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Sample records for monsoon driven godavari

  1. Influence of river discharge on plankton metabolic rates in the tropical monsoon driven Godavari estuary, India

    Digital Repository Service at National Institute of Oceanography (India)

    Sarma, V.V.S.S.; Gupta, S.N.M.; Babu, P.V.R.; Acharyya, T.; Harikrishnachari, N.; Vishnuvardhan, K.; Rao, N.S.; Reddy, N.P.C.; Sarma, V.V.; Sadhuram, Y.; Murty, T.V.R.; Kumar, M.D.

    , J.F., 2000. Persistence of net heterotrophy in lakes during nutrient addition and food web manipulations. Limnology and Oceanography 45, 1718- 1730. Cortner, J.B., Johengen, T.J., and Biddanda, B.A., 2000. Intense winter heterotrophic production...

  2. The response of a natural phytoplankton community from the Godavari River Estuary to increasing CO2 concentration during the pre-monsoon period

    Digital Repository Service at National Institute of Oceanography (India)

    Biswas, H.; Cros, A.; Yadav, K.; Ramana, V.V.; Prasad, V.R.; Acharyya, T.; Babu, P.V.R.

    also been reported by many authors (Trond et al., 2007; Currie and Kalff, 1984). Even diatoms can be out-done by bacteria during such conditions (Brussard and Riegman, 1998). However, the efficiency of bacteria in competing with phytoplankton..., cyanobacteria can easily compete with diatoms in a mixed population under high CO 2 supply and low silicate concentrations. 19 Conclusion: A natural phytoplankton community in the Godavari River Estuary was found to be quite sensitive to increasing CO...

  3. Variability in stratification and flushing times of the Gautami–Godavari estuary, India

    Indian Academy of Sciences (India)

    B Sridevi; V V S S Sarma; T V R Murty; Y Sadhuram; N P C Reddy; K Vijayakumar; N S N Raju; Ch Jawahar Kumar; Y S N Raju; R Luis; M D Kumar; K V S R Prasad

    2015-07-01

    In order to examine the influence of forcing (river flow and tides) and anthropogenic activities (dredging and dam regulation) on stratification, a study was conducted over a period of 19 months (June 2008–December 2009) in the Gautami–Godavari estuary (G–GE) during spring and neap tide periods covering entire spectrum of discharge over a distance of 36 km from the mouth. The bathymetry of the estuary was recently changed due to dredging of ∼20 km of the estuary from the mouth for transportation of barges. This significantly changed the mean depth and salinity of the estuary from its earlier state. The variations in the distribution of salinity in the Godavari estuary are driven by river discharge during wet period (June–November) and tides during dry period (December–May). The weak stratification was observed during high discharge (July–August) and no discharge (January–June) periods associated with dominant fresh water and marine water respectively. The strong stratification was developed associated with decrease in discharge during moderate discharge period (October–December). Relatively stronger stratification was noticed during neap than spring tides. The 15 psu isohaline was observed to have migrated ∼2–3 km more towards upper estuary during spring than neap tide suggesting more salt enters during former than latter period. Total salt content was inversely correlated with river discharge and higher salt of about 400×106 m3 psu was observed during spring than neap tide. Flushing times varied between less than a day and more than a month during peak and no discharge periods respectively with lower times during spring than neap tide. The flushing times are controlled by river discharge during high discharge period, tides during dry period and both (river discharge and tides) under moderate discharge period. This study suggests that modification of discharge, either natural due to weak monsoon, or artificial such as dam constructions and re

  4. Competing Atmospheric and Surface-Driven Impacts of Absorbing Aerosols on the East Asian Summer Monsoon

    Science.gov (United States)

    Persad, G.; Paynter, D.; Ming, Y.; Ramaswamy, V.

    2015-12-01

    Absorbing aerosols, by attenuating shortwave radiation within the atmosphere and reemitting it as longwave radiation, redistribute energy both vertically within the surface-atmosphere column and horizontally between polluted and unpolluted regions. East Asia has the largest concentrations of anthropogenic absorbing aerosols globally, and these, along with the region's scattering aerosols, have both reduced the amount of solar radiation reaching the Earth's surface regionally ("solar dimming") and increased shortwave absorption within the atmosphere, particularly during the peak months of the East Asian Summer Monsoon (EASM). We here analyze how atmospheric absorption and surface solar dimming compete in driving the response of EASM circulation to anthropogenic absorbing aerosols, which dominates, and why—issues of particular importance for predicting how the EASM will respond to projected changes in absorbing and scattering aerosol emissions in the future. We probe these questions in a state-of-the-art general circulation model (GCM) using a combination of realistic and idealized aerosol perturbations that allow us to analyze the relative influence of absorbing aerosols' atmospheric and surface-driven impacts on EASM circulation. In combination, our results make clear that, although absorption-driven dimming has a less detrimental effect on EASM circulation than purely scattering-driven dimming, aerosol absorption is still a net impairment to EASM strength when both its atmospheric and surface effects are considered. Because atmospheric heating is not efficiently conveyed to the surface, the surface dimming and associated cooling from even a pure absorber is sufficient to counteract its atmospheric heating, resulting in a net reduction in EASM strength. These findings elevate the current understanding of the impacts of aerosol absorption on the EASM, improving our ability to diagnose EASM responses to current and future regional changes in aerosol emissions.

  5. Reconstruction of Monsoon Driven South China Sea Surface Ocean Circulation using Coral Δ14C

    Science.gov (United States)

    Goodkin, N.; Bolton, A.; Karnauskas, K. B.; Hughen, K. A.; Griffin, S.; Druffel, E. R. M.

    2016-12-01

    The need to improve our understanding of annual and decadal climate behavior in the South China Sea is increasingly important, as this region includes the largest population density globally but encompasses few climate records. Here we present a record of annually resolved Δ14C from a coral collected off the coast of Nha Trang, Vietnam (12°12'49.90″N, 109°18'17.51″E), that reveals a significant correlation to regional winter sea level pressure (SLP) and sea surface temperature (SST), and extends back more than 400 years. Coral Δ14C during thermonuclear bomb testing indicates the presence of wet-season (summer) upwelling, demonstrated by low Δ14C values for both baseline and peak values relative to other records in the region (Bolton et al., 2016, Radiocarbon). However, annually resolved pre-bomb ∆14C correlates significantly to regional dry-season (winter) SLP and SST, indicating that annual variability is driven by changes to the East Asian Winter Monsoon (EAWM) and subsequent down-welling at this site. Spectral density is focused at 25, 11.8, 7, 4, and 3.2 years per cycle reflecting a range of influences on surface advection variability including the EAWM (D'Arrigo et al., 2005, GRL) and the El Nino Southern Oscillation (ENSO). Spectral power at all of these frequencies decreases following the Little Ice Age ( 1600-1850?) to today, indicating that wind driven surface advection was more variable when hemispheric temperatures were cooler. Decadal variance in the past 100 years is significantly correlated to variance records of the Arctic Oscillation (AO, Thompson and Wallace, 1989, GRL), suggesting that increasing variance in the EAWM may be tied to increasing variance of the AO during the Little Ice Age and vice versa.

  6. Effects of monsoon-driven wave action on coral reefs of Guam and implications for coral recruitment

    Science.gov (United States)

    Becerro, Mikel A.; Bonito, Victor; Paul, Valerie J.

    2006-05-01

    Benthic cyanobacteria can respond rapidly to favorable environmental conditions, overgrow a variety of reef organisms, and dominate benthic marine communities; however, little is known about the dynamics and consequences of such cyanobacterial blooms in coral reef ecosystems. In this study, the benthic community was quantified at the time of coral spawnings in Guam to assess the substrate that coral larvae would encounter when attempting settlement. Transects at 9, 18, and 25-m depths were surveyed at two reef sites before and after heavy wave action driven by westerly monsoon winds. Communities differed significantly between sites and depths, but major changes in benthic community structure were associated with wave action driven by monsoon winds. A shift from cyanobacteria to crustose coralline algae (CCA) accounted for 44% of this change. Coral recruitment on Guam may be limited by substrate availability if cyanobacteria cover large areas of the reef at the time of settlement, and consequently recruitment may in part depend upon wave action from annual monsoon winds and tropical storms which remove cyanobacteria, thereby exposing underlying CCA and other substrate suitable for coral settlement.

  7. Deglaciation in the tropical Indian Ocean driven by interplay between the regional monsoon and global teleconnections

    Digital Repository Service at National Institute of Oceanography (India)

    Saraswat, R.; Lea, D.W.; Nigam, R.; Mackensen, A.; Naik, Dinesh K.

    by prominent weak monsoon intervals (WMI), lasting a few thousand years. Deglacial WMIs are interpreted as the result of cold temperature anomalies generated by sea ice feedbacks in the North Atlantic, most prominently during Heinrich Events. Recent modeling...

  8. Two millennia of Mesoamerican monsoon variability driven by Pacific and Atlantic synergistic forcing

    Science.gov (United States)

    Lachniet, Matthew S.; Asmerom, Yemane; Polyak, Victor; Bernal, Juan Pablo

    2017-01-01

    The drivers of Mesoamerican monsoon variability over the last two millennia remain poorly known because of a lack of precisely-dated and climate-calibrated proxy records. Here, we present a new high resolution (∼2 yrs) and precisely-dated (± 4 yr) wet season hydroclimate reconstruction for the Mesoamerican sector of the North American Monsoon over the past 2250 years based on two aragonite stalagmites from southwestern Mexico which replicate oxygen isotope variations over the 950-1950 CE interval. The reconstruction is quantitatively calibrated to instrumental rainfall variations in the Basin of Mexico. Comparisons to proxy indices of ocean-atmosphere circulation show a synergistic forcing by the North Atlantic and El Niño/Southern Oscillations, whereby monsoon strengthening coincided with a La Niña-like mode and a negative North Atlantic Oscillation, and vice versa for droughts. Our data suggest that weak monsoon intervals are associated with a strong North Atlantic subtropical high pressure system and a weak Intertropical convergence zone in the eastern Pacific Ocean. Population expansions at three major highland Mexico civilization of Teotihuacan, Tula, and Aztec Tenochtitlan were all associated with drought to pluvial transitions, suggesting that urban population growth was favored by increasing freshwater availability in the semi-arid Mexican highlands, and that this hydroclimatic change was controlled by Pacific and Atlantic Ocean forcing.

  9. Can Open Science save us from a solar-driven monsoon?

    Directory of Open Access Journals (Sweden)

    Laken Benjamin A.

    2016-01-01

    Full Text Available Numerous studies have been published claiming strong solar influences on the Earth’s weather and climate, many of which include documented errors and false-positives, yet are still frequently used to substantiate arguments of global warming denial. Recently, Badruddin & Aslam (2015 reported a highly significant relationship between the Indian monsoon and the cosmic ray flux. They found strong and opposing linear trends in the cosmic ray flux during composites of the strongest and weakest monsoons since 1964, and concluded that this relationship is causal. They further speculated that it could apply across the entire tropical and sub-tropical belt and be of global importance. However, examining the original data reveals the cause of this false-positive: an assumption that the data’s underlying distribution was Gaussian. Instead, due to the manner in which the composite samples were constructed, the correlations were biased towards high values. Incorrect or problematic statistical analyses such as this are typical in the field of solar-terrestrial studies, and consequently false-positives are frequently published. However, the widespread adoption of Open Science approaches, placing an emphasis on reproducible open-source analyses as demonstrated in this work, could remedy the situation.

  10. Establishment and adjustment of monsoon-driven circulation in the South China Sea

    Institute of Scientific and Technical Information of China (English)

    王东晓; 王卫强; 施平; 郭佩芳; 甘子钧

    2003-01-01

    The mechanisms of establishment and adjustment of the basin-scale circulation in the South China Sea (SCS) during the monsoon-forced spin-up are investigated using a high resolution circulation model in this paper. The process, in which the upper layer in the SCS evolved from the motionless state to the one when the basin-scale circulation initially established, was described, and the participation of various Kelvin and Rossby waves and their traveling time scales in different stages was revealed. It shows that the coastal trapped Kelvin waves and the westward propagating Rossby waves play important roles in the adjustment of the basin-scale circulation. Furthermore, the characteristic timescale of establishment for the basin-scale circulation in the upper layer of the SCS was obtained.

  11. Seismic characterization of hydrates in faulted, fine-grained sediments of Krishna-Godavari Basin: Full waveform inversion

    Digital Repository Service at National Institute of Oceanography (India)

    Jaiswal, P.; Dewangan, P.; Ramprasad, T.; Zelt, C.A.

    ; full waveform inversion; P-wave velocity; P-wave attenuation 1. INTRODUCTION Hydrates can play a potentially significant role in climate change (Gu et al., 2011), seafloor stability (Brown et al., 2006), and energy security (Boswell and Collett, 2011... distribution within fine-grained, clay-dominated, and faulted sediments of the Krishna-Godavari (KG) Basin located offshore of eastern continental margin of India (Figure 1). We apply FWI in the frequency domain. The domain choice is driven by a) efficiency...

  12. Analysis and Mapping of Flood Line and Flood Zones within the Godavari River in Nasik Municipal Corporation

    Science.gov (United States)

    Thakre, Deepak

    2010-05-01

    Analysis and Mapping of Flood Line within the Godavari River in Nasik(Municipal Corporation Area) Dr.Deepak N.Thakre Lecturer in Geography L.V.H.College, Nasik-3, Maharashtra, India A flood is an overflow or accumulation of an expanse of water that submerges land when the discharge of a river can not be accommodated within the margins of its normal channel so that water spreads over adjoining area and creates havoc. Problem: Since last few years there has been a sudden increase in rainfall,quite intense during a certain period in monsoon,as a result of which the discharge in river Godavari increases and creates problems in low lying areas on the banks of river Godavari like: submergence of houses,major loss of lives,management failure(due to unexpected dimension of floods)and the disruption of normal life. This paper attempts to analyse and draw an averege flood zone and sudden flood zone on the basis of : 1) Actual field work and survey with the help of Dumpy level and GPS 2) Field interviews of affected people 3) Data available from Meteorological and Irrigation department Among several districts that have flourished in the soils of Indian subcontinent the name of Nashik has drawn the attention of people all over the world. Geographical location of Nashik is 20° 01' to 20° 02' North and 73° 30' to 73° 50'East. Nashik city is situated on the banks of river Godavari and tributaries namely Nasardi, Waghadi, Darna and Walvadi.The total area of Nasik is 264.23 Sq.km (102 Sq.mt) and height from M.S.L is 3284 feet (1001 Mt). River Godavari originates in Western mountain range and flows towards East up to Bay of Bengal. On the upstream of Nasik city dams like Gangapur, Darna, Alandi, Kasyapi and Gautami-Godavari are constructed on river Godavari and its tributaries. Gangapur dam is the nearest storage dam constructed 15km away from Nasik city at source area in the year 1965. Due to moderation of floods and construction of dam there is encroachment in low lying areas

  13. Wind-driven coastal upwelling along the western boundary of the Bay of Bengal during the southwest monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Shetye, S.R.; Shenoi, S.S.C.; Gouveia, A.D.; Michael, G.S.; Sundar, D.; Nampoothiri, G.

    monsoon. Occur- rence of shelf waves can have important implications for upwelling along the coast. In their presence, the upwelling intensity at any location is determined not only by the local longshore wind stress, but also by the history of shelf... of Bengal. In: The encyclopedia of oceanography, R. W. FAXRaR~D~E. editor, Dowden, Hutchinson and Ross, Stroudburg, 1021 pp. LEGECKIS R. (1987) Satellite observations of a western boundary current in the Bay of Bengal. Journal of Geophysical Research, 92...

  14. Water quality assessment of Gautami — Godavari mangrove estuarine ecosystem of Andhra Pradesh, India during September 2001

    Indian Academy of Sciences (India)

    S C Tripathy; A K Ray; S Patra; V V Sarma

    2005-04-01

    Some chemical and biological parameters were analysed at sixteen stations in the mangrove ecosystem, of the neighbouring Gautami-Godavari (GG) river estuary and Kakinada (KKD) bay to understand the present status of water quality and the impact of external terrigenous inputs during southwest (SW) monsoon in the study areas. High concentrations of nutrients in the mangrove ecosystem compared to the bay and estuarine ecosystems reveal the importance of this zone as a source of nutrients to the adjacent coastal ecosystems. Low Si :N:P (29 : 4 : 1) ratios in these ecosystems are due to the enrichment of these nutrients through external anthropogenic inputs even after the utilization by phytoplankton in the biological cycle. The mean Chl /Chl and Chl /Chl ratios and high phaeopigments (Pp) concentrations compared to Chl and high ratios of Chl /Pp suggests the possibility of the potential growth of phytoplankton populations in lower light intensity and low turbulent areas of these mangrove ecosystems.

  15. Both temperature fluctuations and East Asian monsoons have driven plant diversification in the karst ecosystems from southern China.

    Science.gov (United States)

    Kong, Hanghui; Condamine, Fabien L; Harris, A J; Chen, Junlin; Pan, Bo; Möller, Michael; Hoang, Van Sam; Kang, Ming

    2017-09-28

    Karst ecosystems in southern China are species-rich and have high levels of endemism, yet little is known regarding the evolutionary processes responsible for the origin and diversification of karst biodiversity. The genus Primulina (Gesneriaceae) comprises ca. 170 species endemic to southern China with high levels of ecological (edaphic) specialization, providing an exceptional model to study the plant diversification in karsts. We used molecular data from nine chloroplast and 11 nuclear regions and macroevolutionary analyses to assess the origin and cause of species diversification due to paleoenvironmental changes and edaphic specialization in Primulina. We found that speciation was positively associated with changes in past temperatures and East Asian monsoons through the evolutionary history of Primulina. Climatic change around the mid-Miocene triggered an early burst followed by a slowdown of diversification rate towards the present with the climate cooling. We detected different speciation rates among edaphic types, and transitions among soil types were infrequently and did not impact the overall speciation rate. Our findings suggest that both global temperature changes and East Asian monsoons have played crucial roles in floristic diversification within the karst ecosystems in southern China, such that speciation was higher when climate was warmer and wetter. This is the first study to directly demonstrate that past monsoon activity is positively correlated with speciation rate in East Asia. This case study could motivate further investigations to assess the impacts of past environmental changes on the origin and diversification of biodiversity in global karst ecosystems, most of which are under threat. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  16. Spatiotemporal trends in the southwest monsoon wind-driven upwelling in the southwestern part of the South China Sea.

    Science.gov (United States)

    Kok, Poh Heng; Mohd Akhir, Mohd Fadzil; Tangang, Fredolin; Husain, Mohd Lokman

    2017-01-01

    This study analyzes two wind-induced upwelling mechanisms, namely, Ekman transport and Ekman pumping that occur during the southwest monsoon. The results suggest that the coastline of the east coast of Peninsular Malaysia (ECPM) is affected by upwelling with spatiotemporal variations. Characterization of upwelling by using wind-induced upwelling indexes (UIW) indicate the existence of favorable upwelling conditions from May to September. Upwelling intensity increased in May and peaked in August before declining in September, decreasing intensity from the southern tip towards the northern tip along the coastline of the ECPM. The existence of upwelling along the ECPM has resulted in an important difference between the SSTs of the inshore and the oceanic regions. Nonetheless, the use of the SST gradient between the inshore and the oceanic SSTs to characterize upwelling (UISST) was found to be unsuitable because the SST along the ECPM was affected by water advection from the Java Sea and incessant changes in the SST. In order to indicate the major contributor of wind-induced upwelling along the ECPM in terms of the spatiotemporal scale, a comparison between Ekman transport and Ekman pumping was drawn by integrating Ekman pumping with respect to the distance where the positive wind stress curl existed. The estimation of Ekman transport and Ekman pumping indicated that Ekman pumping played a major role in contributing towards upwelling in any particular month during the southwest monsoon along the entire coastline of the ECPM as compared to Ekman transport, which contributed towards more than half of the total upwelling transport. By dividing the ECPM into three coastal sections, we observed that Ekman pumping was relatively predominant in the middle and northern coasts, whereas both Ekman transport and Ekman pumping were equally prevalent in the southern coast.

  17. Spatiotemporal trends in the southwest monsoon wind-driven upwelling in the southwestern part of the South China Sea

    Science.gov (United States)

    Mohd Akhir, Mohd Fadzil; Tangang, Fredolin; Husain, Mohd Lokman

    2017-01-01

    This study analyzes two wind-induced upwelling mechanisms, namely, Ekman transport and Ekman pumping that occur during the southwest monsoon. The results suggest that the coastline of the east coast of Peninsular Malaysia (ECPM) is affected by upwelling with spatiotemporal variations. Characterization of upwelling by using wind-induced upwelling indexes (UIW) indicate the existence of favorable upwelling conditions from May to September. Upwelling intensity increased in May and peaked in August before declining in September, decreasing intensity from the southern tip towards the northern tip along the coastline of the ECPM. The existence of upwelling along the ECPM has resulted in an important difference between the SSTs of the inshore and the oceanic regions. Nonetheless, the use of the SST gradient between the inshore and the oceanic SSTs to characterize upwelling (UISST) was found to be unsuitable because the SST along the ECPM was affected by water advection from the Java Sea and incessant changes in the SST. In order to indicate the major contributor of wind-induced upwelling along the ECPM in terms of the spatiotemporal scale, a comparison between Ekman transport and Ekman pumping was drawn by integrating Ekman pumping with respect to the distance where the positive wind stress curl existed. The estimation of Ekman transport and Ekman pumping indicated that Ekman pumping played a major role in contributing towards upwelling in any particular month during the southwest monsoon along the entire coastline of the ECPM as compared to Ekman transport, which contributed towards more than half of the total upwelling transport. By dividing the ECPM into three coastal sections, we observed that Ekman pumping was relatively predominant in the middle and northern coasts, whereas both Ekman transport and Ekman pumping were equally prevalent in the southern coast. PMID:28187215

  18. Predicting Monsoonal-Driven Stream Discharge and Sediment Yield in Himalaya Mountain Basins with Changing Climate and Deforestation

    Science.gov (United States)

    Neupane, R. P.; White, J. D.

    2014-12-01

    Short and long term effects of site water availability impacts the spectrum of management outcomes including landslide risk, hydropower generation, and sustainable agriculture in mountain systems heavily influenced by climate and land use changes. Climate change and land use may predominantly affect the hydrologic cycle of mountain basins as soil precipitation interception is affected by land cover. Using the Soil and Water Assessment Tool, we estimated stream discharge and sediment yield associated with climate and land use changes for two Himalaya basins located at eastern and western margins of Nepal that included drainages of the Tamor and Seti Rivers. Future climate change was modeled using average output of temperature and precipitation changes derived from Special Report on Emission Scenarios (B1, A1B & A2) of 16 global circulation models for 2080 as meteorological inputs into SWAT. Land use change was modeled spatially and included 1) deforestation, 2) expansion of agricultural land, and 3) increased human settlement that were produced by considering current land use with projected changes associated with viability of elevation and slope characteristics of the basins capable of supporting different land use types. We found higher annual stream discharge in all GCM-derived scenarios compared to the baseline with maximum increases of 13 and 8% in SRES-A2 and SRES-A1B for the Tamor and Seti basins, respectively. With 7% of original forest land removed, sediment yield for Tamor basin was estimated to be 65% higher, but increased to 124% for the SRES-B1 scenario. For the Seti basin, 4% deforestation yielded 33% more sediment for the SRES-A1B scenario. Our results indicated that combined effects of future, intensified monsoon rainfall with deforestation lead to dramatic potential for increased stream discharge and sediment yield as rainfall on steep slopes with thin exposed soils increases surface runoff and soil erosion in the Himalayas. This effect appears to

  19. Studies on heavy metal contamination in Godavari river basin

    Science.gov (United States)

    Hussain, Jakir; Husain, Ikbal; Arif, Mohammed; Gupta, Nidhi

    2017-09-01

    Surface water samples from Godavari river basin was analyzed quantitatively for the concentration of eight heavy metals such as arsenic, cadmium, chromium, copper, iron, lead, nickel and zinc using atomic absorption spectrophotometer. The analyzed data revealed that iron and zinc metals were found to be the most abundant metals in the river Godavari and its tributaries. Iron (Fe) recorded the highest, while cadmium (Cd) had the least concentration. Arsenic, cadmium, chromium, iron and zinc metals are within the acceptable limit of BIS (Bureau of Indian Standards (BIS) 1050 (2012) Specification for drinking water, pp 1-5). The analysis of Godavari river and its tributary's water samples reveals that the water is contaminated at selected points which are not suitable for drinking. Nickel and Copper concentration is above acceptable limit and other metal concentration is within the acceptable limit. Comprehensive study of the results reveals that out of 18 water quality stations monitored, water samples collected at 7 water quality stations are found to be within the permissible limit for all purposes. While Rajegaon, Tekra, Nandgaon, P. G. Bridge, Bhatpalli, Kumhari, Pauni, Hivra, Ashti, Bamini, and Jagda stations were beyond the desirable limit due to presence of copper and nickel metals. The contents of copper metal ions were higher at some water quality stations on Wunna river (Nandgaon); Wardha river (Hivra) and Wainganga river (Kumhari, Pauni, Ashti) during Feb. 2012, while nickel concentration during Feb. 2012, June 2012, March 2013 and Aug. 2013 at some water quality stations on rivers Bagh, Indravati, Pranhita, Wunna, Penganga, Peddavagu, Wainganga and Wardha. It can be concluded that rapid population growth and industrialization have brought about resource degradation and a decline in environmental quality.

  20. Time-dependent stratification in the Gauthami-Godavari Estuary

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, T.V.N.

    dur- ing July to October, the flood months of the year. Results and Discussion SALINITY The tidally averaged salinity at Stations 1–3 in the winter and the dry seasons (Fig. 3) showed that the water in the upstream parts of the Gauthami- Godavari... quickly on the flood tide and minimum stratification of 0.3, 5.0, and 5.7 psu during the winter and 0.2, 5.9, and 8.2 psu during the dry season occur at Stations 1–3, respectively, and maximum surface salinity of 28.0, 24.5, and 19.9 psu during winter...

  1. Spectra of currents and temperature off Godavari (east coast of India)

    Digital Repository Service at National Institute of Oceanography (India)

    Sarma, M.S.S; Rao, L.V.G.

    Time series data of currents and temperature obtained from a mooring of current meters off Godavari (East Coast of India) during September 1980 are analysed to study the space scales of semidiurnal and internal oscillations in the range of buoyancy...

  2. Submarine groundwater discharge and nutrient addition to the coastal zone of the Godavari estuary

    Digital Repository Service at National Institute of Oceanography (India)

    Rengarajan, R.; Sarma, V.V.S.S.

    Submarine groundwater discharge (SGD) represents a significant pathway of materials between land and sea, especially as it supplies nutrients, carbon and trace metals to coastal waters. To estimate SGD fluxes to the Godavari estuary, India, we used...

  3. Morphological changes at Godavari delta region due to waves, currents and the associated physical processes

    Digital Repository Service at National Institute of Oceanography (India)

    Sastry, J.S.; Vethamony, P.; Swamy, G.N.

    the speed of 200 cm/sec. The morphological changes due to the effect of river discharge during various seasons and the development of Godavari sand spit off Kakinada and its influence to delta modification are detailed....

  4. Monsoon Country

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Heavy rains have battered areas of south China this year,causing death and destruction For most areas south of the Yangtze River,this year’s monsoon season has come early, with heavy rains triggering floods,damaging crops,threatening reservoirs and causing deaths.

  5. High CO2 emissions from the tropical Godavari estuary (India) associated with monsoon river discharges

    Digital Repository Service at National Institute of Oceanography (India)

    Sarma, V.V; Kumar, N.A.; Prasad, V; Venkataramana, V; Appalanaidu, S.; Sridevi, B.; Kumar, B.S.K.; Bharati, M.D.; Subbaiah, C.V; Acharyya, T.; Rao, G.D.; Viswanadham, R.; Gawade, L; Manjary, D.T.; Kumar, P.P.; Rajeev, K.; Reddy, N.P.C.; Sarma, V.V.; Kumar, M.D.; Sadhuram, Y.; Murty, T.V.R.

    . Appalanaidu, B. Sridevi, B.S.K. Kumar, M.D. Bharati, Ch.V. Subbaiah, T. Acharya, G.D. Rao, R. Viswanadham, L. Gawade, D.T. Manjary, P. P. Kumar, K. Rajeev, N.P.C. Reddy, V.V. Sarma, M.D. Kumar, Y. Sadhuram and T.V.R. Murty National Institute...-67. Borges, A.V., B. Delille and M. Frankignoulle (2005), Budgeting sinks and sources of CO2 in the coastal ocean: Diversity of ecosystems counts. Geophysical Research Letters, 32, No. L14601. Bouillon, S., M. Frankignoulle, F. Dehairs, F. et al.(2003...

  6. Structure of Charnockitic basement in a part of the Krishna–Godavari basin, Andhra Pradesh

    Indian Academy of Sciences (India)

    I V Radhakrishna Murthy; S Bangaru Babu

    2006-08-01

    A regional magnetic survey was carried out over an area of 8000 km2 in Godavari districts of Andhra Pradesh,India,which is covered by the rocks of Eastern Ghat Mobile Belt (EGMB) viz., the Khondalitic series and Charnockites in the northern half and Permian to Mesozoic and Cenozoic sediments in the southern half,and forms a part of the Krishna –Godavari (K –G)basin. The survey brought out a strong NE –SW trending anomaly in the area covered by the rocks of Eastern Ghat Mobile Belt (EGMB),and a mild ENE –WSW trending anomaly in the area covered by the sediments of the Krishna –Godavari (K –G)basin.The NE –SW trending anomaly in the northern half could be attributed to the exposed/near surface Charnockite basement that has come closer to the surface as a result of Eastern Ghat Mobile Belt (EGMB)tectonics.Explanation of the mild ENE –WSW trending anomaly over the sediments of the Krishna –Godavari (K –G)basin required a faulted magnetic basement at depth downthrown towards the south.It is therefore concluded that the Charnockitic basement together with the Khondalite group of rocks which are folded and faulted during the different phases of tectonics of Eastern Ghat Mobile Belt (EGMB) extend into the Krishna –Godavari (K –G)basin and further,were involved in faulting during the phases of formation and sedimentation in the Krishna –Godavari (K –G)basin.

  7. Transport and potential vorticity in the Bay of Bengal during the southwest monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Murty, V.S.N.; Murty, C.S.; Sarma, Y.V.B.; Rao, D.P.; Sastry, J.S.; Rao, G.R.L.

    In the Bay of Bengal, the water transport and potential vorticity (PV) during the southwest monsoon are examined through the prevailing thermohaline and wind-driven circulation. The Indian Monsoon Current (IMC) and the north flowing Eastern Boundary...

  8. A Marchantialean thallus from the Lower Gondwana Sequence of Godavari basin, Andhra Pradesh

    Energy Technology Data Exchange (ETDEWEB)

    Sarate, O.S.; Budhraja, N. [Birbal Sahni Institute of Paleobotany, Lucknow (India)

    2007-07-15

    The present paper deals with the critical observation of a thallus section recorded in one of the samples prepared for the coal petrographic study (Pellet No. 3). This sample represents a coal band lying above the 'Queen seam' from Koyagudem area of the Godavari valley coalfield, Andhra Pradesh. The shape of this specimen in transverse section and its cellular organization very closely resemble the anatomical features of extant thalli of the bryophytic (liverwort) family Rebouliaceae, a big group of Marchantiales (Hepaticopsida). A thallus with cellular details assignable to Hepaticae is recorded from the Lower Gondwana Sequence of Godavari valley coalfield.

  9. Significance of riverine carbon transport: A case study of a large tropical river, Godavari (India)

    Institute of Scientific and Technical Information of China (English)

    M.; M.; Sarin; A.; K.; Sudheer; K.; Balakrishna

    2002-01-01

    Although riverine carbon fluxes are a minor component of the global carbon cycle, the transfer of organic carbon from land to ocean represents a flux of potential carbon storage, irreversible over 103 to 104 a. Future carbon transfers through river basins are expected to accelerate, with respect to both sources and sinks, because of the large-scale human driven land-use and land-cover changes. Thus, the increased amounts of carbon transported to and sequestered in marine sediments (through fertilization by river-borne inorganic nutrients) may be an important net sink for anthropogenic CO2. Particularly, the humid tropics of South Asia are regions very sensitive to this lateral C transport because of high precipitation and high rates of land use and cover change. In this paper we report on the role of upland tributaries in the transport processes influencing the lateral carbon and nitrogen fluxes of the Godavari, a large tropical river of India. By far, dissolved inorganic carbon (DIC) is the dominant form of carbontransport in the river basin. It constitutes as much as 75% to the total carbonload. Particulate and dissolved organic carbon (POC and DOC) fluxes account for21% and 4%, respectively. In the upper basin, DOC fluxes exceed that of POC dueto large-scale anthropogenic activities. In contrast, tributaries in the central basin are characterized by comparable fluxes of POC and DOC. However, downriver POC export is 35% less than the import from upriver and tributaries due to theentrainment of sediments in river channels and dam sites. We argue that for highly disturbed watersheds in tropical regions, downstream transport of sediments and carbon requires long-term sampling programmes.

  10. Occurrence of heavy rainfall around the confluence line in monsoon disturbances and its importance in causing floods

    Indian Academy of Sciences (India)

    G Nageswara Rao

    2001-03-01

    It is well known that heavy rainfall occurs in the southwestern sector of the monsoon depressions due to strong convergence in that sector. By examining the rainfall distribution associated with the monsoon disturbances (lows and depressions) in one of the central Indian river basins, `Godavari', the author found that when the disturbance-centre is away from the basin, heavy rainfall may also occur in the basin area close to the confluence line and cause severe floods in the river. The confluence line is the zone of convergence between the northeasterlies to the west of the disturbance centre and the monsoon westerlies. This study further reveals the importance of the position and movement of the confluence line with respect to the basin, on which the intensity and the raising period of the resulting flood depend.

  11. Tidally-modulated high frequency internal waves in Gautami-Godavari estuary, East coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Sridevi, B.; Murty, T.V.R.; Sadhuram, Y.; Sarma, V.V.S.S.; Murty, V.S.N.; Prasad, K.V.S.R.

    Time series temperature and salinity (at 1 hour interval) and currents data (10 min interval) at surface (3 m) and bottom (14 m), collected in the Gautami-Godavari estuary during 25-27 September 2008 were utilized to document the characteristics...

  12. Evolving provenance in the Proterozoic Pranhita-Godavari Basin, India

    Institute of Scientific and Technical Information of China (English)

    Udeni Amarasinghe; Asru Chaudhuri; Alan S Collins; Gautam Deb; Sarbani Patranabis-Deb

    2015-01-01

    The Pranhita-Godavari Basin in central eastern India is one of the Proterozoic“Pur?ana”basins of cratonic India. New geochronology demonstrates that it has a vast depositional history of repeated basin reac-tivation from the Palaeoproterozoic to the Mesozoic. U-Pb laser ablation inductively coupled plasma mass spectrometry dating of detrital zircons from two samples of the Somanpalli Groupda member of the oldest sedimentary cycle in the valleydconstrains its depositional age to w1620 Ma and demon-strates a tripartite age provenance with peaks at w3500 Ma, w2480 Ma and w1620 Ma, with minor age peaks in the Eoarchaean (w3.8 Ga) and at w2750 Ma. These ages are consistent with palaeocurrent data suggesting a southerly source from the Krishna Province and Enderby Land in East Antarctica. The similarity in the maximum depositional age with previously published authigenic glauconite ages sug-gest that the origin of the Pranhita-Godvari Graben originated as a rift that formed at a high angle to the coeval evolving late Meosproterozoic Krishna Province as Enderby Land collided with the Dharwar craton of India. In contrast, detrital zircons from the Cycle III Sullavai Group red sandstones yielded a maximum depositional age of 970 ? 20 Ma and had age peaks of w2550 Ma, w1600 Ma and then a number of Mesoproterozoic detrital zircons terminating in three analyses at w970 Ma. The provenance of these is again consistent with a southerly source from the Eastern Ghats Orogen and Antarctica. Later cycles of deposition include the overlying Albaka/Usur Formations and finally the late Palaeozoic to Mesozoic Gondwana Supergroup.

  13. Evolving provenance in the Proterozoic Pranhita-Godavari Basin, India

    Directory of Open Access Journals (Sweden)

    Udeni Amarasinghe

    2015-05-01

    Full Text Available The Pranhita-Godavari Basin in central eastern India is one of the Proterozoic “Purāna” basins of cratonic India. New geochronology demonstrates that it has a vast depositional history of repeated basin reactivation from the Palaeoproterozoic to the Mesozoic. U-Pb laser ablation inductively coupled plasma mass spectrometry dating of detrital zircons from two samples of the Somanpalli Group—a member of the oldest sedimentary cycle in the valley—constrains its depositional age to ∼1620 Ma and demonstrates a tripartite age provenance with peaks at ∼3500 Ma, ∼2480 Ma and ∼1620 Ma, with minor age peaks in the Eoarchaean (∼3.8 Ga and at ∼2750 Ma. These ages are consistent with palaeocurrent data suggesting a southerly source from the Krishna Province and Enderby Land in East Antarctica. The similarity in the maximum depositional age with previously published authigenic glauconite ages suggest that the origin of the Pranhita-Godvari Graben originated as a rift that formed at a high angle to the coeval evolving late Meosproterozoic Krishna Province as Enderby Land collided with the Dharwar craton of India. In contrast, detrital zircons from the Cycle III Sullavai Group red sandstones yielded a maximum depositional age of 970 ± 20 Ma and had age peaks of ∼2550 Ma, ∼1600 Ma and then a number of Mesoproterozoic detrital zircons terminating in three analyses at ∼970 Ma. The provenance of these is again consistent with a southerly source from the Eastern Ghats Orogen and Antarctica. Later cycles of deposition include the overlying Albaka/Usur Formations and finally the late Palaeozoic to Mesozoic Gondwana Supergroup.

  14. Occurrence of gas hydrates along the continental margins of India, particularly the Krishna-Godavari offshore basin

    Digital Repository Service at National Institute of Oceanography (India)

    Ramana, M.V.; Ramprasad, T.; KameshRaju, K.A.; Desa, M.

    carried out in the Krishna-Godavari offshore area along the eastern continental margin of India, which is known for its hydrocarbon potential. Processed multibeam data provided a high-resolution seafloor mosaic with a fine scale geomorphology. Deep tow...

  15. Water quality assessment of Gautami-Godavari mangrove estuarine ecosystem of Andhra Pradesh, India during September 2001

    Digital Repository Service at National Institute of Oceanography (India)

    Tripathy, S.C.; Ray, A.K.; Patra, S.; Sarma, V.V.

    Some chemical and biological parameters were analysed at sixteen stations in the mangrove ecosystem, of the neighbouring Gautami-Godavari (GG) river estuary and Kakinada (KKD) bay to understand the present status of water quality and the impact...

  16. Indian monsoon variations during three contrasting climatic periods: the Holocene, Heinrich Stadial 2 and the last interglacial-glacial transition

    Science.gov (United States)

    Zorzi, Coralie; Fernanda Sanchez Goñi, Maria; Anupama, Krishnamurthy; Prasad, Srinivasan; Hanquiez, Vincent; Johnson, Joel; Giosan, Liviu

    2016-04-01

    In contrast to the East Asian and African monsoons the Indian monsoon is still poorly documented throughout the last climatic cycle (last 135,000 years). Pollen analysis from two marine sediment cores (NGHP-01-16A and NGHP-01-19B) collected from the offshore Godavari and Mahanadi basins, both located in the Core Monsoon Zone (CMZ) reveals changes in Indian summer monsoon variability and intensity during three contrasting climatic periods: the Holocene, the Heinrich Stadial (HS) 2 and the Marine Isotopic Stage (MIS) 5/4 during the ice sheet growth transition. During the first part of the Holocene between 11,300 and 4,200 cal years BP, characterized by high insolation (minimum precession, maximum obliquity), the maximum extension of the coastal forest and mangrove reflects high monsoon rainfall. This climatic regime contrasts with that of the second phase of the Holocene, from 4,200 cal years BP to the present, marked by the development of drier vegetation in a context of low insolation (maximum precession, minimum obliquity). The historical period in India is characterized by an alternation of strong and weak monsoon centennial phases that may reflect the Medieval Climate Anomaly and the Little Ice Age, respectively. During the HS 2, a period of low insolation and extensive iceberg discharge in the North Atlantic Ocean, vegetation was dominated by grassland and dry flora indicating pronounced aridity as the result of a weak Indian summer monsoon. The MIS 5/4 glaciation, also associated with low insolation but moderate freshwater fluxes, was characterized by a weaker reduction of the Indian summer monsoon and a decrease of seasonal contrast as recorded by the expansion of dry vegetation and the development of Artemisia, respectively. Our results support model predictions suggesting that insolation changes control the long term trend of the Indian monsoon precipitation, but its millennial scale variability and intensity are instead modulated by atmospheric

  17. Model simulation of tide-induced currents in Gauthami-Godavari estuary

    Digital Repository Service at National Institute of Oceanography (India)

    Sridevi, B.; Murty, T.V.R.; Sadhuram, Y.; Sarma, V.V.S.S.; Naidu, V.S.; Prasad, K.V.S.R.

    controlled by Low Dam at Dowleiswaram, where it bifurcates into two channels as Vasishta and Gauthami Godavari estuary (Figure 1)18,19. Discharge was maximal in August, and virtually no or negligible discharge between January and May19. Mixing... to a wide spec- trum of circulation patterns and estuarine mixing. Virtually no discharge during the dry season made the estuary turn into well-mixed type and circulation is domi- nated by tides. Several investigators studied the seasonal variations...

  18. Monsoons, history of

    Digital Repository Service at National Institute of Oceanography (India)

    Niitsuma, N.; Naidu, P.D.

    The evolution of the Asian monsoon started at around 9.5 Ma, in response to the uplift of the Himalayas. The monsoonal intensity reached its maximum at around 5 Ma, and from that time the associated easterly trade winds caused intense upwelling...

  19. Asian monsoons in a late Eocene greenhouse world

    Science.gov (United States)

    Licht, A.; van Cappelle, M.; Abels, H. A.; Ladant, J.-B.; Trabucho-Alexandre, J.; France-Lanord, C.; Donnadieu, Y.; Vandenberghe, J.; Rigaudier, T.; Lécuyer, C.; Terry, D., Jr.; Adriaens, R.; Boura, A.; Guo, Z.; Soe, Aung Naing; Quade, J.; Dupont-Nivet, G.; Jaeger, J.-J.

    2014-09-01

    The strong present-day Asian monsoons are thought to have originated between 25 and 22 million years (Myr) ago, driven by Tibetan-Himalayan uplift. However, the existence of older Asian monsoons and their response to enhanced greenhouse conditions such as those in the Eocene period (55-34 Myr ago) are unknown because of the paucity of well-dated records. Here we show late Eocene climate records revealing marked monsoon-like patterns in rainfall and wind south and north of the Tibetan-Himalayan orogen. This is indicated by low oxygen isotope values with strong seasonality in gastropod shells and mammal teeth from Myanmar, and by aeolian dust deposition in northwest China. Our climate simulations support modern-like Eocene monsoonal rainfall and show that a reinforced hydrological cycle responding to enhanced greenhouse conditions counterbalanced the negative effect of lower Tibetan relief on precipitation. These strong monsoons later weakened with the global shift to icehouse conditions 34 Myr ago.

  20. Gas-hydrates in Krishna-Godavari and Mahanadi basins: New data

    Digital Repository Service at National Institute of Oceanography (India)

    Sain, K.; Ojha, M.; Satyavani, N.; Ramadass, G.A.; Ramprasad, T.; Das, S.K.; Gupta, H.

    -7622/2012-79-6-553/$ 1.00 © GEOL. SOC. INDIA JOURNAL GEOLOGICAL SOCIETY OF INDIA Vol.79, June 2012, pp.553-556 Gas-hydrates in Krishna-Godavari and Mahanadi Basins: New Data KALACHAND SAIN 1 , MAHESWAR OJHA 1 , NITTALA SATYAVANI 1 , G.A. RAMADASS 2 , T. RAMPRASAD 3 , S... Paula, Goa - 403 004 4 Ministry of Earth Sciences, Prithvi Bhavan, Lodhi Road, New Delhi - 110 003 Email: kalachandsain@yahoo.com than 1500 times of India’s present natural gas reserve, and it is envisaged that 10% recovery from this huge cache of energy...

  1. Measuring the monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaswamy, V.; Nair, R.R.

    of the monsoons, there are also fluctuations arising from human activities. Most scientists believe that large-scale deforestation and burning of fossil fuels will alter global climatic patterns significantly. For the sake of those people whose lives...

  2. Soil moisture initialization effects in the Indian monsoon system

    OpenAIRE

    Asharaf, S.; A. Dobler; Ahrens, B.

    2011-01-01

    Towards the goal to understand the role of land-surface processes over the Indian sub-continent, a series of soil-moisture sensitivity simulations have been performed using a non-hydrostatic regional climate model COSMO-CLM. The experiments were driven by the lateral boundary conditions provided by the ERA-Interim (ECMWF) reanalysis. The simulation results show that the pre-monsoonal soil moisture has a significant influence on the monsoonal precipitation. Both, positive and negative soil-moi...

  3. Assessment of potential shale gas resources of the Bombay, Cauvery, and Krishna-Godavari Provinces, India, 2011

    Science.gov (United States)

    ,

    2012-01-01

    Using a performance-based geologic assessment methodology, the U.S. Geological Survey estimated a technically recoverable mean volume of 6.1 trillion cubic feet of potential shale gas in the Bombay, Cauvery, and Krishna-Godavari Provinces of India.

  4. Magnetic anomalies of offshore Krishna-Godavari Basin, eastern continental margin of India

    Indian Academy of Sciences (India)

    K V Swamy; I V Radhakrishna Murthy; K S Krishna; K S R Murthy; A S Subrahmanyam; M M Malleswara Rao

    2009-08-01

    The marine magnetic data acquired from offshore Krishna–Godavari (K–G) basin, eastern continental margin of India (ECMI), brought out a prominent NE–SW trending feature, which could be explained by a buried structural high formed by volcanic activity. The magnetic anomaly feature is also associated with a distinct negative gravity anomaly similar to the one associated with 85°E Ridge. The gravity low could be attributed to a flexure at the Moho boundary, which could in turn be filled with the volcanic material. Inversion of the magnetic and gravity anomalies was also carried out to establish the similarity of anomalies of the two geological features (structural high on the margin and the 85°E Ridge) and their interpretations. In both cases, the magnetic anomalies were caused dominantly by the magnetization contrast between the volcanic material and the surrounding oceanic crust, whereas the low gravity anomalies are by the flexures of the order of 3–4 km at Moho boundary beneath them. The analysis suggests that both structural high present in offshore Krishna–Godavari basin and the 85°E Ridge have been emplaced on relatively older oceanic crust by a common volcanic process, but at discrete times, and that several of the gravity lows in the Bay of Bengal can be attributed to flexures on the Moho, each created due to the load of volcanic material.

  5. Seasonal Abundance of Micro Algae in Pandi Backwaters of Godavari Estuary, Andhra Pradesh, India

    Directory of Open Access Journals (Sweden)

    Geddada Mohan NARASIMHA RAO

    2010-09-01

    Full Text Available Gautami branch of Godavari River is a typical positive estuary and is in tidal communication with the open sea upto a point near Kapileswarapuram. This branch flows southwest and opens into Bay of Bengal at two places, namely Bhiravapalem and Kothapalem. The Gautami branch of Godavari is also connected to Pandi backwaters by a channel known as Pedderu, which starts at Kothapalem, Balusutippa area and enters Pandi back water system. Two stations were selected for collection of data. Hydrographical data were collected for one year from July 2006 to 2007 and the data on distribution of phytoplankton was studied in three seasons during 2006-2007. Hydrographical features of the two stations showed that lower values were recorded during October to February months, while higher values were reported from the month of March to September. A total 57 species of phytoplankton were identified from the two study sites of the Pandi backwaters Composition of phytoplankton varied seasonally in relation to salinity fluctuations and showed that two peak periods, one in June-July and another in between December and March. Present study indicates that diatoms are the dominant group followed by the Chlorophyceae and others. This study will aid the baseline data for aqua-culturists in nearby regions.

  6. Recent change of the global monsoon precipitation (1979-2008)

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Bin [University of Hawaii at Manoa, Department of Meteorology, Honolulu, HI (United States); University of Hawaii at Manoa, International Pacific Research Center, Honolulu, HI (United States); Liu, Jian [Chinese Academy of Sciences, State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Nanjing (China); Kim, Hyung-Jin [Japan Agency for Marine-Earth Science and Technology, Research Institute for Global Change, Yokohama, Kanagawa (Japan); Webster, Peter J. [Georgia Institute of Technology, School of Earth and Atmospheric Sciences, Atlanta, GA (United States); Yim, So-Young [University of Hawaii at Manoa, International Pacific Research Center, Honolulu, HI (United States)

    2012-09-15

    The global monsoon (GM) is a defining feature of the annual variation of Earth's climate system. Quantifying and understanding the present-day monsoon precipitation change are crucial for prediction of its future and reflection of its past. Here we show that regional monsoons are coordinated not only by external solar forcing but also by internal feedback processes such as El Nino-Southern Oscillation (ENSO). From one monsoon year (May to the next April) to the next, most continental monsoon regions, separated by vast areas of arid trade winds and deserts, vary in a cohesive manner driven by ENSO. The ENSO has tighter regulation on the northern hemisphere summer monsoon (NHSM) than on the southern hemisphere summer monsoon (SHSM). More notably, the GM precipitation (GMP) has intensified over the past three decades mainly due to the significant upward trend in NHSM. The intensification of the GMP originates primarily from an enhanced east-west thermal contrast in the Pacific Ocean, which is coupled with a rising pressure in the subtropical eastern Pacific and decreasing pressure over the Indo-Pacific warm pool. While this mechanism tends to amplify both the NHSM and SHSM, the stronger (weaker) warming trend in the NH (SH) creates a hemispheric thermal contrast, which favors intensification of the NHSM but weakens the SHSM. The enhanced Pacific zonal thermal contrast is largely a result of natural variability, whilst the enhanced hemispherical thermal contrast is likely due to anthropogenic forcing. We found that the enhanced global summer monsoon not only amplifies the annual cycle of tropical climate but also promotes directly a ''wet-gets-wetter'' trend pattern and indirectly a ''dry-gets-drier'' trend pattern through coupling with deserts and trade winds. The mechanisms recognized in this study suggest a way forward for understanding past and future changes of the GM in terms of its driven mechanisms. (orig.)

  7. Seasonal changes in suspended sediment load in the Gauthami-Godavari Estuary

    Digital Repository Service at National Institute of Oceanography (India)

    Reddy, N.P.C.; Rao, B.P.; Rao, K.M.; Rao, V.S.

    estuarine mouths. During pre-monsoon and northeast monsoon seasons, the CSM is mainly controlled by the tidal currents (10 cm/s to 150 cm/s) as the fresh water discharge during this period is minimum. Higher CSM (270 mg/l) at Vrudha estuarine mouth compared...

  8. Circulation and mixing process in Vasishta-Godavari estuary, east coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Kumar, A.R.S.; Murty, T.V.R.; Rao, M.M.M; Rao, V.R.; Reddy, B.S.R.

    coefficient ranges between 20880 m sup(2)/s - 3888 m sup(2)/s in the southwest monsoon season (July-September) while for post and pre-monsoon seasons (November-May) the coefficient is between 515 m sup(2)/s and zero. The fluctuations in diffusion coefficients...

  9. Anti Diabetic Plants Present In West Godavari District Of Andhra Pradesh India- A Short Review.

    Directory of Open Access Journals (Sweden)

    Venkata Narasimha Kadali

    2016-02-01

    Full Text Available Diabetes is considered as one of the chronic disease more prevalent in India and rest of the world. Chronic hyperglycemia leads to the destruction of different organs in the body.There are lots of synthetic drugs present in the market for the treatment of diabetes but they are prone to noxious effects to human systems. Herbs have natural inhibiting potency against various sorts of diseases and they are the ultimate source of bio active compounds which lacks toxic effects. Medicinal plants which have potent anti hyperglycemic effect have been identified and proved experimentally. In this short review an attempt has been made to review some of the medicinal plants such as Annona reticulata, Carica papaya, Coccinia grandis, Moringa oleifera, Murraya koenigi etc., of about 10 species which are proved to be anti diabetic present in the west godavari district of Andhra Pradesh, India.

  10. Wetlands sediment record from the upper Yarlung Tsangpo valley, southwest Tibetan Plateau, reveals mid-Holocene Epipaleolithic human occupation coincident with increased early and mid-Holocene wetness driven by enhanced Indian Monsoon rainfall

    Science.gov (United States)

    Hudson, A. M.; Olsen, J. W.; Quade, J.; Lei, G.; Huth, T.; Zhang, H.; Perreault, C.

    2016-12-01

    The headwaters of the Yarlung Tsangpo river valley, located in the southwestern Tibetan Plateau, are characterized by a cold and dry climate, but contain abundant river-marginal wetlands environments, which fluctuate in extent in response to changes in local water table elevation. This region receives 80% of precipitation from the Indian Monsoon, which forms the dominant control on moisture availability, and hence wetlands extent. Our paleowetlands record, based on 14C dating of organic-rich paleowetlands deposits, provides a novel record of Holocene monsoon intensity. The wetlands deposits consist of four sedimentary units that indicate decreasing wetlands extent and monsoon intensity since 10.4 ka BP. Wet conditions occurred at ˜10.4 ka BP, ˜9.6 ka BP and ˜7.9-4.8 ka BP, with similar-to-modern conditions from ˜4.6-2.0 ka BP, and drier-than-modern conditions from ˜2.0 ka BP to present. Wetland changes correlate with monsoon intensity changes identified in nearby records, with weak monsoon intervals corresponding to desiccation and erosion of wetlands deposits. Dating of in situ ceramic and microlithic artifacts in wetlands sediments at multiple sites indicates Epipaleolithic human occupation of the YT valley after 6.6 ka BP. Artifact typology study reveals a similar microlithic technology was employed across the high plateau interior, but XRF obsidian provenance reveals separate northeast and southwest lithic conveyance zones. This indicates widespread colonization of the high, arid Tibetan Plateau interior by one or more highly mobile human populations during the early and mid-Holocene, coincident with favorable warm, wet climate conditions.

  11. Coastal processes at the southern tip of India during summer monsoon 2005

    Digital Repository Service at National Institute of Oceanography (India)

    Smitha, B.R.; VimalKumar, K.G.; Sanjeevan, V.N.

    In situ temperature and wind data, during summer monsoon 2005, bring out some interesting features like, the existence of a purely wind driven upweiling system at the southern tip (ST), very adjacent to another remotely forced upweiling system...

  12. Oral health status and treatment needs among 10126 school children in West Godavari district, Andhra Pradesh, India

    Science.gov (United States)

    Prasad, M. Ghanashyam; Radhakrishna, A. Naga; Kambalimath, Halaswamy V.; Chandrasekhar, Shalini; Deepthi, B.; Ramakrishna, J.

    2016-01-01

    Objectives: Oral diseases are affecting a large percentage of children worldwide. This study with Indian Society of Pedodontics and Preventive Dentistry collaboration was taken up with the aim to evaluate the oral health status and treatment needs in school-going children of the West Godavari district, Andhra Pradesh, India. Materials and Methods: This cross-sectional study was conducted among 10126 school children who were randomly selected from 32 schools in West Godavari district. To find the significance of the obtained number of cases for different age groups, Chi-square test of significance was used. Results: The prevalence of dental conditions are as follows: Dental caries 63.5%, periodontal diseases 13.6%, dental anomalies 3.6%, dental trauma 3.2%, and orthodontic treatment 25.1%. Among the different age groups, 11–14 years age group has the highest prevalence of oral health problems. Females were more affected with dental caries (P = 0.17), orthodontic treatment needs (P = 0.12), and dental anomalies (P = 0.86) compared to males which was statistically insignificant. The highest prevalence of dental conditions in the case of females was observed during the age of 11–14 years, and in males, the peak was seen in the 15–18 years age group. Conclusions: This study demonstrated that school-going children in West Godavari district suffer from a high prevalence of dental conditions and have higher treatment needs. PMID:27382536

  13. Increased particle flux to the deep ocean related to monsoons

    Digital Repository Service at National Institute of Oceanography (India)

    Nair, R.R.; Ittekkot, V.; Manganini, S.J.; Ramaswamy, V.; Haake, B.; Degens, E.T.; Desai, B.N.; Honjo, S.

    . To assess the impact of monsoon-driven processes on the downward particle flux variations in the open ocean we deployed three moored arrays consisting of six time-series sediment traps at selected locations in the western, central and eastern parts...

  14. Acoustic reflections in the water column of Krishna-Godavari offshore basin, Bay of Bengal.

    Science.gov (United States)

    Sinha, Satish K; Dewangan, Pawan; Sain, Kalachand

    2016-05-01

    Seismic oceanographic studies from various oceans worldwide have indicated that the acoustic reflections are mostly observed along thermal boundaries within the water column. However, the authors present a case study of seismic data from Krishna-Godavari Basin which shows that salinity variations also play an important role in the occurrence of water column reflections. The observed reflection is modeled using the reflectivity series derived from the salinity and temperature profiles from a nearby Conductivity-Temperature-Depth (CTD) location. Sensitivity analysis of temperature and salinity on soundspeed shows that the effect of salinity cannot be ignored for modeling acoustic reflections. The synthetic seismogram matches well with the observed reflection seismic data. Remarkable similarities between the reflection seismic and the salinity profile in the upper thermocline suggest the importance of salinity variations on the water column reflection. Furthermore, impedance inversion of the reflectivity data reveals several thermohaline structures in the water column. The origin of these thermohaline structures is largely unaddressed and may be attributed to the fresh water influx coming from Himalayan and Peninsular rivers or due to the presence of different water masses in the Indian Ocean which warrants a detailed study using concurrent seismic and CTD data.

  15. Metazoan Parasite Infracommunities of the Freshwater Eel, Mastacembelus armatus Lacpde, 1800 from River Godavari, India

    Directory of Open Access Journals (Sweden)

    G. Mani

    2011-01-01

    Full Text Available Mastacembelus armatus is considered to be the delicacy of Southern India. Four hundred ninety four specimens of M. armatus collected from river Godavari from August 2005 to September 2007 were analyzed in order to study their metazoan parasite infracommunities. Twelve species of parasites were collected, 6 digenea, 2 cestodes, 1 monogenea, 1 copepoda, 1 nematoda and 1 acanthocephala; 78% of the fishes were parasitized by one or more than one metazoan, with a mean of 67 parasites/fish. The endoparasites represents 98.3% of the total parasites collected. The digenean Tetracotyle sp. and Circumonchobothrium shindei occupy the position of secondary species and the remaining were satellite species. Relationships between total body length of fish and both total parasite abundance and mean parasite species richness were observed. A new copepod species, Neoergasilus indicus is also encountered in the present investigation. The metazoan parasite infracommunities of M. armatus presented dominance of larval endoparasites; correlation of parasite burden, diversity and species richness with host total length; and no influence of host sex on parasitisation.

  16. Magnetic anomalies across Bastar craton and Pranhita–Godavari basin in south of central India

    Indian Academy of Sciences (India)

    I V Radhakrishna Murthy; S Bangaru Babu

    2009-02-01

    Aeromagnetic anomalies over Bastar craton and Pranhita –Godavari (P –G)basin in the south of central India could be attributed to NW –SE striking mafic intrusives in both the areas at variable depths.Such intrusions can be explained considering the collision of the Bastar and Dharwar cratons by the end of the Archaean and the development of tensile regimes that followed in the Paleoproterozoic,facilitating intrusions of mafic dykes into the continental crust.The P –G basin area,being a zone of crustal weakness along the contact of the Bastar and Dharwar cratons, also experienced extensional tectonics.The inferred remanent magnetization of these dykes dips upwards and it is such that the dykes are oriented towards the east of the magnetic north at the time of their formation compared to their present NW –SE strike.Assuming that there was no imprint of magnetization of a later date,it is concluded that the Indian plate was located in the southern hemisphere,either independently or as part of a supercontinent,for some span of time during Paleoproterozoic and was involved in complex path of movement and rotation subsequently. The paper presents a case study of the utility of aeromagnetic anomalies in qualitatively deducing the palaeopositions of the landmasses from the interpreted remanent magnetism of buried intrusive bodies.

  17. Palynological correlation of coal-bearing horizons in Gundala area, Godavari Graben, India

    Indian Academy of Sciences (India)

    Neerja Jha; Neha Aggarwal

    2011-08-01

    The distributional pattern of various palynotaxa in the coal bearing sediments recovered from six borecores (MLG-23, MLG-24, MLG-28, SGK-2, SGK-3 and SGK-4) in Gundala area of Godavari Graben has suggested occurrence of five distinct palynoassemblages: Palynoassemblage-A marked in borecore MLG-23 shows dominance of monosaccates chiefly Parasaccites along with Plicatipollenites, Caheniasaccites, Divarisaccus, and Potonieisporites, represents Talchir palynoflora; Palynoassemblage-B characterized by dominance of radial monosaccates chiefly Parasaccites along with trilete taxa Callumispora in borecores MLG-23 and MLG-24, corresponds to Lower Karharbari palynoflora; Palynoassemblage-C distinguished in borecores MLG-24, MLG-28, SGK-2, SGK-3 and SGK-4 is marked by dominance of radial monosaccates mainly Parasaccites along with nonstriate disaccate Scheuringipollenites, represents Upper Karharbari palynoflora; Palynoassemblage-D in borecores MLG-23, MLG-24 and MLG-28 demarcated by dominance of nonstriate disaccates chiefly Scheuringipollenites, Ibisporites along with sub-dominance of few striate disaccates, viz., Faunipollenites, Striatopodocarpites, Crescentipollenites and Striatites signifies Barakar palynoflora; the youngest, Palynoassemblage-E identified in borecores MLG-24 and MLG-28 shows dominance of striate disaccates, viz., Striatopodocarpites and Faunipollenites in conjunction with Strotersporites, Crescentipollenites, Hamiapollenites, Corisaccites, Weylandites and Falcisporites. This palynoassemblage also shows the appearance of some stratigraphically significant palynomorphs, viz., Lunatisporites, Lundbladispora, Playfordiaspora, Klausipollenites, Kamthisaccites, Guttulapollenites and Crustaesporites symbolizing Late Permian Raniganj palynoflora. Almost a complete palynological succession from Talchir to Raniganj has been demarcated in Lower Gondwana succession of Gundala area.

  18. Orbital control on late Miocene climate and the North African monsoon : Insight from an ensemble of sub-precessional simulations

    NARCIS (Netherlands)

    Marzocchi, A.; Lunt, D. J.; Flecker, R.; Bradshaw, C. D.; Farnsworth, A.; Hilgen, F. J.

    2015-01-01

    Orbital forcing is a key climate driver over multi-millennial timescales. In particular, monsoon systems are thought to be driven by orbital cyclicity, especially by precession. Here, we analyse the impact of orbital forcing on global climate with a particular focus on the North African monsoon, by

  19. Indian monsoon variability on millennial-orbital timescales.

    Science.gov (United States)

    Kathayat, Gayatri; Cheng, Hai; Sinha, Ashish; Spötl, Christoph; Edwards, R Lawrence; Zhang, Haiwei; Li, Xianglei; Yi, Liang; Ning, Youfeng; Cai, Yanjun; Lui, Weiguo Lui; Breitenbach, Sebastian F M

    2016-04-13

    The Indian summer monsoon (ISM) monsoon is critical to billions of people living in the region. Yet, significant debates remain on primary ISM drivers on millennial-orbital timescales. Here, we use speleothem oxygen isotope (δ(18)O) data from Bittoo cave, Northern India to reconstruct ISM variability over the past 280,000 years. We find strong coherence between North Indian and Chinese speleothem δ(18)O records from the East Asian monsoon domain, suggesting that both Asian monsoon subsystems exhibit a coupled response to changes in Northern Hemisphere summer insolation (NHSI) without significant temporal lags, supporting the view that the tropical-subtropical monsoon variability is driven directly by precession-induced changes in NHSI. Comparisons of the North Indian record with both Antarctic ice core and sea-surface temperature records from the southern Indian Ocean over the last glacial period do not suggest a dominant role of Southern Hemisphere climate processes in regulating the ISM variability on millennial-orbital timescales.

  20. Computation of diffusion coefficients for waters of Gauthami Godavari estuary using one-dimensional advection-diffusion model

    Digital Repository Service at National Institute of Oceanography (India)

    Jyothi, D.; Murty, T.V.R.; Sarma, V.V.; Rao, D.P.

    of Marine Sciences Vol. 29, June 2000, pp. 185-187 Short Communication Computation of diffusion coefficients for waters of Gauthami Godavari estuary using one-dimensional advection-diffusion model D Jyothi, T V Ramana Murty, V V Sarma & D P Rao National.... - Jan.) Y2(x) = 8.55283 x + 17.5469 (Jan. - April) These equations would be more useful to get diffusion coefficients for any point along the channel axis, which in turn, helps to compute the concentration of pollutant along the axis of estuary. Thus...

  1. Prediction of gas hydrate saturation throughout the seismic section in Krishna Godavari basin using multivariate linear regression and multi-layer feed forward neural network approach

    Digital Repository Service at National Institute of Oceanography (India)

    Singh, Y.; Nair, R.R.; Singh, H.; Datta, P.; Jaiswal, P.; Dewangan, P.; Ramprasad, T.

    -Godavari basin. Log prediction process, with uncertainties based on root mean square error properties, was implemented by way of a multi-layer feed forward neural network. The log properties were merged with seismic data by applying a non-linear transform...

  2. Behaviour of fluoride and dissolved silicon in Gouthami Godavari estuarine environment

    Digital Repository Service at National Institute of Oceanography (India)

    Sarma, V.V.; Sudhakar, U.; Varaprasad, S.J.D.

    post-monsoon season. However, during premonsoon season, removal of approximately 16% in case of fluoride and 41% in case of dissolved silicon was found during mixing of sea and river waters. The possible mechanisms for removal of both the elements have...

  3. Geochemistry and petrogenesis of Rajahmundry trap basalts of Krishna-Godavari Basin, India

    Directory of Open Access Journals (Sweden)

    C. Manikyamba

    2015-05-01

    Full Text Available The Rajahmundry Trap Basalts (RTB are erupted through fault-controlled fissures in the Krishna-Godavari Basin (K-G Basin of Godavari Triple Junction, occurring as a unique outcrop sandwiched between Cretaceous and Tertiary sediments along the east coast of India. Detailed geochemical studies have revealed that RTB are mid-Ti (1.74–1.92 to high-Ti (2.04–2.81 basalts with a distinct quartz tholeiitic parentage. MgO (6.2–13.12 wt.%, Mg# (29–50 and Zr (109–202 ppm suggest that these basalts evolved by fractional crystallization during the ascent of the parent magma along deep-seated fractures. Moderate to high fractionation of HREE, as indicated by (Gd/YbN ratios (1.71–2.31 of RTB, suggest their generation through 3–5% melting of a Fe-rich mantle corresponding to the stability fields of spinel and garnet peridotite at depths of 60–100 km. Low K2O/P2O5 (0.26–1.26, high TiO2/P2O5 (6.74–16.79, La/Nb (0.89–1.45, Nb/Th > 8 (8.35–13, negative anomalies at Rb reflect minimum contamination by granitic continental crust. (Nb/LaPM ratios (0.66–1.1 of RTB are attributed to endogenic contamination resulted through recycling of subducted oceanic slab into the mantle. Pronounced Ba enrichment with relative depletion in Rb indicates assimilation of Infra- and Inter-trappean sediments of estuarine to shallow marine character. Geochemical compositions such as Al2O3/TiO2 (3.88–6.83, medium to high TiO2 (1.74–2.81 wt.%, positive Nb anomalies and LREE enrichment of these RTB attest to their mantle plume origin and indicate the generation of parent magma from a plume-related enriched mantle source with EM I signature. Ba/Th (46–247, Ba/La (3.96–28.51 and Th/Nb (0.08–0.13 ratios suggest that the source enrichment process was marked by recycling of subduction-processed oceanic crust and lithospheric components into the mantle. Zr/Hf (37–41 and Zr/Ba (0.51–3.24 indicate involvement of an asthenospheric mantle source. The

  4. Upper Cisuralian palynology and palaeoclimate of Manuguru area Godavari basin, and their global correlation

    Indian Academy of Sciences (India)

    Pauline Sabina K; Neerja Jha

    2014-10-01

    The Permian system of the Palaeozoic Erathem is divided into three series, the Early Permian Cisuralian Series, the Middle Permian Guadalupian Series, and the Late Permian Lopingian Series. The Cisuralian Series encompasses the Asselian to Kungurian stages which constitute the basal part of the Gondwana supersequence I. In India, they are represented lithostratigraphically by the Talchir, Karharbari, and Barakar formations. This paper presents the palynological results from the Barakar Formation of the Upper Cisuralian Series from Manuguru which lies in the southeastern part of the Godavari basin. The succession studied comprises 35 subsurface samples from bore hole 1007 represented by clay, shale, sandstone, and coal. The palynofloras in this sequence have a homogenous composition demonstrating that not many significant floral changes took place through the considered stratigraphic range. The entire sequence is characterized by the dominance of nonstriate bisaccate genus Scheuringipollenites and subdominance of striate bisaccate genus Faunipollenites (=Protohaploxypinus). The other pollen genera among the nonstriate bisaccates are Rhizomaspora, Primuspollenites, Ibisporites, and Platysaccus. The striate bisaccates include Striatites, Striatopodocarpites, and Stroterosporites. The taeniate taxa are represented by Lueckisporites and Lunatisporites. The common monosaccate genera include Caheniasaccites, Potoniesporites, and Barakarites. Spores are less common and include Latosporites, Brevitriletes, Horriditriletes, Microbaculispora, and Callumispora. They characterize the palynofloral composition of the Lower Barakar Formation. The correlation of this assemblage with some of the biostratigraphic palynozones proposed previously for the Cisuralian sequences of the Paraná Basin of South America, Kalahari Karoo Basin of South Africa, Ruhuhu Basin of Tanzania, East Africa as well as palynoassemblages from South Victoria Land and Dronning Maud Land, Antarctica and Collie

  5. CORONARY ARTERY DOMINANCE PATTERN IN EAST-GODAVARI DISTRICT: A CADAVERIC STUDY

    Directory of Open Access Journals (Sweden)

    Arindom

    2016-01-01

    Full Text Available With the advent of coronary angiography, coronary artery diseases can be well combated; but with time sedentary life style and stress as our constant partner have kept coronary artery disease as one of the major causes of death. Revascularization procedures demand a sound knowledge of the course of coronary arteries and their branches, both normal and their quite common variations. In this regard, posterior inter-ventricular artery (PIVA deserves a special importance; PIVA determines the coronary dominance depending on its parent artery. Dominance can be right, left or of balanced type. Balanced type means that PIVA is derived from both right & left coronary arteries. Circulation can occur when both the coronary arteries emit a branch in that area. These and other variations form a very important repertoire of information based on which coronary bypass surgery and angioplasty can be safely and effectively performed. The aim of this study therefore is to document the coronary dominance pattern in this East Godavari district of Andhra-Pradesh. 60 adult human hearts were collected from museum of Anatomy department during the tenure of 5 years (2009 to 2014 and were preserved in 10% formalin. The hearts were dissected carefully to observe the posterior inter-ventricular artery in the posterior inter-ventricular sulcus of each heart and dominance pattern was recorded. In our present study right dominance type was the commonest (46 out of 60 followed by left dominance (10 out of 60. Only 4 out of 60 were of the balanced type. Present study, though not of the only member of its kind will definitely add up to the already existing vast knowledge, based on which various diagnostic and therapeutic intervention of coronary artery diseases can be done effectively and safely

  6. Seismic imaging of a fractured gas hydrate system in the Krishna-Godavari Basin offshore India

    Science.gov (United States)

    Riedel, M.; Collett, T.S.; Kumar, P.; Sathe, A.V.; Cook, A.

    2010-01-01

    Gas hydrate was discovered in the Krishna-Godavari (KG) Basin during the India National Gas Hydrate Program (NGHP) Expedition 1 at Site NGHP-01-10 within a fractured clay-dominated sedimentary system. Logging-while-drilling (LWD), coring, and wire-line logging confirmed gas hydrate dominantly in fractures at four borehole sites spanning a 500m transect. Three-dimensional (3D) seismic data were subsequently used to image the fractured system and explain the occurrence of gas hydrate associated with the fractures. A system of two fault-sets was identified, part of a typical passive margin tectonic setting. The LWD-derived fracture network at Hole NGHP-01-10A is to some extent seen in the seismic data and was mapped using seismic coherency attributes. The fractured system around Site NGHP-01-10 extends over a triangular-shaped area of ~2.5 km2 defined using seismic attributes of the seafloor reflection, as well as " seismic sweetness" at the base of the gas hydrate occurrence zone. The triangular shaped area is also showing a polygonal (nearly hexagonal) fault pattern, distinct from other more rectangular fault patterns observed in the study area. The occurrence of gas hydrate at Site NGHP-01-10 is the result of a specific combination of tectonic fault orientations and the abundance of free gas migration from a deeper gas source. The triangular-shaped area of enriched gas hydrate occurrence is bound by two faults acting as migration conduits. Additionally, the fault-associated sediment deformation provides a possible migration pathway for the free gas from the deeper gas source into the gas hydrate stability zone. It is proposed that there are additional locations in the KG Basin with possible gas hydrate accumulation of similar tectonic conditions, and one such location was identified from the 3D seismic data ~6 km NW of Site NGHP-01-10. ?? 2010.

  7. Orbital pacing and ocean circulation-induced collapses of the Mesoamerican monsoon over the past 22,000 y.

    Science.gov (United States)

    Lachniet, Matthew S; Asmerom, Yemane; Bernal, Juan Pablo; Polyak, Victor J; Vazquez-Selem, Lorenzo

    2013-06-04

    The dominant controls on global paleomonsoon strength include summer insolation driven by precession cycles, ocean circulation through its influence on atmospheric circulation, and sea-surface temperatures. However, few records from the summer North American Monsoon system are available to test for a synchronous response with other global monsoons to shared forcings. In particular, the monsoon response to widespread atmospheric reorganizations associated with disruptions of the Atlantic Meridional Overturning Circulation (AMOC) during the deglacial period remains unconstrained. Here, we present a high-resolution and radiometrically dated monsoon rainfall reconstruction over the past 22,000 y from speleothems of tropical southwestern Mexico. The data document an active Last Glacial Maximum (18-24 cal ka B.P.) monsoon with similar δ(18)O values to the modern, and that the monsoon collapsed during periods of weakened AMOC during Heinrich stadial 1 (ca. 17 ka) and the Younger Dryas (12.9-11.5 ka). The Holocene was marked by a trend to a weaker monsoon that was paced by orbital insolation. We conclude that the Mesoamerican monsoon responded in concert with other global monsoon regions, and that monsoon strength was driven by variations in the strength and latitudinal position of the Intertropical Convergence Zone, which was forced by AMOC variations in the North Atlantic Ocean. The surprising observation of an active Last Glacial Maximum monsoon is attributed to an active but shallow AMOC and proximity to the Intertropical Convergence Zone. The emergence of agriculture in southwestern Mexico was likely only possible after monsoon strengthening in the Early Holocene at ca. 11 ka.

  8. Redistribution of low-salinity pools off east coast of India during southwest monsoon season

    Science.gov (United States)

    Mahapatra, D. K.; Rao, A. D.

    2017-01-01

    The east coast of India receives significant inputs of fresh water into the Bay of Bengal during the southwest monsoon in comparison with the lower influx seen on the west coast. However, in situ observations made off the east coast suggest that in some years low-salinity pools appear offshore, as opposed to where the river discharge actually takes place. To date, no studies have offered any plausible reason for this anomaly. In an attempt to understand the processes involved, we used numerical modelling to elucidate the causes and mechanisms underlying the appearance of offshore low salinity pools. The model uses temperature and salinity information from the World Ocean Atlas 2001 as initial conditions, and is forced using wind stress derived from the weekly wind for July 2002 and 2010 from the NCEP FNL Operational Global Analysis, because of the need to validate the model using more recent observations. It was found that the formation of a low-salinity pool to the south of 16°N and its migration to an offshore region is a result of (i) coastal orientation, (ii) surface circulation supported by a weak East India Coastal Current that redistributes fresh water from two rivers, the Krishna and Godavari, and (iii) an influx of low salinity from the much larger river system to the north, resulting in anomalous pool(s) of low-salinity waters away from the coast. These findings are corroborated by CTD data, ARGO data, and Ocean Surface Current Analysis Real-Time currents.

  9. The role of the Indian monsoon onset in the West African monsoon onset: observations and AGCM nudged simulations

    Energy Technology Data Exchange (ETDEWEB)

    Flaounas, Emmanouil [LATMOS/IPSL, Universite Pierre et Marie Curie, Paris cedex 05 (France); Janicot, Serge [LOCEAN/IPSL, IRD, Universite Pierre et Marie Curie, Paris (France); Bastin, Sophie [LATMOS/IPSL, CNRS, Universite Pierre et Marie Curie, Paris (France); Roca, Remy [LMD/IPSL, CNRS, Universite Pierre et Marie Curie, Paris (France); Mohino, Elsa [LOCEAN/IPSL, CNRS, Universite Pierre et Marie Curie, Paris (France); Universidad de Sevilla, Sevilla (Spain)

    2012-03-15

    In spring the inland penetration of the West African Monsoon (WAM) is weak and the associated rainband is located over the Guinean coast. Then within a few days deep convection weakens considerably and the rainband reappears about 20 days after over the Sahel, where it remains until late September signalling the summer rainy season. Over the period 1989-2008 a teleconnection induced by the Indian monsoon onset is shown to have a significant impact on the WAM onset, by performing composite analyses on both observational data sets and atmospheric general circulation model simulations ensembles where the model is nudged to observations over the Indian monsoon sector. The initiation of convective activity over the Indian subcontinent north of 15 N at the time of the Indian monsoon onset results in a westward propagating Rossby wave establishing over North Africa 7-15 days after. A back-trajectory analysis shows that during this period, dry air originating from the westerly subtropical jet entrance is driven to subside and move southward over West Africa inhibiting convection there. At the same time the low-level pressure field over West Africa reinforces the moisture transport inland. After the passage of the wave, the dry air intrusions weaken drastically. Hence 20 days after the Indian monsoon onset, convection is released over the Sahel where thermodynamic conditions are more favourable. This scenario is very similar in the observations and in the nudged simulations, meaning that the Indian monsoon onset is instrumental in the WAM onset and its predictability at intraseasonal scale. (orig.)

  10. Role of low level flow on the summer monsoon rainfall over the Indian subcontinent during two contrasting monsoon years

    Digital Repository Service at National Institute of Oceanography (India)

    Swapna, P.; RameshKumar, M.R.

    The summer monsoon rainfall over the Indian subcontinent shows 1 large inter-annual variability in three important aspects, namely, the onset date, quantum of monsoon rainfall and the monsoon activity within the monsoon (June - September) period...

  11. Documenting channel features associated with gas hydrates in the Krishna-Godavari Basin, offshore India

    Science.gov (United States)

    Riedel, M.; Collett, T.S.; Shankar, U.

    2011-01-01

    During the India National Gas Hydrate Program (NGHP) Expedition 01 in 2006 significant sand and gas hydrate were recovered at Site NGHP-01-15 within the Krishna-Godavari Basin, East Coast off India. At the drill site NGHP-01-15, a 5-8m thick interval was found that is characterized by higher sand content than anywhere else at the site and within the KG Basin. Gas hydrate concentrations were determined to be 20-40% of the pore volume using wire-line electrical resistivity data as well as core-derived pore-fluid freshening trends. The gas hydrate-bearing interval was linked to a prominent seismic reflection observed in the 3D seismic data. This reflection event, mapped for about 1km2 south of the drill site, is bound by a fault at its northern limit that may act as migration conduit for free gas to enter the gas hydrate stability zone (GHSZ) and subsequently charge the sand-rich layer. On 3D and additional regional 2D seismic data a prominent channel system was imaged mainly by using the seismic instantaneous amplitude attribute. The channel can be clearly identified by changes in the seismic character of the channel fill (sand-rich) and pronounced levees (less sand content than in the fill, but higher than in surrounding mud-dominated sediments). The entire channel sequence (channel fill and levees) has been subsequently covered and back-filled with a more mud-prone sediment sequence. Where the levees intersect the base of the GHSZ, their reflection strengths are significantly increased to 5- to 6-times the surrounding reflection amplitudes. Using the 3D seismic data these high-amplitude reflection edges where linked to the gas hydrate-bearing layer at Site NGHP-01-15. Further south along the channel the same reflection elements representing the levees do not show similarly large reflection amplitudes. However, the channel system is still characterized by several high-amplitude reflection events (a few hundred meters wide and up to ~1km in extent) interpreted as gas

  12. Macrobenthos of Kakinada Bay in the Godavari delta, East coast of India: comparing decadal changes

    Science.gov (United States)

    Raut, Dipti; Ganesh, T.; Murty, N. V. S. S.; Raman, A. V.

    2005-03-01

    A one-year study (1995-1996) on the macrobenthos over a spread of (37) hydrographically differing GPS-fixed sites in Kakinada Bay (mean salinity 27.16±0.4) and adjacent mangrove channels (14.78±0.55) in the Godavari delta, one of India's largest estuarine systems, revealed a great preponderance of benthic life. There were 11 diverse taxa represented by 95 species collected through several (303) grab and dredge hauls. Based on Bray-Curtis similarity through hierarchical clustering implemented in PRIMER, it was possible to distinguish the benthos into four assemblages each of which represented sites in the Central and North bay ( Paphia textrix - Typhlocarcinus sp. Assemblage), South-East bay ( Protankyra similis - Paphia malabarica Assemblage), Mangrove Outlets ( Cerithidea cingulata Assemblage) and Mangrove channels ( Diopatra neapolitana Assemblage). Benthos densities (mean nos. dredge haul -1) were highest (299 individuals) at sites close to mangrove outlets. Species diversity (Margalef, d; Shannon-Wiener, H') was low in general ( d 1.244 to 2.251 and H' 0.038 to 1.502). Sediments were mostly clayey-silt in nature except in southeast bay where they are silt-sand. Organic matter (mean) was at or near 1.3%. The observations have revealed marked changes in benthic community structure relative to an earlier investigation held in 1958-1963 in this area. Over the years, species such as Turritella duplicata, Tonna dolium and Placuna placenta found in considerable numbers previously have dwindled. Anomia, Bursa and Atrina and echinoderms, Astropecten indica, Echinodiscus auritus and Temnopleurus toreumaticus and the brachiopod, Lingula sp. of common occurrence in early 60s are absent altogether attributable to long-term natural trends during the intervening years and/or events accompanying human impingement (e.g. industrial and urban growth, port expansion measures, aquaculture, mangrove denudation etc.). Despite such large-scale alterations in benthos community

  13. Global warming and South Indian monsoon rainfall-lessons from the Mid-Miocene.

    Science.gov (United States)

    Reuter, Markus; Kern, Andrea K; Harzhauser, Mathias; Kroh, Andreas; Piller, Werner E

    2013-04-01

    Precipitation over India is driven by the Indian monsoon. Although changes in this atmospheric circulation are caused by the differential seasonal diabatic heating of Asia and the Indo-Pacific Ocean, it is so far unknown how global warming influences the monsoon rainfalls regionally. Herein, we present a Miocene pollen flora as the first direct proxy for monsoon over southern India during the Middle Miocene Climate Optimum. To identify climatic key parameters, such as mean annual temperature, warmest month temperature, coldest month temperature, mean annual precipitation, mean precipitation during the driest month, mean precipitation during the wettest month and mean precipitation during the warmest month the Coexistence Approach is applied. Irrespective of a ~ 3-4 °C higher global temperature during the Middle Miocene Climate Optimum, the results indicate a modern-like monsoonal precipitation pattern contrasting marine proxies which point to a strong decline of Indian monsoon in the Himalaya at this time. Therefore, the strength of monsoon rainfall in tropical India appears neither to be related to global warming nor to be linked with the atmospheric conditions over the Tibetan Plateau. For the future it implies that increased global warming does not necessarily entail changes in the South Indian monsoon rainfall.

  14. Meteorological results of monsoon-88 Expedition (pre-monsoon period)

    Digital Repository Service at National Institute of Oceanography (India)

    Sadhuram, Y.; Krishnamurthy, L.; Babu, M.T.

    Mean atmospheric circulation, moisture budget and net heat exchange were studied during a pre-monsoon period (18th March to 3rd May, 1988), making use of the data collected on board "Akademik Korolev" in the central equatorial and southern Arabian...

  15. Geophysical and Geochemical Approach for Seawater Intrusion Assessment in the Godavari Delta Basin, A.P., India.

    Science.gov (United States)

    Gurunadha Rao, V V S; Rao, G Tamma; Surinaidu, L; Rajesh, R; Mahesh, J

    2011-05-01

    Coastal lands around Bay of Bengal in Central Godavari Delta are mainly agriculture fields and two times annually paddy crops putting in the study area. Canals of Godavari River are the main source of water for irrigation. Geophysical and geochemical investigations were carried out in the study area to decipher subsurface geologic formation and assessing seawater intrusion. Electrical resistivity tomographic surveys carried out in the watershed-indicated low resistivity formation in the upstream area due to the presence of thick marine clays up to thickness of 20-25 m from the surface. Secondly, the lowering of resistivity may be due to the encroachment of seawater in to freshwater zones and infiltration during tidal fluctuation through mainly the Pikaleru drain, and to some extent rarely through Kannvaram and Vasalatippa drains in the downstream area. Groundwater quality analyses were made for major ions revealed brackish nature of groundwater water at shallow depth. The in situ salinity of groundwater is around 5,000 mg/l and there is no groundwater withdrawal for irrigation or drinking purpose in this area except Cairn energy pumping wells which is using for inject brackish water into the oil wells for easy exploration of oil. Chemical analyses of groundwater samples have indicated the range of salt concentrations and correlation of geophysical and borehole litholog data in the study area predicting seawater-contaminated zones and influence of in situ salinity in the upstream of study area. The article suggested further studies and research work that can lead to sustainable exploitation/use and management of groundwater resources in coastal areas.

  16. Dominating Controls for Wetter South Asian Summer Monsoon in the Twenty-First Century

    Energy Technology Data Exchange (ETDEWEB)

    Mei, Rui; Ashfaq, Moetasim; Rastogi, Deeksha; Leung, Lai-Yung R.; Dominguez, Francina

    2015-04-01

    We analyze a suite of Global Climate Models from the 5th Phase of Coupled Models Intercomparison Project (CMIP5) archives to understand the mechanisms behind a net increase in the South Asian summer monsoon precipitation in response to enhanced radiative forcing during the 21st century despite a robust weakening of dynamics governing the monsoon circulation. Combining the future changes in the contributions from various sources, which contribute to the moisture supply over South Asia, with those in monsoon dynamics and atmospheric moisture content, we establish a pathway of understanding that partly explains these counteracting responses to increase in radiative forcing. Our analysis suggests that both regional (local recycling, Arabian Sea, Bay of Bengal) and remote (mainly Indian Ocean) sources contribute to the moisture supply for precipitation over South Asia during the summer season that is facilitated by the monsoon dynamics. Increase in radiative forcing fuels an increase in the atmospheric moisture content through warmer temperatures. For regional moisture sources, the effect of excessive atmospheric moisture is offset by weaker monsoon circulation and uncertainty in the response of the evapotranspiration over land, so anomalies in their contribution to the total moisture supply are either mixed or muted. In contrast, weakening of the monsoon dynamics has less influence on the moisture supply from remote sources that not only is a dominant moisture contributor in the historical period, but is also the net driver of the positive summer monsoon precipitation response in the 21st century. Our results also indicate that historic measures of the monsoon dynamics may not be well suited to predict the non-stationary moisture driven South Asian summer monsoon precipitation response in the 21st century.

  17. Geochemistry and petrogenesis of Rajahmundry trap basalts of Krishna-Godavari Basin, India

    Institute of Scientific and Technical Information of China (English)

    C. Manikyamba; Sohini Ganguly; M. Santosh; Abhishek Saha; G. Lakshminarayana

    2015-01-01

    The Rajahmundry Trap Basalts (RTB) are erupted through fault-controlled fissures in the Krishna-God-avari Basin (K-G Basin) of Godavari Triple Junction, occurring as a unique outcrop sandwiched between Cretaceous and Tertiary sediments along the east coast of India. Detailed geochemical studies have revealed that RTB are mid-Ti (1.74e1.92) to high-Ti (2.04e2.81) basalts with a distinct quartz tholeiitic parentage. MgO (6.2e13.12 wt.%), Mg# (29e50) and Zr (109e202 ppm) suggest that these basalts evolved by fractional crystallization during the ascent of the parent magma along deep-seated fractures. Mod-erate to high fractionation of HREE, as indicated by (Gd/Yb)N ratios (1.71e2.31) of RTB, suggest their generation through 3e5%melting of a Fe-rich mantle corresponding to the stability fields of spinel and garnet peridotite at depths of 60e100 km. Low K2O/P2O5 (0.26e1.26), high TiO2/P2O5 (6.74e16.79), La/Nb (0.89e1.45), Nb/Th>8 (8.35e13), negative anomalies at Rb reflect minimum contamination by granitic continental crust. (Nb/La)PM ratios (0.66e1.1) of RTB are attributed to endogenic contamination resulted through recycling of subducted oceanic slab into the mantle. Pronounced Ba enrichment with relative depletion in Rb indicates assimilation of Infra- and Inter-trappean sediments of estuarine to shallow marine character. Geochemical compositions such as Al2O3/TiO2 (3.88e6.83), medium to high TiO2 (1.74 e2.81 wt.%), positive Nb anomalies and LREE enrichment of these RTB attest to their mantle plume origin and indicate the generation of parent magma from a plume-related enriched mantle source with EM I signature. Ba/Th (46e247), Ba/La (3.96e28.51) and Th/Nb (0.08e0.13) ratios suggest that the source enrichment process was marked by recycling of subduction-processed oceanic crust and lithospheric components into the mantle. Zr/Hf (37e41) and Zr/Ba (0.51e3.24) indicate involvement of an astheno-spheric mantle source. The Rajahmundry basalts show affinity towards FOZO

  18. Glacial-interglacial water cycle, global monsoon and atmospheric methane changes

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Zhengtang; Wu, Haibin [Chinese Academy of Sciences, Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Beijing (China); Zhou, Xin [Chinese Academy of Sciences, Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Beijing (China); University of Science and Technology of China, School of Earth and Space Sciences and Institute of Polar Environment, Hefei (China)

    2012-09-15

    The causes of atmospheric methane (CH{sub 4}) changes are still a major contention, in particular with regards to the relative contributions of glacial-interglacial cycles, monsoons in both hemispheres and the late Holocene human intervention. Here, we explore the CH{sub 4} signals in the Antarctic EPICA Dome C and Vostok ice records using the methods of timeseries analyses and correlate them with insolation and geological records to address these issues. The results parse out three distinct groups of CH{sub 4} signals attributable to different drivers. The first group ({proportional_to}80% variance), well tracking the marine {delta}{sup 18}O record, is attributable to glacial-interglacial modulation on the global water cycle with the effects shared by wetlands at all latitudes, from monsoonal and non-monsoonal regions in both hemispheres. The second group ({proportional_to}15% variance), centered at the {proportional_to}10-kyr semi-precession frequency, is linkable with insolation-driven tropical monsoon changes in both hemispheres. The third group ({proportional_to}5% variance), marked by millennial frequencies, is seemingly related with the combined effect of ice-volume and bi-hemispheric insolation changes at the precession bands. These results indicate that bi-hemispheric monsoon changes have been a constant driver of atmospheric CH{sub 4}. This mechanism also partially explains the Holocene CH{sub 4} reversal since {proportional_to}5 kyr BP besides the human intervention. In the light of these results, we propose that global monsoon can be regarded as a system consisting of two main integrated components, one primarily driven by the oscillations of Inter-Tropical Convergence Zone (ITCZ) in response to the low-latitude summer insolation changes, anti-phase between the two hemispheres (i.e. the ITCZ monsoon component); and another modulated by the glacial-interglacial cycles, mostly synchronous at the global scale (i.e. the glacial-interglacial monsoon

  19. Relationship Between East Asian Winter Monsoon and Summer Monsoon

    Institute of Scientific and Technical Information of China (English)

    YAN Hongming; YANG Hui; YUAN Yuan; LI Chongyin

    2011-01-01

    Using National Centers for Environmental Prediction/National Centre for Atmospheric Research (NCEP/NCAR) reanalysis data and monthly Hadley Center sea surface temperature (SST) data,and selecting a representative East Asian winter monsoon (EAWM) index,this study investigated the relationship between EAWM and East Asian summer monsoon (EASM) using statistical analyses and numerical simulations.Some possible mechanisms regarding this relationship were also explored.Results indicate a close relationship between EAWM and EASM:a strong EAWM led to a strong EASM in the following summer,and a weak EAWM led to a weak EASM in the following summer.Anomalous EAWM has persistent impacts on the variation of SST in the tropical Indian Ocean and the South China Sea,and on the equatorial atmospheric thermal anomalies at both lower and upper levels.Through these impacts,the EAWM influences the land-sea thermal contrast in summer and the low-level atmospheric divergence and convergence over the Indo-Pacific region.It further affects the meridional monsoon circulation and other features of the EASM.Numerical simulations support the results of diagnostic analysis.The study provides useful information for predicting the EASM by analyzing the variations of preceding EAWM and tropical SST.

  20. Analysing ethnobotanical and fishery-related importance of mangroves of the East-Godavari Delta (Andhra Pradesh, India for conservation and management purposes

    Directory of Open Access Journals (Sweden)

    Ravishankar T

    2006-05-01

    Full Text Available Abstract Mangrove forests, though essentially common and wide-spread, are highly threatened. Local societies along with their knowledge about the mangrove also are endangered, while they are still underrepresented as scientific research topics. With the present study we document local utilization patterns, and perception of ecosystem change. We illustrate how information generated by ethnobiological research can be used to strengthen the management of the ecosystem. This study was conducted in the Godavari mangrove forest located in the East-Godavari District of the state Andhra Pradesh in India, where mangroves have been degrading due to over-exploitation, extensive development of aquaculture, and pollution from rural and urbanized areas (Kakinada. One hundred interviews were carried out among the fisherfolk population present in two mangrove zones in the study area, a wildlife sanctuary with strong conservation status and an adjacent zone. Results from the interviews indicated that Avicennia marina (Forsk. Vierh., a dominant species in the Godavari mangroves, is used most frequently as firewood and for construction. Multiple products of the mangrove included the bark of Ceriops decandra (Griff. Ding Hou to dye the fishing nets and improve their durability, the bark of Aegiceras corniculatum (L. Blanco to poison and catch fish, and the leaves of Avicennia spp. and Excoecaria agallocha L. as fodder for cattle. No medicinal uses of true mangrove species were reported, but there were a few traditional uses for mangrove associates. Utilization patterns varied in the two zones that we investigated, most likely due to differences in their ecology and legal status. The findings are discussed in relation with the demographic and socio-economic traits of the fisherfolk communities of the Godavari mangroves and indicate a clear dependency of their livelihood on the mangrove forest. Reported changes in the Godavari mangrove cover also differed in the two

  1. Analysing ethnobotanical and fishery-related importance of mangroves of the East-Godavari Delta (Andhra Pradesh, India) for conservation and management purposes.

    Science.gov (United States)

    Dahdouh-Guebas, F; Collin, S; Lo Seen, D; Rönnbäck, P; Depommier, D; Ravishankar, T; Koedam, N

    2006-05-08

    Mangrove forests, though essentially common and wide-spread, are highly threatened. Local societies along with their knowledge about the mangrove also are endangered, while they are still underrepresented as scientific research topics. With the present study we document local utilization patterns, and perception of ecosystem change. We illustrate how information generated by ethnobiological research can be used to strengthen the management of the ecosystem. This study was conducted in the Godavari mangrove forest located in the East-Godavari District of the state Andhra Pradesh in India, where mangroves have been degrading due to over-exploitation, extensive development of aquaculture, and pollution from rural and urbanized areas (Kakinada).One hundred interviews were carried out among the fisherfolk population present in two mangrove zones in the study area, a wildlife sanctuary with strong conservation status and an adjacent zone. Results from the interviews indicated that Avicennia marina (Forsk.) Vierh., a dominant species in the Godavari mangroves, is used most frequently as firewood and for construction. Multiple products of the mangrove included the bark of Ceriops decandra (Griff.) Ding Hou to dye the fishing nets and improve their durability, the bark of Aegiceras corniculatum (L.) Blanco to poison and catch fish, and the leaves of Avicennia spp. and Excoecaria agallocha L. as fodder for cattle. No medicinal uses of true mangrove species were reported, but there were a few traditional uses for mangrove associates. Utilization patterns varied in the two zones that we investigated, most likely due to differences in their ecology and legal status. The findings are discussed in relation with the demographic and socio-economic traits of the fisherfolk communities of the Godavari mangroves and indicate a clear dependency of their livelihood on the mangrove forest.Reported changes in the Godavari mangrove cover also differed in the two zones, with significantly

  2. Hydrography and circulation in the western Bay of Bengal during the northeast monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Shetye, S.R.; Gouveia, A.D.; Shankar, D.; Shenoi, S.S.C.; Vinayachandran, P.N.; Sundar, D.; Michael, G.S.; Nampoothiri, G.

    , the transport is 7.7 x 10 sup(6) m sup(3) s sup(-1) . Recent model studies lead us to conclude that the EICC during the northeast monsoon is driven by winds along the east coast of India and Ekman pumping in the interior bay. In the south, Ekman pumping over...

  3. Workshop on Monsoon Climate Systems: Toward Better Prediction of the Monsoon

    Energy Technology Data Exchange (ETDEWEB)

    Sperber, K R; Yasunari, T

    2005-12-20

    The Earth's monsoon systems are the life-blood of more than two-thirds of the world's population through the rainfall they provide to the mainly agrarian societies they influence. More than 60 experts gathered to assess the current understanding of monsoon variability and to highlight outstanding problems simulating the monsoon.

  4. Assessment of knowledge and practices on injection safety among service providers in east Godavari district of Andhra Pradesh

    Directory of Open Access Journals (Sweden)

    Sridevi Garapati

    2014-09-01

    Full Text Available Objectives: To assess the Knowledge and Practices among service providers regarding injection safety and its safe disposal in East Godavari District of Andhra Pradesh. Materials and Methods: Cross-Sectional study conducted in one year from March 2010 to February 2011 among health care providers at all levels that is Primary, Secondary and Tertiary levels of public sector selected randomly in the five revenue divisions of East Godavari District with sample size based on 4PQ/L2 formula found to be 300; Representing 30% doctors (90, 30% staff nurses (90, 30% MPHW (F (90 and 10% Lab-Technicians(30 and data is obtained by semi- structured questionnaire; Analyzed by using SPSS software version16.0.at p<0.05 significance level. Results: In the present study knowledge of various service providers was enquired into and practices were also observed in various aspects of injection safety. Knowledge on washing hands before giving injection was 45.6% but when it comes to practice it was observed only among 18.2%; Similarly knowledge on use of hub-cutter after giving injection was found to be 33.9% but when practice of using hub-cutter was observed, it was only 20.5%; Knowledge on safe disposal of used syringes was 53.8% but the practice was found to be poor (21.7%. Similarly Knowledge on use of color coded bags according to guidelines was 65.8% but when practice was observed it is poor (20.6%. All these differences were statistically significant with p<0.05.  Conclusion: In the present study Patient preference is the main indication for injection; Knowledge of universal precautions, use of needle destroyer after giving injection and correct method for final disposal of sharps was less; whereas Knowledge of complications of unsafe injections, diseases transmitted through needle stick injuries, importance of hepatitis B immunization and Post Exposure Prophylaxis was good. Unsafe practices like not washing hands, not wearing gloves, not cleaning the site of

  5. A reappraisal of polymetamorphism in the Eastern Ghats belt - A view from north of the Godavari rift

    Indian Academy of Sciences (India)

    A Bhattacharya; S Gupta

    2001-12-01

    Evidence collated from different parts of the Eastern Ghats belt north of the Godavari rift (barring the ``Western Charnockite Zone") indicates that this sector evolved through a series of compressive structures (1 to 3), with prolific migmatization in quartzofeldspathic and metapelitic gneisses synchronous with 1 shortening, as was the syn- 1 emplacement of profuse megacrystic K-feldspar-bearing granitoid bodies. Thereafter, melt productivity of the rocks (synchronous with 2 - 3 folding) sharply decreased. Mineral parageneses stable in the 1, 2 and 3 fabrics indicate persistence of granulite facies conditions. P-T estimates on orthopyroxene + garnet + plagioclase + quartz assemblages anchored to recrystallized mosaic that overgrow all penetrative fabric elements in mafic granulites, granitoids and quartzofeldspathic gneisses are in the range of 900°-950°C and P ≅ 8-9 kbar. This estimate is comparable to those retrieved from sapphirine-bearing paragenesis in Mg-Al metapelites that appear to be diachronous in relation to the fabric elements, and arguably disrupt the granoblastic mosaic. These facets in the northern sector of the orogenic belt are compatible with either a single cycle of tectonic events (i.e., 1, 2 and 3 in continuum), or temporally-separate thermo-tectonic events, with the peak of earlier metamorphism (pre- to syn-1) at lower temperature (in the granulite facies) in comparison to the record of high post-3-max values. It is suggested on the basis of the above evidence that the late Proterozoic/Pan-African granulites in the Eastern Ghats belt north of the Godavari rift, are unlikely to be reworked equivalents of any older granulitic crust, such as the ∼1.6 Ga granulites south of the rift. Instead, the temporally disparate sectors may represent different crustal segments with unconnected pre-amalgamation tectonic history. However, if the ∼1.6 Ga granulites of the Western Charnockite Zone continue northwards across the rift, as suggested by

  6. Transport pathways from the Asian monsoon anticyclone to the stratosphere

    Science.gov (United States)

    Garny, Hella; Randel, William

    2016-04-01

    The upper tropospheric Asian monsoon anticyclone emerges in response to persistent deep convection over India and southeast Asia in northern summer. The monsoon circulation is associated with rapid transport from the surface to the upper troposphere within convective updrafts, leading to tracer anomalies within the anticyclone. Possibly air is transported further into the stratosphere, but the exact pathways of air from the upper tropospheric anticyclone to the stratosphere are currently under debate. While air is thought to be confined to the anticyclone by its surrounding wind jets, large variability in the anticyclone results in shedding of air from the anticyclone to its surrounding, and possibly air might reach the extratropical lower stratosphere by isentropic mixing. On the other hand, positive vertical velocities in the anticyclone region suggests upward transport of air into the tropical lower stratosphere. In this study, we investigate transport pathways of air originating in the upper tropospheric Asian monsoon anticyclone based on isentropic and three-dimensional trajectories. Trajectories are driven by ERA-Interim reanalysis data, and three-dimensional results are based both on kinematic and diabatic transport calculations. Isentropic calculations show that air parcels are typically confined within the anticyclone for 10-20 days, and spread over the tropical belt within a month of their initialization. However, only few parcels (3 % at 360 K, 8 % at 380 K) reach the extratropical stratosphere by isentropic transport. When considering vertical transport we find that 31 % (48 %) of the trajectories reach the stratosphere within 60 days when using vertical velocities or diabatic heating rates to calculate vertical transport, respectively. In both cases, most parcels that reach the stratosphere are transported upward within the anticyclone and enter the stratosphere in the tropics, typically 10-20 days after their initialization at 360 K. This suggests

  7. Spacebased Observations of the Oceanic Responses to Monsoons in South China Sea and Arabian Sea

    Science.gov (United States)

    Xie, Xiao-Su; Liu, W. Timothy

    2000-01-01

    A large percentage of the world's population and their agrarian economy must endure the vagaries of the monsoons over the tropical oceans between Africa and the Philippines. We know very little about the oceanic responses to changes of the monsoon in the South China Sea (SCS), which is under the influence of the East Asian Monsoon System, and the Arabian Sea (AS), which is dominated by the Indian Monsoon System; oceanic observations are sparse in both regions. Data from spaceborne microwave scatterometers and radiometers have been used to estimate the two major atmospheric forcing, momentum flux and latent heat flux (LHF), which change with the monsoon winds. Spaceborne sensors also observed the surface signatures of the oceanic response: SST and sea level changes (SLC. Sufficient durations of these data have recently become available to allow the meaningful studies of the annual cycles and interannual anomalies. In SCS, the winter monsoon is strong and steady but the summer monsoon is weak and has large intraseasonal fluctuations. In AS, the summer monsoon is much stronger than the winter monsoon. Significant correlations between LHF and SST tendency, and between curl of wind stress and SLC are found in both oceans. In the north SCS, winds are strong and dry, LHF is high, and ocean cooling is also large in fall; LHF is low and the ocean warms up in spring. In AS, LHF and SST tendency have a semi annual period; LHF is high in summer when the wind is strong and in winter when the wind is dry. Along the coast of Oman, the strong summer southwest monsoon causes intense upwelling, low SST and LHF in summer; such wind-driven SST changes is not as obvious along the Vietnam coast because of the weaker summer monsoon. The negative correlation between curl of wind stress and SLC found in the central basins of both SCS and AS agrees with a simple Ekman pumping scenario. Cyclonic winds drive surface divergence and upwelling in the ocean; the rise of the thermocline causes

  8. Gas hydrate saturations estimated from fractured reservoir at Site NGHP-01-10, Krishna-Godavari Basin, India

    Science.gov (United States)

    Lee, M.W.; Collett, T.S.

    2009-01-01

    During the Indian National Gas Hydrate Program Expedition 01 (NGHP-Ol), one of the richest marine gas hydrate accumulations was discovered at Site NGHP-01-10 in the Krishna-Godavari Basin. The occurrence of concentrated gas hydrate at this site is primarily controlled by the presence of fractures. Assuming the resistivity of gas hydratebearing sediments is isotropic, th?? conventional Archie analysis using the logging while drilling resistivity log yields gas hydrate saturations greater than 50% (as high as ???80%) of the pore space for the depth interval between ???25 and ???160 m below seafloor. On the other hand, gas hydrate saturations estimated from pressure cores from nearby wells were less than ???26% of the pore space. Although intrasite variability may contribute to the difference, the primary cause of the saturation difference is attributed to the anisotropic nature of the reservoir due to gas hydrate in high-angle fractures. Archie's law can be used to estimate gas hydrate saturations in anisotropic reservoir, with additional information such as elastic velocities to constrain Archie cementation parameters m and the saturation exponent n. Theory indicates that m and n depend on the direction of the measurement relative to fracture orientation, as well as depending on gas hydrate saturation. By using higher values of m and n in the resistivity analysis for fractured reservoirs, the difference between saturation estimates is significantly reduced, although a sizable difference remains. To better understand the nature of fractured reservoirs, wireline P and S wave velocities were also incorporated into the analysis.

  9. Tropical stratospheric circulation and monsoon rainfall

    Science.gov (United States)

    Sikder, A. B.; Patwardhan, S. K.; Bhalme, H. N.

    1993-09-01

    Interannual variability of both SW monsoon (June September) and NE monsoon (October December) rainfall over subdivisions of Coastal Andhra Pradesh, Rayalaseema and Tamil Nadu have been examined in relation to monthly zonal wind anomaly for 10 hPa, 30 hPa and 50 hPa at Balboa (9°N, 80°W) for the 29 year period (1958 1986). Correlations of zonal wind anomalies to SW monsoon rainfall ( r=0.57, significant at 1% level) is highest with the longer lead time (August of the previous year) at 10 hPa level suggesting some predictive value for Coastal Andhra Pradesh. The probabilities estimated from the contingency table reveal non-occurrence of flood during easterly wind anomalies and near non-occurrence of drought during westerly anomalies for August of the previous year at 10 hPa which provides information for forecasting of performance of SW monsoon over Coastal Andhra Pradesh. However, NE monsoon has a weak relationship with zonal wind anomalies of 10 hPa, 30 hPa and 50 hPa for Coastal Andhra Pradesh, Rayalaseema and Tamil Nadu. Tracks of the SW monsoon storms and depressions in association with the stratospheric wind were also examined to couple with the fluctuations in SW monsoon rainfall. It is noted that easterly / westerly wind at 10 hPa, in some manner, suppresses / enhances monsoon storms and depressions activity affecting their tracks.

  10. Global monsoon in a geological perspective

    Institute of Scientific and Technical Information of China (English)

    WANG PinXian

    2009-01-01

    Monsoon is now considered as a global system rather than regional phenomena only. For over 300 years, monsoon has been viewed as a gigantic land-sea breeze, but now satellite and conventional observations support an alternative hypothesis which considers monsoon as a manifestation of sea-sonal migration of the intertropical convergence zone (ITCZ) and, hence, a climate system of the global scale. As a low-latitude climate system, monsoon exists over all continents but Antarctica, and through all the geological history at least since the Phenorozoic. The time is ripe for systematical studies of monsoon variations in space and time.As evidenced by the geological records, the global monsoon is controlled by the Wilson cycle on the tectonic time scale (106-108a). A "Mega-continent" produces "Mega-monsoon", and its breakdown leads to weakening of the monsoon Intensity. On the time scales of 104-105 a, the global monsoon displays the precessional cycles of~20 ka and eccentricity cycles of 100- and 400-ka, i.e. the orbital cycles. On the time scales of 103 a and below, the global monsoon intensity is modulated by solar cy-cles and other factors. The cyclicity of global monsoon represents one of the fundamental factors re-sponsible for variations in the Earth surface system as well as for the environmental changes of the human society. The 400-ka long eccentricity cycles of the global monsoon is likened to "heartbeat" of the Earth system, and the precession cycle of the global monsoon was responsible for the collapse of several Asian and African ancient cultures at~4000 years ago, whereas the Solar cycles led to the de-mise of the Maya civilization about a thousand years ago. Therefore, paleoclimatology should be fo-cused not only on the high-latitude processes centered at ice cap variations, but also on the low-latitude processes such as monsoons, as the latter are much more common in the geological history compared to the glaciations.

  11. Aerosol and monsoon climate interactions over Asia

    Science.gov (United States)

    Li, Zhanqing; Lau, W. K.-M.; Ramanathan, V.; Wu, G.; Ding, Y.; Manoj, M. G.; Liu, J.; Qian, Y.; Li, J.; Zhou, T.; Fan, J.; Rosenfeld, D.; Ming, Y.; Wang, Y.; Huang, J.; Wang, B.; Xu, X.; Lee, S.-S.; Cribb, M.; Zhang, F.; Yang, X.; Zhao, C.; Takemura, T.; Wang, K.; Xia, X.; Yin, Y.; Zhang, H.; Guo, J.; Zhai, P. M.; Sugimoto, N.; Babu, S. S.; Brasseur, G. P.

    2016-12-01

    The increasing severity of droughts/floods and worsening air quality from increasing aerosols in Asia monsoon regions are the two gravest threats facing over 60% of the world population living in Asian monsoon regions. These dual threats have fueled a large body of research in the last decade on the roles of aerosols in impacting Asian monsoon weather and climate. This paper provides a comprehensive review of studies on Asian aerosols, monsoons, and their interactions. The Asian monsoon region is a primary source of emissions of diverse species of aerosols from both anthropogenic and natural origins. The distributions of aerosol loading are strongly influenced by distinct weather and climatic regimes, which are, in turn, modulated by aerosol effects. On a continental scale, aerosols reduce surface insolation and weaken the land-ocean thermal contrast, thus inhibiting the development of monsoons. Locally, aerosol radiative effects alter the thermodynamic stability and convective potential of the lower atmosphere leading to reduced temperatures, increased atmospheric stability, and weakened wind and atmospheric circulations. The atmospheric thermodynamic state, which determines the formation of clouds, convection, and precipitation, may also be altered by aerosols serving as cloud condensation nuclei or ice nuclei. Absorbing aerosols such as black carbon and desert dust in Asian monsoon regions may also induce dynamical feedback processes, leading to a strengthening of the early monsoon and affecting the subsequent evolution of the monsoon. Many mechanisms have been put forth regarding how aerosols modulate the amplitude, frequency, intensity, and phase of different monsoon climate variables. A wide range of theoretical, observational, and modeling findings on the Asian monsoon, aerosols, and their interactions are synthesized. A new paradigm is proposed on investigating aerosol-monsoon interactions, in which natural aerosols such as desert dust, black carbon from

  12. Daily variations in pathogenic bacterial populations in a monsoon influenced tropical environment.

    Science.gov (United States)

    Khandeparker, Lidita; Anil, Arga Chandrashekar; Naik, Sneha D; Gaonkar, Chetan C

    2015-07-15

    Changing climatic conditions have influenced the monsoon pattern in recent years. Variations in bacterial population in one such tropical environment were observed everyday over two years and point out intra and inter annual changes driven by the intensity of rainfall. Vibrio spp. were abundant during the monsoon and so were faecal coliforms. Vibrio alginolyticus were negatively influenced by nitrate, whereas, silicate and rainfall positively influenced Vibrio parahaemolyticus numbers. It is also known that pathogenic bacteria are associated with the plankton. Changes in the abundance of plankton, which are governed mainly by environmental changes, could be responsible for variation in pathogenic bacterial abundance during monsoon, other than the land runoff due to precipitation and influx of fresh water.

  13. Geologic implications of gas hydrates in the offshore of India: Krishna-Godavari Basin, Mahanadi Basin, Andaman Sea, Kerala-Konkan Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Kumar, P.; Collett, T.S.; Boswell, R.; Cochran, J.R.; Lall, M.; Mazumdar, A.; Ramana, M.V.; Ramprasad, T.; Riedel, M.; Sain, K.; Sathe, A.V.; Vishwanath, K.; Yadav, U.S.

    stream_size 220180 stream_content_type text/plain stream_name Mar_Pet_Geol_58_29a.pdf.txt stream_source_info Mar_Pet_Geol_58_29a.pdf.txt Content-Encoding UTF-8 Content-Type text/plain; charset=UTF-8 1    Author version... to the present; and they now contain the Mahanadi and Godavari Rivers, respectively. Both rivers have a high sediment transport (Sastri et al., 1981; Biksham and Subrahmanyam, 1988) and both rivers have built substantial deltas so that sedimentation...

  14. Assessment of potential shale oil and tight sandstone gas resources of the Assam, Bombay, Cauvery, and Krishna-Godavari Provinces, India, 2013

    Science.gov (United States)

    Klett, Timothy R.; Schenk, Christopher J.; Wandrey, Craig J.; Brownfield, Michael E.; Charpentier, Ronald R.; Tennyson, Marilyn E.; Gautier, Donald L.

    2014-01-01

    Using a well performance-based geologic assessment methodology, the U.S. Geological Survey estimated a technically recoverable mean volume of 62 million barrels of oil in shale oil reservoirs, and more than 3,700 billion cubic feet of gas in tight sandstone gas reservoirs in the Bombay and Krishna-Godavari Provinces of India. The term “provinces” refer to geologically defined units assessed by the USGS for the purposes of this report and carries no political or diplomatic connotation. Shale oil and tight sandstone gas reservoirs were evaluated in the Assam and Cauvery Provinces, but these reservoirs were not quantitatively assessed.

  15. On the unstable ENSO-Western North Pacific Monsoon relation during the 20th Century

    Science.gov (United States)

    Vega Martín, Inmaculada; Gallego Puyol, David; Ribera Rodriguez, Pedro; Gómez Delgado, Francisco de Paula; Peña-Ortiz, Cristina

    2017-04-01

    The concept of the Western North Pacific Summer Monsoon (WNPSM) appeared for the first time in 1987. Unlike the Indian Summer Monsoon and the East Asian summer monsoon, the WNPSM is an oceanic monsoon driven essentially by the meridional gradient of sea surface temperature. Its circulation is characterized by a northwest-southeast oriented monsoon trough with intense precipitation and low-level southwesterlies and upper-tropospheric easterlies in the region [100°-130° E, 5°-15°N]. Although this monsoon is mainly oceanic, it modulates the precipitation of densely populated areas such as the Philippines. To date, the WNPSM has been quantified by the so-called Western North Pacific Monsoon Index (WNPMI), an index based on wind anomalies over large domains of the Western Pacific. The requirement of continuous observed wind over remote oceanic areas to compute the WNPMI has limited its availability to the 1949-2014 period. In this work we have extended the index by almost 100 years by using historical observations of wind direction taken aboard ships. Our Western North Pacific Directional Index (WNPDI), is defined as the sum of the persistence of the low-level westerly winds in [5°-15°N, 100°-130°E] and easterly winds in [20°-30°N, 110°-140°E]. The new WNPDI index is highly correlated to the existent WNPMI for the concurrent period (1948-2014). (r=+0.88, pCompetitividad through the project INCITE (CGL2013-44530-P, BES-2014-069733).

  16. Atmospheric circulation processes contributing to a multidecadal variation in reconstructed and modeled Indian monsoon precipitation

    Science.gov (United States)

    Wu, Qianru; Hu, Qi

    2015-01-01

    analysis of the recently reconstructed gridded May-September total precipitation in the Indian monsoon region for the past half millennium discloses significant variations at multidecadal timescales. Meanwhile, paleo-climate modeling outputs from the National Center for Atmospheric Research Community Climate System Model 4.0 show similar multidecadal variations in the monsoon precipitation. One of those variations at the frequency of 40-50 years per cycle is examined in this study. Major results show that this variation is a product of the processes in that the meridional gradient of the atmospheric enthalpy is strengthened by radiation loss in the high-latitude and polar region. Driven by this gradient and associated baroclinicity in the atmosphere, more heat/energy is generated in the tropical and subtropical (monsoon) region and transported poleward. This transport relaxes the meridional enthalpy gradient and, subsequently, the need for heat production in the monsoon region. The multidecadal timescale of these processes results from atmospheric circulation-radiation interactions and the inefficiency in generation of kinetic energy from the potential energy in the atmosphere to drive the eddies that transport heat poleward. This inefficiency creates a time delay between the meridional gradient of the enthalpy and the poleward transport. The monsoon precipitation variation lags that in the meridional gradient of enthalpy but leads that of the poleward heat transport. This phase relationship, and underlining chasing process by the transport of heat to the need for it driven by the meridional enthalpy gradient, sustains this multidecadal variation. This mechanism suggests that atmospheric circulation processes can contribute to multidecadal timescale variations. Interactions of these processes with other forcing, such as sea surface temperature or solar irradiance anomalies, can result in resonant or suppressed variations in the Indian monsoon precipitation.

  17. TIGERZ I: Aerosols, Monsoon and Synergism

    Science.gov (United States)

    Holben, B. N.; Tripathi, S. N.; Schafer, J. S.; Giles, D. M.; Eck, T. F.; Sinyuk, A.; Smirnov, A.; Krishnmoorthy, K.; Sorokin, M. G.; Newcomb, W. W.; Tran, A. K.; Sikka, D. R.; Goloub, P.; O'Neill, N. T.; Abboud, I.; Randles, C.; Niranjan, K.; Dumka, U. C.; Tiwari, S.; Devara, P. C.; Kumar, S.; Remer, L. A.; Kleidman, R.; Martins, J. V.; Kahn, R.

    2008-12-01

    The Indo-Gangetic Plain of northern India encompasses a vast complex of urban and rural landscapes, cultures that serve as anthropogenic sources of fine mode aerosols mixed with coarse mode particles transported from SW Asia. The summer monsoon and fall Himalayan snowmelt provide the agricultural productivity to sustain an extremely high population density whose affluence is increasing. Variations in the annual monsoon precipitation of 10% define drought, normal and a wet season; the net effects on the ecosystems and quality of life can be dramatic. Clearly investigation of anthropogenic and natural aerosol impacts on the monsoon, either through the onset, monsoon breaks or end points are a great concern to understand and ultimately mitigate. Many national and international field campaigns are being planned and conducted to study various aspects of the Asian monsoon and some coordinated under the Asian Monsoon Years (AMY) umbrella. A small program called TIGERZ conducted during the pre-monsoon of 2008 in North Central India can serve as a model for contributing significant resources to existing field programs while meeting immediate project goals. This poster will discuss preliminary results of the TIGERZ effort including ground-based measurements of aerosol properties in the I-G from AERONET and synergism with various Indian programs, satellite observations and aerosol modeling efforts.

  18. Acoustic reflections in the water column of Krishna-Godavari offshore basin, Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Sinha, S.K.; Dewangan, P.; Sain, K.

    for reflectivity modeling to generate the synthetic seismogram. 4 III. THEORY AND METHOD A. Estimation of soundspeed in sea water Soundspeed of seawater varies with temperature (T), salinity (S) and depth (D) (or, pressure). Several empirical relationships... Oceanography: A Derivative of the Encyclopedia of Ocean Sciences, edited by J. H. Steele, S. A. Thorpe and K. K. Turekian (Academic Press, London, 2008), pp. 432-441. 32 S. Sinha, "Data driven Q-compensation using continuous wavelet transform," in SEG...

  19. Remote sensing and GIS analysis for demarcation of coastal hazard line along the highly eroding Krishna-Godavari delta front

    Science.gov (United States)

    Kallepalli, Akhil; Kakani, Nageswara Rao; James, David B.

    2016-10-01

    Coastal regions, especially river deltas are highly resourceful and hence densely populated; but these extremely low-lying lands are vulnerable to rising sea levels due to global warming threatening the life and property in these regions. Recent IPCC (2013) predictions of 26-82cm global sea level rise are now considered conservative as subsequent investigations such as by Met Office, UK indicated a vertical rise of about 190cm, which would displace 10% of the world's population living within 10 meters above the sea level. Therefore, predictive models showing the hazard line are necessary for efficient coastal zone management. Remote sensing and GIS technologies form the mainstay of such predictive models on coastal retreat and inundation to future sea-level rise. This study is an attempt to estimate the varying trends along the Krishna-Godavari (K-G) delta region. Detailed maps showing various coastal landforms in the K-G delta region were prepared using the IRS-P6 LISS 3 images. The rate of shoreline shift during a 31-year period along different sectors of the 330km long K-G delta coast was estimated using Landsat-2 and IRS-P6 LISS 3 images between 1977 and 2008. With reference to a selected baseline from along an inland position, End Point Rate (EPR), Shoreline Change Envelope (SCE) and Net Shoreline Movement (NSM) were calculated, using a GIS-based Digital Shoreline Analysis System (DSAS). The results showed that the shoreline migrated landward up to a maximum distance of 3.13km resulting in a net loss of about 42.10km2 area during this 31-year period. Further, considering the nature of landforms and EPR, the future hazard line is predicted for the area, which also indicated a net erosion of about 57.68km2 along the K-G delta coast by 2050 AD.

  20. A hemispheric climatology of monsoon depressions

    Science.gov (United States)

    Hurley, J. V.; Boos, W.

    2012-12-01

    Monsoon depressions are large (1000-2000 km diameter) cyclonic low pressure systems having organized deep convection, best known for forming in the Bay of Bengal and migrating northwest over northern India in the monsoon trough. About 3 to 5 of these systems occur during each monsoon season, contributing about half of the Indian summer rainfall. Despite their importance as a precipitation source, their dynamics are poorly constrained. Furthermore, although they do occur elsewhere, such as around Australia and in the southern Indian Ocean, there does not exist a collective inventory of these systems outside of the Bay of Bengal region. Here we present a climatology of monsoon depressions produced from the ERA-Interim Reanalysis. Feature tracks are identified using an automated tracking algorithm (K. Hodges' TRACK code) applied to the 850 hPa relative vorticity field for local summer, 1989 to 2003. Using criteria based on relative vorticity and sea level pressure, cyclonic low pressure systems are separated into different intensity categories, one of which corresponds to the definition for monsoon depressions used by the India Meteorological Department. The resultant distribution of storms obtained for the Bay of Bengal region compares well with a previously compiled climatology of monsoon depressions that was limited to the region surrounding India. Having validated our ability to identify monsoon depressions in their classic genesis region near India, we then extend the methods to include the western Pacific, Australia, and the southern Indian Ocean. Track distributions and composite structures of monsoon depressions for these different regions will be presented.

  1. Clay mineralogical and geochemical proxies of the East Asian summer monsoon evolution in the South China Sea during Late Quaternary

    Science.gov (United States)

    Chen, Quan; Liu, Zhifei; Kissel, Catherine

    2017-01-01

    The East Asian summer monsoon controls the climatic regime of an extended region through temperature and precipitation changes. As the East Asian summer monsoon is primarily driven by the northern hemisphere summer insolation, such meteorological variables are expected to significantly change on the orbital timescale, influencing the composition of terrestrial sediments in terms of both mineralogy and geochemistry. Here we present clay mineralogy and major element composition of Core MD12-3432 retrieved from the northern South China Sea, and we investigate their relationship with the East Asian summer monsoon evolution over the last 400 ka. The variability of smectite/(illite + chlorite) ratio presents a predominant precession periodicity, synchronous with the northern hemisphere summer insolation changes and therefore with that of the East Asian summer monsoon. Variations in K2O/Al2O3 are characterized by eccentricity cycles, increasing during interglacials when the East Asian summer monsoon is enhanced. Based on the knowledge of sediment provenances, we suggest that these two proxies in the South China Sea are linked to the East Asian summer monsoon evolution with different mechanisms, which are (1) contemporaneous chemical weathering intensity in Luzon for smectite/(illite + chlorite) ratio and (2) river denudation intensity for K2O/Al2O3 ratio of bulk sediment. PMID:28176842

  2. Clay mineralogical and geochemical proxies of the East Asian summer monsoon evolution in the South China Sea during Late Quaternary.

    Science.gov (United States)

    Chen, Quan; Liu, Zhifei; Kissel, Catherine

    2017-02-08

    The East Asian summer monsoon controls the climatic regime of an extended region through temperature and precipitation changes. As the East Asian summer monsoon is primarily driven by the northern hemisphere summer insolation, such meteorological variables are expected to significantly change on the orbital timescale, influencing the composition of terrestrial sediments in terms of both mineralogy and geochemistry. Here we present clay mineralogy and major element composition of Core MD12-3432 retrieved from the northern South China Sea, and we investigate their relationship with the East Asian summer monsoon evolution over the last 400 ka. The variability of smectite/(illite + chlorite) ratio presents a predominant precession periodicity, synchronous with the northern hemisphere summer insolation changes and therefore with that of the East Asian summer monsoon. Variations in K2O/Al2O3 are characterized by eccentricity cycles, increasing during interglacials when the East Asian summer monsoon is enhanced. Based on the knowledge of sediment provenances, we suggest that these two proxies in the South China Sea are linked to the East Asian summer monsoon evolution with different mechanisms, which are (1) contemporaneous chemical weathering intensity in Luzon for smectite/(illite + chlorite) ratio and (2) river denudation intensity for K2O/Al2O3 ratio of bulk sediment.

  3. A new centennial index to study the Western North Pacific Monsoon decadal variability

    Science.gov (United States)

    Vega, Inmaculada; Gómez-Delgado, F. de Paula; Gallego, David; Ribera, Pedro; Peña-Ortiz, Cristina; García-Herrera, Ricardo

    2016-04-01

    The concept of the Western North Pacific Summer Monsoon (WNPSM) appeared for the first time in 1987. It is, unlike the Indian Summer Monsoon (ISM) and the East Asian summer monsoon (EASM), an oceanic monsoon mostly driven by the meridional gradient of sea surface temperature. Its circulation is characterized by a northwest-southeast oriented monsoon trough with intense precipitation and low-level southwesterlies and upper-tropospheric easterlies in the region [100°-130° E, 5°-15°N]. Up to now, the primary index to characterize the WNPSM has been the Western North Pacific Monsoon Index (WNPMI) which covers the 1949-2013 period. The original WNPMI was defined as the difference of 850-hPa westerlies between two regions: D1 [5°-15°N, 100°-130°E] and D2 [20°-30°N, 110°-140°E]. Both domains are included in the main historical ship routes circumnavigating Asia for hundreds of years. Many of the logbooks of these ships have been preserved in historical archives and they usually contain daily observations of wind force and direction. Therefore, it has been possible to compute a new index of instrumental character, which reconstructs the WNPSM back to the middle of the 19th Century, by using solely historical wind direction records preserved in logbooks. We define the monthly Western North Pacific Directional Index (WNPDI) as the sum of the persistence of the low-level westerly winds in D1 and easterly winds in D2. The advantages of this new index are its nature (instrumental) and its length (1849-2013), which is 100 years longer than the WNPMI (which was based on reanalysis data). Our WNPDI shows a high correlation (r=+0.87, pCompetitividad through the project INCITE (CGL2013-44530-P, BES-2014-069733).

  4. From monsoon to marine productivity in the Arabian Sea: insights from glacial and interglacial climates

    Science.gov (United States)

    Le Mézo, Priscilla; Beaufort, Luc; Bopp, Laurent; Braconnot, Pascale; Kageyama, Masa

    2017-07-01

    The current-climate Indian monsoon is known to boost biological productivity in the Arabian Sea. This paradigm has been extensively used to reconstruct past monsoon variability from palaeo-proxies indicative of changes in surface productivity. Here, we test this paradigm by simulating changes in marine primary productivity for eight contrasted climates from the last glacial-interglacial cycle. We show that there is no straightforward correlation between boreal summer productivity of the Arabian Sea and summer monsoon strength across the different simulated climates. Locally, productivity is fuelled by nutrient supply driven by Ekman dynamics. Upward transport of nutrients is modulated by a combination of alongshore wind stress intensity, which drives coastal upwelling, and by a positive wind stress curl to the west of the jet axis resulting in upward Ekman pumping. To the east of the jet axis there is however a strong downward Ekman pumping due to a negative wind stress curl. Consequently, changes in coastal alongshore stress and/or curl depend on both the jet intensity and position. The jet position is constrained by the Indian summer monsoon pattern, which in turn is influenced by the astronomical parameters and the ice sheet cover. The astronomical parameters are indeed shown to impact wind stress intensity in the Arabian Sea through large-scale changes in the meridional gradient of upper-tropospheric temperature. However, both the astronomical parameters and the ice sheets affect the pattern of wind stress curl through the position of the sea level depression barycentre over the monsoon region (20-150° W, 30° S-60° N). The combined changes in monsoon intensity and pattern lead to some higher glacial productivity during the summer season, in agreement with some palaeo-productivity reconstructions.

  5. Characteristics of monsoon low level jet (MLLJ) as an index of monsoon activity

    Indian Academy of Sciences (India)

    N V Sam; K P R Vittal Murty

    2002-12-01

    Temperature and wind data are used to describe variation in the strength of the Monsoon Low Level Jet (MLLJ) from an active phase of the monsoon to a break phase. Also estimated are the characteristics of turbulence above and below MLLJ.

  6. Aerosol and monsoon climate interactions over Asia: AEROSOL AND MONSOON CLIMATE INTERACTIONS

    Energy Technology Data Exchange (ETDEWEB)

    Li, Zhanqing [State Key Laboratory of Earth Surface Processes and Resource Ecology and College of Global Change and Earth System Science, Beijing Normal University, Beijing China; Department of Atmospheric and Oceanic Science and ESSIC, University of Maryland, College Park Maryland USA; Lau, W. K. -M. [Department of Atmospheric and Oceanic Science and ESSIC, University of Maryland, College Park Maryland USA; Ramanathan, V. [Department of Atmospheric and Climate Sciences, University of California, San Diego California USA; Wu, G. [Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing China; Ding, Y. [National Climate Center, China Meteorological Administration, Beijing China; Manoj, M. G. [Department of Atmospheric and Oceanic Science and ESSIC, University of Maryland, College Park Maryland USA; Liu, J. [Department of Atmospheric and Oceanic Science and ESSIC, University of Maryland, College Park Maryland USA; Qian, Y. [Pacific Northwest National Laboratory, Richland Washington USA; Li, J. [State Key Laboratory of Earth Surface Processes and Resource Ecology and College of Global Change and Earth System Science, Beijing Normal University, Beijing China; Zhou, T. [Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing China; Fan, J. [Pacific Northwest National Laboratory, Richland Washington USA; Rosenfeld, D. [Institute of Earth Sciences, Hebrew University, Jerusalem Israel; Ming, Y. [Geophysical Fluid Dynamic Laboratory, NOAA, Princeton New Jersey USA; Wang, Y. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena California USA; Huang, J. [College of Atmospheric Sciences, Lanzhou University, Lanzhou China; Wang, B. [Department of Atmospheric Sciences, University of Hawaii, Honolulu Hawaii USA; School of Atmospheric Physics, Nanjing University of Information Science and Technology, Nanjing China; Xu, X. [Chinese Academy of Meteorological Sciences, Beijing China; Lee, S. -S. [Department of Atmospheric and Oceanic Science and ESSIC, University of Maryland, College Park Maryland USA; Cribb, M. [Department of Atmospheric and Oceanic Science and ESSIC, University of Maryland, College Park Maryland USA; Zhang, F. [State Key Laboratory of Earth Surface Processes and Resource Ecology and College of Global Change and Earth System Science, Beijing Normal University, Beijing China; Yang, X. [State Key Laboratory of Earth Surface Processes and Resource Ecology and College of Global Change and Earth System Science, Beijing Normal University, Beijing China; Zhao, C. [State Key Laboratory of Earth Surface Processes and Resource Ecology and College of Global Change and Earth System Science, Beijing Normal University, Beijing China; Takemura, T. [Research Institute for Applied Mechanics, Kyushu University, Fukuoka Japan; Wang, K. [State Key Laboratory of Earth Surface Processes and Resource Ecology and College of Global Change and Earth System Science, Beijing Normal University, Beijing China; Xia, X. [Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing China; Yin, Y. [School of Atmospheric Physics, Nanjing University of Information Science and Technology, Nanjing China; Zhang, H. [National Climate Center, China Meteorological Administration, Beijing China; Guo, J. [Chinese Academy of Meteorological Sciences, Beijing China; Zhai, P. M. [Chinese Academy of Meteorological Sciences, Beijing China; Sugimoto, N. [National Institute for Environmental Studies, Tsukuba Japan; Babu, S. S. [Space Physics Laboratory, Vikram Sarabhai Space Centre, Thiruvananthapuram India; Brasseur, G. P. [Max Planck Institute for Meteorology, Hamburg Germany

    2016-11-15

    Asian monsoons and aerosols have been studied extensively which are intertwined in influencing the climate of Asia. This paper provides a comprehensive review of ample studies on Asian aerosol, monsoon and their interactions. The region is the primary source of aerosol emissions of varies species, influenced by distinct weather and climatic regimes. On continental scale, aerosols reduce surface insolation and weaken the land-ocean thermal contrast, thus inhibiting the development of monsoons. Locally, aerosol radiative effects alter the thermodynamic stability and convective potential of the lower atmosphere leading to reduced temperatures, increased atmospheric stability, and weakened wind and atmospheric circulation. The atmospheric thermodynamic state may also be altered by the aerosol serving as cloud condensation nuclei or ice nuclei. Many mechanisms have been put forth regarding how aerosols modulate the amplitude, frequency, intensity, and phase of numerous monsoon climate variables. A wide range of theoretical, observational, and modeling findings on the Asian monsoon, aerosols, and their interactions are synthesized. A new paradigm is proposed on investigating aerosol-monsoon interactions, in which natural aerosols such as desert dust, black carbon from biomass burning, and biogenic aerosols from vegetation are considered integral components of an intrinsic aerosol-monsoon climate system, subject to external forcings of global warming, anthropogenic aerosols, and land use and change. Future research on aerosol-monsoon interactions calls for an integrated approach and international collaborations based on long-term sustained observations, process measurements, and improved models, as well as using observations to constrain model simulations and projections.

  7. The First Pan-WCRP Workshop on Monsoon Climate Systems: Toward Better Prediction of the Monsoons

    Energy Technology Data Exchange (ETDEWEB)

    Sperber, K R; Yasunari, T

    2005-07-27

    In 2004 the Joint Scientific Committee (JSC) that provides scientific guidance to the World Climate Research Programme (WCRP) requested an assessment of (1) WCRP monsoon related activities and (2) the range of available observations and analyses in monsoon regions. The purpose of the assessment was to (a) define the essential elements of a pan-WCRP monsoon modeling strategy, (b) identify the procedures for producing this strategy, and (c) promote improvements in monsoon observations and analyses with a view toward their adequacy, and addressing any undue redundancy or duplication. As such, the WCRP sponsored the ''1st Pan-WCRP Workshop on Monsoon Climate Systems: Toward Better Prediction of the Monsoons'' at the University of California, Irvine, CA, USA from 15-17 June 2005. Experts from the two WCRP programs directly relevant to monsoon studies, the Climate Variability and Predictability Programme (CLIVAR) and the Global Energy and Water Cycle Experiment (GEWEX), gathered to assess the current understanding of the fundamental physical processes governing monsoon variability and to highlight outstanding problems in simulating the monsoon that can be tackled through enhanced cooperation between CLIVAR and GEWEX. The agenda with links to the presentations can be found at: http://www.clivar.org/organization/aamon/WCRPmonsoonWS/agenda.htm. Scientific motivation for a joint CLIVAR-GEWEX approach to investigating monsoons includes the potential for improved medium-range to seasonal prediction through better simulation of intraseasonal (30-60 day) oscillations (ISO's). ISO's are important for the onset of monsoons, as well as the development of active and break periods of rainfall during the monsoon season. Foreknowledge of the active and break phases of the monsoon is important for crop selection, the determination of planting times and mitigation of potential flooding and short-term drought. With a few exceptions simulations of ISO are

  8. The Joint Aerosol-Monsoon Experiment: A New Challenge to Monsoon Climate Research

    Science.gov (United States)

    Lau, William K. M.

    2008-01-01

    Aerosol and monsoon related droughts and floods are two of the most serious environmental hazards confronting more than 60% of the population of the world living in the Asian monsoon countries. In recent years, thanks to improved satellite and in-situ observations, and better models, great strides have been made in aerosol, and monsoon research respectively. There is now a growing body of evidence suggesting that interaction of aerosol forcing with water cycle dynamics in monsoon regions may substantially alter the redistribution of energy at the earth surface and in the atmosphere, and therefore significantly impact monsoon rainfall variability and long term trends. In this talk, I will describe issues related to societal needs, scientific background, and challenges in studies of aerosol-water cycle interaction in Asian monsoon regions. As a first step towards addressing these issues, the authors call for an integrated observation and modeling research approach aimed at the interactions between aerosol chemistry and radiative effects and monsoon dynamics of the coupled ocean-atmosphere-land system. A Joint Aerosol-Monsoon Experiment (JAMEX) is proposed for 2007-2011, with an enhanced observation period during 2008-09, encompassing diverse arrays of observations from surface, aircraft, unmanned aerial vehicles, and satellites of physical and chemical properties of aerosols, long range aerosol transport as well as meteorological and oceanographic parameters in the Indo-Pacific Asian monsoon region. JAMEX will leverage on coordination among many ongoing and planned national programs on aerosols and monsoon research in China, India, Japan, Nepal, Italy, US, as well as international research programs of the World Climate Research Program (WCRP) and the World Meteorological Organization (WMO).

  9. Late Permian Palynology and depositional environment of Chintalapudi sub basin, Pranhita-Godavari basin, Andhra Pradesh, India

    Science.gov (United States)

    Jha, Neerja; Pauline Sabina, K.; Aggarwal, Neha; Mahesh, S.

    2014-01-01

    The present study deals with the palynological dating, correlation and depositional setting of the sediments from bore cores MGP-11 and MGP-4 from Gauridevipet area of Chintalapudi sub-basin of Godavari master basin, south India. On the basis of palynological studies, three palynoassemblages have been identified, one in bore core MGP-11 a Faunipollenites (=Protohaploxypinus) and Striasulcites assemblage and two in bore core MGP-4; one is characterized by the dominance of striate bisaccates and Densipollenites and the other by Striatopodocarpites and Cresentipollenites palynoassemblages. The other stratigraphically significant taxa include Guttulapollenites hannonicus, Lunatisporites noviaulensis, Lunatisporites pellucidus, Densoisporites contactus, Chordasporites australiensis, Goubinispora spp., Lundbladispora microconata, Lundbladispora raniganjensis and Klausipollenites schaubergeri. The recovered taxa suggest a Late Permian, Lopingian age for these rocks. This interpretation is based on the correlation of the assemblages with similar assemblages from previous Gondwana studies chiefly Densipollenites magnicorpus Zone of Damodar Basin, India and Late Permian palynoassemblages from Africa, Antarctica, Australia and South America. On the basis of palaeobotanical affinity of the identified microflora it has been inferred that the peat forming plant community was composed mainly of gymnosperm pollen attributable to glossopterids, that includes striate and non-striate bisaccates and paucity of cordaites which includes monosaccates. Spores are subordinate and are derived from lycopsids (Lundbladispora, Densoisporites), sphenopsids (Latosporites) and filicopsids (Horriditriletes, Lophotriletes, Verrucosisporites, Osmundacidites, Leiotriletes, Callumispora, Brevitriletes and Microbaculispora) occurring in variable proportions. The dominance of subarborescent/arborescent vegetation suggests a development in a forest swamp probably in a small distant marginal part of the

  10. Potential of collocated radiometer and wind profiler observations for monsoon studies

    Science.gov (United States)

    Balaji, B.; Prabha, Thara V.; Jaya Rao, Y.; Kiran, T.; Dinesh, G.; Chakravarty, Kaustav; Sonbawne, S. M.; Rajeevan, M.

    2017-09-01

    Collocated observations from microwave radiometer and wind profiler are used in a pilot study during the monsoon period to derive information on the thermodynamics and winds and association with rainfall characteristics. These instruments were operated throughout the monsoon season of 2015. Continuous vertical profiles of winds, temperature and humidity show significant promise for understanding the low-level jet, its periodicity and its association with moisture transport, clouds and precipitation embedded within the monsoon large-scale convection. Observations showed mutually beneficial in explaining variability that are part of the low frequency oscillations and the diurnal variability during monsoon. These observations highlight the importance of locally driven convective systems, in the presence of weak moisture transport over the area. The episodic moisture convergence showed a periodicity of 9 days which matches with the subsequent convection and precipitation and thermodynamic regimes. Inferences from the diurnal cycle of moisture transport and the convective activity, relationship with the low-level jet characteristics and thermodynamics are also illustrated.

  11. Monsoon signatures in recent corals from the Laccadive Islands

    Digital Repository Service at National Institute of Oceanography (India)

    Naqvi, S.A.S.

    have reduced water transparency, thereby curtailing the growth rates. Scanning electron microscopy clearly showed the presence of lithogenic and biogenic material in the monsoonal bands and their absence in the non-monsoonal bands. This indicates...

  12. Thrusts and Prospects on Understanding and Predicting Asian Monsoon Climate

    Institute of Scientific and Technical Information of China (English)

    WANG Bin

    2008-01-01

    Development of monsoon climate prediction through integrated research efforts to improve our understanding of monsoon variability and predictability is a primary goal of the Asian Monsoon Years (2007-2011) and International Monsoon Study under the leadership of the World Climate Research Programme.The present paper reviews recent progress in Asian monsoon research focusing on (1) understanding and modeling of the monsoon variability, (2) determining the sources and limits of predictability, and (3) assessing the current status of climate prediction, with emphasis on the weekly to interannual time scales. Particular attention is paid to identify scientific issues and thrust areas, as well as potential directions to move forward in an attempt to stimulate future research to advance our understanding of monsoon climate dynamics and improve our capability to forecast Asian monsoon climate variation.

  13. Reappraisal of Asian Summer Monsoon Indices and the Long-Term Variation of Monsoon

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The Webster and Yang monsoon index (WYI)-the zonal wind shear between 850 and 200 hPa was calculated and modified on the basis of NCEP/NCAR reanalysis data. After analyzing the circulation and divergence fields of 150-100 and 200 hPa, however, we found that the 200-hPa level could not reflect the real change of the upper-tropospheric circulation of Asian summer monsoon, especially the characteristics and variation of the tropical easterly jet which is the most important feature of the upper-tropospheric circulation. The zonal wind shear U850-U(150+100) is much larger than U850-U200, and thus it can reflect the strength of monsoon more appropriately. In addition, divergence is the largest at 150 hPa rather than 200 hPa, so 150 hPa in the upper-troposphere can reflect the coupling of the monsoon system. Therefore,WYI is redefined as DHI, i.e., IDH=U*850 - U*(150+100), which is able to characterize the variability of not only the intensity of the center of zonal wind shear in Asia, but also the monsoon system in the upper and lower troposphere. DHI is superior to WYI in featuring the long-term variation of Asian summer monsoon as it indicates there is obvious interdecadal variation in the Asian summer monsoon and the climate abrupt change occurred in 1980. The Asian summer monsoon was stronger before 1980 and it weakened after then due to the weakening of the easterly in the layer of 150-100 hPa, while easterly at 200 hPa did not weaken significantly. After the climate jump year in general, easterly in the upper troposphere weakened in Asia, indicating the weakening of summer monsoon; the land-sea pressure difference and thermal difference reduced, resulting in the weakening of monsoon; the corresponding upper divergence as well as the water vapor transport decreased in Indian Peninsula, central Indo-China Peninsula, North China, and Northeast China, indicating the weakening of summer monsoon as well. The difference between NCEP/NCAR and ERA-40 reanalysis data in

  14. On breaks of the Indian monsoon

    Indian Academy of Sciences (India)

    Sulochana Gadgil; P V Joseph

    2003-12-01

    For over a century, the term break has been used for spells in which the rainfall over the Indian monsoon zone is interrupted. The phenomenon of `break monsoon' is of great interest because long intense breaks are often associated with poor monsoon seasons. Such breaks have distinct circulation characteristics (heat trough type circulation) and have a large impact on rainfed agriculture.Although interruption of the monsoon rainfall is considered to be the most important feature of the break monsoon, traditionally breaks have been identified on the basis of the surface pressure and wind patterns over the Indian region. We have defined breaks (and active spells) on the basis of rainfall over the monsoon zone. The rainfall criteria are chosen so as to ensure a large overlap with the traditional breaks documented by Ramamurthy (1969) and De et al (1998). We have identified these rainbreaks for 1901-89. We have also identified active spells on the basis of rainfall over the Indian monsoon zone. We have shown that the all-India summer monsoon rainfall is significantly negatively correlated with the number of rainbreak days (correlation coefficient −0.56) and significantly positively correlated with the number of active days (correlation coefficient 0.47).Thus the interannual variation of the all-India summer monsoon rainfall is shown to be related to the number of days of rainbreaks and active spells identified here. There have been several studies of breaks (and also active spells in several cases) identified on the basis of different criteria over regions differing in spatial scales (e.g., Webster et al 1998; Krishnan et al 2000; Goswami and Mohan 2000; and Annamalai and Slingo 2001). We find that there is considerable overlap between the rainbreaks we have identified and breaks based on the traditional definition. There is some overlap with the breaks identified by Krishnan et al (2000) but little overlap with breaks identified by Webster et al (1998). Further

  15. Siliceous microplankton fluxes and seasonal variations in the central South China Sea during 1993-1995:monsoon climate and El Ni(n)o responses

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Seasonal variations of radiolarian and diatom fluxes in the central South China Sea during 1993-1995 were overwhelmingly controlled by monsoon climate. Radiolarian and diatom increased obviously during the Northeast (from November to February) and Southwest (from June to September) monsoons and decreased during the periods between the monsoons. The change of circulation driven by the monsoons improved water exchange in the different areas that brought rich nutrient materials for the surface microplankton, thereby enhancing radiolarian and diatom fluxes. Variation of radiolarian flux coincided with organic carbon flux, surface primary and export productivities. High radiolarian flux corresponded to high surface primary productivity. Radiolarian and diatom fluxes raised abnormally during 1994-1995 could be attributed to the El Ni(n)o event during the period.

  16. Atmospheric processes sustaining a multidecadal variation in reconstructed and model-simulated Indian monsoon precipitation during the past half millennium

    Science.gov (United States)

    Wu, Qianru

    Analyses of recently reconstructed and model-simulated Indian May-September precipitation disclose a statistically significant multidecadal variation at the frequency of 40-50 year per cycle during the last half millennium. To understand the mechanism of this variation, we examined the energy and dynamic processes in the atmosphere, and the potential forcings from the sea surface temperature (SST) variations around the globe. Comparisons of paleo-SST and the paleo-precipitation simulations suggest that the SST is not a significant forcing of the multidecadal variation found in the Indian monsoon precipitation. Instead, analyses suggest that atmospheric processes characterized by phase differences between the meridional enthalpy gradient and poleward eddy enthalpy transport are important to sustain this variation. In this phase relationship, the meridional enthalpy gradient is strengthened by radiative loss in high latitudes. Driven by this enlarged gradient and associated changes in baroclinicity in the mid-latitude atmosphere, more energy is generated in the tropical and subtropical (monsoon) regions and transported poleward. The monsoon is strengthened to allow more energy being transported poleward. The increased enthalpy transport, in turn, weakens the meridional enthalpy gradient and, subsequently, softens the demand for energy production in the monsoon region. The monsoon weakens and the transport decreases. The variation in monsoon precipitation lags that in the meridional enthalpy gradient, but leads that in the poleward heat transport. This phase relationship and underlining chasing process by the heat transport to the gradient sustain this variation at the multidecadal timescale. This mechanism suggests that atmospheric circulation processes can contribute to multidecadal timescale variations in the Indian monsoon precipitation.

  17. Monsoonal Variations of Supraglacial Lakes, Langtang Khola, Nepal

    Science.gov (United States)

    Miles, E. S.; Willis, I. C.; Arnold, N. S.; Pellicciotti, F.

    2013-12-01

    lakes can have a strong effect on the glacier's annual mass balance and the magnitude of these processes needs to be examined at the local and glacier scales. This research examines changes in supraglacial lake cover and structure across the 2013 monsoon season on two glaciers in the 400km2 Langtang Khola basin of Nepal. Photography of the glacier surface reveals a pattern of basin filling and overtopping preceding monsoonal precipitation inputs, likely driven by high-altitude snowmelt. During the monsoon, repeat structure-from-motion photogrammetry is combined with dGPS surveys to examine changes in lake and ice-cliff geometry, while pressure transducers are used to observe water levels and volumes for selected lakes. Finally, Landsat TM and ETM+ data have been analyzed to assess the seasonality and permanence of the larger lake features. Further work will address remaining challenges in modeling supraglacial lake development and glacier-scale effects including the role of porous flow in the debris layer, the structure and connectivity of the sub-, en-, and supra-glacial hydrologic system, and the initiation of lake drainage events.

  18. Dynamics of Tropical Waves and Monsoons.

    Science.gov (United States)

    1981-04-01

    large-scale rainband in the Baum season. J Vet’,’,r 1o,. large-scale baroclinic forcing. Japon . 52. 448-451. -72 953 MONTHLY % EATHInR REVIEV% V L l 08...monsoon circulation large orographic structures such as the Himalavas. tan importance emanating from the social -economi- and 4) the perturbation of

  19. Warm Indian Ocean, Weak Asian Monsoon

    Science.gov (United States)

    Koll Roxy, Mathew; Ritika, Kapoor; Terray, Pascal; Murtugudde, Raghu; Ashok, Karumuri; Nath Goswami, Buphendra

    2015-04-01

    There are large uncertainties looming over the status and fate of the South Asian monsoon in a changing climate. Observations and climate models have suggested that anthropogenic warming in the past century has increased the moisture availability and the land-sea thermal contrast in the tropics, favoring an increase in monsoon rainfall. In contrast, we notice that South Asian subcontinent experienced a relatively subdued warming during this period. At the same time, the tropical Indian Ocean experienced a nearly monotonic warming, at a rate faster than the other tropical oceans. Using long-term observations and coupled model experiments, we suggest that the enhanced Indian Ocean warming along with the suppressed warming of the subcontinent weaken the land-sea thermal contrast throughout the troposphere, dampen the monsoon Hadley circulation, and reduce the rainfall over South Asia. As a result, the summer monsoon rainfall during 1901-2012 shows a significant weakening trend over South Asia, extending from Pakistan through central India to Bangladesh.

  20. Impact of the Desert dust on the summer monsoon system over Southwestern North America

    Directory of Open Access Journals (Sweden)

    C. Zhao

    2012-04-01

    Full Text Available The radiative forcing of dust emitted from the Southwest United States (US deserts and its impact on monsoon circulation and precipitation over the North America monsoon (NAM region are simulated using a coupled meteorology and aerosol/chemistry model (WRF-Chem for 15 years (1995–2009. During the monsoon season, dust has a cooling effect (−0.90 W m−2 at the surface, a warming effect (0.40 W m−2 in the atmosphere, and a negative top-of-the-atmosphere (TOA forcing (−0.50 W m−2 over the deserts on 24-h average. Most of the dust emitted from the deserts concentrates below 800 hPa and accumulates over the western slope of the Rocky Mountains and Mexican Plateau. The absorption of shortwave radiation by dust heats the lower atmosphere by up to 0.5 K day−1 over the western slope of the Mountains. Model sensitivity simulations with and without dust for 15 summers (June-July-August show that dust heating of the lower atmosphere over the deserts strengthens the low-level southerly moisture fluxes on both sides of the Sierra Madre Occidental. It also results in an eastward migration of NAM-driven moisture convergence over the western slope of the Mountains. These monsoonal circulation changes lead to a statistically significant increase of precipitation by up to ~40 % over the eastern slope of the Mountains (Arizona-New~Mexico-Texas regions. This study highlights the interaction between dust and the NAM system and motivates further investigation of possible dust feedback on monsoon precipitation under climate change and the mega-drought conditions projected for the future.

  1. Past dynamics of the Australian monsoon: precession, phase and links to the global monsoon concept

    Science.gov (United States)

    Beaufort, L.; van der Kaars, S.; Bassinot, F. C.; Moron, V.

    2010-10-01

    Past variations in the dynamics of the Australian monsoon have been estimated from multi-proxy analysis of a core retrieved in the Eastern Banda Sea. Records of coccolith and pollen assemblages, spanning the last 150 000 years, allow reconstruction of past primary production in the Banda Sea, summer moisture availability, and the length of the dry season in northern Australia and southeastern Indonesia. The amount of moisture available during the summer monsoon follows typical glacial/interglacial dynamics with a broad asymmetrical 100-kyr cycle. Primary production and length of the dry season appear to be closely related, given that they follow the precessional cycle with the same phase. This indicates their independence from ice-volume variations. The present inter-annual variability of both parameters is related to El Niño Southern Oscillation (ENSO), which modulates the Australian Winter Monsoon (AWM). The precessional pattern observed in the past dynamics of the AWM is found in ENSO and monsoon records of other regions. A marked shift in the monsoon intensity occurring during the mid Holocene during a period of constant ice volume, suggests that low latitude climatic variation precedes increases in global ice volume. This precessional pattern suggests that a common forcing mechanism underlies low latitude climate dynamics, acting specifically and synchronously on the different monsoon systems.

  2. Past dynamics of the Australian monsoon: precession, phase and links to the global monsoon

    Science.gov (United States)

    Beaufort, L.; van der Kaars, S.; Bassinot, F. C.; Moron, V.

    2010-06-01

    Past variations in the dynamics of the Australian monsoon have been estimated from multi-proxy analysis of a core retrieved in the Eastern Banda Sea. Records of coccolith and pollen assemblages, spanning the last 150,000 years, allow reconstruction of past primary production in the Banda Sea, summer moisture availability, and the length of the dry season in Northern Australia and Southeastern Indonesia. The amount of moisture available during the summer monsoon follows typical glacial/interglacial dynamics with a broad asymmetrical 100-kyr cycle. Primary production and length of the dry season appear to be closely related, given that they follow the precessional cycle with the same phase (August insolation). This indicates their independence from ice-volume variations. The present inter-annual variability of both parameters is related to El Niño Southern Oscillation (ENSO), which modulates the Australian Winter Monsoon (AWM). The precessional pattern observed in the past dynamics of the AWM is found in ENSO and monsoon records of other regions. A marked shift in the monsoon intensity occurring during the mid Holocene during a period of constant ice volume, suggest that low latitude climatic variation precedes global ice volume. This precessional pattern suggests that a common forcing mechanism underlies low latitude climate dynamics, acting specifically and synchronically on the different monsoon systems.

  3. Low-frequency variations in primary production in the Oman upwelling zone associated with monsoon winds

    Institute of Scientific and Technical Information of China (English)

    LIAO Xiaomei; ZHAN Haigang; WEI Xing

    2012-01-01

    Thirteen-year satellite-derived data are used to investigate the temporal variability of net primaryproduction (NPP) in the Oman upwelling zone and its potential forcing mechanisms.The NPP in the Oman upwelling zone is characterized by an abnormal decrease during El Ni(n)o events.Such an NPP decrease may be related to El Ni(n)o-driven anomalous summertime weak wind.During the summer following El Ni(n)o,the anomalous northeasterly wind forced by southwest Indian Ocean warming weakens the southwest monsoon and warms the Arabian Sea.The abnormal wind weakens the coastal Ekman transport,offshore Ekman pumping and horizontal advection,resulting in reduced upward nutrient supply to the euphotic zone.A slightly declining trend in NPP after 2000 associated with a gradual decrease in surface monsoon winds is discussed.

  4. Viral-Induced Mortality of Prokaryotes in a Tropical Monsoonal Estuary

    Science.gov (United States)

    Jasna, Vijayan; Parvathi, Ammini; Pradeep Ram, Angia Sriram; Balachandran, Kizhekkapat K.; Madhu, Nikathil V.; Nair, Maheswari; Jyothibabu, Retnamma; Jayalakshmy, K. Veeraraghava; Revichandran, Chenicherry; Sime-Ngando, Télesphore

    2017-01-01

    Viruses are recognized as the most abundant and dynamic biological entities in the marine and estuarine environment. However, studies on the dynamics and activity of viruses in transient estuarine systems are limited. This study examines temporal and spatial variations in viral abundance (VA) and viral activity across the salinity gradient in a monsoon-driven tropical estuarine system (Cochin estuary, CE) along the southwest coast of India. Water samples were collected from five stations (with different hydrological settings) every 3 h for 24 h period during two distinct seasons, namely pre-monsoon (PRM, dry season) and monsoon (MON, wet season). Time series measurements were made for a spring and neap tidal cycle for each season at all the stations. The results showed marked spatial and seasonal variability with relatively low diel and tidal variations in VA and lytic activity. Viral activity was found to be distinct in five stations studied with the maximum activity in the mesohaline regions (salinity <20) of the estuary. This region was characterized by high VA, lytic infection and viral production, accompanied by low (BGE) and high bacterial respiration. Based on viral lytic production, lytic viruses were found to be responsible for the release of ca. 72.9 ± 58.5 μg C L−1d−1 of bacterial carbon. The contribution of the viral shunt to the dissolved organic carbon (DOC) pool was higher during the dry season (PRM) than MON. Statistical analysis confirmed a significant association of viruses with the host availability and salinity. This work demonstrates the spatiotemporal distribution of viruses in a tropical estuarine ecosystem and highlights their role in microbial mortality across different salinity gradients. This study forms the first report on viral processes from a monsoon-driven tropical estuarine ecosystem. PMID:28588564

  5. A Comparison of Pre-monsoonal and Monsoonal Radiative Forcing by Anthropogenic Aerosols over South Asia

    Science.gov (United States)

    Lee, S.; Cohen, J. B.; Wang, C.

    2012-12-01

    Radiative forcing by anthropogenic aerosols after monsoon onset is often considered unimportant compared to forcing during the pre-monsoonal period, due to precipitation scavenging. We tested this assumption for the South Asian monsoon using three model runs with forcing prescribed during the pre-monsoonal period (March-May), monsoon period (June-September) and both periods. The forcing represents the direct radiative effects of sulfate, organic carbon and black carbon. It was derived from a set of Kalman filter-optimised black carbon emissions from a modelling system based on the CAM3 GCM, a two-moment multi-scheme aerosol and radiation model, and a coupled urban scale processing package; we expect it to be reliable within its given error bounds. The monthly climatological forcing values were prescribed over South Asia every year for 100 years to CESM 1.0.4, a coupled atmosphere-ocean model. We shall compare the three resultant climatologies with climatologies from a no aerosol model and a full aerosol model.

  6. Forecasting Monsoon Precipitation Using Artificial Neural Networks

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    This paper explores the application of Artificial Intelligent (AI) techniques for climate forecast. It pres ents a study on modelling the monsoon precipitation forecast by means of Artificial Neural Networks (ANNs). Using the historical data of the total amount of summer rainfall over the Delta Area of Yangtze River in China, three ANNs models have been developed to forecast the monsoon precipitation in the corre sponding area one year, five-year, and ten-year forward respectively. Performances of the models have been validated using a 'new' data set that has not been exposed to the models during the processes of model development and test. The experiment results are promising, indicating that the proposed ANNs models have good quality in terms of the accuracy, stability and generalisation ability.

  7. Asian monsoon variability, cyclicities, and forcing mechanisms

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.

    meridonal over turning with the lower circulation limb being the strong low-level southwesterly summer monsoon winds of the western Indian Ocean. The convergence of these air masses and their uplift due to heating and orographic steering cause seasonal... is the dominant climatic feature of the Indian Ocean tropics and the adjacent continent. Boreal summer is characterized by high solar radiation that causes intense sensible and latent heating over northern India and Tibet Plateau. This pattern of heating...

  8. Development of summer monsoon and onset of continuous rains over central west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Varkey, M.J.

    rains happening during the last phase of monsoon development as a consequence of and after (2-5 weeks) the establishment of monsoon circulation or monsoon front. Summer monsoon front, as the term 'monsoon' originally meant, is to be delineated from...

  9. Weakening of Indian Summer Monsoon in Recent Decades

    Institute of Scientific and Technical Information of China (English)

    WU Bingyi

    2005-01-01

    The analysis of 43 years of NCEP-NCAR reanalysis data and station observations reveals the connections between tropospheric temperature variations and the weakening of the Indian summer monsoon circulation. The Indian summer monsoon variation is strongly linked to tropospheric temperature over East Asia, showing significant positive correlations of mean tropospheric temperature with all-Indian summer rainfall and the monsoon circulation intensity. The result shows that Indian summer monsoon circulation underwent two weakening processes in recent decades. The first occurred in circa the mid-1960s, and the other occurred in circa the late 1970s. The finding indicates that the mean tropospheric temperature may play a crucial role in the weakening of the Indian summer monsoon intensity via changing land-sea thermal contrast. The role of the tropospheric temperature contrast between East Asia and the tropical area from the eastern Indian Ocean to the tropical western Pacific is to weaken the Indian summer monsoon circulation.

  10. East Asian monsoon climate simulated in the PlioMIP

    Directory of Open Access Journals (Sweden)

    R. Zhang

    2013-02-01

    Full Text Available Based on the simulations with fifteen climate models in the Pliocene Model Intercomparison Project (PlioMIP, the regional climate of East Asia (focusing on China during the mid-Pliocene is investigated in this study. Compared to the pre-industrial, the multi-model ensemble mean (MMM of all models shows the East Asian summer wind (EASW largely strengthens in monsoon China, and the East Asian winter wind (EAWW strengthens in south monsoon China but slightly weakens in north monsoon China in mid-Pliocene. The MMM of all models also illustrates a warmer and wetter mid-Pliocene climate in China. The simulated weakened mid-Pliocene EAWW in north monsoon China and intensified EASW in monsoon China agree well with geological reconstructions. However, the model-model discrepancy in simulating mid-Pliocene East Asian monsoon climate, in particular EAWW, should be further addressed in the future work of PlioMIP.

  11. Asian Monsoon Failure and Megadrought During the Last Millennium

    Science.gov (United States)

    Cook, Edward R.; Anchukaitis, Kevin J.; Buckley, Brendan M.; D'Arrigo, Rosanne D.; Jacoby, Gordon C.; Wright, William E.

    2010-04-01

    The Asian monsoon system affects more than half of humanity worldwide, yet the dynamical processes that govern its complex spatiotemporal variability are not sufficiently understood to model and predict its behavior, due in part to inadequate long-term climate observations. Here we present the Monsoon Asia Drought Atlas (MADA), a seasonally resolved gridded spatial reconstruction of Asian monsoon drought and pluvials over the past millennium, derived from a network of tree-ring chronologies. MADA provides the spatiotemporal details of known historic monsoon failures and reveals the occurrence, severity, and fingerprint of previously unknown monsoon megadroughts and their close linkages to large-scale patterns of tropical Indo-Pacific sea surface temperatures. MADA thus provides a long-term context for recent monsoon variability that is critically needed for climate modeling, prediction, and attribution.

  12. Early warnings and missed alarms for abrupt monsoon transitions

    OpenAIRE

    Z. A. Thomas; Kwasniok, F.; C. A. Boulton; Cox, P.M.; Jones, R. T.; Lenton, T. M.; C. S. M. Turney

    2015-01-01

    Palaeo-records from China (Cheng et al., 2009; Wang et al., 2008, 2001) demonstrate the East Asian Summer Monsoon (EASM) is dominated by abrupt and large magnitude monsoon shifts on millennial timescales, switching between periods of high and weak monsoon rains. It has been hypothesised that over these timescales, the EASM exhibits two stable states with bifurcation-type tipping points between them (Schewe et al., 2012). Here we test this hypothesis by looki...

  13. Early warnings and missed alarms for abrupt monsoon transitions

    OpenAIRE

    Z. A. Thomas; Kwasniok, F.; C. A. Boulton; Cox, P.M.; Jones, R. T.; Lenton, T. M.; C. S. M. Turney

    2015-01-01

    Palaeo-records from China demonstrate that the East Asian Summer Monsoon (EASM) is dominated by abrupt and large magnitude monsoon shifts on millennial timescales, switching between periods of high and weak monsoon rains. It has been hypothesized that over these timescales, the EASM exhibits two stable states with bifurcation-type tipping points between them. Here we test this hypothesis by looking for early warning signals of past bifurcations in speleothem δ18O records fro...

  14. Relationship between land cover and monsoon interannual variations in east Asia

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Asian monsoon have multiple forms of variations such as seasonal variation, intra-seasonal variation, interannual variation, etc. The interannual variations have not only yearly variations but also variations among several years. In general, the yearly variations are described with winter temperature and summer precipitation, and the variations among several years are reflected by circulation of ENSO events. In this study, at first, we analyze the relationship between land cover and interannual monsoon variations represented by precipitation changes using Singular Value Decomposition method based on the time series precipitation data and 8km NOAA AVHRR NDVI data covering 1982 to 1993 in east Asia. Furthermore, after confirmation and reclassification of ENSO events which are recognized as the strong signal of several year monsoon variation, using the same time series NDVI data during 1982 to 1993 in east Asia, we make a Principle Component Analysis and analyzed the correlation of the 7th component eigenvectors and Southern Oscillation Index (SOI) that indicates the characteristic of ENSO events, and summed up the temporal-spatial distribution features of east Asian land cover's inter-annual variations that are being driven by changes of ENSO events.

  15. Onset, active and break periods of the Australian monsoon

    Energy Technology Data Exchange (ETDEWEB)

    Shaik, Hakeem A [Northern Territory Regional Office, Australian Bureau of Meteorology, PO Box 40050, NT Regional Office, Bureau of Meteorology, Casuarina NT 0811, Darwin (Australia); Cleland, Samuel J, E-mail: h.shaik@bom.gov.a [Bureau of Meteorology, Cape Grim BAPS, Smithton Tasmania TAS 7300 (Australia)

    2010-08-15

    Four operational techniques of monsoon monitoring the Australian monsoon at Darwin have been developed in the Darwin Regional Specialised Meteorological Centre. Two techniques used the rainfall only criteria and look into the onset of wet season rainfall/monsoon rainfall. The other two techniques are based purely on Darwin wind data. The data used for the study ranges from 14 to 21 years. The main purpose of the study is to develop near-real time monitoring tools for the Australian monsoon at Darwin. The average date of onset of the monsoon ranges from 19 December to 30 December. The average date of monsoon onset is 28 December. In eleven out of twenty-one years the onset date remained within three days range between the two rainfall techniques, whereas it is eleven out of fourteen years between the wind techniques. The median number of active monsoon spells in a wet season is 3 for the rainfall techniques and 6 for the wind techniques. The average length of each active monsoon spell is around 4 days for all of the techniques. The date of onset of the monsoon has shown negative correlation with the Southern Oscillation Index (SOI) that is late onset is found to occur in El Nino years while early onset is more likely in La Nina years.

  16. Sea surface temperature variability over North Indian Ocean - A study of two contrasting monsoon seasons

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar, M.R.; Sathyendranath, S.; Viswambharan, N.K.; Rao, L.V.G.

    Using the satellite derived sea surface temperature (SST) data for 1979 (bad monsoon) and 1983 (good monsoon), the SST variability for two contrasting monsoon seasons is studied. The study indicates that large negative anomalies off the Somali...

  17. Stable isotopes in monsoon precipitation and water vapour in Nagqu, Tibet, and their implications for monsoon moisture

    Science.gov (United States)

    He, Siyuan; Richards, Keith

    2016-09-01

    Understanding climate variations over the Qinghai-Tibetan plateau has become essential because the high plateau sustains various ecosystems and water sources, and impacts on the Asian monsoon system. This paper provides new information from isotopic signals in meteoric water and atmospheric water vapour on the Qinghai-Tibetan Plateau using high frequency observation data over a relatively short period. The aim is to explore temporal moisture changes and annual variations at the onset and during the summer monsoon season at a transitional site with respect to the monsoon influence. Data show that high frequency and short period observations can reveal typical moisture changes from the pre-monsoon to the monsoon seasons (2010), and the large variation in isotopic signals in different years with respect to active/inactive periods during a mature phase of the monsoon (2011), especially inferring from the temporal changes in the d-excess of precipitation and its relationship with δ18O values, when higher d-excess is found in the pre-monsoon precipitation. In this transition zone on a daily basis, δ18O values in precipitation are controlled mainly by the amount of rainfall during the monsoon season, while temperature seems more important before the onset of monsoon. Furthermore, the "amount effect" is significant for night-time rain events. From comparison of signals in both the precipitation and water vapour, an inconsistent relationship between d-excess values suggests various moisture fluxes are active in a short period. The temporal pattern of isotopic signal change from the onset of the monsoon to the mature monsoon phase provides information about the larger circulation dynamics of the Asian monsoon.

  18. COMPARATIVE STUDY OF DISEASE PATTERNS AND SCHOLASTIC PERFORMANCE AMONG RURAL, URBAN AND TRIBAL GOVERNMENT RESIDENTIAL HOSTEL CHILDREN OF EAST GODAVARI DISTRICT

    Directory of Open Access Journals (Sweden)

    Sirigineedi Chandra

    2016-04-01

    Full Text Available BACKGROUND Most of the children from tribal, rural and urban slums are found to suffer from health problems due to poor quality of life. Malnutrition continues to be major threat leading to morbidities and poor scholastic performance in these children. The welfare hostels for the children are established for weaker sections of the society as an important social welfare measure in India since long time. The data regarding the nutritional, morbidity status and scholastic performance of the children in social welfare hostels are sparse. With this background, this study was conducted to evaluate the extent and pattern of health status of school age children and their scholastic performance using a predesigned proforma. METHODS The study was conducted in randomly selected 3 hostels from urban, rural and tribal areas of East Godavari District. It was a cross sectional observational study. RESULTS Mild anaemia, poor attention and calculation ability, dental caries, refractive errors, nonspecific headaches, dermatological problems, Vitamin A deficiency were the commonly seen problems in all rural, urban, tribal hostellers. CONCLUSION Anaemia, dermatological problems and dental caries are more commonly observed in all, hence hygienic conditions and nutritional supplementations are to be improved. Regular de-worming program has to be successfully implemented in the hostels to decrease the prevalence of worm infestations. Poor scholastic performance can be improved by implementing skilled training programs like Pradhan Mantri Kaushal Vikas Yojana (PMKVY in these hostels along with formal education.

  19. Kinematics of large scale asymmetric folds and associated smaller scale brittle-ductile structures in the Proterozoic Somnur Formation, Pranhita - Godavari valley, south India

    Indian Academy of Sciences (India)

    Gautam Ghosh; Dilip Saha

    2005-04-01

    The development of structural elements and finite strain data are analysed to constrain kinematics of folds and faults at various scales within a Proterozoic fold-and-thrust belt in Pranhita-Godavari basin, south India. The first order structures in this belt are interpreted as large scale buckle folds above a subsurface decollement emphasizing the importance of detachment folding in thin skinned deformation of a sedimentary prism lying above a gneissic basement. That the folds have developed through fixed-hinge buckling is constrained by the nature of variation of mesoscopic fabric over large folds and finite strain data. Relatively low, irrotational °attening strain (X:Z - 3.1-4.8, k > 1) are associated with zones of near upright early mesoscopic folds and cleavage, whereas large flattening strain (X:Z - 3.9-7.3, k > 1) involving noncoaxiality are linked to domains of asymmetric, later inclined folds, faults and intense cleavage on the hanging wall of thrusts on the flanks of large folds. In the latter case, the bulk strain can be factorized to components of pure shear and simple shear with a maximum shearing strain of 3. The present work reiterates the importance of analysis of minor structures in conjunction with strain data to unravel the kinematic history of fold-and-thrust belts developed at shallow crustal level.

  20. Shallow geological environment of Krishna–Godavari offshore, eastern continental margin of India as inferred from the interpretation of high resolution sparker data

    Indian Academy of Sciences (India)

    G Anitha; M V Ramana; T Ramprasad; P Dewangan; M Anuradha

    2014-03-01

    Krishna–Godavari offshore basin, a part of the eastern continental margin of India is a proven petroliferous basin. Recent drilling in this area in search of gas hydrates reveals that the upper ∼300 m thick Quaternary–Recent strata comprised of nannofossil bearing rich clays and, fractures/faults are the suitable zones for gas hydrates accumulation. Therefore, the knowledge about the shallow geological environments and its architecture are significantly important in assessing the gas hydrates potential of this area. In order to enhance the geological understanding, the newly acquired high resolution seismic (HRS) reflection data in this gas hydrates prone area is interpreted. The processed seismic sections show a maximum penetration of 562 ms TWT (∼450 m) underneath the seabed with high resolution stratification. An attempt has been made to: (i) deduce the shallow geological environment from the reflection characteristics, and, (ii) assign tentative ages under the constraints of drilling/coring results. We further explained the observed folded structures on the surface and subsurface through a mechanism linked to shale tectonism and neotectonic activity.

  1. Pattern of Holocene glaciation in the monsoon-dominated Kosa Valley, central Himalaya, Uttarakhand, India

    Science.gov (United States)

    Bisht, Pinkey; Nawaz Ali, S.; Rana, Naresh; Singh, Sunil; Poonam; Sundriyal, Y. P.; Bagri, D. S.; Juyal, Navin

    2017-05-01

    Reconstruction based on the geomorphology, lateral moraine stratigraphy, and limited optical chronology indicate that the monsoon-dominated Kosa Valley experienced four glacial advances during the late glacial to late Holocene. The oldest and most extensive glaciation, which is termed as Raj Bank Stage-1 (RBS-1), is represented by the degraded moraine ridge. This glaciation remains undated; however, the chronology of outwash terrace gravel dated to 12.7 ± 1.3 ka indicates that the RBS-1 probably represents the Last Glacial Maximum (LGM). The second glacial advance (RBS-2) is preserved as a curvilinear lateral moraine and is dated to 6.1 ± 0.4 ka. The third glacial advance viz. RBS-3 is bracketed between 5.0 ± 0.5 and 4.0 ± 0.4 ka. Following this, the glacier receded in pulses that are represented by two distinct recessional moraines (RBS-3a and b). The forth glacial stage (RBS-4), which is dated between 2.2 ± 0.2 and 1.6 ± 0.2 ka, shows a pulsating recession and is represented by a prominent recessional moraine (RBS-4a). Whereas, presence of unconsolidated, poorly defined moraine mounds proximal to the glacier snout are ascribed as neoglacial advance corresponding to the Little Ice Age (LIA). With the limited chronometric data, we speculated that the glaciation was driven during the weak to moderate Indian Summer Monsoon (ISM) aided by lowered temperature. Presence of recessional moraines associated with mid-Holocene glacial phase indicate that the monsoon-dominated glaciers respond sensitively to minor (sub-millennial scale) changes in temperature and precipitation conditions. The observations are broadly in accordance with the studies carried out in other monsoon-dominated valleys in the central Himalaya, implying that in ISM dominated regions, lowered temperature seems to be the major driver of glaciations during the late glacial to late Holocene.

  2. Meteorological fields variability over the Indian seas in pre and summer monsoon months during extreme monsoon seasons

    Indian Academy of Sciences (India)

    U C Mohanty; R Bhatla; P V S Raju; O P Madan; A Sarkar

    2002-09-01

    In this study, the possible linkage between summer monsoon rainfall over India and surface meteorological fields (basic fields and heat budget components) over monsoon region (30° E-120°E, 30°S-30°N) during the pre-monsoon month of May and summer monsoon season (June to September) are examined. For this purpose, monthly surface meteorological fields anomaly are analyzed for 42 years (1958-1999) using reanalysis data of NCEP/NCAR (National Center for Environmental Prediction/National Center for Atmospheric Research). The statistical significance of the anomaly (difference) between the surplus and deficient monsoon years in the surface meteorological fields are also examined by Student's t-test at 95% confidence level. Significant negative anomalies of mean sea level pressure are observed over India, Arabian Sea and Arabian Peninsular in the pre-monsoon month of May and monsoon season. Significant positive anomalies in the zonal and meridional wind (at 2m) in the month of May are observed in the west Arabian Sea off Somali coast and for monsoon season it is in the central Arabian Sea that extends up to Somalia. Significant positive anomalies of the surface temperature and air temperature (at 2m) in the month of May are observed over north India and adjoining Pakistan and Afghanistan region. During monsoon season this region is replaced by significant negative anomalies. In the month of May, significant positive anomalies of cloud amount are observed over Somali coast, north Bay of Bengal and adjoining West Bengal and Bangladesh. During monsoon season, cloud amount shows positive anomalies over NW India and north Arabian Sea. There is overall reduction in the incoming shortwave radiation flux during surplus monsoon years. A higher magnitude of latent heat flux is also found in surplus monsoon years for the month of May as well as the monsoon season. The significant positive anomaly of latent heat flux in May, observed over southwest Arabian Sea, may be considered

  3. The abrupt onset of the modern South Asian Monsoon winds

    Science.gov (United States)

    Betzler, Christian; Eberli, Gregor P.; Kroon, Dick; Wright, James D.; Swart, Peter K.; Nath, Bejugam Nagender; Alvarez-Zarikian, Carlos A.; Alonso-García, Montserrat; Bialik, Or M.; Blättler, Clara L.; Guo, Junhua Adam; Haffen, Sébastien; Horozal, Senay; Inoue, Mayuri; Jovane, Luigi; Lanci, Luca; Laya, Juan Carlos; Mee, Anna Ling Hui; Lüdmann, Thomas; Nakakuni, Masatoshi; Niino, Kaoru; Petruny, Loren M.; Pratiwi, Santi D.; Reijmer, John J. G.; Reolid, Jesús; Slagle, Angela L.; Sloss, Craig R.; Su, Xiang; Yao, Zhengquan; Young, Jeremy R.

    2016-07-01

    The South Asian Monson (SAM) is one of the most intense climatic elements yet its initiation and variations are not well established. Dating the deposits of SAM wind-driven currents in IODP cores from the Maldives yields an age of 12. 9 Ma indicating an abrupt SAM onset, over a short period of 300 kyrs. This coincided with the Indian Ocean Oxygen Minimum Zone expansion as revealed by geochemical tracers and the onset of upwelling reflected by the sediment’s content of particulate organic matter. A weaker ‘proto-monsoon’ existed between 12.9 and 25 Ma, as mirrored by the sedimentary signature of dust influx. Abrupt SAM initiation favors a strong influence of climate in addition to the tectonic control, and we propose that the post Miocene Climate Optimum cooling, together with increased continentalization and establishment of the bipolar ocean circulation, i.e. the beginning of the modern world, shifted the monsoon over a threshold towards the modern system.

  4. The relationship between Arabian Sea upwelling and Indian monsoon revisited

    Directory of Open Access Journals (Sweden)

    X. Yi

    2015-11-01

    Full Text Available Studies based on upwelling indices (sediment records, sea-surface temperature and wind suggest that upwelling along the western coast of Arabian Sea is strongly affected by the Indian summer monsoon (ISM. In order to examine this relationship directly, we employ the vertical water mass transport produced by the eddy-resolving global ocean simulation STORM driven by meteorological reanalysis over the last 61 years. With its very high spatial resolution (10 km, STORM allows us to identify characteristics of the upwelling system. We analyze the co-variability between upwelling and meteorological and oceanic variables from 1950 to 2010. The analyses reveal high interannual correlations between coastal upwelling and along-shore wind-stress (r=0.73 as well as with sea-surface temperature (r0.83. However, the correlation between the upwelling and the ISM is small and other factors might contribute to the upwelling variability. In addition, no long-term trend is detected in our modeled upwelling time series.

  5. Asian Eocene monsoons as revealed by leaf architectural signatures

    Science.gov (United States)

    Spicer, Robert A.; Yang, Jian; Herman, Alexei B.; Kodrul, Tatiana; Maslova, Natalia; Spicer, Teresa E. V.; Aleksandrova, Galina; Jin, Jianhua

    2016-09-01

    The onset and development of the Asian monsoon systems is a topic that has attracted considerable research effort but proxy data limitations, coupled with a diversity of definitions and metrics characterizing monsoon phenomena, have generated much debate. Failure of geological proxies to yield metrics capable of distinguishing between rainfall seasonality induced by migrations of the Inter-tropical Convergence Zone (ITCZ) from that attributable to topographically modified seasonal pressure reversals has frustrated attempts to understand mechanisms underpinning monsoon development and dynamics. Here we circumvent the use of such single climate parameter metrics in favor of detecting directly the distinctive attributes of different monsoon regimes encoded in leaf fossils. Leaf form adapts to the prevailing climate, particularly under the extreme seasonal stresses imposed by monsoons, so it is likely that fossil leaves carry a unique signature of past monsoon regimes. Leaf form trait spectra obtained from fossils from Eocene basins in southern China were compared with those seen in modern leaves growing under known climate regimes. The fossil leaf trait spectra, including those derived from previously published fossil floras from northwestern India, were most similar to those found in vegetation exposed to the modern Indonesia-Australia Monsoon (I-AM), which is largely a product of seasonal migrations of the ITCZ. The presence of this distinctive leaf physiognomic signature suggests that although a monsoon climate existed in Eocene time across southern Asia the characteristics of the modern topographically-enhanced South Asia Monsoon had yet to develop. By the Eocene leaves in South Asia had become well adapted to an I-AM type regime across many taxa and points to the existence of a pervasive monsoon climate prior to the Eocene. No fossil trait spectra typical of exposure to the modern East Asia monsoon were seen, suggesting the effects of this system in southern

  6. Early forecasting of Indian Summer Monsoon: case study 2016

    Science.gov (United States)

    Surovyatkina, Elena; Stolbova, Veronika; Kurths, Jurgen

    2017-04-01

    The prior knowledge of dates of onset and withdrawal of monsoon is of vital importance for the population of the Indian subcontinent. In May 2016 before monsoon season, India recorded its highest-ever temperature of 51C. Hot waves have decimated crops, killed livestock and left 330 million people without enough water. At the end of monsoon season the floods in Indian this year have also broken previous records. Severe and devastating rainfall poured down, triggering dams spilling and floods. Such extreme conditions pose the vital questions such as: When will the monsoon come? When will the monsoon withdraw? More lead time in monsoon forecast warning is crucial for taking appropriate decisions at various levels - from the farmer's field (e.g. plowing day, seeding) to the central government (e.g. managing water and energy resources, food procurement policies). The Indian Meteorological Department issues forecasts of onset of monsoon for Kerala state in South India on May 15-th. It does not give such predictions for the other 28 states of the country. Our study concerns the central part of India. We made the monsoon forecast using our recently developed method which focuses on Tipping elements of the Indian monsoon [1]. Our prediction relies on observations of near-surface air temperature and relative humidity from both the ERA-40 and NCEP/NCAR reanalyses. We performed both of our forecasts for the onset and withdrawal of monsoon for the central part of India, the Eastern Ghats (20N,80E). We predicted the monsoon arrival to the Eastern Ghats (20N,80E) on the 13th of June with a deviation of +/-4 days. The prediction was made on May 6-th, 2016 [2], that is 40 days in advance of the date of the forecast. The actual monsoon arrival was June 17-th. In this day near-surface air temperature and relative humidity overcame the critical values and the monsoon season started, that was confirmed by observations of meteorological stations located around the EG-region. We

  7. Time-dependence of salinity in monsoonal estuaries

    Digital Repository Service at National Institute of Oceanography (India)

    Vijith, V.; Sundar, D.; Shetye, S.R.

    and come under the influence of the Indian Summer Monsoon (ISM) is never in a steady state. We refer to such estuaries as "monsoonal estuaries", an example of which is the Mandovi estuary located on the west coast of India. We describe the annual cycle...

  8. Evaporation over the Arabian Sea during two contrasting monsoons

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar, M.R.; Sadhuram, Y.

    monsoon rainfall. It is noticed that in general, the sea surface temperatures are higher in 1983 throughout the monsoon season than in 1979 in the Arabian Sea excepting western region. The mean rates of evaporation on a seasonal scale are found to be equal...

  9. Reconciling societal and scientific definitions for the monsoon

    Science.gov (United States)

    Reeve, Mathew; Stephenson, David

    2014-05-01

    Science defines the monsoon in numerous ways. We can apply these definitions to forecast data, reanalysis data, observations, GCMs and more. In a basic research setting, we hope that this work will advance science and our understanding of the monsoon system. In an applied research setting, we often hope that this work will benefit a specific stakeholder or community. We may want to inform a stakeholder when the monsoon starts, now and in the future. However, what happens if the stakeholders cannot relate to the information because their perceptions do not align with the monsoon definition we use in our analysis? We can resolve this either by teaching the stakeholders or learning from them about how they define the monsoon and when they perceive it to begin. In this work we reconcile different scientific monsoon definitions with the perceptions of agricultural communities in Bangladesh. We have developed a statistical technique that rates different scientific definitions against the people's perceptions of when the monsoon starts and ends. We construct a probability mass function (pmf) around each of the respondent's answers in a questionnaire survey. We can use this pmf to analyze the time series of monsoon onsets and withdrawals from the different scientific definitions. We can thereby quantitatively judge which definition may be most appropriate for a specific applied research setting.

  10. Autoencoder-based identification of predictors of Indian monsoon

    Science.gov (United States)

    Saha, Moumita; Mitra, Pabitra; Nanjundiah, Ravi S.

    2016-10-01

    Prediction of Indian summer monsoon uses a number of climatic variables that are historically known to provide a high skill. However, relationships between predictors and predictand could be complex and also change with time. The present work attempts to use a machine learning technique to identify new predictors for forecasting the Indian monsoon. A neural network-based non-linear dimensionality reduction technique, namely, the sparse autoencoder is used for this purpose. It extracts a number of new predictors that have prediction skills higher than the existing ones. Two non-linear ensemble prediction models of regression tree and bagged decision tree are designed with identified monsoon predictors and are shown to be superior in terms of prediction accuracy. Proposed model shows mean absolute error of 4.5 % in predicting the Indian summer monsoon rainfall. Lastly, geographical distribution of the new monsoon predictors and their characteristics are discussed.

  11. Identifying the northernmost summer monsoon location in East Asia

    Institute of Scientific and Technical Information of China (English)

    Hu Haoran; Qian Weihong

    2007-01-01

    An integrated index which can be used to indicate the advance of subtropical summer monsoon in East Asia has been proposed in this paper. The index was combined by three variables including precipitation, wind and pseudo-equivalent potential temperature. The northernmost summer monsoon location (NSML) was identified by using this index annually. It was found that the NSML experienced an interdecadal shift in the period 1977-1979 based on the annual index analysis from 1961 to 2001. A comparison of the NSML with other four summer monsoon indices has also been made. The result showed that the NSML could well represent the interannual and interdecadal variability of summer monsoon precipitation in North China (beyond 35°N), while other four indices could well indicate the precipitation anomalies of East Asian summer monsoon along the Yangtze River valley (around 30°N).

  12. Comparison of East Asian winter monsoon indices

    Directory of Open Access Journals (Sweden)

    Gao Hui

    2007-01-01

    Full Text Available Four East Asian winter monsoon (EAWM indices are compared in this paper. In the research periods, all the indices show similar interannual and decadal-interdecadal variations, with predominant periods centering in 3–4 years, 6.5 years and 9–15 years, respectively. Besides, all the indices show remarkable weakening trends since the 1980s. The correlation coefficient of each two indices is positive with a significance level of 99%. Both the correlation analyses and the composites indicate that in stronger EAWM years, the Siberian high and the higher-level subtropical westerly jet are stronger, and the Aleutian low and the East Asia trough are deeper. This circulation pattern is favorable for much stronger northwesterly wind and lower air temperature in the subtropical regions of East Asia, while it is on the opposite in weaker EAWM years. Besides, EAWM can also exert a remarkable leading effect on the summer monsoon. After stronger (weaker EAWM, less (more summer precipitation is seen over the regions from the Yangtze River valley of China to southern Japan, while more (less from South China Sea to the tropical western Pacific.

  13. Seismic characterization of hydrates in faulted, fine-grained sediments of Krishna-Godavari basin: Full waveform inversion.

    Digital Repository Service at National Institute of Oceanography (India)

    Jaiswal, P.; Dewangan, P.; Ramprasad, T.; Zelt, C.A.

    potentially significant role in climate change (Gu et al., 2011), seafloor stability (Brown et al., 2006), and energy security (Boswell and Collett, 2011). Gas hydrates detection in offshore continental margins is generally guided by a bottom simulating... of eastern continental margin of India (Figure 1). We apply FWI in the frequency domain. The domain choice is driven by a) efficiency in forward modeling (Marfurt, 1984), and b) the possibility of a multiscale implementation (Sirgue and Pratt, 2004) which...

  14. A meridional dipole in premonsoon Bay of Bengal tropical cyclone activity induced by ENSO: TROPICAL CYCLONES, MONSOON AND ENSO

    Energy Technology Data Exchange (ETDEWEB)

    Balaguru, Karthik [Marine Sciences Laboratory, Pacific Northwest National Laboratory, Seattle Washington USA; Leung, L. Ruby [Atmospheric Sciences and Global Change, Pacific Northwest National Laboratory, Richland Washington USA; Lu, Jian [Atmospheric Sciences and Global Change, Pacific Northwest National Laboratory, Richland Washington USA; Foltz, Gregory R. [Physical Oceanography Division, Atlantic Oceanographic and Meteorological Laboratory, Miami Florida USA

    2016-06-27

    Analysis of Bay of Bengal tropical cyclone (TC) track data for the month of May during 1980-2013 reveals a meridional dipole in TC intensification: TC intensification rates increased in the northern Bay and decreased in the southern Bay. The dipole was driven by an increase in low-level vorticity and atmospheric humidity in the northern Bay, making the environment more favorable for TC intensification, and enhanced vertical wind shear in the southern Bay, tending to reduce TC development. These environmental changes were associated with a strengthening of the monsoon circulation for the month of May, driven by a La Nin˜a-like shift in tropical Pacific SSTs andassociated tropical wave dynamics. Analysis of a suite of climate models fromthe CMIP5 archive for the 150-year historical period shows that most models correctly reproduce the link between ENSO and Bay of Bengal TC activity through the monsoon at interannual timescales. Under the RCP 8.5 scenario the same CMIP5 models produce an El Nin˜o like warming trend in the equatorial Pacific, tending to weaken the monsoon circulation. These results suggest

  15. Impact of GCM boundary forcing on regional climate modeling of West African summer monsoon precipitation and circulation features

    Science.gov (United States)

    Kebe, Ibourahima; Sylla, Mouhamadou Bamba; Omotosho, Jerome Adebayo; Nikiema, Pinghouinde Michel; Gibba, Peter; Giorgi, Filippo

    2017-03-01

    In this study, the latest version of the International Centre for Theoretical Physics Regional Climate Model (RegCM4) driven by three CMIP5 Global Climate Models (GCMs) is used at 25 km grid spacing over West Africa to investigate the impact of lateral boundary forcings on the simulation of monsoon precipitation and its relationship with regional circulation features. We find that the RegCM4 experiments along with their multimodel ensemble generally reproduce the location of the main precipitation characteristics over the region and improve upon the corresponding driving GCMs. However, the provision of different forcing boundary conditions leads to substantially different precipitation magnitudes and spatial patterns. For instance, while RegCM4 nested within GFDL-ESM-2M and HadGEM2-ES exhibits some underestimations of precipitation and an excessively narrow Intertropical Convergence Zone, the MPI-ESM-MR driven run produces precipitation spatial distribution and magnitudes more similar to observations. Such a superior performance originates from a much better simulation of the interactions between baroclinicity, temperature gradient and African Easterly Jet along with an improved connection between the Isentropic Potential Vorticity, its gradient and the African Easterly Waves dynamics. We conclude that a good performing GCM in terms of monsoon dynamical features (in this case MPI-ESM-MR) is needed to drive RCMs in order to achieve a better representation of the West Africa summer monsoon precipitation.

  16. Numerical simulations of barnacle larval dispersion coupled with field observations on larval abundance, settlement and recruitment in a tropical monsoon influenced coastal marine environment

    Science.gov (United States)

    Gaonkar, Chetan A.; Samiksha, S. V.; George, Grinson; Aboobacker, V. M.; Vethamony, P.; Anil, Arga Chandrashekar

    2012-06-01

    larval dispersion and retention in the region is predominantly driven by local hydrodynamics operating in the vicinity. Linking larval dispersion and retention with settlement and recruitment of barnacles indicated that the processes are mainly influenced by wind and resultant current patterns. These findings facilitate unravelling the processes operating in the region and to understand the distribution pattern of the intertidal organisms in general in this tropical environment influenced by monsoons.

  17. Forced and internal modes of variability of the East Asian summer monsoon

    Directory of Open Access Journals (Sweden)

    J. Liu

    2008-05-01

    Full Text Available The modern instrumental record (1979–2006 is analyzed in an attempt to reveal the dynamical structure and origins of the major modes of interannual variability of East Asian summer monsoon (EASM and to elucidate their fundamental differences with the major modes of seasonal variability. These differences are instrumental in understanding of the forced (say orbital and internal (say interannual modes of variability in EASM. We show that the leading mode of interannual variation, which accounts for about 39% of the total variance, is primarily associated with decaying phases of major El Nino, whereas the second mode, which accounts for 11.3% of the total variance, is associated with the developing phase of El Nino/La Nina. The EASM responds to ENSO in a nonlinear fashion with regard to the developing and decay phases of El Nino. The two modes are determined by El Nino/La Nina forcing and monsoon-warm ocean interaction, or essentially driven by internal feedback processes within the coupled climate system. For this internal mode, the intertropical convergence zone (ITCZ and subtropical EASM precipitations exhibit an out-of-phase variations; further, the Meiyu in Yangtze River Valley is also out-of-phase with the precipitation in the central North China.

    In contrast, the slow and fast annual cycles forced by the solar radiation show an in-phase correlation between the ITCZ and subtropical EASM precipitation. Further, the seasonal march of precipitation displays a continental-scale northward advance of a rain band (that tilts in a southwest-northeastward direction over the entire Indian and East Asian summer monsoon from mid-May toward the end of July. This uniformity in seasonal advance suggests that the position of the northern edge of the summer monsoon or the precipitation over the central North China may be an adequate measure of the monsoon intensity for the forced mode, while the intensity of the internal mode of EASM variability

  18. Late Quaternary Planktic Foraminifer Fauna andMonsoon Upwelling Records from the Western South China Sea, Near the Vietnam

    Directory of Open Access Journals (Sweden)

    Pai-Sen Yu

    2008-01-01

    Full Text Available Marine sediment core MD012394 from the Vietnam coastal upwelling area in the western South China Sea was investigated in order to reconstruct the last Quaternary monsoon upwelling based on planktic foraminifer fauna assemblages and fauna-based sea surface temperature (SST estimates. The age model of core MD012394 was constructed using oxygen isotope stratigraphy of the planktic foraminifer G. sacculifer, with 10 accelerator mass spectrometry (AMS 14C dating of planktic foraminifers from the sediment samples. Our studies on the relative and absolute abundances of planktic foraminifer assemblages reveal eight dominant species in core MD012394: N. dutertrei + N. pachyderma (right coiling, G. ruber, G. glutinata, G. sacculifer, P. obliquiloculata, G. menardii + G. tumida, G. calida, and G. inflata. In a Q-mode factor analysis of the fauna abundance data, the fauna factors show variations that do not parallel the glacial/interglacial changes throughout the last 135 kyr. The relative abundance patterns of G. inflata and N. dutertrei (including N. pachyderma-R are interpreted as hydrographic proxies for East Asian summer and winter monsoon, respectively, in the current study. We calculated the fluctuations in the SST using the Revised Analog Method (RAM in MD012394 and found that the abundance changes of the summer monsoon upwelling indicator G. inflata were similar and nearly synchronous. This suggests that the summer monsoon-driven upwelling signal was strong near the local summer insolation maximum, which induced low SSTs, particular around ~11, 33, 59, and 83 kya. Our studies support the view that the strengths of both summer insolation and the East Asian summer monsoon have determined the relative abundance of planktic foraminifers and the SSTs in the western SCS during the last 135 kyr.

  19. Interannual variability of South American monsoon circulation

    Science.gov (United States)

    Alonso Gan, Manoel; Rafaele Araújo Lima, Jeane

    2016-04-01

    The South America Monsoon System (SAMS) is responsible for influencing the atmospheric circulation and precipitation over most of tropical South America (SA) during the summer season. Studies for aiming to understand the temporal variability of this system have great value to the scientific community, because the processes that control the monsoon climate are not totally clear. Thus, the main objective of this research is to investigate the possible large-scale climatic factors and the remote interaction mechanisms, which may be associated with summer season interannual variability focusing on identifying the main differences between dry and wet extremes rainy season in the South-eastern Amazon Basin (SAB), Central-West (WC) and Southeast (SE) of Brazil, which are areas influenced by the summer monsoon regime. For such analyzes, Pearson correlations, quantile method and composite analysis were used during the period from 1979 to 2014. The correlation between precipitation anomaly in SAB and the sea surface temperature anomaly (SSTA) and wind at 850hPa and 300hPa indicate El Niño-Southern Oscillation (ENSO) influence. Precipitation anomalies in WC did not show significant correlation with SSTA. However, a pattern similar to ENSO Modoki type was observed in the composite analysis. At 850 hPa, the presence of an anomalous cyclonic (anticyclonic) circulation was observed over the central region of SA during wet (dry) summers seasons. Over SE region of Brazil, a dipole SSTA pattern over the South Atlantic was identified, as well the presence of anomalous circulations with an equivalent barotropic structure over these SSTA areas. This pattern is more evident in case of dry summer on the SE. At 300 hPa, the wave train between 30°S-60°S was observed presenting a feature curvature from 120°W reaching SA, similar to the Pacific-South American pattern (PSA). Analysis of the summer interannual variability indicated the manifestation of wet summers more frequently than dry

  20. The Indian summer monsoon as revealed by NCMRWF system

    Indian Academy of Sciences (India)

    P L S Rao; U C Mohanty; P V S Raju; Gopal Iyengar

    2003-03-01

    In this study, we present the mean seasonal features of the Indian summer monsoon circulation in the National Centre for Medium Range Weather Forecasting (NCMRWF) global data assimilation and forecast system. The large-scale budgets of heat and moisture are examined in the analyzed and model atmosphere. The daily operational analyses and forecasts (day 1 through day 5) produced for the summer seasons comprising June, July and August of 1995 and 1993 have been considered for the purpose. The principal aim of the study is two-fold. Primarily, to comprehend the influence of the systematic errors over the Indian summer monsoon, secondarily, to analyze the performance of the model in capturing the interseasonal variability. The heat and moisture balances show reduction in the influx of heat and moisture in the model forecasts compared to the analyzed atmosphere over the monsoon domain. Consequently, the diabatic heating also indicates reducing trend with increase in the forecast period. In effect, the strength of Indian summer monsoon, which essentially depends on these parameters, weakens considerably in the model forecasts. Despite producing feeble monsoon circulation, the model captures interseasonal variability realistically. Although, 1995 and 1993 are fairly normal monsoon seasons, the former received more rainfall compared to the latter in certain pockets of the monsoon domain. This is clearly indicated by the analyzed and model atmosphere in terms of energetics.

  1. Onset of Indian Summer Monsoon: a retrospective analysis

    Science.gov (United States)

    Sruthi, S.; Mrudula, G.

    2016-05-01

    The monsoon onset over Kerala is considered as the beginning of rain fall over India and it is the end of hot summer. Different criteria have been used to define the monsoon onset over Kerala, with the one given by India Meteorological Department taken as the standard criteria. The analysis of the past 20 years of observations shows that the variables during the monsoon onset do not behave in the same way always. The purpose of this paper is to analyses the monsoon onset phases and to find possible reasons behind the variable nature of the monsoon onset. Different meteorological parameters like precipitation, outgoing long wave radiation (OLR), winds, air temperature, and specific humidity at different levels are analyzed for the same. Research has been done on various distinct features of monsoon such as Low Level Jet (LLJ), Tropical Easterly Jet (TEJ), monsoon trough, and depressions etc., during the onset phase. The analysis showed that in some years the strength of LLJ is lesser compared to the normal years. It is also seen that in some years the wind flow pattern is different from that observed during a standard onset year. The results of these analyses will be presented in detail in the paper.

  2. Anomalous behaviour of the Indian summer monsoon 2009

    Indian Academy of Sciences (India)

    B Preethi; J V Revadekar; R H Kripalani

    2011-10-01

    The Indian subcontinent witnessed a severe monsoon drought in the year 2009. India as a whole received 77% of its long period average during summer monsoon season (1 June to 30 September) of 2009, which is the third highest deficient all India monsoon season rainfall year during the period 1901–2009. Therefore, an attempt is made in this paper to study the characteristic features of summer monsoon rainfall of 2009 over the country and to investigate some of the possible causes behind the anomalous behaviour of the monsoon. Presence of El Niño like conditions in the Pacific and warming over the equatorial Indian Ocean altered the circulation patterns and produced an anomalous low level convergence and ascending motion over the Indian Ocean region and large scale subsidence over the Indian landmass. Furthermore, the crossequatorial flow was weak, the monsoon was dominated by the slower 30–60 day mode, and the synoptic systems, which formed over the Bay of Bengal and the Arabian Sea, did not move inland. All the above features resulted in less moisture supply over the Indian landmass, resulting in subdued rainfall activity leading to a severe monsoon drought during 2009.

  3. Impacts of East Asian aerosols on the Asian monsoon

    Science.gov (United States)

    Bartlett, Rachel; Bollasina, Massimo; Booth, Ben; Dunstone, Nick; Marenco, Franco

    2016-04-01

    Over recent decades, aerosol emissions from Asia have increased rapidly. Aerosols are able to alter radiative forcing and regional hydroclimate through direct and indirect effects. Large emissions within the geographical region of the Asian monsoon have been found to impact upon this vital system and have been linked to observed drying trends. The interconnected nature of smaller regional monsoon components (e.g. the Indian monsoon and East Asian monsoon) presents the possibility that aerosol sources could have far-reaching impacts. Future aerosol emissions are uncertain and may continue to dominate regional impacts on the Asian monsoon. Standard IPCC future emissions scenarios do not take a broad sample of possible aerosol pathways. We investigate the sensitivity of the Asian monsoon to East Asian aerosol emissions. Experiments carried out with HadGEM2-ES use three time-evolving future anthropogenic aerosol emissions scenarios with similar time-evolving greenhouse gases. We find a wetter summer over southern China and the Indochina Peninsula associated with increased sulfate aerosol over China. The southern-flood-northern-drought pattern seen in observations is reflected in these results. India is found to be drier in the summer overall, although wetter in June. These precipitation changes are linked to the increase in sulfate through the alteration of large scale dynamics. Sub-seasonal changes are also seen, with an earlier withdrawal of the monsoon over East Asia.

  4. Book Review: Late Cenozoic Climate Change in Asia: Loess, Monsoon and Monsoon-arid Environment Evolution

    Science.gov (United States)

    Clemens, Steven C.

    2015-01-01

    Loess-Paleosol deposits drape >500,000 km2 of eastern China, spanning environments from the humid, monsoon-influenced regions near the coast to the arid, westerlies-dominated regions inland. Sections, up to hundreds of meters thick, are exposed in deeply incised river valleys and can be accessed as well by drilling. Combined, the high sedimentation rates and extensive geographic coverage make these sections unique among global terrestrial sediment archives. The Chinese loess-paleosol sequences, and the arid interior regions to the northwest, record diverse aspects of geologic and environmental change ranging from the tectonic evolution of the Tibetan Plateau (106 year time scale) through glacial-interglacial scale changes in global ice volume and greenhouse gasses (105 year time scale) on down through the orbital (104 years) to millennial and centennial scale events (103-102 year) relevant to the underpinnings of human interactions with changing environmental pressures. 'Late Cenozoic Climate Chang in Asia: Loess, Monsoon and Monsoon-arid Environment Evolution' is a timely contribution that synthesizes findings derived from the extensive work in these areas, places the findings in the broader context of global climate change and helps to define avenues for future research.

  5. Dynamics of Projected Changes in South Asian Summer Monsoon Climate

    Science.gov (United States)

    Kulkarni, A.; Sabade, S.; Kripalani, R.

    2011-12-01

    South Asian summer monsoon (June through September) rainfall simulation and its potential future changes are evaluated in a multi-model ensemble of global coupled climate models outputs under World Climate Research Program Coupled Model Intercomparison Project (WCRP CMIP3) data set. The response of South Asian summer monsoon to a transient increase in future anthropogenic radiative forcing is investigated for two time slices , middle (2031-2050) and end of the 21st century (2081-2100) in the non-mitigated Special Report on Emission Scenarios (SRES) B1, A1B and A2 .There is large inter-model variability in simulation of spatial characteristics of seasonal monsoon precipitation. Ten out of 25 models are able to simulate space-time characteristics of South Asian monsoon precipitation reasonably well. The response of these selected 10 models have been examined for projected changes in seasonal monsoon rainfall. The multi-model ensemble of these 10 models project significant increase in monsoon precipitation with global warming. The substantial increase in precipitation is observed over western equatorial Indian Ocean and southern parts of India. However the monsoon circulation weakens significantly under all the three climate change experiments. Possible mechanisms for projected increase in precipitation and for precipitation-wind paradox have been discussed. The surface temperature over Asian landmass increases in pre-monsoon months due to global warming and heat low over north-west India intensifies. The dipole snow configuration over Eurasian continent strengthens in warmer atmosphere which is conducive for enhancement in precipitation over Indian landmass. The increase in precipitation is mainly contributed by the substantial increase in water vapor content in the atmosphere. No notable changes have been projected in the El Nino-Monsoon relationship.

  6. Intensification and deepening of the Arabian Sea Oxygen Minimum Zone in response to increase in Indian monsoon wind intensity

    Science.gov (United States)

    Lachkar, Zouhair; Smith, Shafer; Levy, Marina

    2017-04-01

    The decline in oxygen supply to the ocean associated with global warming of sea-surface temperatures is expected to expand the oxygen minimum zones (OMZs). This global trend can be attenuated or amplified by regional processes. In the Arabian Sea, the World's thickest OMZ is highly vulnerable to changes in the Indian monsoon wind. Evidence from paleo records and future climate projections indicate strong variations of the Indian monsoon wind intensity over climatic timescales. Yet, the response of the OMZ to these wind changes remains poorly understood and its amplitude and timescale unexplored. Here, we investigate the impacts of perturbations in Indian monsoon wind intensity (from -50% to +50%) on the size and intensity of the Arabian Sea OMZ, and examine the biogeochemical and ecological implications of these changes. To this end, we conducted a series of eddy-resolving simulations of the Arabian Sea using the Regional Oceanic Modeling System (ROMS) coupled to a nitrogen based Nutrient-Phytoplankton-Zooplankton-Detritus (NPZD) ecosystem model that includes a representation of the O2 cycle. We show that the Arabian Sea productivity increases and its OMZ expands and deepens in response to monsoon wind intensification. These responses are dominated by the perturbation of the summer monsoon wind, whereas the changes in the winter monsoon wind play a secondary role. While the productivity responds quickly and nearly linearly to wind increase (i.e., on a timescale of years), the OMZ response is much slower (i.e., a timescale of decades). Our analysis reveals that the OMZ expansion at depth is driven by increased oxygen biological consumption, whereas its surface weakening is induced by increased lateral ventilation. The enhanced lateral ventilation favors episodic intrusions of oxic waters in the lower epipelagic zone (100-200m) of the western and central Arabian Sea, leading to intermittent expansions of habitats and a more frequent alternation of hypoxic and oxic

  7. The Aerosol-Monsoon Climate System of Asia

    Science.gov (United States)

    Lau, William K. M.; Kyu-Myong, Kim

    2012-01-01

    In Asian monsoon countries such as China and India, human health and safety problems caused by air-pollution are worsening due to the increased loading of atmospheric pollutants stemming from rising energy demand associated with the rapid pace of industrialization and modernization. Meanwhile, uneven distribution of monsoon rain associated with flash flood or prolonged drought, has caused major loss of human lives, and damages in crop and properties with devastating societal impacts on Asian countries. Historically, air-pollution and monsoon research are treated as separate problems. However a growing number of recent studies have suggested that the two problems may be intrinsically intertwined and need to be studied jointly. Because of complexity of the dynamics of the monsoon systems, aerosol impacts on monsoons and vice versa must be studied and understood in the context of aerosol forcing in relationship to changes in fundamental driving forces of the monsoon climate system (e.g. sea surface temperature, land-sea contrast etc.) on time scales from intraseasonal variability (weeks) to climate change ( multi-decades). Indeed, because of the large contributions of aerosols to the global and regional energy balance of the atmosphere and earth surface, and possible effects of the microphysics of clouds and precipitation, a better understanding of the response to climate change in Asian monsoon regions requires that aerosols be considered as an integral component of a fully coupled aerosol-monsoon system on all time scales. In this paper, using observations and results from climate modeling, we will discuss the coherent variability of the coupled aerosol-monsoon climate system in South Asia and East Asia, including aerosol distribution and types, with respect to rainfall, moisture, winds, land-sea thermal contrast, heat sources and sink distributions in the atmosphere in seasonal, interannual to climate change time scales. We will show examples of how elevated

  8. A new criterion for identifying breaks in monsoon conditions over the Indian subcontinent

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar, M.R.; Dessai, U.R.P.

    of July. The quantum of monsoon rainfall also varies from year to year. The monsoon rainfall is not continuous within the life cycle of a monsoon; there are several spells of active, weak and break in monsoon conditions. The summer monsoon months...? to refer different features such as convection and circulation etc. over different regions. Further, the authors have used different durations to refer the break as well as looked them in different months. [4] By analyzing 80 years (1888...

  9. Summer monsoon rainfall prediction for India - Some new ideas

    Digital Repository Service at National Institute of Oceanography (India)

    Varkey, M.J.

    Present methods of forecasting of mean Indian rainfall for summer monsoon season are critically examined. Considering the wide variations in mean seasonal rainfalls (more than 5 to less than 400 cm) and crops in various regions of India...

  10. Transient coupling relationships of the Holocene Australian monsoon

    CERN Document Server

    McRobie, Fiona H; Wyrwoll, Karl-Heinz

    2015-01-01

    The modern-day northwest Australian summer monsoon is dynamically coupled to other regional monsoon systems and inflows from the Indian Ocean, however, the nature of these relationships over longer time scales is uncertain. Previous attempts to evaluate how proxy records from the Indonesian-Australian monsoon region correspond to other records from the Indian and East Asian monsoon regions, as well as to El Ni\\~no-related proxy records, has been qualitative, relying on `curve-fitting' methods. Here, we seek a quantitative approach for identifying coupling relationships between paleoclimate proxy records, employing statistical techniques to compute the interdependence of two paleoclimate time series. We verify the use of complex networks to identify coupling relationships between modern climate indices which correspond to physically-based mechanisms. This method is then extended to a set of paleoclimate proxy records from the Asian, Australasian and South American regions spanning the past 9,000 years. The res...

  11. Air sea interaction during summer monsoon period of 1979

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar, M.R.

    The present study highlights the utility of satellite derived parameters like SST, precipitation, CMV winds in the lower troposphere etc. in supplementing the in-situ observations. This information can lead to a better understanding of the monsoon...

  12. Monsoon regime in the Indian Ocean and zooplankton variability

    Digital Repository Service at National Institute of Oceanography (India)

    Nair, V.R.

    The monsoonal effects on zooplankton lead to characteristic zoogeographic patterns in the open ocean and coastal waters. The evaluation of zooplankton variability in the Indian Ocean is presented in three sections: the open ocean, coastal waters...

  13. Intraseasonal Variability of the Indian Summer Monsoon in the Regional Climate Model COSMO-CLM

    Science.gov (United States)

    Befort, Daniel J.; Leckebusch, Gregor C.; Cubasch, Ulrich

    2015-04-01

    The regional climate model COSMO-CLM driven by ERA-Interim reanalysis data with a spatial resolution of 55km is used to simulate observed features of the intraseasonal variability of the Indian summer monsoon (ISM) during the period 1979 until 2011. One of these features is the northward propagation of the monsoon intraseasonal oscillations. We find, that the temporal evolution of this oscillation between model and observation is in good agreement, but the strength is less well simulated. Additionally, the models capability to simulate observed dry and wet events on a weekly time scale is investigated using the standardized precipitation index. In general, the model is capable to simulate these events with a similar magnitude at the same time, but we find a higher ability for dry compared to wet events. We hypothesize this is related to differences in the atmospheric circulation during dry and wet events. Analyses show, that dry events are characterized by a cyclonic vortex over India as well as an anti-cyclonic vortex over Pakistan region in 500hPa, whereas wet events are characterized by an anti-cyclonic vortex over India, only. It is found that COSMO-CLM has a higher ability to simulate the observed anomalous circulation over Pakistan region compared to observed anomalous circulation patterns over India. Overall, this study shows that the current configuration of COSMO-CLM is able to simulate key features of the intraseasonal variability of the Indian summer monsoon. Thus, under consideration of its limitations, COSMO-CLM is suitable to investigate possible changes of the intraseasonal variability of ISM under changed climate conditions.

  14. Asian monsoon modulation of nonsteady state diagenesis in hemipelagic marine sediments offshore of Japan

    Science.gov (United States)

    Chang, Liao; Bolton, Clara T.; Dekkers, Mark J.; Hayashida, Akira; Heslop, David; Krijgsman, Wout; Kodama, Kazuto; Paterson, Greig A.; Roberts, Andrew P.; Rohling, Eelco J.; Yamamoto, Yuhji; Zhao, Xiang

    2016-11-01

    We have identified millennial-scale variations in magnetic mineral diagenesis from Pacific Ocean sediments offshore of Japan that we correlate with changes in organic carbon burial that were likely driven by Asian monsoon fluctuations. The correlation was determined by identifying offsets between the positions of fossil diagenetic fronts and climatically induced variations in organic carbon burial inferred from magnetic and geochemical analyses. Episodes of intense monsoon activity and attendant sediment magnetic mineral diagenesis also appear to correlate with Heinrich events, which supports the existence of climatic telecommunications between Asia and the North Atlantic region. Several lines of evidence support our conclusions: (1) fluctuations in down-core magnetic properties and diagenetic pyrite precipitation are approximately coeval; (2) localized stratigraphic intervals with relatively stronger magnetic mineral dissolution are linked to enhanced sedimentary organic carbon contents that gave rise to nonsteady state diagenesis; (3) down-core variations in elemental S content provide a proxy for nonsteady state diagenesis that correlate with key records of Asian monsoon variations; and (4) relict titanomagnetite that is preserved as inclusions within silicate particles, rather than secondary authigenic phases (e.g., greigite), dominates the strongly diagenetically altered sediment intervals and are protected against sulfidic dissolution. We suggest that such millennial-scale environmental modulation of nonsteady state diagenesis (that creates a temporal diagenetic filter and relict magnetic mineral signatures) is likely to be common in organic-rich hemipelagic sedimentary settings with rapidly varying depositional conditions. Our work also demonstrates the usefulness of magnetic mineral inclusions for recording important environmental magnetic signals.

  15. The middle Holocene climatic records from Arabia: Reassessing lacustrine environments, shift of ITCZ in Arabian Sea, and impacts of the southwest Indian and African monsoons

    Science.gov (United States)

    Enzel, Yehouda; Kushnir, Yochanan; Quade, Jay

    2015-06-01

    A dramatic increase in regional summer rainfall amount has been proposed for the Arabian Peninsula during the middle Holocene (ca. 9-5 ka BP) based on lacustrine sediments, inferred lake levels, speleothems, and pollen. This rainfall increase is considered primarily the result of an intensified Indian summer monsoon as part of the insolation-driven, northward shift of the boreal summer position of the Inter-Tropical Convergence Zone (ITCZ) to over the deserts of North Africa, Arabia, and northwest India. We examine the basis for the proposed drastic climate change in Arabia and the shifts in the summer monsoon rains, by reviewing paleohydrologic lacustrine records from Arabia. We evaluate and reinterpret individual lake-basin status regarding their lacustrine-like deposits, physiography, shorelines, fauna and flora, and conclude that these basins were not occupied by lakes, but by shallow marsh environments. Rainfall increase required to support such restricted wetlands is much smaller than needed to form and maintain highly evaporating lakes and we suggest that rainfall changes occurred primarily at the elevated edges of southwestern, southern, and southeastern Arabian Peninsula. These relatively small changes in rainfall amounts and local are also supported by pollen and speleothems from the region. The changes do not require a northward shift of the Northern Hemisphere summer ITCZ and intensification of the Indian monsoon rainfall. We propose that (a) latitudinal and slight inland expansion of the North African summer monsoon rains across the Red Sea, and (b) uplifted moist air of this monsoon to southwestern Arabia highlands, rather than rains associated with intensification of Indian summer monsoon, as proposed before, increased rains in that region; these African monsoon rains produced the modest paleo-wetlands in downstream hyperarid basins. Furthermore, we postulate that as in present-day, the ITCZ in the Indian Ocean remained at or near the equator all

  16. Early warnings and missed alarms for abrupt monsoon transitions

    Science.gov (United States)

    Thomas, Z. A.; Kwasniok, F.; Boulton, C. A.; Cox, P. M.; Jones, R. T.; Lenton, T. M.; Turney, C. S. M.

    2015-12-01

    Palaeo-records from China demonstrate that the East Asian Summer Monsoon (EASM) is dominated by abrupt and large magnitude monsoon shifts on millennial timescales, switching between periods of high and weak monsoon rains. It has been hypothesized that over these timescales, the EASM exhibits two stable states with bifurcation-type tipping points between them. Here we test this hypothesis by looking for early warning signals of past bifurcations in speleothem δ18O records from Sanbao Cave and Hulu Cave, China, spanning the penultimate glacial cycle. We find that although there are increases in both autocorrelation and variance preceding some of the monsoon transitions during this period, it is only immediately prior to the abrupt monsoon shift at the penultimate deglaciation (Termination II) that statistically significant increases are detected. To supplement our data analysis, we produce and analyse multiple model simulations that we derive from these data. We find hysteresis behaviour in our model simulations with transitions directly forced by solar insolation. However, signals of critical slowing down, which occur on the approach to a bifurcation, are only detectable in the model simulations when the change in system stability is sufficiently slow to be detected by the sampling resolution of the data set. This raises the possibility that the early warning "alarms" were missed in the speleothem data over the period 224-150 kyr and it was only at the monsoon termination that the change in the system stability was sufficiently slow to detect early warning signals.

  17. A statistically predictive model for future monsoon failure in India

    Science.gov (United States)

    Schewe, Jacob; Levermann, Anders

    2012-12-01

    Indian monsoon rainfall is vital for a large share of the world’s population. Both reliably projecting India’s future precipitation and unraveling abrupt cessations of monsoon rainfall found in paleorecords require improved understanding of its stability properties. While details of monsoon circulations and the associated rainfall are complex, full-season failure is dominated by large-scale positive feedbacks within the region. Here we find that in a comprehensive climate model, monsoon failure is possible but very rare under pre-industrial conditions, while under future warming it becomes much more frequent. We identify the fundamental intraseasonal feedbacks that are responsible for monsoon failure in the climate model, relate these to observational data, and build a statistically predictive model for such failure. This model provides a simple dynamical explanation for future changes in the frequency distribution of seasonal mean all-Indian rainfall. Forced only by global mean temperature and the strength of the Pacific Walker circulation in spring, it reproduces the trend as well as the multidecadal variability in the mean and skewness of the distribution, as found in the climate model. The approach offers an alternative perspective on large-scale monsoon variability as the result of internal instabilities modulated by pre-seasonal ambient climate conditions.

  18. Causal evidence between monsoon and evolution of rhizomyine rodents

    Science.gov (United States)

    López-Antoñanzas, Raquel; Knoll, Fabien; Wan, Shiming; Flynn, Lawrence J.

    2015-03-01

    The modern Asian monsoonal systems are currently believed to have originated around the end of the Oligocene following a crucial step of uplift of the Tibetan-Himalayan highlands. Although monsoon possibly drove the evolution of many mammal lineages during the Neogene, no evidence thereof has been provided so far. We examined the evolutionary history of a clade of rodents, the Rhizomyinae, in conjunction with our current knowledge of monsoon fluctuations over time. The macroevolutionary dynamics of rhizomyines were analyzed within a well-constrained phylogenetic framework coupled with biogeographic and evolutionary rate studies. The evolutionary novelties developed by these rodents were surveyed in parallel with the fluctuations of the Indian monsoon so as to evaluate synchroneity and postulate causal relationships. We showed the existence of three drops in biodiversity during the evolution of rhizomyines, all of which reflected elevated extinction rates. Our results demonstrated linkage of monsoon variations with the evolution and biogeography of rhizomyines. Paradoxically, the evolution of rhizomyines was accelerated during the phases of weakening of the monsoons, not of strengthening, most probably because at those intervals forest habitats declined, which triggered extinction and progressive specialization toward a burrowing existence.

  19. Possible role of pre-monsoon sea surface warming in driving the summer monsoon onset over the Bay of Bengal

    Science.gov (United States)

    Li, Kuiping; Liu, Yanliang; Yang, Yang; Li, Zhi; Liu, Baochao; Xue, Liang; Yu, Weidong

    2016-08-01

    Sea surface temperature (SST) reaches its annual maximum just before the summer monsoon onset and collapses soon after in the central areas of the Bay of Bengal (BoB). Here, the impact of the peak in the pre-monsoon SST on triggering the earliest monsoon onset in the BoB is investigated, with a focus on the role they play in driving the first-branch northward-propagating intra-seasonal oscillations (FNISOs) over the equatorial Eastern Indian Ocean (EIO). During the calm pre-monsoon period, sea surface warming in the BoB could increase the surface equivalent potential temperature (θe) in several ways. Firstly, warming of the sea surface heats the surface air through sensible heating, which forces the air temperature to follow the SST. The elevated air surface temperature accounts for 30 % of the surface θe growth. Furthermore, the elevated air temperature raises the water vapor capacity of the surface air to accommodate more water vapor. Constrained by the observation that the surface relative humidity is maintained nearly constant during the monsoon transition period, the surface specific humidity exhibits a significant increase, according to the Clausius-Clapeyron relationship. Budget analysis indicates that the additional moisture is primarily obtained from sea surface evaporation, which also exhibits a weak increasing trend due to the sea surface warming. In this way, it contributes about 70 % to the surface θe growth. The rapid SST increase during the pre-monsoon period preconditions the summer monsoon onset over the BoB through its contributions to significantly increase the surface θe, which eventually establishes the meridional asymmetry of the atmospheric convective instability in the EIO. The pre-established greater convective instability leads to the FNISO convections, and the summer monsoon is triggered in the BoB region.

  20. Monsoon influence on planktic δ18O records from the South China Sea

    Science.gov (United States)

    Wang, Pinxian; Li, Qianyu; Tian, Jun; He, Juan; Jian, Zhimin; Ma, Wentao; Dang, Haowen

    2016-06-01

    While the benthic δ18O records from many South China Sea sites mimic the SPECMAP/LR04 standard, their paired planktic δ18O curves differ by comparable values at negative peaks corresponding to interstadials, especially between MIS 5.1, 5.3, 5.5, 6.5, and 7.3. Similar planktic δ18O records also occur in some other low-latitude oceans under monsoon influence. Because neither temperature nor salinity effects can fully account for the variations of such δ18O records after derivation from the SPECMAP/LR04 standard, variations in the rain water δ18O affected by regional hydroclimate changes are considered to have played an important role. In contrast to the SPECMAP/LR04 standard δ18O curve prevailed by 100-kyr cycles, these regional planktic δ18O curves are distinguished by 20-kyr precession signal, showing partial similarity to the δ18O records of atmospheric oxygen in polar ice-core bubbles and in stalagmite calcite. We speculate that the common features of these three independent δ18O records are indicative of the effect of evolving hydrological cycling driven by monsoon circulation in low latitudes.

  1. Influence of Soil Moisture on the Asian and African Monsoons. Part II: Interannual Variability.

    Science.gov (United States)

    Douville, H.

    2002-04-01

    The relevance of soil moisture (SM) for simulating the interannual climate variability has not been much investigated until recently. Much more attention has been paid on SST anomalies, especially in the Tropics where the El Niño-Southern Oscillation represents the main mode of variability. In the present study, ensembles of atmospheric integrations based on the Action de Recherche Petit Echelle Grande Echelle (ARPEGE) climate model have been performed for two summer seasons: 1987 and 1988, respectively. The aim is to compare the relative impacts of using realistic boundary conditions of SST and SM on the simulated variability of the Asian and African monsoons. Besides control runs with interactive SM, sensitivity tests have been done in which SM is relaxed toward a state-of-the-art SM climatology, either globally or regionally over the monsoon domain. The simulations indicate that the variations of the Asian monsoon between 1987 and 1988 are mainly driven by SST anomalies. This result might be explained by the strong teleconnection with the ENSO and by a weak SM-precipitation feedback over south Asia (Part I of the study). The influence of SM is more obvious over Africa. The model needs both realistic SST and SM boundary conditions to simulate the observed variability of the Sahelian monsoon rainfall. The positive impact of the SM relaxation is not only due to a local mechanism whereby larger surface evaporation leads to larger precipitation. The best results are obtained when the relaxation is applied globally, suggesting that remote SM impacts also contribute to the improved simulation of the precipitation variability. A relationship between the Sahelian rainfall anomalies and the meridional wind anomalies over North Africa points out the possible influence of the Northern Hemisphere midlatitudes. The comparison of the low- and midtropospheric anomalies in the various pairs of experiments indicates that SM anomalies can trigger stationary waves over Europe, and

  2. ON THE PROCESS OF SUMMER MONSOON ONSET OVER EAST ASIA

    Institute of Scientific and Technical Information of China (English)

    陈隆勋; 李薇; 赵平; 陶诗言

    2001-01-01

    Using daily observational rainfall data covered 194 stations of China from 1961 to 1995 and NCEP model analyzed pentad precipitation data of global grid point from 1979 to 1997, the distribution of onset date of rainy season over Asian area from spring to summer is studied in this paper. The analyzed results show that there exist two stages of rainy season onset over East Asian region from spring to summer rainy season onset accompanying subtropical monsoon and tropical monsoon respectively. The former rain belt is mainly formed by the convergence of cold air and the recurved southwesterly flow from western part of subtropical high and westerly flow from the so-called western trough of subtropical region occurring during winter to spring over South Asia. The latter is formed in the process of subtropical monsoon rain belt over inshore regions of South China Sea originally coming from south of Changjiang (Yangtze) River Basin advancing with northward shift of subtropical high after the onset of tropical monsoon over South China Sea. The pre-flood rainy season over South China region then came into mature period and the second peak of rainfall appeared. Meiyu, the rainy season over Changjiang-Huaihe River Basin and North China then formed consequently. The process of summer tropical monsoon onset over South China Sea in 1998 is also discussed in this paper. It indicated that the monsoon during summer tropical monsoon onset over South China Sea is the result of the westerly flow over middle part of South China Sea,which is from the new generated cyclone formed in north subtropical high entering into South China Sea, converged with the tropical southwesterly flow recurved by the intensified cross-equatorial flow.

  3. Asian Monsoon Variability from the Monsoon Asia Drought Atlas (MADA) and Links to Indo-Pacific Climate

    Science.gov (United States)

    Ummenhofer, Caroline; D'Arrigo, Rosanne; Anchukaitis, Kevin; Hernandez, Manuel; Buckley, Brendan; Cook, Edward

    2014-05-01

    Drought patterns across monsoon and temperate Asia over the period 1877-2005 are linked to Indo-Pacific climate variability associated with the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). Using the Monsoon Asia Drought Atlas (MADA) composed of a high-resolution network of hydroclimatically sensitive tree-ring records with a focus on the June-August months, spatial drought patterns during El Niño and IOD events are assessed as to their agreement with an instrumental drought index and consistency in the drought response amongst ENSO/IOD events. Spatial characteristics in drought patterns are related to regional climate anomalies over the Indo-Pacific basin, using reanalysis products, including changes in the Asian monsoon systems, zonal Walker circulation, moisture fluxes, and precipitation. A weakening of the monsoon circulation over the Indian subcontinent and Southeast Asia during El Niño events, along with anomalous subsidence over monsoon Asia and reduced moisture flux, is reflected in anomalous drought conditions over India, Southeast Asia and Indonesia. When an IOD event co-occurs with an El Niño, severe drought conditions identified in the MADA for Southeast Asia, Indonesia, eastern China and central Asia are associated with a weakened South Asian monsoon, reduced moisture flux over China, and anomalous divergent flow and subsidence over Indonesia. Variations in the strength of the South Asian monsoon can also be linked to the Strange Parallels Drought (1756-1768) affecting much of Southeast Asia and the Indian subcontinent in the mid-18th Century. Large-scale climate anomalies across the wider region during years with an anomalously strengthened/weakened South Asian monsoon are discussed with implications for severe droughts prior to the instrumental period. Insights into the relative influences of Pacific and Indian Ocean variability for Asian monsoon climate on interannual to decadal and longer timescales, as recorded in the

  4. Transport pathways of carbon monoxide in the Asian summer monsoon diagnosed from Model of Ozone and Related Tracers (MOZART)

    Science.gov (United States)

    Park, Mijeong; Randel, William J.; Emmons, Louisa K.; Livesey, Nathaniel J.

    2009-04-01

    Satellite observations of tropospheric chemical constituents (such as carbon monoxide, CO) reveal a persistent maximum in the upper troposphere-lower stratosphere (UTLS) associated with the Asian summer monsoon anticyclone. Diagnostic studies suggest that the strong anticyclonic circulation acts to confine air masses, but the sources of pollution and transport pathways to altitudes near the tropopause are the subject of debate. Here we use the Model for Ozone and Related Tracers 4 (MOZART-4) global chemistry transport model, driven by analyzed meteorological fields, to study the source and transport of CO in the Asian monsoon circulation. A MOZART-4 simulation for one summer is performed, and results are compared with satellite observations of CO from the Aura Microwave Limb Sounder and the Atmospheric Chemistry Experiment Fourier Transform Spectrometer. Overall, good agreement is found between the modeled and observed CO in the UTLS, promoting confidence in the model simulation. The model results are then analyzed to understand the sources and transport pathways of CO in the Asian monsoon region, and within the anticyclone in particular. The results show that CO is transported upward by monsoon deep convection, with the main surface sources from India and Southeast Asia. The uppermost altitude of the convective transport is ˜12 km, near the level of main deep convective outflow, and much of the CO is then advected in the upper troposphere northeastward across the Pacific Ocean and southwestward with the cross-equatorial Hadley flow. However, some of the CO is also advected vertically to altitudes near the tropopause (˜16 km) by the large-scale upward circulation on the eastern side of the anticyclone, and this air then becomes trapped within the anticyclone (to the west of the convection, extending to the Middle East). Within the anticyclone, the modeled CO shows a relative maximum near 15 km, in good agreement with observations.

  5. East China Sea δ18O Record Detects Millennial-Scale Changes in the East Asian Summer Monsoon

    Science.gov (United States)

    Gleeman, E.; Clemens, S. C.; Lawman, A. E.; Kubota, Y.; Holbourn, A. E.; Martin, A.

    2015-12-01

    The East Asian Summer Monsoon (EASM) brings heavy summer rainfall to some of Asia's most densely-populated areas, impacting agricultural production and water resources. Sediment cores were recovered from International Ocean Drilling Program Site U1429 in the East China Sea (31° 37.04' N, 128° 59.50' E, 732 mbsl). This location receives runoff from the Yangtze River, which serves as a major drainage system for monsoon-induced precipitation. Hence, the δ18O record of planktonic foraminifera at Site U1429 reflects changes in regional, monsoon-driven salinity. The top 100 meters of core at Site U1429 were sampled at a preliminary resolution of 15 cm and processed to isolate the planktonic foraminifer Globigerinoides ruber for δ18O mass spectrometry analyses. Abrupt, millennial-scale regional climate variability in the EASM and its linkage to orbital forcings have been reconstructed using stratigraphic analysis of δ18O. The sub-orbital scale structure of the δ18O record over the past 400 kyr matches the structures of both the composite speleothem δ18O from eastern China (Sanbao and Hulu caves) and the planktonic δ18O record from northern South China Sea Site 1146. The similarities between these δ18O records indicate a strong regional response to monsoon forcing. Removal of the temperature component of the δ18O signal by using Mg/Ca (G. ruber) paleothermometry will provide a record of changes in the δ18O composition of seawater in response to Yangtze River runoff.

  6. Modelling Monsoons: Understanding and Predicting Current and Future Behaviour

    Energy Technology Data Exchange (ETDEWEB)

    Turner, A; Sperber, K R; Slingo, J M; Meehl, G A; Mechoso, C R; Kimoto, M; Giannini, A

    2008-09-16

    The global monsoon system is so varied and complex that understanding and predicting its diverse behaviour remains a challenge that will occupy modellers for many years to come. Despite the difficult task ahead, an improved monsoon modelling capability has been realized through the inclusion of more detailed physics of the climate system and higher resolution in our numerical models. Perhaps the most crucial improvement to date has been the development of coupled ocean-atmosphere models. From subseasonal to interdecadal timescales, only through the inclusion of air-sea interaction can the proper phasing and teleconnections of convection be attained with respect to sea surface temperature variations. Even then, the response to slow variations in remote forcings (e.g., El Nino-Southern Oscillation) does not result in a robust solution, as there are a host of competing modes of variability that must be represented, including those that appear to be chaotic. Understanding the links between monsoons and land surface processes is not as mature as that explored regarding air-sea interactions. A land surface forcing signal appears to dominate the onset of wet season rainfall over the North American monsoon region, though the relative role of ocean versus land forcing remains a topic of investigation in all the monsoon systems. Also, improved forecasts have been made during periods in which additional sounding observations are available for data assimilation. Thus, there is untapped predictability that can only be attained through the development of a more comprehensive observing system for all monsoon regions. Additionally, improved parameterizations - for example, of convection, cloud, radiation, and boundary layer schemes as well as land surface processes - are essential to realize the full potential of monsoon predictability. Dynamical considerations require ever increased horizontal resolution (probably to 0.5 degree or higher) in order to resolve many monsoon features

  7. The Influence of Regional SSTs on the Interdecadal Shift of the East Asian Summer Monsoon

    Institute of Scientific and Technical Information of China (English)

    FU Jianjian; LI Shuanglin

    2013-01-01

    East Asia has experienced a significant interdecadal climate shift since the late 1970s.This shift was accompanied by a decadal change of global SST.Previous studies have suggested that the decadal shift of global SST background status played a substantial role in such a climatic shift.However,the individual roles of different regional SSTs remain unclear.In this study,we investigated these roles using ensemble experiments of an atmospheric general circulation model,GFDL (Geophysical Fluid Dynamics Laboratory) AM2.Two kinds of ensembles were performed.The first was a control ensemble in which the model was driven with the observed climatological SSTs.The second was an experimental ensemble in which the model was driven with the observed climatological SSTs plus interdecadal SST background shifts in separate ocean regions.The results suggest that the SST shift in the tropics exerted more important influence than those in the extratropics,although the latter contribute to the shift modestly.The variations of summer monsoonal circulation systems,including the South Asian High,the West Pacific Subtropical High,and the lower-level air flow,were analyzed.The results show that,in comparison with those induced by extratropical SSTs,the shifts induced by tropical SSTs bear more similarity to the observations and to the simulations with global SSTs prescribed.In particular,the observed SST shift in the tropical Pacific Ocean,rather than the Indian Ocean,contributed significantly to the shift of East Asian summer monsoon since the 1970s.

  8. Trace gas transport out of the Indian Summer Monsoon

    Science.gov (United States)

    Tomsche, Laura; Pozzer, Andrea; Zimmermann, Peter; Parchatka, Uwe; Fischer, Horst

    2016-04-01

    The trace gas transport out of the Indian summer monsoon was investigated during the aircraft campaign OMO (Oxidation Mechanism Observations) with the German research aircraft HALO (High Altitude and Long Range Research Aircraft) in July/August 2015. HALO was based at Paphos/Cyprus and also on Gan/Maledives. Flights took place over the Mediterranean Sea, the Arabian Peninsula and the Arabian Sea. In this work the focus is on the distribution of carbon monoxide (CO) and methane (CH4) in the upper troposphere. They were measured with the laser absorption spectrometer TRISTAR on board of HALO. During the Indian summer monsoon strong convection takes place over India and the Bay of Bengal. In this area the population is high accompanied by many emission sources e.g. wetlands and cultivation of rice. Consequently the boundary layer is polluted containing high concentrations of trace gases like methane and carbon monoxide. Due to vertical transport these polluted air masses are lifted to the upper troposphere. Here they circulate with the so called Asian monsoon anticyclone. In the upper troposphere polluted air masses lead to a change in the chemical composition thus influence the chemical processes. Furthermore the anticyclone spreads the polluted air masses over a larger area. Thus the outflow of the anticyclone in the upper troposphere leads to higher concentrations of trace gases over the Arabian Sea, the Arabian Peninsula and also over the eastern part of North Africa and the eastern part of the Mediterranean Sea. During OMO higher concentrations of methane and carbon monoxide were detected at altitudes between 11km and 15km. The highest measured concentrations of carbon monoxide and methane were observed over Oman. The CO concentration in the outflow of the monsoon exceeds background levels by 10-15ppb. However the enhancement in the concentration is not obviously connected to the monsoon due to the natural variability in the troposphere. The enhancement in the

  9. The contrasting features of Asian summer monsoon during surplus and deficient rainfall over India

    Science.gov (United States)

    Raju, P. V. S.; Mohanty, U. C.; Rao, P. L. S.; Bhatla, R.

    2002-12-01

    An endeavour is made to distinguish the mean summer monsoon features during surplus and deficient monsoon seasons. Based on all-India summer monsoon rainfall, over 42 years (1958-99), seven surplus and ten deficient monsoon seasons are identified. Making use of daily averaged (00 Z and 12 Z) reanalysis data sets from the National Center for Environmental Prediction-National Center for Atmospheric Research for the corresponding surplus and deficient monsoon seasons, the mean circulation characteristics and large-scale energetics are examined.The circulation features denote that the cross equatorial flow, low-level jet and tropical easterly jet are stronger during a surplus monsoon. Further, strong Tibetan anticyclonic flow characterizes a surplus monsoon. The large-scale balances of kinetic energy, heat and moisture show a significantly large quantity of diabatic heating, adiabatic generation of kinetic energy, and horizontal convergence of heat and moisture during the surplus monsoon season compared with the deficient state. The regions with statistically significant difference between surplus and deficient monsoon seasons are delineated by a Student's t-test at the 95% confidence level. The remarkable aspect noticed in this study is that the Arabian Sea branch of the monsoon circulation is more vigorous during a surplus monsoon season, whereas the eastern Bay of Bengal branch is stronger during a deficient monsoon. The various large-scale budget terms of kinetic energy, heat and moisture are found to be consistent and in agreement with the seasonal monsoon activity over India.

  10. Investigation of summer monsoon rainfall variability in Pakistan

    Science.gov (United States)

    Hussain, Mian Sabir; Lee, Seungho

    2016-08-01

    This study analyzes the inter-annual and intra-seasonal rainfall variability in Pakistan using daily rainfall data during the summer monsoon season (June to September) recorded from 1980 to 2014. The variability in inter-annual monsoon rainfall ranges from 20 % in northeastern regions to 65 % in southwestern regions of Pakistan. The analysis reveals that the transition of the negative and positive anomalies was not uniform in the investigated dataset. In order to acquire broad observations of the intra-seasonal variability, an objective criterion, the pre-active period, active period and post-active periods of the summer monsoon rainfall have demarcated. The analysis also reveals that the rainfall in June has no significant contribution to the increase in intra-seasonal rainfall in Pakistan. The rainfall has, however, been enhanced in the summer monsoon in August. The rainfall of September demonstrates a sharp decrease, resulting in a high variability in the summer monsoon season. A detailed examination of the intra-seasonal rainfall also reveals frequent amplitude from late July to early August. The daily normal rainfall fluctuates significantly with its maximum in the Murree hills and its minimum in the northwestern Baluchistan.

  11. Global monsoon precipitation responses to large volcanic eruptions.

    Science.gov (United States)

    Liu, Fei; Chai, Jing; Wang, Bin; Liu, Jian; Zhang, Xiao; Wang, Zhiyuan

    2016-04-11

    Climate variation of global monsoon (GM) precipitation involves both internal feedback and external forcing. Here, we focus on strong volcanic forcing since large eruptions are known to be a dominant mechanism in natural climate change. It is not known whether large volcanoes erupted at different latitudes have distinctive effects on the monsoon in the Northern Hemisphere (NH) and the Southern Hemisphere (SH). We address this issue using a 1500-year volcanic sensitivity simulation by the Community Earth System Model version 1.0 (CESM1). Volcanoes are classified into three types based on their meridional aerosol distributions: NH volcanoes, SH volcanoes and equatorial volcanoes. Using the model simulation, we discover that the GM precipitation in one hemisphere is enhanced significantly by the remote volcanic forcing occurring in the other hemisphere. This remote volcanic forcing-induced intensification is mainly through circulation change rather than moisture content change. In addition, the NH volcanic eruptions are more efficient in reducing the NH monsoon precipitation than the equatorial ones, and so do the SH eruptions in weakening the SH monsoon, because the equatorial eruptions, despite reducing moisture content, have weaker effects in weakening the off-equatorial monsoon circulation than the subtropical-extratropical volcanoes do.

  12. Water characteristics, mixing and circulation in the Bay of Bengal during southwest monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Murty, V.S.N.; Sarma, Y.V.B.; Rao, D.P.; Murty, C.S.

    Influence of the freshwater influx, the wind forcing and the Indian Ocean monsoon drift current on the property distributions and the circulation in the Bay of Bengal during southwest monsoon has been quantified. At the head of the Bay, waters...

  13. High-resolution peat records for Holocene monsoon history in the eastern Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    YU; Xuefeng; ZHOU; Weijian; Lars; G.Franzen; XIAN; Feng; CHENG; Peng; A.J.; Tim; Jull

    2006-01-01

    The variations of summer and winter monsoons during the Holocene in the eastern Tibetan Plateau are shown to follow two basic models based on the reliable dating and high-resolution monsoon proxies determinations, one being a synchronous model in that both summer and winter monsoons are strengthening or decreasing, and the other to form a complementary pattern. These two different patterns evenly interact with each other on different time scales and together compose a complicated monsoon climatic model in this region. The climatic condition integrated by winter and summer monsoons is synchronous to the global pattern, which also shows the instability of the Holocene climate on centennial-millennial timescale. The abrupt monsoon event in about 6.2 ka cal.BP is much more severe than that in ca. 8.0 ka cal. BP, which indicates the regional character of the Asian monsoon and that the Asian monsoon climate is indeed a window on the global climate system.

  14. Environmental status of groundwater affected by chromite ore processing residue (COPR) dumpsites during pre-monsoon and monsoon seasons.

    Science.gov (United States)

    Matern, Katrin; Weigand, Harald; Singh, Abhas; Mansfeldt, Tim

    2017-02-01

    Chromite ore processing residue (COPR) is generated by the roasting of chromite ores for the extraction of chromium. Leaching of carcinogenic hexavalent chromium (Cr(VI)) from COPR dumpsites and contamination of groundwater is a key environmental risk. The objective of the study was to evaluate Cr(VI) contamination in groundwater in the vicinity of three COPR disposal sites in Uttar Pradesh, India, in the pre-monsoon and monsoon seasons. Groundwater samples (n = 57 pre-monsoon, n = 70 monsoon) were taken in 2014 and analyzed for Cr(VI) and relevant hydrochemical parameters. The site-specific ranges of Cr(VI) concentrations in groundwater were <0.005 to 34.8 mg L(-1) (Rania), <0.005 to 115 mg L(-1) (Chhiwali), and <0.005 to 2.0 mg L(-1) (Godhrauli). Maximum levels of Cr(VI) were found close to the COPR dumpsites and significantly exceeded safe drinking water limits (0.05 mg L(-1)). No significant dependence of Cr(VI) concentration on monsoons was observed.

  15. 基于动力反演方法的亚洲季风机制探讨%The Exploring of the Asian Monsoon Driving Mechanism Based on Dynamical Inversion Method

    Institute of Scientific and Technical Information of China (English)

    李玉霞; 林振山; 刘会玉

    2015-01-01

    The monsoon driving mechanism is a hot spot in the quaternary global change research, where the in-ternational academia has been paid close attention. As early as in 1686, Halley has put forward that the heat dif-ferences caused by the sun between the marine and terrestrial bring about the monsoon. With the deepening of the research, different driving factors are proposed one after another, such as the solar activity, the mechanical force and thermal effect of the Qinghai-Tibet Plateau, ENSO, the temperature of the south and north poles, the migration of the intertropical convergence zone, the thermohaline circulation and so on in which the solar activ-ity and the thermohaline circulation are widely accepted. Cave stalagmites oxygen isotope is one of the most important high-resolution alternative indexes of palaeoclimate. Especially in the region strongly affected by the monsoon, the change of the values of stalagmiteδ18O is often taken as the index of ancient monsoon intensi-ty. The Asian monsoon is an important part of the global climate system. Usually the Asian monsoon can be di-vided into East Asia monsoon and Indian monsoon, but the two monsoon regions have no clear boundary. So it is hard to verdict which monsoon the stalagmite collected from this convergence zone represents. Dongge cave is just located in the convergence zone, as is mentioned above,and which monsoon the stalagmiteδ18O value of Dongge Cave represents is still controversial. By means of the dynamic inversion analysis of the Asian mon-soon, the following results are obtained:1) The stalagmitesδ18O value of Dongge Cave is more likely to repre-sent the Indian monsoon. The Indian monsoon system is a complex nonlinear dynamic system driven by the Antarctic temperature and other factors. 2) The solar activity plays a negative feedback stabilizing role in the Indian monsoon system. The stronger the solar activity is, the weaker the stabilization role it plays will be. The temperature of the

  16. The once and future pulse of Indian monsoonal climate

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, K.K.; Patwardhan, S.K.; Goswami, B.N. [Indian Institute of Tropical Meteorology, Pune (India); Kamala, K. [Universiti Pierre et Marie Curie, LOCEAN-IPSL, Paris (France); Rajagopalan, Balaji [University of Colorado, Boulder, CO (United States); Hoerling, Martin P.; Eischeid, Jon K. [NOAA/ESRL/PSD, Boulder, CO (United States); Srinivasan, G. [RIMES, Pathunthani (Thailand); Nemani, Ramakrishna [NASA-Ames Research Center, Moffett Field, CA (United States)

    2011-06-15

    We present a comprehensive assessment of the present and expected future pulse of the Indian monsoon climate based on observational and global climate model projections. The analysis supports the view that seasonal Indian monsoon rains in the latter half of the 21th century may not be materially different in abundance to that experienced today although their intensity and duration of wet and dry spells may change appreciably. Such an assessment comes with considerable uncertainty. With regard to temperature, however, we find that the Indian temperatures during the late 21st Century will very likely exceed the highest values experienced in the 130-year instrumental record of Indian data. This assessment comes with higher confidence than for rainfall because of the large spatial scale driving the thermal response of climate to greenhouse gas forcing. We also find that monsoon climate changes, especially temperature, could heighten human and crop mortality posing a socio-economic threat to the Indian subcontinent. (orig.)

  17. An East Asian Monsoon in the Mid-Pliocene

    Institute of Scientific and Technical Information of China (English)

    YAN Qing; ZHANG Zhong-Shi; GAO Yong-Qi

    2012-01-01

    In this study, the authors simulate the East Asian climate changes in the mid-Pliocene (~3.3 to 3.0 Ma BP) with the Community Atmosphere Model version 3.1 (CAM3.1) and compare the simulated East Asian monsoon with paleoclimate data. The simulations show an obvious warming pattern in East Asia in the mid-Pliocene compared with the pre-industrial climate, with surface air temperature increasing by 0.5 4.0°C. In the warm mid-Pliocene simulation, the East Asian Summer Monsoon (EASM) becomes stronger, while the East Asian Winter Monsoon (EAWM) is similar relative to the pre-industrial climate. Compared with the paleoclimate data, our simulations depict the intensified EASM well but cannot reproduce the weakened EAWM. This model-data discrepancy may be attributed to the uncertainty in the reconstructed mid-Pliocene sea surface temperature.

  18. Effects of increased CO{sub 2} levels on monsoons

    Energy Technology Data Exchange (ETDEWEB)

    Cherchi, Annalisa; Masina, Simona; Navarra, Antonio [Centro Euro-Mediterraneo per i Cambiamenti Climatici and Istituto Nazionale di Geofisica e Vulcanologia, Bologna (Italy); Alessandri, Andrea [Centro Euro-Mediterraneo per i Cambiamenti Climatici, Bologna (Italy)

    2011-07-15

    Increased atmospheric carbon dioxide concentration provided warmer atmospheric temperature and higher atmospheric water vapor content, but not necessarily more precipitation. A set of experiments performed with a state-of-the-art coupled general circulation model forced with increased atmospheric CO{sub 2} concentration (2, 4 and 16 times the present-day mean value) were analyzed and compared with a control experiment to evaluate the effect of increased CO{sub 2} levels on monsoons. Generally, the monsoon precipitation responses to CO{sub 2} forcing are largest if extreme concentrations of carbon dioxide are used, but they are not necessarily proportional to the forcing applied. In fact, despite a common response in terms of an atmospheric water vapor increase to the atmospheric warming, two out of the six monsoons studied simulate less or equal summer mean precipitation in the 16 x CO{sub 2} experiment compared to the intermediate sensitivity experiments. The precipitation differences between CO{sub 2} sensitivity experiments and CTRL have been investigated specifying the contribution of thermodynamic and purely dynamic processes. As a general rule, the differences depending on the atmospheric moisture content changes (thermodynamic component) are large and positive, and they tend to be damped by the dynamic component associated with the changes in the vertical velocity. However, differences are observed among monsoons in terms of the role played by other terms (like moisture advection and evaporation) in shaping the precipitation changes in warmer climates. The precipitation increase, even if weak, occurs despite a weakening of the mean circulation in the monsoon regions (''precipitation-wind paradox''). In particular, the tropical east-west Walker circulation is reduced, as found from velocity potential analysis. The meridional component of the monsoon circulation is changed as well, with larger (smaller) meridional (vertical) scales. (orig.)

  19. Teleconnections between Indian monsoon and Sahel rainfall and the Mediterranean

    Science.gov (United States)

    Raicich, Fabio; Pinardi, Nadia; Navarra, Antonio

    2003-02-01

    The teleconnections with Indian monsoon and Sahel rainfall indices are investigated here on an interannual time scale in terms of meteorological and marine dynamics over the Mediterranean area. Sea-level pressure from gridded data sets and from individual stations, together with sea-level data from stations all around the Mediterranean coastlines, are used.In summer (July-August-September, JAS) the sea-level pressure field over the eastern Mediterranean anticorrelates with the Indian monsoon index (correlation coefficient C = -0.5 on average). A Mediterranean pressure index (MPI), defined as the standardized difference between sea-level atmospheric pressure at Mersa Matruh (southeastern Mediterranean) and Marseille (northwestern Mediterranean) stations, anticorrelates with Indian monsoon index even more (C = -0.68). The MPI is proportional to the mean geostrophic surface flow field across an imaginary line joining the two stations and turns out to be significantly correlated with the meridional wind component over the eastern Mediterranean, known as the low-level Etesian wind regime. This wind regime represents the inflow surface field into the African inter-tropical convergence zone and, therefore, has an association with the Indian monsoon regime. The ocean response, evident by sea-level anomalies at coastal stations, shows a maximum anticorrelation with Indian monsoon index in late summer and autumn (September-October-November, SON).The Sahel index anticorrelates with sea-level pressure, with the maximum absolute value in June-July-August. This may be interpreted as a tendency of the Mediterranean sea-level pressure anomalies to precede those of Sahel precipitation, which is characterized by maximum rainfall in July-September. The MPI anticorrelates with Sahel index during and before JAS, indicating that the Etesian wind regime intensity is connected to Sahel rainfall. The sea level again anticorrelates with the Sahel index, with the maximum absolute value in

  20. Asian Summer Monsoon and its Associated Rainfall Variability in Thailand

    Directory of Open Access Journals (Sweden)

    Atsamon Limsakul

    2010-07-01

    Full Text Available The Asian monsoon is an important component of the Earth's climate. Its associated rainfall variability is a crucial fac¬tor for Thailand's socio-economic development, water resources and agricultural management. An analysis shows that the Thailand rainfall annual cycle is in phase with the Indian summer monsoon (ISM and the western North Pacific summer monsoon (WNPSM. On the basis of the Empirical Orthogonal Function (EOF analysis, the dominant spatial-temporal interannual variability in summer monsoon rainfall (Jun.-Sep. during 1975-2006 could be explained by the first two EOF modes, accounting for 34% of the total variance. The EOF1 was spatially dominated by strong positive signals in the central and east, whereas the EOF2 exhibited dipole variability. The coefficient time series of EOF1 significantly correlated posi¬tively with ISM index, but negatively with WNPSM index. The results suggest that summer monsoon rainfall in Thailand is higher (lower than normal during the strengthening (weakening of ISM. In contrast, rainfall in the north-east (central is surplus (deficit during the strengthening (weakening of WNPSM. These findings imply that, on an interannual time scale, ISM and WNPSM exert their influence to a different extent on summer monsoon rainfall in Thailand. A clear picture of linking mechanisms and interactions with another climate mode in the Indo-Pacific sector needs to be understood. This knowledge is essential for effectively adapting to climate-related hazards and rainfall extremes and for better management of water resource and agriculture in Thailand, especially under current/future warming conditions.

  1. A new index to describe the tropical Asian summer monsoon

    Institute of Scientific and Technical Information of China (English)

    XU ZhongFeng; FU CongBin; QIAN YongFu

    2009-01-01

    We define a new monsoon index (MV) as the product of relative vorticity and equivalent potential tem-perature using the long-term NCEP/NCAR reanalysis data.The MV index provides new insights into the intraseasonal and interannual variabilities of the broad-scale tropical Asian summer monsoon (TASM),including the South Asian summer monsoon (SASM) and the South China Sea summer monsoon (SCSSM).On the intraseasonal timescale,the pentad-to-pentad MV index bears a close relationship to the broad-scale rainfall in the TASM regions.Among 29 summers from 1979 to 2007,in 23/27 summers the correlation coefficients are higher than 0.7 in the SASM/SCSSM region.However,in fewer than 9 summers,the correlations between the broad-scale rainfall and the existing circulation indices are higher than 0.7.On the interannual timescale,various existing SASM circulation indices are moderately or well correlated with all-India summer monsoon rainfall,whereas their correlations with broad-scale SASM rainfall are weak.In contrast,the summer mean MV index correlates well with the broad-scale SASM rainfall and all-India summer monsoon rainfall (correlation of 0.73 and 0.65,respectively).In the SCSSM region,the summer mean MV index also bears a close relationship to the SCSSM rainfall,al-though some discrepancies exist during certain years.The composite strong TASM shows a stronger low-tropospheric low pressure in association with the enhanced westerly winds and moisture transfer,stronger convection,and upper-tropospheric easterly winds,which indicate that the MV index can well capture the features of TASM.

  2. A new index to describe the tropical Asian summer monsoon

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    We define a new monsoon index (MV) as the product of relative vorticity and equivalent potential temperature using the long-term NCEP/NCAR reanalysis data. The MV index provides new insights into the intraseasonal and interannual variabilities of the broad-scale tropical Asian summer monsoon (TASM), including the South Asian summer monsoon (SASM) and the South China Sea summer monsoon (SCSSM). On the intraseasonal timescale, the pentad-to-pentad MV index bears a close relationship to the broad-scale rainfall in the TASM regions. Among 29 summers from 1979 to 2007, in 23/27 summers the correlation coefficients are higher than 0.7 in the SASM/SCSSM region. However, in fewer than 9 summers, the correlations between the broad-scale rainfall and the existing circulation indices are higher than 0.7. On the interannual timescale, various existing SASM circulation indices are moderately or well correlated with all-India summer monsoon rainfall, whereas their correlations with broad-scale SASM rainfall are weak. In contrast, the summer mean MV index correlates well with the broad-scale SASM rainfall and all-India summer monsoon rainfall (correlation of 0.73 and 0.65, respectively). In the SCSSM region, the summer mean MV index also bears a close relationship to the SCSSM rainfall, although some discrepancies exist during certain years. The composite strong TASM shows a stronger low-tropospheric low pressure in association with the enhanced westerly winds and moisture transfer, stronger convection, and upper-tropospheric easterly winds, which indicate that the MV index can well capture the features of TASM.

  3. Characteristics of Summertime Circulation Patterns for Southern Taiwan's Monsoon Rainfall from July to September

    Directory of Open Access Journals (Sweden)

    Ken-Chung Ko and Yi-Shuan Tzeng

    2013-01-01

    Full Text Available This study documents the circulation features associated with summer monsoon rainfall over southern Taiwan from July through September over the period 1974 - 2001. Four types of monsoon systems, Monsoon I, I-TC, II and II-TC, are identified based on the daily rainfall data of 4 observational stations over southern Taiwan and the daily wind direction data of Lanyu. The total rainfall amount of Monsoon I and I-TC is much greater than that for Monsoon II and II-TC because the former two have more moisture. Monsoon I is characterized by a strong southwesterly flow over southern Taiwan due to the tightening of the pressure gradient between the monsoon trough and subtropical high over the western North Pacific. The Monsoon I-TC pattern exhibits a deep monsoon trough along with an anomalous cyclone near the East China Sea; this pattern drives a large volume of moisture that causes heavy rainfall over southern Taiwan. The circulation patterns of Monsoon I and I-TC resemble the flow pattern during the Mei-Yu or _ _ season from May through mid-July. The Monsoon II pattern reveals a trough south of Taiwan and accompanied by a strong ridge north to it. The convection is located near the southern flank of the monsoon trough. The circulation pattern of Monsoon II-TC yields a deep trough south of the westward protruding subtropical ridge. Additionally, the Monsoon II-TC is less significant because of the wide variety of the TC locations. The Monsoon II and II-TC patterns are similar to the Pacific-Japan (PJ pattern that can affect weather in the East Asian summer monsoon area.

  4. A Holistic View of the Coupled Monsoon System

    Science.gov (United States)

    Webster, P. J.

    2008-12-01

    The basic dynamical constraint on both the atmospheric and oceanic components of the monsoon is the strong cross-equatorial pressure gradient (CEPG). The CEPG is positive and strongest in the lower troposphere during the boreal summer and weakest and negative in the boreal winter. Counter gradients exist at higher elevations. The CEPG is a slowly varying field set up by land-sea differences, convective heating and the seasonal cycle of sea-surface temperature. The dynamic response to this evolving CEPG creates the seasonal structure of the ocean and the atmosphere and determines how the monsoon system will respond to forcing from outside the system. It determines the mode of interannual variability of the system. The CEPG drives a cross-equatorial flow that gains moisture through evaporation. Strong latent heat release occurs in littoral seas and land areas during the summer and to the south of the equator during winter creating net cross-equatorial heat fluxes from the winter to summer hemispheres. However, the cross- equatorial wind fields, so generated, cause an Ekman heat transport from the winter to the summer hemisphere. The net flux is large with a seasonal amplitude of about 2 PW. This almost matches the net atmospheric heat transport, but with reversed sign. For example, the oceanic heat flux is sufficient to reduce the north Indian Ocean upper temperature by 1-2C during summer and warm it by a comparable amount during winter. The net effect is to reduce the vigor of the atmospheric monsoon. To a large degree, the couple ocean-atmosphere system is self-regulated and closed system. Occasional outside influences (ENSO, anomalous springtime snow cover etc.) influence the monsoon. For example there is evidence that El Nino (La Nina) is associated with a weak (strong) monsoon. But a strong (weak) monsoon creates a stronger (weaker) cross-equatorial flow and an enhanced (reduced) oceanic heat flux to the winter hemisphere. In this manner, the system returns to

  5. Hydrography of the eastern Arabian Sea during summer monsoon 2002

    Digital Repository Service at National Institute of Oceanography (India)

    Shankar, D.; Shenoi, S.S.C.; Nayak, R.K.; Vinayachandran, P.N.; Nampoothiri, G.S.; Almeida, A.M.; Michael, G.S.; RameshKumar, M.R.; Sundar, D.; Sreejith, O.P.

    (figure 10), unlike in the Lakshadweep Sea before the onset of the summer monsoon (Durand et al 2004; Shenoi et al 2004, 2005a; Shankar et al 2004). The 10 cm rain event during SK-179 caused but a 0.2openbulletCfallintemper- ature, comparable... in the Lakshadweep Sea before the onset of the summer monsoon (Durand et al 2004; Shenoi et al 2004, 2005a). Variability in the salinity field was not confined to the surface layers, but was evident throughout the depth range of the observations. The high- salinity...

  6. Late quaternary variability of the Arabian Sea monsoon and oxygen minimum zone

    NARCIS (Netherlands)

    Reichart, Gert-Jan

    1997-01-01

    The Monsoon Among the first Europeans observing the Asiatic monsoon was Alexander the Great during his campaign to the mouth of the Indus (325 B.C.). The oldest known records of the Arabian Sea monsoonal climate, however, are shipping documents, dated about 2300 B.C., which refer to the use of the s

  7. Late Miocene-Pliocene Asian monsoon intensification linked to Antarctic ice-sheet growth

    NARCIS (Netherlands)

    Ao, H.; Roberts, A.P.; Dekkers, M.J.|info:eu-repo/dai/nl/073463744; Liu, X.; Rohling, E.J.; Shi, Z.; An, Z.; Zhao, X.

    2016-01-01

    Environmental conditions in one of Earth's most densely populated regions, East Asia, are dominated by the monsoon. While Quaternary monsoon variability is reasonably well understood, pre-Quaternary monsoon variability and dynamics remain enigmatic. In particular, little is known about potential rel

  8. Rainfall analysis for Indian monsoon region using the merged rain gauge observations and satellite estimates: Evaluation of monsoon rainfall features

    Indian Academy of Sciences (India)

    S K Roy Bhowmik; Ananda K Das

    2007-06-01

    Objective analysis of daily rainfall at the resolution of 1° grid for the Indian monsoon region has been carried out merging dense land rainfall observations and INSAT derived precipitation estimates. This daily analysis, being based on high dense rain gauge observations was found to be very realistic and able to reproduce detailed features of Indian summer monsoon. The inter-comparison with the observations suggests that the new analysis could distinctly capture characteristic features of the summer monsoon such as north–south oriented belt of heavy rainfall along the Western Ghats with sharp gradient of rainfall between the west coast heavy rain region and the rain shadow region to the east, pockets of heavy rainfall along the location of monsoon trough/low, over the east central parts of the country, over north–east India, along the foothills of Himalayas and over the north Bay of Bengal. When this product was used to assess the quality of other available standard climate products (CMAP and ECMWF reanalysis) at the grid resolution of 2.5°, it was found that the orographic heavy rainfall along Western Ghats of India was poorly identified by them. However, the GPCC analysis (gauge only) at the resolution of 1° grid closely discerns the new analysis. This suggests that there is a need for a higher resolution analysis with adequate rain gauge observations to retain important aspects of the summer monsoon over India. The case studies illustrated show that the daily analysis is able to capture large-scale as well as mesoscale features of monsoon precipitation systems. This study with data of two seasons (2001 and 2003) has shown sufficiently promising results for operational application, particularly for the validation of NWP models.

  9. The turbulence underside of the West African Monsoon

    Science.gov (United States)

    Lothon, M.; Lohou, F.; Saïd, F.; Campistron, B.; Canut, G.; Couvreux, F.; Durand, P.; Kalapureddy, M. C.; Lee, Y.; Madougou, S.; Serça, D.

    2009-09-01

    We present an experimental analysis of the sahelian Planetary Boundary Layer (PBL) processes in the context of the AMMA (African Monsoon Multidisciplinary Analysis) program and its extensive observational deployment in 2006. From May to October, two opposite flows are interacting in the first 5 thousands m over surface in Sahel: the moist southerly monsoon flow and the overlying northeasterly Saharan Air Layer (SAL) in which the African Easterly Jet (AEJ) is developing, generated by the contrast of surface moisture and temperature between Sahara and the Gulf of Guinea. Until the monsoon onset in mid-July, the low troposphere is slowly moistening through advection from the Guinea Gulf by the monsoon flow, especially during the night. During the day, the dry convection occurring within the PBL vertically redistributes part of the water vapour. After the onset, deep convection occurs much more frequently and the role played by the PBL completely changes. The relative position of the interface between monsoon and SAL and the PBL top inversion is crucial for the nature of the interaction and its impact on scalars, especially water vapour. We consider the role of the PBL processes in this context, and focus on four main aspects: (1) the diurnal cycle of the low troposphere, (2) the interaction between the PBL and the AEJ, (3) the entrainment at the PBL top (4) the impact of the PBL processes at surface. We base our analysis on long term profilers, radiosondes, and surface flux data, short term aircraft turbulence measurements made during the Special Observing Periods and Large Eddy Simulation. The network of wind profilers enables us to study the large scale circulation and highlight the consistence and extent of the nocturnal jet, and the importance of the diurnal cycle of the low troposphere for the West African Monsoon. During daytime, both the wind within the monsoon flow and the AEJ windspeed in the overlying SAL decrease, due to turbulent mixing within the PBL and

  10. Predicting monsoon rainfall and pressure indices from sea surface temperature

    Digital Repository Service at National Institute of Oceanography (India)

    Sadhuram, Y.

    The relationship between the sea surface temperature (SST) in the Indian Ocean and monsoon rainfall has been examined by using 21 years data set (1967-87) of MOHSST.6 (Met. Office Historical Sea Surface Temperature data set, obtained from U.K. Met...

  11. Atlantic effects on recent decadal trends in global monsoon

    Science.gov (United States)

    Kamae, Youichi; Li, Xichen; Xie, Shang-Ping; Ueda, Hiroaki

    2017-01-01

    Natural climate variability contributes to recent decadal climate trends. Specifically the trends during the satellite era since 1979 include Atlantic and Indian Ocean warming and Pacific cooling associated with phase shifts of the Atlantic Multidecadal Oscillation and the Pacific Decadal Oscillation, and enhanced global monsoon (GM) circulation and rainfall especially in the Northern Hemisphere. Here we evaluate effects of the oceanic changes on the global and regional monsoon trends by partial ocean temperature restoring experiments in a coupled atmosphere-ocean general circulation model. Via trans-basin atmosphere-ocean teleconnections, the Atlantic warming drives a global pattern of sea surface temperature change that resembles observations, giving rise to the enhanced GM. The tropical Atlantic warming and the resultant Indian Ocean warming favor subtropical deep-tropospheric warming in both hemispheres, resulting in the enhanced monsoon circulations and precipitation over North America, South America and North Africa. The extratropical North Atlantic warming makes an additional contribution to the monsoon enhancement via Eurasian continent warming and resultant land-sea thermal gradient over Asia. The results of this study suggest that the Atlantic multidecadal variability can explain a substantial part of global climate variability including the recent decadal trends of GM.

  12. Evidence of Upwelling along Peninsular Malaysia during Southwest Monsoon

    DEFF Research Database (Denmark)

    Daryabor, Farshid

    2015-01-01

    Upwelling off the east coast of Peninsular Malaysia (PM) was detected from recent cruise data collected during the southwest monsoon. Thermocline lifting was observed at 104˚E from a number of parallel transects. To confirm the presence of upwelling, satellite remote sensing data were used...

  13. Sensitivity of the Indian Monsoon to Human Activities

    Institute of Scientific and Technical Information of China (English)

    B. KNOPF; K. ZICKFELD; M. FLECHSIG; V. PETOUKHOV

    2008-01-01

    In this paper the authors perform an extensive sensitivity analysis of the Indian summer monsoon rainfall to changes in parameters and boundary conditions which are influenced by human activities. For this study, the authors use a box model of the Indian monsoon which reproduces key features of the observed monsoon dynamics such as the annual course of precipitation and the transitions between winter and summer regimes. Because of its transparency and computational efficiency, this model is highly suitable for exploring the effects of anthropogenic perturbations such as emissions of greenhouse gases and sulfur dioxide, and land cover changes, on the Indian monsoon. Results of a systematic sensitivity analysis indicate that changes in those parameters which are related to emissions of greenhouse gases lead to an increase in Indian summer rainfall. In contrast, all parameters related to higher atmospheric aerosol concentrations lead to a decrease in Indian rainfall. Similarly, changes in parameters which can be related to forest conversion or desertification, act to decrease the summer precipitation. The results indicate that the sign of precipitation changes over India will be dependent on the direction and relative magnitude of different human perturbations.

  14. Characteristics of monsoon waves off Uran, west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Nayak, B.U.; Chandramohan, P.; Mandal, S.

    's and the spectral methods for determining various wave parameters. Monsoon wave climate was stronger with the occurrence of the highest significant wave height of 2.45 m and the corresponding maximum wave height of 3.9 m in July. Significant wave height varied from...

  15. Spatial monsoon variability with respect to NAO and SO

    Indian Academy of Sciences (India)

    S B Kakade; S S Dugam

    2006-10-01

    In this paper, the simultaneous effect of North Atlantic Oscillation (NAO) and Southern Oscillation (SO) on monsoon rainfall over different homogeneous regions/subdivisions of India is studied. The simultaneous effect of both NAO and SO on Indian summer monsoon rainfall (ISMR) is more important than their individual impact because both the oscillations exist simultaneously throughout the year. To represent the simultaneous impact of NAO and SO, an index called effective strength index (ESI) has been defined on the basis of monthly NAO and SO indices. The variation in the tendency of ESI from January through April has been analyzed and reveals that when this tendency is decreasing, then the ESI value throughout the monsoon season (June-September) of the year remains negative and vice versa. This study further suggests that during the negative phase of ESI tendency, almost all subdivisions of India show above-normal rainfall and vice versa. The correlation analysis indicates that the ESI-tendency is showing an inverse and statistically significant relationship with rainfall over 14 subdivisions of India. Area wise, about 50% of the total area of India shows statistically significant association. Moreover, the ESI-tendency shows a significant relationship with rainfall over north west India, west central India, central north east India, peninsular India and India as a whole. Thus, ESI-tendency can be used as a precursor for the prediction of Indian summer monsoon rainfall on a smaller spatial scale.

  16. Hydrography of the Wadge bank - premonsoon and monsoon seasons

    Digital Repository Service at National Institute of Oceanography (India)

    RamaRaju, V.S.; Rao, T.V.N.; RameshBabu, V.; Anto, A.F.

    and central parts of the region during pre-monsoon. The low saline Bay of Bengal waters are present in the southeastern part of the Wadge Bank and high saline waters of Arabian Sea intrude from northwest indicating the withdrawal of the North Equatorial...

  17. Is an onset vortex important for monsoon onset over Kerala?

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar, M.R.; Sankar, S.; Reason, C.

    Inter-annual variability in the formation of the mini warm pool [sea-surface temperature (SST) more than 30 degrees C] over the south eastern Arabian Sea (SEAS) and its role in the formation of the monsoon onset vortex (MOV) has been examined using...

  18. Morphodynamics of tidal inlets in a tropical monsoon area

    NARCIS (Netherlands)

    Lam, N.T.; Stive, M.J.F.; Verhagen, H.J.; Wang, Z.B.

    2007-01-01

    Morphodynamics of a tidal inlet system on a micro-tidal coast in a tropical monsoon influenced region is modelled and discussed. Influences of river flow and wave climate on the inlet morphology are investigated with the aid of process-based state-of-the-art numerical models. Seasonal and episodic b

  19. Surface temperature pattern of the Indian Ocean before summer monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Gopinathan, C.K.; Rao, D.P.

    , suggests that the position of the warmer areas in the Bay of Bengal in May is an indicator of the subsequent summer rainfall over India. The statistical method adopted for the long range forcasting of the Indian summer monsoon gives very little...

  20. Early warnings and missed alarms for abrupt monsoon transitions

    Directory of Open Access Journals (Sweden)

    Z. A. Thomas

    2015-04-01

    Full Text Available Palaeo-records from China (Cheng et al., 2009; Wang et al., 2008, 2001 demonstrate the East Asian Summer Monsoon (EASM is dominated by abrupt and large magnitude monsoon shifts on millennial timescales, switching between periods of high and weak monsoon rains. It has been hypothesised that over these timescales, the EASM exhibits two stable states with bifurcation-type tipping points between them (Schewe et al., 2012. Here we test this hypothesis by looking for early warning signals of past bifurcations in speleothem records from Sanbao Cave and Hulu Cave, China (Wang et al., 2008, 2001, spanning the penultimate glacial cycle, and in multiple model simulations derived from the data. We find hysteresis behaviour in our model simulations with transitions directly forced by solar insolation. We detect critical slowing down prior to an abrupt monsoon shift during the penultimate deglaciation consistent with long-term orbital forcing. However, such signals are only detectable when the change in system stability is sufficiently slow to be detected by the sampling resolution of the dataset, raising the possibility that the alarm was missed and a similar forcing drove earlier EASM shifts.

  1. Moisture source for summer monsoon rainfall over India

    Digital Repository Service at National Institute of Oceanography (India)

    Sadhuram, Y.; Rao, D.P.

    Southwest monsoon plays a vital role in India's economy as the major income comes from agriculture. What could be the moisture source for this copious amount of rainfall over the Indian sub-continent?. This has been studied in detail and noticed...

  2. An Assessment of Monsoon Triggered Landslides in Western Nepal

    Science.gov (United States)

    Sudan Acharya, Madhu

    2010-05-01

    Due to heavy monsoon rain, rugged topography and very young mountains, frequent slope failures and soil erosion are very common in Nepal but in most of cases the natural slopes are disturbed by men to construct a road through it and the situation further aggravated by the Monsoon rain. Summer usually tests the disaster response capacity of Nepal, when the monsoons trigger water induced disasters. This year Nepal's Western regions were most severely affected by floods and landslides. Every year, sadly, it is the same story of mostly poor people living in remote villages succumbing to landslides and flooding and those who survive facing hardships brought on by the disaster. The tail end of the monsoon in October has triggered flood and landslides in Nepal which affected a total of 14 districts in the mid and far-west regions, of which Kailali, Bardiya, Banke, Dadeldhura, Accham and Kanchapur district are most affected. The affected areas are geographically scattered and remote, and are therefore difficult to access. In this year (2009), flood and landslides have claimed 62 lives, affecting more than 152,000 individuals from 27,000 families. More than 4,000 families are displaced and are taking shelter in schools, open space and forest areas with no protection from the external elements. In the above context the prevention and mitigation measures for landslides is a great challenge for Nepal. Nepal has been investing its huge amount of resources to stabilize landslides and roadside slope failures, still then it has become unmanageable during Monsoon time. Considering the above facts, an assessment of landslides which were occurred during the Monsoon (July-October 2009), along Khodpe - Jhota - Chainpur road in far western region of Nepal has been carried out based on the field observation of various landslides. The paper presents the causes and mechanisms of failures of different landslides which are mostly triggered by Monsoon rain. It also suggests some low cost

  3. What drives the global summer monsoon over the past millennium?

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jian [Chinese Academy of Sciences, State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Nanjing (China); Wang, Bin [University of Hawaii at Manoa, Department of Meteorology, Honolulu, HI (United States); University of Hawaii at Manoa, International Pacific Research Center, Honolulu, HI (United States); Yim, So-Young; Lee, June-Yi [University of Hawaii at Manoa, International Pacific Research Center, Honolulu, HI (United States); Jhun, Jong-Ghap [Seoul National University, School of Earth and Environmental Sciences/Research Institute of Oceanography, Seoul (Korea, Republic of); Ha, Kyung-Ja [Pusan National University, Division of Earth Environmental System, Busan (Korea, Republic of)

    2012-09-15

    The global summer monsoon precipitation (GSMP) provides a fundamental measure for changes in the annual cycle of the climate system and hydroclimate. We investigate mechanisms governing decadal-centennial variations of the GSMP over the past millennium with a coupled climate model's (ECHO-G) simulation forced by solar-volcanic (SV) radiative forcing and greenhouse gases (GHG) forcing. We show that the leading mode of GSMP is a forced response to external forcing on centennial time scale with a globally uniform change of precipitation across all monsoon regions, whereas the second mode represents internal variability on multi-decadal time scale with regional characteristics. The total amount of GSMP varies in phase with the global mean temperature, indicating that global warming is accompanied by amplification of the annual cycle of the climate system. The northern hemisphere summer monsoon precipitation (NHSMP) responds to GHG forcing more sensitively, while the southern hemisphere summer monsoon precipitation (SHSMP) responds to the SV radiative forcing more sensitively. The NHSMP is enhanced by increased NH land-ocean thermal contrast and NH-minus-SH thermal contrast. On the other hand, the SHSMP is strengthened by enhanced SH subtropical highs and the east-west mass contrast between Southeast Pacific and tropical Indian Ocean. The strength of the GSMP is determined by the factors controlling both the NHSMP and SHSMP. Intensification of GSMP is associated with (a) increased global land-ocean thermal contrast, (b) reinforced east-west mass contrast between Southeast Pacific and tropical Indian Ocean, and (c) enhanced circumglobal SH subtropical highs. The physical mechanisms revealed here will add understanding of future change of the global monsoon. (orig.)

  4. The South Asian Monsoon Circulation in Moist Isentropic coordinates

    Science.gov (United States)

    Thazhe Purayil, Sabin; Pauluis, Olivier

    2016-04-01

    The atmospheric circulation and thermodynamic structure during the South Asian Summer Monsoon season is analyzed in isentropic coordinates through the mass transport represented in terms of the potential temperature and equivalent potential temperature. This approach, originally developed to analyze the global meridional circulation, makes it possible to identify the thermodynamic properties of the inflow and outflow of different air mass. To understand the thermodynamic properties of air mass in south Asian monsoon region, we have used three diagnostics; a) the joint distribution of the mass transport as a function of dry and moist entropy, b) the vertical mass flux over the monsoon domain and c) the mass transport and isentropic thickness for different moist ventilation range of tropical atmosphere. The thermodynamic properties of the various air masses, such as the inflow of warm moist air in the boundary layer, upper tropospheric outflow, and midlatitude dry air intrusion are being systematically identified. The isentropic distribution of the vertical mass flux transport in terms of equivalent potential temperature is used to explain the characteristics of ascending and descending air parcels over the Indian subcontinent. Diagnosis based on the isentropic thickness reveals that the regional monsoon circulation and associated precipitation features can be systematically explained by this method. This technique is used to study the evolution of the monsoon flow in the seasonal scale. We used the data from AMIP-type simulations carried out with prescribed Sea Surface Temperature and sea ice for a 25 year period (1981-2005) from the GFDL High-resolution atmospheric model (HiRAM) with an average grid spacing of ~25km over the globe.

  5. The vorticity and angular momentum budgets of Asian summer monsoon

    Indian Academy of Sciences (India)

    P L S Rao; U C Mohanty; P V S Raju; M A Arain

    2004-09-01

    The study delineates the vorticity and angular momentum balances of Asian summer monsoon during the evolution and established phases. It also elucidates the differences between these balances in the National Centre for Environmental Prediction/National Centre for Atmospheric Research (NCEP/NCAR) reanalysis and the National Centre for Medium Range Weather Forecasts (NCM- RWF) analysis fields. The NCEP/NCAR reanalysis for a 40 year period (1958-97) and the NCM- RWF analysis for a three year (1994-96) period are made use of for the purpose. The time mean summer monsoon circulation is bifurcated into stable mean and transient eddy components and the mean component is elucidated. The generation of vorticity due to stretching of isobars balances most of the vorticity transported out of the monsoon domain during the evolution period. However, during the established period, the transportation by the relative and planetary vorticity components exceeds the generation due to stretching. The effective balancing mechanism is provided by vorticity generation due to sub-grid scale processes. The flux convergence of omega and relative momenta over the monsoon domain is effectively balanced by pressure torque during the evolution and established phases. Nevertheless, the balance is stronger during the established period due to the increase in the strength of circulation. Both the NCMRWF and NCEP fields indicate the mean features related to vorticity and angular momentum budgets realistically. Apart from the oceanic bias (strong circulation over oceans rather than continents), the summer monsoon circulation indicated by the NCEP is feeble compared to NCMRWF. The significant terms in the large-scale budgets of vorticity and angular momentum enunciate this aspect.

  6. Impacts of intraseasonal oscillation on the onset and interannual variation of the Indian summer monsoon

    Institute of Scientific and Technical Information of China (English)

    QI YanJun; ZHANG RenHe; LI Tim; WEN Min

    2009-01-01

    The role of the intraseasonal oscillation (ISO) on the seasonal and interannual variations of the Indian summer monsoon is investigated based on the analysis of observational data. It is shown that the ISO significantly contributes to the establishment of low-level westerlies during the monsoon onset and developing periods. The effect of the ISO on the annual cycle of the monsoon is through nonlinear eddy momentum transport. On the interannual timescale, the Indian summer monsoon rainfall exhibits a significant out-of-phase relationship with the ISO intensity over the Indian monsoon region. In strong ISO years it appears the weak monsoon when there is an abnormal high over the India subcontinent in the lower troposphere. In weak ISO years there exists an abnormal low and the strong monsoon ap-pears.

  7. Potential modulations of pre-monsoon aerosols during El Niño: impact on Indian summer monsoon

    Science.gov (United States)

    Fadnavis, S.; Roy, Chaitri; Sabin, T. P.; Ayantika, D. C.; Ashok, K.

    2016-11-01

    The potential role of aerosol loading on the Indian summer monsoon rainfall during the El Niño years are examined using satellite-derived observations and a state of the art fully interactive aerosol-chemistry-climate model. The Aerosol Index (AI) from TOMS (1978-2005) and Aerosol Optical Depth (AOD) from MISR spectroradiometer (2000-2010) indicate a higher-than-normal aerosol loading over the Indo-Gangetic plain (IGP) during the pre-monsoon season with a concurrent El Niño. Sensitivity experiments using ECHAM5-HAMMOZ climate model suggests that this enhanced loading of pre-monsoon absorbing aerosols over the Indo-Gangetic plain can reduce the drought during El Niño years by invoking the `Elevated-Heat-Pump' mechanism through an anomalous aerosol-induced warm core in the atmospheric column. This anomalous heating upshot the relative strengthening of the cross-equatorial moisture inflow associated with the monsoon and eventually reduces the severity of drought during El Niño years. The findings are subject to the usual limitations such as the uncertainties in observations, and limited number of El Niño years (during the study period).

  8. Rocky Mountain hydroclimate: Holocene variability and the role of insolation, ENSO, and the North American Monsoon

    Science.gov (United States)

    Anderson, Lesleigh

    2012-01-01

    Over the period of instrumental records, precipitation maximum in the headwaters of the Colorado Rocky Mountains has been dominated by winter snow, with a substantial degree of interannual variability linked to Pacific ocean–atmosphere dynamics. High-elevation snowpack is an important water storage that is carefully observed in order to meet increasing water demands in the greater semi-arid region. The purpose here is to consider Rocky Mountain water trends during the Holocene when known changes in earth's energy balance were caused by precession-driven insolation variability. Changes in solar insolation are thought to have influenced the variability and intensity of the El Niño Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and North American Monsoon and the seasonal precipitation balance between rain and snow at upper elevations. Holocene records are presented from two high elevation lakes located in northwest Colorado that document decade-to-century scale precipitation seasonality for the past ~ 7000 years. Comparisons with sub-tropical records of ENSO indicate that the snowfall-dominated precipitation maxima developed ~ 3000 and 4000 years ago, coincident with evidence for enhanced ENSO/PDO dynamics. During the early-to-mid Holocene the records suggest a more monsoon affected precipitation regime with reduced snowpack, more rainfall, and net moisture deficits that were more severe than recent droughts. The Holocene perspective of precipitation indicates a far broader range of variability than that of the past century and highlights the non-linear character of hydroclimate in the U.S. west.

  9. Monsoonal versus Anthropogenic Controls on Erosion Patterns and Sediment Flux in the Song Gianh, Vietnam

    Science.gov (United States)

    Clift, Peter; Jonell, Tara; Carter, Andrew; Van Hoang, Long; Böning, Philipp

    2016-04-01

    The Song Gianh is a small drainage on the northern central coast of Vietnam that delivers sediment into the Gulf of Tonkin. The basin provides the opportunity to evaluate what surface processes control continental erosion rates and patterns because there is a strong monsoonal precipitation gradient from the SW to NE. We apply several complimentary provenance methods to modern siliciclastic sediments of the Song Gianh to pinpoint regions of focused sediment generation and evaluate how sediment is mixed downstream and delivered to the ocean. We find that detrital zircon populations of Song Gianh main channel change radically downstream of the confluence with the northern Rao Tro tributary, which is dominated by 100-300 Ma grains eroded from granite bedrock. This tributary provides almost as much zircon to the main channel as all the headwater tributaries combined, despite being a much smaller, drier, and flatter sub-basin. In contrast, bulk sediment Nd and Sr isotopes indicate that most sediment is derived from the wetter headwater tributaries. Contribution from the southern tributaries to the net siliciclastic river flux is negligible. Precipitation and topography do not appear to modulate zircon production in the modern river although regions controlling bulk Nd and Sr compositions are wetter and have higher local relief. This apparent contrast in regions of sediment production suggests disequilibrium and differential travel times for zircon and mineral phases rich in Nd and Sr. Optically Stimulated Luminescence (OSL) dating of alluvial terraces on the main channel show that the valleys aggraded rapidly from ~7-9 ka during a period of strong summer monsoon, suggesting that heavy rainfall generated large sediment volumes. Younger terraces dated to 500-1000 yrs BP are interpreted to reflect erosion and aggradation driven by extensive human agriculture. We speculate that agriculture, together with bedrock compositions, are the most likely control on producing the

  10. Intraseasonal variability of the Indian summer monsoon: wet and dry events in COSMO-CLM

    Science.gov (United States)

    Befort, Daniel J.; Leckebusch, G. C.; Cubasch, U.

    2016-10-01

    This study aims to validate the widely used regional climate model COSMO-CLM driven by ERA-Interim reanalysis data with a spatial resolution of 55 km with respect to observed features of the intraseasonal variability of the Indian summer monsoon (ISM) during the period 1979 until 2011. One of these features is the northward propagation of the ISM intraseasonal oscillations. We find, that the temporal evolution between model and observation is in good agreement, while less agreement with respect to the strength is found. Furthermore, the model's capability to simulate observed dry and wet events on a weekly time-scale is investigated using the standardized precipitation index. In general, the model is capable to simulate these events with a similar magnitude at the same time. Observational based analyses show, that the coupling between atmospheric circulation anomalies and rainfall anomalies over India on the intraseasonal time scale is well represented by the model. The most important circulation anomalies for dry events are a lower tropospheric anti-cyclonic vortex over India and partly an upper tropospheric cyclonic vortex over the Pakistan region and vice versa for wet events. The model shows a slightly higher ability to simulate dry compared to wet events. Overall, this study shows that the current configuration of COSMO-CLM is able to simulate the key features of the intraseasonal variability of the Indian summer monsoon. Being aware of its limitation, COSMO-CLM is suitable to investigate possible changes of the intraseasonal variability of ISM under changed climate conditions in the past or in the future.

  11. Relationship between summer monsoon rainfall and cyclogenesis over Bay of Bengal during post-monsoon (October–December) season

    Indian Academy of Sciences (India)

    Y Sadhuram; K Maneesha

    2016-10-01

    In this study, an attempt has been made to examine the relationship between summer monsoon rainfall (June–September) and the total number of depressions, cyclones and severe cyclones (TNDC) over Bay of Bengal during the post-monsoon (October–December) season. The seasonal rainfall of the subdivisions (located in south India) (referred as rainfall index – RI), is positively and significantly correlated(r = 0.59; significant at >99% level) with the TNDC during the period, 1984–2013. By using the first differences (current season minus previous season), the correlations are enhanced and a remarkably high correlation of 0.87 is observed between TNDC and RI for the recent period, 1993–2013. The average seasonalgenesis potential parameter (GPP) showed a very high correlation of 0.84 with the TNDC. A very high correlation of 0.83 is observed between GPP and RI for the period, 1993–2013. The relative vorticity and mid-tropospheric relative humidity are found to be the dominant terms in GPP. The GPP was 3.5 times higher in above (below) normal RI in which TNDC was 4 (2). It is inferred that RI is playing a keyrole in TNDC by modulating the environmental conditions (low level vorticity and relative humidity) over Bay of Bengal during post-monsoon season which could be seen from the very high correlation of 0.87 (which explains 76% variability in TNDC). For the first time, we show that RI is a precursor for the TNDC over Bay of Bengal during post-monsoon season. Strong westerlies after the SW monsoon seasontransport moisture over the subdivisions towards Bay of Bengal due to cyclonic circulation. This circulation favours upward motion and hence transport moisture vertically to mid-troposphere which causes convective instability and this in turn favour more number of TNDC, under above-normal RI year.

  12. Relationship between summer monsoon rainfall and cyclogenesis over Bay of Bengal during post-monsoon (October-December) season

    Science.gov (United States)

    Sadhuram, Y.; Maneesha, K.

    2016-10-01

    In this study, an attempt has been made to examine the relationship between summer monsoon rainfall (June-September) and the total number of depressions, cyclones and severe cyclones (TNDC) over Bay of Bengal during the post-monsoon (October-December) season. The seasonal rainfall of the subdivisions (located in south India) (referred as rainfall index - RI), is positively and significantly correlated ( r=0.59; significant at >99% level) with the TNDC during the period, 1984-2013. By using the first differences (current season minus previous season), the correlations are enhanced and a remarkably high correlation of 0.87 is observed between TNDC and RI for the recent period, 1993-2013. The average seasonal genesis potential parameter (GPP) showed a very high correlation of 0.84 with the TNDC. A very high correlation of 0.83 is observed between GPP and RI for the period, 1993-2013. The relative vorticity and mid-tropospheric relative humidity are found to be the dominant terms in GPP. The GPP was 3.5 times higher in above (below) normal RI in which TNDC was 4 (2). It is inferred that RI is playing a key role in TNDC by modulating the environmental conditions (low level vorticity and relative humidity) over Bay of Bengal during post-monsoon season which could be seen from the very high correlation of 0.87 (which explains 76% variability in TNDC). For the first time, we show that RI is a precursor for the TNDC over Bay of Bengal during post-monsoon season. Strong westerlies after the SW monsoon season transport moisture over the subdivisions towards Bay of Bengal due to cyclonic circulation. This circulation favours upward motion and hence transport moisture vertically to mid-troposphere which causes convective instability and this in turn favour more number of TNDC, under above-normal RI year.

  13. Relationship between summer monsoon rainfall and cyclogenesis over Bay of Bengal during post-monsoon (October-December) season

    Science.gov (United States)

    Sadhuram, Y.; Maneesha, K.

    2016-09-01

    In this study, an attempt has been made to examine the relationship between summer monsoon rainfall (June-September) and the total number of depressions, cyclones and severe cyclones (TNDC) over Bay of Bengal during the post-monsoon (October-December) season. The seasonal rainfall of the subdivisions (located in south India) (referred as rainfall index - RI), is positively and significantly correlated (r=0.59; significant at >99% level) with the TNDC during the period, 1984-2013. By using the first differences (current season minus previous season), the correlations are enhanced and a remarkably high correlation of 0.87 is observed between TNDC and RI for the recent period, 1993-2013. The average seasonal genesis potential parameter (GPP) showed a very high correlation of 0.84 with the TNDC. A very high correlation of 0.83 is observed between GPP and RI for the period, 1993-2013. The relative vorticity and mid-tropospheric relative humidity are found to be the dominant terms in GPP. The GPP was 3.5 times higher in above (below) normal RI in which TNDC was 4 (2). It is inferred that RI is playing a key role in TNDC by modulating the environmental conditions (low level vorticity and relative humidity) over Bay of Bengal during post-monsoon season which could be seen from the very high correlation of 0.87 (which explains 76% variability in TNDC). For the first time, we show that RI is a precursor for the TNDC over Bay of Bengal during post-monsoon season. Strong westerlies after the SW monsoon season transport moisture over the subdivisions towards Bay of Bengal due to cyclonic circulation. This circulation favours upward motion and hence transport moisture vertically to mid-troposphere which causes convective instability and this in turn favour more number of TNDC, under above-normal RI year.

  14. Bacterial domination over Archaea in ammonia oxidation in a monsoon-driven tropical estuary

    Digital Repository Service at National Institute of Oceanography (India)

    Vipindas, P.V.; Anas, A.; Jasmin, C.; Lallu, K.R.; Fausia, K.H.; Balachandran, K.K.; Muraleedharan, K.R.; Nair, S.

    % polyacrylamide denaturing gradient gel prepared with 35 – 50 % (for AOB) and 30 – 55 % (for AOA) formamide for 17.5 h at 75 V. The bands separated were stained with SYBR green and observed in a gel documentation system (BioRAD, USA). The bands were picked.... This work was done using MMRF facility and is duly acknowledged. This is NIO contribution No: xxxx Reference 1. Mulder A, Van de Graaf AA, Robertson LA, Kuenen J (1995) Anaerobic ammonium oxidation discovered in a denitrifying fluidized bed reactor...

  15. Active and break spells of the Indian summer monsoon

    Indian Academy of Sciences (India)

    M Rajeevan; Sulochana Gadgil; Jyoti Bhate

    2010-06-01

    In this paper, we suggest criteria for the identification of active and break events of the Indian summer monsoon on the basis of recently derived high resolution daily gridded rainfall dataset over India (1951–2007). Active and break events are defined as periods during the peak monsoon months of July and August, in which the normalized anomaly of the rainfall over a critical area, called the monsoon core zone exceeds 1 or is less than −1.0 respectively, provided the criterion is satisfied for at least three consecutive days. We elucidate the major features of these events. We consider very briefly the relationship of the intraseasonal fluctuations between these events and the interannual variation of the summer monsoon rainfall. We find that breaks tend to have a longer life-span than active spells. While, almost 80% of the active spells lasted 3–4 days, only 40% of the break spells were of such short duration. A small fraction (9%) of active spells and 32% of break spells lasted for a week or longer. While active events occurred almost every year, not a single break occurred in 26% of the years considered. On an average, there are 7 days of active and break events from July through August. There are no significant trends in either the days of active or break events. We have shown that there is a major difference between weak spells and long intense breaks. While weak spells are characterized by weak moist convective regimes, long intense break events have a heat trough type circulation which is similar to the circulation over the Indian subcontinent before the onset of the monsoon. The space-time evolution of the rainfall composite patterns suggests that the revival from breaks occurs primarily from northward propagations of the convective cloud zone. There are important differences between the spatial patterns of the active/break spells and those characteristic of interannual variation, particularly those associated with the link to ENSO. Hence, the

  16. A diagnostic study of monsoon energetics for two contrasting years

    Directory of Open Access Journals (Sweden)

    S. S. V. S. Ramakrishna

    2010-12-01

    Full Text Available In the present study we made an attempt to explain the behavior of the southwest monsoon for two contrasting years, from the view point of energetics. As a test case we selected 2002 and 2003, which were weak and strong monsoon years, respectively, based on rainfall. The energy terms Kψ, Kχ and APE and the conversion terms f∇ψ. ∇χ, −ω'T' are calculated at 850 hPa level and also vertically integrated from 1000 hPa to 100 hPa. The results indicate that, the year of high energy (both KΨ, Kχ i.e. 2002, does not give a good amount of rainfall compared to the good year i.e. 2003. The break period during the year 2002 has been clearly explained using the block diagrams. Periods of highest rainfall coincide with the positive conversions of f∇ψ. ∇χ and −ω'T'. Vertically integrated moisture fluxes during the break period of 2002, 2003 are also analyzed. The main reservoirs (sources and sinks for the monsoon energy are also identified using block diagrams. Negative correlation between daily rainfall and energy terms in the year 2002 indicates its unusual behavior both in terms of energetics as well as precipitation. Positive correlations in the year 2003 represent strong monsoonal behavior. We calculated the climatology of the total kinetic energy at 850 hPa, vertically integrated (1000–100 hPa for 30 years (1980–2009 and rainfall for 103 years (1901–2003 which clearly indicates that the monsoon is indeed a season of high energy for the South Asian region.

    Also the east- west direct thermal circulations are strongly related to the good and bad monsoon years.

  17. Spatial variations of sea level along the coast of Thailand: Impacts of extreme land subsidence, earthquakes and the seasonal monsoon

    Science.gov (United States)

    Saramul, Suriyan; Ezer, Tal

    2014-11-01

    The study addresses two important issues associated with sea level along the coasts of Thailand: first, the fast sea level rise and its spatial variation, and second, the monsoonal-driven seasonal variations in sea level. Tide gauge data that are more extensive than in past studies were obtained from several different local and global sources, and relative sea level rise (RSLR) rates were obtained from two different methods, linear regressions and non-linear Empirical Mode Decomposition/Hilbert-Huang Transform (EMD/HHT) analysis. The results show extremely large spatial variations in RSLR, with rates varying from ~ 1 mm y-1 to ~ 20 mm y-1; the maximum RSLR is found in the upper Gulf of Thailand (GOT) near Bangkok, where local land subsidence due to groundwater extraction dominates the trend. Furthermore, there are indications that RSLR rates increased significantly in all locations after the 2004 Sumatra-Andaman Earthquake and the Indian Ocean tsunami that followed, so that recent RSLR rates seem to have less spatial differences than in the past, but with high rates of ~ 20-30 mm y-1 almost everywhere. The seasonal sea level cycle was found to be very different between stations in the GOT, which have minimum sea level in June-July, and stations in the Andaman Sea, which have minimum sea level in February. The seasonal sea-level variations in the GOT are driven mostly by large-scale wind-driven set-up/set-down processes associated with the seasonal monsoon and have amplitudes about ten times larger than either typical steric changes at those latitudes or astronomical annual tides.

  18. Shifting covariability of North American summer monsoon precipitation with antecedent winter precipitation

    Science.gov (United States)

    McCabe, G.J.; Clark, M.P.

    2006-01-01

    Previous research has suggested that a general inverse relation exists between winter precipitation in the southwestern United states (US) and summer monsoon precipitation. In addition, it has been suggested that this inverse relation between winter precipitation and the magnitude of the southwestern US monsoon breaks down under certain climatic conditions that override the regional winter/monsoon precipitation relations. Results from this new study indicate that the winter/monsoon precipitation relations do not break down, but rather shift location through time. The strength of winter/monsoon precipitation relations, as indexed by 20-year moving correlations between winter precipitation and monsoon precipitation, decreased in Arizona after about 1970, but increased in New Mexico. The changes in these correlations appear to be related to an eastward shift in the location of monsoon precipitation in the southwestern US. This eastward shift in monsoon precipitation and the changes in correlations with winter precipitation also appear to be related to an eastward shift in July/August atmospheric circulation over the southwestern US that resulted in increased monsoon precipitation in New Mexico. Results also indicate that decreases in sea-surface temperatures (SSTs) in the central North Pacific Ocean also may be associated with th changes in correlations between winter and monsoon precipitation. Copyright ?? 2006 Royal Meteorological Society.

  19. Predictor-Year Subspace Clustering Based Ensemble Prediction of Indian Summer Monsoon

    Directory of Open Access Journals (Sweden)

    Moumita Saha

    2016-01-01

    Full Text Available Forecasting the Indian summer monsoon is a challenging task due to its complex and nonlinear behavior. A large number of global climatic variables with varying interaction patterns over years influence monsoon. Various statistical and neural prediction models have been proposed for forecasting monsoon, but many of them fail to capture variability over years. The skill of predictor variables of monsoon also evolves over time. In this article, we propose a joint-clustering of monsoon years and predictors for understanding and predicting the monsoon. This is achieved by subspace clustering algorithm. It groups the years based on prevailing global climatic condition using statistical clustering technique and subsequently for each such group it identifies significant climatic predictor variables which assist in better prediction. Prediction model is designed to frame individual cluster using random forest of regression tree. Prediction of aggregate and regional monsoon is attempted. Mean absolute error of 5.2% is obtained for forecasting aggregate Indian summer monsoon. Errors in predicting the regional monsoons are also comparable in comparison to the high variation of regional precipitation. Proposed joint-clustering based ensemble model is observed to be superior to existing monsoon prediction models and it also surpasses general nonclustering based prediction models.

  20. Forcing mechanism of the Pleistocene east Asian monsoon variations in a phase perspective

    Institute of Scientific and Technical Information of China (English)

    TIAN; Jun; WANG; Pinxian; CHENG; Xinrong; WANG; Rujian; SU

    2005-01-01

    The deep sea records from the ODP Sites 1143 and 1144 in the northern and southern South China Sea (SCS), including foraminiferal δ18O and δ13C, Opal% and pollen percentage, reveal that the variations of the east Asian monsoon have been closely correlated with the variations of the Earth's orbital parameters (eccentricity, obliquity and precession) and the global ice volume on orbital scale. All the monsoonal proxies show strong 100 ka, 41 ka and 23 ka cycles. Although G. ruber δ13C of Site 1143 is coherent with the ETP (ETP= normalized (eccentricity + obliquity-precession) at eccentricity, obliquity and precession bands, most of the coherent relationship focuses on the precession band, and the other monsoonal proxies are coherent with the ETP only at the precession band, which indicate that precession dominates the Pleistocene tropical climate changes. The phase relationship of the monsoonal proxies with the foraminiferal δ18O implies that the global ice volume changes have played a significant role in modulating the east Asian monsoon climate, at least dominating the winter monsoon. This forcing mechanism of the east Asian monsoon is apparently different from that of the Indian ocean monsoon. The variations of the east Asian monsoon at the precession band, at least that of the winter monsoon, have been controlled not only by the sensible heating but also by the latent heating of the surface water in the South China Sea.

  1. Role of Atmospheric Circulation and Westerly Jet Changes in the mid-Holocene East Asian Summer Monsoon

    Science.gov (United States)

    Kong, W.; Chiang, J. C. H.

    2014-12-01

    The East Asian Summer Monsoon (EASM) varies on inter-decadal to interglacial-glacial timescales. The EASM is stronger in the mid-Holocene than today, and these changes can be readily explained by orbitally-driven insolation increase during the boreal summer. However, a detailed understanding of the altered seasonal evolution of the EASM during this time is still lacking. In particular, previous work has suggested a close link between seasonal migration of the EASM and that of the mid-latitude westerlies impinging on the Tibetan Plateau. In this study, we explore, this problem in PMIP3 climate model simulations of the mid-Holocene, focusing on the role of atmospheric circulation and in particular how the westerly jet modulates the East Asia summer climate on paleoclimate timescales. Analysis of the model simulations suggests that, compared to the preindustrial simulations, the transition from Mei-Yu to deep summer rainfall occurs earlier in the mid-Holocene. This is accompanied by an earlier weakening and northward shift of westerly jet away from the Tibetan Plateau. The variation in the strength and the 3-D structure of the westerly jet in the mid-Holocene is summarized. We find that changes to the monsoonal rainfall, westerly jet and meridional circulation covary on paleoclimate timescales. Meridional wind changes in particular are tied to an altered stationary wave pattern, resembling today's the so-called 'Silk Road' teleconnection pattern, riding along the westerly jet. Diagnostic analysis also reveals changes in moist static energy and eddy energy fluxes associated with the earlier seasonal transition of the EASM. Our analyses suggest that the westerly jet is critical to the altered dynamics of the East Asian summer monsoon during the mid-Holocene.

  2. Monsoon oscillations regulate fertility of the Red Sea

    KAUST Repository

    Raitsos, Dionysios E.

    2015-02-16

    Tropical ocean ecosystems are predicted to become warmer, more saline, and less fertile in a future Earth. The Red Sea, one of the warmest and most saline environments in the world, may afford insights into the function of the tropical ocean ecosystem in a changing planet. We show that the concentration of chlorophyll and the duration of the phytoplankton growing season in the Red Sea are controlled by the strength of the winter Arabian monsoon (through horizontal advection of fertile waters from the Indian Ocean). Furthermore, and contrary to expectation, in the last decade (1998-2010) the winter Red Sea phytoplankton biomass has increased by 75% during prolonged positive phases of the Multivariate El Niño-Southern Oscillation Index. A new mechanism is reported, revealing the synergy of monsoon and climate in regulating Red Sea greenness. © 2015 The Authors.

  3. Response of monsoon variability in Himalayas to global warming

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Reconstructed annual net accumulation from the Dasuopu ice core recovered in Himalayas, with a good correlation to Indian monsoon, reflects a major precipitation trend in central Himalayas. The Dasuopu accumulation (DSP An) also shows a strong correlation to the Northern Hemispheric temperature. Generally, as the Northern Hemispheric temperature increases by 0.1 K, the accumulation decreases by about 90 mm and vise versa. Under the condition of global warming, especially since 1920, the Northern Hemispheric mean temperature has increased by about 0.5 K, whereas accumulation in Dasuopu ice core has decreased by about 450 mm. According to the relationship between accumulation and temperature, a scenario prediction of monsoon rainfall in central Himalayas is made.

  4. Mesoscale characteristics of monsoonal convection and associated stratiform precipitation

    Science.gov (United States)

    Keenan, Thomas D.; Rutledge, Steven A.

    1993-01-01

    Observations undertaken on 12 January 1990 at Darwin (Australia) are used to document the structure of a monsoonal rainband in a low convective available potential energy low-shear tropical environment. Dual-Doppler radar analyses are employed to investigate the structure and kinematics of the convective and stratiform regions. A system with the characteristics of a relatively short-lived squall line in which warm rain processes play a significant role in the production of precipitation is evident. Planetary boundary layer cold-pool production is important in the organization and motion of the system. A trailing stratiform region is evident with a mean updraft-downdraft circulation, but is composed of in situ decaying convective cells. A storm-relative mesoscale cyclonic circulation is also observed within the stratiform cloud. This vortex was maintained by thermodynamically induced midlevel convergence, convectively generated storm-scale circulations, and their interaction with the background monsoon flow.

  5. The onset and advance of the Asian summer monsoon

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Based on the daily outgoing longwave radiation (OLR) data from National Oceanic and Atmospheric Administration (NOAA) satellites, the Climate Prediction Center's merged analysis of precipitation (CMAP) data and the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis dataset, the mean intraseasonal variability of the Asian summer monsoon (ASM) is investigated by using power spectrum analysis, band-pass filter, and diagnostic analyses. The processes of the onset and advance of monsoon over the southern part of Indochina Peninsula, the east coast of Bay of Bengal, the South China Sea and the Indian subcontinent are explored. It is found that there is an abrupt change in OLR, precipitation and zonal wind during the onset and advance of the ASM. It is also indicated that the southern part of Indochina Peninsula and the adjacent Andaman Sea is the region where the earliest onset of the ASM occurs in the 2nd pentad of May.

  6. Predicting onset and withdrawal of Indian Summer Monsoon in 2016: results of Tipping elements approach

    Science.gov (United States)

    Surovyatkina, Elena; Stolbova, Veronika; Kurths, Jurgen

    2017-04-01

    The monsoon is the season of rain caused by a global seasonal reverse in winds direction and a change in pressure distribution. The Southwest winds bring summer monsoon to India. The economy of India is able to maintain its GDP in the wake of a good monsoon. However, if monsoon gets delayed by even two weeks, it can spell disaster because the high population depending on agriculture - 70% of its people directly related to farming. Agriculture, in turn, is dependent on the monsoon. Although the rainy season happens annually between June and September, the time of monsoon season's onset and withdrawal varies within a month from year to year. The important feature of the monsoon is that it starts and ends suddenly. Hence, despite enormous progress having been made in predicting monsoon since 1886, it remains a significant scientific challenge. To make predictions of monsoon timing in 2016, we applied our recently developed method [1]. Our approach is based on a teleconnection between the Eastern Ghats (EG) and North Pakistan (NP) - Tipping Elements of Indian Summer Monsoon. Both our predictions - for monsoon onset and withdrawal - were made for the Eastern Ghats region (EG-20N,80E) in the central part of India, while the Indian Meteorological Department forecasts monsoon over Kerala - a state at the southern tip of the Indian subcontinent. Our prediction for monsoon onset was published on May 6-th, 2016 [2]. We predicted the monsoon arrival to the EG on the 13th of June with a deviation of +/-4 days. In fact, monsoon onset was on June 17-th, that was confirmed by information from meteorological stations located around the EG-region. Hence, our prediction of monsoon onset (made 40 days in advance) was correct. We delivered the prediction of monsoon withdrawal on July 27, 2016 [3], announcing the monsoon withdrawal from the EG on October 5-th with a deviation of +/-5 days. The actual monsoon withdrawal started on October 10-th when the relative humidity in the region

  7. Eastward propagating MJO during boreal summer and Indian monsoon droughts

    Energy Technology Data Exchange (ETDEWEB)

    Joseph, Susmitha; Sahai, A.K.; Goswami, B.N. [Indian Institute of Tropical Meteorology, Climate and Global Modeling Division, Pune (India)

    2009-06-15

    Improved understanding of underlying mechanism responsible for Indian summer monsoon (ISM) droughts is important due to their profound socio-economic impact over the region. While some droughts are associated with 'external forcing' such as the El-Nino and Southern Oscillation (ENSO), many ISM droughts are not related to any known 'external forcing'. Here, we unravel a fundamental dynamic process responsible for droughts arising not only from external forcing but also those associated with internal dynamics. We show that most ISM droughts are associated with at least one very long break (VLB; breaks with duration of more than 10 days) and that the processes responsible for VLBs may also be the mechanism responsible for ISM droughts. Our analysis also reveals that all extended monsoon breaks (whether co-occurred with El-Nino or not) are associated with an eastward propagating Madden-Julian Oscillation (MJO) in the equatorial Indian Ocean and western Pacific extending to the dateline and westward propagating Rossby waves between 10 and 25 N. The divergent Rossby wave associated with the dry phase of equatorial convection propagates westward towards Indian land, couple with the northward propagating dry phase and leads to the sustenance of breaks. Thus, the propensity of eastward propagating MJO during boreal summer is largely the cause of monsoon droughts. While short breaks are not accompanied by westerly wind events (WWE) over equatorial western Pacific favorable for initiating air-sea interaction, all VLBs are accompanied by sustained WWE. The WWEs associated with all VLB during 1975-2005 initiate air-sea interaction on intraseasonal time scale, extend the warm pool eastward allowing the convectively coupled MJO to propagate further eastward and thereby sustaining the divergent circulation over India and the monsoon break. The ocean-atmosphere coupling on interannual time scale (such as El-Nino) can also produce VLB, but not necessary. (orig.)

  8. Stable isotopic signature of Australian monsoon controlled by regional convection

    Science.gov (United States)

    Zwart, C.; Munksgaard, N. C.; Kurita, N.; Bird, M. I.

    2016-11-01

    The aim of this study was to identify the main meteorological drivers of rainfall isotopic variation in north Australia in order to improve the interpretation of isotopic proxy records in this region. An intense monitoring program was conducted during two monsoonal events that showed significant and systematic isotopic change over time. The results showed a close link between isotopic variation in precipitation and variability in monsoon conditions, associated with the presence of large convective envelopes propagating through the study site. The largest negative amplitudes in the isotopic signal were observed when eastward and westward moving precipitation systems within the convective envelope merged over the measurement site. This suggests that the amplitude of the isotopic signal is related to the size and activity of the convective envelope. The strong correlation between rainfall isotopic variation, regional outgoing longwave radiation and regional rainfall amount supports this conclusion. This is further strengthened by the strong relationship between isotopic variation and the integrated rainfall history of air masses prior to arriving at the measurement locations. A local amount effect was not significant and these findings support the interpretation of δ18O as proxy for regional climatic conditions rather than local rainfall amount. Meteorological parameters that characterize intra-seasonal variability of monsoon conditions were also found to be strongly linked to inter-seasonal variability of the monthly based δ18O values in the Global Network of Isotopes in Precipitation (GNIP) database. This leads to the conclusion that information about the Australian monsoon variability can likely be inferred from the isotopic proxy record in North Australia on short (intra seasonal) and long (inter seasonal or longer) timescales.

  9. Eastward propagating MJO during boreal summer and Indian monsoon droughts

    Science.gov (United States)

    Joseph, Susmitha; Sahai, A. K.; Goswami, B. N.

    2009-06-01

    Improved understanding of underlying mechanism responsible for Indian summer monsoon (ISM) droughts is important due to their profound socio-economic impact over the region. While some droughts are associated with ‘external forcing’ such as the El-Niño and Southern Oscillation (ENSO), many ISM droughts are not related to any known ‘external forcing’. Here, we unravel a fundamental dynamic process responsible for droughts arising not only from external forcing but also those associated with internal dynamics. We show that most ISM droughts are associated with at least one very long break (VLB; breaks with duration of more than 10 days) and that the processes responsible for VLBs may also be the mechanism responsible for ISM droughts. Our analysis also reveals that all extended monsoon breaks (whether co-occurred with El-Niño or not) are associated with an eastward propagating Madden-Julian Oscillation (MJO) in the equatorial Indian Ocean and western Pacific extending to the dateline and westward propagating Rossby waves between 10° and 25°N. The divergent Rossby wave associated with the dry phase of equatorial convection propagates westward towards Indian land, couple with the northward propagating dry phase and leads to the sustenance of breaks. Thus, the propensity of eastward propagating MJO during boreal summer is largely the cause of monsoon droughts. While short breaks are not accompanied by westerly wind events (WWE) over equatorial western Pacific favorable for initiating air-sea interaction, all VLBs are accompanied by sustained WWE. The WWEs associated with all VLB during 1975-2005 initiate air-sea interaction on intraseasonal time scale, extend the warm pool eastward allowing the convectively coupled MJO to propagate further eastward and thereby sustaining the divergent circulation over India and the monsoon break. The ocean-atmosphere coupling on interannual time scale (such as El-Niño) can also produce VLB, but not necessary.

  10. The East Asian subtropical summer monsoon: Recent progress

    Science.gov (United States)

    He, Jinhai; Liu, Boqi

    2016-04-01

    The East Asian subtropical summer monsoon (EASSM) is one component of the East Asian summer monsoon system, and its evolution determines the weather and climate over East China. In the present paper, we firstly demonstrate the formation and advancement of the EASSM rainbelt and its associated circulation and precipitation patterns through reviewing recent studies and our own analysis based on JRA-55 (Japanese 55-yr Reanalysis) data and CMAP (CPC Merged Analysis of Precipitation), GPCP (Global Precipitation Climatology Project), and TRMM (Tropical Rainfall Measuring Mission) precipitation data. The results show that the rainy season of the EASSM starts over the region to the south of the Yangtze River in early April, with the establishment of strong southerly wind in situ. The EASSM rainfall, which is composed of dominant convective and minor stratiform precipitation, is always accompanied by a frontal system and separated from the tropical summer monsoon system. It moves northward following the onset of the South China Sea summer monsoon. Moreover, the role of the land-sea thermal contrast in the formation and maintenance of the EASSM is illustrated, including in particular the effect of the seasonal transition of the zonal land-sea thermal contrast and the influences from the Tibetan Plateau and midlatitudes. In addition, we reveal a possible reason for the subtropical climate difference between East Asia and East America. Finally, the multi-scale variability of the EASSM and its influential factors are summarized to uncover possible reasons for the intraseasonal, interannual, and interdecadal variability of the EASSM and their importance in climate prediction.

  11. Monsoon and primary acute angle closure in malaysia.

    Science.gov (United States)

    Ch'ng, T W; Mosavi, S A A; Noor Azimah, A A; Azlan, N Z; Azhany, Y; Liza-Sharmini, A T

    2013-10-01

    Acute angle closure (AAC) without prompt treatment may lead to optic neuropathy. Environmental factor such as climate change may precipitate pupillary block, the possible mechanism of AAC. To determine the association of northeast monsoon and incidence of AAC in Malaysia. A retrospective study was conducted on AAC patients admitted to two main tertiary hospitals in Kelantan, Malaysia between January 2001 and December 2011. The cumulative number of rainy day, amount of rain, mean cloud cover and 24 hours mean humidity at the estimated day of attack were obtained from the Department of Meteorology, Malaysia. A total 73 cases of AAC were admitted with mean duration of 4.1SD 2.0 days. More than half have previous history of possibility of AAC. There was higher incidence of AAC during the northeast monsoon (October to March). There was also significant correlation of number of rainy day (r=0.718, p<0.001), amount of rain (r=0.587, p<0.001), cloud cover (r=0.637, p<0.001), mean daily global radiation (r=- 0.596, P<0.001), 24 hours mean temperature (r=-0.298, p=0.015) and 24 hours mean humidity (r=0.508, p<0.001) with cumulative number of admission for AAC for 12 calendar months. Higher incidence of AAC during northeast monsoon suggested the effect of climate as the potential risk factor. Prompt treatment to arrest pupillary block and reduction of the intraocular pressure is important to prevent potential glaucomatous damage. Public awareness of AAC and accessibility to treatment should be part of preparation to face the effect of northeast monsoon.

  12. Shift in Indian summer monsoon onset during 1976/1977

    Science.gov (United States)

    Sahana, A. S.; Ghosh, Subimal; Ganguly, Auroop; Murtugudde, Raghu

    2015-05-01

    The Indian summer monsoon rainfall (ISMR) contributes nearly 80% of the annual rainfall over India and has a significant influence on the country’s gross domestic product through the agricultural sector. Onset of the ISMR displays substantial interannual variability and controls the crop calendar and hence the agricultural output. This variability is traditionally linked to sea surface temperature (SST) anomalies over the tropical Pacific Ocean. The tropical Pacific SST underwent a regime shift during 1976/77. We report a prominent delay in the Indian summer monsoon (ISM) onset following the regime shift. The onset dates are computed with the Hydrologic Onset and Withdrawal Index, based on vertically integrated moisture transport over the Arabian Sea (AS). The shift in onset is found to be due to the change in moisture availability over the AS. A delay in the development of easterly vertical shear reduces northward-propagating intraseasonal variability during May-June, limiting the moisture supply from the equatorial Indian Ocean (IO) to the AS. This, along with enhanced precipitation over the IO during the pre-monsoon, drives a reduction in moisture availability over the AS region from pre- to post-1976/77, delaying the ISM onset in recent decades. Our findings highlight the need for the re-assessment of the crop calendar in India, which is now based on the mean onset date computed from long-term data, without considering the regime shift or trends in onset.

  13. Aerosols and contrasting monsoon conditions over the Himalayan region

    Science.gov (United States)

    Singh, Charu; Ganguly, Dilip; Dash, S. K.

    2016-05-01

    Impact of aerosols on the Indian summer monsoon (ISM) variability is well documented; however there are limited studies which have quantified the role of aerosols in modifying the amount of rainfall. To address this research problem, we make use of the remotely sensed data set of precipitation and aerosols from different observations. In the present study remotely sensed precipitation data set has been utilised to define contrasting monsoon conditions over the Himalayan region. As per the classical definition, active and break spells are defined over the central part of the Indian land region, and during the break spells over the central Indian region, the Himalayan region receives substantial amount of rainfall. It is found that accumulation of more dust over the Uttarakhand region significantly (negative correlation with rainfall; significant at 5% significance level) suppresses the rainfall during break spells. We propose that the substantial aerosol loading and its associated dynamical feedback over the Himalayan foothills may have considerable impact on the amount of rainfall over the mountainous regions of the Indian subcontinent. Results presented in this paper are supported by the statistically robust significance test and would be useful to develop the understanding of the role of aerosols in modulating the rainfall intensity during the summer monsoon season.

  14. Hunza Landslide and Monsoon Flooding in Pakistan Call for International Attention to Transboundary Natural Hazards

    Science.gov (United States)

    Kargel, J. S.; Fink, W.; Furfaro, R.; Leonard, G. J.; Patterson, M.; Glims, Gaphaz

    2010-12-01

    Two major disasters in Pakistan and innumerable lesser disasters throughout the Himalaya-Karakoram region in 2010 highlight geologic events and extreme weather (perhaps climate change) in affecting the well being of whole nations and commerce and relations between nations. Two chief events in Pakistan include the Jan. 4 rockslide into the Hunza River and the subsequent formation of a natural dam lake (Lake Gojal); and the monsoon precipitation-fed flooding across the Indus Basin. The first event severed Pakistan’s major land link with China. The second event devastated Pakistan’s national land-based transportation infrastructure and agriculture and displaced millions of people. In a country plagued by monsoon-driven floods, the lack of catastrophic breakout of Lake Gojal is welcome. Satellite-based monitoring shows the spillway to be eroding more rapidly (but not alarmingly) under August’s monsoon peak flow. Similar events have occurred before in the region and will occur again. These mega-events in Pakistan should be an alert for all of South Asia, as climate change increases or shifts the hazard environment, encroaching development and urbanization increases the vulnerabilities, and as improved capacity for trans-national commerce breaks down the Himalayan barrier and both promotes new opportunities and possible conflicts. 2010's natural mega-calamities in Pakistan and widespread landsliding and flooding elsewhere in South Asia underscores the subcontinent’s need for a thorough field-, remote sensing-, and modeling-based assessment of the disaster potential related to landslides, glacier surges, extreme monsoon precipitation events, natural glacier and landslide dam lake outbursts, and unseasonal snow melting. The Himalayan-Karakoram region is remarkable for its heterogeneous responses to climate change. For instance, some areas are undergoing rapid glacier recession and stagnation; others are undergoing glacier growth. We take the instance of the

  15. Reduction of uncertainty associated with future changes in Indian summer monsoon projected by climate models and assessment of monsoon teleconnections

    Science.gov (United States)

    Rajendran, Kavirajan; Surendran, Sajani; Kitoh, Akio; Varghese, Stella Jes

    2016-05-01

    Coupled Model Intercomparison Project phase 5 (CMIP5) coupled global climate model (CGCM) Representative Concentration Pathway (RCP) simulations project clear future temperature increase but diverse changes in Indian summer monsoon rainfall (ISMR) with substantial inter-model spread. Robust signals of projected changes are derived based on objective criteria and the physically consistent simulations with the highest reliability suggest future reduction in the frequency of light rainfall but increase in high to extreme rainfall. The role of equatorial Indian and Pacific Oceans on the projected changes in monsoon rainfall is investigated. The results of coupled model projections are also compared with the corresponding projections from high resolution AGCM time-slice, multi-physics and multi-forcing ensemble experiments.

  16. Global surface temperature signals in pine ring-width chronologies from southern monsoon Asia

    Science.gov (United States)

    Buckley, B. M.; Cook, B. I.; Bhattacharyya, A.; Dukpa, D.; Chaudhary, V.

    2005-10-01

    We analyze Pinus ring width chronologies from three locations across monsoon Asia (Bhutan, India, and Thailand) where climate is dominated by the southwest monsoon in the boreal summer. We compare these records to global surface temperatures for the past 150 years, shifting the correlations through three seasonal averages: two seasons preceding the monsoon (Dec-Feb and Mar-May), and the monsoon season itself (Jun-Sep). Clear patterns emerge for each of the chronologies that highlight links to areas of known influence on the Asian monsoon: the Indian Ocean, the tropical eastern Pacific Ocean, and the high-latitude Asian landmass. The Thai and Indian chronologies are from the same species (P. merkusii), and show a strong correlation with tropical Indian and Pacific Ocean bands. The Bhutan chronology (P. Wallichiana) is most strongly linked to climate over the north Pacific and Asian landmass. All of these correlations are strongest in seasons preceding the summer monsoon.

  17. Effects of large-scale deforestation on precipitation in the monsoon regions: remote versus local effects.

    Science.gov (United States)

    Devaraju, N; Bala, Govindasamy; Modak, Angshuman

    2015-03-17

    In this paper, using idealized climate model simulations, we investigate the biogeophysical effects of large-scale deforestation on monsoon regions. We find that the remote forcing from large-scale deforestation in the northern middle and high latitudes shifts the Intertropical Convergence Zone southward. This results in a significant decrease in precipitation in the Northern Hemisphere monsoon regions (East Asia, North America, North Africa, and South Asia) and moderate precipitation increases in the Southern Hemisphere monsoon regions (South Africa, South America, and Australia). The magnitude of the monsoonal precipitation changes depends on the location of deforestation, with remote effects showing a larger influence than local effects. The South Asian Monsoon region is affected the most, with 18% decline in precipitation over India. Our results indicate that any comprehensive assessment of afforestation/reforestation as climate change mitigation strategies should carefully evaluate the remote effects on monsoonal precipitation alongside the large local impacts on temperatures.

  18. Pleistocene Indian Monsoon rainfall variability dominated by obliquity

    Science.gov (United States)

    Gebregiorgis, D.; Hathorne, E. C.; Giosan, L.; Collett, T. S.; Nuernberg, D.; Frank, M.

    2015-12-01

    The past variability of the Indian Monsoon is mostly known from records of wind strength over the Arabian Sea while Quaternary proxy records of Indian monsoon precipitation are still lacking. Here we utilize scanning x-ray fluorescence (XRF) data from a sediment core obtained by the IODP vessel JOIDES Resolution in the Andaman Sea (Site 17) to investigate changes in sediment supply from the peak monsoon precipitation regions to the core site. We use Ti/Ca and K/Rb ratios to trace changes in terrigenous flux and weathering regime, respectively, while Zr/Rb ratios suggest grain size variations. The age model of Site 17 is based on correlation of benthic C. wuellerstorfi/C. mundulus δ18O data to the LR04 global benthic δ18O stack at a resolution of ~3 kyr (Lisiecki and Raymo, 2005) for the last 2 Myrs. In its youngest part the age model is supported by five 14C ages on planktic foraminifera and the youngest Toba ash layer (Ali et al., 2015) resulting in a nearly constant sedimentation rate of ~6.5 cm/kyr. Frequency analysis of the 4 mm resolution Ti/Ca, K/Rb, and Zr/Rb time series using the REDFIT program (Schulz and Mudelsee, 2002), reveals the three main Milankovitch orbital cycles above the 90% confidence level. Depth domain spectral analysis reveals the presence of significant cyclicity at wavelengths of 28.5 and 2.8 m corresponding to the ~400 kyr and ~41 kyr cycles, respectively, during the last 2 Myr. These records suggest that Indian monsoon variability has varied in the obliquity and eccentricity bands, the latter in particular after the mid Pleistocene transition (MPT), while strong precession forcing is lacking in this super-high resolution record. Northern summer insolation and Southern Hemisphere latent heat export are out of phase during precessional cycles, but in phase in the obliquity band, which indicates that Indian monsoon precipitation has likely been more sensitive to both NH pull and SH push mechanisms (Clemens and Prell, 2003). References Ali

  19. Effect of freshwater influx on phytoplankton in the Mandovi estuary (Goa, India) during monsoon season: Chemotaxonomy

    Digital Repository Service at National Institute of Oceanography (India)

    Parab, S.G.; Matondkar, S.G.P.; Gomes, H.R.; Goes, J.I.

    stages of the monsoon was recorded, and this data is discussed in relation to environmental changes in the Mandovi estuary during the monsoon season. Keywords: Phytoplankton; Pigment Analysis; Monsoon; Freshwater Runoff; CHEMTAX 1. Introduction... by both salinity and nutrients [8]. As an al- ternative and complement to microscopic examination, the accessory pigments estimated by High Performance Liquid-Chromatography (HPLC) provide accurate class- specific differentiation of the phytoplankton...

  20. Mangrove forest degradation indicated by mangrove-derived organic matter in the Qinzhou Bay, Guangxi, China, and its response to the Asian monsoon during the Holocene climatic optimum

    Institute of Scientific and Technical Information of China (English)

    MENG Xianwei; XIA Peng; LI Zhen; LIU Lejun

    2016-01-01

    The response of mangrove ecosystems to the Asian monsoon in the future global warming can be understood by reconstructing the development of mangrove forests during the Holocene climatic optimum (HCO), using proxies preserved in coastal sediments. The total organic matter in sediments of a segmented core, with calibrated age ranges between 5.6 and 7.7 cal. ka BP and corresponding to the HCO, from the Qinzhou Bay in Guangxi, China, is quantitatively partitioned into three end-members according to their sources: mangrove-derived, terrigenous, and marine phytoplanktonic, using a three-end-member model depicted by organic carbon isotope (δ13Corg) and the molar ratio of total organic carbon to total nitrogen (C/N). The percentage of mangrove-derived organic matter (MOM) contribution is used as a proxy for mangrove development. Three visible drops in MOM contribution occurred at ca. 7.3, ca. 6.9, and ca. 6.2 cal. ka BP, respectively, are recognized against a relatively stable and higher MOM contribution level, indicating that three distinct mangrove forest degradations occurred in the Qinzhou Bay during the HCO. The three mangrove forest degradations approximately correspond to the time of the strengthened/weakened Asian winter/summer monsoon. This indicates that even during a period favorable for the mangrove development, such as the HCO, climatic extremes, such as cold and dry events driven by the strengthened/weakened Asian winter/summer monsoon, can trigger the degradation of mangrove forests.

  1. The Asian monsoon's role in atmospheric heat transport responses to orbital and millennial-scale climate change

    Science.gov (United States)

    McGee, D.; Green, B.; Donohoe, A.; Marshall, J.

    2015-12-01

    Recent studies have provided a framework for understanding the zonal-mean position of the tropical rain belt by documenting relationships between rain belt latitude and atmospheric heat transport across the equator (Donohoe et al., 2013). Modern seasonal and interannual variability in globally-averaged rain belt position (often referred to as 'ITCZ position') reflects the interhemispheric heat balance, with the rain belt's displacement toward the warmer hemisphere directly proportional to atmospheric heat transport into the cooler hemisphere. Model simulations suggest that rain belt shifts are likely to have obeyed the same relationship with interhemispheric heat transport in response to past changes in orbital parameters, ice sheets, and ocean circulation. This relationship implies that even small (±1 degree) shifts in the mean rain belt require large changes in hemispheric heat budgets, placing tight bounds on mean rain belt shifts in past climates. This work has primarily viewed tropical circulation in two dimensions, as a pair of zonal-mean Hadley cells on either side of the rain belt that are displaced north and south by perturbations in hemispheric energy budgets, causing the atmosphere to transport heat into the cooler hemisphere. Here we attempt to move beyond this zonal-mean perspective, motivated by arguments that the Asian monsoon system, rather than the zonal-mean circulation, plays the dominant role in annual-mean heat transport into the southern hemisphere in the modern climate (Heaviside and Czaja, 2012; Marshall et al., 2014). We explore a range of climate change experiments, including simulations of North Atlantic cooling and mid-Holocene climate, to test whether changes in interhemispheric atmospheric heat transport are primarily driven by the mean Hadley circulation, the Asian monsoon system, or other regional-scale atmospheric circulation changes. The scalings that this work identifies between Asian monsoon changes and atmospheric heat

  2. Inter-decadal variations,causes and future projection of the Asian summer monsoon

    Institute of Scientific and Technical Information of China (English)

    Ding Yihui; Si Dong; Sun Ying; Liu Yanju; Song Yafang

    2014-01-01

    The present paper presents a concise summary of our recent studies on the Asian summer monsoon, with highting decadal and inter-decadal scales. The studies on the long-term variations of the Asian summer monsoon and its impacts on the change in the summer precipitation in China are reviewed. Moreover,recent changes in the Asian summer monsoon and summer precipitation in East Asia (including Meiyu precipitation) are discussed. Finally,the future changes of the Asian summer monsoon are also pointed out in this paper.

  3. Dynamics of the Asian Summer Monsoon Onset and the Tibetan Plateau Impacts

    Science.gov (United States)

    Yimin, Liu; Guoxiong, Wu; Boqi, Liu; Suling, Ren; Yue, Guan

    2015-04-01

    The formation and development of the South Asian High (SAH) in early spring over South China Sea (SCS) provides upper tropospheric pumping over the Southeast Bay of Bengal (BOB) and leads to the BOB monsoon onset. The strong latent heat release of the BOB monsoon results in the northeastward unstable development of the SAH which contributes to the SCS monsoon onset. The zonal asymmetric unstable development of the SAH after the SCS monsoon onset leads to the Indian summer monsoon onset. In spring over South BOB, usually there is vortex development preceding the Asian summer monsoon onset. The rapid development of the BOB monsoon onset vortex is due to the local strong air-sea interaction, which is modulated by the Tibetan Plateau (TP) forcing and the land-sea thermal contrast across South Asia. Strong heating from BOB monsoon generates stationary Rossby-wave in lower troposphere, producing weak cold advection and convection over North SCS. Development of surface BOB cyclone provides Northeastward water vapor transport towards North SCS where convection develops. Before the Indian Summer Monsoon (ISM) onset, the North- South land- sea thermal contrast increases eastward remarkably on the southeast of Arabian Sea. Air traveling eastward along the near- surface tropical westerly jet gets northward accelerated, forcing a lower tropospheric convergence near and to the north of the jet stream. Such a forced convection development occurs intensively over the southeastern Arabian Sea and southwestern India, contributing to the ISM onset.

  4. Transport pathways of peroxyacetyl nitrate in the upper troposphere and lower stratosphere from different monsoon systems during the summer monsoon season

    Directory of Open Access Journals (Sweden)

    S. Fadnavis

    2014-08-01

    Full Text Available The Asian summer monsoon involves complex transport patterns with large scale redistribution of trace gases in the upper troposphere and lower stratosphere (UTLS. We employ the global chemistry–climate model ECHAM5-HAMMOZ in order to evaluate the transport pathways and the contributions of nitrogen oxide reservoir species PAN, NOx, and HNO3 from various monsoon regions, to the UTLS over Southern Asia and vice versa. The model is evaluated with trace gas retrievals from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS-E and aircraft campaigns during the monsoon season (June–September. There are three regions which contribute substantial pollution to the UTLS during the monsoon: the Asian summer monsoon (ASM, the North American Monsoon (NAM and the West African monsoon (WAM. However, penetration due to ASM convection is deeper into the UTLS as compared to NAM and WAM outflow. The circulation in these monsoon regions distributes PAN into the tropical latitude belt in the upper troposphere. Remote transport also occurs in the extratropical upper troposphere where westerly winds drive North American and European pollutants eastward to partly merge with the ASM plume. Strong ASM convection transports these remote and regional pollutants into the lower stratosphere. In the lower stratosphere the injected pollutants are transported westward by easterly winds. The intense convective activity in the monsoon regions is associated with lightning generation and thereby the emission of NOy species. This will affect the distribution of PAN in the UTLS. The estimates of lightning produced PAN, HNO3, NOx and ozone obtained from control and lightning-off simulations shows high percentage changes over the regions of convective transport especially equatorial Africa and America and comparatively less over the ASM. This indicates higher anthropogenic pollution transport from the ASM region into the UTLS.

  5. Effect of climate change on seasonal monsoon in Asia and its impact on the variability of monsoon rainfall in Southeast Asia

    Directory of Open Access Journals (Sweden)

    Yen Yi Loo

    2015-11-01

    Full Text Available Global warming and climate change is one of the most extensively researched and discussed topical issues affecting the environment. Although there are enough historical evidence to support the theory that climate change is a natural phenomenon, many research scientists are widely in agreement that the increase in temperature in the 20th century is anthropologically related. The associated effects are the variability of rainfall and cyclonic patterns that are being observed globally. In Southeast Asia the link between global warming and the seasonal atmospheric flow during the monsoon seasons shows varying degree of fuzziness. This study investigates the impact of climate change on the seasonality of monsoon Asia and its effect on the variability of monsoon rainfall in Southeast Asia. The comparison of decadal variation of precipitation and temperature anomalies before the 1970s found general increases which were mostly varying. But beyond the 1970s, global precipitation anomalous showed increases that almost corresponded with increases in global temperature anomalies for the same period. There are frequent changes and a shift westward of the Indian summer monsoon. Although precipitation is observed to be 70% below normal levels, in some areas the topography affects the intensity of rainfall. These shifting phenomenon of other monsoon season in the region are impacting on the variability of rainfall and the onset of monsoons in Southeast Asia and is predicted to delay for 15 days the onset of the monsoon in the future. The variability of monsoon rainfall in the SEA region is observed to be decadal and the frequency and intensity of intermittent flooding of some areas during the monsoon season have serious consequences on the human, financial, infrastructure and food security of the region.

  6. Effect of climate change on seasonal monsoon in Asia and its impact on the variability of monsoon rainfall in Southeast Asia

    Institute of Scientific and Technical Information of China (English)

    Yen Yi Loo; Lawal Billa; Ajit Singh

    2015-01-01

    Global warming and climate change is one of the most extensively researched and discussed topical issues affecting the environment. Although there are enough historical evidence to support the theory that climate change is a natural phenomenon, many research scientists are widely in agreement that the increase in temperature in the 20th century is anthropologically related. The associated effects are the variability of rainfall and cyclonic patterns that are being observed globally. In Southeast Asia the link between global warming and the seasonal atmospheric flow during the monsoon seasons shows varying degree of fuzziness. This study investigates the impact of climate change on the seasonality of monsoon Asia and its effect on the variability of monsoon rainfall in Southeast Asia. The comparison of decadal variation of precipitation and temperature anomalies before the 1970s found general increases which were mostly varying. But beyond the 1970s, global precipitation anomalous showed increases that almost corresponded with increases in global temperature anomalies for the same period. There are frequent changes and a shift westward of the Indian summer monsoon. Although precipitation is observed to be 70%below normal levels, in some areas the topography affects the intensity of rainfall. These shifting phenomenon of other monsoon season in the region are impacting on the variability of rainfall and the onset of monsoons in Southeast Asia and is predicted to delay for 15 days the onset of the monsoon in the future. The variability of monsoon rainfall in the SEA region is observed to be decadal and the frequency and intensity of intermittent flooding of some areas during the monsoon season have serious consequences on the human, financial, infrastructure and food security of the region.

  7. The Plio-Pleistocene Evolution of the Indian Ocean Monsoonal System: Evidence from the Arabian Sea and East Africa

    Science.gov (United States)

    Wilson, K. E.; Maslin, M. A.; Mackay, A. W.; Leng, M. J.; Kingston, J.; Deino, A.

    2011-12-01

    It is important to identify the teleconnections between high latitude forcing and tropical monsoonal circulation in order to understand climate change in East Africa during the Plio-Pleistocene. Here we present a record of aeolian dust transport to the Arabian Sea between approximately 2.9 and 2.3 million years ago (Ma), constructed from the high-resolution XRF scanning of sediment cores from ODP Sites 721 and 722. Variations in the delivery of aeolian dust to the Arabian Sea, reflected in normalised flux of titanium, show that monsoonal circulation prior to 2.6 Ma, and after 2.5 Ma, was highly variable and primarily driven by orbitally-forced changes in tropical summer insolation, strongly modulated by the 400,000 year cycle of orbital eccentricity. This is confirmed by the presence of lakes in the East African Rift Valley during key eccentricity maxima. The dust record is coupled with the analysis of a well-dated series of diatomite units from the Baringo-Bogoria Basin which document the rhythmic cycling of large, precessionally-driven freshwater lakes which periodically occupied the Central Kenyan Rift Valley between 2.7 and 2.58 Ma. Analysis of one of these lake sequences using stable oxygen isotope measurements of diatom silica, combined with the XRF analysis of whole-sample geochemistry, reveals that the deep lake phase was characterised by fluctuations in rainfall and lake depth over cycles lasting, on average, 1,400 years. The presence of these millennial-scale fluctuations is confirmed by evidence of abrupt climate cycles in the oceanic dust record from the Arabian Sea.

  8. Predictability experiments for the Asian summer monsoon impact of SST anomalies on interannual and intraseasonal variability

    CERN Document Server

    Molteni, F; Ferranti, L; Slingo, J M

    2003-01-01

    The effects of SST anomalies on the interannual and intraseasonal variability of the Asian summer monsoon have been studied by multivariate statistical analyses of 850-hPa wind and rainfall fields simulated in a set of ensemble integrations of the ECMWF atmospheric GCM, referred to as the PRISM experiments. The simulations used observed SSTs (PRISM-O), covering 9 years characterised by large variations of the ENSO phenomenon in the 1980's and the early 1990's. A parallel set of simulations was also performed with climatological SSTs (PRISM-C), thus enabling the influence of SST forcing on the modes of interannual and intraseasonal variability to be investigated. As in observations, the model's interannual variability is dominated by a zonally-oriented mode which describes the north-south movement of the tropical convergence zone (TCZ). This mode appears to be independent of SST forcing and its robustness between the PRISM-O and PRISM-C simulations suggests that it is driven by internal atmospheric dynamics. O...

  9. Examining Impact of Global warming on the summer monsoon system using regional Climate Model (PRECIS)

    Science.gov (United States)

    Patwardhan, S. K.; Kundeti, K.; Krishna Kumar, K.

    2011-12-01

    Every year, southwest monsoon arrives over Indian region with remarkable regularity. It hits the southern state of Kerala first by the end of May or the early June. More than 70% of the annual precipitation is received during the four monsoon months viz. June to September. This monsoon rainfall is vital for the agriculture as well as for the yearly needs of Indian population. The performance of the monsoon depends on the timely onset over southern tip of India and its progress along the entire country. This northward progression of monsoon to cover the entire Indian landmass, many times, is associated with the formation of synoptic scale system in the Bay of Bengal region and their movement along the monsoon trough region. The analysis of the observed cyclonic disturbances show that their frequency has reduced in recent decades. It is, therefore, necessary to assess the effect of global warming on the monsoon climate of India. A state-of-art regional climate modelling system, known as PRECIS (Providing REgional Climates for Impacts Studies) developed by the Hadley Centre for Climate Prediction and Research, U.K. is applied over the South Asian domain to investigate the impact of global warming on the cyclonic disturbances. The PRECIS simulations at 50 km x 50 km horizontal resolution are made for two time slices, present (1961-1990) and the future (2071-2100), for two socio-economic scenarios A2 and B2. The model skills are evaluated using observed precipitation and surface air temperature. The model has shown reasonably good skill in simulating seasonal monsoon rainfall, whereas cold bias is seen in surface air temperature especially in post-monsoon months. The typical monsoon features like monsoon trough, precipitation maxima over west coast and northeast India are well simulated by the model. The model simulations under the scenarios of increasing greenhouse gas concentrations and sulphate aerosols are analysed to study the likely changes in the quasi

  10. Propagation and effects of monsoonal seasonally intense rainfall signal in river strata

    Science.gov (United States)

    Plink-Bjorklund, P.

    2014-12-01

    Climatic forcing signals in river systems tend to be modified on different temporal and spatial scales due to inherent signal buffering, re-routing, and a complex mixing of multiple autogenic and allogenic signals. Thus climate forcing response is generally assumed inherently non-linear with significant hysteresis effects. This paper explores propagation and effects of monsoonal, seasonally intense rainfall signal in river strata in the monsoonal and bordering subtropical domains. Some such rivers occur completely within the monsoon climate zone. Others have parts of their drainages in temperate climate zones, or on high elevations and receive some of their water discharge from other sources. Yet others, have their upstream drainages in the tropical monsoon climates, but flow through bordering subtropical drylands. Yet, all these rivers characteristically experience seasonal high magnitude floods as the effect of intense monsoon precipitation. Many rivers in the bordering subtropical zone receive monsoon rain and transmit discharge only during abnormal or strengthened monsoon seasons and associated cyclonic flow. Field datasets, comparison to modern river deposits and a literature review of monsoonal and bordering subtropical domain rivers reveal that the effects of the intense seasonal monsoon rain and the resultant flooding are readily recognizable in modern and ancient fluvial strata. This paper argues that this distinct and dominant climate signal propagation occurs because it is the monsoon discharge that is commonly responsible for up to 100% of sediment erosion, transport and deposition, creating a system wide flushing or splash effect on a single season to multi-million year time scale. The distinct monsoon flood deposits are interbedded with other types of fluvial strata in systems where significant deposition also occurs from low-magnitude flood or non-flood discharges.

  11. THE CLIMATIC CHARACTERISTICS OF SUMMER MONSOON ONSET OVER THE SOUTH CHINA SEA I.40-YEAR AVERAGE

    Institute of Scientific and Technical Information of China (English)

    冯瑞权; 王安宇; 吴池胜; 林建恒; 古志明; 林文实; 谭志文

    2002-01-01

    By using 40-year NCEP reanalysis daily data (1958-1997),we have analyzed the climatic characteristics of summer monsoon onset in the South China Sea (105(E ~120(E,5(N~20(N,to be simplified as SCS in the text followed) pentad by pentad (5 days).According to our new definition,in the monsoon area of the SCS two of the following conditions should be satisfied:1) At 850hPa,the southwest winds should be greater than 2m/s.2) At 850 hPa,should be greater than 335(K.The new definition means that the summer monsoon is the southwest winds with high temperature and high moisture.The onset of the SCS summer monsoon is defined to start when one half of the SCS area (105(E~120(E,5(N~20(N) is controlled by the summer monsoon.The analyzed results revealed the following:1) The summer monsoon in the SCS starts to build up abruptly in the 4th pentad in May.2) The summer monsoon onset in the SCS is resulted from the development and intensification of southwesterly monsoon in the Bay of Bengal.3) The onset of the summer monsoon and establishment of the summer monsoon rainfall season in the SCS occur simultaneously.4) During the summer monsoon onset in the SCS,troughs deepen and widen quickly in the lower troposphere of the India;the subtropical high in the Western Pacific moves eastward off the SCS in the middle troposphere;the easterly advances northward over the SCS in the upper troposphere.

  12. Comparative Study of Monsoon Rainfall Variability over India and the Odisha State

    Directory of Open Access Journals (Sweden)

    K C Gouda

    2017-10-01

    Full Text Available Indian summer monsoon (ISM plays an important role in the weather and climate system over India. The rainfall during monsoon season controls many sectors from agriculture, food, energy, and water, to the management of disasters. Being a coastal province on the eastern side of India, Odisha is one of the most important states affected by the monsoon rainfall and associated hydro-meteorological systems. The variability of monsoon rainfall is highly unpredictable at multiple scales both in space and time. In this study, the monsoon variability over the state of Odisha is studied using the daily gridded rainfall data from India Meteorological Department (IMD. A comparative analysis of the behaviour of monsoon rainfall at a larger scale (India, regional scale (Odisha, and sub-regional scale (zones of Odisha is carried out in terms of the seasonal cycle of monsoon rainfall and its interannual variability. It is seen that there is no synchronization in the seasonal monsoon category (normal/excess/deficit when analysed over large (India and regional (Odisha scales. The impact of El Niño, La Niña, and the Indian Ocean Dipole (IOD on the monsoon rainfall at both scales (large scale and regional scale is analysed and compared. The results show that the impact is much more for rainfall over India, but it has no such relation with the rainfall over Odisha. It is also observed that there is a positive (negative relation of the IOD with the seasonal monsoon rainfall variability over Odisha (India. The correlation between the IAV of monsoon rainfall between the large scale and regional scale was found to be 0.46 with a phase synchronization of 63%. IAV on a sub-regional scale is also presented.

  13. Aerosol and rainfall variability over the Indian monsoon region. Distributions, trends and coupling

    Energy Technology Data Exchange (ETDEWEB)

    Gautam, R. [Maryland Univ., Baltimore County, MD (United States). Goddard Earth Science and Technology Center; NASA Goddard Space Flight Center, Greenbelt, MD (United States). Lab. for Atmospheres; Hsu, N.C.; Lau, K.M. [NASA Goddard Space Flight Center, Greenbelt, MD (United States). Lab. for Atmospheres; Kafatos, M. [Chapman Univ., Orange, CA (United States). Center of Excellence in Earth Observing

    2009-07-01

    Aerosol solar absorption over the Indian monsoon region has a potential role of modulating the monsoon circulation and rainfall distribution as suggested by recent studies based on model simulations. Prior to the onset of the monsoon, northern India is influenced by significant dust transport that constitutes the bulk of the regional aerosol loading over the Gangetic-Himalayan region. In this paper, a multi-sensor characterization of the increasing pre-monsoon aerosol loading over northern India, in terms of their spatial, temporal and vertical distribution is presented. Aerosol transport from the northwestern arid regions into the Indo-Gangetic Plains and over the foothills of the Himalayas is found to be vertically extended to elevated altitudes (up to 5 km) as observed from the space-borne lidar measurements (CALIPSO). In relation with the enhanced pre-monsoon aerosol loading and the associated solar absorption effects on tropospheric temperature anomalies, this paper investigates the monsoon rainfall variability over India in recent past decades from an observational viewpoint. It is found that the early summer monsoon rainfall over India is on the rise since 1950s, as indicated by historical rainfall data, with over 20% increase for the period 1950-2004. This large sustained increase in the early summer rainfall is led by the observed strengthening of the pre-monsoon tropospheric land-sea thermal gradient over the Indian monsoon region as indicated by microwave satellite measurements (MSU) of tropospheric temperatures from 1979-2007. Combined analysis of changes in tropospheric temperatures and summer monsoon rainfall in the past three decades, suggest a future possibility of an emerging rainfall pattern of a wetter monsoon over South Asia in early summer followed by a drier period. (orig.)

  14. Towards understanding the unusual Indian monsoon in 2009

    Indian Academy of Sciences (India)

    P A Francis; Sulochana Gadgil

    2010-08-01

    The Indian summer monsoon season of 2009 commenced with a massive deficit in all-India rainfallof 48% of the average rainfall in June. The all-India rainfall in July was close to the normal but that in August was deficit by 27%. In this paper, we first focus on June 2009, elucidating the special features and attempting to identify the factors that could have led to the large deficit in rainfall. In June 2009, the phase of the two important modes, viz., El Niño and Southern Oscillation (ENSO) and the equatorial Indian Ocean Oscillation (EQUINOO) was unfavourable. Also, the eastern equatorial Indian Ocean (EEIO) was warmer than in other years and much warmer than the Bay. In almost all the years, the opposite is true, i.e., the Bay is warmer than EEIO in June. It appears that this SST gradient gave an edge to the tropical convergence zone over the eastern equatorial Indian Ocean, in competition with the organized convection over the Bay. Thus, convection was not sustained for more than three or four days over the Bay and no northward propagations occurred. We suggest that the reversal of the sea surface temperature (SST) gradient between the Bay of Bengal and EEIO, played a critical role in the rainfall deficit over the Bay and hence the Indian region. We also suggest that suppression of convection over EEIO in association with the El Niño led to a positive phase of EQUINOO in July and hence revival of the monsoon despite the El Niño. It appears that the transition to a negative phase of EQUINOO in August and the associated large deficit in monsoon rainfall can also be attributed to the El Niño.

  15. Response of Asian Summer Monsoon to CO2 Doubling

    Institute of Scientific and Technical Information of China (English)

    ZHENG Jian; LIU Qinyu; HUANG Fei

    2011-01-01

    Based on simulations of the IPCC 20C3M and SRES A1B experiments in ten coupled models,the Asian summer monsoon (ASM) response to CO2 doubling and the different responses among models are examined.Nine models show the similar results that the weakening of land-ocean thermal contrast caused by the CO2 doubling contributes to a weaker large-scale ASM circulation.Further analysis in this study also shows that the major ASM components,such as the Somali cross-equatorial flow,the low level India-South China Sea monsoon trough,and the upper level tropical easterly jet stream,weaken as CO2 doubles.However,the ASM rainfall increases as a result of the increased moisture from the warmer Indian Ocean and the South China Sea,and the enhanced northward moisture transport over the ASM region.For the response of enhanced northward moisture transport over South Asia,the positive contribution of moisture content increase in the Indian Ocean is dominant and the negative contribution of the weaker monsoon circulation is secondary at 850 hPa,but both have positive contribution to the total moisture transport along the East China coast.The paradox of the weaker ASM circulation and the increasing precipitation in CO2 doubling is confirmed.It is found that strengthening of northward moisture transport could intensify the precipitation and atmospheric heat source over the north Arabian Sea and East China,and result in enhanced southwesterly at 850hPa as global warming occurs.All ten models show significant enhanced southwesterly response over the north Arabian Sea,and six of them show enhanced southwesterly response along the East China coast.

  16. Three million years of monsoon variability over the northern Sahara

    Energy Technology Data Exchange (ETDEWEB)

    Larrasoana, J.C.; Roberts, A.P.; Rohling, E.J.; Winklhofer, M. [School of Ocean and Earth Science, Southampton Oceanography Centre, University of Southampton, European Way, Southampton SO14 3ZH (United Kingdom); Wehausen, R. [Institut fuer Chemie und Biologie des Meeres (ICBM), Carl-von-Ossietzky-Universitaet, 26111, Oldenburg (Germany)

    2003-12-01

    We present a 3 million year record of aeolian dust supply into the eastern Mediterranean Sea, based on hematite contents derived from magnetic properties of sediments from Ocean Drilling Program Site 967. Our record has an average temporal resolution of {proportional_to}400 years. Geochemical data validate this record of hematite content as a proxy for the supply of aeolian dust from the Sahara. We deduce that the aeolian hematite in eastern Mediterranean sediments derives from the eastern Algerian, Libyan, and western Egyptian lowlands located north of the central Saharan watershed ({proportional_to}21 N). In corroboration of earlier work, we relate dust flux minima to penetration of the African summer monsoon front to the north of the central Saharan watershed. This would have enhanced soil humidity and vegetation cover in the source regions, in agreement with results from ''green Sahara'' climate models. Our results indicate that this northward monsoon penetration recurred during insolation maxima throughout the last 3 million years. As would be expected, this orbital precession-scale mechanism is modulated on both short ({proportional_to}100-kyr) and long ({proportional_to}400-kyr) eccentricity time scales. We also observe a strong expression of the {proportional_to}41-kyr (obliquity) cycle, which we discuss in terms of high- and low-latitude mechanisms that involve Southern Hemisphere meridional temperature contrasts and shifts in the latitudes of the tropics, respectively. We also observe a marked increase in sub-Milankovitch variability around the mid-Pleistocene transition ({proportional_to}0.95 Ma), which suggests a link between millennial-scale climate variability, including monsoon dynamics, and the size of northern hemisphere ice sheets. (orig.)

  17. South American Summer Monsoon history recorded in Brazilian speleothems

    Science.gov (United States)

    Wang, X.; Auler, A. S.; Edwards, R. L.; Cheng, H.

    2008-12-01

    We have obtained three high-resolution oxygen isotopic records of cave calcites from Caverna Botuverá, southern Brazil, Gruta do Padre, central Brazil, and Caverna Paraíso, Amazonian Brazil. All three records have chronologies determined by U-Th dates and span the last 90, 20 and 50 thousand years, respectively. Tests for equilibrium conditions show that their oxygen isotopic variations are primarily caused by climate change. The three records thus can provide information about precipitation history and fluctuations of the South American Summer Monsoon along a latitudinal transect from 28° S to 4° S. During the last glacial period, the three oxygen isotopic profiles show abrupt millennial-scale variations, which are anti- correlated with the Chinese speleothem monsoon records and northern high-latitude ice core records. This is likely related to the displacement of the mean position of the intertropical convergence zone and associated asymmetry of Hadley cells, consistent with an oceanic meridional overturning circulation mechanism for driving the abrupt climate events. However, the three records show distinct isotopic patterns in Holocene epoch. The δ18O values in the Botuvera record decrease steadily throughout Holocene, while in the Padre record, the δ18O drops slightly until ~6-7 thousand years ago and then gradually increases until the present. The Paraiso Holocene record is similar to the Padre one, but with a much greater amplitude. Together with Andean ice core and lake records, our observations suggest asynchronous changes in Holocene monsoonal precipitation in South America, possibly related to strengthened zonal tropical air-sea interactions after the melting of the large northern ice sheets.

  18. Seasonal prediction of Indian summer monsoon: Sensitivity to persistent SST

    Indian Academy of Sciences (India)

    Sukanta Kumar Das; Sanjib Kumar Deb; C M Kishtawal; Pradip Kumar Pal

    2013-10-01

    In the present study, the assessment of the Community Atmosphere Model (CAM) developed at National Centre for Atmospheric Research (NCAR) for seasonal forecasting of Indian Summer Monsoon (ISM) with different persistent SST is reported. Towards achieving the objective, 30-year model climatology has been generated using observed SST. Upon successful simulation of climatological features of ISM, the model is tested for the simulation of ISM 2011 in forecast mode. Experiments have been conducted in three different time-phases, viz., April, May and June; using different sets of initial conditions (ICs) and the persistent SSTs of the previous months of the time-phases. The spatial as well as temporal distribution of model simulated rainfall suggest a below normal monsoon condition throughout the season in all the experiments. However, the rainfall anomaly shows some positive signature over north-east part of India in the month of June and August whereas the central Indian landmass had positive anomaly during August and September. The monthly accumulated All-India rainfall (AIR) over land for June to September 2011 are predicted to be 101% (17.6 cm), 86% (24.3 cm), 83% (21.0 cm) and 95% (15.5 cm) of normal AIR, respectively. This makes the seasonal accumulated AIR 78.4 cm which is 11% below the normal rainfall of 87.6 cm. The model prediction for the months of June and July is comparable with the observation; however, the simulation would not be able to capture the high rainfall during August and September. The intention behind this work is to assess the shortcomings in the CAM model prediction, which can later be improved for future monsoon forecast experiments.

  19. Indian monsoon cycles through the last twelve million years

    Digital Repository Service at National Institute of Oceanography (India)

    Gupta, S.M.

    stream_size 98222 stream_content_type text/plain stream_name Earth_Sci_India_3_248.pdf.txt stream_source_info Earth_Sci_India_3_248.pdf.txt Content-Encoding UTF-8 Content-Type text/plain; charset=UTF-8 Open access e...) and ~21st December (longest night), respectively. Twice crossing over of equator by Sun heats up the tropical ocean, evaporates surface waters, makes clouds, which get transported by the monsoonal winds blowing towards India and resulting into rains...

  20. The Indian summer monsoon and the waters around India

    Digital Repository Service at National Institute of Oceanography (India)

    Shetye, S.R.

    the surface salinity. We shall see in the next two sections that there exists, at least in part, a positive feedback between the strength of the monsoon activity over the Bay and the low salinities there. 4. The ET and the seas around India The first clue... this talk with a diagram (Fig. 6) that summarizes the many elements that cooperate to make the ISM happen. An interesting feature of the series of processes we have examined is positive feedback. Over the Bay of Bengal it acts as follows. A warm Bay sustains...

  1. Linking hemispheric radiation budgets, ITCZ shifts, and monsoons

    Science.gov (United States)

    McGee, D.; Donohoe, A.; Marshall, J.; Ferreira, D.

    2014-12-01

    We explore the relationship between the Intertropical Convergence Zone (ITCZ), hemispheric heat budgets, and monsoon strength in past climates. Modern seasonal and interannual variability in the globally-averaged position of the ITCZ (as estimated by the tropical precipitation centroid) reflects the interhemispheric heat balance, with the ITCZ's displacement toward the warmer hemisphere directly proportional to atmospheric heat transport into the cooler hemisphere. Model simulations suggest that ITCZ shifts are likely to have obeyed the same relationship with interhemispheric heat transport in response to past changes in orbital parameters, ice sheets, and ocean circulation. This relationship implies that even small (±1 degree) shifts in the mean (annually and zonally averaged) ITCZ require large changes in hemispheric heat budgets, placing tight bounds on mean ITCZ shifts in past climates. To test this energetic argument, we use the observed relationship between mean ITCZ position and tropical sea surface temperature (SST) gradients in combination with proxy-based estimates of past SST gradients to show that mean ITCZ shifts for the mid-Holocene, Heinrich Stadial 1 and Last Glacial Maximum are not likely to have been more than 1 degree latitude from its present mean position. In exploring these results, we provide brief descriptions of the estimated radiation budgets of past climates that help demonstrate how different climate forcings change the interhemispheric heat balance and thus the ITCZ's global-mean position. We also address the seeming inconsistency between the small ITCZ shifts indicated by energetic constraints and the large changes in monsoon rainfall suggested by proxy data. We compare global-average and regional-scale tropical precipitation in observations and explore their responses to a variety of forcings (orbital changes, ice sheets, hosing) in models. These comparisons make clear that monsoon precipitation can change substantially even in the

  2. Extended Range Prediction of Indian Summer Monsoon: Current status

    Science.gov (United States)

    Sahai, A. K.; Abhilash, S.; Borah, N.; Joseph, S.; Chattopadhyay, R.; S, S.; Rajeevan, M.; Mandal, R.; Dey, A.

    2014-12-01

    The main focus of this study is to develop forecast consensus in the extended range prediction (ERP) of monsoon Intraseasonal oscillations using a suit of different variants of Climate Forecast system (CFS) model. In this CFS based Grand MME prediction system (CGMME), the ensemble members are generated by perturbing the initial condition and using different configurations of CFSv2. This is to address the role of different physical mechanisms known to have control on the error growth in the ERP in the 15-20 day time scale. The final formulation of CGMME is based on 21 ensembles of the standalone Global Forecast System (GFS) forced with bias corrected forecasted SST from CFS, 11 low resolution CFST126 and 11 high resolution CFST382. Thus, we develop the multi-model consensus forecast for the ERP of Indian summer monsoon (ISM) using a suite of different variants of CFS model. This coordinated international effort lead towards the development of specific tailor made regional forecast products over Indian region. Skill of deterministic and probabilistic categorical rainfall forecast as well the verification of large-scale low frequency monsoon intraseasonal oscillations has been carried out using hindcast from 2001-2012 during the monsoon season in which all models are initialized at every five days starting from 16May to 28 September. The skill of deterministic forecast from CGMME is better than the best participating single model ensemble configuration (SME). The CGMME approach is believed to quantify the uncertainty in both initial conditions and model formulation. Main improvement is attained in probabilistic forecast which is because of an increase in the ensemble spread, thereby reducing the error due to over-confident ensembles in a single model configuration. For probabilistic forecast, three tercile ranges are determined by ranking method based on the percentage of ensemble members from all the participating models falls in those three categories. CGMME further

  3. A composite study of onset of the Australian summer monsoon

    Science.gov (United States)

    Hendon, Harry H.; Liebmann, Brant

    1990-01-01

    The circulation changes that accompany an onset (defined as the first occurrence of wet 850-mb westerly winds at Darwin, Australia) of the Australian summer monsoon are documented by a composite study for the years 1957-1987. Composites of atmospheric fields at stations in and about the Australian tropics are constructed relative to the onset data at Darwin. It is shown that the composite onset is dominated by a slow eastward migration of a deep-baroclinic convective circulation displaced south of the equator. This propagating anomaly exhibited many features of the so-called 40-50 day oscillation, including an upper level anticyclone that accompanies the convective anomaly.

  4. On the role of the cross equatorial flow on summer monsoon rainfall over India using NCEP/NCAR reanalysis data

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar, M.R.; Shenoi, S.S.C.; Schluessel, P.

    monsoon using satellite data. Bound.- Layer Meteorl., 51, 199–209. Webster, P. J., Magana, V. O., Palmer, T. N., Shukla, J., Tomas, R. A., Yanai, M., Yasunari, T., 1998: Monsoons: Processes, Predictability and Prospects for prediction. J. Geophys. Res...

  5. Transport pathways of CO in the African upper troposphere during the monsoon season: a study based upon the assimilation of spaceborne observations

    Directory of Open Access Journals (Sweden)

    B. Barret

    2008-06-01

    Full Text Available The transport pathways of carbon monoxide (CO in the African Upper Troposphere (UT during the West African Monsoon (WAM is investigated through the assimilation of CO observations by the Aura Microwave Limb Sounder (MLS in the MOCAGE Chemistry Transport Model (CTM. The assimilation setup, based on a 3-D First Guess at Assimilation Time (3-D-FGAT variational method is described. Comparisons between the assimilated CO fields and in situ airborne observations from the MOZAIC program between Europe and both Southern Africa and Southeast Asia show an overall good agreement around the lowermost pressure level sampled by MLS (~215 hPa. The 4-D assimilated fields averaged over the month of July 2006 have been used to determine the main dynamical processes responsible for the transport of CO in the African UT. The studied period corresponds to the second AMMA (African Monsoon Multidisciplinary Analyses aircraft campaign. At 220 hPa, the CO distribution is characterized by a latitudinal maximum around 5° N mostly driven by convective uplift of air masses impacted by biomass burning from Southern Africa, uplifted within the WAM region and vented predominantly southward by the upper branch of the winter hemisphere Hadley cell. Above 150 hPa, the African CO distribution is characterized by a broad maximum over northern Africa. This maximum is mostly controlled by the large scale UT circulation driven by the Asian Summer Monsoon (ASM and characterized by the Asian Monsoon Anticyclone (AMA centered at 30° N and the Tropical Easterly Jet (TEJ on the southern flank of the anticyclone. Asian pollution uplifted to the UT over large region of Southeast Asia is trapped within the AMA and transported by the anticyclonic circulation over Northeast Africa. South of the AMA, the TEJ is responsible for the tranport of CO-enriched air masses from India and Southeast Asia over Africa. Using the high time resolution provided by the 4-D assimilated fields, we give evidence

  6. Gridded daily Indian monsoon rainfall for 14 seasons: Merged TRMM and IMD gauge analyzed values

    Indian Academy of Sciences (India)

    Ashis K Mitra; I M Momin; E N Rajagopal; S Basu; M N Rajeevan; T N Krishnamurti

    2013-10-01

    Indian monsoon is an important component of earth’s climate system. Daily rainfall data for longer period is vital to study components and processes related to Indian monsoon. Daily observed gridded rainfall data covering both land and adjoining oceanic regions are required for numerical model validation and model development for monsoon. In this study, a new gridded daily Indian rainfall dataset at 1° × 1° latitude/longitude resolution covering 14 monsoon seasons (1998–2011) are described. This merged satellite gauge rainfall dataset (NMSG) combines TRMM TMPA rainfall estimates with gauge information from IMD gridded data. Compared to TRMM and GPCP daily rainfall data, the current NMSG daily data has more information due to inclusion of local gauge analysed values. In terms of bias and skill scores this dataset is superior to other daily rainfall datasets. In a mean climatological sense and also for anomalous monsoon seasons, this merged satellite gauge data brings out more detailed features of monsoon rainfall. The difference of NMSG and GPCP looks significant. This dataset will be useful to researchers for monsoon intraseasonal studies and monsoon model development research.

  7. Revisiting Asian monsoon formation and change associated with Tibetan Plateau forcing: I. Formation

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Guoxiong; Liu, Yimin; Duan, Anmin; Bao, Qing [Chinese Academy of Sciences, State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Beijing (China); Dong, Buwen [University of Reading, Department of Meteorology, National Centre for Atmospheric Science, Reading (United Kingdom); Liang, Xiaoyun [China Meteorological Administration, National Climate Center, Beijing (China); Yu, Jingjing [China Meteorological Administration, National Meteorological Information Center, Beijing (China)

    2012-09-15

    Numerical experiments with different idealized land and mountain distributions are carried out to study the formation of the Asian monsoon and related coupling processes. Results demonstrate that when there is only extratropical continent located between 0 and 120 E and between 20/30 N and the North Pole, a rather weak monsoon rainband appears along the southern border of the continent, coexisting with an intense intertropical convergence zone (ITCZ). The continuous ITCZ surrounds the whole globe, prohibits the development of near-surface cross-equatorial flow, and collects water vapor from tropical oceans, resulting in very weak monsoon rainfall. When tropical lands are integrated, the ITCZ over the longitude domain where the extratropical continent exists disappears as a consequence of the development of a strong surface cross-equatorial flow from the winter hemisphere to the summer hemisphere. In addition, an intense interaction between the two hemispheres develops, tropical water vapor is transported to the subtropics by the enhanced poleward flow, and a prototype of the Asian monsoon appears. The Tibetan Plateau acts to enhance the coupling between the lower and upper tropospheric circulations and between the subtropical and tropical monsoon circulations, resulting in an intensification of the East Asian summer monsoon and a weakening of the South Asian summer monsoon. Linking the Iranian Plateau to the Tibetan Plateau substantially reduces the precipitation over Africa and increases the precipitation over the Arabian Sea and the northern Indian subcontinent, effectively contributing to the development of the South Asian summer monsoon. (orig.)

  8. Active and break events of Indian summer monsoon during 1901-2014

    Digital Repository Service at National Institute of Oceanography (India)

    Pai, D.S.; Sridhar, L.; RameshKumar, M.R.

    The study lists active and break monsoon events over India over a very long period (1901-2014) identified using criteria based on a rainfall index derived over a critical high rainfall region called core monsoon zone. The break and active spells...

  9. See-saw relationship of the Holocene East Asian-Australian summer monsoon

    Science.gov (United States)

    Eroglu, Deniz; McRobie, Fiona H.; Ozken, Ibrahim; Stemler, Thomas; Wyrwoll, Karl-Heinz; Breitenbach, Sebastian F. M.; Marwan, Norbert; Kurths, Jürgen

    2016-09-01

    The East Asian-Indonesian-Australian summer monsoon (EAIASM) links the Earth's hemispheres and provides a heat source that drives global circulation. At seasonal and inter-seasonal timescales, the summer monsoon of one hemisphere is linked via outflows from the winter monsoon of the opposing hemisphere. Long-term phase relationships between the East Asian summer monsoon (EASM) and the Indonesian-Australian summer monsoon (IASM) are poorly understood, raising questions of long-term adjustments to future greenhouse-triggered climate change and whether these changes could `lock in' possible IASM and EASM phase relationships in a region dependent on monsoonal rainfall. Here we show that a newly developed nonlinear time series analysis technique allows confident identification of strong versus weak monsoon phases at millennial to sub-centennial timescales. We find a see-saw relationship over the last 9,000 years--with strong and weak monsoons opposingly phased and triggered by solar variations. Our results provide insights into centennial- to millennial-scale relationships within the wider EAIASM regime.

  10. INTRODUCING A NEW INTERNATIONAL PROGRAM: MONSOON ASIA INTEGRATED REGIONAL STUDY (MAIRS)

    Institute of Scientific and Technical Information of China (English)

    Congbin Fu; Ailikun; Renjian Zhang; Xiaodong Yan

    2006-01-01

    The Monsoon Asia Integrated Regional Study (MAIRS) is a new Earth System Science Partnership (ESSP)program aimed at the integrated study of environmental changes over monsoon Asian region. This paper briefly introduces MAIRS, its background and concept, scientific themes and objectives, data requirements and its information system, intensive observation experiment, and its linkage with ongoing international projects.

  11. See–saw relationship of the Holocene East Asian–Australian summer monsoon

    Science.gov (United States)

    Eroglu, Deniz; McRobie, Fiona H.; Ozken, Ibrahim; Stemler, Thomas; Wyrwoll, Karl-Heinz; Breitenbach, Sebastian F. M.; Marwan, Norbert; Kurths, Jürgen

    2016-01-01

    The East Asian–Indonesian–Australian summer monsoon (EAIASM) links the Earth's hemispheres and provides a heat source that drives global circulation. At seasonal and inter-seasonal timescales, the summer monsoon of one hemisphere is linked via outflows from the winter monsoon of the opposing hemisphere. Long-term phase relationships between the East Asian summer monsoon (EASM) and the Indonesian–Australian summer monsoon (IASM) are poorly understood, raising questions of long-term adjustments to future greenhouse-triggered climate change and whether these changes could ‘lock in' possible IASM and EASM phase relationships in a region dependent on monsoonal rainfall. Here we show that a newly developed nonlinear time series analysis technique allows confident identification of strong versus weak monsoon phases at millennial to sub-centennial timescales. We find a see–saw relationship over the last 9,000 years—with strong and weak monsoons opposingly phased and triggered by solar variations. Our results provide insights into centennial- to millennial-scale relationships within the wider EAIASM regime. PMID:27666662

  12. Modelling the impacts of deforestation on monsoon rainfall in West Africa

    Energy Technology Data Exchange (ETDEWEB)

    Abiodun, B J [Department of Environmental and Geographical Science, University of Cape Town (South Africa); Pal, J S [Department of Civil Engineering and Environmental Science, Loyola Marymount University, California (United States); Afiesimama, E A [WMO Regional Research and Training Institute, Lagos (Nigeria); Gutowski, W J [Department of Geological and Atmospheric Sciences, Iowa State University, Iowa (United States); Adedoyin, A, E-mail: babiodun@csag.uct.ac.z [Department of Physics, University of Botswana, Gaborone (Botswana)

    2010-08-15

    The study found that deforestation causes more monsoon moisture to be retained in the mid-troposphere, thereby reducing the northward transport of moisture needed for rainfall over West Africa. Hence, deforestation has dynamical impacts on the West African monsoon and rainfall.

  13. See-saw relationship of the Holocene East Asian-Australian summer monsoon.

    Science.gov (United States)

    Eroglu, Deniz; McRobie, Fiona H; Ozken, Ibrahim; Stemler, Thomas; Wyrwoll, Karl-Heinz; Breitenbach, Sebastian F M; Marwan, Norbert; Kurths, Jürgen

    2016-09-26

    The East Asian-Indonesian-Australian summer monsoon (EAIASM) links the Earth's hemispheres and provides a heat source that drives global circulation. At seasonal and inter-seasonal timescales, the summer monsoon of one hemisphere is linked via outflows from the winter monsoon of the opposing hemisphere. Long-term phase relationships between the East Asian summer monsoon (EASM) and the Indonesian-Australian summer monsoon (IASM) are poorly understood, raising questions of long-term adjustments to future greenhouse-triggered climate change and whether these changes could 'lock in' possible IASM and EASM phase relationships in a region dependent on monsoonal rainfall. Here we show that a newly developed nonlinear time series analysis technique allows confident identification of strong versus weak monsoon phases at millennial to sub-centennial timescales. We find a see-saw relationship over the last 9,000 years-with strong and weak monsoons opposingly phased and triggered by solar variations. Our results provide insights into centennial- to millennial-scale relationships within the wider EAIASM regime.

  14. FEATURES AND COMPARISONS OF THE QUASI-BIENNIAL VARIATIONS IN THE ASIA-PACIFIC MONSOON SUBSYSTEMS

    Institute of Scientific and Technical Information of China (English)

    ZHENG Bin; LI Chun-hui; LIN Ai-lan; GU De-jun

    2009-01-01

    The National Centers for Environmental Prediction (NCEP) reanalysis data Climate Diagnostics Center Merged Analysis of Precipitation (CMAP) results,and NOAA Extended Reconstructed Sea Surface Temperature (SST),have been utilized in this paper to study the quasi-biennial variations in Asia-Pacific monsoon subsystems and associated SST anomalies (SSTA) and wind anomalies. Four monsoon indices are computed fi,om NCEP/National Center for Atmospheric Research (NCAR) reanalysis to represent the South Asian monsoon (SAM),South China Sea summer monsoon (SCSSM),Western North Pacific monsoon (WNPM) and East Asian monsoon (EAM),respectively. The quasi-biennial periods are very significant in Asia-Pacific monsoons (as discovered by power spectrum analysis),and for SAM and EAM---with moderate effects by EI Ni(n)o-Southern Oscillation (ENSO)---the quasi-biennial periods are the most important factor. For SCSSM and WNPM (once again due to the effects of ENSO),the quasi-biennial periods are of secondary durations. There are obvious interdecadal variations in the quasi-biennial modes of the Asia-Pacific monsoon,so in the negative phase the biennial modes will not be significant or outstanding. The wind anomalies and SSTA associated with the biennial modes are very different in the SAM. WNPM and EAM regions. Since the WNPM and SCSSM are very similar in the biennial modes,they can be combined into one subsystem,called SCS/WNPM.

  15. Why is Bay of Bengal warmer than Arabian Sea during the summer monsoon?

    Digital Repository Service at National Institute of Oceanography (India)

    Shenoi, S.S.C.; Shankar, D.; Shetye, S.R.

    the summer monsoon. In the Arabian Sea, the winds associated with the summer monsoon are stronger and favour the transfer of heat to deeper layers owing to overturning and turbulent mixing. In contrast, the weaker winds over the bay force a relatively...

  16. The value of C sub(e) for the Arabian Sea during summer monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, A.S.; Sadhuram, Y.; Krishna, V.V.G.

    We estimate, from the moisture budget the bulk aerodynamic coefficient for latent heat flux (C sub(e)) during the monsoon season over the central Arabian Sea. The average value of C sub(e) under active monsoon conditions was found to be 2.25 x 10...

  17. The effect of regional changes in anthropogenic aerosols on rainfall of the East Asian Summer Monsoon

    Directory of Open Access Journals (Sweden)

    L. Guo

    2013-02-01

    Full Text Available The response of East Asian Summer Monsoon (EASM precipitation to long term changes in regional anthropogenic aerosols (sulphate and black carbon is explored in an atmospheric general circulation model, the atmospheric component of the UK High-Resolution Global Environment Model v1.2 (HiGAM. Separately, sulphur dioxide (SO2 and black carbon (BC emissions in 1950 and 2000 over East Asia are used to drive model simulations, while emissions are kept constant at year 2000 level outside this region. The response of the EASM is examined by comparing simulations driven by aerosol emissions representative of 1950 and 2000. The aerosol radiative effects are also determined using an off-line radiative transfer model. During June, July and August, the EASM was not significantly changed as either SO2 or BC emissions increased from 1950 to 2000 levels. However, in September, precipitation is significantly decreased by 26.4% for sulphate aerosol and 14.6% for black carbon when emissions are at the 2000 level. Over 80% of the decrease is attributed to changes in convective precipitation. The cooler land surface temperature over China in September (0.8 °C for sulphate and 0.5 °C for black carbon due to increased aerosols reduces the surface thermal contrast that supports the EASM circulation. However, mechanisms causing the surface temperature decrease in September are different between sulphate and BC experiments. In the sulphate experiment, the sulphate direct and the 1st indirect radiative effects contribute to the surface cooling. In the BC experiment, the BC direct effect is the main driver of the surface cooling, however, a decrease in low cloud cover due to the increased heating by BC absorption partially counteracts the direct effect. This results in a weaker land surface temperature response to BC changes than to sulphate changes. The resulting precipitation response is also weaker, and the responses of the monsoon circulation

  18. Impacts of the East Asian Monsoon on springtime dust concentrations over China: IMPACTS OF MONSOON ON DUST

    Energy Technology Data Exchange (ETDEWEB)

    Lou, Sijia [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Now at Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Russell, Lynn M. [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Yang, Yang [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Now at Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Xu, Li [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Lamjiri, Maryam A. [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; DeFlorio, Michael J. [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Miller, Arthur J. [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Ghan, Steven J. [Now at Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Liu, Ying [Now at Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Singh, Balwinder [Now at Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA

    2016-07-12

    We use 150 year preindustrial simulations of the Community Earth System Model to quantify the impacts of the East Asian Monsoon strength on interannual variations of springtime dust concentrations over China. The simulated interannual variations in March-April-May (MAM) dust column concentrations range between 20–40% and 10–60% over eastern and western China, respectively. The dust concentrations over eastern China correlate negatively with the East Asian Monsoon (EAM) index, which represents the strength of monsoon, with a regionally averaged correlation coefficient of 0.64. Relative to the strongest EAM years, MAMdust concentrations in the weakest EAM years are higher over China, with regional relative differences of 55.6%, 29.6%, and 13.9% in the run with emissions calculated interactively and of 33.8%, 10.3%, and 8.2% over eastern, central, and western China, respectively, in the run with prescribed emissions. Both interactive run and prescribed emission run show the similar pattern of climate change between the weakest and strongest EAM years. Strong anomalous northwesterly and westerly winds over the Gobi and Taklamakan deserts during the weakest EAM years result in larger transport fluxes, and thereby increase the dust concentrations over China. These differences in dust concentrations between the weakest and strongest EAM years (weakest-strongest) lead to the change in the net radiative forcing by up to 8 and 3Wm2 at the surface, compared to 2.4 and +1.2Wm2 at the top of the atmosphere over eastern and western China, respectively.

  19. Transport pathways of peroxyacetyl nitrate in the upper troposphere and lower stratosphere from different monsoon systems during the summer monsoon season

    Directory of Open Access Journals (Sweden)

    S. Fadnavis

    2015-06-01

    Full Text Available The Asian summer monsoon involves complex transport patterns with large scale redistribution of trace gases in the upper troposphere and lower stratosphere (UTLS. We employ the global chemistry-climate model ECHAM5-HAMMOZ in order to evaluate the transport pathways and the contributions of nitrogen oxide species PAN, NOx, and HNO3 from various monsoon regions, to the UTLS over Southern Asia and vice versa. Simulated long term seasonal mean mixing ratios are compared with trace gas retrievals from the Michelson Interferometer for Passive Atmospheric Sounding aboard ENVISAT(MIPAS-E and aircraft campaigns during the monsoon season (June–September in order to evaluate the model's ability to reproduce these transport patterns. The model simulations show that there are three regions which contribute substantial pollution to the South Asian UTLS: the Asian summer monsoon (ASM, the North American Monsoon (NAM and the West African monsoon (WAM. However, penetration due to ASM convection reaches deeper into the UTLS as compared to NAM and WAM outflow. The circulation in all three monsoon regions distributes PAN into the tropical latitude belt in the upper troposphere. Remote transport also occurs in the extratropical upper troposphere where westerly winds drive North American and European pollutants eastward where they can become part of the ASM convection and be lifted into the lower stratosphere. In the lower stratosphere the injected pollutants are transported westward by easterly winds. The intense convective activity in the monsoon regions is associated with lightning and thereby the formation of additional NOx. This also affects the distribution of PAN in the UTLS. According to sensitivity simulations with and without lightning, increase in concentrations of PAN (~ 40%, HNO3 (75%, NOx (70% and ozone (30% over the regions of convective transport, especially over equatorial Africa and America and comparatively less over the ASM. This indicates that

  20. Environmental flow for Monsoon Rivers in India: The Yamuna River as a case study

    CERN Document Server

    Soni, Vikram; Singh, Diwan

    2013-01-01

    We consider the flows of Monsoon Rivers in India that will permit the river to perform all its natural functions. About 80% of the total flow for Indian rivers is during the monsoon and the remaining 20% is during the non monsoon period. By carrying out a case study of the river Yamuna in Delhi we find that at least 50% of the virgin monsoon (July to September) flow is required for the transport of the full spectrum of soil particles in the river sediment. A similar flow is needed for adequate recharge of the floodplain aquifers along river. For the non monsoon period (October to June) about 60% of the virgin flow is necessary to avoid the growth of still water algae and to support river biodiversity.

  1. Mid-Pliocene East Asian monsoon climate simulated in the PlioMIP

    Directory of Open Access Journals (Sweden)

    R. Zhang

    2013-09-01

    Full Text Available Based on simulations with 15 climate models in the Pliocene Model Intercomparison Project (PlioMIP, the regional climate of East Asia (focusing on China during the mid-Pliocene is investigated in this study. Compared to the pre-industrial, the multi-model ensemble mean (MMM of all models shows the East Asian summer winds (EASWs largely strengthen in monsoon China, and the East Asian winter winds (EAWWs strengthen in south monsoon China but slightly weaken in north monsoon China in the mid-Pliocene. The MMM of all models also illustrates a warmer and wetter mid-Pliocene climate in China. The simulated weakened mid-Pliocene EAWWs in north monsoon China and intensified EASWs in monsoon China agree well with geological reconstructions. However, there is a large model–model discrepancy in simulating mid-Pliocene EAWW, which should be further addressed in the future work of PlioMIP.

  2. Late Holocene (~ 2 ka) East Asian Monsoon variations inferred from river discharge and climate interrelationships in the Pearl River Estuary

    Digital Repository Service at National Institute of Oceanography (India)

    Nan, Q.; Li, T.; Chen, J.; Nigam, R.

    -size distributions, TOC contents, and δ13Corg variations appear to be directly related to monsoon precipitation in the sediment source area. An increased East Asian summer monsoon rainfall (EASM) and/or an enhanced East Asian winter monsoon rainfall could...

  3. Forecasting of monsoon heavy rains: challenges in NWP

    Science.gov (United States)

    Sharma, Kuldeep; Ashrit, Raghavendra; Iyengar, Gopal; Bhatla, R.; Rajagopal, E. N.

    2016-05-01

    Last decade has seen a tremendous improvement in the forecasting skill of numerical weather prediction (NWP) models. This is attributed to increased sophistication in NWP models, which resolve complex physical processes, advanced data assimilation, increased grid resolution and satellite observations. However, prediction of heavy rains is still a challenge since the models exhibit large error in amounts as well as spatial and temporal distribution. Two state-of-art NWP models have been investigated over the Indian monsoon region to assess their ability in predicting the heavy rainfall events. The unified model operational at National Center for Medium Range Weather Forecasting (NCUM) and the unified model operational at the Australian Bureau of Meteorology (Australian Community Climate and Earth-System Simulator -- Global (ACCESS-G)) are used in this study. The recent (JJAS 2015) Indian monsoon season witnessed 6 depressions and 2 cyclonic storms which resulted in heavy rains and flooding. The CRA method of verification allows the decomposition of forecast errors in terms of error in the rainfall volume, pattern and location. The case by case study using CRA technique shows that contribution to the rainfall errors come from pattern and displacement is large while contribution due to error in predicted rainfall volume is least.

  4. Hydrography of the eastern Arabian Sea during summer monsoon 2002

    Indian Academy of Sciences (India)

    D Shankar; S S C Shenoi; R K Nayak; P N Vinayachandran; G Nampoothiri; A M Almeida; G S Michael; M R Ramesh Kumar; D Sundar; O P Sreejith

    2005-10-01

    Hydrographic observations in the eastern Arabian Sea (EAS)during summer monsoon 2002 (during the first phase of the Arabian Sea Monsoon Experiment (ARMEX))include two approximately fortnight-long CTD time series.A barrier layer was observed occasionally during the two time series. These ephemeral barrier layers were caused by in situ rainfall,and by advection of low-salinity (high-salinity)waters at the surface (below the surface mixed layer).These barrier layers were advected away from the source region by the West India Coastal Current and had no discernible effect on the sea surface temperature.The three high-salinity water masses,the Arabian Sea High Salinity Water (ASHSW),Persian Gulf Water (PGW),and Red Sea Water (RSW),and the Arabian Sea Salinity Minimum also exhibited intermittency:they appeared and disappeared during the time series.The concentration of the ASHSW,PGW,and RSWdecreased equatorward,and that of the RSW also decreased offshore.The observations suggest that the RSW is advected equatorward along the continental slope off the Indian west coast.

  5. Indian summer monsoon forcing on the deglacial polar cold reversals

    Indian Academy of Sciences (India)

    Virupaxa K Banakar; Sweta Baidya; Alexander M Piotrowski; D Shankar

    2017-08-01

    The deglacial transition from the last glacial maximum at $\\sim$20 kiloyears before present (ka) to the Holocene (11.7 ka to Present) was interrupted by millennial-scale cold reversals, viz., Antarctic Cold Reversal ($\\sim$14.5–12.8 ka) and Greenland Younger Dryas ($\\sim$12.8–11.8 ka) which had different timings and extent of cooling in each hemisphere. The cause of this synchronously initiated, but different hemispheric cooling during these cold reversals (Antarctic Cold Reversal $\\sim$3∘C and Younger Dryas $\\sim$10∘C) is elusive because CO2, the fundamental forcing for deglaciation, and Atlantic meridional overturning circulation, the driver of antiphased bipolar climate response, both fail to explain this asymmetry. We use centennial-resolution records of the local surface water $\\delta ^{18}\\hbox {O}$ of the Eastern Arabian Sea, which constitutes a proxy for the precipitation associated with the Indian Summer Monsoon, and other tropical precipitation records to deduce the role of tropical forcing in the polar cold reversals. We hypothesize a mechanism for tropical forcing, via the Indian Summer Monsoons, of the polar cold reversals by migration of the Inter-Tropical Convergence Zone and the associated cross-equatorial heat transport.

  6. Impact of irrigation on the South Asian summer monsoon

    Science.gov (United States)

    Saeed, Fahad; Hagemann, Stefan; Jacob, Daniela

    2009-10-01

    The Indian subcontinent is one of the most intensely irrigated regions of the world and state of the art climate models do not account for the representation of irrigation. Sensitivity studies with the regional climate model REMO show distinct feedbacks between the simulation of the monsoon circulation with and without irrigation processes. We find that the temperature and mean sea level pressure, where the standard REMO version without irrigation shows a significant bias over the areas of Indus basin, is highly sensitive to the water used for irrigation. In our sensitivity test we find that removal of this bias has caused less differential heating between land and sea masses. This in turns reduces the westerlies entering into land from Arabian Sea, hence creating conditions favorable for currents from Bay of Bengal to intrude deep into western India and Pakistan that have been unrealistically suppressed before. We conclude that the representation of irrigated water is unavoidable for realistic simulation of south Asian summer monsoon and its response under global warming.

  7. Projected changes in South Asian summer monsoon by multi-model global warming experiments

    Science.gov (United States)

    Sabade, S. S.; Kulkarni, Ashwini; Kripalani, R. H.

    2011-03-01

    South Asian summer monsoon (June through September) rainfall simulation and its potential future changes are evaluated in a multi-model ensemble of global coupled climate models outputs under World Climate Research Program Coupled Model Intercomparison Project (WCRP CMIP3) dataset. The response of South Asian summer monsoon to a transient increase in future anthropogenic radiative forcing is investigated for two time slices, middle (2031-2050) and end of the twenty-first century (2081-2100), in the non-mitigated Special Report on Emission Scenarios B1, A1B and A2 .There is large inter-model variability in the simulation of spatial characteristics of seasonal monsoon precipitation. Ten out of the 25 models are able to simulate space-time characteristics of the South Asian monsoon precipitation reasonably well. The response of these selected ten models has been examined for projected changes in seasonal monsoon rainfall. The multi-model ensemble of these ten models projects a significant increase in monsoon precipitation with global warming. The substantial increase in precipitation is observed over western equatorial Indian Ocean and southern parts of India. However, the monsoon circulation weakens significantly under all the three climate change experiments. Possible mechanisms for the projected increase in precipitation and for precipitation-wind paradox have been discussed. The surface temperature over Asian landmass increases in pre-monsoon months due to global warming and heat low over northwest India intensifies. The dipole snow configuration over Eurasian continent strengthens in warmer atmosphere, which is conducive for the enhancement in precipitation over Indian landmass. No notable changes have been projected in the El Niño-Monsoon relationship, which is useful for predicting interannual variations of the monsoon.

  8. Subseasonal features of the Asian summer monsoon in the NCEP climate forecast system

    Institute of Scientific and Technical Information of China (English)

    Song YANG; WEN Min; R Wayne HIGGINS

    2008-01-01

    The operational climate forecast system (CFS) of the US National Centers for Environmental Prediction provides climate predic-tions over the world, and CFS products are becoming an important source of information for regional climate predictions in many Asian countries where monsoon climate dominates. Recent studies have shown that, on monthly-to-seasonal time-scales, the CFS is highly skillful in simulating and predicting the variability of the Asian monsoon. The higher-frequency variability of the Asian summer monsoon in the CFS is analyzed, using output from a version with a spectral triangular truncation of 126 waves in horizon-tal and 64 sigma layers in vertical, focusing on synoptic, quasi-biweekly, and intraseasonal time-scales. The onset processes of different regional monsoon components were investigated within Asia. Although the CFS generally overestimates variability of mon-soon on these time-scales, it successfully captures many major features of the variance patterns, especially for the synoptic time-scale. The CFS also captures the timing of summer monsoon onsets over India and the Indo-China Peninsula. However, it encoun-ters difficulties in simulating the onset of the South China Sea monsoon. The success and failure of the CFS in simulating the onset of monsoon precipitation can also be seen from the associated features of simulated atmospheric circulation processes. Overall, the CFS is capable of simulating the synoptic-to-intraseasonal variability of the Asian summer monsoon with skills. As for seasonal-to-interannual time-scales shown previously, the model is expected to possess a potential for skillful predictions of the high-frequencyvariability of the Asian monsoon.

  9. Arabian Peninsula-North Pacific Oscillation and its association with the Asian summer monsoon

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Using correlation and EOF analyses on sea level pressure from 57-year NCEP-NCAR reanalysis data, the Arabian Peninsula-North Pacific Oscillation (APNPO) is identified. The APNPO reflects the co-variability between the North Pacific high and South Asian summer monsoon low. This teleconnec- tion pattern is closely related to the Asian summer monsoon. On interannual timescale, it co-varies with both the East Asian summer monsoon (EASM) and South Asian summer monsoon (SASM); on decadal timescale, it co-varies with the EASM: both exhibit two abrupt climate changes in the middle 1960s and the late 1970s respectively. The possible physical process for the connections between the APNPO and Asian summer monsoon is then explored by analyzing the APNPO-related atmospheric circulations. The results show that with a strong APNPO, the Somali Jet, SASM flow, EASM flow, and South Asian high are all enhanced, and an anomalous anticyclone is produced at the upper level over northeast China via a zonal wave train. Meanwhile, the moisture transportation to the Asian monsoon regions is also strengthened in a strong APNPO year, leading to a strong moisture convergence over India and northern China. All these changes of circulations and moisture conditions finally result in an anoma- lous Asian summer monsoon and monsoon rainfall over India and northern China. In addition, the APNPO has a good persistence from spring to summer. The spring APNPO is also significantly corre- lated with Asian summer monsoon variability. The spring APNPO might therefore provide valuable in- formation for the prediction of Asian summer monsoon.

  10. Flavoring components of raw monsooned arabica coffee and their changes during radiation processing.

    Science.gov (United States)

    Variyar, Prasad S; Ahmad, Rasheed; Bhat, Rajeev; Niyas, Zareena; Sharma, Arun

    2003-12-31

    Volatile aroma principles, nonvolatile taste constituents (caffeine and chlorogenic and caffeic acids), and glycosidically bound aroma compounds of monsooned and nonmonsooned raw arabica coffee were analyzed using gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC). Among the most potent odor active constituents known to contribute to the aroma of the green beans, 3-isopropyl-2-methoxypyrazine, 3-isobutyl-2-methoxypyrazine, 4-vinylguaiacol, beta-damascenone, (E)-2-nonenal, trans,trans-2,4-decadienal, phenylacetaldehyde, and 3-methylbutyric acid were detected by GC-MS in both samples. A decrease in content of methoxypyrazines and an increase in 4-vinylguaiacol and isoeugenol resulted in a dominant spicy note of monsooned coffee. These phenolic compounds exist partly as their glycosides, and their release from the bound precursors during monsooning accounted for their higher content in monsooned coffee. A considerable decrease in astringent chlorogenic acid as a consequence of hydrolysis to bitter caffeic acid was noted in monsooned coffee. Radiation processing of nonmonsooned beans at a dose of 5 kGy resulted in an increased rate of monsooning. At this dose a quantitative increase in most of the aroma active components could be observed in all samples studied. Hydrolysis of chlorogenic acid to caffeic acid was noted in radiation-processed monsooned coffee beans irrespective of whether the treatment was carried out before or after monsooning. These changes were, however, not observed in irradiated, nonmonsooned coffee beans, suggesting an enzymatic rather than a radiolytic cleavage of chlorogenic acid. A rationale behind the mechanism of monsooning and radiation-induced enhancement of the monsooning process is discussed.

  11. Fault system and thermal regime in the vicinity of site NGHP-01-10, Krishna-Godavari basin, Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Dewangan, P.; Srirama, G.; Ramprasad, T.; Ramana, M.V.; Jaiswal, P.

    driven (Milkov and Sassen, 2002). In structural accumulation gases are transported to the GHSZ through features such as faults and mud 3 volcanoes, e.g. northwestern Gulf of Mexico (Brooks et al., 1986; MacDonald et al., 1994; Milkov and Sassen, 2000... horizons, e.g., Blake ridge (Xu and Ruppel, 1999; Dickens et al., 1997), Gulf of Mexico minibasins (Milkov and Sassen, 2001; Pflaum et al., 1986), Nankai trough (Matsumoto et al., 2001), and Mallik (Dallimore et al., 1999). A combination of both...

  12. Recent Progresses in Impacts of Indo-Western Pacific Ocean on East Asian Monsoon

    Science.gov (United States)

    Li, Jianping

    2016-04-01

    tropical Indian Ocean (TIO). A significant wetting trend over the MLY in winter during the three decades since the late 1970s, forming a ''mid-eastChina winter wetting'' pattern, which has become an important feature of precipitation change under the weakening East Asian winter monsoon (EAWM). It is found that the increasing TIO SST is the dominant factor responsible for recent increases in precipitation over the MLY. The thermal forcing driven bythe TIO SST warming gives rise to an anomalous cyclonic circulation along the coast of eastern China, which transports more water vapor onto the Chinese mainland, shifts and causes anomalous convergence over the MLY, and generates the increase in precipitation there. As such, the increasing SST in the TIO induces over 80% of the observed wetting trend over the MLY.

  13. Projected seasonal mean summer monsoon over India and adjoining regions for the twenty-first century

    Science.gov (United States)

    Dash, Sushil K.; Mishra, Saroj K.; Pattnayak, Kanhu C.; Mamgain, Ashu; Mariotti, Laura; Coppola, Erika; Giorgi, Filippo; Giuliani, Graziano

    2015-11-01

    In this study, we present the projected seasonal mean summer monsoon over India and adjoining regions for the twenty-first century under the representative concentration pathway (RCP) 4.5 and RCP 8.5 scenarios using the regional model RegCM4 driven by the global model GFDL-ESM2M. RegCM4 is integrated from 1970 to 2099 at 50 km horizontal resolution over the South Asia CORDEX domain. The simulated mean summer monsoon circulation and associated rainfall by RegCM4 are validated against observations in the reference period 1975 to 2004 based on the Global Precipitation Climatology Project (GPCP) and India Meteorological Department (IMD) data sets. Regional model results are also compared with those of the global model GFDL which forces the RegCM4, showing that the regional model in particular improves the simulation of precipitation trends during the reference period. Future projections are categorized as near future (2010-2039), mid future (2040-2069), and far future (2070-2099). Comparison of projected seasonal (June-September) mean rainfall from the different time slices indicate a gradual increase in the intensity of changes over some of the regions under both the RCP4.5 and RCP8.5 scenarios. RegCM4 projected rainfall decreases over most of the Indian land mass and the equatorial and northern Indian Ocean, while it increases over the Arabian Sea, northern Bay of Bengal, and the Himalayas. Results show that the monsoon circulation may become weaker in the future associated with a decrease in rainfall over Indian land points. The RegCM4 projected decrease in June, July, August, September (JJAS) rainfall under the RCP8.5 scenario over the central, eastern, and peninsular India by the end of the century is in the range of 25-40 % of their mean reference period values; it is significant at the 95 % confidence level and it is broadly in line with patterns of observed change in recent decades. Surface evaporation is projected to increase over the Indian Ocean, thereby

  14. Fine-scale responses of phytoplankton to freshwater influx in a tropical monsoonal estuary following the onset of southwest monsoon

    Indian Academy of Sciences (India)

    Suraksha M Pednekar; S G Prabhu Matondkar; Helga Do R Gomes; Joaquim I Goes; Sushma Parab; Vijaya Kerkar

    2011-06-01

    In May of 2007, a study was initiated by the National Institute of Oceanography (NIO), Goa, India, to investigate the influence of monsoonal rainfall on hydrographic conditions in the Mandovi River of India. The study was undertaken at a location ∼2 km upstream of the mouth of this estuary. During the premonsoon (PreM) in May, when circulation in the estuary was dominated by tidal activity, phytoplankton communities in the high saline (35–37 psu) waters at the study site were largely made up of the coastal neritic species Fragilaria oceanica, Ditylum brightwellii and Trichodesmium erythraeum. During the later part of the intermonsoon (InterM) phase, an abrupt decline in salinity led to a surge in phytoplankton biomass (Chlorophyll ∼14 mg m−3), of a population that was dominated by Thalassiosira eccentricus. As the southwest monsoon (SWM) progressed and the estuary freshened salinity and Chlorophyll (Chl ) concentrations decreased during the MoN, Skeletonema costatum established itself as the dominant form. Despite the low biomass (Chl > 2 mg m−3), the phytoplankton community of the MoN was the most diverse of the entire study. During the postmonsoon (PostM), the increase in salinity was marked by a surge in dinoflagellate populations comprising of Ceratium furca, Akashiwo sanguinea, and Pyrophacus horologium.

  15. Multi-proxy evidence for compositional change of organic matter in the largest tropical (peninsular) river basin of India

    Digital Repository Service at National Institute of Oceanography (India)

    Pradhan, U.K.; Ying Wu; Shirodkar, P.V.; Zhang, J.; Zhang, G.

    The distribution and compositional changes of organic matter (OM) within the Godavari river system is increasingly influenced by reduced monsoon rainfall and an increased number of damming. To track these changes stable isotopes of organic carbon...

  16. An assessment of Indian monsoon seasonal forecasts and mechanisms underlying monsoon interannual variability in the Met Office GloSea5-GC2 system

    Science.gov (United States)

    Johnson, Stephanie J.; Turner, Andrew; Woolnough, Steven; Martin, Gill; MacLachlan, Craig

    2017-03-01

    We assess Indian summer monsoon seasonal forecasts in GloSea5-GC2, the Met Office fully coupled subseasonal to seasonal ensemble forecasting system. Using several metrics, GloSea5-GC2 shows similar skill to other state-of-the-art seasonal forecast systems. The prediction skill of the large-scale South Asian monsoon circulation is higher than that of Indian monsoon rainfall. Using multiple linear regression analysis we evaluate relationships between Indian monsoon rainfall and five possible drivers of monsoon interannual variability. Over the time period studied (1992-2011), the El Niño-Southern Oscillation (ENSO) and the Indian Ocean dipole (IOD) are the most important of these drivers in both observations and GloSea5-GC2. Our analysis indicates that ENSO and its teleconnection with Indian rainfall are well represented in GloSea5-GC2. However, the relationship between the IOD and Indian rainfall anomalies is too weak in GloSea5-GC2, which may be limiting the prediction skill of the local monsoon circulation and Indian rainfall. We show that this weak relationship likely results from a coupled mean state bias that limits the impact of anomalous wind forcing on SST variability, resulting in erroneous IOD SST anomalies. Known difficulties in representing convective precipitation over India may also play a role. Since Indian rainfall responds weakly to the IOD, it responds more consistently to ENSO than in observations. Our assessment identifies specific coupled biases that are likely limiting GloSea5-GC2 Indian summer monsoon seasonal prediction skill, providing targets for model improvement.

  17. An assessment of Indian monsoon seasonal forecasts and mechanisms underlying monsoon interannual variability in the Met Office GloSea5-GC2 system

    Science.gov (United States)

    Johnson, Stephanie J.; Turner, Andrew; Woolnough, Steven; Martin, Gill; MacLachlan, Craig

    2016-06-01

    We assess Indian summer monsoon seasonal forecasts in GloSea5-GC2, the Met Office fully coupled subseasonal to seasonal ensemble forecasting system. Using several metrics, GloSea5-GC2 shows similar skill to other state-of-the-art seasonal forecast systems. The prediction skill of the large-scale South Asian monsoon circulation is higher than that of Indian monsoon rainfall. Using multiple linear regression analysis we evaluate relationships between Indian monsoon rainfall and five possible drivers of monsoon interannual variability. Over the time period studied (1992-2011), the El Niño-Southern Oscillation (ENSO) and the Indian Ocean dipole (IOD) are the most important of these drivers in both observations and GloSea5-GC2. Our analysis indicates that ENSO and its teleconnection with Indian rainfall are well represented in GloSea5-GC2. However, the relationship between the IOD and Indian rainfall anomalies is too weak in GloSea5-GC2, which may be limiting the prediction skill of the local monsoon circulation and Indian rainfall. We show that this weak relationship likely results from a coupled mean state bias that limits the impact of anomalous wind forcing on SST variability, resulting in erroneous IOD SST anomalies. Known difficulties in representing convective precipitation over India may also play a role. Since Indian rainfall responds weakly to the IOD, it responds more consistently to ENSO than in observations. Our assessment identifies specific coupled biases that are likely limiting GloSea5-GC2 Indian summer monsoon seasonal prediction skill, providing targets for model improvement.

  18. Strong winter monsoon wind causes surface cooling over India and China in the Late Miocene

    Directory of Open Access Journals (Sweden)

    H. Tang

    2015-01-01

    Full Text Available Modern Asian winter monsoon characterised by the strong northwesterly wind in East Asia and northeasterly wind in South Asia, has a great impact on the surface temperature of the Asian continent. Its outbreak can result in significant cooling of the monsoon region. However, it is still unclear whether such an impact existed and is detectable in the deep past. In this study, we use temperature reconstructions from plant and mammal fossil data together with climate model results to examine the co-evolution of surface temperature and winter monsoon in the Late Miocene (11–5 Ma, when a significant change of the Asian monsoon system occurred. We find that a stronger-than-present winter monsoon wind might have existed in the Late Miocene due to the lower Asian orography, particularly the northern Tibetan Plateau and the mountains north of it. This can lead to a pronounced cooling in southern China and northern India, which counteracts the generally warmer conditions in the Late Miocene compared to present. The Late Miocene strong winter monsoon was characterised by a marked westerly component and primarily caused by a pressure anomaly between the Tibetan Plateau and Northern Eurasia, rather than by the gradient between the Siberian High and the Aleutian Low. As a result, the close association of surface temperature with winter monsoon strength on inter-annual scale as observed at present may not have established in the Late Miocene.

  19. Interconnections between the Asian monsoon, ENSO, and high northern latitude climate during the Holocene

    Institute of Scientific and Technical Information of China (English)

    HONG Bing; LIN Qinghua; HONG Yetang

    2006-01-01

    The article emphatically reviews the research progress in interconnections between the East Asian and Indian Ocean summer monsoons, between the Asian monsoon and the El Nino-Southern Oscillation (ENSO) activity, and between the monsoon, ENSO and the changing of the North Atlantic climate during the Holocene. According to the studies of recent years, it is found that the intensity variations of the East Asian and Indian Ocean summer monsoons show an opposite relationship, which may be closely related to the phenomena of ENSO in the equatorial Pacific Ocean and the variation of the deep-water formation of the North Atlantic Ocean on the interannual to orbital time scales. The 4k and 8k events occurring at around 4200 and 8200 a BP, respectively, might be the two in a series of severe paleo-El Nino events during the Holocene, strongly reflecting the interactions and influences of the monsoons, ENSO and the North Atlantic climate. In order to better understand the relationships between these paleoclimatic phenomena, scientists need to strengthen the research work on the Asian monsoon division and the comparison between monsoon proxy records, and the study on the proxy record of sea surface temperature with high time-resolution in the equatorial Pacific Ocean and the simulation research of paleoclimate condition.

  20. Determination of summer monsoon onset and its related large-scale circulation characteristics over Pakistan

    Science.gov (United States)

    Latif, M.; Syed, F. S.

    2016-08-01

    The onset of summer monsoon over the Core Monsoon Region of Pakistan (CMRP) has been investigated in this study using observational daily rainfall and Precipitable Water (PW) data sets. An objective criterion is proposed to define monsoon onset dates by employing Precipitation Index and Normalized Precipitable Water Index techniques. The climatological mean summer monsoon onset dates over CMRP based on daily rainfall data sets are observed to be 1 July and 30 June in the station and gridded data sets, respectively. Whereas the daily PW-based climatological mean onset date is 30 June. The year-wise onset dates determined through station and gridded rainfall data sets are very similar but these dates differ in case of PW-based onsets. The evolution of large-scale circulation anomalies and thermodynamic structure leading monsoon onset over Pakistan shows that a strong positive temperature and geopotential height anomalies appear over the northwestern part of the core region in the upper atmosphere. This warm geopotential height anomaly gets strengthen as the monsoon onset approaches. The temperature anomalies are barotropic whereas the geopotential height anomalies are baroclinic with the presence of low level anticyclone over the Tibetan Plateau. A moisture convergence zone along the foothill of Himalayas and low level moisture convergence zone over the north Arabian Sea set the stage for the moisture carrying monsoon winds to blow inland towards CMRP. The moisture is mainly supplied from the Arabian Sea, as the low pressure system approaches CMRP from the Bay of Bengal.

  1. Deciphering the desiccation trend of the South Asian monsoon hydroclimate in a warming world

    Science.gov (United States)

    Krishnan, R.; Sabin, T. P.; Vellore, R.; Mujumdar, M.; Sanjay, J.; Goswami, B. N.; Hourdin, F.; Dufresne, J.-L.; Terray, P.

    2016-08-01

    Rising propensity of precipitation extremes and concomitant decline of summer-monsoon rains are amongst the most distinctive hydroclimatic signals that have emerged over South Asia since 1950s. A clear understanding of the underlying causes driving these monsoon hydroclimatic signals has remained elusive. Using a state-of-the-art global climate model with high-resolution zooming over South Asia, we demonstrate that a juxtaposition of regional land-use changes, anthropogenic-aerosol forcing and the rapid warming signal of the equatorial Indian Ocean is crucial to produce the observed monsoon weakening in recent decades. Our findings also show that this monsoonal weakening significantly enhances occurrence of localized intense precipitation events, as compared to the global-warming response. A 21st century climate projection using the same high-resolution model indicates persistent decrease of monsoonal rains and prolongation of soil drying. Critical value-additions from this study include (1) realistic simulation of the mean and long-term historical trends in the Indian monsoon rainfall (2) robust attributions of changes in moderate and heavy precipitation events over Central India (3) a 21st century projection of drying trend of the South Asian monsoon. The present findings have profound bearing on the regional water-security, which is already under severe hydrological-stress.

  2. INTENSITY INDEX OF SOUTH CHINA SEA MONSOON AND ITS VARIATION CHARACTERISTICS

    Institute of Scientific and Technical Information of China (English)

    吴尚森; 梁建茵

    2002-01-01

    According to the basic characteristics of the activities of summer monsoon in the South China Sea,a standardized index,, has been designed that integrates a dynamic factor (southwesterly component) and a thermodynamic factor (OLR) for the indication of summer monsoon in the South China Sea.With the index determined for individual months of June,July and August and the entire summertime from 1975 to 1999,specific months and years are indicated that are either strong or weak in monsoon intensity.The variation is studied for the patterns and 's relationship is revealed with the onset of summer monsoon and the precipitation in Guangdong province and China.The results show that there are quasi-10 and quasi-3-4 year cycles in the interannual variation of the monsoon over the past 25 years.When it has an early (late) onset,the summer monsoon is usually strong (weak).In the strong (weak) monsoon years,precipitation tends to be more (less) in the first raining season of the year but normal or less (normal) in the second,in the province,but it would be more (less) in northeastern China and most parts of the northern China and south of the lower reaches of the Changjiang River and less (more) in the middle and lower reaches of the river,western part of northern China and western China.

  3. The footprint of Asian monsoon dynamics in the mass and energy balance of a Tibetan glacier

    Directory of Open Access Journals (Sweden)

    T. Mölg

    2012-08-01

    Full Text Available Determinations of glacier-wide mass and energy balance are still scarce for the remote mountains of the Tibetan Plateau, where field measurements are challenging. Here we run and evaluate a physical, distributed mass balance model for Zhadang glacier (central Tibet, 30° N, based on in-situ measurements over 2009–2011 and an uncertainty estimate by Monte Carlo and ensemble strategies. The model application aims to provide the first quantification of how the Indian Summer Monsoon (ISM impacts an entire glacier over the various stages of the monsoon's annual cycle. We find a strong and systematic ISM footprint on the interannual scale. Early (late monsoon onset causes higher (lower accumulation, and reduces (increases the available energy for ablation primarily through changes in absorbed shortwave radiation. By contrast, only a weak footprint exists in the ISM cessation phase. Most striking though is the core monsoon season: local mass and energy balance variability is fully decoupled from the active/break cycle that defines large-scale atmospheric variability during the ISM. Our results demonstrate quantitatively that monsoon onset strongly affects the ablation season of glaciers in Tibet. However, we find no direct ISM impact on the glacier in the main monsoon season, which has not been acknowledged so far. This result also adds cryospheric evidence that regional modification of the large-scale monsoon flow prevails on the Tibetan Plateau in summer.

  4. The footprint of Asian monsoon dynamics in the mass and energy balance of a Tibetan glacier

    Directory of Open Access Journals (Sweden)

    T. Mölg

    2012-12-01

    Full Text Available Determinations of glacier-wide mass and energy balance are still scarce for the remote mountains of the Tibetan Plateau, where field measurements are challenging. Here we run and evaluate a physical, distributed mass balance model for Zhadang Glacier (central Tibet, 30° N based on in-situ measurements over 2009–2011 and an uncertainty estimate by Monte Carlo and ensemble strategies. The model application aims to provide the first quantification of how the Indian Summer Monsoon (ISM impacts an entire glacier over the various stages of the monsoon's annual cycle. We find a strong and systematic ISM footprint on the interannual scale. Early (late monsoon onset causes higher (lower accumulation, and reduces (increases the available energy for ablation primarily through changes in absorbed shortwave radiation. By contrast, only a weak footprint exists in the ISM cessation phase. Most striking though is the core monsoon season: local mass and energy balance variability is fully decoupled from the active/break cycle that defines large-scale atmospheric variability during the ISM. Our results demonstrate quantitatively that monsoon onset strongly affects the ablation season of glaciers in Tibet. However, we find no direct ISM impact on the glacier in the main monsoon season, which has not been acknowledged so far. This result also adds cryospheric evidence that, once the monsoon is in full swing, regional atmospheric variability prevails on the Tibetan Plateau in summer.

  5. The footprint of Asian monsoon dynamics in the mass and energy balance of a Tibetan glacier

    Science.gov (United States)

    Mölg, T.; Maussion, F.; Yang, W.; Scherer, D.

    2012-12-01

    Determinations of glacier-wide mass and energy balance are still scarce for the remote mountains of the Tibetan Plateau, where field measurements are challenging. Here we run and evaluate a physical, distributed mass balance model for Zhadang Glacier (central Tibet, 30° N) based on in-situ measurements over 2009-2011 and an uncertainty estimate by Monte Carlo and ensemble strategies. The model application aims to provide the first quantification of how the Indian Summer Monsoon (ISM) impacts an entire glacier over the various stages of the monsoon's annual cycle. We find a strong and systematic ISM footprint on the interannual scale. Early (late) monsoon onset causes higher (lower) accumulation, and reduces (increases) the available energy for ablation primarily through changes in absorbed shortwave radiation. By contrast, only a weak footprint exists in the ISM cessation phase. Most striking though is the core monsoon season: local mass and energy balance variability is fully decoupled from the active/break cycle that defines large-scale atmospheric variability during the ISM. Our results demonstrate quantitatively that monsoon onset strongly affects the ablation season of glaciers in Tibet. However, we find no direct ISM impact on the glacier in the main monsoon season, which has not been acknowledged so far. This result also adds cryospheric evidence that, once the monsoon is in full swing, regional atmospheric variability prevails on the Tibetan Plateau in summer.

  6. A Primary Study of Interaction Between Monsoon and Sea Surface Temperature in the Neighborhood Sea Area in South Aisa

    Institute of Scientific and Technical Information of China (English)

    LIU Lihong; ZHENG Zuguang; XIA Youlong; WU Hong

    2005-01-01

    Using a coupled ocean-atmosphere model simplified, and the low spectrum method and the equilibria theory, we discussed the interaction of South Asian winter and summer monsoons with sea surface temperature(SST) seasonal variation in the neighbor sea area. The results indicate that, when the winter monsoon is strong, the winter SST is low, and the SST will also be low next summer;and vice versa. When the summer monsoon is strong, the summer SST is high;and vice versa. It is inconspicuous for SST in winter that summer monsoon is strong or weak. Ocean-atmosphere interaction reinforces winter and summer monsoons,while meridional SST gradient reinforces winter monsoon and weakens summer monsoon.

  7. Sea surface height anomaly and upper ocean temperature over the Indian Ocean during contrasting monsoons

    Science.gov (United States)

    Gera, Anitha; Mitra, A. K.; Mahapatra, D. K.; Momin, I. M.; Rajagopal, E. N.; Basu, Swati

    2016-09-01

    Recent research emphasizes the importance of the oceanic feedback to monsoon rainfall over the Asian landmass. In this study, we investigate the differences in the sea surface height anomaly (SSHA) and upper ocean temperature over the tropical Indian Ocean during multiple strong and weak monsoons. Analysis of satellite derived SSHA, sea surface temperature (SST) and ocean reanalysis data reveals that patterns of SSHA, SST, ocean temperature, upper ocean heat content (UOHC) and propagations of Kelvin and Rossby waves differ during strong and weak monsoon years. During strong monsoons positive SSH, SST and UOHC anomalies develop over large parts of north Indian Ocean whereas during weak monsoons much of the north Indian Ocean is covered with negative anomalies. These patterns can be used as a standard tool for evaluating the performance of coupled and ocean models in simulating & forecasting strong and weak monsoons. The rainfall over central India is found to be significantly correlated with SSHA over the regions (Arabian Sea and West central Indian Ocean and Bay of Bengal) where SSHA is positively large during strong monsoons. The SST-SSHA correlation is also very strong over the same area. The study reveals that much convection takes place over these regions during strong monsoons. In contrast during weak monsoons, convection takes place over eastern equatorial region. These changes in SST are largely influenced by oceanic Kelvin and Rossby waves. The Rossby waves initiated in spring at the eastern boundary propagate sub-surface heat content in the ocean influencing SST in summer. The SST anomalies modulate the Hadley circulation and the moisture transport thereby contributing to rainfall over central India. Therefore oceanic Kelvin and Rossby waves influence the rainfall over central India.

  8. Impact of East Asian summer monsoon circulation on the regional aerosol distribution in observations and models

    Science.gov (United States)

    Wang, Hongli; Xie, Xiaoning; Yan, Libin; Liu, Xiaodong

    2017-06-01

    The East Asian summer monsoon (EASM) can change the spatio-temporal distribution of aerosols by influencing the aerosol horizontal and vertical transports and the wet deposition of aerosols over East Asia. In this paper, we examined the aerosol optical depth (AOD) during summer together with the intensity of the EASM based on moderate-resolution imaging spectroradiometer products on board the Terra satellite and the modeling results from the NCAR Community Atmospheric Model 5.1 in the mid-latitude monsoonal East Asia (20-45° N, 105-130° E). Our results from both observations and simulations show positive correlations of AOD with the monsoon intensity over the Northeast Asia sub-region (32.5-45° N, 105-130° E), and negative correlations with that over the southeast Asia sub-region (20-32.5° N, 105-130° E). The observed and simulated AODs were much larger over the northern sub-region and much smaller over the southern sub-region in the strongest monsoon years compared with those in the weakest monsoon years. The model results suggest that the mechanism responsible for the north-south difference in the aerosol distribution was mainly caused by lower-tropospheric meridional wind anomalies related to EASM. Compared with the weakest monsoon years, the strongest monsoon years experienced southerly wind anomalies, which enabled more aerosols to be transported northward and resulted in a convergence of aerosols over the northern sub-region. In addition, the wet deposition of aerosols reduced (enhanced) the aerosol concentrations in the northern (southern) sub-region during the strongest monsoon years compared with the weakest monsoon years, which partly offset the impact of the lower southerly winds on the aerosol distribution over East Asia.

  9. Land-sea heating contrast in an idealized Asian summer monsoon

    Energy Technology Data Exchange (ETDEWEB)

    Chou, C. [Environmental Change Research Project, Institute of Earth Sciences, Academia Sinica, Taipei, 115 (Taiwan)

    2003-07-01

    Mechanisms determining the tropospheric temperature gradient that is related to the intensity of the Asian summer monsoon are examined in an intermediate atmospheric model coupled with a mixed-layer ocean and a simple land surface model with an idealized Afro-Eurasian continent and no physical topography. These include processes involving in the influence of the Eurasian continent, thermal effects of the Tibetan Plateau and effects of sea surface temperature. The mechanical effect on the large-scale flow induced by the Plateau is not included in this study. The idealized land-sea geometry without topography induces a positive meridional tropospheric temperature gradient thus a weak Asian summer monsoon circulation. Higher prescribed heating and weaker surface albedo over Eurasia and the Tibetan Plateau, which mimic effects of different land surface processes and the thermal effect of the uplift of the Tibetan Plateau, strengthens the meridional temperature gradient, and so as cold tropical SST anomalies. The strengthened meridional temperature gradient enhances the Asian summer monsoon circulation and favors the strong convection. The corresponding monsoon rainbelt extends northward and northeastward and creates variations of the monsoon rainfall anomalies in different subregions. The surface albedo over the Tibetan Plateau has a relatively weak inverse relation with the intensity of the Asian summer monsoon. The longitudinal gradient of ENSO-like SST anomalies induces a more complicated pattern of the tropospheric temperature anomalies. First, the positive (negative) longitudinal gradient induced by the El Nino (La Nina)-like SST anomalies weakens (strengthens) the Walker circulation and the circulation between South Asia and northern Africa and therefore the intensity of the Asian summer monsoon, while the corresponding monsoon rainbelt extends northward (southward). The El Nino (La Nina)-like SST anomalies also induces colder (warmer) tropospheric temperature

  10. The Dynamic Plateau Monsoon Index and Its Association with General Circulation Anomalies

    Institute of Scientific and Technical Information of China (English)

    XUN Xueyi; HU Zeyong; MA Yaoming

    2012-01-01

    Based on monthly ECMWF reanalysis-Interim (ERA-Interim) reanalysis data,along with monthly precipitation and temperature data,the Dynamic Plateau Monsoon Index (DPMI) is defined.The results of a contrast analysis of the DPMI versus the Traditional Plateau Monsoon Index (TPMI) are described.The response of general circulation to northern Qinghai-Xizang Plateau summer monsoon anomalies and the correlation of the DPMI with general circulation anomalies are investigated.The results show that,the DPMI reflected meteorological elements better and depicted climate variation more accurately than the TPMI.In years when the plateau summer monsoon is strong,the low over the plateau and the trough near the eastern coast of Asia are deeper and higher than normal over South China.This correlation corresponds to two anomalous cyclones over the plateau and the eastern coast of Asia and an anomalous anticyclone in South China.The plateau and its adjacent regions are affected by anomalous southwesterly winds that transport more moisture to South China and cause more precipitation.The lower reaches of the Yangtze River appear to receive more precipitation by means of the strong westerly water vapor flow transported from the "large triangle affecting the region".In years when the plateau summer monsoon is weak,these are opposite.The plateau monsoon is closely related to the intensity and position of the South Asian high,and the existence of a teleconnection pattern in the mid-upper levels suggests a possible linl~ge of the East Asian monsoon and the Indian monsoon to the plateau summer monsoon.

  11. The effects of monsoons and climate teleconnections on the Niangziguan Karst Spring discharge in North China

    Science.gov (United States)

    Zhang, Juan; Hao, Yonghong; Hu, Bill X.; Huo, Xueli; Hao, Pengmei; Liu, Zhongfang

    2017-01-01

    Karst aquifers supply drinking water for 25 % of the world's population, and they are, however, vulnerable to climate change. This study is aimed to investigate the effects of various monsoons and teleconnection patterns on Niangziguan Karst Spring (NKS) discharge in North China for sustainable exploration of the karst groundwater resources. The monsoons studied include the Indian Summer Monsoon, the West North Pacific Monsoon and the East Asian Summer Monsoon. The climate teleconnection patterns explored include the Indian Ocean Dipole, E1 Niño Southern Oscillation, and the Pacific Decadal Oscillation. The wavelet transform and wavelet coherence methods are used to analyze the karst hydrological processes in the NKS Basin, and reveal the relations between the climate indices with precipitation and the spring discharge. The study results indicate that both the monsoons and the climate teleconnections significantly affect precipitation in the NKS Basin. The time scales that the monsoons resonate with precipitation are strongly concentrated on the time scales of 0.5-, 1-, 2.5- and 3.5-year, and that climate teleconnections resonate with precipitation are relatively weak and diverged from 0.5-, 1-, 2-, 2.5-, to 8-year time scales, respectively. Because the climate signals have to overcome the resistance of heterogeneous aquifers before reaching spring discharge, with high energy, the strong climate signals (e.g. monsoons) are able to penetrate through aquifers and act on spring discharge. So the spring discharge is more strongly affected by monsoons than the climate teleconnections. During the groundwater flow process, the precipitation signals will be attenuated, delayed, merged, and changed by karst aquifers. Therefore, the coherence coefficients between the spring discharge and climate indices are smaller than those between precipitation and climate indices. Further, the fluctuation of the spring discharge is not coincident with that of precipitation in most

  12. Climatology of monsoon precipitation over the Tibetan Plateau from 13-year TRMM observations

    Science.gov (United States)

    Aijuan, Bai; Guoping, Li

    2016-10-01

    Based on the 13-year data from the Tropical Rainfall Measuring Mission (TRMM) satellite during 2001-2013, the influencing geographical location of the Tibetan Plateau (Plateau) monsoon is determined. It is found that the domain of the Plateau monsoon is bounded by the latitude between 27° N and 37° N and the longitude between 60° E and 103° E. According to the annual relative precipitation, the Plateau monsoon can be divided into three sections: the Plateau winter monsoon (PWM) over Iran and Afghanistan, the Plateau summer monsoon (PSM) over the central Plateau, and the transiting zone of the Plateau monsoon (TPM) over the south, west, and east edges of the Plateau. In PWM and PSM, the monsoon climatology has a shorter rainy season with the mean annual rainfall of less than 800 mm. In TPM, it has a longer rainy season with the mean annual rainfall of more than 1800 mm. PWM experiences a single-peak monthly rainfall with the peak during January to March; PSM usually undergoes a multi-peak pattern with peaks in the warm season; TPM presents a double-peak pattern, with a strong peak in late spring to early summer and a secondary peak in autumn. The Plateau monsoon also characterizes an asymmetrical seasonal advance of the rain belt. In the east of the Plateau, the rain belt migrates in a south-north orientation under the impact of the tropical and subtropical systems' oscillation. In the west of the Plateau, the rain belt advances in an east-west direction, which is mainly controlled by the regional Plateau monsoon.

  13. Heavy Rainfall Associated with a Monsoon Depression in South China: Structure Analysis

    Institute of Scientific and Technical Information of China (English)

    JIANG Jianying; JIANG Jixi; BU Yalin; LIU Nianqing

    2008-01-01

    A heavy rainfall associated with the deepening of a monsoon depression happened in the summer of 2005.This process was first diagnostically analyzed and the 3D structure of the monsoon depression was discussed,then this structure was compared with those of the monsoon depression in South Asia and the low vortex in the Meiyu front. The results showed that the heavy rainfall directly resulted from a monsoon depression in South China, and the large-scale environment provided a favorable background for the deepening of the monsoon depression. The 3D structure of the monsoon depression was as follows. In the horizontal direction,there existed a convective cloud band to the south of the monsoon depression, which lay in a convectively instable area, with a relatively strong ascending motion in the mid and low levels of the troposphere, and the ascending motion matched well with a moist tongue, a convergence area, and a band of positive vorticity in the mid and low levels of the troposphere. In the vertical direction, the depression had an obviously cyclonic circulation in the mid and low levels of the troposphere, but no circulation from above 300 hPa. The monsoon depression corresponded to convergence and positive vorticity in the low levels, but to divergence and negative vortieity in the upper levels. The upward draft of the depression could reach the upper levels of the troposphere in the west of the depression, while the descending motion lay in the east. There was a low-level jet to the south of the depression, while the upper-level jet was not obvious. The depression was vertically warm in the upper levels and cold in the low levels, and the axis of the depression tilted southeastward with height, whose characteristics were different not only from the monsoon depression in South Asia but also from the low vortex in the Meiyu front.

  14. Toward a 530,000-year Hydroclimate History for the Southern Half of the Australasian Monsoon

    Science.gov (United States)

    Gagan, M. K.; Scroxton, N. G.; Kimbrough, A. K.; Krause, C.; Hantoro, W. S.; Ayliffe, L. K.; Dunbar, G. B.; Cheng, H.; Edwards, R. L.; Hellstrom, J. C.; Shen, C. C.; Scott-Gagan, H.; Suwargadi, B. W.; Rifai, H.

    2015-12-01

    Speleothem 18O/16O records have revealed key aspects of past hydroclimates in the northern Australasian monsoon domain on orbital to millennial scales, but much less is known about the southern half of the monsoon system. We aim to develop a hydroclimate history for the southern Australasian monsoon based on speleothems from southwest Sulawesi and Flores, Indonesia (latitudes 5-9oS), which extend back to ~530 kyr BP and 90 kyr BP, respectively. To date, the 18O/16O record for Sulawesi covers glacial terminations TIV (~340 kyr BP), TIII (~245 kyr BP) and TI (~18 kyr BP). The details of each termination are different, however two important hydroclimate patterns are emerging. First, the 18O/16O record shows sharp weakening of the monsoon immediately before each termination. This surprisingly robust pattern marks a southern extension of the northern 'weak monsoon interval', and reinforces the idea that southward monsoon displacement is a fundamental feature of terminations. Second, monsoon intensification around Sulawesi lags the rise in atmospheric CO2 and Antarctic temperature by several thousand years, but parallels the 18O/16O decrease in atmospheric O2. Our finding extends that of Wang et al. (2008) and Cheng et al. (2009) who noted the influence of the low-latitude hydrological cycle on the 18O/16O of tropical transpiration, and its potential for correlating ice core and paleomonsoon records. Further south, the 90-kyr 18O/16O record for Flores shows clear precession-scale antiphasing with China, and southerly positioning of the summer monsoon rainfall belt during Heinrich stadials. Heinrich stadials 5, 4, 2 and 1 occur during wetter intervals in Flores that accompanied relatively high southern summer insolation. Intriguingly, these events are associated with abrupt atmospheric CH4 signals that may be due to increased Southern Hemisphere CH4 production related to intensification of monsoon rainfall over southern tropical land areas (Rhodes et al., 2014).

  15. Strengthened African summer monsoon in the mid-Piacenzian

    Science.gov (United States)

    Zhang, Ran; Zhang, Zhongshi; Jiang, Dabang; Yan, Qing; Zhou, Xin; Cheng, Zhigang

    2016-09-01

    Using model results from the first phase of the Pliocene Model Intercomparison Project (PlioMIP) and four experiments with CAM4, the intensified African summer monsoon (ASM) in the mid-Piacenzian and corresponding mechanisms are analyzed. The results from PlioMIP show that the ASM intensified and summer precipitation increased in North Africa during the mid-Piacenzian, which can be explained by the increased net energy in the atmospheric column above North Africa. Further experiments with CAM4 indicated that the combined changes in the mid-Piacenzian of atmospheric CO2 concentration and SST, as well as the vegetation change, could have substantially increased the net energy in the atmospheric column over North Africa and further intensified the ASM. The experiments also demonstrated that topography change had a weak effect. Overall, the combined changes of atmospheric CO2 concentration and SST were the most important factor that brought about the intensified ASM in the mid-Piacenzian.

  16. An Indian Ocean precursor for Indian summer monsoon rainfall variability

    Science.gov (United States)

    Sreejith, O. P.; Panickal, S.; Pai, S.; Rajeevan, M.

    2015-11-01

    The Indian summer monsoon rainfall (ISMR) depicts large interannual variability strongly linked with El Niño-Southern Oscillation (ENSO). However, many of the El Niño years were not accompanied by deficient ISMR. The results from the study reveal the significant role of coupled air-sea interaction over the tropical Indian Ocean (IO) in modifying the ENSO-ISMR association. The IO warm water volume (WWV), a measure of heat content variations in the equatorial IO has strong influence on ISMR. A deepening (shoaling) of thermocline in the eastern equatorial IO (EEIO) during late boreal spring (April-May) accompanied by increase (decrease) in WWV anomalies weaken (enhance) the ISMR by enhancing (suppressing) the convection over EEIO resulting in the below (above) normal ISMR. Thus, the changes in the WWV anomalies in the EEIO along with ENSO conditions during boreal spring can be considered as a precursor for the performance of subsequent ISMR.

  17. Long range prediction of Indian summer monsoon rainfall

    Indian Academy of Sciences (India)

    A A Munot; K Krishna Kumar

    2007-02-01

    The search for new parameters for predicting the all India summer monsoon rainfall (AISMR) has been an important aspect of long range prediction of AISMR. In recent years NCEP/NCAR reanalysis has improved the geographical coverage and availability of the data and this can be easily updated. In this study using NCEP/NCAR reanalysis data on temperature, zonal and meridional wind at different pressure levels, few predictors are identified and a prediction scheme is developed for predicting AISMR. The regression coeffcients are computed by stepwise multiple regression procedure. The final equation explained 87% of the variance with multiple correlation coeffcient (MCC), 0.934. The estimated rainfall in the El-Nino year of 1997 was -1.7% as against actual of 4.4%. The estimated rainfall deficiency in both the recent deficient years of 2002 and 2004 were -19.5% and -8.5% as against observed -20.4% and -11.5% respectively.

  18. Trends and variability of droughts over the Indian monsoon region

    Directory of Open Access Journals (Sweden)

    Ganeshchandra Mallya

    2016-06-01

    Full Text Available Drought characteristics for the Indian monsoon region are analyzed using two different datasets and standard precipitation index (SPI, standardized precipitation-evapotranspiration index (SPEI, Gaussian mixture model-based drought index (GMM-DI, and hidden Markov model-based drought index (HMM-DI for the period 1901–2004. Drought trends and variability were analyzed for three epochs: 1901–1935, 1936–1971 and 1972–2004. Irrespective of the dataset and methodology used, the results indicate an increasing trend in drought severity and frequency during the recent decades (1972–2004. Droughts are becoming more regional and are showing a general shift to the agriculturally important coastal south-India, central Maharashtra, and Indo-Gangetic plains indicating higher food security and socioeconomic vulnerability in the region.

  19. Developer Driven and User Driven Usability Evaluations

    DEFF Research Database (Denmark)

    Bruun, Anders

    2013-01-01

    Usability evaluation provide software development teams with insights on the degree to which a software application enables a user to achieve his/her goals, how fast these goals can be achieved, how easy it is to learn and how satisfactory it is in use Although usability evaluations are crucial....... The four primary findings from my studies are: 1) The developer driven approach reveals a high level of thoroughness and downstream utility. 2) The user driven approach has higher performance regarding validity 3) The level of reliability is comparable between the two approaches. 4) The user driven...

  20. Teleconnections associated with Northern Hemisphere summer monsoon intraseasonal oscillation

    Science.gov (United States)

    Moon, Ja-Yeon; Wang, Bin; Ha, Kyung-Ja; Lee, June-Yi

    2013-06-01

    The boreal summer intraseasonal oscillation (BSISO) has strong convective activity centers in Indian (I), Western North Pacific (WNP), and North American (NA) summer monsoon (SM) regions. The present study attempts to reveal BSISO teleconnection patterns associated with these dominant intraseasonal variability centers. During the active phase of ISM, a zonally elongated band of enhanced convection extends from India via the Bay of Bengal and Philippine Sea to tropical central Pacific with suppressed convection over the eastern Pacific near Mexico. The corresponding extratropical circulation anomalies occur along the waveguides generated by the North African-Asian jet and North Atlantic-North European jet. When the tropical convection strengthens over the WNPSM sector, a distinct great circle-like Rossby wave train emanates from the WNP to the western coast of United States (US) with an eastward shift of enhanced meridional circulation. In the active phase of NASM, large anticyclonic anomalies anchor over the western coast of US and eastern Canada and the global teleconnection pattern is similar to that during a break phase of the ISM. Examination of the evolution of the BSISO teleconnection reveals quasi-stationary patterns with preferred centers of teleconnection located at Europe, Russia, central Asia, East Asia, western US, and eastern US and Canada, respectively. Most centers are embedded in the waveguide along the westerly jet stream, but the centers at Europe and Russia occur to the north of the jet-induced waveguide. Eastward propagation of the ISO teleconnection is evident over the Pacific-North America sector. The rainfall anomalies over the elongated band near the monsoon domain over the Indo-western Pacific sector have an opposite tendency with that over the central and southern China, Mexico and southern US, providing a source of intraseasonal predictability to extratropical regions. The BSISO teleconnection along and to the north of the subtropical jet

  1. Daily atmospheric variability in the South American monsoon system

    Energy Technology Data Exchange (ETDEWEB)

    Krishnamurthy, V. [Institute of Global Environment and Society (IGES), Center for Ocean-Land-Atmosphere Studies (COLA), Calverton, MD (United States); George Mason University, Department of Atmospheric, Oceanic and Earth Sciences, Fairfax, VA (United States); Misra, Vasubandhu [Florida State University, Department of Meteorology and Center for Ocean-Atmospheric Prediction Studies, Tallahassee, FL (United States)

    2011-08-15

    The space-time structure of the daily atmospheric variability in the South American monsoon system has been studied using multichannel singular spectrum analysis of daily outgoing longwave radiation. The three leading eigenmodes are found to have low-frequency variability while four other modes form higher frequency oscillations. The first mode has the same time variability as that of El Nino-Southern Oscillation (ENSO) and exhibits strong correlation with the Pacific sea surface temperature (SST). The second mode varies on a decadal time scale with significant correlation with the Atlantic SST suggesting an association with the Atlantic multidecadal oscillation (AMO). The third mode also has decadal variability but shows an association with the SST of the Pacific decadal oscillation (PDO). The fourth and fifth modes describe an oscillation that has a period of about 165 days and is associated with the North Atlantic oscillation (NAO). The sixth and seventh modes describe an intraseasonal oscillation with a period of 52 days which shows strong relation with the Madden-Julian oscillation. There exists an important difference in the variability of convection between Amazon River Basin (ARB) and central-east South America (CESA). Both regions have similar variations due to ENSO though with higher magnitude in ARB. The AMO-related mode has almost identical variations in the two regions, whereas the PDO-related mode has opposite variations. The interseasonal NAO-related mode also has variations of opposite sign with comparable magnitudes in the two regions. The intraseasonal variability over the CESA is robust while it is very weak over the ARB region. The relative contributions from the low-frequency modes mainly determine the interannual variability of the seasonal mean monsoon although the interseasonal oscillation may contribute in a subtle way during certain years. The intraseasonal variability does not seem to influence the interannual variability in either region

  2. A limited area model (LAM) intercomparison study of a TWP-ICE active monsoon mesoscale convective event

    Science.gov (United States)

    Zhu, Ping; Dudhia, Jim; Field, Paul R.; Wapler, Kathrin; Fridlind, Ann; Varble, Adam; Zipser, Ed; Petch, Jon; Chen, Ming; Zhu, Zhenduo

    2012-06-01

    A limited area model (LAM) intercomparison study is conducted based on a tropical monsoonal deep convection case observed during the Tropical Warm Pool - International Cloud Experiment (TWP-ICE). The LAM simulations are compared with the variational analyses (VA) based on the Atmospheric Radiation Measurement (ARM) observations and the cloud resolving model (CRM) simulations forced by the VA. Driven by the ECMWF analyses or global model forecasts, LAMs are able to produce the large-scale thermodynamic field reasonably well compared with the VA. However, the LAM simulated dynamic fields, such as the large-scale horizontal divergence, vertical velocity, and cyclogenesis in the monsoonal trough, have a large inter-model spread and deviate substantially from observations. Despite the differences in large-scale forcing, there is certain consistency between the CRM and LAM simulations: stratiform (w ≤ 1 m s-1) ice clouds dominate the cloud fraction and convective (w > 3 m s-1) clouds occupy less than 3 percent of the total cloudy area. But the hydrometeor content of stratiform ice clouds is only one tenth of that of convective and transitional (1 m s-1 < w ≤ 3 m s-1) ice clouds. However, there is a large inter-LAM spread in the simulated cloud fraction and hydrometeor mixing ratios. The inter-LAM difference in solid phase hydrometeors (cloud ice, snow, and graupel) can be up to nearly a factor of 10. Among all the hydrometeor types, the stratiform ice clouds are simulated least consistently by the LAMs. The large inter-LAM spread suggests that obtaining consistent and reliable dynamic and cloud fields remains a challenge for the LAM approach.

  3. Coherent tropical-subtropical Holocene see-saw moisture patterns in the Eastern Hemisphere monsoon systems

    Science.gov (United States)

    Wang, Yongbo; Bekeschus, Benjamin; Handorf, Dörthe; Liu, Xingqi; Dallmeyer, Anne; Herzschuh, Ulrike

    2017-08-01

    The concept of a Global Monsoon (GM) has been proposed based on modern precipitation observations, but its application over a wide range of temporal scales is still under debate. Here, we present a synthesis of 268 continental paleo-moisture records collected from monsoonal systems in the Eastern Hemisphere, including the East Asian Monsoon (EAsM), the Indian Monsoon (IM), the East African Monsoon (EAfM), and the Australian Monsoon (AuM) covering the last 18,000 years. The overall pattern of late Glacial to Holocene moisture change is consistent with those inferred from ice cores and marine records. With respect to the last 10,000 years (10 ka), i.e. a period that has high spatial coverage, a Fuzzy c-Means clustering analysis of the moisture index records together with ;Xie-Beni; index reveals four clusters of our data set. The paleoclimatic meaning of each cluster is interpreted considering the temporal evolution and spatial distribution patterns. The major trend in the tropical AuM, EAfM, and IM regions is a gradual decrease in moisture conditions since the early Holocene. Moisture changes in the EAsM regions show maximum index values between 8 and 6 ka. However, records located in nearby subtropical areas, i.e. in regions not influenced by the intertropical convergence zone, show an opposite trend compared to the tropical monsoon regions (AuM, EAfM and IM), i.e. a gradual increase. Analyses of modern meteorological data reveal the same spatial patterns as in the paleoclimate records such that, in times of overall monsoon strengthening, lower precipitation rates are observed in the nearby subtropical areas. We explain this pattern as the effect of a strong monsoon circulation suppressing air uplift in nearby subtropical areas, and hence hindering precipitation. By analogy to the modern system, this would mean that during the early Holocene strong monsoon period, the intensified ascending airflows within the monsoon domains led to relatively weaker ascending or

  4. Forecasting of onset of southwest monsoon over Kerala coast using satellite data

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar, M.R.

    IEEE GEOSCIENCE AND REMOTE SENSING LETTERS, VOL. 1, NO. 4, OCTOBER 2004 265 Forecasting of Onset of Southwest Monsoon Over Kerala Coast Using Satellite Data M. R. Ramesh Kumar Abstract—The Global Precipitation and in situ gauge data have been used.... This is National Institute of Oceanography contribution number 3891. KUMAR: FORECASTING OF ONSET OF SOUTHWEST MONSOON OVER KERALA COAST USING SATELLITE DATA 267 REFERENCES [1] R. Ananthakrishnan and M. K. Soman, “The onset of the south west monsoon over Kerala 1901...

  5. THE EAST ASIAN SUBTROPICAL SUMMER MONSOON INDEX AND ITS RELATION WITH THE CLIMATE ANOMALIES IN CHINA

    Institute of Scientific and Technical Information of China (English)

    LIU Xuan-fei; WANG-Jing

    2007-01-01

    A new East Asian subtropical summer monsoon circulation index is defined, where the barotropic and baroclinic components of circulation are included. Results show that this index can well indicate the interannual variability of summer precipitation and temperature anomalies in China. A strong monsoon is characterized by more rainfall in the Yellow River basin and northern China, less rainfall in the Yangtze River basin, and more rainfall in south and southeast China, in association with higher temperature in most areas of China. Furthermore, comparison is made between the index proposed in this paper and other monsoon indexes in representing climate anomalies in China.

  6. Mid-Pliocene East Asian monsoon climate simulated in the PlioMIP

    OpenAIRE

    Zhang, R.; Yan, Q.; Z. S. Zhang; Jiang, D.; B. L. Otto-Bliesner; A. M. Haywood; D. J. Hill; Dolan, A. M.; Stepanek, C.; Lohmann, G.; Contoux, C.; F. Bragg; Chan, W.-L.; Chandler, M. A.; A. Jost

    2013-01-01

    Based on the simulations with fifteen climate models in the Pliocene Model Intercomparison Project (PlioMIP), the regional climate of East Asia (focusing on China) during the mid-Pliocene is investigated in this study. Compared to the pre-industrial, the multi-model ensemble mean (MMM) of all models shows the East Asian summer wind (EASW) largely strengthens in monsoon China, and the East Asian winter wind (EAWW) strengthens in south monsoon China but slightly weakens in north monsoon China i...

  7. A Study of the Teleconnections in the Asian-Pacific Monsoon Region

    Institute of Scientific and Technical Information of China (English)

    DING Yihui; LIU Yunyun

    2008-01-01

    The interactions among the Asian-Pacific monsoon subsystems have significant impacts on the climatic regimes in the monsoon region and even the whole world. Based on the domestic and foreign related research, an analysis is made of four different teleconnection modes found in the Asian-Pacific monsoon region, which reveal clearly the interactions among the Indian summer monsoon (ISM), the East Asian summer monsoon (EASM), and the western North Pacific summer monsoon (WNPSM). The results show that: (1) In the period of the Asian monsoon onset, the date of ISM onset is two weeks earlier than the beginning of the Meiyu over the Yangtze River Basin, and a teleconnection mode is set up from the southwestern India via the Bay of Bengal (BOB) to the Yangtze River Basin and southern Japan, I.e., the "southern" teleconnection of the Asian summer monsoon. (2) In the Asian monsoon culmination period, the precipitation of the Yangtze River Basin is influenced significantly by the WNPSM through their teleconnection relationship, and is negatively related to the WNPSM rainfall, that is, when the WNPSM is weaker than normal, the precipitation of the Yangtze River Basin is too.re than normal. (3) In contrast to the rainfall over the Yangtze River Basin, the precipitation of northern China (from the 4th pentad of July to the 3rd pentad of August) is positively related to the WNPSM. When the WNPSM is stronger than normal, the position of the western Pacific subtropical high (WPSH) becomes farther northeast than normal, the anomalous northeastward water vapor transport along the southwestern flank of WPSH is converged over northern China, providing adequate moisture for more rainfalls than normal there. (4) The summer rainfall in northern China has also a positive correlation with the ISM. During the peak period of ISM, a teleconnection pattern is formed from Northwest India via the Tibetan Plateau to northern China, I.e., the "northern" teleconnection of the Asian summer monsoon

  8. Enhancement and depletion of lower/middle tropospheric ozone in Senegal during pre-monsoon and monsoon periods of summer 2008: observations and model results

    Directory of Open Access Journals (Sweden)

    G. S. Jenkins

    2011-10-01

    Full Text Available During the summer (8 June through 3 September of 2008, 9 ozonesondes are launched from Dakar, Senegal (14.75° N, 17.49° W to investigate ozone (O3 variability in the lower/middle troposphere during the pre-monsoon and monsoon periods. Results during June 2008 (pre-monsoon period show a reduction in O3 concentrations, especially in the 850–700 hPa layer with Saharan Air Layer (SAL events. However, O3 concentrations are increased in the 950–900 hPa layer where the peak of the inversion is found and presumably the highest dust concentrations. We also use the WRF-CHEM model to gain greater insights for observations of elevated/reduced O3 concentrations during the pre-monsoon/monsoon periods. In the transition period between 26 June and 2 July in the lower troposphere (925–600 hPa, a significant increase in O3 concentrations occur which we suggest is caused by enhanced biogenic NOx emissions from Sahelian soils following rain events on 28 June and 1 July. During July and August 2008 (monsoon period, with the exception of one SAL outbreak, vertical profiles of O3 are well mixed with concentrations not exceeding 55 ppb between the surface and 550 hPa. The results suggest that during the pre-monsoon period ozone concentrations in the lower troposphere are controlled by the SAL, which destroys ozone through heterogeneous processes. At the base of the SAL we also find elevated levels of ozone, which we attribute to biogenic sources of NOx from Saharan dust that are released in the presence of moist conditions. Once the monsoon period commences, wet and dry deposition become important sinks of ozone in the Sahel with episodes of ozone poor air that is horizontally transported from low latitudes into the Sahel. These results support aircraft chemical measurements and chemical modeling results from the African Monsoon Multidisciplinary Analysis (AMMA field

  9. GENERAL SITUATION ABOUT ACTIVITY OF SUMMER MONSOON OVER SOUTH CHINA SEA IN 2004 ASIAN SUMMER MONSOON INDEX

    Institute of Scientific and Technical Information of China (English)

    LI Chun-hui; LIANG Jian-yin

    2006-01-01

    Based on daily NCEP reanalysis data, OLR and satellite rainfall data, the characteristic of the activities of South China Sea summer monsoon(SCSSM) in 2004 were analyzed. The results showed that the establishment of SCSSM was little later than normal and the intensity was stronger than normal. Influenced by the location of the northwest Pacific subtropical high, which was much northward and westward than normal,SCSSM was active mainly in the South China Sea areas. There existed obvious intraseasonal oscillation and two significant periods of SCSSM, one was about 20-30 days and the other about 40-50 days. The transportation of moisture was concentrated on the South China Sea and the northwest Pacific regions, reducing the northward transportation and resulting in drought in southern China.

  10. Prediction and Monitoring of Monsoon Intraseasonal Oscillations over Indian Monsoon Region in an Ensemble Prediction System using CFSv2

    Science.gov (United States)

    Borah, Nabanita; Sukumarpillai, Abhilash; Sahai, Atul Kumar; Chattopadhyay, Rajib; Joseph, Susmitha; De, Soumyendu; Nath Goswami, Bhupendra; Kumar, Arun

    2014-05-01

    An ensemble prediction system (EPS) is devised for the extended range prediction (ERP) of monsoon intraseasonal oscillations (MISO) of Indian summer monsoon (ISM) using NCEP Climate Forecast System model version2 at T126 horizontal resolution. The EPS is formulated by producing 11 member ensembles through the perturbation of atmospheric initial conditions. The hindcast experiments were conducted at every 5-day interval for 45 days lead time starting from 16th May to 28th September during 2001-2012. The general simulation of ISM characteristics and the ERP skill of the proposed EPS at pentad mean scale are evaluated in the present study. Though the EPS underestimates both the mean and variability of ISM rainfall, it simulates the northward propagation of MISO reasonably well. It is found that the signal-to-noise ratio becomes unity by about18 days and the predictability error saturates by about 25 days. Though useful deterministic forecasts could be generated up to 2nd pentad lead, significant correlations are observed even up to 4th pentad lead. The skill in predicting large-scale MISO, which is assessed by comparing the predicted and observed MISO indices, is found to be ~17 days. It is noted that the prediction skill of actual rainfall is closely related to the prediction of amplitude of large scale MISO as well as the initial conditions related to the different phases of MISO. Categorical prediction skills reveals that break is more skillfully predicted, followed by active and then normal. The categorical probability skill scores suggest that useful probabilistic forecasts could be generated even up to 4th pentad lead.

  11. Observed variability of sea surface salinity and thermal inversions in the Lakshadweep Sea during contrast monsoons

    Digital Repository Service at National Institute of Oceanography (India)

    Gopalakrishna, V.V.; Johnson, Z.; Salgaonkar, G.; Nisha, K.; Rajan, C.K.; Rao, R.R.

    The sea surface salinity (SSS) of the Lakshadweep Sea (LS) shows large seasonal variability due to horizontal advection of low (high) salinity waters from south (north) during winter (summer) monsoon. The measurements made in the LS during...

  12. Monsoon oscillations of the Findlater Jet and coastal winds of India

    Digital Repository Service at National Institute of Oceanography (India)

    Pankajakshan, T.; Zhao, C.; Muraleedharan, P.M.; Rao, G.S.P.; Sugimori, Y.

    Intraseasonal variability (ISV) of the Low Level Jet (LLJ) and its effects on coastal winds during the Indian summer monsoon are examined using National Centre for Environmental Prediction / National Centre for Atmospheric Research (NCEP) reanalyses...

  13. Driving forces of Indian summer monsoon on Milankovitch and sub-Milankovitch time scales: A review

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.

    and deep water circulation changes drive the variability of southwest (SW) monsoon in the Indian subcontinent. Different forcing factors act on different time scales. Arabian Sea sediments consist of distinct fauna that are endemic to areas of upwelling...

  14. Influence of eastern Arabian Sea on summer monsoon rainfall over west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    RameshBabu, V.; Rao, M.S.; Rao, M.V.

    anomaly field in the eastern Arabian Sea where larger atmospheric convection as compared to that over other parts of the water body normally takes place during the summer monsoon season. The present results based on observations during ten years' period...

  15. Impact of convection over the equatorial trough on the summer monsoon activity over India

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar, M.R.; Shenoi, S.S.C.; Schulz, J.

    Project (GPCP). Most (about 73%) of the break in monsoon (BM) events were associated with the convective activity (rainfall more than 30 mm/pentad) over the equatorial trough (ET) region. The association between these events and the convective activity...

  16. Improving Energy-Based Estimates of Monsoon Location in the Presence of Proximal Deserts

    CERN Document Server

    Shekhar, Ravi

    2016-01-01

    Two theoretical frameworks have been widely used to understand the response of monsoons to local and remote forcings: the vertically integrated atmospheric energy budget and convective quasi-equilibrium (CQE). Existing forms of these frameworks neglect some of the complexities of monsoons, such as the shallow meridional circulations that advect dry air from adjacent deserts into the middle and lower troposphere of monsoon regions. Here the fidelity of energy budget and CQE theories for monsoon location is assessed in a three-dimensional beta-plane model with boundary conditions representative of an off-equatorial continent with a tropical grassland and an adjacent subtropical desert. Energy budget theories show mixed success for various SST and land surface albedo forcings, with the ITCZ being collocated with the energy flux equator but a non-monotonic relationship existing between ITCZ latitude and cross-equatorial energy transport. Accounting for the off-equatorial position of the unperturbed energy flux eq...

  17. Attenuation of surface waves due to monsoon rains: A model study for the north Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Vethamony, P.; Kumar, B.P.; Sarma, Y.V.B.

    The dynamic interaction of intense rain with waves based on momentum exchange is applied to a second generation wave model to predict wave attenuation during monsoon. The scheme takes into account the characteristics of rain and wave parameters...

  18. The Onset of the Monsoon over the Bay of Bengal: The Year-to-Year Variations

    Institute of Scientific and Technical Information of China (English)

    YU Wei-Dong; LI Kui-Ping; SHI Jian-Wei; LIU Lin; WANG Hui-Wu; LIU Yan-Liang

    2012-01-01

    In situ buoy observation data spanning four years (2008-2011) were used to demonstrate the year-to-year variations of the monsoon onset processes in the Bay of Bengal (BOB). A significant early (late) monsoon onset event in 2009 (2010) was analyzed in detail. It is found that the year-to-year variations of monsoon onset can be attributed to either the interannual variability in the BoB SST or the irregular activities of the intra-seasonal oscillation (ISO). This finding raises concern over the potential difficulties in simulating or predicting the monsoon onset in the BoB region. This uncertainty largely comes from the unsatisfactory model behavior at the intra-seasonal time scale.

  19. Eurasian Snow Conditions and Summer Monsoon Rainfall over South and Southeast Asia:Assessment and Comparison

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    This study reveals the complex nature of the connection between Eurasian snow and the following summer season's monsoon rainfall by using four different indicators of snow conditions and correlating each of them to summer monsoon rainfall. Using 46 years of historical records of mean winter snow depth,maximum snow depth, and snow starting dates, and 27 years of snow area coverage from remote sensing observations over Eurasia, the authors found diverse correlation patterns between snow conditions and the following warm season's rainfall over South and Southeast Asia. Some of the results contradict the well-known inverse relationships between snow and the summer monsoon. This study provides an easy comparison of results in that it shows the connections between Eurasian snow and monsoon rainfall by using different Eurasian snow indicators based on the best available historical records without discrimination of regional variations in snow conditions.

  20. Vertical distribution of mesozooplankton in the central and eastern Arabian Sea during the winter monsoons

    Digital Repository Service at National Institute of Oceanography (India)

    Padmavati, G.; Haridas, P.; Nair, K.K.C.; Gopalakrishnan, T.C.; Shiney, P.; Madhupratap, M.

    The vertical distribution of mesozooplankton in the central and eastern Arabian Sea was investigated during the winter monsoon in 1995. Samples were analysed from discrete depth zones defined according to oxygen and temperature profiles of the water...

  1. Relationships between Indian summer monsoon rainfall and ice cover over selected oceanic regions

    Digital Repository Service at National Institute of Oceanography (India)

    Gopinathan, C.K.

    The variations in oceanic ice cover at selected polar regions during 1973 to 1987 have been analysed in relation to the seasonal Indian summer monsoon rainfall. The ice cover over the Arctic regions in June has negative relationship (correlation...

  2. Global association of the Madden-Julian Oscillation with monsoon lows and depressions

    Science.gov (United States)

    Haertel, Patrick; Boos, William R.

    2017-08-01

    Previous research has revealed that monsoon lows and depressions are modulated on intraseasonal time scales in a few regions, including India, Australia, and the East Pacific. This study examines whether such modulation occurs on a global scale and, in particular, how the Madden-Julian Oscillation (MJO) is associated with changes in synoptic-scale vortices across all monsoon regions. The spatial climatology of monsoon disturbances is largely insensitive to MJO amplitude. However, monsoon disturbance frequency (MDF) varies substantially with MJO phase, with regional perturbations of 25 to 90% of the seasonal mean value across the tropics. In off-equatorial locations, MDF maxima occur in locations where the MJO enhances low level cyclonic vorticity, typically near the western edge of midlevel moisture perturbations. In contrast, equatorial MDF perturbations are in phase with MJO moisture and rainfall anomalies, with maxima in regions with strong low level zonal wind convergence.

  3. A High-Resolution Absolute-Dated Late Pleistocene Monsoon Record from Hulu Cave, China

    National Research Council Canada - National Science Library

    Y. J. Wang; H. Cheng; R. L. Edwards; Z. S. An; J. Y. Wu; C.-C. Shen; J. A. Dorale

    2001-01-01

    Oxygen isotope records of five stalagmites from Hulu Cave near Nanjing bear a remarkable resemblance to oxygen isotope records from Greenland ice cores, suggesting that East Asian Monsoon intensity...

  4. Culturable heterotrophic bacteria from the euphotic zone of the Indian Ocean ocean during the summer monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Nair, S.; LokaBharathi, P.A.; Chandramohan, D.

    Cuturable heterotrophic bacterial counts (viable counts: VC) by surface plating on ZoBell medium and total bacterial counts (TC) by epifuorenscence microscopy were carried out in sea water off the southwest coast of India during the monsoon. TC were...

  5. AN EAST ASIAN SUBTROPICAL SUMMER MONSOON INDEX DEFINED BY MOISTURE TRANSPORT

    Institute of Scientific and Technical Information of China (English)

    LIANG Ping; TANG Xu; HE Jin-hai; CHEN Long-xun

    2008-01-01

    Using daily NCEP/NCAR reanalysis dataset and observation rainfall data in China for the 1971- 2000 period, a subtropical summer monsoon index has been defined by meridional moisture transport of the total atmosphere column. Results show that the subtropical summer monsoon index defined by the difference of meridional moisture transport between South China and North China can be used to describe the intensity of the subtropical summer monsoon. High (low) index is corresponding to strong (weak) subtropical summer monsoon. And the new index is well related to the summer rainfall over the middle and lower reaches of Yangtze River. In addition, the convergence of moisture transport from the west Pacific via the South China Sea and that from the North China may be responsible for the anomalously excessive summer rainfall over the middle and lower reaches of Yangtze River.

  6. Variations in phytoplankton community in a monsoon-influenced tropical estuary

    Digital Repository Service at National Institute of Oceanography (India)

    Patil, J.S.; Anil, A.C.

    . The break period in monsoon altered the phytoplankton community leading to mixed species bloom of large-sized diatoms and harmful dinoflagellates (Gymnodinium catenatum and Cochlodinium polykrikoides) under high-saline, nutrient-poor, non...

  7. Impact of monsoon rainfall on the total food grain yield over India

    Indian Academy of Sciences (India)

    V Prasanna

    2014-07-01

    The study focuses on understanding the variations of precipitation during summer monsoon season and its impact on Kharif and Rabi foodgrain yield over India. Total foodgrain yield over India during Kharif (summer) season is directly affected by variations in the summer monsoon precipitation (June–September). An increase (decrease) in rainfall is generally associated with an increase (decrease) in foodgrain yield. A similar correspondence during the Rabi (winter) foodgrain yield is not evident. The Rabi crop is not directly affected by variations in the post-monsoon precipitation (October–December) alone, also the summer season precipitation influences the Rabi crop through water and soil moisture availability over many parts of India. Though the reduction of rainfall activity during the entire summer monsoon season leads to reduction in crop yields, the occurrence of prolonged rainfall breaks also causes adverse effect on the crop growth resulting in reduced crop yields.

  8. Elucidation of the tidal influence on bacterial populations in a monsoon influenced estuary through simultaneous observations

    Digital Repository Service at National Institute of Oceanography (India)

    Khandeparker, L.; Eswaran, R.; Gardade, L.; Kuchi, N.; Mapari, K.E.; Naik, S.D.; Anil, A.C.

    The influence of tides on bacterial populations in a monsoon influenced tropical estuary was assessed through fine resolution sampling (1 to 3 h) during spring and neap tides from mouth to the freshwater end at four stations during pre...

  9. Environmental changes associated with monsoon induced upwelling, off central west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    DeSousa, S.N.; Sawkar, K.; Rao, P.V.S.S.D.P.

    Coastal upwelling of nutrients during and after the southwest monsoon has been considered to support rich pelagic and demersal fisheries off the west coast of India. Studies indicate occurrence of coastal upwelling assoicated with Ekman transport...

  10. Characteristics of coastal waters of the western Bay of Bengal during different monsoon seasons

    Digital Repository Service at National Institute of Oceanography (India)

    Suryanarayana, A.; Murty, C.S.; Rao, D.P.

    Physical characteristics of waters along the eastern coast of India up to offshore distances of 400 km have been investigated during the seasons of the north-easterly and south-westerly monsoons in light of relevant observed meteorological forcings...

  11. Temporal variation of diatom benthic propagules in a monsoon-influenced tropical estuary

    Digital Repository Service at National Institute of Oceanography (India)

    Patil, J.S.; Anil, A

    Temporal variations in the diatom benthic propagule (DBP) community and their role in the phytoplankton community in a monsoon-affected tropical estuary, Zuari estuary, Goa (India) are presented. The DBP from the sediments was enumerated using...

  12. Natural and anthropogenic impacts on the Asian monsoon precipitation during the 20th century

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The increase in the global average temperature during the last century is considered an integrated result of anthropogenic and natural forcing, but different views remain about the anthropogenic impacts on the Asian monsoon precipitation. Based on the ~2000-year records of stalagmite δ18O from the Dongge Cave (Guizhou Province) and Wanxiang Cave (Gansu Province), we address the possible anthropogenic impacts on the southwest and southeast Asian monsoon from 1900-2000 AD, using the method of Singular Spectrum Analysis (SSA). The results show that the monsoon precipitation trends in the last 100 years at both sites can be obtained through SSA prediction using the data prior to 1900 AD. These suggest that human activity has not significantly affected the trends of monsoon precipitation despite of its impact on the global temperature.

  13. Cyclone trends constrain monsoon variability during Late Oligocene sea level highstands (Kachchh Basin, NW India

    Directory of Open Access Journals (Sweden)

    M. Reuter

    2013-01-01

    Full Text Available Important concerns about the consequences of climate change for India are the potential impact on tropical cyclones and the monsoon. Herein we present a sequence of fossil shell beds from the shallow-marine Maniyara Fort Formation (Kachcch Basin as an indicator of tropical cyclone activity along the NW Indian coast during the Late Oligocene warming period (~27–24 Ma. Direct proxies providing information about the atmospheric circulation dynamics over the Indian subcontinent at this time are important since it corresponds to a major climate reorganization in Asia that ends up with the establishment of the modern Asian monsoon system in the Early Miocene. The vast shell concentrations comprise a mixture of parautochthonous and allochthonous assemblages indicating storm-generated sediment transport from deep to shallow water during third-order sea level highstands. Three distinct skeletal assemblages were distinguished each recording a relative storm wave base depth. (1 A shallow storm wave base is shown by nearshore mollusks, corals and Clypeaster echinoids; (2 an intermediate storm wave base depth is indicated by lepidocyclind foraminifers, Eupatagus echinoids and corallinaceans; and (3 a deep storm wave base is represented by an Amussiopecten–Schizaster echinoid assemblage. Vertical changes in these skeletal associations give evidence of gradually increasing tropical cyclone intensity in line with third-order sea level rise. The intensity of cyclones over the Arabian Sea is primarily linked to the strength of the Indian monsoon. Therefore and since the topographic boundary conditions for the Indian monsoon already existed in the Late Oligocene, the longer-term cyclone trends were interpreted to reflect monsoon variability during the initiation of the Asian monsoon system. Our results imply an active monsoon over the Eastern Tethys at ~26 Ma followed by a period of monsoon weakening during the peak of the Late Oligocene

  14. Cyclone trends constrain monsoon variability during late Oligocene sea level highstands (Kachchh Basin, NW India)

    Science.gov (United States)

    Reuter, M.; Piller, W. E.; Harzhauser, M.; Kroh, A.

    2013-09-01

    Climate change has an unknown impact on tropical cyclones and the Asian monsoon. Herein we present a sequence of fossil shell beds from the shallow-marine Maniyara Fort Formation (Kachcch Basin) as a recorder of tropical cyclone activity along the NW Indian coast during the late Oligocene warming period (~ 27-24 Ma). Proxy data providing information about the atmospheric circulation dynamics over the Indian subcontinent at this time are important since it corresponds to a major climate reorganization in Asia that ends up with the establishment of the modern Asian monsoon system at the Oligocene-Miocene boundary. The vast shell concentrations are comprised of a mixture of parautochthonous and allochthonous assemblages indicating storm-generated sediment transport from deeper to shallow water during third-order sea level highstands. Three distinct skeletal assemblages were distinguished, each recording a relative storm wave base. (1) A shallow storm wave base is shown by nearshore molluscs, reef corals and Clypeaster echinoids; (2) an intermediate storm wave base depth is indicated by lepidocyclinid foraminifers, Eupatagus echinoids and corallinacean algae; and (3) a deep storm wave base is represented by an Amussiopecten bivalve-Schizaster echinoid assemblage. These wave base depth estimates were used for the reconstruction of long-term tropical storm intensity during the late Oligocene. The development and intensification of cyclones over the recent Arabian Sea is primarily limited by the atmospheric monsoon circulation and strength of the associated vertical wind shear. Therefore, since the topographic boundary conditions for the Indian monsoon already existed in the late Oligocene, the reconstructed long-term cyclone trends were interpreted to reflect monsoon variability during the initiation of the Asian monsoon system. Our results imply an active monsoon over the Eastern Tethys at ~ 26 Ma followed by a period of monsoon weakening during the peak of the late

  15. Simulation of Asian Monsoon Seasonal Variations with Climate Model R42L9/LASG

    Institute of Scientific and Technical Information of China (English)

    王在志; 吴国雄; 吴统文; 宇如聪

    2004-01-01

    The seasonal variations of the Asian monsoon were explored by applying the atmospheric general circulation model R42L9 that was developed recently at the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences (LASG/IAP/CAS). The 20-yr (1979-1998) simulation was done using the prescribed20-yr monthly SST and sea-ice data as required by Atmospheric Model Intercomparison Project (AMIP)Ⅱ in the model. The monthly precipitation and monsoon circulations were analyzed and compared with the observations to validate the model's performance in simulating the climatological mean and seasonal variations of the Asian monsoon. The results show that the model can capture the main features of the spatial distribution and the temporal evolution of precipitation in the Indian and East Asian monsoon areas. The model also reproduced the basic patterns of monsoon circulation. However, some biases exist in this model. The simulation of the heating over the Tibetan Plateau in summer was too strong. The overestimated heating caused a stronger East Asian monsoon and a weaker Indian monsoon than the observations. In the circulation fields, the South Asia high was stronger and located over the Tibetan Plateau. The western Pacific subtropical high was extended westward, which is in accordance with the observational results when the heating over the Tibetan Plateau is stronger. Consequently, the simulated rainfall around this area and in northwest China was heavier than in observations, but in the Indian monsoon area and west Pacific the rainfall was somewhat deficient.

  16. Cyclone trends constrain monsoon variability during late Oligocene sea level highstands (Kachchh Basin, NW India

    Directory of Open Access Journals (Sweden)

    M. Reuter

    2013-09-01

    Full Text Available Climate change has an unknown impact on tropical cyclones and the Asian monsoon. Herein we present a sequence of fossil shell beds from the shallow-marine Maniyara Fort Formation (Kachcch Basin as a recorder of tropical cyclone activity along the NW Indian coast during the late Oligocene warming period (~ 27–24 Ma. Proxy data providing information about the atmospheric circulation dynamics over the Indian subcontinent at this time are important since it corresponds to a major climate reorganization in Asia that ends up with the establishment of the modern Asian monsoon system at the Oligocene–Miocene boundary. The vast shell concentrations are comprised of a mixture of parautochthonous and allochthonous assemblages indicating storm-generated sediment transport from deeper to shallow water during third-order sea level highstands. Three distinct skeletal assemblages were distinguished, each recording a relative storm wave base. (1 A shallow storm wave base is shown by nearshore molluscs, reef corals and Clypeaster echinoids; (2 an intermediate storm wave base depth is indicated by lepidocyclinid foraminifers, Eupatagus echinoids and corallinacean algae; and (3 a deep storm wave base is represented by an Amussiopecten bivalve-Schizaster echinoid assemblage. These wave base depth estimates were used for the reconstruction of long-term tropical storm intensity during the late Oligocene. The development and intensification of cyclones over the recent Arabian Sea is primarily limited by the atmospheric monsoon circulation and strength of the associated vertical wind shear. Therefore, since the topographic boundary conditions for the Indian monsoon already existed in the late Oligocene, the reconstructed long-term cyclone trends were interpreted to reflect monsoon variability during the initiation of the Asian monsoon system. Our results imply an active monsoon over the Eastern Tethys at ~ 26 Ma followed by a period of monsoon weakening during the

  17. Seasonally asymmetric transition of the Asian monsoon in response to ice age boundary conditions

    Energy Technology Data Exchange (ETDEWEB)

    Ueda, Hiroaki; Kuroki, Harumitsu; Kamae, Youichi [University of Tsukuba, Graduate School of Life and Environmental Sciences, Tsukuba, Ibaraki (Japan); Ohba, Masamichi [Central Research Institute of Electric Power Industry, Environmental Science Research Laboratory, Abiko (Japan)

    2011-12-15

    Modulation of a monsoon under glacial forcing is examined using an atmosphere-ocean coupled general circulation model (AOGCM) following the specifications established by Paleoclimate Modelling Intercomparison Project phase 2 (PMIP2) to understand the air-sea-land interaction under different climate forcing. Several sensitivity experiments are performed in response to individual changes in the continental ice sheet, orbital parameters, and sea surface temperature (SST) in the Last Glacial Maximum (LGM: 21 ka) to evaluate the driving mechanisms for the anomalous seasonal evolution of the monsoon. Comparison of the model results in the LGM with the pre-industrial (PI) simulation shows that the Arabian Sea and Bay of Bengal are characterized by enhancement of pre-monsoon convection despite a drop in the SST encompassing the globe, while the rainfall is considerably suppressed in the subsequent monsoon period. In the LGM winter relative to the PI, anomalies in the meridional temperature gradient (MTG) between the Asian continents minus the tropical oceans become positive and are consistent with the intensified pre-monsoon circulation. The enhanced MTG anomalies can be explained by a decrease in the condensation heating relevant to the suppressed tropical convection as well as positive insolation anomalies in the higher latitude, showing an opposing view to a warmer future climate. It is also evident that a latitudinal gradient in the SST across the equator plays an important role in the enhancement of pre-monsoon rainfall. As for the summer, the sensitivity experiments imply that two ice sheets over the northern hemisphere cools the air temperature over the Asian continent, which is consistent with the reduction of MTG involved in the attenuated monsoon. The surplus pre-monsoon convection causes a decrease in the SST through increased heat loss from the ocean surface; in other words, negative ocean feedback is also responsible for the subsequent weakening of summer

  18. Effect of precession on the Asian summer monsoon evolution: A systematic review

    Institute of Scientific and Technical Information of China (English)

    LIU XiaoDong; SHI ZhengGuo

    2009-01-01

    Geological climatic records and model simulations on the Asian summer monsoon climate change induced by insolation forcing of the Earth's precession are systematically reviewed in this paper. The presentation of the questions on the mechanism of the Asian monsoon evolution at the precession band, currently existing debates and future research directions are discussed. Since the early 1980s, more and more observed evidence and simulated results, especially the absolute-dated stalagmite re-cords and orbital-scale transient model runs in the last few years, have indicated that the quasi-20ka period in the Quaternary monsoon climate change is caused by precession. However, debates still exist on the dynamic mechanism how precession affects the Asian monsoon. The "zero phase" hypothesis says that the Asian monsoon is merely controlled by summer insolation in the Northern Hemisphere (NH) while the "latent heat" hypothesis emphasizes the dominant effect of latent heat transport from the Southern Hemisphere (SH) besides the role of the northern insolation. The two hypotheses have separately been supported by some evidence. Although we are cognizant of the importance of northern solar radiation and the remote effect of southern insolation, it has still a long way to go before com-prehensively understanding the evolutionary mechanism of the Asian monsoon. In view of the prob-lems existing in present researches of monsoon-dominated climate change at the precession scale, we propose that studies on the environmental significance of geological monsoon proxies, feedback processes in the long-term transient simulations and intercomparisons between observations and modeling results should be strengthened in the future.

  19. GMMIP (v1.0) contribution to CMIP6: Global Monsoons Model Inter-comparison Project

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Tianjun; Turner, Andrew G.; Kinter, James L.; Wang, Bin; Qian, Yun; Chen, Xiaolong; Wu, Bo; Wang, Bin; Liu, Bo; Zou, Liwei; He, Bian

    2016-10-10

    The Global Monsoons Model Inter-comparison Project (GMMIP) has been endorsed by the panel of Coupled Model Inter-comparison Project (CMIP) as one of the participating model inter-comparison projects (MIPs) in the sixth phase of CMIP (CMIP6). The focus of GMMIP is on monsoon climatology, variability, prediction and projection, which is relevant to four of the “Grand Challenges” proposed by the World Climate Research Programme. At present, 21 international modeling groups are committed to joining GMMIP. This overview paper introduces the motivation behind GMMIP and the scientific questions it intends to answer. Three tiers of experiments, of decreasing priority, are designed to examine (a) model skill in simulating the climatology and interannual-to-multidecadal variability of global monsoons forced by the sea surface temperature during historical climate period; (b) the roles of the Interdecadal Pacific Oscillation and Atlantic Multidecadal Oscillation in driving variations of the global and regional monsoons; and (c) the effects of large orographic terrain on the establishment of the monsoons. The outputs of the CMIP6 Diagnostic, Evaluation and Characterization of Klima experiments (DECK), “historical” simulation and endorsed MIPs will also be used in the diagnostic analysis of GMMIP to give a comprehensive understanding of the roles played by different external forcings, potential improvements in the simulation of monsoon rainfall at high resolution and reproducibility at decadal timescales. The implementation of GMMIP will improve our understanding of the fundamental physics of changes in the global and regional monsoons over the past 140 years and ultimately benefit monsoons prediction and projection in the current century.

  20. Monsoonal response to mid-holocene orbital forcing in a high resolution GCM

    Directory of Open Access Journals (Sweden)

    J. H. C. Bosmans

    2012-04-01

    Full Text Available In this study, we use a sophisticated high-resolution atmosphere-ocean coupled climate model, EC-Earth, to investigate the effect of Mid-Holocene orbital forcing on summer monsoons on both hemispheres. During the Mid-Holocene (6 ka, there was more summer insolation on the Northern Hemisphere than today, which intensified the meridional temperature and pressure gradients. Over North Africa, monsoonal precipitation is intensified through increased landward monsoon winds and moisture advection as well as decreased moisture convergence over the oceans and more convergence over land compared to the pre-industrial simulation. Precipitation also extends further north as the ITCZ shifts northward in response to the stronger poleward gradient of insolation. This increase and poleward extent is stronger than in most previous ocean-atmosphere GCM simulations. In north-westernmost Africa, precipitation extends up to 35° N. Over tropical Africa, internal feedbacks completely overcome the direct warming effect of increased insolation. We also find a weakened African Easterly Jet. Over Asia, monsoonal precipitation during the Mid-Holocene is increased as well, but the response is different than over North-Africa. There is more convection over land at the expense of convection over the ocean, but precipitation does not extend further northward, monsoon winds over the ocean are weaker and the surrounding ocean does not provide more moisture. On the Southern Hemisphere, summer insolation and the poleward insolation gradient were weaker during the Mid-Holocene, resulting in a reduced South American monsoon through decreased monsoon winds and less convection, as well as an equatorward shift in the ITCZ. This study corroborates the findings of paleodata research as well as previous model studies, while giving a more detailed account of Mid-Holocene monsoons.

  1. History and variability of East Asian monsoon climate since the late Miocene

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    @@ The variability and dynamic mechanism of the East Asian monsoon climate is a major scientific puzzle in the exploration of global change.As early as in the late 1990s,a research team led by Prof.AN Zhisheng from the CAS Institute of Earth Environment started their work in this topic,with an objective of improving the hypothesis of monsoon-controlled East Asian environment and advancing the basic studies of past global changes in eastern Asia.

  2. GMMIP (v1.0) contribution to CMIP6: Global Monsoons Model Inter-comparison Project

    OpenAIRE

    Zhou, Tianjun; Turner, Andrew G.; Kinter, James L.; Qian, Yun; Chen, Xiaolong; Bo WU; Wang, Bin; Liu, Bo; Zou, Liwei; He, Bian

    2016-01-01

    The Global Monsoons Model Inter-comparison Project (GMMIP) has been endorsed by the panel of Coupled Model Inter-comparison Project (CMIP) as one of the participating model inter-comparison projects (MIPs) in the sixth phase of CMIP (CMIP6). The focus of GMMIP is on monsoon climatology, variability, prediction and projection, which is relevant to four of the “Grand Challenges” proposed by the World Climate Research Programme. At present, 21 international modeling groups are ...

  3. Links between Indo-Pacific climate variability and drought in the Monsoon Asia Drought Atlas

    Science.gov (United States)

    Ummenhofer, Caroline C.; D'Arrigo, Rosanne D.; Anchukaitis, Kevin J.; Buckley, Brendan M.; Cook, Edward R.

    2013-03-01

    Drought patterns across monsoon and temperate Asia over the period 1877-2005 are linked to Indo-Pacific climate variability associated with the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). Using the Monsoon Asia Drought Atlas (MADA) composed of a high-resolution network of hydroclimatically sensitive tree-ring records with a focus on the June-August months, spatial drought patterns during El Niño and IOD events are assessed as to their agreement with an instrumental drought index and consistency in the drought response amongst ENSO/IOD events. Spatial characteristics in drought patterns are related to regional climate anomalies over the Indo-Pacific basin, using reanalysis products, including changes in the Asian monsoon systems, zonal Walker circulation, moisture fluxes, and precipitation. A weakening of the monsoon circulation over the Indian subcontinent and Southeast Asia during El Niño events, along with anomalous subsidence over monsoon Asia and reduced moisture flux, is reflected in anomalous drought conditions over India, Southeast Asia and Indonesia. When an IOD event co-occurs with an El Niño, severe drought conditions identified in the MADA for Southeast Asia, Indonesia, eastern China and central Asia are associated with a weakened South Asian monsoon, reduced moisture flux over China, and anomalous divergent flow and subsidence over Indonesia. Insights into the relative influences of Pacific and Indian Ocean variability for Asian monsoon climate on interannual to decadal and longer timescales, as recorded in the MADA, provide a useful tool for assessing long-term changes in the characteristics of Asian monsoon droughts in the context of Indo-Pacific climate variability.

  4. Evaluation of CFSV2 Forecast Skill for Indian Summer Monsoon Sub-Seasonal Characteristics

    Science.gov (United States)

    S, S. A.; Ghosh, S.

    2015-12-01

    Prediction of sub seasonal monsoon characteristics of Indian Summer Monsoon (ISM) is highly crucial for agricultural planning and water resource management. The Climate forecast System version 2 (CFS V2), the state of the art coupled climate model developed by NCEP, is currently being employed for the seasonal and extended range forecasts of ISM. Even though CFSV2 is a fully coupled ocean- atmosphere- land model with advanced physics, increased resolution and refined initialisation, its ISM forecasts, in terms of seasonal mean and variability needs improvement. Numerous works have been done for verifying the CFSV2 forecasts in terms of the seasonal mean, its mean and variability, active and break spells, and El Nino Southern Oscillation (ENSO) - monsoon interactions. Most of these works are based on either rain fall strength or rainfall based indices. Here we evaluate the skill of CFS v2 model in forecasting the various sub seasonal features of ISM, viz., the onset and withdrawal days of monsoon that are determined using circulation based indices, the Monsoon Intra Seasonal Oscillations (MISO), and Indian Ocean and Pacific Ocean sea surface temperatures. The MISO index, we use here, is based on zonal wind at 850 hPa and Outgoing Long wave Radiation (OLR) anomalies. With this work, we aim at assessing the skill of the model in simulating the large scale circulation patterns and their variabilities within the monsoon season. Variabilities in these large scale circulation patterns are primarily responsible for the variabilities in the seasonal monsoon strength and its temporal distribution across the season. We find that the model can better forecast the large scale circulation and than the actual precipitation. Hence we suggest that seasonal rainfall forecasts can be improved by the statistical downscaling of CFSV2 forecasts by incorporating the established relationships between the well forecasted large scale variables and monsoon precipitation.

  5. GMMIP (v1.0) contribution to CMIP6: Global Monsoons Model Inter-comparison Project

    Science.gov (United States)

    Zhou, Tianjun; Turner, Andrew G.; Kinter, James L.; Wang, Bin; Qian, Yun; Chen, Xiaolong; Wu, Bo; Wang, Bin; Liu, Bo; Zou, Liwei; He, Bian

    2016-10-01

    The Global Monsoons Model Inter-comparison Project (GMMIP) has been endorsed by the panel of Coupled Model Inter-comparison Project (CMIP) as one of the participating model inter-comparison projects (MIPs) in the sixth phase of CMIP (CMIP6). The focus of GMMIP is on monsoon climatology, variability, prediction and projection, which is relevant to four of the "Grand Challenges" proposed by the World Climate Research Programme. At present, 21 international modeling groups are committed to joining GMMIP. This overview paper introduces the motivation behind GMMIP and the scientific questions it intends to answer. Three tiers of experiments, of decreasing priority, are designed to examine (a) model skill in simulating the climatology and interannual-to-multidecadal variability of global monsoons forced by the sea surface temperature during historical climate period; (b) the roles of the Interdecadal Pacific Oscillation and Atlantic Multidecadal Oscillation in driving variations of the global and regional monsoons; and (c) the effects of large orographic terrain on the establishment of the monsoons. The outputs of the CMIP6 Diagnostic, Evaluation and Characterization of Klima experiments (DECK), "historical" simulation and endorsed MIPs will also be used in the diagnostic analysis of GMMIP to give a comprehensive understanding of the roles played by different external forcings, potential improvements in the simulation of monsoon rainfall at high resolution and reproducibility at decadal timescales. The implementation of GMMIP will improve our understanding of the fundamental physics of changes in the global and regional monsoons over the past 140 years and ultimately benefit monsoons prediction and projection in the current century.

  6. A mechanism for land-ocean contrasts in global monsoon trends in a warming climate

    Energy Technology Data Exchange (ETDEWEB)

    Fasullo, J. [National Center for Atmospheric Research, CAS/NCAR, Boulder, CO (United States)

    2012-09-15

    A central paradox of the global monsoon record involves reported decreases in rainfall over land during an era in which the global hydrologic cycle is both expected and observed to intensify. It is within this context that this work develops a physical basis for both interpreting the observed record and anticipating changes in the monsoons in a warming climate while bolstering the concept of the global monsoon in the context of shared feedbacks. The global-land monsoon record across multiple reanalyses is first assessed. Trends that in other studies have been taken as real are shown to likely be spurious as a result of changes in the assimilated data streams both prior to and during the satellite era. Nonetheless, based on satellite estimates, robust increases in monsoon rainfall over ocean do exist and a physical basis for this land-ocean contrast remains lacking. To address the contrast's causes, simulated trends are therefore assessed. While projections of total rainfall are inconsistent across models, the robust land-ocean contrast identified in observations is confirmed. A feedback mechanism is proposed rooted in the facts that land areas warm disproportionately relative to ocean, and onshore flow is the chief source of monsoonal moisture. Reductions in lower tropospheric relative humidity over land domains are therefore inevitable and these have direct consequences for the monsoonal convective environment including an increase in the lifting condensation level and a shift in the distribution of convection generally towards less frequent and potentially more intense events. The mechanism is interpreted as an important modulating influence on the ''rich-get-richer'' mechanism. Caveats for regional monsoons exist and are discussed. (orig.)

  7. Influence of the monsoon trough on air-sea interaction in the head of the Bay of Bengal during the southwest monsoon of 1990 (monsoon trough boundary layer experiment - 90)

    Digital Repository Service at National Institute of Oceanography (India)

    Sarma, Y.V.B.; Seetaramayya, P.; Murty, V.S.N.; Rao, D.P.

    surface heat flux by 80Wm sup(-2), was associated with the development of a depression when the monsoon trough moved southwards. At the peak of the depression, values of the latent heat flux and evaporation reached up to 270 Wm sup(-2) and 1.0 cm day sup...

  8. The South American monsoon variability over the last millennium in climate models

    Science.gov (United States)

    Rojas, Maisa; Arias, Paola A.; Flores-Aqueveque, Valentina; Seth, Anji; Vuille, Mathias

    2016-08-01

    In this paper we assess South American monsoon system (SAMS) variability in the last millennium as depicted by global coupled climate model simulations. High-resolution proxy records for the South American monsoon over this period show a coherent regional picture of a weak monsoon during the Medieval Climate Anomaly and a stronger monsoon during the Little Ice Age (LIA). Due to the small external forcing during the past 1000 years, model simulations do not show very strong temperature anomalies over these two specific periods, which in turn do not translate into clear precipitation anomalies, in contrast with the rainfall reconstructions in South America. Therefore, we used an ad hoc definition of these two periods for each model simulation in order to account for model-specific signals. Thereby, several coherent large-scale atmospheric circulation anomalies are identified. The models feature a stronger monsoon during the LIA associated with (i) an enhancement of the rising motion in the SAMS domain in austral summer; (ii) a stronger monsoon-related upper-tropospheric anticyclone; (iii) activation of the South American dipole, which results in a poleward shift of the South Atlantic Convergence Zone; and (iv) a weaker upper-level subtropical jet over South America. The diagnosed changes provide important insights into the mechanisms of these climate anomalies over South America during the past millennium.

  9. Contribution of Monthly and Regional Rainfall to the Strength of Indian Summer Monsoon

    Science.gov (United States)

    Zheng, Y.; Ali, M.; Bourassa, M. A.

    2015-12-01

    Indian Summer Monsoon Rainfall (ISMR: June-September) has both temporal and spatial variability causing floods/droughts in different seasons/locations leading to a strong or weak monsoon. Here, we present the contribution of all-India monthly, seasonal and regional rainfall to the ISMR, with special reference to the strong and weak monsoons. For this purpose, rainfall data provided by the India Meteorological Department (IMD: http://www.imd.gov.in/section/nhac/dynamic/Monsoon_frame.htm) for 1901-2013 have been used. The IMD divided the Indian sub-continent into four homogeneous regions of northwest India (NWI), northeast India (NEI), central India (CI), and south peninsula India (SPIN). Rainfall during July-August contributes the most to the total seasonal rainfall, whether it is a strong or weak monsoon. Although the NEI has the maximum area-weighted rainfall, its contribution is the least toward a strong or weak monsoon. The rainfall in the remaining three regions (NWI, CI, and SPIN) controls whether an ISMR is strong or weak. Compared to the monthly rainfall, the regional rainfall dominates the strong or weak rainfall periods.

  10. Late Miocene-Pliocene Asian monsoon intensification linked to Antarctic ice-sheet growth

    Science.gov (United States)

    Ao, Hong; Roberts, Andrew P.; Dekkers, Mark J.; Liu, Xiaodong; Rohling, Eelco J.; Shi, Zhengguo; An, Zhisheng; Zhao, Xiang

    2016-06-01

    Environmental conditions in one of Earth's most densely populated regions, East Asia, are dominated by the monsoon. While Quaternary monsoon variability is reasonably well understood, pre-Quaternary monsoon variability and dynamics remain enigmatic. In particular, little is known about potential relationships between northern hemispheric monsoon response and major Cenozoic changes in Antarctic ice cover. Here we document long-term East Asian summer monsoon (EASM) intensification through the Late Miocene-Pliocene (∼8.2 to 2.6 Ma), and attribute this to progressive Antarctic glaciation. Our new high-resolution magnetic records of long-term EASM intensification come from the Late Miocene-Pliocene Red Clay sequence on the Chinese Loess Plateau; we identify underlying mechanisms using a numerical climate-model simulation of EASM response to an idealized stepwise increase in Antarctic ice volume. We infer that progressive Antarctic glaciation caused intensification of the cross-equatorial pressure gradient between an atmospheric high-pressure cell over Australia and a low-pressure cell over mid-latitude East Asia, as well as intensification of the cross-equatorial sea-surface temperature (SST) gradient. These combined atmospheric and oceanic adjustments led to EASM intensification. Our findings offer a new and more global perspective on the controls behind long-term Asian monsoon evolution.

  11. The South American Monsoon Variability over the Last Millennium in CMIP5/PMIP3 simulations

    Directory of Open Access Journals (Sweden)

    M. Rojas

    2015-12-01

    Full Text Available In this paper we assess South American Monsoon System (SAMS variability throughout the Last Millennium as depicted by the Coupled Modelling Intercomparison Project version 5/Paleo Modelling Intercomparison Project version 3 (CMIP5/PMIP3 simulations. High-resolution proxy records for the South American monsoon over this period show a coherent regional picture of a weak monsoon during the Medieval Climate Anomaly period and a stronger monsoon during the Little Ice Age (LIA. Due to the small forcing during the past 1000 years, CMIP5/PMIP3 model simulations do not show very strong temperature anomalies over these two specific periods, which in turn do not translate into clear precipitation anomalies, as suggested by rainfall reconstructions in South America. However, with an ad-hoc definition of these two periods for each model simulation, several coherent large-scale atmospheric circulation anomalies were identified. The models feature a stronger Monsoon during the LIA associated with: (i an enhancement of the rising motion in the SAMS domain in austral summer, (ii a stronger monsoon-related upper-troposphere anticyclone, (iii activation of the South American dipole, which results to a certain extent in a poleward shift in the South Atlantic Convergence Zone and (iv a weaker upper-level sub tropical jet over South America, this providing important insights into the mechanisms of these climate anomalies over South America during the past millennium.

  12. Catastrophic drought in East Asian monsoon region during Heinrich event 1

    Science.gov (United States)

    Zhou, Xin; Sun, Liguang; Chu, Yangxi; Xia, Zehui; Zhou, Xinying; Li, Xiangzhong; Chu, Zhuding; Liu, Xiangjun; Shao, Da; Wang, Yuhong

    2016-06-01

    Heinrich event 1 (H1) is an important millennial climate event during the last deglaciation. The substantial decreasing of monsoon strength in the East Asian monsoon region during the H1, as shown by stalagmite δ18O records, has been attributed to the southward shift of the intertropical convergence zone (ITCZ), which is caused by the slowdown/collapse of the Atlantic meridional overturning circulation (AMOC). However, records from different Asian monsoon regions show various trends in precipitation changes during the H1, and these trends cannot be solely interpreted by the southward shift of the ITCZ. In the present study, we reconstructed time-series of East Asian monsoon precipitation between 25,000 and 10,000 a BP from floodplain sediments in the Huai River Basin. A white sediment layer, distinct from other layers in the profile, contains significantly low TOC, tree pollen and fern spore contents, and more positive δ13Corg, and it is deposited during the H1 event. The determined TOC, pollen and δ13Corg time-series, together with previously reported stalagmite δ18O, indicate a catastrophic (severe) drought in Jianghuai Region, one of the East Asian monsoon regions, during the H1. The La Niña condition in tropical Pacific likely also contributes to the catastrophic drought in Jianghuai Region and the precipitation variations in the Asian monsoon region during the H1.

  13. Interactive Aspects of the Indian and the African Summer Monsoon Systems

    Science.gov (United States)

    Sanjeeva Rao, P.; Sikka, D. R.

    2007-09-01

    This study addresses an understanding of the possible mutual interactions of sub-seasonal variability of the two neighboring regional monsoon systems through data analysis. The NCEP/NCAR re-analysis and OLR data for three years was used to reveal the large-scale organization of convective episodes on synoptic (~5 days) and low frequency (15 50 day) scales. It is found that synoptic scale organization over both the sectors is influenced by the eastward migration of large-scale convective episodes associated with the Madden Julian Oscillation (MJO) on the low frequency scale. The organization of convection associated with the African monsoon on the synoptic scale is influenced by the pulsatory character of lower mid-troposphere and upper troposphere wind regimes moving westward over the African sector. Over the Indian region formation of low pressure areas and depressions in the monsoon trough occur in an overlapping manner under an envelope of low frequency seasonal oscillation. We have also found some correspondence between the summer monsoon rainfall over tropical North Africa and India on a decadal basis, which would suggest a common mode of multi-decadal variability in the two monsoon systems. The study points out the need to organize simultaneous field campaigns over the Indian and the African monsoon regions so as to bring out observational features of possible interactions between the two neighboring systems, which could then be validated through modeling studies.

  14. Last Glacial to Holocene history of the Indian Monsoon recorded in Andaman Sea sediments

    Science.gov (United States)

    Hathorne, E. C.; Yirgaw, D. G.; Ali, S.; Giosan, L.; Collett, T. S.; Nath, B.; Frank, M.

    2013-12-01

    Over 3 billion people live in the area influenced by the Asian monsoon, the rains of which provide vital water resources while posing a risk to human life through flooding. Despite the importance to so many the monsoon is difficult to predict and model, making its future development in a changing global climate uncertain. To help improve models and predictions, histories of monsoon variability beyond the instrumental record are required. The past variability of the Indian Monsoon is mostly known from records of monsoon wind strength over the Arabian Sea. This study uses a unique long sediment core obtained by the drill ship JOIDES Resolution in the Andaman Sea to examine the past variability of Indian Monsoon precipitation on the Indian sub-continent and directly over the ocean. Here we present multi-proxy data examining variations during the last glacial and deglaciation. The radiogenic Sr, Nd, and Pb isotopic composition of the clay fraction (fresh water. References: Antonov, J. I., D. Seidov, T. P. Boyer, R. A. Locarnini, A. V. Mishonov, and H. E. Garcia (2010). World Ocean Atlas 2009 Volume 2: Salinity. S. Levitus, Ed., NOAA Atlas NESDIS 69, U.S. Government Printing Office, Washington, D.C., 184 pp.

  15. INTENSITY INDEX OF SOUTH CHINA SEA MONSOON AND ITS VARIATION CHARACTERISTICS

    Institute of Scientific and Technical Information of China (English)

    吴尚森; 梁建茵

    2002-01-01

    According to the basic characteristics of the activities of summer monsoon in the South China Sea,Standardized index,Is,has been designed that integrates a dynamic factor(southwesterly component) and a thermodynamic factor(OLR) for the indication of summer monsoon in the South China Sea,With the index determined for individual months of June,July and August and the entire summertime from 1975 to 1999,specific months and years are indicated that are either strong or weak in monsoon intensity,The variation is studied for the patterns and Is's relationship is revealed with the onset of summer monsoon and the precipitation in Guang-dong province and China.The results show that there are quasi-10 and quasi-3-4 year cycles in the interannual variation of the monsooon over the past 25 years.When it has an early(late)onset,the summer monsoon is usually strong (weak),In the strong(weak)monsoon,years,precipitation tends to be more(less)in the first raining season of the year but normal or less(normal)in the second,in the province,but it would be more(less) in northeastern China and most parts of the northern china and south of the lower reaches of the Changjiang River and less(more)in the middle and lower reaches of the river,western part of northern China and western China.

  16. Searching for a fingerprint of global warming in the Asian summer monsoon

    Energy Technology Data Exchange (ETDEWEB)

    Stephenson, D.B.; Douville, H.; Kumar, K.R. [University of Reading, Reading (United Kingdom). Dept. of Meteorology

    2001-07-01

    This study investigates possible trends in several large-scale indices that describe the Asian summer monsoon. Results from recent atmospheric general circulating experiments are used to provide clues as to how the monsoon might be changing due to the effects of global warming. Interestingly, this study has found that the large-scale wind shear monsoon indices have been decreasing at a rate of 0.1-0.3% per year (based on NCEP/NCAR (National Centre for Atmospheric Research) analyses 1958-98) in quantitative agreement with recent results from doubled CO{sub 2} simulations made using several state-of-the-art climate models. Nevertheless, despite the weakening of the monsoon circulation, all-India rainfall shows no clear trend in either the model results or in the observation re-analyses from 1958-98. Multiple regression is used to separte out the dynamical contribution from the observed all-India rainfall index, and a clear increasing trend then emerges in the non-dynamical residual. A simple dimensionless multivariate monsoon index is proposed that could be of use in monitoring global warming changes in the monsoon. 31 refs., 2 figs., 3 tabs.

  17. An improved south Asian summer monsoon index with Monte Carlo test

    Institute of Scientific and Technical Information of China (English)

    Shi Neng; Gu Jun-Qiang; Yi Yan-Ming; Lin Zhen-Min

    2005-01-01

    The Indian monsoon intensity index suggested by Webster and Yang (WY index) is optimized and improved in this paper. At first, the area (40°E-110°E, 0°-20°N) for calculating the zonal wind-shear between 850hPa and 200hPa in the WY index is optimized and adjusted according to the significance test of differences of wind fields. Then the regionally averaged zonal wind is computed over the optimized area. Finally, the optimal linear combination of the zonal winds at the two levels is performed using the regression method, thus defining a new broad-scale circulation index for the interannual variability of the south Asian summer monsoon, i.e. the improved south Asian summer monsoon index. Results indicate that the improved south Asian summer monsoon index has two advantages: its correlation with the All Indian Summer Monsoon Rainfall index is higher than that of WY index, and its computational domain of circulation is also larger than that of WY index. The computational results based on the 1948-98 NCAR/NCEP wind data indicate that the correlation of the improved SASM index with the All Indian Summer Monsoon Rainfall index is higher than that of WY index by 0.27.

  18. Late Miocene-Pliocene Asian monsoon intensification linked to Antarctic ice-sheet growth

    Science.gov (United States)

    Ao, H.; Roberts, A. P.; Dekkers, M. J.; Liu, X.; Rohling, E. J.; Shi, Z.; An, Z.; Zhao, X.

    2016-12-01

    Environmental conditions in one of Earth's most densely populated regions, East Asia, are dominated by the monsoon. While Quaternary monsoon variability is reasonably well understood, pre-Quaternary monsoon variability and dynamics remain enigmatic. In particular, little is known about potential relationships between northern hemispheric monsoon response and major Cenozoic changes in Antarctic ice cover. Here we document long-term East Asian summer monsoon (EASM) intensification through the Late Miocene-Pliocene (˜8.2 to 2.6 Ma), and attribute this to progressive Antarctic glaciation. Our new high-resolution magnetic records of long-term EASM intensification come from the Late Miocene-Pliocene Red Clay sequence on the Chinese Loess Plateau; we identify underlying mechanisms using a numerical climate-model simulation of EASM response to an idealized stepwise increase in Antarctic ice volume. We infer that progressive Antarctic glaciation caused intensification of the cross-equatorial pressure gradient between an atmospheric high-pressure cell over Australia and a low-pressure cell over mid-latitude East Asia, as well as intensification of the cross-equatorial sea-surface temperature (SST) gradient. These combined atmospheric and oceanic adjustments led to EASM intensification. Our findings offer a new and more global perspective on the controls behind long-term Asian monsoon evolution.

  19. MONSOONS MUDE AND GOLD MUSONLAR GEMİ VE ALTIN

    Directory of Open Access Journals (Sweden)

    Paul LUNDE

    2009-12-01

    Full Text Available The “global economy” of the Middle Ages was created by linking the Indian Ocean trading networks with those of the Mediterranean Sea and its African and European hinterlands. These products, together with ceramics, textiles and sugar provided from Egypt and Syria, reached European markets almost exclusively through the Italian maritime republics of Amalfi, Pisa, Genoa and Venice. Especially the direction of the monsoon winds in the Indian Ocean and the course of the Venice trade ships were at the same direction. Thereby, Venice trade ships set out toward the end of August and made their way slowly through the Adriatic and the Aegean to Cyprus and Alexandria, timing their arrival there to coincide with the availability of monsoon-borne and by this way the products which are ned carried through Europe. İt is important to emphasize this subject that North Europe economy depends on this Monsoons where they became at Indian Ocean. As a maritime republic dedicated itself to the international trade, Venice was an anomaly in a feudal Europe that measured wealth by land, not money. Therefor this idea were encouraging their believing about ending the monopoly of the Muslim trade at the Indian Ocean. Ortaçağın global ekonomisini Hint Okyanusu ticaret hattı ile Akdeniz, Afrika ve Avrupa Hinterlantları arasındaki ticaret bağlantısı teşkil ediyordu. Avrupa ekonomisindeki gelişmelere paralel olarak Batı dünyasının gereksinim duyduğu ve Mısır ile Suriye’den tedarik edilen şeker, tekstil, seramik gibi ürünler Amalfi, Pisa, Ceneviz ve Venedik gibi İtalyan Cumhuriyetleri aracılığıyla Avrupa pazarlarına taşınmaktaydı. Özellikle Hint Okyanusu üzerindeki muson rüzgârlarının yönleriyle Venedik ticaret gemilerinin rotaları aynı doğrultudaydı. Bu suretle Ağustos ayının sonuna doğru İtalya’dan ayrılan gemiler, Adriyatik, Ege ve Kıbrıs rotasından İskenderiye’ye ulaştığı esnada musonlarla kar

  20. Cloud radar deployment for Indian Monsoon observations: Preliminary Results

    Science.gov (United States)

    Chakravarty, K.; Kalapureddy, M.; Pa, M.; Deshpandy, S.; Das, S.; Pandithurai, G.; Prabhakaran, T.; Chandrasekar, C. V.; Goswami, B.

    2013-12-01

    Indian Institute of Tropical Meteorology (IITM)'s acquired Ka-band radar for the Study of the interaction between Cloud and Environment for formation of Precipitation. Main objective of it is to make simultaneous high resolution measurements on dynamical, cloud microphysical and precipitation parameters pertain to monsoon system probably at diverse locations. The goal is to understand the interplay between cloud processes and environment that not only allow understanding the fundamental cloud-environment interactions but also precipitation formation mechanisms and further to estimate cloud contribution to the re-distribution of energy and water in climate system. For this, Polarimetric weather Doppler Radar at higher frequencies (9.5 and 35 GHz) can be a potential tool to gain knowledge on this scientific as well as societal application oriented programme. IITM's Polarimetric scanning Ka-band (cloud) radar operations started recently during May 2013. Mobile Ka-band Scanning Polarimetric Doppler Radar (KaSPR) is a cloud radar operating at wavelength of 8.5 mm with average powers of 110 W. KaSPR incorporates a conduction cooled Extended Interaction Klystron Amplifier. It is having four foot diameter Ka-band cassegrain antenna. Liquid cooled air-sealed RF unit provides excellent temperature stability. Antenna on the top of RF unit is mounted on the Elevation over azimuth pedestal which is designed to rotate continuously in the azimuth axis and a full 180 degrees in the elevation axis (horizon to horizon) with a maximum velocity of 200/sec and maximum acceleration of 120/s2. KaSPR uses dual channel 16-bit digital receiver having dynamic range of more than 80 dB with bandwidths 10 MHz. Arbitrary waveform generator capable of generating any user-defined waveform of up to 16K samples in length. It is having sensitivity of the order -45 dBZ at 5 km. KaSPR has been providing high sensitivity versatile measurements of cloud and precipitation at tropical site (Manderdev, 18

  1. Improving GEFS Weather Forecasts for Indian Monsoon with Statistical Downscaling

    Science.gov (United States)

    Agrawal, Ankita; Salvi, Kaustubh; Ghosh, Subimal

    2014-05-01

    Weather forecast has always been a challenging research problem, yet of a paramount importance as it serves the role of 'key input' in formulating modus operandi for immediate future. Short range rainfall forecasts influence a wide range of entities, right from agricultural industry to a common man. Accurate forecasts actually help in minimizing the possible damage by implementing pre-decided plan of action and hence it is necessary to gauge the quality of forecasts which might vary with the complexity of weather state and regional parameters. Indian Summer Monsoon Rainfall (ISMR) is one such perfect arena to check the quality of weather forecast not only because of the level of intricacy in spatial and temporal patterns associated with it, but also the amount of damage it can cause (because of poor forecasts) to the Indian economy by affecting agriculture Industry. The present study is undertaken with the rationales of assessing, the ability of Global Ensemble Forecast System (GEFS) in predicting ISMR over central India and the skill of statistical downscaling technique in adding value to the predictions by taking them closer to evidentiary target dataset. GEFS is a global numerical weather prediction system providing the forecast results of different climate variables at a fine resolution (0.5 degree and 1 degree). GEFS shows good skills in predicting different climatic variables but fails miserably over rainfall predictions for Indian summer monsoon rainfall, which is evident from a very low to negative correlation values between predicted and observed rainfall. Towards the fulfilment of second rationale, the statistical relationship is established between the reasonably well predicted climate variables (GEFS) and observed rainfall. The GEFS predictors are treated with multicollinearity and dimensionality reduction techniques, such as principal component analysis (PCA) and least absolute shrinkage and selection operator (LASSO). Statistical relationship is

  2. Understanding and prediction of Monsoon Intraseasonal Oscillation (Invited)

    Science.gov (United States)

    Wang, B.

    2013-12-01

    Compared with the Madden-Julian Oscillation (MJO), which prevails in boreal winter, the boreal summer intraseasonal oscillation (BSISO) has a more complex propagation pattern and spatial- temporal evolution, with prominent northward propagation and a shift of the variability center from the equatorial region to the Asian-western North Pacific and North American monsoon regions. Understanding the origin and perpetuation of BSISO has eluded scientists for decades. Improved understanding of the physical mechanisms is a prerequisite for improvement of BSISO prediction. An account of essential aspects of BSISO is presented, including (a) what sustains it or why a new rainy phase is initiated in the western equatorial Indian Ocean, (b) How a titled BSISO rain band is formed, (c) why its rain bands move northeastward in the Asian-Pacific monsoon regions, (d) how its interaction with mixed layer-ocean can play an important role in its dynamics, and (e) how it interacts with mid-latitude wave trains. Practical useful BSISO indices are proposed for monitoring and prediction purpose based on multivariate empirical orthogonal function (MV-EOF) analysis of daily anomalies of outgoing longwave radiation and zonal wind at 850 hPa in the region 10oS-40oN, 40o-160oE, for the extended boreal summer (May-October) season over the 30-year period 1981-2010. The prediction skill and predictability of the BSISO are also examined in terms of predictable modes identified form observation and multi-model ensemble (MME) hindcasts obtained from ten coupled models participated in the IntraSeasonal Variability Hindcast Experiment (ISVHE) project. It is noted that the first two MV-EOF modes are predictable using the coupled models and the bivariate temporal correlation coefficient skill for the two modes reaches 0.5 at 22-day forecast lead for the best model but at 5-day for the worst model. As a phenomenon bridging synoptic weather and seasonal variability, BSISO predictability is strongly

  3. Transport of aerosols into the UTLS and their impact on the Asian monsoon region as seen in a global model simulation

    Directory of Open Access Journals (Sweden)

    S. Fadnavis

    2013-09-01

    Full Text Available An eight-member ensemble of ECHAM5-HAMMOZ simulations for a boreal summer season is analysed to study the transport of aerosols in the upper troposphere and lower stratosphere (UTLS during the Asian summer monsoon (ASM. The simulations show persistent maxima in black carbon, organic carbon, sulfate, and mineral dust aerosols within the anticyclone in the UTLS throughout the ASM (period from July to September, when convective activity over the Indian subcontinent is highest, indicating that boundary layer aerosol pollution is the source of this UTLS aerosol layer. The simulations identify deep convection and the associated heat-driven circulation over the southern flanks of the Himalayas as the dominant transport pathway of aerosols and water vapour into the tropical tropopause layer (TTL. Comparison of model simulations with and without aerosols indicates that anthropogenic aerosols are central to the formation of this transport pathway. Aerosols act to increase cloud ice, water vapour, and temperature in the model UTLS. Evidence of ASM transport of aerosols into the stratosphere is also found, in agreement with aerosol extinction measurements from the Halogen Occultation Experiment (HALOE and Stratospheric Aerosol and Gas Experiment (SAGE II. As suggested by the observations, aerosols are transported into the Southern Hemisphere around the tropical tropopause by large-scale mixing processes. Aerosol-induced circulation changes also include a weakening of the main branch of the Hadley circulation and a reduction of monsoon precipitation over India.

  4. Study on the association of green house gas (CO2) with monsoon rainfall using AIRS and TRMM satellite observations

    Science.gov (United States)

    Singh, R. B.; Janmaijaya, M.; Dhaka, S. K.; Kumar, V.

    Monsoon water cycle is the lifeline to over 60 per cent of the world's population. Throughout history, the monsoon-related calamities of droughts and floods have determined the life pattern of people. The association of Green House Gases (GHGs) particularly Carbon dioxide (CO2) with monsoon has been greatly debated amongst the scientific community in the past. The effect of CO2 on the monsoon rainfall over the Indian-Indonesian region (8-30°N, 65°-100°E) is being investigated using satellite data. The correlation coefficient (Rxy) between CO2 and monsoon is analysed. The Rxy is not significantly positive over a greater part of the study region, except a few regions. The inter-annual anomalies of CO2 is identified for playing a secondary role to influencing monsoon while other phenomenon like ENSO might be exerting a much greater influence.

  5. Simulation of the Indian monsoon and its variability during the last millennium

    Directory of Open Access Journals (Sweden)

    S. Polanski

    2013-02-01

    Full Text Available The general circulation model ECHAM5 has been used to simulate the Indian monsoon and its variability during the Medieval Warm Period (MWP; 900–1100 AD, the Little Ice Age (LIA; 1515–1715 AD and for recent climate (REC; 1800–2000 AD. The focus is on the analysis of external drivers and internal feedbacks leading to extreme rainfall events over India from interannual to multidecadal time scale. An evaluation of spatiotemporal monsoon patterns with present-day observation data is in agreement with other state-of-the-art monsoon modeling studies. The simulated monsoon intensity on multidecadal time scale is weakened (enhanced in summer (winter due to colder (warmer SSTs in the Indian Ocean. Variations in solar insolation are the main drivers for these SST anomalies, verified by very strong temporal anticorrelations between Total Solar Irradiance and All-India-Monsoon-Rainfall in summer monsoon months. The external solar forcing is coupled and overlain by internal climate modes of the ocean (ENSO and IOD with asynchronous intensities and lengths of periods.

    In addition, the model simulations have been compared with a relative moisture index derived from paleoclimatic reconstructions based on various proxies and archives in India. In this context, the Lonar record in Central India has been highlighted and evaluated the first time. The simulated relative annual rainfall anomalies in comparison to present-day climate are in agreement (disagreement with the reconstructed moisture index for MWP (LIA climate.

    In order to investigate the interannual monsoon variability with respect to monsoon failures, dry summer monsoon composites for 30-yr-long periods of MWP, LIA and REC have been further analysed. Within dry years of LIA, the summer rainfall over India and surrounding oceans is less than in MWP indicating stronger drying conditions due to a stronger summer solar insolation forcing coupled with variations in ENSO. To quantify the

  6. Future of West African Monsoon in A Warming Climate

    Science.gov (United States)

    Raj, Jerry; Kunhu Bangalath, Hamza; Stenchikov, Georgiy

    2016-04-01

    West Africa is the home of more than 300 million people whose agriculture based economy highly relies on West African Monsoon (WAM), which produces a mean annual rainfall of 150 - 2,500 mm and variability and change of which have devastating impact on the local population. The observed widespread drought in West Africa during the 1970s and 1980s was the most significant drought at regional scale during the twentieth century. In this study, a high resolution AGCM, High Resolution Atmospheric Model (HiRAM), is used to study the effects of anthropogenic greenhouse warming on WAM. HiRAM is developed at GFDL based on AM2 and employs a cubed-sphere finite volume dynamical core and uses shallow convective scheme (for moist convection and stratiform cloudiness) instead of deep convective parameterization. Future projections are done using two representative concentration pathways, RCP 4.5 and RCP 8.5 from 2007 to 2050 at C360 (~25 km) resolution. Both RCP 4.5 and RCP 8.5 scenarios predict warming over West Africa during boreal summer, especially over Western Sahara. Also, both scenarios predict southward shift in WAM rainfall pattern and drying over Southern Sahara, while RCP 8.5 predicts enhanced rainfall over Gulf of Guinea. The intensification of rainfall over tropical latitudes is caused by increased low level winds due to warm SST over Gulf of Guinea.

  7. Mountain Heavy Rainfall Measurement Experiments in a Subtropical Monsoon Environment

    Science.gov (United States)

    Jong-Dao Jou, Ben; Chi-June Jung, Ultimate; Lai, Hsiao-Wei; Feng, Lei

    2014-05-01

    Quantitative rainfall measurement experiments have been conducted in Taiwan area for the past 5 years (since 2008), especially over the complex terrain region. In this paper, results from these experiments will be analyzed and discussed, especially those associated with heavy rain events in the summer monsoon season. Observations from s-band polarimetric radar (SPOL of NCAR) and also x-band vertically-pointing radar are analyzed to reveal the high resolution temporal and spatial variation of precipitation structure. May and June, the Meiyu season in the area, are months with subtropical frontal rainfall events. Mesoscale convective systems, i.e., pre-frontal squall lines and frontal convective rainbands, are very active and frequently produce heavy rain events over mountain areas. Accurate quantitative precipitation measurements are needed in order to meet the requirement for landslide and flood early warning purpose. Using ground-based disdrometers and vertically-pointing radar, we have been trying to modify the quantitative precipitation estimation in the mountain region by using coastal operational radar. In this paper, the methodology applied will be presented and the potential of its application will be discussed. *corresponding author: Ben Jong-Dao Jou, jouben43@gmail.com

  8. First observations of Gigantic Jets from Monsoon Thunderstorms over India

    Science.gov (United States)

    Singh, Rajesh; Maurya, Ajeet; Chanrion, Olivier; Neubert, Torsten; Cummer, Steven; Mlynarczyk, Janusz; Bór, József; Siingh, Devendraa; Cohen, Morris; Kumar, Sushil

    2016-04-01

    Gigantic Jets are electric discharges from thunderstorm cloud tops to the bottom of the ionosphere at ~80 km altitude. After their first discovery in 2001, relatively few observations have been reported. Most of these are from satellites at large distances and a few tens from the ground at higher spatial resolution. Here we report the first Gigantic Jets observed in India from two thunderstorm systems that developed over the land surface from monsoon activity, each storm producing two Gigantic Jets. The jets were recorded by a video camera system at standard video rate (20 ms exposure) at a few hundred km distance. ELF measurements suggest that the jets are of the usual negative polarity and that they develop in less than 40 ms, which is faster than most jets reported in the past. The jets originate from the leading edge of a slowly drifting convective cloud complex close to the highest regions of the clouds and carry ~25 Coulomb of charge to the ionosphere. One jet has a markedly horizontal displacement that we suggest is caused by a combination of close-range cloud electric fields at inception, and longer-range cloud fields at larger distances during full development. The Gigantic Jets are amongst the few that have been observed over land.

  9. Surface response to rain events throughout the West African monsoon

    Directory of Open Access Journals (Sweden)

    F. Lohou

    2013-07-01

    Full Text Available This study analyses the response of the continental surface to a rain event, taking advantage of the long-term near-surface measurements over different vegetation covers at different latitudes, acquired during the African Monsoon Multidisciplinary Analysis (AMMA experiment. The simulated surface response by nine land surface models involved in AMMA Land Model Intercomparison Project (ALMIP, is compared to the observations. The surface response, described via the evaporative fraction, evolves in two steps: the immediate surface response and the surface recovery. The immediate surface response corresponds to an increase in the evaporative fraction occurring immediately after the rain. For all the experimental sites, the immediate surface response is strongest when the surface is relatively dry. From the simulation point of view, this relationship is highly model and latitude dependent. The recovery period, characterized by a decrease of the evaporative fraction during several days after the rain, follows an exponential relationship whose rate is vegetation dependent: from 1 day over bare soil to 70 days over the forest. Land surface models correctly simulate the decrease of EF over vegetation covers whereas a slower and more variable EF decrease is simulated over bare soil.

  10. Indian monsoon variability in relation to Regional Pressure Index

    Indian Academy of Sciences (India)

    S S Dugam; S B Kakade

    2003-12-01

    In this paper Regional Pressure Index (RPI) over the Indian region (20°N-40°N and 70°E-85°E) has been constructed for 101 years (1899-1999) on a monthly scale. The relationship of these indices was carried out with the Indian Summer Monsoon Rainfall (June-September) (ISMR) over the various homogeneous regions, for all the time scales. From the analysis it has been seen that RPI in the month of May is significantly associated with ISMR over various regions on all the scales. The relationship is statistically significant at 1% level. The study reveals that RPI in the month of May and January will be a new precursor for the long range forecasting of ISMR on the smaller spatial scale. On the decadal and climatological scale, winter and spring time RPI show a significant inverse relationship with the rainfall over the regions Peninsular India (PI) and North West India (NWI), while the association is direct with Central North East India (CNEI) and North East India (NEI). The relationship is significant at 0.1 and 1% level respectively.

  11. On the role of convective systems over the northwest Pacific and monsoon activity over the Indian subcontinent

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar, M.R.; Babu, A.K.; Reason, C.

    .e. years with well below average rainfall) as compared to excess monsoon years (years with well above average rainfall). Based on these previously found associations involving various characteristics of convective activity in the region, this study seeks... and also on the quantum of monsoon rainfall for several contrasting monsoon years. 2. Data Data for convective systems in the northwest Pacific Ocean (NWP) were acquired from the UNISYS website (http://weather.unisys.com) and originate from the Joint...

  12. Monsoon-influenced glacier retreat in the Ladakh Range, Jammu and Kashmir

    Science.gov (United States)

    Chudley, Tom; Miles, Evan; Willis, Ian

    2016-04-01

    While the majority of glaciers in the Himalaya-Karakoram mountain chain are receding in response to climate change, stability and even growth is observed in the Karakoram, where glaciers also exhibit widespread surge-type behaviour. Changes in the accumulation regime driven by mid-latitude westerlies could explain such stability relative to the monsoon-fed glaciers of the Himalaya, but a lack of detailed meteorological records presents a challenge for climatological analyses. We therefore analyse glacier changes for an intermediate zone of the HKH to characterise the transition between the substantial retreat of Himalayan glaciers and the surging stability of Karakoram glaciers. Using Landsat imagery, we assess changes in glacier area and length from 1991-2014 across a ˜140 km section of the Ladakh Range, Jammu and Kashmir. Bordering the surging, stable portion of the Karakoram to the north and the Western Himalaya to the southeast, the Ladakh Range represents an important transitional zone to identify the potential role of climatic forcing in explaining differing glacier behaviour across the region. A total of 878 glaciers are semi-automatically identified in 1991, 2002, and 2014 using NDSI (thresholds chosen between 0.30 and 0.45) before being manually corrected. Ice divides and centrelines are automatically derived using an established routine. Total glacier area for the study region is in line with that Randolph Glacier Inventory (RGI) and ˜25% larger than the GLIMS Glacier Database, which is apparently more conservative in assigning ice cover in the accumulation zone. However, the RGI appears notably less successful in identifying glacier termini. Preliminary analysis of glaciers in our study area suggest an overall areal decline of -17.21±7.50% between 1991-2014., a figure more similar to the Zanskar ranges to the south than the Karakoram to the north. No evidence of surge-type behaviour is observed in the study area over this period. Glaciers tend to be

  13. Future projection of mean and variability of the Asian Summer Monsoon and Indian Ocean Climate systems

    Energy Technology Data Exchange (ETDEWEB)

    Annamalai, H [IPRC, University of Hawaii

    2014-09-15

    The overall goal of this project is to assess the ability of the CMIP3/5 models to simulate the Indian-Ocean monsoon systems. The PI along with post-docs investigated research issues ranging from synoptic systems to long-term trends over the Asian monsoon region. The PI applied diagnostic tools such as moist static energy (MSE) to isolate: the moist and radiative processes responsible for extended monsoon breaks over South Asia, precursors in the ENSO-monsoon association, reasons for the drying tendency over South Asia and the possible effect on tropical Indian Ocean climate anomalies influencing certain aspects of ENSO characteristics. By diagnosing various observations and coupled model simulations, we developed working hypothesis and tested them by carrying out sensitivity experiments with both linear and nonlinear models. Possible physical and dynamical reasons for model sensitivities were deduced. On the teleconnection front, the ability of CMIP5 models in representing the monsoon-desert mechanism was examined recently. Further more, we have applied a suite of diagnostics and have performed an in depth analysis on CMIP5 integrations to isolate the possible reasons for the ENSO-monsoon linkage or lack thereof. The PI has collaborated with Dr. K.R. Sperber of PCMDI and other CLIVAR Asian-Australian monsoon panel members in understanding the ability of CMIP3/5 models in capturing monsoon and its spectrum of variability. The objective and process-based diagnostics aided in selecting models that best represent the present-day monsoon and its variability that are then employed for future projections. Two major highlights were an invitation to write a review on present understanding monsoons in a changing climate in Nature Climate Change, and identification of an east-west shift in observed monsoon rainfall (more rainfall over tropical western Pacific and drying tendency over South Asia) in the last six decades and attributing that shift to SST rise over the tropical

  14. Summer monsoon onset-induced changes of autotrophic pico- and nanoplankton in the largest monsoonal estuary along the west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Mohan, A.P.; Jyothibabu, R.; Jagadeesan, L.; Lallu, K.R.; Karnan, C.

    , the total abundance of picoplankton community remained virtually unchanged in the upstream due to an increase in the abundance of picoeukaryotes. On the other hand, the autotrophic nanoplankton abundance increased from pre-monsoon levels of av. 3.8×106...

  15. Thermally driven upslope flow in mountainous terrain

    Science.gov (United States)

    Liberzon, Dan; Hocut, Christopher; Fernando, Harindra; Environmental Fluid Dynamics Team

    2011-11-01

    Buoyancy driven up-slope flow and its separation from mountain apex are two important processes that determine meso and regional flows in mountainous areas. Such flow configurations have applications from mountain meteorology to large scale monsoonal circulation. A combined experimental and theoretical study toward improving our understanding of the mechanisms governing upslope flow processes, in particular, generation of upstream circulating cells and plume rise at the apex is presented. The experiments were performed in a 1.25x.35x.3 m water tank, using an inclined (10 to 30 degrees from the horizontal) electrical foil as the heated slope. Under certain condition the flow configuration produced stable circulation cells and rising limited plumes of finite height. Particle Tracking Velocimetry and flow visualization techniques were used for the diagnostics of velocity field and plume rise height, and relevant salient dimensionless quantities were evaluated in terms of governing parameters. Theoretical arguments are presented to explain the results. Parameter ranges for the appearance of characteristic flow patterns are also delineated.

  16. Query Driven Visualization

    CERN Document Server

    Buddelmeijer, Hugo

    2011-01-01

    The request driven way of deriving data in Astro-WISE is extended to a query driven way of visualization. This allows scientists to focus on the science they want to perform, because all administration of their data is automated. This can be done over an abstraction layer that enhances control and flexibility for the scientist.

  17. EVOLUTION OF TROPOSPHERIC TEMPERATURE FIELDS AND CORRESPONDING THERMAL MECHANISMS BEFORE/AFTER ONSET PERIODS OF ASIAN SUMMER MONSOON

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The evolution of the tropospheric temperature fields over Indian and South China Sea monsoon areas and their thermal mechanisms are compared and analyzed during the period from March to June, 1996. The results show that the onsets of the Indian and South China Sea summer monsoons are closely associated with the seasonal warming in the troposphere over the zonal belt of 10° N ~ 30° N in these areas, which leads to the inversion of meridional temperature gradient. During the pre-onset period, the warming over the South China Sea monsoon region is mainly due to the warm horizontal advection and diabatic (latent) heating processes. Meanwhile, the warming is suppressed by the vertical adiabatic process (cooling). In spring over the Indian monsoon region, the significant adiabatic heating due to the subsidence motion, which compensates the cooling due to the strong cold advection and diabatic cooling processes, results in a larger warming rate than over the South China Sea monsoon region. However, the meridional temperature gradient over the Indian monsoon region is so large during the late winter and early spring that it takes longer time to warm the troposphere to have the reversion of meridional temperature gradient than it does over the South China Sea monsoon region. It results in the phenomenon that the South China Sea summer monsoon generally breaks out earlier than the Indian summer monsoon.

  18. Low-Frequency Vortex Pair over the Tropical Eastern Indian Ocean and the South China Sea Summer Monsoon Onset

    Institute of Scientific and Technical Information of China (English)

    PAN Jing; LI Chong-Yin

    2011-01-01

    In this paper, the relationship between a pair of low-frequency vortexes over the equatorial Indian Ocean and the South China Sea (SCS) summer monsoon onset is studied based on a multi-year (1980-2003) analysis. A pair of vortexes symmetric about the equator is an important feature prior to the SCS summer monsoon onset. A composite analysis shows that the life cycle of the pair of vortexes is closely associated with the SCS summer monsoon onset. The westerly between the twin cyclones is an important factor to the SCS summer monsoon onset process.

  19. Changes in the in-phase relationship between the Indian and subsequent Australian summer monsoons during the past five decades

    Directory of Open Access Journals (Sweden)

    J.-Y. Yu

    2007-10-01

    Full Text Available This study examines the decadal changes in the in-phase relationship between Indian summer monsoon and the subsequent Australian summer monsoon using observational data from 1950–2005. The in-phase relationship is the tendency for a strong Indian summer monsoon to be followed by a strong Australian summer monsoon and vice versa. It is found that the in-phase relationship was weak during the late 1950s and early 1960s, strengthened to a maximum in the early 1970s just before the 1976/77 Pacific climate shift, then declined until the late 1990s. Pacific SST anomalies are noticed to have strong persistence from boreal to austral summer, providing the memory to connect the Indian and subsequent Australian summer monsoon. The simultaneous correlation between the Pacific SST anomalies and the Indian summer monsoon is always strong. It is the weakening and strengthening of the simultaneous correlation between the Australian summer monsoon and the Pacific SST anomalies that contributes to the decadal variations of the in-phase monsoon relation. This study suggests that the interaction between the Australian monsoon and the Pacific Ocean is crucial to tropical climate variability and has experienced significant changes over the past five decades.

  20. Seasonal and Intraseasonal Variability of Mesoscale Convective Systems over the South Asian Monsoon Region

    Energy Technology Data Exchange (ETDEWEB)

    Virts, Katrina S.; Houze, Robert A.

    2016-12-01

    Seasonal and intraseasonal differences in mesoscale convective systems (MCSs) over South Asia are examined using A-Train satellites, a ground-based lightning network, and reanalysis fields. Pre-monsoon (April-May) MCSs occur primarily over Bangladesh and the eastern Bay of Bengal. During the monsoon (June-September), small MCSs occur over the Meghalaya Plateau and northeast Himalayan notch, while large and connected MCSs are most widespread over the Bay of Bengal. Monsoon MCSs produce less lightning and exhibit more extensive stratiform and anvil reflectivity structures in CloudSat observations than do pre-monsoon MCSs. During the monsoon season, Bay of Bengal and Meghalaya Plateau MCSs vary with the 30-60 day northward-propagating intraseasonal oscillation, while northeast Himalayan notch MCSs are associated with weak large-scale anomalies but locally enhanced CAPE. During intraseasonal active periods, a zone of enhanced large and connected MCSs, precipitation, and lightning extends from the northeastern Arabian Sea southeast over India and the Bay of Bengal, flanked by suppressed anomalies. Spatial variability is observed within this enhancement zone: lightning is most enhanced where MCSs are less enhanced, and vice versa. Reanalysis composites indicate that Bay of Bengal MCSs are associated with monsoon depressions, which are frequent during active monsoon periods, while Meghalaya Plateau MCSs are most frequent at the end of break periods, as anomalous southwesterly winds strengthen moist advection toward the terrain. Over both regions, MCSs exhibit more extensive stratiform and anvil regions and less lightning when the large-scale environment is moister, and vice versa.

  1. Adaptability of Irrigation to a Changing Monsoon in India: How far can we go?

    Science.gov (United States)

    Zaveri, E.; Grogan, D. S.; Fisher-Vanden, K.; Frolking, S. E.; Wrenn, D. H.; Nicholas, R.

    2014-12-01

    Agriculture and the monsoon are inextricably linked in India. A large part of the steady rise in agricultural production since the onset of the Green Revolution in the 1960's has been attributed to irrigation. Irrigation is used to supplement and buffer crops against precipitation shocks, but water availability for such use is itself sensitive to the erratic, seasonal and spatially heterogeneous nature of the monsoon. We provide new evidence on the relationship between monsoon changes, irrigation variability and water availability by linking a process based hydrology model with an econometric model for one of the world's most water stressed countries. India uses more groundwater for irrigation than any other country, and there is substantial evidence that this has led to depletion of groundwater aquifers. First, we build an econometric model of historical irrigation decisions using detailed agriculture and weather data spanning 35 years. Multivariate regression models reveal that for crops grown in the wet season, irrigation is sensitive to distribution and total monsoon rainfall but not to ground or surface water availability. For crops grown in the dry season, total monsoon rainfall matters most, and its effect is sensitive to groundwater availability. The historical estimates from the econometric model are used to calculate future irrigated areas under three different climate model predictions of monsoon climate for the years 2010 - 2050. These projections are then used as input to a physical hydrology model, which quantifies supply of irrigation water from sustainable sources such as rechargeable shallow groundwater, rivers and reservoirs, to unsustainable sources such as non- rechargeable groundwater. We find that the significant variation in monsoon projections lead to very different results. Crops grown in the dry season show particularly divergent trends between model projections, leading to very different groundwater resource requirements.

  2. Systematic errors in Monsoon simulation: importance of the equatorial Indian Ocean processes

    Science.gov (United States)

    Annamalai, H.; Taguchi, B.; McCreary, J. P., Jr.; Nagura, M.; Miyama, T.

    2015-12-01

    H. Annamalai1, B. Taguchi2, J.P. McCreary1, J. Hafner1, M. Nagura2, and T. Miyama2 International Pacific Research Center, University of Hawaii, USA Application Laboratory, JAMSTEC, Japan In climate models, simulating the monsoon precipitation climatology remains a grand challenge. Compared to CMIP3, the multi-model-mean (MMM) errors for Asian-Australian monsoon (AAM) precipitation climatology in CMIP5, relative to GPCP observations, have shown little improvement. One of the implications is that uncertainties in the future projections of time-mean changes to AAM rainfall may not have reduced from CMIP3 to CMIP5. Despite dedicated efforts by the modeling community, the progress in monsoon modeling is rather slow. This leads us to wonder: Has the scientific community reached a "plateau" in modeling mean monsoon precipitation? Our focus here is to better understanding of the coupled air-sea interactions, and moist processes that govern the precipitation characteristics over the tropical Indian Ocean where large-scale errors persist. A series idealized coupled model experiments are performed to test the hypothesis that errors in the coupled processes along the equatorial Indian Ocean during inter-monsoon seasons could potentially influence systematic errors during the monsoon season. Moist static energy budget diagnostics has been performed to identify the leading moist and radiative processes that account for the large-scale errors in the simulated precipitation. As a way forward, we propose three coordinated efforts, and they are: (i) idealized coupled model experiments; (ii) process-based diagnostics and (iii) direct observations to constrain model physics. We will argue that a systematic and coordinated approach in the identification of the various interactive processes that shape the precipitation basic state needs to be carried out, and high-quality observations over the data sparse monsoon region are needed to validate models and further improve model physics.

  3. Impact of Ocean-Continent Distribution over Southern Asia on the Formation of Summer Monsoon

    Institute of Scientific and Technical Information of China (English)

    JIN Qihua; HE Jinhai; CHEN Longxun; ZHU Congwen

    2006-01-01

    Using the CCM3/NCAR, a series of numerical experiments are designed to explore the effect of ocean-land interlaced distributions of Africa-Arabian Sea-India Peninsula-Bay of Bengal (BOB)-Indo-China PeninsulaSouth China Sea on the formation of the Asian summer monsoon circulation (ASMC). The results show that the thermal difference between African or Indian Subcontinent and nearby areas including the Indian Ocean,Arabian Sea, and part of BOB is the primary mechanism that maintains the Indian monsoon circulation.In the experiment getting rid of these two continents, the Indian monsoon system (IMS) members, i.e., the Somali cross-equatorial jet (40°E) and the southwesterly monsoon over the Arabian Sea and BOB, almost disappear. Moreover, the Hadley circulation weakens dominantly. It also proves that Africa has greater effect than Indian Subcontinent on the IMS.However, the existence of Indo-China Peninsula and Australia strengthens the East Asian monsoon system (EAMS). The thermal contrast between Indo-China Peninsula and SCS, Australia and western Pacific Ocean plays an important role in the formation of the tropical monsoon to the south of the EAMS. When the Indo-China Peninsula is masked in the experiment, the cross-equatorial flow (105°E and 125°E) vanishes,so does the southwesterly monsoon usually found over East Asia, and EAMS is enfeebled significantly. In addition, the impacts of these thermal contrasts on the distribution of the summer precipitation and surface temperature are investigated.

  4. Surface and upper air meteorological features during onset phase of 2003 monsoon

    Indian Academy of Sciences (India)

    O P Singh; H R Hatwar; Onkari Prasad

    2007-08-01

    The second campaign of the Arabian Sea Monsoon Experiment (ARMEX-II) was conducted in two phases viz., March–April and May–June 2003. In the present work, the buoy and ocean research vessel data collected during the second phase of ARMEX-II have been analysed to bring out the characteristic features of monsoon onset. The results have shown that the thermodynamical features such as build up of lower tropospheric instability and increased height of zero degree isotherm occurred about a week before the monsoon onset over Kerala and adjoining southeast Arabian Sea. There was a sharp fall in the temperature difference between 850 and 500 hPa, and the height of zero degree isotherm about 2–3 days before the monsoon onset. The flux of sensible heat was positive (sea to air) over south Arabian Sea during the onset phase. Over the Bay of Bengal higher negative (air to sea) values of sensible flux prevailed before the monsoon onset which became less negative with the advance of monsoon over that region. The pre-onset period was characterized by large sea surface temperature (SST) gradient over the Arabian Sea with rapid decrease towards north of the warm pool region. The buoy observations have shown that SST remained close to 30.5°C in the warm pool region during the pre-onset period in 2003 but only 2–3 degrees away (north of this region) SSTs were as low as 28.5-29°C. An interesting aspect of sea level pressure (SLP) variability over the Indian seas during the onset phase of summer monsoon 2003 was undoubtedly, the highest SLP in the warm pool region inspite of very high SSTs.

  5. The effect of El-Niño on South Asian Monsoon and agricultural production

    Science.gov (United States)

    Mukherjee, A.

    2015-12-01

    Mukherjee A, Wang S.Y.Abstract:The South Asian Monsoon has a prominent and significant impact on South Asian countries like India, Bangladesh, Nepal, Pakistan, Sri Lanka and it is one of the most studied phenomena in the world. The monsoon is historically known to be influenced by El Niño-Southern Oscillation (ENSO). The inter-annual and inter-decadal variability of seasonal precipitation over India strongly depends upon the ENSO phasing. The average southwest monsoon rainfall received during the years with El Niño was found to be less compared to normal years and the average rainfall during the northeast monsoon is higher in coastal Andhra Pradesh. ENSO is anti-correlated with Indian summer monsoon (ISM). The last prominent effect of ENSO on India's monsoon occurred in 2009 with 23% reduction in annual rainfall, reducing summer sown crops such as rice, sugar cane etc. and pushing up food prices. Climatic resources endowment plays a major role in planning agricultural production in tropical and sub-tropical environment especially under rain-fed agriculture, and so contingent crop planning drawn on this relationship would help to mitigate the effects of ENSO episodes in the region. The unexplored area in this domain of research is the changes in the frequency and intensity of ENSO due to global warming and its impact on ENSO prediction and agricultural management practices. We analyze the last 30 years datasets of Pacific SST, and precipitation and air temperature over Southeast Asia to examine the evolution of ENSO teleconnections with ISM, as well as making estimates of drought indices such as Palmer Drought Severity Index. This research can lead toward better crop management strategies in the South Asian monsoon region.

  6. Understanding land surface response to changing South Asian monsoon in a warming climate

    Directory of Open Access Journals (Sweden)

    M. V. S. Ramarao

    2015-05-01

    Full Text Available Recent studies have drawn attention to a significant weakening trend of the South Asian monsoon circulation and an associated decrease in regional rainfall during the last few decades. While surface temperatures over the region have steadily risen during this period, most of the CMIP (Coupled Model Intercomparison Project global climate models have difficulties in capturing the observed decrease of monsoon precipitation, thus limiting our understanding of the regional land surface response to monsoonal changes. This problem is investigated by performing two long-term simulation experiments, with and without anthropogenic forcing, using a variable resolution global climate model having high-resolution zooming over the South Asian region. The present results indicate that anthropogenic effects have considerably influenced the recent weakening of the monsoon circulation and decline of precipitation. It is seen that the simulated increase of surface temperature over the Indian region during the post-1950s is accompanied by a significant decrease of monsoon precipitation and soil moisture. Our analysis further reveals that the land surface response to decrease of soil moisture is associated with significant reduction in evapotranspiration over the Indian land region. A future projection, based on the representative concentration pathway 4.5 (RCP4.5 scenario of the Intergovernmental panel on Climate Change (IPCC, using the same high-resolution model indicates the possibility for detecting the summer-time soil drying signal over the Indian region during the 21st century, in response to climate change. While these monsoon hydrological changes have profound socioeconomic implications, the robustness of the high-resolution simulations provides deeper insights and enhances our understanding of the regional land surface response to the changing South Asian monsoon.

  7. Three centuries of Myanmar monsoon climate variability inferred from teak tree rings

    Science.gov (United States)

    D'Arrigo, Rosanne; Palmer, Jonathan; Ummenhofer, Caroline C.; Kyaw, Nyi Nyi; Krusic, Paul

    2011-12-01

    Asian monsoon extremes critically impact much of the globe’s population. Key gaps in our understanding of monsoon climate remain due to sparse coverage of paleoclimatic information, despite intensified recent efforts. Here we describe a ring width chronology of teak, one of the first high-resolution proxy records for the nation of Myanmar. Based on 29 samples from 20 living trees and spanning from 1613-2009, this record, from the Maingtha forest reserve north of Mandalay, helps fill a substantial gap in spatial coverage of paleoclimatic records for monsoon Asia. Teak growth is positively correlated with rainfall and Palmer Drought Severity Index variability over Myanmar, during and prior to the May-September monsoon season (e.g., r = 0.38 with Yangon rainfall, 0.001, n 68). Importantly, this record also correlates significantly with larger-scale climate indices, including core Indian rainfall (23°N, 76°E a particularly sensitive index of the monsoon), and the El Niño-Southern Oscillation (ENSO). The teak ring width value following the so-called 1997-98 El Niño of the Century suggests that this was one of the most severe droughts in the past ˜300 years in Myanmar. Evidence for past dry conditions inferred for Myanmar is consistent with tree-ring records of decadal megadroughts developed for Thailand and Vietnam. These results confirm the climate signature related to monsoon rainfall in the Myanmar teak record and the considerable potential for future development of climate-sensitive chronologies from Myanmar and the broader region of monsoon Asia.

  8. Extreme monsoon precipitation events over South Asia in a warming world

    Science.gov (United States)

    Raghavan, K.; Sabin, T. P.; Mujumdar, M.; Priya, P.

    2012-04-01

    The recent series of flood events over Pakistan and Northwest India during the monsoon seasons of 2010 and 2011 are examples of extreme phenomena during the last century that have evoked considerable interest among various scientific communities. One of the causes for the 2010 intense precipitation over Pakistan has been attributed to the interaction between the tropical monsoon surge and southward intruding extra-tropical circulation anomalies (Hong et al. 2011). On the other hand, it has been hypothesized by Mujumdar et al. (2012) that the westward shift of the West Pacific Subtropical High (WPSH) in response to the strong La Nina conditions during 2010 was instrumental in altering the convection and circulation over the Bay of Bengal and the monsoon trough region, which in turn sustained the moist convective activities over Indo-Pak through transport of moisture from the Arabian Sea. However several aspects of the dynamics of these intense monsoon precipitation events are not adequately understood especially when atmospheric convective instabilities are expected to amplify in the backdrop of the ongoing global warming. Here, we have carried out a set of ensemble simulation experiments using a high-resolution global climate model to understand the evolution of intense monsoon precipitation events over Pakistan and Northwest India as in 2010. The results based on the model simulations indicate that while interactions among the WPSH, the South Asian monsoon trough and sub-tropical westerlies are conducive for development of convective instabilities over the Indo-Pak region, the local convective activities are found to significantly amplify in response to the large build up of moisture associated with global warming. The present results have implications in understanding how extreme monsoon precipitation events in the Indo-Pak region might have responded to past climatic variations.

  9. On the link between extreme floods and excess monsoon epochs in South Asia

    Energy Technology Data Exchange (ETDEWEB)

    Kale, Vishwas [University of Pune, Department of Geography, Pune (India)

    2012-09-15

    This paper provides a synoptic view of extreme monsoon floods on all the nine large rivers of South Asia and their association with the excess (above-normal) monsoon rainfall periods. Annual maximum flood series for 18 gauging stations spread over four countries (India, Pakistan, Bangladesh and Nepal) and long-term monsoon rainfall data were analyzed to ascertain whether the extreme floods were clustered in time and whether they coincided with multi-decade excess monsoon rainfall epochs at the basin level. Simple techniques, such as the Cramer's t-test, regression and Mann-Kendall (MK) tests and Hurst method were used to evaluate the trends and patterns of the flood and rainfall series. MK test reveals absence of any long-term tendency in all the series. However, the Cramer's t test and Hurst-Mandelbrot rescaled range statistic provide evidence that both rainfall and flood time series are persistent. Using the Cramer's t-test the excess monsoon epochs for each basin were identified. The excess monsoon periods for different basins were found to be highly asynchronous with respect to duration as well as the beginning and end. Three main conclusions readily emerge from the analyses. Extreme floods (>90th percentile) in South Asia show a tendency to cluster in time. About three-fourth of the extreme floods have occurred during the excess monsoon periods between {proportional_to}1840 and 2000 AD, implying a noteworthy link between the two. The frequency of large floods was higher during the post-1940 period in general and during three decades (1940s, 1950s and 1980s) in particular. (orig.)

  10. Interaction of Convective Organization and Monsoon Precipitation, Atmosphere, Surface and Sea (INCOMPASS)

    Science.gov (United States)

    Turner, A. G.; Bhat, G. S.; Evans, J. G.; Madan, R.; Marsham, J. H.; Martin, G.; Mitra, A. K.; Mrudula, G.; Parker, D. J.; Pattnaik, S.; Rajagopal, E. N.; Taylor, C.; Tripathi, S. N.

    2016-12-01

    INCOMPASS will build on a field and aircraft measurement campaign from the 2016 monsoon onset to better understand and predict monsoon rainfall. The monsoon supplies the majority of water in South Asia, however modelling and forecasting the monsoon from days to the season ahead is limited by large model errors that develop quickly. Likely problems lie in physical parametrizations such as convection, the boundary layer and land surface. At the same time, lack of detailed observations prevents more thorough understanding of monsoon circulation and its interaction with the land surface; a process governed by boundary layer and convective cloud dynamics. From May to July 2016, INCOMPASS used a modified BAe-146 jet aircraft operated by the UK Facility for Airborne Atmospheric Measurements (FAAM), for the first project of this scale in India. The India and UK team flew around 100 hours of science sorties from bases in northern and southern India. Flights from Lucknow in the northern plains took measurements to the west and southeast to allow sampling of the complete contrast from dry desert air to the humid environment over the north Bay of Bengal. These routes were repeated in the pre-monsoon and monsoon phases, measuring contrasting surface and boundary layer structures. In addition, flights from the southern base in Bengaluru measured contrasts from the Arabian Sea, across the intense rains of the Western Ghats mountains, over the rain shadow in southeast India and over the southern Bay of Bengal. Flight planning was performed with the aid of forecasts from a new UK Met Office 4km limited area model. INCOMPASS also installed a network of surface flux towers, as well as operating a cloud-base ceilometer and performing intensive radiosonde launches from a supersite in Kanpur. This presentation will outline preliminary results from the field campaign including new observations of the surface, boundary layer structure and atmospheric profiles together with detailed

  11. Regional climate model experiments to investigate the Asian monsoon in the Late Miocene

    Directory of Open Access Journals (Sweden)

    H. Tang

    2011-03-01

    Full Text Available The Late Miocene (11.6–5.3 Ma is a crucial period for the Asian monsoon evolution. However, the spatiotemporal changes of the Asian monsoon system in the Late Miocene are still ambiguous, and the mechanisms responsible for these changes are debated. Here, we present a simulation of the Asian monsoon climate (0 to 60° N and 50 to 140° E in the Tortonian (11–7 Ma using the regional climate model CCLM3.2. We employ relatively high spatial resolution (1° × 1° and adapt the physical boundary conditions such as topography, land-sea distribution and vegetation in the regional model to represent the Late Miocene. As climatological forcing, the output of a Tortonian run with a fully-coupled atmosphere-ocean general circulation model is used. Our results show a stronger-than-present E-Asian winter monsoon wind in the Tortonian, as a result of the enhanced mid-latitude westerly wind of our global forcing and the lowered northern Tibetan Plateau in the regional model. The summer monsoon circulation is generally weakened in our regional Tortonian run compared to today. However, the changes of summer monsoon precipitation exhibit major regional differences. The precipitation decreases in N-China and N-India, but increases in S-China, the western coast and the southern tip of India. This can be attributed to the combined effect of both the regional topographical changes and the other forcings related to our global model. The spread of the dry summer conditions over N-China and NW-India further implies that the monsoonal climate may not be fully established over these regions in the Tortonain. Compared with the global model, the high resolution regional model highlights the spatial differences of the Asian monsoon climate in the Tortonian, and better characterizes the convective activity and its response to topographical changes. It therefore provides a useful and compared to global models complementary tool to improve our understanding of the Asian

  12. Regional climate model experiments to investigate the Asian monsoon in the Late Miocene

    Directory of Open Access Journals (Sweden)

    H. Tang

    2011-08-01

    Full Text Available The Late Miocene (11.6–5.3 Ma is a crucial period in the history of the Asian monsoon. Significant changes in the Asian climate regime have been documented for this period, which saw the formation of the modern Asian monsoon system. However, the spatiotemporal structure of these changes is still ambiguous, and the associated mechanisms are debated. Here, we present a simulation of the average state of the Asian monsoon climate for the Tortonian (11–7 Ma using the regional climate model CCLM3.2. We employ relatively high spatial resolution (1° × 1° and adapt the physical boundary conditions such as topography, land-sea distribution and vegetation in the regional model to represent the Late Miocene. As climatological forcing, the output of a Tortonian run with a fully-coupled atmosphere-ocean general circulation model is used. Our regional Tortonian run shows a stronger-than-present East Asian winter monsoon wind as a result of the enhanced mid-latitude westerly wind of our global forcing and the lowered present-day northern Tibetan Plateau in the regional model. The summer monsoon circulation is generally weakened in our regional Tortonian run compared to today. However, the changes of summer monsoon precipitation exhibit major regional differences. Precipitation decreases in northern China and northern India, but increases in southern China, the western coast and the southern tip of India. This can be attributed to the changes in both the regional topography (e.g. the lower northern Tibetan Plateau and the global climate conditions (e.g. the higher sea surface temperature. The spread of dry summer conditions over northern China and northern Pakistan in our Tortonian run further implies that the monsoonal climate may not have been fully established in these regions in the Tortonian. Compared with the global model, the high resolution regional model highlights the spatial differences of the Asian monsoon climate in the Tortonian, and better

  13. Detecting human impacts on the flora, fauna, and summer monsoon of Pleistocene Australia

    Directory of Open Access Journals (Sweden)

    G. H. Miller

    2007-08-01

    Full Text Available The moisture balance across northern and central Australia is dominated by changes in the strength of the Australian Summer Monsoon. Lake-level records that record changes in monsoon strength on orbital timescales are most consistent with a Northern Hemisphere insolation control on monsoon strength, a result consistent with recent modeling studies. A weak Holocene monsoon relative to monsoon strength 65–60 ka, despite stronger forcing, suggests a changed monsoon regime after 60 ka. Shortly after 60 ka humans colonized Australia and all of Australia's largest mammals became extinct. Between 60 and 40 ka Australian climate was similar to present and not changing rapidly. Consequently, attention has turned toward plausible human mechanisms for the extinction, with proponents for over-hunting, ecosystem change, and introduced disease. To differentiate between these options we utilize isotopic tracers of diet preserved in eggshells of two large, flightless birds to track the status of ecosystems before and after human colonization. More than 800 dated eggshells of the Australian emu (Dromaius novaehollandiae, an opportunistic, dominantly herbivorous feeder, provide a 140-kyr dietary reconstruction that reveals unprecedented reduction in the bird's food resources about 50 ka, coeval in three distant regions. These data suggest a tree/shrub savannah with occasionally rich grasslands was converted abruptly to the modern desert scrub. The diet of the heavier, extinct Genyornis newtoni, derived from >550 dated eggshells, was more restricted than in co-existing Dromaius, implying a more specialized feeding strategy. We suggest that generalist feeders, such as Dromaius, were able to adapt to a changed vegetation regime, whereas more specialized feeders, such as Genyornis, became extinct. We speculate that ecosystem collapse across arid and semi-arid zones was a consequence of systematic burning by early humans

  14. Detecting human impacts on the flora, fauna, and summer monsoon of Pleistocene Australia

    Science.gov (United States)

    Miller, G. H.; Magee, J. W.; Fogel, M. L.; Gagan, M. K.

    2007-08-01

    The moisture balance across northern and central Australia is dominated by changes in the strength of the Australian Summer Monsoon. Lake-level records that record changes in monsoon strength on orbital timescales are most consistent with a Northern Hemisphere insolation control on monsoon strength, a result consistent with recent modeling studies. A weak Holocene monsoon relative to monsoon strength 65-60 ka, despite stronger forcing, suggests a changed monsoon regime after 60 ka. Shortly after 60 ka humans colonized Australia and all of Australia's largest mammals became extinct. Between 60 and 40 ka Australian climate was similar to present and not changing rapidly. Consequently, attention has turned toward plausible human mechanisms for the extinction, with proponents for over-hunting, ecosystem change, and introduced disease. To differentiate between these options we utilize isotopic tracers of diet preserved in eggshells of two large, flightless birds to track the status of ecosystems before and after human colonization. More than 800 dated eggshells of the Australian emu (Dromaius novaehollandiae), an opportunistic, dominantly herbivorous feeder, provide a 140-kyr dietary reconstruction that reveals unprecedented reduction in the bird's food resources about 50 ka, coeval in three distant regions. These data suggest a tree/shrub savannah with occasionally rich grasslands was converted abruptly to the modern desert scrub. The diet of the heavier, extinct Genyornis newtoni, derived from >550 dated eggshells, was more restricted than in co-existing Dromaius, implying a more specialized feeding strategy. We suggest that generalist feeders, such as Dromaius, were able to adapt to a changed vegetation regime, whereas more specialized feeders, such as Genyornis, became extinct. We speculate that ecosystem collapse across arid and semi-arid zones was a consequence of systematic burning by early humans. We also suggest that altered climate feedbacks linked to changes

  15. Impacts of Urbanization on Indian Summer Monsoon Rainfall

    Science.gov (United States)

    Shastri, H. K.; Ghosh, S.; Karmakar, S.

    2013-12-01

    Rapid urbanisation all around the world is a matter of concern to the scientific community. The fast growing urban areas carries out huge anthropogenic activities that burdens natural environment and its resources like air-water quality and space, thus have different climatology to their rural surroundings. World Urbanization Prospects 2005 annual report described 20th century as witnessing a rapid urbanization of the world's population. Though urbanization is a worldwide phenomenon, it is especially prevalent in India, where urban areas have experienced an unprecedented rate of growth with level of urbanization increased from 17.23 % to 31.16% in year 1951 to 2011and the number of cities with population more than one million has grown from 5 to 53 over the same time. We take up an observational study to understand influence of urbanisation on mesoscale circulations and resulting convection, thus nature of precipitation around urban areas. The spatially distributed analysis of gridded daily precipitation data over the country is carried out to identify nature of trends in selected statistics of Indian summer monsoon precipitation and examine its association with urban land cover to have an impact on precipitation statistics. We evaluate explicit changes around urban land use in context of 40 large Indian urban areas. Further we assess local-urban climatic signals in the point level rainfall observations with model based analysis of two nearby locations under similar climatic conditions but differing largely in terms of urbanisation. The results of gridded data analysis indicate an overall tendency towards decrease in mean precipitation however, rainfall activities are enhanced around urban areas across different climate zones of the country. Though trends observed in selected climatic parameters revealed great degree of spatial inter variability in selected precipitation statistics over the country, they accounts a greater degree of inclination for occurrence under

  16. Baseline predictability of daily east Asian summer monsoon circulation indices

    Science.gov (United States)

    Ai, Shucong; Chen, Quanliang; Li, Jianping; Ding, Ruiqiang; Zhong, Quanjia

    2017-05-01

    The nonlinear local Lyapunov exponent (NLLE) method is adopted to quantitatively determine the predictability limit of East Asian summer monsoon (EASM) intensity indices on a synoptic timescale. The predictability limit of EASM indices varies widely according to the definitions of indices. EASM indices defined by zonal shear have a limit of around 7 days, which is higher than the predictability limit of EASM indices defined by sea level pressure (SLP) difference and meridional wind shear (about 5 days). The initial error of EASM indices defined by SLP difference and meridional wind shear shows a faster growth than indices defined by zonal wind shear. Furthermore, the indices defined by zonal wind shear appear to fluctuate at lower frequencies, whereas the indices defined by SLP difference and meridional wind shear generally fluctuate at higher frequencies. This result may explain why the daily variability of the EASM indices defined by zonal wind shear tends be more predictable than those defined by SLP difference and meridional wind shear. Analysis of the temporal correlation coefficient (TCC) skill for EASM indices obtained from observations and from NCEP's Global Ensemble Forecasting System (GEFS) historical weather forecast dataset shows that GEFS has a higher forecast skill for the EASM indices defined by zonal wind shear than for indices defined by SLP difference and meridional wind shear. The predictability limit estimated by the NLLE method is shorter than that in GEFS. In addition, the June-September average TCC skill for different daily EASM indices shows significant interannual variations from 1985 to 2015 in GEFS. However, the TCC for different types of EASM indices does not show coherent interannual fluctuations.

  17. Validation of Seasonal Forecast of Indian Summer Monsoon Rainfall

    Science.gov (United States)

    Das, Sukanta Kumar; Deb, Sanjib Kumar; Kishtawal, C. M.; Pal, Pradip Kumar

    2015-06-01

    The experimental seasonal forecast of Indian summer monsoon (ISM) rainfall during June through September using Community Atmosphere Model (CAM) version 3 has been carried out at the Space Applications Centre Ahmedabad since 2009. The forecasts, based on a number of ensemble members (ten minimum) of CAM, are generated in several phases and updated on regular basis. On completion of 5 years of experimental seasonal forecasts in operational mode, it is required that the overall validation or correctness of the forecast system is quantified and that the scope is assessed for further improvements of the forecast over time, if any. The ensemble model climatology generated by a set of 20 identical CAM simulations is considered as the model control simulation. The performance of the forecast has been evaluated by assuming the control simulation as the model reference. The forecast improvement factor shows positive improvements, with higher values for the recent forecasted years as compared to the control experiment over the Indian landmass. The Taylor diagram representation of the Pearson correlation coefficient (PCC), standard deviation and centered root mean square difference has been used to demonstrate the best PCC, in the order of 0.74-0.79, recorded for the seasonal forecast made during 2013. Further, the bias score of different phases of experiment revealed the fact that the ISM rainfall forecast is affected by overestimation in predicting the low rain-rate (less than 7 mm/day), but by underestimation in the medium and high rain-rate (higher than 11 mm/day). Overall, the analysis shows significant improvement of the ISM forecast over the last 5 years, viz. 2009-2013, due to several important modifications that have been implemented in the forecast system. The validation exercise has also pointed out a number of shortcomings in the forecast system; these will be addressed in the upcoming years of experiments to improve the quality of the ISM prediction.

  18. Summer monsoon onset over Kerala: New definition and prediction

    Indian Academy of Sciences (India)

    D S Pai; Rajeevan M Nair

    2009-04-01

    The summer monsoon onset over Kerala (MOK)marks the beginning of the rainy season for the country.Associated with the MOK,significant transitions of large scale atmospheric and oceanic circulation patterns are observed over the Asia –Pacific region.In this study,a new method for the objective identification of MOK,based on large scale circulation features and rainfall over Kerala,is discussed.Further,a set of empirical models based on the principal component regression (PCR)technique was developed for the prediction of the date of MOK by keeping in mind the IMD ’s operational forecasting service requirements.Predictors for the models were derived using correlation analysis from the thermal,convective and circulation patterns.Only five predictors pertaining to the second half of April were used in the first model (Model-1)so that the prediction of MOK can be prepared by the end of April itself.The second model (Model-2)used four additional predictors pertaining up to the first half of May along with two predictors used in the Model-1 for update prediction at the end of the first half of May.To develop each of the PCR models, Principal Components Analysis (PCA)of the respective predictor data was carried out followed by regression analysis of first two principal components (PCs)with the date of MOK.Both these models showed good skill in predicting the date of MOK during the independent test period of 1997 –2007.The root mean square error (RMSE)of the predictions from both the models during the independent test period was about four days which was nearly half the RMSE of the predictions based on climatology.

  19. Titan's Methane Monsoon : Evidence of Catastrophic Hydrology from Cassini RADAR

    Science.gov (United States)

    Lorenz, R. D.; Cassini RADAR Team

    2005-08-01

    Radar imagery from the October 2004 TA encounter (1) indicated a number of bright, narrow, sinuous features that might be cracks or canyons - two of these appeared to connect to the apices of triangular radar-bright striated features that may be alluvial fans rendered radar-bright by wavelength-scale (>2cm) cobbles or boulders. The findings of the Huygens probe seem to support the idea of pluvial and fluvial activity on Titan. The February 2005 T3 encounter provided radar imagery of another region with two areas of dendritic networks of bright sinuous features, one being a remarkable collection of apparently braided channels draining into a radar-bright plain. We present analysis of the topological properties (branching ratios, tortuosity etc.) of these networks and channels, supporting an origin via erosion by heavy rainfall on a relatively uncohesive terrain, and present some terrestrial analogs. We consider these observations in the context of a paradigm for Titan (2,3,4) reminiscent of the hydrology of the US desert southwest, where long droughts are punctuated by catastrophic downpours. Even though the annual average rainfall is modest (energetically limited to 1cm/yr (3)) pluvial/fluvial erosion is a major agent of geomorphological change. Although perhaps climatologically inaccurate, the term ``Methane Monsoon" coined by Arthur C. Clarke (5) is an evocative name for the paradigm. References (1) C. Elachi et al., Science, 308, 970-974, 2005. (2) R. D. Lorenz, Science, 290, 467-468, 2000. (3) R. D. Lorenz and J. Mitton, Lifting Titan's Veil, Cambridge University Press, 2002. (4) R. D. Lorenz et al., Geophysical Review Letters, 32, L01201, 2005 (5). A. C. Clarke, Imperial Earth, , Victor Gollancz, London, 1975

  20. Investigation of dominant modes of monsoon ISO in the northwest and eastern Himalayan region

    Science.gov (United States)

    Mukherjee, Sandipan; Ballav, Srabanti; Soni, Sandeep; Kumar, Kireet; Kumar De, Utpal

    2016-08-01

    This study investigates the altitudinal variation of dominant modes of summer monsoon intra-seasonal oscillation (ISO) over the Northwest (NWH) and Eastern Himalayan (EH) region using (i) spatially scattered 133 number of station rainfall observations and (ii) latitudinal transect-wise (LT) rainfall variation, obtained from an observed interpolated gridded rainfall data for the period 1995-2004. The altitudinal variation of dominant modes of monsoon ISO were investigated by exploring the strong and weak phases of the principal components of 10-90 days bandpass rainfall data of June to September with respect to location specific station height. Investigation of frequency of days for light and moderate rainfall along with the occurrence of total seasonal rainy days has revealed existence of a rainfall maximum around 2100 m height for the NWH region. Similarly, the total seasonal rainy days of EH region was found to have maxima between 1100 and 1400 m height. Analyses of the spatially scattered station rainfall observation for the NWH region showed that the strong periods of ISO modes exist around 747.9 (±131.7) m and 2227.2 (±100.2) m heights. Over the EH region, the dominant modes of the monsoon ISO were found to be centred around 1200 m. Significant alterations of strong and weak phases of monsoon ISO as a response to altitudinal variation in the mountain surface were observed when latitudinal transect-wise variation of monsoon ISO modes were investigated.

  1. RELATIONSHIPS BETWEEN AUTUMN INDIAN OCEAN DIPOLE MODE AND THE STRENGTH OF SCS SUMMER MONSOON

    Institute of Scientific and Technical Information of China (English)

    LI Dong-hui; ZHANG Gui; ZHU Yi-min; TAN Yan-ke; WANG Xue-zhong

    2007-01-01

    Based on 1948 - 2004 monthly Reynolds Sea Surface Temperature (SST) and NCEP/NCAR atmospheric reanalysis data, the relationships between autumn Indian Ocean Dipole Mode (IODM) and the strength of South China Sea (SCS) Summer Monsoon are investigated through the EOF and smooth correlation methods. The results are as the following. (1) There are two dominant modes of autumn SSTA over the tropical Indian Ocean. They are the uniformly signed basin-wide mode (USBM) and Indian Ocean dipole mode (IODM), respectively. The SSTA associated with USBM are prevailing decadal to interdecadal variability characterized by a unanimous pattern, while the IODM mainly represents interannual variability of SSTA. (2) When positive (negative) IODM exists over the tropical Indian Ocean during the preceding fall,the SCS summer monsoon will be weak (strong). The negative correlation between the interannual variability of IODM and that of SCS summer monsoon is significant during the warm phase of long-term trend but insignificant during the cool phase. (3) When the SCS summer monsoon is strong (weak), the IODM will be in its positive (negative) phase during the following fall season. The positive correlation between the interannual variability of SCS summer monsoon and that of IODM is significant during both the warm and cool phase of the long-term trend, but insignificant during the transition between the two phases.

  2. Entropy analysis of stable isotopes in precipitation: tracing the monsoon systems in China.

    Science.gov (United States)

    Wang, Tao; Chen, Jiansheng; Li, Ling

    2016-08-10

    Due to the complexity of monsoon systems and random behaviors of isotope tracers, conventional methods are not adequate for uncovering detailed information about monsoon activities from typically limited precipitation isotope data. We developed a new approach based on the entropy theory to analyze such data with a focus on the monsoon systems in China, dealing with the complexity of these systems and data deficiency. Using precipitation isotope data from 42 selected stations in and around China within the GNIP network, we computed entropies associated with D and (18)O. These entropies were found to relate linearly to each other with a proportionality factor close to unity. The spatial variations of the D and (18)O entropy in the study area revealed the origins, extents and pathways of the Chinese monsoon systems, as well as their interactions. While further investigation is needed at a greater (global) scale, this study has demonstrated how the entropy theory enables an in-depth analysis of precipitation isotope data to trace the pathway and determine the range of a monsoon system.

  3. Seasonal forecasting of Bangladesh summer monsoon rainfall using simple multiple regression model

    Indian Academy of Sciences (India)

    Md Mizanur Rahman; M Rafiuddin; Md Mahbub Alam

    2013-04-01

    In this paper, the development of a statistical forecasting method for summer monsoon rainfall over Bangladesh is described. Predictors for Bangladesh summer monsoon (June–September) rainfall were identified from the large scale ocean–atmospheric circulation variables (i.e., sea-surface temperature, surface air temperature and sea level pressure). The predictors exhibited a significant relationship with Bangladesh summer monsoon rainfall during the period 1961–2007. After carrying out a detailed analysis of various global climate datasets; three predictors were selected. The model performance was evaluated during the period 1977–2007. The model showed better performance in their hindcast seasonal monsoon rainfall over Bangladesh. The RMSE and Heidke skill score for 31 years was 8.13 and 0.37, respectively, and the correlation between the predicted and observed rainfall was 0.74. The BIAS of the forecasts (% of long period average, LPA) was −0.85 and Hit score was 58%. The experimental forecasts for the year 2008 summer monsoon rainfall based on the model were also found to be in good agreement with the observation.

  4. Prediction of a thermodynamic wave train from the monsoon to the Arctic following extreme rainfall events

    Science.gov (United States)

    Krishnamurti, T. N.; Kumar, Vinay

    2016-06-01

    This study addresses numerical prediction of atmospheric wave trains that provide a monsoonal link to the Arctic ice melt. The monsoonal link is one of several ways that heat is conveyed to the Arctic region. This study follows a detailed observational study on thermodynamic wave trains that are initiated by extreme rain events of the northern summer south Asian monsoon. These wave trains carry large values of heat content anomalies, heat transports and convergence of flux of heat. These features seem to be important candidates for the rapid melt scenario. This present study addresses numerical simulation of the extreme rains, over India and Pakistan, and the generation of thermodynamic wave trains, simulations of large heat content anomalies, heat transports along pathways and heat flux convergences, potential vorticity and the diabatic generation of potential vorticity. We compare model based simulation of many features such as precipitation, divergence and the divergent wind with those evaluated from the reanalysis fields. We have also examined the snow and ice cover data sets during and after these events. This modeling study supports our recent observational findings on the monsoonal link to the rapid Arctic ice melt of the Canadian Arctic. This numerical modeling suggests ways to interpret some recent episodes of rapid ice melts that may require a well-coordinated field experiment among atmosphere, ocean, ice and snow cover scientists. Such a well-coordinated study would sharpen our understanding of this one component of the ice melt, i.e. the monsoonal link, which appears to be fairly robust.

  5. Differences and links between the East Asian and South Asian summer monsoon systems: Characteristics and Variability

    Science.gov (United States)

    Huang, Ronghui; Liu, Yong; Du, Zhencai; Chen, Jilong; Huangfu, Jingliang

    2017-10-01

    This paper analyzes the differences in the characteristics and spatio-temporal variabilities of summertime rainfall and water vapor transport between the East Asian summer monsoon (EASM) and South Asian summer monsoon (SASM) systems. The results show obvious differences in summertime rainfall characteristics between these two monsoon systems. The summertime rainfall cloud systems of the EASM show a mixed stratiform and cumulus cloud system, while cumulus cloud dominates the SASM. These differences may be caused by differences in the vertical shear of zonal and meridional circulations and the convergence of water vapor transport fluxes. Moreover, the leading modes of the two systems' summertime rainfall anomalies also differ in terms of their spatiotemporal features on the interannual and interdecadal timescales. Nevertheless, several close links with respect to the spatiotemporal variabilities of summertime rainfall and water vapor transport exist between the two monsoon systems. The first modes of summertime rainfall in the SASM and EASM regions reveal a significant negative correlation on the interannual and the interdecadal timescales. This close relationship may be linked by a meridional teleconnection in the regressed summertime rainfall anomalies from India to North China through the southeastern part over the Tibetan Plateau, which we refer to as the South Asia/East Asia teleconnection pattern of Asian summer monsoon rainfall. The authors wish to dedicate this paper to Prof. Duzheng YE, and commemorate his 100th anniversary and his great contributions to the development of atmospheric dynamics.

  6. Precipitation top heights of orographic heavy rainfall in the Asian monsoon regions

    Science.gov (United States)

    Shige, Shoichi; Kummerow, Christian

    2016-04-01

    In contrast to the dominant view that heavy rainfall results from deep clouds, the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) frequently observed heavy, but shallow orographic rainfall over coastal mountain ranges of the Asian monsoon regions. The low-level horizontal winds, leading to topographic forced upward motion on the windward slopes, are dynamically important for its occurrence. This paper focuses on the thermodynamic character of the atmospheric environment associated with shallow orographic heavy rainfall. The precipitation-top heights of orographic heavy rainfall generally decrease with low- and mid-level relative humidity especially for coastal mesoscale mountain ranges during summer monsoon. This differs from what has been observed for convection over the tropical ocean in previous studies, but is consistent with abundant shallow convection during the moist summer monsoon season. In contrast, the precipitation-top heights over Annam Cordillera during the transition phase from boreal summer to winter monsoon seasons, facing the prevailing northeasterly, increase with low-level and mid-level relative humidity, demonstrating that convection depth is not a simple function of humidity. The precipitation-top heights of orographic heavy rainfall decrease with the low-level stability for all regions considered in this study as well as Annam Cordillera during the transition phase from boreal summer to winter monsoon seasons. Therefore, low-level static stability, which inhibits cloud growth and promotes cloud detrainment, is inferred to be an equally important parameter in determining the precipitation-top heights.

  7. Applications of monsoon research: Opportunities to inform decisionmaking and reduce regional vulnerability

    Science.gov (United States)

    Ray, A. J.; Garfin, G. M.; Wilder, M.; Lenart, M.; Vásquez-León, M.; Comrie, A. C.

    2007-05-01

    This presentation will describe ongoing efforts to understand interactions between the North American Monsoon and society, in order to develop applications for monsoon research in a highly complex, multicultural and binational region. The North American Monsoon is an annual precipitation regime that begins in early June in Mexico and progresses northward to the southwestern United States. The region includes stakeholders in large urban complexes, productive agricultural areas, and sparsely populated arid and semi-arid ecosystems. The political, cultural, and socioeconomic divisions between the U.S. and Mexico create a broad range of sensitivities to climate variability as well as capacities to use forecasts and other information to cope with climate. We will highlight methodologies to link climate science with society and analyze opportunities for monsoon science to benefit society in four sectors: natural hazards management, agriculture, public health, and water management. We present a synthesized list of stakeholder needs and a calendar of decisions to help scientists link user needs to potential forecasts and products. To ensure usability of forecasts and other research products, we recommend iterative scientist-stakeholder interactions, through integrated assessments. These knowledge- exchange interactions can improve the capacity for stakeholders to use forecasts thoughtfully and inform the development of research, and for the research community to obtain feedback on climate-related products and receive insights to guide research direction. We expect that integrated assessments can capitalize on the opportunities for monsoon science to inform decisionmaking, in the best instances, reduce regional climate vulnerabilities and enhance regional sustainability

  8. Mechanism of ENSO influence on the South Asian monsoon rainfall in global model simulations

    Science.gov (United States)

    Joshi, Sneh; Kar, Sarat C.

    2017-02-01

    Coupled ocean atmosphere global climate models are increasingly being used for seasonal scale simulation of the South Asian monsoon. In these models, sea surface temperatures (SSTs) evolve as coupled air-sea interaction process. However, sensitivity experiments with various SST forcing can only be done in an atmosphere-only model. In this study, the Global Forecast System (GFS) model at T126 horizontal resolution has been used to examine the mechanism of El Niño-Southern Oscillation (ENSO) forcing on the monsoon circulation and rainfall. The model has been integrated (ensemble) with observed, climatological and ENSO SST forcing to document the mechanism on how the South Asian monsoon responds to basin-wide SST variations in the Indian and Pacific Oceans. The model simulations indicate that the internal variability gets modulated by the SSTs with warming in the Pacific enhancing the ensemble spread over the monsoon region as compared to cooling conditions. Anomalous easterly wind anomalies cover the Indian region both at 850 and 200 hPa levels during El Niño years. The locations and intensity of Walker and Hadley circulations are altered due to ENSO SST forcing. These lead to reduction of monsoon rainfall over most parts of India during El Niño events compared to La Niña conditions. However, internally generated variability is a major source of uncertainty in the model-simulated climate.

  9. Prediction of a thermodynamic wave train from the monsoon to the Arctic following extreme rainfall events

    Science.gov (United States)

    Krishnamurti, T. N.; Kumar, Vinay

    2017-04-01

    This study addresses numerical prediction of atmospheric wave trains that provide a monsoonal link to the Arctic ice melt. The monsoonal link is one of several ways that heat is conveyed to the Arctic region. This study follows a detailed observational study on thermodynamic wave trains that are initiated by extreme rain events of the northern summer south Asian monsoon. These wave trains carry large values of heat content anomalies, heat transports and convergence of flux of heat. These features seem to be important candidates for the rapid melt scenario. This present study addresses numerical simulation of the extreme rains, over India and Pakistan, and the generation of thermodynamic wave trains, simulations of large heat content anomalies, heat transports along pathways and heat flux convergences, potential vorticity and the diabatic generation of potential vorticity. We compare model based simulation of many features such as precipitation, divergence and the divergent wind with those evaluated from the reanalysis fields. We have also examined the snow and ice cover data sets during and after these events. This modeling study supports our recent observational findings on the monsoonal link to the rapid Arctic ice melt of the Canadian Arctic. This numerical modeling suggests ways to interpret some recent episodes of rapid ice melts that may require a well-coordinated field experiment among atmosphere, ocean, ice and snow cover scientists. Such a well-coordinated study would sharpen our understanding of this one component of the ice melt, i.e. the monsoonal link, which appears to be fairly robust.

  10. Deep learning for predicting the monsoon over the homogeneous regions of India

    Science.gov (United States)

    Saha, Moumita; Mitra, Pabitra; Nanjundiah, Ravi S.

    2017-06-01

    Indian monsoon varies in its nature over the geographical regions. Predicting the rainfall not just at the national level, but at the regional level is an important task. In this article, we used a deep neural network, namely, the stacked autoencoder to automatically identify climatic factors that are capable of predicting the rainfall over the homogeneous regions of India. An ensemble regression tree model is used for monsoon prediction using the identified climatic predictors. The proposed model provides forecast of the monsoon at a long lead time which supports the government to implement appropriate policies for the economic growth of the country. The monsoon of the central, north-east, north-west, and south-peninsular India regions are predicted with errors of 4.1%, 5.1%, 5.5%, and 6.4%, respectively. The identified predictors show high skill in predicting the regional monsoon having high variability. The proposed model is observed to be competitive with the state-of-the-art prediction models.

  11. COMPOSITE ANALYSIS OF SUMMER MONSOON ONSET PROCESS OVER SOUTH CHINA SEA

    Institute of Scientific and Technical Information of China (English)

    徐海明; 何金海; 周兵

    2001-01-01

    Based on the method of composite analysis, the onset process and preceding signs of summer monsoon over the South China Sea (SCS) is investigated. The result indicates that convection activities appear first over the Indo-China Peninsula prior to the onset of the monsoon, then around the Philippines just at the point of onset, implying that the convection activities around the Philippines serve as one of the reasons leading to the SCS monsoon onset. Before the SCS monsoon onset, the equatorial westerly over the Indian Ocean (75°E ~ 95°E ) experiences noticeable enhancement and plays an important role on the SCS monsoon onset. It propagates eastward rapidly and causes the establishment and strengthening of equatorial westerly in the southern SCS, on the one hand, it results in the migration southward of the westerly on south side of the south-China stationary front by means of shift northeastward of the westerly and convection over the Bay of Bengal, on the other. Further study also shows that the intensification of equatorial westerly in the Indian Ocean (75°E ~ 95°E) and the southern SCS is closely related to the reinforcement of the Southern-Hemisphere Mascarene high and Australian high, and cross-equatorial flow northward around Somali, at 85°E and 105°E, respectively.

  12. Competing influences of greenhouse warming and aerosols on Asian summer monsoon circulation and rainfall

    Science.gov (United States)

    Lau, William Ka-Ming; Kim, Kyu-Myong

    2017-05-01

    In this paper, we have compared and contrasted competing influences of greenhouse gases (GHG) warming and aerosol forcing on Asian summer monsoon circulation and rainfall based on CMIP5 historical simulations. Under GHG-only forcing, the land warms much faster than the ocean, magnifying the pre-industrial climatological land-ocean thermal contrast and hemispheric asymmetry, i.e., warmer northern than southern hemisphere. A steady increasing warm-ocean-warmer-land (WOWL) trend has been in effect since the 1950's substantially increasing moisture transport from adjacent oceans, and enhancing rainfall over the Asian monsoon regions. However, under GHG warming, increased atmospheric stability due to strong reduction in mid-tropospheric and near surface relative humidity coupled to an expanding subsidence areas, associated with the Deep Tropical Squeeze (DTS, Lau and Kim, 2015b) strongly suppress monsoon convection and rainfall over subtropical and extratropical land, leading to a weakening of the Asian monsoon meridional circulation. Increased anthropogenic aerosol emission strongly masks WOWL, by over 60% over the northern hemisphere, negating to a large extent the rainfall increase due to GHG warming, and leading to a further weakening of the monsoon circulation, through increasing atmospheric stability, most likely associated with aerosol solar dimming and semi-direct effects. Overall, we find that GHG exerts stronger positive rainfall sensitivity, but less negative circulation sensitivity in SASM compared to EASM. In contrast, aerosols exert stronger negative impacts on rainfall, but less negative impacts on circulation in EASM compared to SASM.

  13. Earth as diode: monsoon source of the orbital ~100 ka climate cycle

    Directory of Open Access Journals (Sweden)

    R. Y. Anderson

    2010-08-01

    Full Text Available A potential source for Earth's enigmatic ~100 ka climate cycle, which is found in many ancient geological records at low latitudes and also in the pacing of glaciation during the late Pleistocene, is traced to a climatic rectifying process inherent in the monsoon. Seasonal information needed to identify the rectifying mechanism is preserved within varves of a continuous, 200 ka recording of annual maximum surface temperature (Tmax from the equator of Western Pangea. Specific seasonal reactions recorded in varves show how the monsoon reacted to seasonal differences in insolation at equinox to produce a 11.7 ka semi-precession cycle in Tmax. At solstice, anti-phasing of insolation in the Northern and Southern Hemispheres, intensified and focused by a highly asymmetric Pangea relative to the equator, produced a strong equatorial maritime monsoon that performed a nonlinear rectifying function similar to that of a simple rectifying diode. Expressed in the resulting varve series are substantial cycles in Tmax of 100 ka, 23.4 ka, and 11.7 ka. Importantly, any external or internal forcing of the tropical (monsoon climate system at higher-than-orbital frequencies (e.g. solar, ENSO should also be amplified at Milankovitch frequencies by the monsoon.

  14. An Index Measuring the Interannual Variation of the East Asian Summer Monsoon--The EAP Index

    Institute of Scientific and Technical Information of China (English)

    黄刚

    2004-01-01

    Based on the EAP (East Asia/Pacific) teleconnection in the summer circulation anomalies over the Northern Hemisphere,an index measuring the strength of the East Asian summer monsoon,i.e.,the socalled EAP index,is defined in this paper.From the analyses of observed data,it is clearly shown that the EAP index defined in this study can well describe the interannual variability of summer rainfall and surfaceair temperature in East Asia,especially in the Yangtze River valley and the Hualhe River valley,Korea,and Japan.Moreover,this index can also reflect the interannual variability of the East Asian summer monsoon system including the monsoon horizontal circulation and the vertical-merldional circulation cell over East Asia.From the composite analyses of climate and monsoon circulation anomalies for high EAP index and for low EAP index,respectively,it is well demonstrated that the EAP index proposed in this study can well measure the strength of the East Asian summer monsoon.

  15. Contrasting influences of aerosols on cloud properties during deficient and abundant monsoon years.

    Science.gov (United States)

    Patil, Nitin; Dave, Prashant; Venkataraman, Chandra

    2017-03-24

    Direct aerosol radiative forcing facilitates the onset of Indian monsoon rainfall, based on synoptic scale fast responses acting over timescales of days to a month. Here, we examine relationships between aerosols and coincident clouds over the Indian subcontinent, using observational data from 2000 to 2009, from the core monsoon region. Season mean and daily timescales were considered. The correlation analyses of cloud properties with aerosol optical depth revealed that deficient monsoon years were characterized by more frequent and larger decreases in cloud drop size and ice water path, but increases in cloud top pressure, with increases in aerosol abundance. The opposite was observed during abundant monsoon years. The correlations of greater aerosol abundance, with smaller cloud drop size, lower evidence of ice processes and shallower cloud height, during deficient rainfall years, imply cloud inhibition; while those with larger cloud drop size, greater ice processes and a greater cloud vertical extent, during abundant rainfall years, suggest cloud invigoration. The study establishes that continental aerosols over India alter cloud properties in diametrically opposite ways during contrasting monsoon years. The mechanisms underlying these effects need further analysis.

  16. Consistent increase in Indian monsoon rainfall and its variability across CMIP-5 models

    Directory of Open Access Journals (Sweden)

    A. Menon

    2013-01-01

    Full Text Available The possibility of an impact of global warming on the Indian monsoon is of critical importance for the large population of this region. Future projections within the Coupled Model Intercomparison Project Phase 3 (CMIP-3 showed a wide range of trends with varying magnitude and sign across models. Here the Indian summer monsoon rainfall is evaluated in 20 CMIP-5 models for the period 1850 to 2100. In the new generation of climate models a consistent increase in seasonal mean rainfall during the summer monsoon periods arises. All models simulate stronger seasonal mean rainfall in the future compared to the historic period under the strongest warming scenario RCP-8.5. Increase in seasonal mean rainfall is the largest for the RCP-8.5 scenario compared to other RCPs. The interannual variability of the Indian monsoon rainfall also shows a consistent positive trend under unabated global warming. Since both the long-term increase in monsoon rainfall as well as the increase in interannual variability in the future is robust across a wide range of models, some confidence can be attributed to these projected trends.

  17. Role of west Asian surface pressure in summer monsoon onset over central India

    Science.gov (United States)

    Chakraborty, Arindam; Agrawal, Shubhi

    2017-07-01

    Using rain-gauge measurements and reanalysis data sets for 1948-2015, we propose a mechanism that controls the interannual variation of summer monsoon onset over central India. In May, about a month before the onset, the low level jet over the Arabian Sea is about 40% stronger and about 2.5 degrees northward during years of early onset as compared to years of late onset. A stronger and northward shifted low level jet carries about 50% more moisture in early onset years, which increases low level moist static energy over central India in the pre-monsoon season. The increase in low level moist static energy decreases the stability of the atmosphere and makes it conducive for convection. The strength and position of the low level jet are determined by surface pressure gradient between western Asia and the west-equatorial Indian Ocean. Thus, an anomalous surface pressure low over western Asia in the pre-monsoon season increases this gradient and strengthens the jet. Moreover, a stronger low level jet increases the meridional shear of zonal wind and supports the formation of an onset vortex in a stronger baroclinic atmosphere. These developments are favourable for an early onset of the monsoon over the central Indian region. Our study postulates a new physical mechanism for the interannual variation of onset over central India, the core of the Indian monsoon region and relevant to Indian agriculture, and could be tested for real-time prediction.

  18. The role of potential vorticity anomalies in the Somali Jet on Indian Summer Monsoon Intraseasonal Variability

    Science.gov (United States)

    Rai, P.; Joshi, M.; Dimri, A. P.; Turner, A. G.

    2017-08-01

    The climate of the Indian subcontinent is dominated by rainfall arising from the Indian summer monsoon (ISM) during June to September. Intraseasonal variability during the monsoon is characterized by periods of heavy rainfall interspersed by drier periods, known as active and break events respectively. Understanding and predicting such events is of vital importance for forecasting human impacts such as water resources. The Somali Jet is a key regional feature of the monsoon circulation. In the present study, we find that the spatial structure of Somali Jet potential vorticity (PV) anomalies varies considerably during active and break periods. Analysis of these anomalies shows a mechanism whereby sea surface temperature (SST) anomalies propagate north/northwestwards through the Arabian Sea, caused by a positive feedback loop joining anomalies in SST, convection, modification of PV by diabatic heating and mixing in the atmospheric boundary layer, wind-stress curl, and ocean upwelling processes. The feedback mechanism is consistent with observed variability in the coupled ocean-atmosphere system on timescales of approximately 20 days. This research suggests that better understanding and prediction of monsoon intraseasonal variability in the South Asian monsoon may be gained by analysis of the day-to-day dynamical evolution of PV in the Somali Jet.

  19. Astronomical and Hydrological Perspective of Mountain Impacts on the Asian Summer Monsoon.

    Science.gov (United States)

    He, Bian; Wu, Guoxiong; Liu, Yimin; Bao, Qing

    2015-12-01

    The Asian summer monsoon has great socioeconomic impacts. Understanding how the huge Tibetan and Iranian Plateaus affect the Asian summer monsoon is of great scientific value and has far-reaching significance for sustainable global development. One hypothesis considers the plateaus to be a shield for monsoon development in India by blocking cold-dry northerly intrusion into the tropics. Based on astronomical radiation analysis and numerical modeling, here we show that in winter the plateaus cannot block such a northerly intrusion; while in summer the daily solar radiation at the top of the atmosphere and at the surface, and the surface potential temperature to the north of the Tibetan Plateau, are higher than their counterparts to its south, and such plateau shielding is not needed. By virtue of hydrological analysis, we show that the high energy near the surface required for continental monsoon development is maintained mainly by high water vapor content. Results based on potential vorticity-potential temperature diagnosis further demonstrate that it is the pumping of water vapor from sea to land due to the thermal effects of the plateaus that breeds the Asian continental monsoon.

  20. Assessment of the Impact of The East Asian Summer Monsoon on the Air Quality Over China

    Science.gov (United States)

    Hao, Nan; Ding, Aijun; Safieddine, Sarah; Valks, Pieter; Clerbaux, Cathy; Trautmann, Thomas

    2016-04-01

    Air pollution is one of the most important environmental problems in developing Asian countries like China. In this region, studies showed that the East Asian monsoon plays a significant role in characterizing the temporal variation and spatial patterns of air pollution, since monsoon is a major atmospheric system affecting air mass transport, convection, and precipitation. Knowledge gaps still exist in the understanding of Asian monsoon impact on the air quality in China under the background of global climate change. For the first time satellite observations of tropospheric ozone and its precursors will be integrated with the ground-based, aircraft measurements of air pollutants and model simulations to study the impact of the East Asian monsoon on air quality in China. We apply multi-platform satellite observations by the GOME-2, IASI, and MOPITT instruments to analyze tropospheric ozone and CO, precursors of ozone (NO2, HCHO and CHOCHO) and other related trace gases over China. Two years measurements of air pollutants including NO2, HONO, SO2, HCHO and CHOCHO at a regional back-ground site in the western part of the Yangtze River Delta (YRD) in eastern China will be presented. The potential of using the current generation of satellite instruments, ground-based instruments and aircraft to monitor air quality changes caused by the East Asian monsoon circulation will be presented. Preliminary comparison results between satellite measurement and limited but valuable ground-based and aircraft measurements will also be showed.

  1. Projected changes of summer monsoon extremes and hydroclimatic regimes over West Africa for the twenty-first century

    Science.gov (United States)

    Diallo, Ismaïla; Giorgi, Filippo; Deme, Abdoulaye; Tall, Moustapha; Mariotti, Laura; Gaye, Amadou T.

    2016-12-01

    We use two CORDEX-Africa simulations performed with the regional model RegCM4 to characterize the projected changes in extremes and hydroclimatic regimes associated with the West African Monsoon (WAM). RegCM4 was driven for the period 1970-2100 by the HadGEM2-ES and the MPI-ESM Global Climate Models (GCMs) under the RCP8.5 greenhouse gas concentration pathway. RegCM4 accurately simulates the WAM characteristics in terms of seasonal mean, seasonal cycle, interannual variability and extreme events of rainfall. Overall, both RegCM4 experiments are able to reproduce the large-scale atmospheric circulation for the reference period (i.e. present-day), and in fact show improved performance compared to the driving GCMs in terms of precipitation mean climatology and extreme events, although different shortcomings in the various models are still evident. Precipitation is projected to decrease (increase) over western (eastern) Sahel, although with different spatial detail between RegCM4 and the corresponding driving GCMs. Changes in extreme precipitation events show patterns in line with those of the mean change. The models project different changes in water budget over the Sahel region, where the MPI projects an increased deficit in local moisture supply (E P). The E-P change is primarily precipitation driven. The precipitation increases over the eastern and/or central Sahel are attributed to the increase of moisture convergence due to increased water vapor in the boundary layer air column and surface evaporation. On the other hand, the projected dry conditions over the western Sahel are associated with the strengthening of moisture divergence in the upper level (850-300 hPa) combined to both a southward migration of the African Easterly Jet (AEJ) and a weakening of rising motion between the core of the AEJ and the Tropical Easterly Jet.

  2. Biogeochemical variability in the central equatorial Indian Ocean during the monsoon transition

    Science.gov (United States)

    Strutton, P. G.; Coles, V. J.; Hood, R. R.; Matear, R. J.; McPhaden, M. J.; Phillips, H. E.

    2015-04-01

    In this paper we examine time-series measurements of near-surface chlorophyll concentration from a mooring that was deployed at 80.5°E on the equator in the Indian Ocean in 2010. These data reveal at least six striking spikes in chlorophyll from October through December, at approximately 2-week intervals, that coincide with the development of the fall Wyrtki jets during the transition between the summer and winter monsoons. Concurrent meteorological and in situ physical measurements from the mooring reveal that the chlorophyll pulses are associated with the intensification of eastward winds at the surface and eastward currents in the mixed layer. These observations are inconsistent with upwelling dynamics as they occur in the Atlantic and Pacific oceans, since eastward winds that force Wyrtki jet intensification should drive downwelling. The chlorophyll spikes could be explained by two alternative mechanisms: (1) turbulent entrainment of nutrients and/or chlorophyll from across the base of the mixed layer by wind stirring or Wyrtki jet-induced shear instability or (2) enhanced southward advection of high chlorophyll concentrations into the equatorial zone. The first mechanism is supported by the phasing and amplitude of the relationship between wind stress and chlorophyll, which suggests that the chlorophyll spikes are the result of turbulent entrainment driven by synoptic zonal wind events. The second mechanism is supported by the observation of eastward flows over the Chagos-Laccadive Ridge, generating high chlorophyll to the north of the equator. Occasional southward advection can then produce the chlorophyll spikes that are observed in the mooring record. Wind-forced biweekly mixed Rossby gravity waves are a ubiquitous feature of the ocean circulation in this region, and we examine the possibility that they may play a role in chlorophyll variability. Statistical analyses and results from the OFAM3 (Ocean Forecasting Australia Model, version 3) eddy

  3. Biogeochemical variability in the equatorial Indian Ocean during the monsoon transition

    Science.gov (United States)

    Strutton, P. G.; Coles, V. J.; Hood, R. R.; Matear, R. J.; McPhaden, M. J.; Phillips, H. E.

    2014-04-01

    In this paper we examine time-series measurements of near-surface chlorophyll concentration from a mooring that was deployed at 80.5° E on the equator in the Indian Ocean in 2010. These data reveal at least six striking spikes in chlorophyll in October through December, with approximately 2 week periodicity, that coincide with the development of the fall Wyrtki jets during the transition between the summer and winter monsoons. Concurrent meteorological and in situ physical measurements from the mooring reveal that the chlorophyll pulses are associated with intensification of eastward winds at the surface and eastward currents in the mixed layer. These observations are inconsistent with upwelling dynamics as occurs in the Atlantic and Pacific Oceans, since eastward winds that force Wyrtki jet intensification should drive downwelling. The chlorophyll spikes could be explained by two alternative mechanisms: (1) turbulent entrainment of nutrients and/or chlorophyll from across the base of the mixed layer by wind stirring or Wyrtki jet-induced shear instability; or (2) enhanced horizontal advection of high chlorophyll concentrations into the convergent equatorial zone. The first mechanism is supported by the phasing and amplitude of the relationship between wind stress and chlorophyll, which suggests that the chlorophyll spikes are the result of turbulent entrainment driven by synoptic zonal wind events. The second mechanism is supported by satellite chlorophyll observations that reveal a clear connection between the increased chlorophyll concentrations at the mooring location and larger-scale topographic wake effects from the Chagos-Lacadive Ridge upstream. The biweekly periodicity of the chlorophyll spikes appears to be related to the presence of mixed Rossby-gravity waves, also known as Yanai waves, which can be seen throughout the time-series as a biweekly periodicity in the meridional velocities with upward phase propagation. Consistent with hypothesis 2, eastward

  4. Biogeochemical variability in the equatorial Indian Ocean during the monsoon transition

    Directory of Open Access Journals (Sweden)

    P. G. Strutton

    2014-04-01

    Full Text Available In this paper we examine time-series measurements of near-surface chlorophyll concentration from a mooring that was deployed at 80.5° E on the equator in the Indian Ocean in 2010. These data reveal at least six striking spikes in chlorophyll in October through December, with approximately 2 week periodicity, that coincide with the development of the fall Wyrtki jets during the transition between the summer and winter monsoons. Concurrent meteorological and in situ physical measurements from the mooring reveal that the chlorophyll pulses are associated with intensification of eastward winds at the surface and eastward currents in the mixed layer. These observations are inconsistent with upwelling dynamics as occurs in the Atlantic and Pacific Oceans, since eastward winds that force Wyrtki jet intensification should drive downwelling. The chlorophyll spikes could be explained by two alternative mechanisms: (1 turbulent entrainment of nutrients and/or chlorophyll from across the base of the mixed layer by wind stirring or Wyrtki jet-induced shear instability; or (2 enhanced horizontal advection of high chlorophyll concentrations into the convergent equatorial zone. The first mechanism is supported by the phasing and amplitude of the relationship between wind stress and chlorophyll, which suggests that the chlorophyll spikes are the result of turbulent entrainment driven by synoptic zonal wind events. The second mechanism is supported by satellite chlorophyll observations that reveal a clear connection between the increased chlorophyll concentrations at the mooring location and larger-scale topographic wake effects from the Chagos–Lacadive Ridge upstream. The biweekly periodicity of the chlorophyll spikes appears to be related to the presence of mixed Rossby-gravity waves, also known as Yanai waves, which can be seen throughout the time-series as a biweekly periodicity in the meridional velocities with upward phase propagation. Consistent with

  5. Pre- and post-monsoonal changes in grain size and heavy minerals in the sediments from Kalbadevi Bay, Ratnagiri, west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Valsangkar, A.B.; Fernandes, D.

    distribution. Clay accumulation in the Bay begins after the culmination of monsoonal effects. Distribution of ilmenite appears similar to that of magnetite. Pre- and post- monsoonal changes in the distribution pattern of heavy minerals show that fine to very...

  6. Warm pool thermodynamics from the Arabian Sea Monsoon Experiment (ARMEX)

    Digital Repository Service at National Institute of Oceanography (India)

    Sengupta, D.; Parampil, S.R.; Bhat, G.S.; Murty, V.S.N.; RameshBabu, V.; Sudhakar, T.; Premkumar, K.; Pradhan, Y.

    driven upper ocean currents (e.g. Sun and Liu [1996]; Loschnigg and Webster [2000]; Clement et al. [2005]), and (c) enhanced evaporation over warm SST and redistribution of boundary-layer moisture or of elevated latent heating by large scale atmospheric... observations show the presence of shallow mixed layers, barrier layers and temperature inversions (Shenoi et al [2004], Shankar et al [2004]). In addition to salinity effects, the north Indian Ocean warm pool also becomes increasingly stably stratified...

  7. Laser-Driven Fusion.

    Science.gov (United States)

    Gibson, A. F.

    1980-01-01

    Discusses the present status and future prospects of laser-driven fusion. Current research (which is classified under three main headings: laser-matter interaction processes, compression, and laser development) is also presented. (HM)

  8. Quantifying pollution transport from the Asian monsoon anticyclone into the lower stratosphere

    Directory of Open Access Journals (Sweden)

    F. Ploeger

    2017-06-01

    Full Text Available Pollution transport from the surface to the stratosphere within the Asian monsoon circulation may cause harmful effects on stratospheric chemistry and climate. Here, we investigate air mass transport from the monsoon anticyclone into the stratosphere using a Lagrangian chemistry transport model. We show how two main transport pathways from the anticyclone emerge: (i into the tropical stratosphere (tropical pipe, and (ii into the Northern Hemisphere (NH extratropical lower stratosphere. Maximum anticyclone air mass fractions reach around 5 % in the tropical pipe and 15 % in the extratropical lowermost stratosphere over the course of a year. The anticyclone air mass fraction correlates well with satellite hydrogen cyanide (HCN and carbon monoxide (CO observations, confirming that pollution is transported deep into the tropical stratosphere from the Asian monsoon anticyclone. Cross-tropopause transport occurs in a vertical chimney, but with the pollutants transported quasi-horizontally along isentropes above the tropopause into the tropics and NH.

  9. Influence of cosmic-ray variability on the monsoon rainfall and temperature

    CERN Document Server

    Badruddin,

    2014-01-01

    We study the role of galactic cosmic ray (GCR) variability in influencing the rainfall variability in Indian Summer Monsoon Rainfall (ISMR) season. We find that on an average during 'drought' (low ISMR) periods in India, GCR flux is decreasing, and during 'flood' (high ISMR) periods, GCR flux is increasing. The results of our analysis suggest for a possibility that the decreasing GCR flux during the summer monsoon season in India may suppress the rainfall. On the other hand, increasing GCR flux may enhance the rainfall. We suspect that in addition to real environmental conditions, significant levitation/dispersion of low clouds and hence reduced possibility of collision/coalescence to form raindrops suppresses the rainfall during decreasing GCR flux in monsoon season. On the other hand, enhanced collision/coalescence efficiency during increasing GCR flux due to electrical effects may contribute to enhancing the rainfall. Based on the observations, we put forward the idea that, under suitable environmental con...

  10. Lag influences of winter circulation conditions in the tropical western Pacific on South Asian summer monsoon

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    By means of monthly mean NCEP/NCAR data analyses, this note investigates the lag influences of winter circulation conditions in the tropical western Pacific on South Asian summer monsoon through the methods of composite, correlation and statistical confident test. The results indicate clearly that winter climate variations in the equatorial western Pacific would produce significant influences on the following South Asian summer monsoon, and with the lapse of time the lag influences show clearly moving northward and extending westward features. When winter positive (negative) sea level pressure anomalies occupy the equatorial western Pacific, there is an anticyclonic (cyclonic) circulation anomaly appearing in the northwestern Pacific. With the lapse of time, the anticyclonic (cyclonic) circulation anomaly gradually moves to northeast, and its axis in the west-east directions also stretches, therefore, easterly (westerly) anomalies in the south part of the anticyclonic (cyclonic) circulation anomaly continuously expand westward to the peninsula of India. Undoubtedly, the South Asian summer monsoon is weak (strong)

  11. On the recent strengthening of the relationship between ENSO and northeast monsoon rainfall over South Asia

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Pankaj; Rupa Kumar, K.; Sahai, A.K. [Indian Institute of Tropical Meteorology, Pune (India); Rajeevan, M. [India Meteorological Department, Pune (India)

    2007-05-15

    The southeastern parts of India and Sri Lanka receive substantial rainfall from the northeast monsoon (NEM) during October through December. The interannual variability in NEM rainfall is known to be significantly influenced by the El-Nino/Southern Oscillation (ENSO). Unlike the southwest monsoon (SWM), the NEM rainfall is enhanced during the warm ENSO events, and vice versa. In the context of the recent weakening of the inverse relationship between Southwest Monsoon (SWM) and ENSO, we examine the secular variations in the positive relationship between ENSO and NEM rainfall over South Asia, showing that their relationship has strengthened over the recent years. Based on the analysis of GISST, IMD/CRU precipitation and NCEP/NCAR reanalysis data, we suggest that this secular variation of the relationship is due to epochal changes in the tropospheric circulation associated with ENSO over the region. (orig.)

  12. Impact of Anthropogenic Climate Change on the East Asian Summer Monsoon

    Science.gov (United States)

    Burke, Claire; Stott, Peter

    2017-07-01

    The East Asian summer monsoon (EASM) is important for bringing rainfall to large areas of China. Historically, variations in the EASM have had major impacts including flooding and drought. We present an analysis of the impact of anthropogenic climate change on EASM rainfall in Eastern China using a newly updated attribution system. Our results suggest that anthropogenic climate change has led to an overall decrease in total monsoon rainfall over the past 65 years, and an increased number of dry days. However the model also predicts that anthropogenic forcings have caused the most extreme heavy rainfall events to become shorter in duration and more intense. With the potential for future changes in aerosol and greenhouse gas emissions, historical trends in monsoon rainfall may not be indicative of future changes, although extreme rainfall is projected to increase over East Asia with continued warming in the region.

  13. Significance of the normalized seasonality of wind field and its rationality for characterizing the monsoon

    Institute of Scientific and Technical Information of China (English)

    李建平; 曾庆存

    2000-01-01

    The significance of the normalized seasonality of wind field is theoretically studied and the intrinsic relationship between its critical value and the definition of the monsoon region is revealed. As a result, the rationality which the monsoon region is characterized by the significant normalized seasonality is proved. Based on this, by use of the NECP/NCAR reanalysis data during 1958-1997, the spatial structure of the significant normalized seasonality of wind field is investigated, and the significant baroclinity of the seasonal variation of the atmospheric general circulation in the vertical direction is verified. Moreover, in the tropics there exists an anti-symmetric distribution between the significant seasonality in the eastern hemisphere and that in the western hemisphere, and the monsoon is linked closely to some important systems such as the subtropical highs, the night jet and the west wind channels.

  14. Prediction of monsoon rainfall with a nested grid mesoscale limited area model

    Indian Academy of Sciences (India)

    S K Roy Bhowmik

    2003-12-01

    At the India Meteorological Department (IMD), New Delhi, a 12-level limited area model with 100km horizontal resolution has been in use for weather forecasting. The present study uses this model together with a higher horizontal resolution (50 km) and vertical resolution (16-levels) model to examine the impact of increased resolution to simulate mesoscale features of rainfall during monsoon disturbances. The model was run for 22 days in the month of August 1997 and one week in September 1997 during three monsoon depressions and one cyclonic storm in the Bay of Bengal. The model results are compared with observations. The study shows that the model can capture mesoscale convective organization associated with monsoon depression.

  15. Analysis of spatial and temporal extreme monsoonal rainfall over South Asia using complex networks

    Energy Technology Data Exchange (ETDEWEB)

    Malik, Nishant [Potsdam Institute for Climate Impact Research, P.O. Box 60 12 03, Potsdam (Germany); University of Potsdam, Institute of Physics, Potsdam-Golm (Germany); Bookhagen, Bodo [University of California Santa Barbara, Department of Geography, Santa Barbara, CA (United States); Marwan, Norbert [Potsdam Institute for Climate Impact Research, P.O. Box 60 12 03, Potsdam (Germany); Kurths, Juergen [Potsdam Institute for Climate Impact Research, P.O. Box 60 12 03, Potsdam (Germany); Humboldt University, Department of Physics, Berlin (Germany)

    2012-08-15

    We present a detailed analysis of summer monsoon rainfall over the Indian peninsular using nonlinear spatial correlations. This analysis is carried out employing the tools of complex networks and a measure of nonlinear correlation for point processes such as rainfall, called event synchronization. This study provides valuable insights into the spatial organization, scales, and structure of the 90th and 94th percentile rainfall events during the Indian summer monsoon (June-September). We furthermore analyse the influence of different critical synoptic atmospheric systems and the impact of the steep Himalayan topography on rainfall patterns. The presented method not only helps us in visualising the structure of the extreme-event rainfall fields, but also identifies the water vapor pathways and decadal-scale moisture sinks over the region. Furthermore a simple scheme based on complex networks is presented to decipher the spatial intricacies and temporal evolution of monsoonal rainfall patterns over the last 6 decades. (orig.)

  16. Sea breeze Initiated Rainfall over the east Coast of India during the Indian Southwest Monsoon

    Energy Technology Data Exchange (ETDEWEB)

    Simpson, M; Warrior, H; Raman, S; Aswathanarayana, P A; Mohanty, U C; Suresh, R

    2006-09-05

    Sea breeze initiated convection and precipitation is investigated along the east coast of India during the Indian southwest monsoon season. The sea breeze circulations are observed approximately 70 to 80% of the days during the summer months (June to August) along the Chennai coast. Observations of average sea breeze wind speeds are stronger at a rural location as compared to the wind speeds observed inside the urban region of Chennai. The sea breeze circulation is shown to be the dominant mechanism for initiating rainfall during the Indian southwest monsoon season. Roughly 80% of the total rainfall observed during the southwest monsoon over Chennai is directly related to the convection initiated by sea breeze circulation.

  17. South Asian Summer Monsoon and Its Relationship with ENSO in the IPCC AR4 Simulations

    Energy Technology Data Exchange (ETDEWEB)

    Annamalai, H; Hamilton, K; Sperber, K R

    2005-09-07

    In this paper we use the extensive integrations produced for the IPCC Fourth Assessment Report (AR4) to examine the relationship between ENSO and the monsoon at interannual and decadal timescales. We begin with an analysis of the monsoon simulation in the 20th century integrations. Six of the 18 models were found to have a reasonably realistic representation of monsoon precipitation climatology. For each of these six models SST and anomalous precipitation evolution along the equatorial Pacific during El Nino events display considerable differences when compared to observations. Out of these six models only four (GFDL{_}CM{_}2.0, GFDL{_}CM{_}2.1, MRI, and MPI{_}ECHAM5) exhibit a robust ENSO-monsoon contemporaneous teleconnection, including the known inverse relationship between ENSO and rainfall variations over India. Lagged correlations between the all-India rainfall (AIR) index and Nino3.4 SST reveal that three models represent the timing of the teleconnection, including the spring predictability barrier which is manifested as the transition from positive to negative correlations prior to the monsoon onset. Furthermore, only one of these three models (GFDL{_}CM{_}2.1) captures the observed phase lag with the strongest anticorrelation of SST peaking 2-3 months after the summer monsoon, which is partially attributable to the intensity of simulated El Nino itself. We find that the models that best capture the ENSO-monsoon