WorldWideScience

Sample records for strong inter-annual rainfall

  1. The impact of inter-annual rainfall variability on African savannas changes with mean rainfall.

    Science.gov (United States)

    Synodinos, Alexis D; Tietjen, Britta; Lohmann, Dirk; Jeltsch, Florian

    2018-01-21

    Savannas are mixed tree-grass ecosystems whose dynamics are predominantly regulated by resource competition and the temporal variability in climatic and environmental factors such as rainfall and fire. Hence, increasing inter-annual rainfall variability due to climate change could have a significant impact on savannas. To investigate this, we used an ecohydrological model of stochastic differential equations and simulated African savanna dynamics along a gradient of mean annual rainfall (520-780 mm/year) for a range of inter-annual rainfall variabilities. Our simulations produced alternative states of grassland and savanna across the mean rainfall gradient. Increasing inter-annual variability had a negative effect on the savanna state under dry conditions (520 mm/year), and a positive effect under moister conditions (580-780 mm/year). The former resulted from the net negative effect of dry and wet extremes on trees. In semi-arid conditions (520 mm/year), dry extremes caused a loss of tree cover, which could not be recovered during wet extremes because of strong resource competition and the increased frequency of fires. At high mean rainfall (780 mm/year), increased variability enhanced savanna resilience. Here, resources were no longer limiting and the slow tree dynamics buffered against variability by maintaining a stable population during 'dry' extremes, providing the basis for growth during wet extremes. Simultaneously, high rainfall years had a weak marginal benefit on grass cover due to density-regulation and grazing. Our results suggest that the effects of the slow tree and fast grass dynamics on tree-grass interactions will become a major determinant of the savanna vegetation composition with increasing rainfall variability. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Inter-annual rainfall variability and droughts occurrence during ...

    African Journals Online (AJOL)

    This study examined the trends of rainfall and the intensity of drought during sowing season and mid-season of rice farming calendar in the rainforest belt of Nigeria using data spanning 52 years (1961-2012) for five synoptic weather stations. The trends were investigated using simple linear regression and second order ...

  3. Skilful prediction of Sahel summer rainfall on inter-annual and multi-year timescales.

    Science.gov (United States)

    Sheen, K L; Smith, D M; Dunstone, N J; Eade, R; Rowell, D P; Vellinga, M

    2017-05-25

    Summer rainfall in the Sahel region of Africa exhibits one of the largest signals of climatic variability and with a population reliant on agricultural productivity, the Sahel is particularly vulnerable to major droughts such as occurred in the 1970s and 1980s. Rainfall levels have subsequently recovered, but future projections remain uncertain. Here we show that Sahel rainfall is skilfully predicted on inter-annual and multi-year (that is, >5 years) timescales and use these predictions to better understand the driving mechanisms. Moisture budget analysis indicates that on multi-year timescales, a warmer north Atlantic and Mediterranean enhance Sahel rainfall through increased meridional convergence of low-level, externally sourced moisture. In contrast, year-to-year rainfall levels are largely determined by the recycling rate of local moisture, regulated by planetary circulation patterns associated with the El Niño-Southern Oscillation. Our findings aid improved understanding and forecasting of Sahel drought, paramount for successful adaptation strategies in a changing climate.

  4. Large-Scale Processes Associated with Inter-Decadal and Inter-Annual Early Spring Rainfall Variability in Taiwan

    Directory of Open Access Journals (Sweden)

    Jau-Ming Chen

    2016-02-01

    Full Text Available Early spring (March - April rainfall in Taiwan exhibits evident and distinct inter-annual and inter-decadal variability. The inter-annual varibility has a positive correlation with the El Niño/Southern Oscillation while the inter-decadal variability features a phase change beginning in the late 1970s, coherent with the major phase change in the Pacific decadal oscillation. Rainfall variability in both timescales is regulated by large-scale processes showing consistent dynamic features. Rainfall increases are associated with positive sea surface temperature (SST anomalies in the tropical eastern Pacific and negative SST anomalies in the tropical central Pacific. An anomalous lower-level divergent center appears in the tropical central Pacific. Via a Rossby-wave-like response, an anomalous lower-level anticyclone appears to the southeast of Taiwan over the Philippine Sea-tropical western Pacific region, which is accompanied by an anomalous cyclone to the north-northeast of Taiwan. Both circulation anomalies induce anomalous southwesterly flows to enhance moisture flux from the South China Sea onto Taiwan, resulting in significant moisture convergence nearby Taiwan. With enhanced moisture supplied by anomalous southwesterly flows, significant rainfall increases occur in both inter-annual and inter-decadal timescales in early spring rainfall on Taiwan.

  5. Factors affecting the inter-annual to centennial timescale variability of Indian summer monsoon rainfall

    Science.gov (United States)

    Malik, Abdul; Brönnimann, Stefan

    2017-09-01

    The Modes of Ocean Variability (MOV) namely Atlantic Multidecadal Oscillation (AMO), Pacific Decadal Oscillation (PDO), and El Niño Southern Oscillation (ENSO) can have significant impacts on Indian Summer Monsoon Rainfall (ISMR) on different timescales. The timescales at which these MOV interacts with ISMR and the factors which may perturb their relationship with ISMR need to be investigated. We employ De-trended Cross-Correlation Analysis (DCCA), and De-trended Partial-Cross-Correlation Analysis (DPCCA) to study the timescales of interaction of ISMR with AMO, PDO, and ENSO using observational dataset (AD 1854-1999), and atmosphere-ocean-chemistry climate model simulations with SOCOL-MPIOM (AD 1600-1999). Further, this study uses De-trended Semi-Partial Cross-Correlation Analysis (DSPCCA) to address the relation between solar variability and the ISMR. We find statistically significant evidence of intrinsic correlations of ISMR with AMO, PDO, and ENSO on different timescales, consistent between model simulations and observations. However, the model fails to capture modulation in intrinsic relationship between ISRM and MOV due to external signals. Our analysis indicates that AMO is a potential source of non-stationary relationship between ISMR and ENSO. Furthermore, the pattern of correlation between ISMR and Total Solar Irradiance (TSI) is inconsistent between observations and model simulations. The observational dataset indicates statistically insignificant negative intrinsic correlation between ISMR and TSI on decadal-to-centennial timescales. This statistically insignificant negative intrinsic correlation is transformed to statistically significant positive extrinsic by AMO on 61-86-year timescale. We propose a new mechanism for Sun-monsoon connection which operates through AMO by changes in summer (June-September; JJAS) meridional gradient of tropospheric temperatures (ΔTTJJAS). There is a negative (positive) intrinsic correlation between ΔTTJJAS (AMO) and

  6. Intra-seasonal oscillations associated with Indian Ocean warm pool and summer monsoon rainfall and their inter-annual variability

    Digital Repository Service at National Institute of Oceanography (India)

    Muraleedharan, P.M.; Nisha, P.G.; Sathe, P.V.; Sivakumar, K.U.

    and SST at the East Coast by 20 to 30 days, the coefficient of correlation 8 did not support a strong relationship. The OLR, again failed to support the 20 to 30 days lead showed by SST and WS. Strong and significant relationships between rainfall... supports high OLR with the same phase lag. Therefore the difference in phase lag between OLR and rainfall is anticipated and is in line with the argument that a reversal of relationship is expected with the same 20 to 30 days phase lag to support...

  7. Universal Inverse Power-Law Distribution for Fractal Fluctuations in Dynamical Systems: Applications for Predictability of Inter-Annual Variability of Indian and USA Region Rainfall

    Science.gov (United States)

    Selvam, A. M.

    2017-01-01

    Dynamical systems in nature exhibit self-similar fractal space-time fluctuations on all scales indicating long-range correlations and, therefore, the statistical normal distribution with implicit assumption of independence, fixed mean and standard deviation cannot be used for description and quantification of fractal data sets. The author has developed a general systems theory based on classical statistical physics for fractal fluctuations which predicts the following. (1) The fractal fluctuations signify an underlying eddy continuum, the larger eddies being the integrated mean of enclosed smaller-scale fluctuations. (2) The probability distribution of eddy amplitudes and the variance (square of eddy amplitude) spectrum of fractal fluctuations follow the universal Boltzmann inverse power law expressed as a function of the golden mean. (3) Fractal fluctuations are signatures of quantum-like chaos since the additive amplitudes of eddies when squared represent probability densities analogous to the sub-atomic dynamics of quantum systems such as the photon or electron. (4) The model predicted distribution is very close to statistical normal distribution for moderate events within two standard deviations from the mean but exhibits a fat long tail that are associated with hazardous extreme events. Continuous periodogram power spectral analyses of available GHCN annual total rainfall time series for the period 1900-2008 for Indian and USA stations show that the power spectra and the corresponding probability distributions follow model predicted universal inverse power law form signifying an eddy continuum structure underlying the observed inter-annual variability of rainfall. On a global scale, man-made greenhouse gas related atmospheric warming would result in intensification of natural climate variability, seen immediately in high frequency fluctuations such as QBO and ENSO and even shorter timescales. Model concepts and results of analyses are discussed with reference

  8. Drivers of inter-annual variability in Net Ecosystem Exchange in a semi-arid savanna ecosystem, South Africa

    Directory of Open Access Journals (Sweden)

    S. A. Archibald

    2009-02-01

    Full Text Available Inter-annual variability in primary production and ecosystem respiration was explored using eddy-covariance data at a semi-arid savanna site in the Kruger Park, South Africa. New methods of extrapolating night-time respiration to the entire day and filling gaps in eddy-covariance data in semi-arid systems were developed. Net ecosystem exchange (NEE in these systems occurs as pulses associated with rainfall events, a pattern not well-represented in current standard gap-filling procedures developed primarily for temperate flux sites. They furthermore do not take into account the decrease in respiration at high soil temperatures. An artificial neural network (ANN model incorporating these features predicted measured fluxes accurately (MAE 0.42 gC/m2/day, and was able to represent the seasonal patterns of photosynthesis and respiration at the site. The amount of green leaf area (indexed using satellite-derived estimates of fractional interception of photosynthetically active radiation fAPAR, and the timing and magnitude of rainfall events, were the two most important predictors used in the ANN model. These drivers were also identified by multiple linear regressions (MLR, with strong interactive effects. The annual integral of the filled NEE data was found to range from −138 to +155 g C/m2/y over the 5 year eddy covariance measurement period. When applied to a 25 year time series of meteorological data, the ANN model predicts an annual mean NEE of 75(±105 g C/m2/y. The main correlates of this inter-annual variability were found to be variation in the amount of absorbed photosynthetically active radiation (APAR, length of the growing season, and number of days in the year when moisture was available in the soil.

  9. ENSO Related Inter-Annual Lightning Variability from the Full TRMM LIS Lightning Climatology

    Science.gov (United States)

    Clark, Austin; Cecil, Daniel

    2018-01-01

    The El Nino/Southern Oscillation (ENSO) contributes to inter-annual variability of lightning production more than any other atmospheric oscillation. This study further investigated how ENSO phase affects lightning production in the tropics and subtropics using the Tropical Rainfall Measuring Mission (TRMM) Lightning Imaging Sensor (LIS). Lightning data were averaged into mean annual warm, cold, and neutral 'years' for analysis of the different phases and compared to model reanalysis data. An examination of the regional sensitivities and preliminary analysis of three locations was conducted using model reanalysis data to determine the leading convective mechanisms in these areas and how they might respond to the ENSO phases

  10. The influence of intra- and inter-annual meteorological variability on dengue transmission: a multi-level modeling analysis

    Science.gov (United States)

    Wen, Tzai-Hung; Chen, Tzu-Hsin

    2017-04-01

    Dengue fever is one of potentially life-threatening mosquito-borne diseases and IPCC Fifth Assessment Report (AR5) has confirmed that dengue incidence is sensitive to the critical weather conditions, such as effects of temperature. However, previous literature focused on the effects of monthly or weekly average temperature or accumulative precipitation on dengue incidence. The influence of intra- and inter-annual meteorological variability on dengue outbreak is under investigated. The purpose of the study focuses on measuring the effect of the intra- and inter-annual variations of temperature and precipitation on dengue outbreaks. We developed the indices of intra-annual temperature variability are maximum continuity, intermittent, and accumulation of most suitable temperature (MST) for dengue vectors; and also the indices of intra-annual precipitation variability, including the measure of continuity of wetness or dryness during a pre-epidemic period; and rainfall intensity during an epidemic period. We used multi-level modeling to investigate the intra- and inter-annual meteorological variations on dengue outbreaks in southern Taiwan from 1998-2015. Our results indicate that accumulation and maximum continuity of MST are more significant than average temperature on dengue outbreaks. The effect of continuity of wetness during the pre-epidemic period is significantly more positive on promoting dengue outbreaks than the rainfall effect during the epidemic period. Meanwhile, extremely high or low rainfall density during an epidemic period do not promote the spread of dengue epidemics. Our study differentiates the effects of intra- and inter-annual meteorological variations on dengue outbreaks and also provides policy implications for further dengue control under the threats of climate change. Keywords: dengue fever, meteorological variations, multi-level model

  11. Improving uncertainty estimates: Inter-annual variability in Ireland

    Science.gov (United States)

    Pullinger, D.; Zhang, M.; Hill, N.; Crutchley, T.

    2017-11-01

    This paper addresses the uncertainty associated with inter-annual variability used within wind resource assessments for Ireland in order to more accurately represent the uncertainties within wind resource and energy yield assessments. The study was undertaken using a total of 16 ground stations (Met Eireann) and corresponding reanalysis datasets to provide an update to previous work on this topic undertaken nearly 20 years ago. The results of the work demonstrate that the previously reported 5.4% of wind speed inter-annual variability is considered to be appropriate, guidance is given on how to provide a robust assessment of IAV using available sources of data including ground stations, MERRA-2 and ERA-Interim.

  12. Global inter-annual gravity changes from GRACE: Early results

    DEFF Research Database (Denmark)

    Andersen, Ole Baltazar; Hinderer, J.

    2005-01-01

    Fifteen monthly gravity field solutions from the GRACE twin satellites launched more than two years ago have been studied to estimate gravity field changes between 2002 and 2003. The results demonstrate that GRACE is capable of capturing the changes in ground water on inter-annual scales...... with an accuracy of 0.4 muGal corresponding to 9 mm water thickness on spatial scales longer than 1300 km. Four of the most widely used global hydrological models have been investigated for their spatial comparison with GRACE observations of inter-annual gravity field variations due to changes in continental water...... storage. The Global Land Data Assimilation System model has a spatial correlation coefficient with GRACE observations of 0.65 over the northern hemisphere. This demonstrates that the observed gravity field changes on these scales are largely related to changes in continental water storage....

  13. Inter-annual variation in the response of Pinus taeda tree growth to long term Free Air Carbon dioxide Enrichment (FACE)

    Science.gov (United States)

    Moore, D. J.; Aref, S.; Ho, R. M.; Pippen, J. S.; Hamilton, J.; de Lucia, E. H.

    2005-12-01

    Rising carbon dioxide is predicted to increase forest productivity, though the duration of the response and how it might be altered by annual variation in rainfall and temperature are not well understood. For eight years we measured the basal area of trees exposed to Free Air Carbon-dioxide Enrichment (FACE) in a rapidly growing Pinus taeda plantation and used these measurements to estimate monthly and annual growth. We coupled these measurements with a mathematical model to estimate the start and end of growth in each year. Elevated carbon dioxide increased the basal area increment (BAI) of trees by 13 to 27 percent. Exposure to elevated carbon dioxide increased the growth rate but not the duration of the growing season in most years. With the exception of one year following an extreme drought and a severe ice storm, BAI was positively correlated with the amount of rainfall during the growing season. The inter-annual variation in the relative enhancement of BAI caused by elevated carbon dioxide was strongly related to the combination of temperature and rainfall during the growing season. There was no evidence of a systematic reduction in the stimulation of growth during the first eight years of this experiment, suggesting that hypothesized limitation of the carbon dioxide response caused by nitrogen availability has yet to occur.

  14. Consideration to the early warning rainfall criteria of landslides after strong earthquake in Japan

    Science.gov (United States)

    Kubota, T.

    2012-04-01

    1. Objective The research on the warning rainfall criteria of landslides after strong earthquakes is conducted associated with the great earthquake in Eastern Japan (M=9.0). After this kind of strong earthquake, soil strength of the slopes in the region that were exposed to the strong seismic forces are generally reduced by seismic shaking (vibration) or disturbance by certain slope deformation. In this situation, the revised rainfall criteria for landslides are required. On this point of view, we are intrigued to elucidate the response of landslide to rainfall under this weaken soil condition. Hence, the impact of rainfall events on the specific landslide slopes that experienced the strong seismic shaking is analyzed using numerical simulation method i.e. finite element method (FEM) in order to evaluate the critical rainfall for landslide occurrence. 2. Method and target areas Field investigation, field survey and geotechnical test with the samples from the landslide slopes are conducted to obtain the basic data for FEM analysis such as topographical, geological, geotechnical features including hydraulic conductivity "k" and soil shear strength at the slopes that experienced strong earthquake. Then, FEM analysis which consists of seepage analysis and slope stability analysis combined with the rain data at nearest meteorological observatory are conducted under the earthquake impact i.e. the slope condition with cracks which are located near the top of the slope and have high "k" or reduced soil strength. Comparing the FEM results with ones without earthquake impact, the influence of the earthquake shaking to the landslide slopes is estimated. 3. Result and consideration In the result of FEM analysis, the cracks induced by the earthquake are effective to increase the seepage and render the slopes instable. Also, reduced soil strength such as 4% decrease in internal friction angle caused instability of the slope. The slope deterioration mentioned above due to the

  15. Inter-annual to multi-decadal variability in prairie water resources over the past millennium

    International Nuclear Information System (INIS)

    Sauchyn, D.

    2008-01-01

    In the Prairie Provinces, declining levels have been recently recorded for various rivers and lakes, and further reductions are projected. These trends reflect human impact in terms of increasing water consumption and possibly anthropogenic climate change. From the coupling of hydrological models and climate change scenarios, researchers have projected lower future summer flows as global warming brings shorter warmer winters and longer and generally drier summers to western Canada. However, the detection and interpretation of trends from gauge records and model outputs are constrained by the relatively short perspective of decades and the uncertainties associated with projecting climate change and its impacts on hydrological regimes. A longer perspective on inter-annual to multi-decadal variability in water resources is available from moisture-sensitive tree-ring chronologies. We have established a dense network of low elevation chronologies spanning the headwaters of the Saskatchewan, Missouri, Churchill and Mackenzie River basins. Standardized tree-ring width for a large sample of trees and sites is a strong regional signal of annual and seasonal hydroclimate, and an especially good proxy of low water levels. Proxy streamflow records, up to 800 years in length, show quasi-periodic variability at inter-annual to multi-decadal scales that correspond to the tempo of sea-surface temperature anomalies. The industrial sponsors of our research, Manitoba Hydro and EPCOR, anticipate the use of our tree-ring reconstructions for informing forecasts of future water supplies and planning adaptation to climate change. Engineers from these companies, and more than 50 other water managers and planners from the Prairie Provinces, attended a workshop in March 2008 to explore potential applications of paleo-hydrological records to water resource management. (author)

  16. Inter-Annual Variability in Blue Whale Distribution off Southern Sri Lanka between 2011 and 2012

    Directory of Open Access Journals (Sweden)

    Asha de Vos

    2014-07-01

    Full Text Available Blue whale (Balaenoptera musculus movements are often driven by the availability of their prey in space and time. While globally blue whale populations undertake long-range migrations between feeding and breeding grounds, those in the northern Indian Ocean remain in low latitude waters throughout the year with the implication that the productivity of these waters is sufficient to support their energy needs. A part of this population remains around Sri Lanka where they are usually recorded close to the southern coast during the Northeast Monsoon. To investigate inter-annual variability in sighting locations, we conducted systematic Conductivity-Temperature-Depth (CTD and visual surveys between January–March 2011 and January–March 2012. In 2011, there was a notable decrease in inshore sightings compared to 2009 and 2012 (p < 0.001. CTD data revealed that in 2011 there was increased freshwater in the upper water column accompanied by deeper upwelling than in 2012. We hypothesise that anomalous rainfall, along with higher turbidity resulting from river discharge, affected the productivity of the inshore waters and caused a shift in blue whale prey and, consequently, the distribution of the whales themselves. An understanding of how predators and their prey respond to environmental variability is important for predicting how these species will respond to long-term changes. This is especially important given the rapid temperature increases predicted for the semi-enclosed northern Indian Ocean.

  17. Tree growth variation in the tropical forest: understanding effects of temperature, rainfall and CO2.

    Science.gov (United States)

    Schippers, Peter; Sterck, Frank; Vlam, Mart; Zuidema, Pieter A

    2015-01-28

    Tropical forest responses to climatic variability have important consequences for global carbon cycling, but are poorly understood. As empirical, correlative studies cannot disentangle the interactive effects of climatic variables on tree growth, we used a tree growth model (IBTREE) to unravel the climate effects on different physiological pathways and in turn on stem growth variation. We parameterized the model for canopy trees of Toona ciliata (Meliaceae) from a Thai monsoon forest and compared predicted and measured variation from a tree-ring study over a 30-year period. We used historical climatic variation of minimum and maximum day temperature, precipitation and carbon dioxide (CO 2 ) in different combinations to estimate the contribution of each climate factor in explaining the inter-annual variation in stem growth. Running the model with only variation in maximum temperature and rainfall yielded stem growth patterns that explained almost 70% of the observed inter-annual variation in stem growth. Our results show that maximum temperature had a strong negative effect on the stem growth by increasing respiration, reducing stomatal conductance and thus mitigating a higher transpiration demand, and - to a lesser extent - by directly reducing photosynthesis. Although stem growth was rather weakly sensitive to rain, stem growth variation responded strongly and positively to rainfall variation owing to the strong inter-annual fluctuations in rainfall. Minimum temperature and atmospheric CO 2 concentration did not significantly contribute to explaining the inter-annual variation in stem growth. Our innovative approach - combining a simulation model with historical data on tree-ring growth and climate - allowed disentangling the effects of strongly correlated climate variables on growth through different physiological pathways. Similar studies on different species and in different forest types are needed to further improve our understanding of the sensitivity of

  18. Intra-seasonal and Inter-annual variability of Bowen Ratio over rain-shadow region of North peninsular India

    Science.gov (United States)

    Morwal, S. B.; Narkhedkar, S. G.; Padmakumari, B.; Maheskumar, R. S.; Deshpande, C. G.; Kulkarni, J. R.

    2017-05-01

    Intra-seasonal and inter-annual variability of Bowen Ratio (BR) have been studied over the rain-shadow region of north peninsular India during summer monsoon season. Daily grid point data of latent heat flux (LHF), sensible heat flux (SHF) from NCEP/NCAR Reanalysis for the period 1970-2014 have been used to compute daily area-mean BR. Daily grid point rainfall data at a resolution of 0.25° × 0.25° from APHRODITE's Water Resources for the available period 1970-2007 have been used to study the association between rainfall and BR. The study revealed that BR rapidly decreases from 4.1 to 0.29 in the month of June and then remains nearly constant at the same value (≤0.1) in the rest of the season. High values of BR in the first half of June are indicative of intense thermals and convective clouds with higher bases. Low values of BR from July to September period are indicative of weak thermals and convective clouds with lower bases. Intra-seasonal and inter-annual variability of BR is found to be inversely related to precipitation over the region. BR analysis indicates that the land surface characteristics of the study region during July-September are similar to that over oceanic regions as far as intensity of thermals and associated cloud microphysical properties are concerned. Similar variation of BR is found in El Nino and La Nina years. During June, an increasing trend is observed in SHF and BR and decreasing trend in LHF from 1976 to 2014. Increasing trend in the SHF is statistically significant.

  19. Seasonal and inter-annual variability of the net ecosystem CO2 exchange of a temperate mountain grassland: effects of climate and management.

    Science.gov (United States)

    Wohlfahrt, Georg; Hammerle, Albin; Haslwanter, Alois; Bahn, Michael; Tappeiner, Ulrike; Cernusca, Alexander

    2008-04-27

    The role and relative importance of climate and cutting for the seasonal and inter-annual variability of the net ecosystem CO 2 (NEE) of a temperate mountain grassland was investigated. Eddy covariance CO 2 flux data and associated measurements of the green area index and the major environmental driving forces acquired during 2001-2006 at the study site Neustift (Austria) were analyzed. Driven by three cutting events per year which kept the investigated grassland in a stage of vigorous growth, the seasonal variability of NEE was primarily modulated by gross primary productivity (GPP). The role of environmental parameters in modulating the seasonal variability of NEE was obscured by the strong response of GPP to changes in the amount of green area, as well as the cutting-mediated decoupling of phenological development and the seasonal course of climate drivers. None of the climate and management metrics examined was able to explain the inter-annual variability of annual NEE. This is thought to result from (1) a high covariance between GPP and ecosystem respiration (R eco ) at the annual time scale which results in a comparatively small inter-annual variation of NEE, (2) compensating effects between carbon exchange during and outside the management period, and (3) changes in the biotic response to rather than the climate variables per se. GPP was more important in modulating inter-annual variations in NEE in spring and before the first and second cut, while R eco explained a larger fraction of the inter-annual variability of NEE during the remaining, in particular the post-cut, periods.

  20. Seasonal and inter-annual temperature variability in the bottom waters over the Black Sea shelf

    Science.gov (United States)

    Shapiro, G. I.; Wobus, F.; Aleynik, D. L.

    2011-02-01

    Long-term changes in the state of the Bottom Shelf Water (BSW) on the Western shelf of the Black Sea are assessed using analysis of intra- and inter-annual variations of temperature as well as their relations to physical parameters of both shelf and deep-sea waters. First, large data sets of in-situ observations over the 20th century are compiled into high-resolution monthly climatology at different depth levels. Then, the temperature anomalies from the climatic mean are calculated and aggregated into spatial compartments and seasonal bins to reveal temporal evolution of the BSW. For the purpose of this study the BSW is defined as such shelf water body between the seabed and the upper mixed layer (bounded by the σθ = 14.2 isopycnal) which has limited ability to mix vertically with oxygen-rich surface waters during the warm season (May-November) due to the formation of a seasonal pycnocline. The effects of atmospheric processes at the surface on the BSW are hence suppressed as well as the action of the "biological pump". The vertical extent of the near- bottom waters is determined based on energy considerations and the structure of the seasonal pycnocline, whilst the horizontal extent is controlled by the shelf break, where strong along-slope currents hinder exchanges with the deep sea. The BSW is shown to occupy nearly half of the area of the shelf during the summer stratification period. The potential of the BSW to ventilate horizontally during the warm season with the deep-sea waters is assessed using isopycnic analysis of temperature variations. A long-term time series of temperature anomalies in the BSW is constructed from observations during the May-November period for the 2nd half of the 20th century. The results reveal a warm phase in the 1960s/70s, followed by cooling of the BSW during 1980-2001. The transition between the warm and cold periods coincides with a regime shift in the Black Sea ecosystem. While it was confirmed that the memory of winter

  1. Seasonal and inter-annual variability of energy exchange above a boreal Scots pine forest

    Directory of Open Access Journals (Sweden)

    S. Launiainen

    2010-12-01

    Full Text Available Twelve-years of eddy-covariance measurements conducted above a boreal Scots pine forest in Hyytiälä, Southern Finland, were analyzed to assess the seasonal and inter-annual variability of surface conductance (gs and energy partitioning. The gs had distinct annual course, driven by the seasonal cycle of the Scots pine. Low gs (2–3 mm s−1 in April cause the sensible heat flux to peak in May–June while evapotranspiration takes over later in July–August when gs is typically 5–7 mm s−1. Hence, during normal years Bowen ratio decreases from 4–6 in April to 0.7–0.9 in August. Sensitivity of gs to ambient vapor pressure deficit (D was relatively constant but the reference value at D = 1 kPa varied seasonally and between years. Only two drought episodes when volumetric soil moisture content in upper mineral soil decreased below 0.15 m3 m−3 occurred during the period. Below this threshold value, transpiration was strongly reduced, which promoted sensible heat exchange increasing Bowen ratio to 3–4. Annual evapotranspiration varied between 218 and 361 mm and accounted between 50% and 90% of equilibrium evaporation. The forest floor contributed between 16 and 25% of the total evapotranspiration on annual scale. The fraction stayed similar over the observed range of environmental conditions including drought periods. The inter-annual variability of evapotranspiration could not be linked to any mean climate variable while the summertime sensible heat flux and net radiation were well explained by global radiation. The energy balance closure varied annually between 0.66 and 0.95 and had a distinct seasonal cycle with worse closure in spring when a large proportion of available energy is partitioned into sensible heat.

  2. Inter-annual variations in wave characteristics off Ratnagiri, Northeast Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Johnson, G.; SanilKumar, V.; Singh, J.

    The wave data measured using the Datawell directional wave rider buoy at 13 m water depth off Ratnagiri during 2010 to 2013 is used to study the inter-annual variations in the wave characteristics. The percentage occurrence of waves with significant...

  3. Black sea annual and inter-annual water mass variations from space

    DEFF Research Database (Denmark)

    Yildiz, H.; Andersen, Ole Baltazar; Simav, M.

    2011-01-01

    This study evaluates the performance of two widely used GRACE solutions (CNES/GRGS RL02 and CSR RL04) in deriving annual and inter-annual water mass variations in the Black Sea for the period 2003–2007. It is demonstrated that the GRACE derived water mass variations in the Black Sea are heavily i...

  4. Inter-annual trends of heavy metals in marine resources from the ...

    African Journals Online (AJOL)

    USER

    In an attempt to monitor and assess the pollution status of marine resources in the Nigerian territorial waters, this study was carried out to reveal the levels and inter-annual trend of heavy metals in marine resources from the Lagos lagoon marine ecosystem. Studies were carried out annually in the month of. July between ...

  5. Inter-annual trends of heavy metals in marine resources from the ...

    African Journals Online (AJOL)

    In an attempt to monitor and assess the pollution status of marine resources in the Nigerian territorial waters, this study was carried out to reveal the levels and inter-annual trend of heavy metals in marine resources from the Lagos lagoon marine ecosystem. Studies were carried out annually in the month of July between ...

  6. The Teleconnection of the Tropical Atlantic to Indo-Pacific Sea Surface Temperatures on Inter-Annual to Centennial Time Scales: A Review of Recent Findings

    Directory of Open Access Journals (Sweden)

    Fred Kucharski

    2016-02-01

    Full Text Available In this paper, the teleconnections from the tropical Atlantic to the Indo-Pacific region from inter-annual to centennial time scales will be reviewed. Identified teleconnections and hypotheses on mechanisms at work are reviewed and further explored in a century-long pacemaker coupled ocean-atmosphere simulation ensemble. There is a substantial impact of the tropical Atlantic on the Pacific region at inter-annual time scales. An Atlantic Niño (Niña event leads to rising (sinking motion in the Atlantic region, which is compensated by sinking (rising motion in the central-western Pacific. The sinking (rising motion in the central-western Pacific induces easterly (westerly surface wind anomalies just to the west, which alter the thermocline. These perturbations propagate eastward as upwelling (downwelling Kelvin-waves, where they increase the probability for a La Niña (El Niño event. Moreover, tropical North Atlantic sea surface temperature anomalies are also able to lead La Niña/El Niño development. At multidecadal time scales, a positive (negative Atlantic Multidecadal Oscillation leads to a cooling (warming of the eastern Pacific and a warming (cooling of the western Pacific and Indian Ocean regions. The physical mechanism for this impact is similar to that at inter-annual time scales. At centennial time scales, the Atlantic warming induces a substantial reduction of the eastern Pacific warming even under CO2 increase and to a strong subsurface cooling.

  7. Tropopause referenced ozone climatology and inter-annual variability (1994–2003 from the MOZAIC programme

    Directory of Open Access Journals (Sweden)

    Thouret

    2006-01-01

    Full Text Available The MOZAIC programme collects ozone and water vapour data using automatic equipment installed on board five long-range Airbus A340 aircraft flying regularly all over the world since August 1994. Those measurements made between September 1994 and August 1996 allowed the first accurate ozone climatology at 9–12 km altitude to be generated. The seasonal variability of the tropopause height has always provided a problem when constructing climatologies in this region. To remove any signal from the seasonal and synoptic scale variability in tropopause height we have chosen in this further study of these and subsequent data to reference our climatology to the altitude of the tropopause. We define the tropopause as a mixing zone 30 hPa thick across the 2 pvu potential vorticity surface. A new ozone climatology is now available for levels characteristic of the upper troposphere (UT and the lower stratosphere (LS regardless of the seasonal variations of the tropopause over the period 1994–2003. Moreover, this new presentation has allowed an estimation of the monthly mean climatological ozone concentration at the tropopause showing a sine seasonal variation with a maximum in May (120 ppbv and a minimum in November (65 ppbv. Besides, we present a first assessment of the inter-annual variability of ozone in this particular critical region. The overall increase in the UTLS is about 1%/yr for the 9 years sampled. However, enhanced concentrations about 10–15 % higher than the other years were recorded in 1998 and 1999 in both the UT and the LS. This so-called '1998–1999 anomaly' may be attributed to a combination of different processes involving large scale modes of atmospheric variability, circulation features and local or global pollution, but the most dominant one seems to involve the variability of the North Atlantic Oscillation (NAO as we find a strong positive correlation (above 0.60 between ozone recorded in the upper troposphere and the NAO

  8. Quantification of Impact of Orbital Drift on Inter-Annual Trends in AVHRR NDVI Data

    Directory of Open Access Journals (Sweden)

    Jyoteshwar R. Nagol

    2014-07-01

    Full Text Available The Normalized Difference Vegetation Index (NDVI time-series data derived from Advanced Very High Resolution Radiometer (AVHRR have been extensively used for studying inter-annual dynamics of global and regional vegetation. However, there can be significant uncertainties in the data due to incomplete atmospheric correction and orbital drift of the satellites through their active life. Access to location specific quantification of uncertainty is crucial for appropriate evaluation of the trends and anomalies. This paper provides per pixel quantification of orbital drift related spurious trends in Long Term Data Record (LTDR AVHRR NDVI data product. The magnitude and direction of the spurious trends was estimated by direct comparison with data from MODerate resolution Imaging Spectrometer (MODIS Aqua instrument, which has stable inter-annual sun-sensor geometry. The maps show presence of both positive as well as negative spurious trends in the data. After application of the BRDF correction, an overall decrease in positive trends and an increase in number of pixels with negative spurious trends were observed. The mean global spurious inter-annual NDVI trend before and after BRDF correction was 0.0016 and −0.0017 respectively. The research presented in this paper gives valuable insight into the magnitude of orbital drift related trends in the AVHRR NDVI data as well as the degree to which it is being rectified by the MODIS BRDF correction algorithm used by the LTDR processing stream.

  9. Atmospheric forcing controlling inter-annual nutrient dynamics in the open Gulf of Finland

    Science.gov (United States)

    Lehtoranta, Jouni; Savchuk, Oleg P.; Elken, Jüri; Dahlbo, Kim; Kuosa, Harri; Raateoja, Mika; Kauppila, Pirkko; Räike, Antti; Pitkänen, Heikki

    2017-07-01

    The loading of P into the Gulf of Finland has decreased markedly, but no overall trend in the concentration of P has been observed in the open Gulf, where the concentrations of both inorganic N and P still have a pronounced inter-annual variability. Our main aim was to study whether the internal processes driven by atmospheric forcing can explain the variation in the nutrient conditions in the Gulf during the period 1992-2014. We observed that the long-term salinity variation of the bottom water in the northern Baltic Proper controls that in the Gulf, and that the deep-water concentrations of oxygen and nutrients are significantly correlated between the basins. This imposes preconditions regarding how atmospheric forcing may influence deep water flows and stratification in the Gulf on a long-term scale. We found that over short timescales, winter winds in particular can control the in- and outflows of water and the vertical stratification and mixing, which to a large extent explained the inter-annual variation in the DIN and TP pools in the Gulf. We conclude that the inter-annual variation in the amounts, ratios, and spatial distribution of nutrients sets variable preconditions for the spring and potential blue-green algae blooms, and that internal processes were able to mask the effects of the P load reductions implemented across the whole Gulf. The transportation of P along the bottom from the northern Baltic Proper and its evident uplift in the Gulf highlights the fact that the nutrient reductions are also needed in the entire catchment of the Baltic Sea to improve the trophic status of the open Gulf.

  10. Seasonal and inter-annual turbidity variability in the Río de la Plata from 15 years of MODIS: El Niño dilution effect

    Science.gov (United States)

    Dogliotti, A. I.; Ruddick, K.; Guerrero, R.

    2016-12-01

    Spatio-temporal variability of turbidity in the Río de la Plata (RdP) estuary (Argentina) at seasonal and inter-annual timescales is analyzed from 15 years (2000-2014) of MODIS data and explained in terms of river discharges and the El Niño Southern Oscillation (ENSO). Satellite estimates were first validated using in situ turbidity measurements and then the time series of monthly averages were analyzed to assess the seasonal and inter-annual variability of turbidity. A strong seasonal variability was found in the upper and middle estuary with high turbidity from March to May and low turbidity from June to January. It was found that this variability is highly correlated to the seasonal cycle of the water discharge of the Bermejo river with a one-month delay between its peak and turbidity in the upper RdP estuary. On inter-annual time scales the influence of ENSO shows low turbidity amplitudes in the upper and middle estuary during moderate El Niño years, while the opposite pattern is observed in some La Niña years. A dilution effect during El Niño years is observed given that the main tributaries, which provide ∼92% of the liquid discharge, show water discharge increases due to excess in rain, while the Bermejo river, which provides ∼70% of the solid discharge and only 2% of the liquid discharge to the RdP, does not show this inter-decadal periodicity. In turn, increased turbidities are observed when negative RdP water discharge anomalies occurred, but this is not always related to La Niña events, since these events are not the only predictor for drought in this region.

  11. Influence of inter-annual environmental variability on chrysophyte cyst assemblages: insight from a 2-years sediment trap study in lakes from northern Poland

    Directory of Open Access Journals (Sweden)

    Iván Hernández-Almeida

    2017-02-01

    Full Text Available Quantitative paleonvironmental studies using transfer functions are developed from training sets. However, changes in some variables (e.g., climatic can be difficult to identify from short-term monitoring (e.g., less than one year. Here, we present the study of the chrysophyte cyst assemblages from sediment traps deployed during two consecutive years (November 2011-November 2013 in 14 lakes from Northern Poland. The studied lakes are distributed along a W-E climatological gradient, with very different physical, chemical and morphological characteristics, and land-uses. Field surveys were carried out to recover the sediment trap material during autumn, along with the measurement of several environmental variables (nutrients, major water ions, conductivity, pH, dissolved oxygen and chlorophyll-a. During the study, one year experienced mild seasonal changes in air temperature (November 2011-November 2012; TS1, typical of oceanic climate, while the other year was characterized by colder winter and spring (November 2012-November 2013; TS2, and higher summer temperatures, more characteristic of continental climate. Other environmental variables (e.g., nutrients did not show great changes between both years. Multivariate statistical analyses (RDA and DCA were performed on individual TS1 and TS2 datasets. Water chemistry and nutrients (pH, TN and TP explained the largest portion of the variance of the chrysophyte data for the individual years. However, analyses of the combined TS1 and TS2 datasets show that strong changes between summer and autumn (warm period, ice-free period with thermal stratification and winter and spring (cold period, ice-cover period play the most important role in the inter-annual variability in the chrysophyte assemblages. We show how inter-annual sampling maximizes ecological gradients of interest, particularly in regions with large environmental diversity, and low climatic variability. This methodology could help to identify

  12. Micro-phytoplankton community structure in the coastal upwelling zone off Concepción (central Chile): Annual and inter-annual fluctuations in a highly dynamic environment

    Science.gov (United States)

    Anabalón, V.; Morales, C. E.; González, H. E.; Menschel, E.; Schneider, W.; Hormazabal, S.; Valencia, L.; Escribano, R.

    2016-12-01

    An intensification of upwelling-favorable winds in recent decades has been detected in some of the main eastern boundary current systems, especially at higher latitudes, but the response of coastal phytoplankton communities in the Humboldt Current System (HCS) remains unknown. At higher latitudes in the HCS (35-40°S), strong seasonality in wind-driven upwelling during spring-summer coincides with an annual increase in coastal chlorophyll-a and primary production, and a dominance of micro-phytoplankton. In order to understand the effects of potential upwelling intensification on the micro-phytoplankton community in this region, annual and inter-annual variability in its structure (total and taxa-specific abundance and biomass) and its association with oceanographic fluctuations were analyzed using in situ time series data (2002-2009) from a shelf station off Concepcion (36.5°S). At the annual scale, total mean abundance and biomass, attributed to a few dominant diatom taxa, were at least one order of magnitude greater during spring-summer than autumn-winter, in association with changes in upwelling and surface salinity and temperature, whereas macro-nutrient concentrations remained relatively high all the year. At the inter-annual scale, total abundance and biomass decreased during the upwelling season of the 2006-2009 period compared with the 2002-2006 period, notably due to lower abundances of Skeletonema and Leptocylindrus, but the relative dominance of a few taxa was maintained. The 2006-2009 period was characterized by higher upwelling intensity, colder and higher salinity waters, and changes in nutrient concentrations and ratios compared with the first period. The inter-annual changes in the micro-phytoplankton community were mostly associated with changes in surface salinity and temperature (changes in upwelling intensity) but also with changes in Si/N and N/P, which relate to other land-derived processes.

  13. Inter-annual variation of carbon uptake by a plantation oak woodland in south-eastern England

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    M. Wilkinson

    2012-12-01

    Full Text Available The carbon balance of an 80-yr-old deciduous oak plantation in the temperate oceanic climate of the south-east of Great Britain was measured by eddy covariance over 12 yr (1999–2010. The mean annual net ecosystem productivity (NEP was 486 g C m−2 yr−1 (95% CI of ±73 g C m−2 yr−1, and this was partitioned into a gross primary productivity (GPP of 2034 ± 145 g C m−2 yr−1, over a 165 (±6 day growing season, and an annual loss of carbon through respiration and decomposition (ecosystem respiration, Reco of 1548 ± 122 g C m−2 yr−1. Although the maximum variation of NEP between years was large (333 g C m−2 yr−1, the ratio of Reco/GPP remained relatively constant (0.76 ± 0.02 CI. Some anomalies in the annual patterns of the carbon balance could be linked to particular weather events, such as low summer solar radiation and low soil moisture content (values below 30% by volume. The European-wide heat wave and drought of 2003 did not reduce the NEP of this woodland because of good water supply from the surface-water gley soil. The inter-annual variation in estimated intercepted radiation only accounted for ~ 47% of the variation in GPP, although a significant relationship (p < 0.001 was found between peak leaf area index and annual GPP, which modified the efficiency with which incident radiation was used in net CO2 uptake. Whilst the spring start and late autumn end of the net CO2 uptake period varied substantially (range of 24 and 27 days respectively, annual GPP was not related to growing season length. Severe outbreaks of defoliating moth caterpillars, mostly Tortrix viridana L. and Operophtera brumata L., caused considerable damage to the forest canopy in 2009 and 2010, resulting in reduced GPP in these two years. Inter-annual variation in

  14. Seasonal and inter-annual variability of lower stratospheric age of air spectra

    Science.gov (United States)

    Ploeger, Felix; Birner, Thomas

    2016-08-01

    Trace gas transport in the lower stratosphere is investigated by analysing seasonal and inter-annual variations of the age of air spectrum - the probability distribution of stratospheric transit times. Age spectra are obtained using the Chemical Lagrangian Model of the Stratosphere (CLaMS) driven by ERA-Interim winds and total diabatic heating rates, and using a time-evolving boundary-impulse-response (BIER) method based on multiple tracer pulses. Seasonal age spectra show large deviations from an idealized stationary uni-modal shape. Multiple modes emerge in the spectrum throughout the stratosphere, strongest at high latitudes, caused by the interplay of seasonally varying tropical upward mass flux, stratospheric transport barriers and recirculation. Inter-annual variations in transport (e.g. quasi-biennial oscillation) cause significant modulations of the age spectrum shape. In fact, one particular QBO phase may determine the spectrum's mode during the following 2-3 years. Interpretation of the age spectrum in terms of transport contributions due to the residual circulation and mixing is generally not straightforward. It turns out that advection by the residual circulation represents the dominant pathway in the deep tropics and in the winter hemisphere extratropics above 500 K, controlling the modal age in these regions. In contrast, in the summer hemisphere, particularly in the lowermost stratosphere, mixing represents the most probable pathway controlling the modal age.

  15. Trend Change Detection in NDVI Time Series: Effects of Inter-Annual Variability and Methodology

    Science.gov (United States)

    Forkel, Matthias; Carvalhais, Nuno; Verbesselt, Jan; Mahecha, Miguel D.; Neigh, Christopher S.R.; Reichstein, Markus

    2013-01-01

    Changing trends in ecosystem productivity can be quantified using satellite observations of Normalized Difference Vegetation Index (NDVI). However, the estimation of trends from NDVI time series differs substantially depending on analyzed satellite dataset, the corresponding spatiotemporal resolution, and the applied statistical method. Here we compare the performance of a wide range of trend estimation methods and demonstrate that performance decreases with increasing inter-annual variability in the NDVI time series. Trend slope estimates based on annual aggregated time series or based on a seasonal-trend model show better performances than methods that remove the seasonal cycle of the time series. A breakpoint detection analysis reveals that an overestimation of breakpoints in NDVI trends can result in wrong or even opposite trend estimates. Based on our results, we give practical recommendations for the application of trend methods on long-term NDVI time series. Particularly, we apply and compare different methods on NDVI time series in Alaska, where both greening and browning trends have been previously observed. Here, the multi-method uncertainty of NDVI trends is quantified through the application of the different trend estimation methods. Our results indicate that greening NDVI trends in Alaska are more spatially and temporally prevalent than browning trends. We also show that detected breakpoints in NDVI trends tend to coincide with large fires. Overall, our analyses demonstrate that seasonal trend methods need to be improved against inter-annual variability to quantify changing trends in ecosystem productivity with higher accuracy.

  16. Explaining the inter-annual variability in the ecosystem fluxes of the Brasschaat Scots pine forest: 20 years of eddy flux and pollution monitoring

    Science.gov (United States)

    Horemans, Joanna; Roland, Marilyn; Janssens, Ivan; Ceulemans, Reinhart

    2017-04-01

    Because of their ecological and recreational value, the health of forest ecosystems and their response to global change and pollution are of high importance. At a number of EuroFlux and ICOS ecosystem sites in Europe - as the Brasschaat forest site - the measurements of ecosystem fluxes of carbon and other gases are combined with vertical profiles of air pollution within the framework of the ICP-Forest monitoring program. The Brasschaat forest is dominated by 80-year old Scots pines (Pinus sylvestris L.), and has a total area of about 150 ha. It is situated near an urban area in the Campine region of Flanders, Belgium and is characterized by a mean annual temperature of 9.8 °C and an annual rainfall of 830 mm. In this contribution we report on a long-term analysis (1996-2016) of the ecosystem carbon and water fluxes, the energy exchanges and the pollutant concentrations (ozone, NOx, NH3, SO2). Particular interest goes to the inter-annual variation of the carbon fluxes and the carbon allocation patterns. The impact of the long-term (aggregated) and the short-term variability in both the meteorological drivers and in the main tropospheric pollutants on the carbon fluxes is examined, as well as their mutual interactive effects and their potential memory effect. The effect of variability in the drivers during the phenological phases (seasonality) on the inter-annual variability of the fluxes is also examined. Basic statistical techniques as well as spectral analyses and data mining techniques are being used.

  17. Inter-annual variation in the response of leaf-out onset to soil moisture increase in a teak plantation in northern Thailand.

    Science.gov (United States)

    Yoshifuji, Natsuko; Igarashi, Yasunori; Tanaka, Nobuaki; Tanaka, Katsunori; Sato, Takanori; Tantasirin, Chatchai; Suzuki, Masakazu

    2014-11-01

    To understand the impact of inter-annual climate change on vegetation-atmosphere mass and energy exchanges, it has become necessary to explore changes in leaf-out onset in response to climatic fluctuations. We examined the response of leaf-out and transpiration onset dates to soil moisture in a teak plantation in northern Thailand based on a 12-year leaf area index and sap flow measurements. The date of leaf-out and transpiration onset varied between years by up to 40 days, and depended on the initial date when the relative extractable water in a soil layer of 0-0.6 m (Θ) was greater than 0.2 being consistent with our previous results. Our new finding is that the delay in leaf-out and transpiration onset relative to the initial date when Θ > 0.2 increases linearly as the initial date on which Θ > 0.2 becomes earlier. The delay spans about 20 days in years when Θ > 0.2 occurs in March (the late dry season)-much earlier than usual because of heavy pre-monsoon rainfalls-while there is little delay in years when Θ > 0.2 occurs in May. This delay indicates the influence of additional factors on leaf-out onset, which controls the delay in the response of leaf-out to soil moisture increase. The results increased our knowledge about the pattern and extent of the changes in leaf phenology that occur in response to the inter-annual climate variation in tropical regions, where, in particular, such research is needed.

  18. Inter-annual Variations of the Carbon Footprint in Beijing Tianjin and Hebei Agro-ecosystem

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    TIAN Zhi-hui

    2018-02-01

    Full Text Available Based on the integration of Beijing, Tianjin and Hebei, we investigated inter-annual changes in carbon footprint from 2005 to 2014 in the agro-ecosystem of suburban Beijing Tianjin and Hebei. Our findings indicated that:(1 Carbon sink decreased 6.6 percent annually. The average annual carbon storage amount was 4 855 000 tons, with food crops constituting the highest proportion;(2 Carbon emission in the system showed a gradually decreasing trend, with agricultural chemicals as significant contributors. The annual average carbon emission was 7 278 000 tons in the Beijing Tianjin and Hebei farmland ecosystem. The largest amount of carbon emissions came from agricultural chemicals, nitrogen(from fertilizerwas the biggest contributor;(3 The average carbon footprint was 1 612 000 hm2 in the Beijing Tianjin and Hebei farmland ecosystem and showed a decreasing trend along with an ecological surplus of carbon.

  19. Inter-annual variability in fossil-fuel CO2 emissions due to temperature anomalies

    Science.gov (United States)

    Bréon, F.-M.; Boucher, O.; Brender, P.

    2017-07-01

    It is well known that short-term (i.e. interannual) variations in fossil-fuel CO2 emissions are closely related to the evolution of the national economies. Nevertheless, a fraction of the CO2 emissions are linked to domestic and business heating and cooling, which can be expected to be related to the meteorology, independently of the economy. Here, we analyse whether the signature of the inter-annual temperature anomalies is discernible in the time series of CO2 emissions at the country scale. Our analysis shows that, for many countries, there is a clear positive correlation between a heating-degree-person index and the component of the CO2 emissions that is not explained by the economy as quantified by the gross domestic product (GDP). Similarly, several countries show a positive correlation between a cooling-degree-person (CDP) index and CO2 emissions. The slope of the linear relationship for heating is on the order of 0.5-1 kg CO2 (degree-day-person)-1 but with significant country-to-country variations. A similar relationship for cooling shows even greater diversity. We further show that the inter-annual climate anomalies have a small but significant impact on the annual growth rate of CO2 emissions, both at the national and global scale. Such a meteorological effect was a significant contribution to the rather small and unexpected global emission growth rate in 2014 while its contribution to the near zero emission growth in 2015 was insignificant.

  20. HOW STRONG IS THE RELATIONSHIP BETWEEN RAINFALL VARIABILITY AND CAATINGA PRODUCTIVITY? A CASE STUDY UNDER A CHANGING CLIMATE.

    Science.gov (United States)

    Salimon, Cleber; Anderson, Liana

    2017-05-22

    Despite the knowledge of the influence of rainfall on vegetation dynamics in semiarid tropical Brazil, few studies address and explore quantitatively the various aspects of this relationship. Moreover, Northeast Brazil is expected to have its rainfall reduced by as much as 60% until the end of the 21st Century, under scenario AII of the IPCC Report 2010. We sampled and analyzed satellite-derived monthly rainfall and a vegetation index data for 40 sites with natural vegetation cover in Paraíba State, Brazil from 2001 to 2012. In addition, the anomalies for both variables were calculated. Rainfall variation explained as much as 50% of plant productivity, using the vegetation index as a proxy, and rainfall anomaly explained 80% of the vegetation productivity anomaly. In an extreme dry year (2012), with 65% less rainfall than average for the period 2001-2012, the vegetation index decreased by 25%. If such decrease persists in a long term trend in rainfall reduction, this could lead to a disruption in this ecosystem functioning and the dominant vegetation could become even more xeric or desert-like, bringing serious environmental, social and economical impacts.

  1. Sensitivity of inter-annual variation of CO2 seasonal cycle at Mauna Loa to atmospheric transport

    International Nuclear Information System (INIS)

    Taguchi, Shoichi; Murayama, Shohei; Higuchi, Kaz

    2003-01-01

    Origins of the inter-annual variations of the Mauna Loa atmospheric CO 2 seasonal cycle related to atmospheric transport were examined using a global atmospheric transport model with prescribed land biota CO 2 source functions at 11 land sections. On average, the seasonal variation of atmospheric CO 2 at Mauna Loa is influenced mostly by the Siberian CO 2 flux, followed by temperate Asia and North America. The inter-annual variability of the seasonal cycle is caused mainly by the inter-annual variation in the transport of the Siberian signal to Mauna Loa. The characteristics of the simulated seasonal cycle and its inter-annual variability at Mauna Loa are found to be sensitive to the quality of the wind data used to drive the transport model. Implication of this result is that for studying a long-term variations of atmospheric transport a meteorological data set for driving an atmospheric transport model should be obtained from the same production procedure

  2. Inter-annual variations in wave spectral characteristics at a location off the central west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    SanilKumar, V.; Nair, M.A.

    The inter-annual variations in wave spectrum are examined based on the wave data measured at 9 m water depth off the central west coast of India from 2009 to 2012 using a wave rider buoy. The temporal variation of the spectral energy density over a...

  3. Intra-Seasonal Oscillation (ISO) of south Kerala rainfall during the ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    Time series of daily averaged rainfall of about 40 rain gauge stations of south Kerala, situated at the southern-most part of peninsular India between latitudes about 8◦N and 10◦N were subjected to Wavelet Analysis to study the Intra Seasonal Oscillation (ISO) in the rainfall and its inter- annual variability. Of the 128 days, ...

  4. Multi-tissue analyses reveal limited inter-annual and seasonal variation in mercury exposure in an Antarctic penguin community.

    Science.gov (United States)

    Brasso, Rebecka L; Polito, Michael J; Emslie, Steven D

    2014-10-01

    Inter-annual variation in tissue mercury concentrations in birds can result from annual changes in the bioavailability of mercury or shifts in dietary composition and/or trophic level. We investigated potential annual variability in mercury dynamics in the Antarctic marine food web using Pygoscelis penguins as biomonitors. Eggshell membrane, chick down, and adult feathers were collected from three species of sympatrically breeding Pygoscelis penguins during the austral summers of 2006/2007-2010/2011. To evaluate the hypothesis that mercury concentrations in penguins exhibit significant inter-annual variation and to determine the potential source of such variation (dietary or environmental), we compared tissue mercury concentrations with trophic levels as indicated by δ(15)N values from all species and tissues. Overall, no inter-annual variation in mercury was observed in adult feathers suggesting that mercury exposure, on an annual scale, was consistent for Pygoscelis penguins. However, when examining tissues that reflected more discrete time periods (chick down and eggshell membrane) relative to adult feathers, we found some evidence of inter-annual variation in mercury exposure during penguins' pre-breeding and chick rearing periods. Evidence of inter-annual variation in penguin trophic level was also limited suggesting that foraging ecology and environmental factors related to the bioavailability of mercury may provide more explanatory power for mercury exposure compared to trophic level alone. Even so, the variable strength of relationships observed between trophic level and tissue mercury concentrations across and within Pygoscelis penguin species suggest that caution is required when selecting appropriate species and tissue combinations for environmental biomonitoring studies in Antarctica.

  5. Seasonal and Inter-Annual Analysis of Chlorophyll-a and Inherent Optical Properties from Satellite Observations in the Inner and Mid-Shelves of the South of Buenos Aires Province (Argentina

    Directory of Open Access Journals (Sweden)

    Ana L. Delgado

    2015-09-01

    Full Text Available The aim of this study is to describe and understand the seasonal and inter-annual physical and biological dynamics of the inner and mid shelves of the Southwestern Buenos Aires Province (Argentina. We used chlorophyll-a (chl-a concentrations and inherent optical properties (IOPs, derived from ocean color products between 2002 and 2010, as a proxy for the physical and biological parameters of interest. This study focuses on the absorption by phytoplankton, aph(443, particulate backscattering, bbp(443, and absorption due to dissolved and particulate detrital matter, adg(443, and chl-a derived from a multiband quasi-analytical algorithm (QAA. A regionalization based on the coefficient of variation and the Census X-11 method were applied to define regions and to analyze the inter-annual and seasonal variability of the ocean color parameters, with regards to climate variability. The coastal zone presents the highest values of chl-a with two maxima in winter and autumn, while the mid-shelf shows a strong spring chl-a maximum. After 2009, all parameters under study shifted their seasonality and their magnitude changed over the entire area. In the coastal zone, mean values of aph(443 and bbp(443 increased, while in the mid-shelf, chl-a and aph(443 decreased. The observed inter-annual and seasonal behavior of the parameters is tightly related to climate variability of the study area.

  6. INTER-annual/decadal variability of the north Aegean Sea hydrodynamics over 1960-2000

    Directory of Open Access Journals (Sweden)

    V. VERVATIS

    2014-12-01

    Full Text Available Results from a high-resolution hindcast model experiment, supported by available observations, reveal an increasing salinity trend in the north Aegean during the Eastern Mediterranean Transient (EMT, largely controlled by increases in the flow rate and salinity of water masses of Levantine origin entering the domain through the Myconos-Ikaria strait as a response to an acceleration of the Aegean thermohaline cell. Changes in the Dardanelles inflow (increasing salinity and in the surface freshwater flux (increasing Evaporation-Precipitation, although both contribute to a higher salt content of the basin during the EMT, play a minor role in the inter-annual/decadal variability of the freshwater budget. A long-term decreasing temperature trend is observed from the 1960s to the early 1990s. It is superimposed on the salinity-preconditioning phase over the 1980s and early 1990s. Both signals are, concomitantly, favouring conditions for intense Dense Water Formation (DWF in the north Aegean Sea. In addition, the northward displacement of the Black Sea Water front over the EMT, leads to the expansion of convective cells towards the north and to higher formation rates associated with both colder and saltier surface waters.

  7. Inter-annual variations of CO2 observed by commercial airliner in the CONTRAIL project

    Science.gov (United States)

    Sawa, Yousuke; Machida, Toshinobu; Matsueda, Hidekazu; Niwa, Yosuke; Umezawa, Taku

    2016-04-01

    Since 2005, we have conducted an observation program for greenhouse gases using the passenger aircraft of the Japan Airlines named Comprehensive Observation Network for TRace gases by AIrLiner (CONTRAIL). Over the past 10 years, successful operation of Continuous CO2 Measuring Equipment (CME) has delivered more than 6 million in-situ CO2 data from about 12000 flights between Japan and Europe, Australia, North America, or Asia. The large number of CME data enable us to well characterize spatial distributions and seasonal changes of CO2 in wide regions of the globe especially the Asia-Pacific regions. While the mean growth rates for the past 10 years were about 2 ppm/year, large growth rates of about 3 ppm/year were found in the wide latitudinal bands from 30S to 70N from the second half of 2012 to the first half of 2013. The multiyear data sets have the potential to help understand the global/regional CO2 budget. One good example is the significant inter-annual difference in CO2 vertical profiles observed over Singapore between October 2014 and October 2015, which is attributable to the massive biomass burnings in Indonesia in 2015.

  8. Inter-annual sea level variability in the southern Gulf of Mexico (1966-1976)

    Science.gov (United States)

    Salas-de-León, David Alberto; Monreal-Gómez, María Adela; Salas-Monreal, David; Riveron-Enzastiga, Mayra Lorena; Sánchez-Santillan, Norma Leticia

    2006-04-01

    Hourly time series at seven locations throughout the southern Gulf of Mexico were used to calculate the trend and the inter-annual sea level. The sea level series from January 1966 to December 1976 were filtered using a Lanczos low pass filter to remove oscillations with periods smaller than one year. The results revealed a sea level increment of about 1.4 mm yr-1 from 1966 to 1976 in the southern Gulf of Mexico. The monthly sea level variability obtained after the trends were removed, presented a sea level setup during winter and a sea level depression in summer attributed to seasonal wind conditions. The horizontal representation of averaged sea level in the southern Gulf of Mexico presented a saddle critical point. The associated sea level slope indicated water accumulation at Ciudad Madero in the western side of the gulf and Coatzacoalcos in the southernmost station, and sea level depressions at Tuxpan and Progreso in the southwestern and southeastern side of the gulf, respectively. Nevertheless, one of the most intriguing result is the presence of a Kelvin wave with a two mode oscillation axis that goes from Progreso to Tuxpan.

  9. Millennium-scale crossdating and inter-annual climate sensitivities of standing California redwoods.

    Directory of Open Access Journals (Sweden)

    Allyson L Carroll

    Full Text Available Extremely decay-resistant wood and fire-resistant bark allow California's redwoods to accumulate millennia of annual growth rings that can be useful in biological research. Whereas tree rings of Sequoiadendron giganteum (SEGI helped formalize the study of dendrochronology and the principle of crossdating, those of Sequoia sempervirens (SESE have proven much more difficult to decipher, greatly limiting dendroclimatic and other investigations of this species. We overcame these problems by climbing standing trees and coring trunks at multiple heights in 14 old-growth forest locations across California. Overall, we sampled 1,466 series with 483,712 annual rings from 120 trees and were able to crossdate 83% of SESE compared to 99% of SEGI rings. Standard and residual tree-ring chronologies spanning up to 1,685 years for SESE and 1,538 years for SEGI were created for each location to evaluate crossdating and to examine correlations between annual growth and climate. We used monthly values of temperature, precipitation, and drought severity as well as summer cloudiness to quantify potential drivers of inter-annual growth variation over century-long time series at each location. SESE chronologies exhibited a latitudinal gradient of climate sensitivities, contrasting cooler northern rainforests and warmer, drier southern forests. Radial growth increased with decreasing summer cloudiness in northern rainforests and a central SESE location. The strongest dendroclimatic relationship occurred in our southernmost SESE location, where radial growth correlated negatively with dry summer conditions and exhibited responses to historic fires. SEGI chronologies showed negative correlations with June temperature and positive correlations with previous October precipitation. More work is needed to understand quantitative relationships between SEGI radial growth and moisture availability, particularly snowmelt. Tree-ring chronologies developed here for both redwood

  10. Inter-annual Variability in Tundra Phenology Captured with Digital Photography

    Science.gov (United States)

    Melendez, M.; Vargas, S. A.; Tweedie, C. E.

    2012-12-01

    The need to improve multi-scale phenological monitoring of arctic terrestrial ecosystems has been a persistent research challenge. Although there has been a range of advances in remote sensing capacities over the past decade, these present costly, and sometimes logistically challenging and technically demanding solutions for arctic terrestrial ecosystems. In this poster and undergraduate research project, we demonstrate how seasonal and inter-annual variability in landscape phenology can be derived for multiple tundra ecosystems using a low-cost and low-tech kite aerial photography (KAP) system that has been developed as a contribution to the US Arctic Observing Network. Seasonal landscape phenology was observed over the Networked Info-Mechanical Systems (NIMS) grids (2 x 50 meters) located in Barrow and Atqasuk, Alaska using imagery acquired with KAP and analyzed for a range of greenness indices. Preliminary results showed that the 2G-RB greenness index correlated the best with NDVI values calculated from ground based hyperspectral reflectance measurements. 2012 had the highest 2G-RB greenness index values for both Barrow and Atqasuk sites, which correlated well with NDVI values acquired from ground-based hyperspectral reflectance measurements. Wet vegetation types showed the most interannual variability at the Atqasuk site based on the 2G-RB greenness index while in Barrow the moist vegetation types showed the most interannual variability. These results show that vegetation indices similar to those acquired from hyperspectral remote sensing platforms can be derived using low-cost and low-tech techniques. Further analysis using these same techniques is required in order to link relatively small scale vegetation dynamics measured with KAP with those documented at large scales using satellite imagery.

  11. Particle size distribution function of photoelectric counter and closed volume aureole photometer (seasonal variations and inter-annual differences)

    Science.gov (United States)

    Polkin, Vas. V.; Polkin, Vik. V.; Panchenko, M. V.

    2017-11-01

    The results of atmospheric aerosol monitoring are discussed. We compare data of particle size distribution function, which are obtained by photoelectric counter, with inversion of data closed volume aureole photometer, that's allow us to measure the aureole scattering phase function in the range of angles 1.2-20 degrees at a wavelength of 650 nm. Seasonal variations and inter-annual differences collected from 2010 to 2015 years are analyzed and evaluated.

  12. Spatial and temporal changes in inter-annual and seasonal NDVI in the Qinling mountains of China

    Science.gov (United States)

    Wang, Tao; Lu, Ying

    2017-11-01

    As an important ecological barrier in central China, the Qinling Mountains have received more attention in response to global or regional climate change. Spatial and temporal changes of inter-annual and seasonal NDVI were analysed after extraction of the vegetation growth season, based on MODIS NDVI images and linear trend analysis. The results showed that: (1) the NDVI value and vegetation cover level of the Qinling Mountains were high. The NDVI showed significant annual and seasonal increases, in which the summer value contributed the most to the inter-annual value, followed by spring and autumn. In terms of the change trend, the NDVI showed a linear increase in annual and seasonal data, in which the spring growth rate contributed the most to the inter-annual value, followed by autumn and summer. (2) The spatial distribution of the linear change trend of the NDVI in the inter-annual and seasonal data was mainly increased, but the area of reduction was also large. The area of reduced NDVI was mainly distributed in the middle and western area with middle and high elevations, as well as urban neighbourhoods with intensive human activities, such as the Hanzhong basin, the Ankang basin, and the Shangluo basin. The rate of change in NDVI in human activity areas was higher than in the middle and higher elevation areas. The change may be driven by human activities in the former and by climate change in the latter. Monitoring of the vegetation ecological system in the Qinling Mountains should be strengthened to understand the change process, as well as to provide a scientific basis when making policies for regional ecological environmental protection.

  13. How does the terrestrial carbon exchange respond to inter-annual climatic variations? A quantification based on atmospheric CO2 data

    Science.gov (United States)

    Rödenbeck, Christian; Zaehle, Sönke; Keeling, Ralph; Heimann, Martin

    2018-04-01

    The response of the terrestrial net ecosystem exchange (NEE) of CO2 to climate variations and trends may crucially determine the future climate trajectory. Here we directly quantify this response on inter-annual timescales by building a linear regression of inter-annual NEE anomalies against observed air temperature anomalies into an atmospheric inverse calculation based on long-term atmospheric CO2 observations. This allows us to estimate the sensitivity of NEE to inter-annual variations in temperature (seen as a climate proxy) resolved in space and with season. As this sensitivity comprises both direct temperature effects and the effects of other climate variables co-varying with temperature, we interpret it as inter-annual climate sensitivity. We find distinct seasonal patterns of this sensitivity in the northern extratropics that are consistent with the expected seasonal responses of photosynthesis, respiration, and fire. Within uncertainties, these sensitivity patterns are consistent with independent inferences from eddy covariance data. On large spatial scales, northern extratropical and tropical inter-annual NEE variations inferred from the NEE-T regression are very similar to the estimates of an atmospheric inversion with explicit inter-annual degrees of freedom. The results of this study offer a way to benchmark ecosystem process models in more detail than existing effective global climate sensitivities. The results can also be used to gap-fill or extrapolate observational records or to separate inter-annual variations from longer-term trends.

  14. The climatic variability inter annual associated to El Nino - la Nina cycle, oscillation of the south and their effect in the pluviometric patron of Colombia

    International Nuclear Information System (INIS)

    Montealegre Bocanegra Jose Edgar; Pabon Caicedo, Jose Daniel

    2000-01-01

    In the present article we study the influence that on a year-to-year scale the interactions between the atmosphere and the Tropical North and South Atlantic, as well as the Pacific Ocean, have on the inter annual variability of the precipitation in Colombia. We identify and quantify the existing relations between the indexes of the macro-scale, characteristic of the inter annual variability of those oceans, and the indexes characteristic of the inter annual precipitation variability, for selected regions in Colombia. The determination of these relations is of fundamental importance in order to develop objective schemes, based on physic-statistical methods, aimed at predicting the climate in Colombia

  15. The influence of inter-annually varying albedo on regional climate and drought

    KAUST Repository

    Meng, Xianhong

    2013-05-05

    strengthening of the second mechanism. That is, the second mechanism is stronger in a drought year compared to a normal year and this difference is larger than for the first mechanism. When both mechanisms are active, the second mechanism tends to dominate across the model domain, particularly during the 2002 drought period. The introduction of observed inter-annual variations in albedo produces an enhancement of the first mechanism and a weakening of the second mechanism during the onset of the drought. © 2013 Springer-Verlag Berlin Heidelberg.

  16. Patterns and controls of inter-annual variability in the terrestrial carbon budget

    Directory of Open Access Journals (Sweden)

    B. Marcolla

    2017-08-01

    Full Text Available The terrestrial carbon fluxes show the largest variability among the components of the global carbon cycle and drive most of the temporal variations in the growth rate of atmospheric CO2. Understanding the environmental controls and trends of the terrestrial carbon budget is therefore essential to predict the future trajectories of the CO2 airborne fraction and atmospheric concentrations. In the present work, patterns and controls of the inter-annual variability (IAV of carbon net ecosystem exchange (NEE have been analysed using three different data streams: ecosystem-level observations from the FLUXNET database (La Thuile and 2015 releases, the MPI-MTE (model tree ensemble bottom–up product resulting from the global upscaling of site-level fluxes, and the Jena CarboScope Inversion, a top–down estimate of surface fluxes obtained from observed CO2 concentrations and an atmospheric transport model. Consistencies and discrepancies in the temporal and spatial patterns and in the climatic and physiological controls of IAV were investigated between the three data sources. Results show that the global average of IAV at FLUXNET sites, quantified as the standard deviation of annual NEE, peaks in arid ecosystems and amounts to  ∼  120 gC m−2 y−1, almost 6 times more than the values calculated from the two global products (15 and 20 gC m−2 y−1 for MPI-MTE and the Jena Inversion, respectively. Most of the temporal variability observed in the last three decades of the MPI-MTE and Jena Inversion products is due to yearly anomalies, whereas the temporal trends explain only about 15 and 20 % of the variability, respectively. Both at the site level and on a global scale, the IAV of NEE is driven by the gross primary productivity and in particular by the cumulative carbon flux during the months when land acts as a sink. Altogether these results offer a broad view on the magnitude, spatial patterns and environmental drivers of IAV

  17. Patterns and controls of inter-annual variability in the terrestrial carbon budget

    Science.gov (United States)

    Marcolla, Barbara; Rödenbeck, Christian; Cescatti, Alessandro

    2017-08-01

    The terrestrial carbon fluxes show the largest variability among the components of the global carbon cycle and drive most of the temporal variations in the growth rate of atmospheric CO2. Understanding the environmental controls and trends of the terrestrial carbon budget is therefore essential to predict the future trajectories of the CO2 airborne fraction and atmospheric concentrations. In the present work, patterns and controls of the inter-annual variability (IAV) of carbon net ecosystem exchange (NEE) have been analysed using three different data streams: ecosystem-level observations from the FLUXNET database (La Thuile and 2015 releases), the MPI-MTE (model tree ensemble) bottom-up product resulting from the global upscaling of site-level fluxes, and the Jena CarboScope Inversion, a top-down estimate of surface fluxes obtained from observed CO2 concentrations and an atmospheric transport model. Consistencies and discrepancies in the temporal and spatial patterns and in the climatic and physiological controls of IAV were investigated between the three data sources. Results show that the global average of IAV at FLUXNET sites, quantified as the standard deviation of annual NEE, peaks in arid ecosystems and amounts to ˜ 120 gC m-2 y-1, almost 6 times more than the values calculated from the two global products (15 and 20 gC m-2 y-1 for MPI-MTE and the Jena Inversion, respectively). Most of the temporal variability observed in the last three decades of the MPI-MTE and Jena Inversion products is due to yearly anomalies, whereas the temporal trends explain only about 15 and 20 % of the variability, respectively. Both at the site level and on a global scale, the IAV of NEE is driven by the gross primary productivity and in particular by the cumulative carbon flux during the months when land acts as a sink. Altogether these results offer a broad view on the magnitude, spatial patterns and environmental drivers of IAV from a variety of data sources that can be

  18. Landslides induced by heavy rainfall in July 2012 in Northern Kyushu District, Japan and the influence of long term rainfall increase comparing with the slope destabilization due to strong seismic shaking

    Science.gov (United States)

    Kubota, Tetsuya; Shinohara, Yoshinori; Aditian, Aril

    2013-04-01

    1. Objective We had a deluge in July 2012 in the northern Kyushu district with intense rainfall of 800mm and 108mm/hr. This intensity yielded countless traces of debris flow and landslides, slope failures that induced tremendous damage and causalities in the area. Hence, several field investigations and reconnaissance tasks were conducted to delve into this sediment-related disaster. The various results and the information obtained through this investigation were reported, mentioning the damage, the meteorological condition, geologic-geomorphologic features and hydraulic characteristics of the debris flows, vegetation effects, and the influence of the climate change. Increase in rainfall that may be induced by the global climate change is obvious in Kyushu district, Japan, according to the analysis of rain data observed in various locations including mountainside points that are not influenced by local warming due to urbanization. On this point of view, we are intrigued to elucidate the response of landslide to this increase in rainfall. Hence, its long term impact on this landslide disaster is also analyzed comparing with the slope destabilization due to strong seismic shaking. 2. Method and target areas Field investigation on landslides slopes, slope failures and torrents where debris flows occurred are conducted to obtain the geologic data, geo-structure, vegetation feature, soil samples and topographic data i.e. cross sections, then soil shear tests and soil permeability tests are also conducted. The rainfall data at the nearest rain observatory were obtained from the database of Japan meteorological agency. The long term impact on the slope stability at some slopes in the area is analyzed by the finite element method (FEM) combined with rain infiltration and seepage analysis with the long term rainfall fluctuation data, obtaining factor of safety ( Fs) on real landslide slopes. The results are compared with the destabilized influence on the slopes due to the

  19. A neural network-based estimate of the seasonal to inter-annual variability of the Atlantic Ocean carbon sink

    Science.gov (United States)

    Landschützer, P.; Gruber, N.; Bakker, D. C. E.; Schuster, U.; Nakaoka, S.; Payne, M. R.; Sasse, T.; Zeng, J.

    2013-05-01

    equator (-0.007 Pg C yr-1 decade-1). Surface ocean pCO2 was also increasing less than that of the atmosphere over most of the Atlantic south of the equator, leading to a substantial trend toward a stronger CO2 sink for the entire South Atlantic (-0.14 Pg C yr-1 decade-1). The Atlantic carbon sink varies relatively little on inter-annual time-scales (±0.04 Pg C yr-1; 1σ).

  20. The impact of inter-annual variability of annual cycle on long-term memory in long historical temperature records

    Science.gov (United States)

    Deng, Qimin; Fu, Zuntao

    2017-04-01

    Changes in the estimation of long-term correlation induced by inter-annual variability of annual cycle have been investigated by means of detrended fluctuation analysis (DFA). In a consequence of the intrinsic nonlinearity of the climate system, the annual cycle suffers from both amplitude and phase fluctuations. How does this changing annual cycle affect the fluctuation of temperature anomalies? A recently developed adaptive data analysis tool, the Nonlinear Mode Decomposition (NMD), is used to extract and remove time-varying annual cycle. We compared the differences of the long-term correlation calculated by removing different annual cycle, time-varying and stationary. The study was based on long historical temperature records around the North Atlantic Ocean. The traditional climatology annual cycle which lack characteristic of inter-annual fluctuation would lead to: (1) the estimation of Hurst exponent (2) how to choose scaling range and (3) the goodness of fit. Especially removing steady climatology annual cycle would introduce an artificial crossover around one-year period in the DFA curve. The conclusion is verified by generating deterministic time series through Monte Carlo simulations.

  1. Localised residency and inter-annual fidelity to coastal foraging areas may place sea bass at risk to local depletion.

    Science.gov (United States)

    Doyle, Thomas K; Haberlin, Damien; Clohessy, Jim; Bennison, Ashley; Jessopp, Mark

    2017-04-04

    For many marine migratory fish, comparatively little is known about the movement of individuals rather than the population. Yet, such individual-based movement data is vitally important to understand variability in migratory strategies and fidelity to foraging locations. A case in point is the economically important European sea bass (Dicentrarchus labrax L.) that inhabits coastal waters during the summer months before migrating offshore to spawn and overwinter. Beyond this broad generalisation we have very limited information on the movements of individuals at coastal foraging grounds. We used acoustic telemetry to track the summer movements and seasonal migrations of individual sea bass in a large tidally and estuarine influenced coastal environment. We found that the vast majority of tagged sea bass displayed long-term residency (mean, 167 days) and inter-annual fidelity (93% return rate) to specific areas. We describe individual fish home ranges of 3 km or less, and while fish clearly had core resident areas, there was movement of fish between closely located receivers. The combination of inter-annual fidelity to localised foraging areas makes sea bass very susceptible to local depletion; however, the designation of protected areas for sea bass may go a long way to ensuring the sustainability of this species.

  2. Inter-annual variabilities in biogeophysical feedback of terrestrial ecosystem to atmosphere using a land surface model

    Science.gov (United States)

    Seo, C.; Hong, S.; Jeong, H. M.; Jeon, J.

    2017-12-01

    Biogeophysical processes of terrestrial ecosystem such as water vapor and energy flux are the key features to understand ecological feedback to atmospheric processes and thus role of terrestrial ecosystem in climate system. For example, it has been recently known that the ecological feedback through water vapor and energy flux results in regulating regional weathers and climates which is one of the fundamental functions of terrestrial ecosystem. In regional scale, water vapor flux has been known to give negative feedback to atmospheric warming, while energy flux from the surface has been known to positive feedback. In this study, we explored the inter-annual variabilities in these two biogeophysical features to see how the climate regulating functions of terrestrial ecosystem have been changed with climate change. We selected a land surface model involving vegetation dynamics that is forced by atmospheric data from NASA including precipitation, temperature, wind, surface pressure, humidity, and incoming radiations. From the land surface model, we simulated 60-year water vapor and energy fluxes from 1961 to 2010, and calculates feedbacks of terrestrial ecosystem as in radiation amount into atmosphere. Then, we analyzed the inter-annual variabilities in the feedbacks. The results showed that some mid-latitude areas showing very high variabilities in precipitation showed higher positive feedback and/or lower negative feedback. These results suggest deterioration of the biogeophyisical factor of climate regulating function over those regions.

  3. Inter-annual precipitation variabiity inferred from late Holocene speleothem records from Fiji: implications for SPCZ localisation and ENSO behaviour

    Science.gov (United States)

    Mattey, D.; Stephens, M.; Hoffmann, D.; Brett, M.

    2015-12-01

    The modern tropical Fiji climate is characterised by seasonal rainfall controlled by the position of the South Pacific Convergence Zone (SPCZ). Interannual rainfall is strongly modulated on decadal timescales by ENSO with higher rainfall associated with La Nina events. Voli Voli cave near Sigatoga (Viti Levu) is a stream passage that has been monitored since 2009. A U-Th dated laminated speleothem spans a 1500 year interval across the transition from the Medieval Warm Period into the Little Ice Age marked by a fabric change from finely laminated calcite with thin clay layers, to white well-laminated calcite. The older record is characterised by rising δ13C values followed by a rapid decrease in δ13C around 1200 AD. Evidence from cave monitoring shows that cave air CO2 levels are strongly seasonal as a result of greater ventilation by winter trade winds and high resolution δ13C record shows regularly spaced peaks correlated with paired laminae and cycles in P and S which provide annual markers driven by rainfall and seasonal ventilation. δ18O values remain relatively unchanged throughout the record but micromilling at sub-annual resolution reveals systematic cycles in δ18O that span groups of paired laminae with an inferred periodicity of 3-7 years i.e. a similar frequency to modern ENSO. The presence of these sub-decadal cycles in δ18O may be a result of a combination of factors. The amplitude of 2-3‰ would be equivalent to an amount-effect related change in annual precipitation of around 50% but an additional smoothing process, perhaps a result of aquifer storage, is required to attenuate interannual variance in precipitation. The Voli Voli record provides evidence of an underlying climatic change to more frequent La Niña conditions from 1200 AD and may be associated with increased conflict, shifts in settlements and changes in subsistence strategies on the island. Coeval speleothem isotope records from tropical Pacific Islands provide a provide a

  4. Inter-annual Variations in Snow/Firn Density over the Greenland Ice Sheet by Combining GRACE gravimetry and Envisat Altimetry

    Science.gov (United States)

    Su, X.; Shum, C. K.; Guo, J.; Howat, I.; Jezek, K. C.; Luo, Z.; Zhou, Z.

    2017-12-01

    Satellite altimetry has been used to monitor elevation and volume change of polar ice sheets since the 1990s. In order to derive mass change from the measured volume change, different density assumptions are commonly used in the research community, which may cause discrepancies on accurately estimating ice sheets mass balance. In this study, we investigate the inter-annual anomalies of mass change from GRACE gravimetry and elevation change from Envisat altimetry during years 2003-2009, with the objective of determining inter-annual variations of snow/firn density over the Greenland ice sheet (GrIS). High positive correlations (0.6 or higher) between these two inter-annual anomalies at are found over 93% of the GrIS, which suggests that both techniques detect the same geophysical process at the inter-annual timescale. Interpreting the two anomalies in terms of near surface density variations, over 80% of the GrIS, the inter-annual variation in average density is between the densities of snow and pure ice. In particular, at the Summit of Central Greenland, we validate the satellite data estimated density with the in situ data available from 75 snow pits and 9 ice cores. This study provides constraints on the currently applied density assumptions for the GrIS.

  5. Assessing the Change in Rainfall Characteristics and Trends for the Southern African ITCZ Region

    Science.gov (United States)

    Baumberg, Verena; Weber, Torsten; Helmschrot, Jörg

    2015-04-01

    Southern Africa is strongly influenced by the movement and intensity of the Intertropical Convergence Zone (ITCZ) thus determining the climate in this region with distinct seasonal and inter-annual rainfall dynamics. The amount and variability of rainfall affect the various ecosystems by controlling the hydrological system, regulating water availability and determining agricultural practices. Changes in rainfall characteristics potentially caused by climate change are of uppermost relevance for both ecosystem functioning and human well-being in this region and, thus, need to be investigated. To analyse the rainfall variability governed by the ITCZ in southern Africa, observational daily rainfall datasets with a high spatial resolution of 0.25° x 0.25° (about 28 km x 28 km) from satellite-based Tropical Rainfall Measuring Mission (TRMM) and Global Land Data Assimilation System (GLDAS) are used. These datasets extend from 1998 to 2008 and 1948 to 2010, respectively, and allow for the assessment of rainfall characteristics over different spatial and temporal scales. Furthermore, a comparison of TRMM and GLDAS and, where available, with observed data will be made to determine the differences of both datasets. In order to quantify the intra- and inner-annual variability of rainfall, the amount of total rainfall, duration of rainy seasons and number of dry spells along with further indices are calculated from the observational datasets. Over the southern African ITCZ region, the rainfall characteristics change moving from wetter north to the drier south, but also from west to east, i.e. the coast to the interior. To address expected spatial and temporal variabilities, the assessment of changes in the rainfall parameters will be carried out for different transects in zonal and meridional directions over the region affected by the ITCZ. Revealing trends over more than 60 years, the results will help to identify and understand potential impacts of climate change on

  6. Using Decision Trees to Examine Relationships between Inter-Annual Vegetation Variability, Topographic Attributes, and Climate Signals

    Science.gov (United States)

    White, A. B.; Kumar, P.

    2003-12-01

    The objective of this research is to develop KDD (knowledge discovery in databases) techniques for spatio-temporal geo-data, and use these techniques to examine inter-annual vegetation health signals. The underlying hypothesis of the research is that the signatures of inter-annual variability of climate on vegetation dynamics as represented by the statistical descriptors of vegetation index variations depend upon a variety of attributes related to the topography, hydrology, physiography, and climate. NDVI (normalized differential vegetation index) is enlisted to represent vegetation health and relationships between this index and topographic attributes such as elevation, slope, aspect, compound topographic index (CTI), and the proximity to a stream, are analyzed. Several scientific questions related to the identification and characterization of the inter-annual variability ensue as a consequence of our hypothesis. Investigations were performed using 13 years of 1-km resolution NDVI data from the AVHRR instrument on NOAA's POES (polar-orbiting operational environmental satellite) over the continental U.S. Various temporal change indices were used in order to identify anomalous inter-annual behavior in the NDVI index, including maximum absolute and relative deviations from the 13-year mean and positive and negative persistence indices (after Zhou et al., 2001). The KDD technique used in this research is the decision tree, which falls under the classification and prediction division of data mining techniques. The algorithm is similar to c4.5 and id3, but can handle continuous input and output values without binning and is optimized to determine the minimum error. Future work will incorporate clustering algorithms (both distance and density-based) and association rule algorithms (constraint-based) adapted for spatial-temporal data. Investigations will also be performed at smaller spatial scales, integrating higher resolution data. Throughout the growing season

  7. Seasonal and inter-annual temperature variability in the bottom waters over the western Black Sea shelf

    Directory of Open Access Journals (Sweden)

    G. I. Shapiro

    2011-09-01

    Full Text Available Long-term changes in the state of the Bottom Shelf Water (BSW on the Western shelf of the Black Sea are assessed using analysis of intra-seasonal and inter-annual temperature variations. For the purpose of this study the BSW is defined as such shelf water mass between the seabed and the upper mixed layer (bounded by the σθ = 14.2 isopycnal which has limited ability to mix vertically with oxygen-rich surface waters during the warm season due to formation of a seasonal pycnocline. A long-term time series of temperature anomalies in the BSW is constructed from in-situ observations taken over the 2nd half of the 20th century. The BSW is shown to occupy nearly half of the shelf area during the summer stratification period (May–November.The results reveal a warm phase in the 1960s/70s, followed by a cold phase between 1985 and 1995 and a further warming after 1995. The transition between the warm and cold periods coincides with a regime shift in the Black Sea ecosystem. While it was confirmed that the memory of winter convection is well preserved over the following months in the deep sea, the signal of winter cooling in the BSW significantly reduces during the warm season. The potential of the BSW to ventilate horizontally during the warm season with the deep-sea waters is assessed using isopycnic analysis of temperature variations. It is shown that temperature in the BSW is stronger correlated with the temperature of Cold Intermediate Waters (CIW in the deep sea than with the severity of the previous winters, thus indicating that the isopycnal exchanges with the deep sea are more important for inter-annual/inter-decadal variability of the BSW on the western Black Sea shelf than effects of winter convection on the shelf itself.

  8. Hydrological niche separation explains seasonal and inter-annual variations of vegetation dynamics in seasonally dry tropical forests

    Science.gov (United States)

    Xu, X.; Medvigy, D.; Powers, J. S.; Becknell, J. M.; Guan, K.

    2015-12-01

    Despite ample water supply, vegetation dynamics are subject to seasonal water stress in large fraction of tropical forests. These seasonally dry tropical forests (SDTFs) account for over 40% of tropical forests, harbor high biodiversity, have large potential carbon sink due to forest recovery from human disturbance and also play a critical role in global carbon budget and inter-annual variations. Plants in this biome display notably diverse responses to seasonal and inter-annual variations of water availability, especially inter-specific variations in canopy seasonality and biomass growth. Current process-based dynamic vegetation models cannot represent these diversities and are shown to perform poorly on simulating drought responses of tropical forests, calling into question of their ability to accurately simulate future changes in SDTFs. Accumulated field observations, suggest that hydrological niche separation driven by coordinated plant functional traits is associated with plants' performance under drought. Yet, it remains not clear whether the physiology-level hydrological niche separation can explain the ecosystem-level diversity observed in SDTFs. Here, we test the theory with a model-data fusion approach. We implemented a new plant hydrodynamic module that is able to track leaf water potential at sub-daily scale in ED2 model. We further incorporated a hydrological niche separation scheme based on a meta-data analysis of key functional traits in SDTFs. Simulated ecological patterns with and without hydrological niche separation were then compared with remote-sensing and long-term field observations from an SDTF site in Palo Verde, Costa Rica. Using several numerical experiments, we specifically examine the following questions: (i) Whether hydrological niche separation can explain the diversity in canopy seasonality and biomass growth? (ii) How important are the yet uncertain belowground functional traits, especially root profile in determining canopy

  9. Estimating inter-annual variability in winter wheat sowing dates from satellite time series in Camargue, France

    Science.gov (United States)

    Manfron, Giacinto; Delmotte, Sylvestre; Busetto, Lorenzo; Hossard, Laure; Ranghetti, Luigi; Brivio, Pietro Alessandro; Boschetti, Mirco

    2017-05-01

    Crop simulation models are commonly used to forecast the performance of cropping systems under different hypotheses of change. Their use on a regional scale is generally constrained, however, by a lack of information on the spatial and temporal variability of environment-related input variables (e.g., soil) and agricultural practices (e.g., sowing dates) that influence crop yields. Satellite remote sensing data can shed light on such variability by providing timely information on crop dynamics and conditions over large areas. This paper proposes a method for analyzing time series of MODIS satellite data in order to estimate the inter-annual variability of winter wheat sowing dates. A rule-based method was developed to automatically identify a reliable sample of winter wheat field time series, and to infer the corresponding sowing dates. The method was designed for a case study in the Camargue region (France), where winter wheat is characterized by vernalization, as in other temperate regions. The detection criteria were chosen on the grounds of agronomic expertise and by analyzing high-confidence time-series vegetation index profiles for winter wheat. This automatic method identified the target crop on more than 56% (four-year average) of the cultivated areas, with low commission errors (11%). It also captured the seasonal variability in sowing dates with errors of ±8 and ±16 days in 46% and 66% of cases, respectively. Extending the analysis to the years 2002-2012 showed that sowing in the Camargue was usually done on or around November 1st (±4 days). Comparing inter-annual sowing date variability with the main local agro-climatic drivers showed that the type of preceding crop and the weather conditions during the summer season before the wheat sowing had a prominent role in influencing winter wheat sowing dates.

  10. Inter-annual cascade effect on marine food web: A benthic pathway lagging nutrient supply to pelagic fish stock.

    Directory of Open Access Journals (Sweden)

    Lohengrin Dias de Almeida Fernandes

    Full Text Available Currently, spatial and temporal changes in nutrients availability, marine planktonic, and fish communities are best described on a shorter than inter-annual (seasonal scale, primarily because the simultaneous year-to-year variations in physical, chemical, and biological parameters are very complex. The limited availability of time series datasets furnishing simultaneous evaluations of temperature, nutrients, plankton, and fish have limited our ability to describe and to predict variability related to short-term process, as species-specific phenology and environmental seasonality. In the present study, we combine a computational time series analysis on a 15-year (1995-2009 weekly-sampled time series (high-resolution long-term time series, 780 weeks with an Autoregressive Distributed Lag Model to track non-seasonal changes in 10 potentially related parameters: sea surface temperature, nutrient concentrations (NO2, NO3, NH4 and PO4, phytoplankton biomass (as in situ chlorophyll a biomass, meroplankton (barnacle and mussel larvae, and fish abundance (Mugil liza and Caranx latus. Our data demonstrate for the first time that highly intense and frequent upwelling years initiate a huge energy flux that is not fully transmitted through classical size-structured food web by bottom-up stimulus but through additional ontogenetic steps. A delayed inter-annual sequential effect from phytoplankton up to top predators as carnivorous fishes is expected if most of energy is trapped into benthic filter feeding organisms and their larval forms. These sequential events can explain major changes in ecosystem food web that were not predicted in previous short-term models.

  11. Twenty years of high-resolution sea surface temperature imagery around Australia: inter-annual and annual variability.

    Science.gov (United States)

    Foster, Scott D; Griffin, David A; Dunstan, Piers K

    2014-01-01

    The physical climate defines a significant portion of the habitats in which biological communities and species reside. It is important to quantify these environmental conditions, and how they have changed, as this will inform future efforts to study many natural systems. In this article, we present the results of a statistical summary of the variability in sea surface temperature (SST) time-series data for the waters surrounding Australia, from 1993 to 2013. We partition variation in the SST series into annual trends, inter-annual trends, and a number of components of random variation. We utilise satellite data and validate the statistical summary from these data to summaries of data from long-term monitoring stations and from the global drifter program. The spatially dense results, available as maps from the Australian Oceanographic Data Network's data portal (http://www.cmar.csiro.au/geonetwork/srv/en/metadata.show?id=51805), show clear trends that associate with oceanographic features. Noteworthy oceanographic features include: average warming was greatest off southern West Australia and off eastern Tasmania, where the warming was around 0.6°C per decade for a twenty year study period, and insubstantial warming in areas dominated by the East Australian Current, but this area did exhibit high levels of inter-annual variability (long-term trend increases and decreases but does not increase on average). The results of the analyses can be directly incorporated into (biogeographic) models that explain variation in biological data where both biological and environmental data are on a fine scale.

  12. Twenty years of high-resolution sea surface temperature imagery around Australia: inter-annual and annual variability.

    Directory of Open Access Journals (Sweden)

    Scott D Foster

    Full Text Available The physical climate defines a significant portion of the habitats in which biological communities and species reside. It is important to quantify these environmental conditions, and how they have changed, as this will inform future efforts to study many natural systems. In this article, we present the results of a statistical summary of the variability in sea surface temperature (SST time-series data for the waters surrounding Australia, from 1993 to 2013. We partition variation in the SST series into annual trends, inter-annual trends, and a number of components of random variation. We utilise satellite data and validate the statistical summary from these data to summaries of data from long-term monitoring stations and from the global drifter program. The spatially dense results, available as maps from the Australian Oceanographic Data Network's data portal (http://www.cmar.csiro.au/geonetwork/srv/en/metadata.show?id=51805, show clear trends that associate with oceanographic features. Noteworthy oceanographic features include: average warming was greatest off southern West Australia and off eastern Tasmania, where the warming was around 0.6°C per decade for a twenty year study period, and insubstantial warming in areas dominated by the East Australian Current, but this area did exhibit high levels of inter-annual variability (long-term trend increases and decreases but does not increase on average. The results of the analyses can be directly incorporated into (biogeographic models that explain variation in biological data where both biological and environmental data are on a fine scale.

  13. On the anatomy of nearshore sandbars : A systematic exposition of inter-annual sandbar dynamics

    NARCIS (Netherlands)

    Walstra, D.J.R.

    2016-01-01

    Nearshore sandbars have a lifetime of many years, during which they exhibit cyclic, offshore directed behaviour with strong alongshore coherence. A bar is generated near the shoreline and grows in height and width while migrating offshore, before finally decaying at the seaward limit of the surf

  14. Seasonal and inter-annual photosynthetic response of representative C4 species to soil water content and leaf nitrogen concentration across a tropical seasonal floodplain

    NARCIS (Netherlands)

    Mantlana, K.B.; Arneth, A.; Veenendaal, E.M.; Wohland, P.; Wolski, P.; Kolle, O.; Lloyd, J.

    2008-01-01

    We examined the seasonal and inter-annual variation of leaf-level photosynthetic characteristics of three C4 perennial species, Cyperus articulatus, Panicum repens and Imperata cylindrica, and their response to environmental variables, to determine comparative physiological responses of plants

  15. Seasonal and inter-annual variations of leaf-level photosynthesis and soil respiration in the representative ecosystems of the Okavango Delta, Botswana

    NARCIS (Netherlands)

    Mantlana, K.B.

    2008-01-01

    Seasonal and inter-annual leaf-level photosynthesis and soil respiration measurements were conducted in representative ecosystems of the Okavango Delta, Botswana, that differ in their long-term soil water content: the permanent swamp, the seasonal floodplain, the rain-fed grassland and the mopane

  16. The twentieth century Africal easterly waves in reanalysis systems and IPCC simulations, from intra-seasonal to inter-annual variability

    Energy Technology Data Exchange (ETDEWEB)

    Ruti, Paolo; Dell' Aquila, Alessandro [ENEA, CR Casaccia, UTMEA-CLIM, Rome (Italy)

    2010-11-15

    The nature of intraseasonal and interannual variability of African easterly waves (AEWs) in IPCC-CMIP3 global simulations is investigated in comparison with 40-year NCEP and ERA40 products. AEWs are a major source of atmospheric variability over the Sahel and particularly over West Africa. An accurate representation of AEWs dynamics is therefore an important precondition to skilled climate predictions and seasonal forecasts for this area. We describe the synoptic features of these disturbances and we illustrate a statistical link, at interannual timescale, between Sea Surface Temperature and AEWs activity. At intraseasonal time scale, the models exhibit a wide variety of behaviours in reproducing the synoptic features of the disturbances, namely AEWs amplitude and pattern. It is possible to classify the models into two groups, one localizing intense variability well inside the continental area, and the other exhibiting a weaker variance mostly placed over West Africa. Concerning the inter-annual variability, we point out a statistical link between SST anomalies and AEWs activity that reveals a strong influence of the ENSO events on the variability of the disturbances over the Guinean coasts. Warm/cold ENSO events occur in conjunction with suppressed/enhanced AEWs through upper tropospheric teleconnection bridge. Only two model running at significantly different vertical and horizontal resolution (INM and INGV-SGX) are able to reproduce this mechanism in accordance to what observed in the global reanalysis systems. Our result introduces non-negligible caveats with respect to the ability of most of CMIP3 models in obtaining reliable description of AEWs. (orig.)

  17. The impact of annual and seasonal rainfall patterns on growth and phenology of emergent tree species in Southeastern Amazonia, Brazil

    Science.gov (United States)

    James Grogan; Mark Schulze

    2012-01-01

    Understanding tree growth in response to rainfall distribution is critical to predicting forest and species population responses to climate change. We investigated inter-annual and seasonal variation in stem diameter by three emergent tree species in a seasonally dry tropical forest in southeast Pará, Brazil. Annual diameter growth rates by Swietenia macrophylla...

  18. Large inter annual variation in air quality during the annual festival 'Diwali' in an Indian megacity.

    Science.gov (United States)

    Parkhi, Neha; Chate, Dilip; Ghude, Sachin D; Peshin, Sunil; Mahajan, Anoop; Srinivas, Reka; Surendran, Divya; Ali, Kaushar; Singh, Siddhartha; Trimbake, Hanumant; Beig, Gufran

    2016-05-01

    A network of air quality and weather monitoring stations was established under the System of Air Quality Forecasting and Research (SAFAR) project in Delhi. We report observations of ozone (O3), nitrogen oxides (NOx), carbon monoxide (CO) and particulate matter (PM2.5 and PM10) before, during and after the Diwali in two consecutive years, i.e., November 2010 and October 2011. The Diwali days are characterised by large firework displays throughout India. The observations show that the background concentrations of particulate matter are between 5 and 10 times the permissible limits in Europe and the United States. During the Diwali-2010, the highest observed PM10 and PM2.5 mass concentration is as high as 2070µg/m3 and 1620μg/m(3), respectively (24hr mean), which was about 20 and 27 times to National Ambient Air Quality Standards (NAAQS). For Diwali-2011, the increase in PM10 and PM2.5 mass concentrations was much less with their peaks of 600 and of 390μg/m(3) respectively, as compared to the background concentrations. Contrary to previous reports, firework display was not found to strongly influence the NOx, and O3 mixing ratios, with the increase within the observed variability in the background. CO mixing ratios showed an increase. We show that the large difference in 2010 and 2011 pollutant concentrations is controlled by weather parameters. Copyright © 2015. Published by Elsevier B.V.

  19. Effects of Climatic Factors and Ecosystem Responses on the Inter-Annual Variability of Evapotranspiration in a Coniferous Plantation in Subtropical China

    Science.gov (United States)

    Xu, Mingjie; Wen, Xuefa; Wang, Huimin; Zhang, Wenjiang; Dai, Xiaoqin; Song, Jie; Wang, Yidong; Fu, Xiaoli; Liu, Yunfen; Sun, Xiaomin; Yu, Guirui

    2014-01-01

    Because evapotranspiration (ET) is the second largest component of the water cycle and a critical process in terrestrial ecosystems, understanding the inter-annual variability of ET is important in the context of global climate change. Eight years of continuous eddy covariance measurements (2003–2010) in a subtropical coniferous plantation were used to investigate the impacts of climatic factors and ecosystem responses on the inter-annual variability of ET. The mean and standard deviation of annual ET for 2003–2010 were 786.9 and 103.4 mm (with a coefficient of variation of 13.1%), respectively. The inter-annual variability of ET was largely created in three periods: March, May–June, and October, which are the transition periods between seasons. A set of look-up table approaches were used to separate the sources of inter-annual variability of ET. The annual ETs were calculated by assuming that (a) both the climate and ecosystem responses among years are variable (Vcli-eco), (b) the climate is variable but the ecosystem responses are constant (Vcli), and (c) the climate is constant but ecosystem responses are variable (Veco). The ETs that were calculated under the above assumptions suggested that the inter-annual variability of ET was dominated by ecosystem responses and that there was a negative interaction between the effects of climate and ecosystem responses. These results suggested that for long-term predictions of water and energy balance in global climate change projections, the ecosystem responses must be taken into account to better constrain the uncertainties associated with estimation. PMID:24465610

  20. Seasonal and inter-annual variations of dissolved oxygen in the northwestern Mediterranean Sea (DYFAMED site)

    Science.gov (United States)

    Coppola, Laurent; Legendre, Louis; Lefevre, Dominique; Prieur, Louis; Taillandier, Vincent; Diamond Riquier, Emilie

    2018-03-01

    Dissolved oxygen (O2) is a relevant tracer to interpret variations of both water mass properties in the open ocean and biological production in the surface layer of both coastal and open waters. Deep-water formation is very active in the northwestern Mediterranean Sea, where it influences intermediate and deep waters properties, nutrients replenishment and biological production. This study analyses, for the first time, the 20-year time series of monthly O2 concentrations at the DYFAMED long-term sampling site in the Ligurian Sea. Until the winters of 2005 and 2006, a thick and strong oxygen minimum layer was present between 200 and 1300 m because dense water formation was then local, episodic and of low intensity. In 2005-2006, intense and rapid deep convection injected 24 mol O2 m-2 between 350 and 2000 m from December 2005 to March 2006. Since this event, the deep layer has been mostly ventilated during winter time by newly formed deep water spreading from the Gulf of Lion 250 km to the west and by some local deep mixing in early 2010, 2012 and 2013. In the context of climate change, it is predicted that the intensity of deep convection will become weaker in the Mediterranean, which could potentially lead to hypoxia in intermediate and deep layers with substantial impact on marine ecosystems. With the exception of winters 2005 and 2006, the O2 changes in surface waters followed a seasonal trend that reflected the balance between air-sea O2 exchanges, changes in the depth of the mixed layer and phytoplankton net photosynthesis. We used the 20-year O2 time series to estimate monthly and annual net community production. The latter was 7.1 mol C m-2 yr-1, consistent with C-14 primary production determinations and sediment-trap carbon export fluxes at DYFAMED.

  1. The Physical Context of Seasonal and Inter-Annual Variability in Phytoplankton across the Scotian Shelf: Insights from Profiling Gliders

    Science.gov (United States)

    Ross, T.; Craig, S. E.; Dever, M.; Beck, M.; Comeau, A.; Davis, R. F.

    2016-02-01

    Understanding how phytoplankton respond to their physical environment is key to predicting how bloom dynamics might change under future climate change scenarios. Phytoplankton are at the base of most marine food webs and play an important role in drawing CO2 out of the atmosphere. We use 5 years of simultaneous CTD, irradiance, fluorescence by chlorophyll a and optical backscattering observations obtained from Slocum glider missions across the Scotian Shelf, near Halifax, Nova Scotia, Canada, to examine the seasonal and inter-annual variability in proxies of phytoplankton abundance and type, and their physical context. Consistent with previous studies, we find that the main spring bloom occurs before the onset of the seasonal stratified layer. In fact, the largest chlorophyll observations consistently occurred while there was very little stratification in the upper 60 meters. This first bloom type, which was diatom dominated, was followed by a phytoplankton assemblage dominated by pico- and nano-phytoplankton and dinoflagellates associated with the nutrient poor, more stable summertime conditions. We examine the conditions throughout the entire growing season and compare the conditions during the initiation of the spring diatom bloom between years.

  2. Mechanisms influencing seasonal to inter-annual prediction skill of sea ice extent in the Arctic Ocean in MIROC

    Science.gov (United States)

    Ono, Jun; Tatebe, Hiroaki; Komuro, Yoshiki; Nodzu, Masato I.; Ishii, Masayoshi

    2018-02-01

    To assess the skill of seasonal to inter-annual predictions of the detrended sea ice extent in the Arctic Ocean (SIEAO) and to clarify the underlying physical processes, we conducted ensemble hindcasts, started on 1 January, 1 April, 1 July and 1 October for each year from 1980 to 2011, for lead times up to three years, using the Model for Interdisciplinary Research on Climate (MIROC) version 5 initialised with the observed atmosphere and ocean anomalies and sea ice concentration. Significant skill is found for the winter months: the December SIEAO can be predicted up to 11 months ahead (anomaly correlation coefficient is 0.42). This skill might be attributed to the subsurface ocean heat content originating in the North Atlantic. A plausible mechanism is as follows: the subsurface water flows into the Barents Sea from spring to fall and emerges at the surface in winter by vertical mixing, and eventually affects the sea ice variability there. Meanwhile, the September SIEAO predictions are skillful for lead times of up to two months, due to the persistence of sea ice in the Beaufort, Chukchi, and East Siberian seas initialised in July, as suggested by previous studies.

  3. Regional peculiarities in the inter-annual distribution of the red 630.0 nm line nightglow intensities over Abastumani

    Science.gov (United States)

    Toriashvili, L.; Didebulidze, G. G.; Todua, M.

    2017-12-01

    Peculiarities of the inter-annual distribution of atomic oxygen red OI 630.0 nm line nightglow intensity observed from Abastumani Astrophysical Observatory (41.75 N; 42.82 E) are considered, using the long-term dataset. This distribution demonstrates semi-annual and annual-like variations which occur during solar minimum, as well as maximum phases. The maximum values of the red line intensities are in Summer, however in June it is lower than in May and July, which may be due to regional effects. This phenomenon is considered as a the possible result of regional dynamical processes influencing the behavior of the ionosphere F2 layer which cause changes of electrons/ions densities in the 630.0 nm line luminous region (maximum luminous layer is at about 230-280 km). Using the red line intensities and ionosphere F2 layer electron density data of the IRI-12 model, the changes of meridional thermospheric wind velocities are estimated for this mid-latitude region. These meridional and vertical wind field changes causes of variations of the red line intensities in June can be caused by tidal wind and accompanied by atmospheric gravity waves activities.

  4. Climate drives inter-annual variability in probability of high severity fire occurrence in the western United States

    Science.gov (United States)

    Keyser, Alisa; Westerling, Anthony LeRoy

    2017-05-01

    A long history of fire suppression in the western United States has significantly changed forest structure and ecological function, leading to increasingly uncharacteristic fires in terms of size and severity. Prior analyses of fire severity in California forests showed that time since last fire and fire weather conditions predicted fire severity very well, while a larger regional analysis showed that topography and climate were important predictors of high severity fire. There has not yet been a large-scale study that incorporates topography, vegetation and fire-year climate to determine regional scale high severity fire occurrence. We developed models to predict the probability of high severity fire occurrence for the western US. We predict high severity fire occurrence with some accuracy, and identify the relative importance of predictor classes in determining the probability of high severity fire. The inclusion of both vegetation and fire-year climate predictors was critical for model skill in identifying fires with high fractional fire severity. The inclusion of fire-year climate variables allows this model to forecast inter-annual variability in areas at future risk of high severity fire, beyond what slower-changing fuel conditions alone can accomplish. This allows for more targeted land management, including resource allocation for fuels reduction treatments to decrease the risk of high severity fire.

  5. Satellites reveals the biophysical effects of forest cover change on climate at diurnal, seasonal and inter-annual time scales

    Science.gov (United States)

    Duveiller, Gregory; Alkama, Ramdane; Cescatti, Alessandro

    2017-04-01

    Changing the planet's forest cover can have a profound impact of the climate system by altering its role as a carbon sink. However, deforestation and afforestation also changes the biophysical properties of the surface such as albedo, roughness and root depth, thus altering the energy balance and the resulting surface and air temperature. The result of these competing biophysical processes varies spatially and seasonally, and can lead to either warming or cooling depending on which process dominates. The main tools to characterize such plant-climate interactions for both the past and future are land surface models embedded in larger Earth System models, yet their capacity to model biophysical effects accurately across the globe remains unclear due to the complexity of the phenomena. Alternatively, with appropriate methodologies, the climate impacts of the biophysical effects of forest cover change can be derived from space by satellite measurements of surface temperature and energy fluxes. Here we present the confrontation of two dedicated assessments that have been specifically generated for this scope with contrasting methodologies. The first is based on identifying an actual change in the local climate following an observed forest cover transition. Although it directly measures the desired effect, this method can only be applied to the places where vegetation change has effectively occurred. The second method relies on a 'space-for-time' approximation that identifies the potential impact of a plant cover transition from differences in climate amongst neighboring areas with contrasting vegetation. We show how both approaches reinforce and complement each other to provide a consolidated result across diurnal, seasonal and inter-annual time scales. We anticipate that these evidences derived from satellite records may support the benchmarking and development of Earth system models and support the inclusion of vegetation-driven biophysical processes in climate

  6. Detecting Inter-Annual Variations in the Phenology of Evergreen Conifers Using Long-Term MODIS Vegetation Index Time Series

    Directory of Open Access Journals (Sweden)

    Laura Ulsig

    2017-01-01

    Full Text Available Long-term observations of vegetation phenology can be used to monitor the response of terrestrial ecosystems to climate change. Satellite remote sensing provides the most efficient means to observe phenological events through time series analysis of vegetation indices such as the Normalized Difference Vegetation Index (NDVI. This study investigates the potential of a Photochemical Reflectance Index (PRI, which has been linked to vegetation light use efficiency, to improve the accuracy of MODIS-based estimates of phenology in an evergreen conifer forest. Timings of the start and end of the growing season (SGS and EGS were derived from a 13-year-long time series of PRI and NDVI based on a MAIAC (multi-angle implementation of atmospheric correction processed MODIS dataset and standard MODIS NDVI product data. The derived dates were validated with phenology estimates from ground-based flux tower measurements of ecosystem productivity. Significant correlations were found between the MAIAC time series and ground-estimated SGS (R2 = 0.36–0.8, which is remarkable since previous studies have found it difficult to observe inter-annual phenological variations in evergreen vegetation from satellite data. The considerably noisier NDVI product could not accurately predict SGS, and EGS could not be derived successfully from any of the time series. While the strongest relationship overall was found between SGS derived from the ground data and PRI, MAIAC NDVI exhibited high correlations with SGS more consistently (R2 > 0.6 in all cases. The results suggest that PRI can serve as an effective indicator of spring seasonal transitions, however, additional work is necessary to confirm the relationships observed and to further explore the usefulness of MODIS PRI for detecting phenology.

  7. Trends and inter-annual variability of methane emissions derived from 1979-1993 global CTM simulations

    Directory of Open Access Journals (Sweden)

    F. Dentener

    2003-01-01

    Full Text Available The trend and interannual variability of methane sources are derived from multi-annual simulations of tropospheric photochemistry using a 3-D global chemistry-transport model. Our semi-inverse analysis uses the fifteen years (1979--1993 re-analysis of ECMWF meteorological data and annually varying emissions including photo-chemistry, in conjunction with observed CH4 concentration distributions and trends derived from the NOAA-CMDL surface stations. Dividing the world in four zonal regions (45--90 N, 0--45 N, 0--45 S, 45--90 S we find good agreement in each region between (top-down calculated emission trends from model simulations and (bottom-up estimated anthropogenic emission trends based on the EDGAR global anthropogenic emission database, which amounts for the period 1979--1993 2.7 Tg CH4 yr-1. Also the top-down determined total global methane emission compares well with the total of the bottom-up estimates. We use the difference between the bottom-up and top-down determined emission trends to calculate residual emissions. These residual emissions represent the inter-annual variability of the methane emissions. Simulations have been performed in which the year-to-year meteorology, the emissions of ozone precursor gases, and the stratospheric ozone column distribution are either varied, or kept constant. In studies of methane trends it is most important to include the trends and variability of the oxidant fields. The analyses reveals that the variability of the emissions is of the order of 8Tg CH4 yr-1, and likely related to wetland emissions and/or biomass burning.

  8. Inter-annual variations in water yield to lakes in northeastern Alberta: implications for estimating critical loads of acidity

    Directory of Open Access Journals (Sweden)

    Roderick HAZEWINKEL

    2010-08-01

    Full Text Available Stable isotopes of water were applied to estimate water yield to fifty lakes in northeastern Alberta as part of an acid sensitivity study underway since 2002 in the Athabasca Oil Sands Region (AOSR. Herein, we apply site-specific water yields for each lake to calculate critical loads of acidity using water chemistry data and a steady-state water chemistry model. The main goal of this research was to improve site-specific critical load estimates and to understand the sensitivity to hydrologic variability across a Boreal Plains region under significant oil sands development pressure. Overall, catchment water yields were found to vary significantly over the seven year monitoring period, with distinct variations among lakes and between different regions, overprinted by inter-annual climate-driven shifts. Analysis of critical load estimates based on site-specific water yields suggests that caution must be applied to establish hydrologic conditions and define extremes at specific sites in order to protect more sensitive ecosystems. In general, lakes with low (high water yield tended to be more (less acid sensitive but were typically less (more affected by interannual hydrological variations. While it has been customary to use long-term water yields to define a static critical load for lakes, we find that spatial and temporal variability in water yield may limit effectiveness of this type of assessment in areas of the Boreal Plain characterized by heterogeneous runoff and without a long-term lake-gauging network. Implications for predicting acidification risk are discussed for the AOSR.

  9. Inter-annual Variability of Evapotranspiration in a Semi-arid Oak-savanna Ecosystem: Measured and Modeled Buffering to Precipitation Changes

    Science.gov (United States)

    Raz-Yaseef, N.; Sonnentag, O.; Kobayashi, H.; Baldocchi, D. D.

    2010-12-01

    Precipitation (P) is the primary control on vegetation dynamics and productivity, implying that climate induced disturbances in frequency and timing of P are intimately coupled with fluxes of carbon, water and energy. Future climate change is expected to increase extreme rainfall events as well as droughts, suggesting linked vegetation changes to an unknown extent. Semi-arid climates experience large inter-annual variability (IAV) in P, creating natural conditions adequate to study how year-to-year changes in P affect atmosphere-biosphere fluxes. We used a 10-year flux database collected at a semi-arid savanna site in order to: (1) define IAV in P by means of frequency and timing; (2) investigate how changes in P affect the ecohydrology of the forest and its partitioning into the main vapor fluxes, and (3) evaluate model capability to predict IAV of carbon and water fluxes above and below the canopy. This is based on the perception that the capability of process-oriented models to construct the deviation, and not the average, is important in order to correctly predict ecosystem sensitivity to climate change. Our research site was a low density and low LAI (0.8) semi-arid (P=523±180 mm yr-1) savanna site, combined of oaks and grass, and located at Tonzi ranch, California. Measurements of carbon and water fluxes above and below the tree canopy using eddy covariance and supplementary measurements have been made since 2001. Measured fluxes were compared to modeled based on two bio-meteorological process-oriented ecosystem models: BEPS and 3D-CAONAK. Our results show that IAV in P was large, and standard deviation (STD) was 38% of the average. Accordingly, the wet soil period (measured volumetric water content > 8%) varied between 156 days in dry years to 301 days in wet years. IAV of the vapor fluxes were lower than that of P (STD was 17% for the trees and 23% for the floor components), suggesting on ecosystem buffering to changes in P. The timing of grass green up

  10. Analysis on inter-annual variability of CO2 exchange in Arctic tundra: a model-data approach

    Science.gov (United States)

    López Blanco, E.; Lund, M.; Christensen, T. R.; Smallman, T. L.; Slevin, D.; Westergaard-Nielsen, A.; Tamstorf, M. P.; Williams, M.

    2017-12-01

    Arctic ecosystems are exposed to rapid changes triggered by the climate variability, thus there is a growing concern about how the carbon (C) exchange balance will respond to climate change. There is a lack of knowledge about the mechanisms that drive the interactions between photosynthesis and ecological respiration with changes in C stocks in the Arctic tundra across full annual cycles. The reduction of uncertainties can be addressed through process-based modelling efforts. Here, we report the independent predictions of net ecosystem exchange (NEE), gross primary production (GPP) and ecosystem respiration (Reco) calculated from the soil-plant-atmosphere (SPA) model across eight years. The model products are validated with observational data obtained from the Greenland Ecosystem Monitoring (GEM) program in West Greenland tundra (64° N). Overall, the model results explain 71%, 73% and 51% of the variance in NEE, GPP and Reco respectively using data on meteorology and local vegetation and soil structure. The estimated leaf area index (LAI) is able to explain 80% of the plant greenness variation, which was used as a plant phenology proxy. The full annual cumulated NEE during the 2008-2015 period was -0.13 g C m-2 on average (range -30.6 to 34.1 g C m-2), while GPP was -214.6 g C m-2 (-126.2 to -332.8 g C m-2) and Reco was 214.4 g C m-2 (213.9 to 302.2 g C m-2). We found that the model supports the main finding from our previous analysis on flux responses to meteorological variations and biological disturbance. Here, large inter-annual variations in GPP and Reco are also compensatory, and so NEE remains stable across climatically diverse snow-free seasons. Further, we note evidence that leaf maintenance and root growth respiration are highly correlated with GPP (R2 = 0.92 and 0.83, p budgets and the delayed effect of wintertime conditions on the C fluxes.

  11. Drivers of inter-annual variability in Net Ecosystem Exchange in a semi-arid savanna ecosystem, South Africa

    CSIR Research Space (South Africa)

    Archibald, SA

    2009-01-01

    Full Text Available and filling gaps in eddy-covariance data in semi-arid systems were developed. Net ecosystem exchange (NEE) in these systems occurs as pulses associated with rainfall events, a pattern not well-represented in current standard gap-filling procedures developed...

  12. Rainfall mediations in the spreading of epidemic cholera

    Science.gov (United States)

    Righetto, L.; Bertuzzo, E.; Mari, L.; Schild, E.; Casagrandi, R.; Gatto, M.; Rodriguez-Iturbe, I.; Rinaldo, A.

    2013-10-01

    Following the empirical evidence of a clear correlation between rainfall events and cholera resurgence that was observed in particular during the recent outbreak in Haiti, a spatially explicit model of epidemic cholera is re-examined. Specifically, we test a multivariate Poisson rainfall generator, with parameters varying in space and time, as a driver of enhanced disease transmission. The relevance of the issue relates to the key insight that predictive mathematical models may provide into the course of an ongoing cholera epidemic aiding emergency management (say, in allocating life-saving supplies or health care staff) or in evaluating alternative management strategies. Our model consists of a set of dynamical equations (SIRB-like i.e. subdivided into the compartments of Susceptible, Infected and Recovered individuals, and including a balance of Bacterial concentrations in the water reservoir) describing a connected network of human communities where the infection results from the exposure to excess concentrations of pathogens in the water. These, in turn, are driven by rainfall washout of open-air defecation sites or cesspool overflows, hydrologic transport through waterways and by mobility of susceptible and infected individuals. We perform an a posteriori analysis (from the beginning of the epidemic in October 2010 until December 2011) to test the model reliability in predicting cholera cases and in testing control measures, involving vaccination and sanitation campaigns, for the ongoing epidemic. Even though predicting reliably the timing of the epidemic resurgence proves difficult due to rainfall inter-annual variability, we find that the model can reasonably quantify the total number of reported infection cases in the selected time-span. We then run a multi-seasonal prediction of the course of the epidemic until December 2015, to investigate conditions for further resurgences and endemicity of cholera in the region with a view to policies which may bring to

  13. Intra and inter-annual structure of zooplankton communities in floodplain lakes: a long-term ecological research study

    Directory of Open Access Journals (Sweden)

    Nadson R. Simões

    2012-12-01

    Full Text Available Water flow management has significantly changed the natural dynamic of floods, which are responsible for the structure and dynamic of aquatic communities in river-floodplain systems. With the aim to elaborate a conceptual framework that describes the main ecological factors associated with zooplankton community structure in the Upper Paraná River, we investigated the mechanisms that regulate the communities structure and their response to inter-annual and hydro-sedimentological variations in the floodplain and the biological factors associated with species abundance in those communities. For this we conducted samplings every six months (potamophase in March and limnophase in September to characterize intra and inter-annual variations in community structure between 2000 and 2008. The intra-annual differences on the species richness, abundance, Shannon diversity index, and evenness, were conducted using Bayesian procedures to show probabilistic predictions of the data fit to main variation sources. Non-metric multi-dimensional scaling (NMDS, multi-response permutation procedure (MRPP, and indicator species analysis (IndVal were run to assess and characterize the seasonality of the community structure. During high water (potamophase, hydrologic connectivity favoured exchange and dispersal of species in some lakes, increasing local diversity; during low water (limnophase, higher local productivity favoured opportunistic taxa, increasing species dominance and decreasing local diversity. Food resources and density of small-size fish were biological factors associated with the seasonal dynamic of the zooplankton community; these factors were dependent on hydrosedimentological phase (potamophase or limnophase. Water levels and limnological modifications related to water flow management have promoted replacement and impoverishment of aquatic biota in affected lakes and have indicated the ecological importance of a natural dynamic flood, which displays

  14. Intra-Seasonal Rainfall Variations and Linkage with Kharif Crop Production: An Attempt to Evaluate Predictability of Sub-Seasonal Rainfall Events

    Science.gov (United States)

    Singh, Ankita; Ghosh, Kripan; Mohanty, U. C.

    2017-11-01

    The sub-seasonal variation of Indian summer monsoon rainfall highly impacts Kharif crop production in comparison with seasonal total rainfall. The rainfall frequency and intensity corresponding to various rainfall events are found to be highly related to crop production and therefore, the predictability of such events are considered to be diagnosed. Daily rainfall predictions are made available by one of the coupled dynamical model National Centers for Environmental Prediction Climate Forecast System (NCEPCFS). A large error in the simulation of daily rainfall sequence influences to take up a bias correction and for that reason, two approaches are used. The bias-corrected GCM is able to capture the inter-annual variability in rainfall events. Maximum prediction skill of frequency of less rainfall (LR) event is observed during the month of September and a similar result is also noticed for moderate rainfall event with maximum skill over the central parts of the country. On the other hand, the impact of rainfall weekly rainfall intensity is evaluated against the Kharif rice production. It is found that weekly rainfall intensity during July is having a significant impact on Kharif rice production, but the corresponding skill was found very low in GCM. The GCM are able to simulate the less and moderate rainfall frequency with significant skill.

  15. The impact of inter-annual variability of annual cycle on long-term persistence of surface air temperature in long historical records

    Science.gov (United States)

    Deng, Qimin; Nian, Da; Fu, Zuntao

    2018-02-01

    Previous studies in the literature show that the annual cycle of surface air temperature (SAT) is changing in both amplitude and phase, and the SAT departures from the annual cycle are long-term correlated. However, the classical definition of temperature anomalies is based on the assumption that the annual cycle is constant, which contradicts the fact of changing annual cycle. How to quantify the impact of the changing annual cycle on the long-term correlation of temperature anomaly variability still remains open. In this paper, a recently developed data adaptive analysis tool, the nonlinear mode decomposition (NMD), is used to extract and remove time-varying annual cycle to reach the new defined temperature anomalies in which time-dependent amplitude of annual cycle has been considered. By means of detrended fluctuation analysis, the impact induced by inter-annual variability from the time-dependent amplitude of annual cycle has been quantified on the estimation of long-term correlation of long historical temperature anomalies in Europe. The results show that the classical climatology annual cycle is supposed to lack inter-annual fluctuation which will lead to a maximum artificial deviation centering around 600 days. This maximum artificial deviation is crucial to defining the scaling range and estimating the long-term persistence exponent accurately. Selecting different scaling range could lead to an overestimation or underestimation of the long-term persistence exponent. By using NMD method to extract the inter-annual fluctuations of annual cycle, this artificial crossover can be weakened to extend a wider scaling range with fewer uncertainties.

  16. The Influences of Drought and Land-Cover Conversion on Inter-Annual Variation of NPP in the Three-North Shelterbelt Program Zone of China Based on MODIS Data.

    Directory of Open Access Journals (Sweden)

    Dailiang Peng

    Full Text Available Terrestrial ecosystems greatly contribute to carbon (C emission reduction targets through photosynthetic C uptake.Net primary production (NPP represents the amount of atmospheric C fixed by plants and accumulated as biomass. The Three-North Shelterbelt Program (TNSP zone accounts for more than 40% of China's landmass. This zone has been the scene of several large-scale ecological restoration efforts since the late 1990s, and has witnessed significant changes in climate and human activities.Assessing the relative roles of different causal factors on NPP variability in TNSP zone is very important for establishing reasonable local policies to realize the emission reduction targets for central government. In this study, we examined the relative roles of drought and land cover conversion(LCC on inter-annual changes of TNSP zone for 2001-2010. We applied integrated correlation and decomposition analyses to a Standardized Evapotranspiration Index (SPEI and MODIS land cover dataset. Our results show that the 10-year average NPP within this region was about 420 Tg C. We found that about 60% of total annual NPP over the study area was significantly correlated with SPEI (p<0.05. The LCC-NPP relationship, which is especially evident for forests in the south-central area, indicates that ecological programs have a positive impact on C sequestration in the TNSP zone. Decomposition analysis generally indicated that the contributions of LCC, drought, and other Natural or Anthropogenic activities (ONA to changes in NPP generally had a consistent distribution pattern for consecutive years. Drought and ONA contributed about 74% and 23% to the total changes in NPP, respectively, and the remaining 3% was attributed to LCC. Our results highlight the importance of rainfall supply on NPP variability in the TNSP zone.

  17. Seasonal and inter-annual variability in velocity and frontal position of Siachen Glacier (Eastern Karakorum) using multi-satellite data

    Science.gov (United States)

    Usman, M.; Furuya, M.; Sakakibara, D.; Abe, T.

    2017-12-01

    The anomalous behavior of Karakorum glaciers is a hot topic of discussion in the scientific community. Siachen Glacier is one of the longest glaciers ( 75km) in Karakorum Range. This glacier is supposed to be a surge type but so far no studies have confirmed this claim. Detailed velocity mapping of this glacier can possibly provide some clues about intra/inter-annual changes in velocity and observed terminus. Using L-band SAR data of ALOS-1/2, we applied the feature tracking technique (search patch of 128x128 pixels (range x azimuth) , sampling interval of 12x36 pixels) to derive velocity changes; we used GAMMA software. The velocity was calculated by following the parallel flow assumption. To calculate the local topographic gradient unit vector, we used ASTER-GDEM. We also used optical images acquired by Landsat 5 Thematic Mapper (TM), the Landsat 7 Enhanced Thematic Mapper Plus (ETM+) to derive surface velocity. The algorithm we used is Cross-Correlation in Frequency domain on Orientation images (CCF-O). The velocity was finally calculated by setting a flow line and averaging over the area of 200x200m2. The results indicate seasonal speed up signals that modulate inter-annually from 1999 to 2011, with slight or no change in the observed frontal position. However, in ALOS-2 data, the `observed terminus' seems to have been advancing.

  18. Root-associated fungi of Vaccinium carlesii in subtropical forests of China: intra- and inter-annual variability and impacts of human disturbances

    Science.gov (United States)

    Zhang, Yanhua; Ni, Jian; Tang, Fangping; Pei, Kequan; Luo, Yiqi; Jiang, Lifen; Sun, Lifu; Liang, Yu

    2016-01-01

    Ericoid mycorrhiza (ERM) are expected to facilitate establishment of ericaceous plants in harsh habitats. However, diversity and driving factors of the root-associated fungi of ericaceous plants are poorly understood. In this study, hair-root samples of Vaccinium carlesii were taken from four forest types: old growth forests (OGF), secondary forests with once or twice cutting (SEC I and SEC II), and Cunninghamia lanceolata plantation (PLF). Fungal communities were determined using high-throughput sequencing, and impacts of human disturbances and the intra- and inter-annual variability of root-associated fungal community were evaluated. Diverse fungal taxa were observed and our results showed that (1) Intra- and inter-annual changes in root-associated fungal community were found, and the Basidiomycota to Ascomycota ratio was related to mean temperature of the sampling month; (2) Human disturbances significantly affected structure of root-associated fungal community of V. carlesii, and two secondary forest types were similar in root-associated fungal community and were closer to that of the old growth forest; (3) Plant community composition, edaphic parameters, and geographic factors significantly affected root-associated fungal communities of V. carlesii. These results may be helpful in better understanding the maintenance mechanisms of fungal diversity associated with hair roots of ERM plants under human disturbances. PMID:26928608

  19. Inter-annual variability in the thermal structure of an oceanic time series station off Ecuador (1990-2003) associated with El Niño events

    Science.gov (United States)

    Garcés-Vargas, José; Schneider, Wolfgang; Abarca del Río, Rodrigo; Martínez, Rodney; Zambrano, Eduardo

    2005-10-01

    Previously unpublished data (1990-2003) from a marine station located 20 km off the coast of Ecuador (Station La Libertad, 02°12'S, 080°55'W) are employed to investigate oceanic inter-annual variability in the far eastern equatorial Pacific, and its relation to the central-eastern equatorial Pacific. La Libertad is the only time series station between the Galapagos Islands and the South American coast, the region most affected by El Niño events (El Niño 2 region, 0-5°S, 90°W-80°W). Although configured and serviced differently, station La Libertad can be looked at as an eastern extension of the TAO/TRITON monitoring system, whose easternmost mooring is located at 95°W, 1550 km offshore. This study of El Niño's impact on the thermocline and its relationship to sea surface temperature revealed anomalies in the thermocline at station La Libertad some 2-4 months before their appearance at the sea surface. Inter-annual variability, namely quasi-biennial and quasi-quadrennial oscillations, accounts for roughly 80% of the total variance in temperature anomalies observed in the water column at station La Libertad. The coincidence in both phase and amplitude of these inter-annual oscillations explains the strength of El Niño events in the water column off La Libertad. We further show that anomalies in heat content appear 8-9 weeks earlier at 140°W in the equatorial Pacific (6550 km away from the coast) than at the coast itself. The arrival of El Niño, which has important regional social consequences as well as those for local fisheries, could therefore be predicted in the sub-surface waters off Ecuador by using these anomalies as a complementary index. In addition, the speed of the eastward propagation of these El Niño-associated anomalies' suggests the possible participation of higher-order baroclinic mode Kelvin waves and associated interaction processes in the eastern Pacific, which should be further investigated.

  20. A procedure to derive intra-and inter-annual changes on vegetation from NDVI time series. A case study in Spain

    International Nuclear Information System (INIS)

    Gilabert, M. A; Martinez, B.; Melia, J.

    2009-01-01

    The objective of this work is to study the spatial patterns of vegetation activity over spain and its temporal variability throughout the period 1989-2002. A multi-resolution analysis (MRA) bases on the wavelet transform has been implemented on NDVI time series from the MEDOKADS database. The MRA decomposes the original signal as a sum of series associated with temporal scales. Specifically, the intra-annual series is processed to define several key features in relation with the vegetation penology. In contras, the inter-annual components of the signal is used to detect trends by means of a Mann-Kendall test and map the magnitude of the land-cover change. Finally, a comprehensive identification of the areas presenting a negative value of the magnitude of change is carried out to select those linked to land degradation processes. Results show a major presence of these areas the Southeast of Spain. (Author) 5 refs.

  1. Inter-annual variability of NDVI in response to long-term warming and fertilization in wet sedge and tussock tundra.

    Science.gov (United States)

    Boelman, Natalie T; Stieglitz, Marc; Griffin, Kevin L; Shaver, Gaius R

    2005-05-01

    This study explores the relationship between the normalized difference vegetation index (NDVI) and aboveground plant biomass for tussock tundra vegetation and compares it to a previously established NDVI-biomass relationship for wet sedge tundra vegetation. In addition, we explore inter-annual variation in NDVI in both these contrasting vegetation communities. All measurements were taken across long-term experimental treatments in wet sedge and tussock tundra communities at the Toolik Lake Long Term Ecological Research (LTER) site, in northern Alaska. Over 15 years (for wet sedge tundra) and 14 years (for tussock tundra), N and P were applied in factorial experiments (N, P and N+P), air temperature was increased using greenhouses with and without N+P fertilizer, and light intensity was reduced by 50% using shade cloth. during the peak growing seasons of 2001, 2002, and 2003, NDVI measurements were made in both the wet sedge and tussock tundra experimental treatment plots, creating a 3-year time series of inter-annual variation in NDVI. We found that: (1) across all tussock experimental tundra treatments, NDVI is correlated with aboveground plant biomass (r2 = 0.59); (2) NDVI-biomass relationships for tussock and wet sedge tundra communities are community specific, and; (3) NDVI values for tussock tundra communities are typically, but not always, greater than for wet sedge tundra communities across all experimental treatments. We suggest that differences between the response of wet sedge and tussock tundra communities in the same experimental treatments result from the contrasting degree of heterogeneity in species and functional types that characterize each of these Arctic tundra vegetation communities.

  2. Seasonal and inter-annual dynamics of growth, non-structural carbohydrates and C stable isotopes in a Mediterranean beech forest.

    Science.gov (United States)

    Scartazza, Andrea; Moscatello, Stefano; Matteucci, Giorgio; Battistelli, Alberto; Brugnoli, Enrico

    2013-07-01

    Seasonal and inter-annual dynamics of growth, non-structural carbohydrates (NSC) and carbon isotope composition (δ(13)C) of NSC were studied in a beech forest of Central Italy over a 2-year period characterized by different environmental conditions. The net C assimilated by forest trees was mainly used to sustain growth early in the season and to accumulate storage carbohydrates in trunk and root wood in the later part of the season, before leaf shedding. Growth and NSC concentration dynamics were only slightly affected by the reduced soil water content (SWC) during the drier year. Conversely, the carbon isotope analysis on NSC revealed seasonal and inter-annual variations of photosynthetic and post-carboxylation fractionation processes, with a significant increase in δ(13)C of wood and leaf soluble sugars in the drier summer year than in the wetter one. The highly significant correlation between δ(13)C of leaf soluble sugars and SWC suggests a decrease of the canopy C isotope discrimination and, hence, an increased water-use efficiency with decreasing soil water availability. This may be a relevant trait for maintaining an acceptable plant water status and a relatively high C sink capacity during dry seasonal periods. Our results suggest a short- to medium-term homeostatic response of the Collelongo beech stand to variations in water availability and solar radiation, indicating that this Mediterranean forest was able to adjust carbon-water balance in order to prevent C depletion and to sustain plant growth and reserve accumulation during relatively dry seasons.

  3. The Inter-Annual Variability Analysis of Carbon Exchange in Low Artic Fen Uncovers The Climate Sensitivity And The Uncertainties Around Net Ecosystem Exchange Partitioning

    Science.gov (United States)

    Blanco, E. L.; Lund, M.; Williams, M. D.; Christensen, T. R.; Tamstorf, M. P.

    2015-12-01

    An improvement in our process-based understanding of CO2 exchanges in the Arctic, and their climate sensitivity, is critical for examining the role of tundra ecosystems in changing climates. Arctic organic carbon storage has seen increased attention in recent years due to large potential for carbon releases following thaw. Our knowledge about the exact scale and sensitivity for a phase-change of these C stocks are, however, limited. Minor variations in Gross Primary Production (GPP) and Ecosystem Respiration (Reco) driven by changes in the climate can lead to either C sink or C source states, which likely will impact the overall C cycle of the ecosystem. Eddy covariance data is usually used to partition Net Ecosystem Exchange (NEE) into GPP and Reco achieved by flux separation algorithms. However, different partitioning approaches lead to different estimates. as well as undefined uncertainties. The main objectives of this study are to use model-data fusion approaches to (1) determine the inter-annual variability in C source/sink strength for an Arctic fen, and attribute such variations to GPP vs Reco, (2) investigate the climate sensitivity of these processes and (3) explore the uncertainties in NEE partitioning. The intention is to elaborate on the information gathered in an existing catchment area under an extensive cross-disciplinary ecological monitoring program in low Arctic West Greenland, established under the auspices of the Greenland Ecosystem Monitoring (GEM) program. The use of such a thorough long-term (7 years) dataset applied to the exploration in inter-annual variability of carbon exchange, related driving factors and NEE partition uncertainties provides a novel input into our understanding about land-atmosphere CO2 exchange.

  4. The role of climate and human changes on inter-annual variation in stream nitrate fluxes and concentrations

    Science.gov (United States)

    Philippe, M.; Gascuel, C.; Pierre, A.; Patrick, D.; Laurent, R.; Jérome, M.

    2010-12-01

    In recent decades, temporal variations in nitrate fluxes and concentrations in temperate rivers have resulted from the interaction of anthropogenic and climatic factors. The effect of climatic drivers remains unclear, while the relative importance of the drivers seems to be highly site dependent. This paper focuses on 2-6 years variations called meso-scale variations, and analyses the climatic drivers of these variations in a study site characterized by high N inputs from intensive animal farming systems and shallow aquifers with impervious bedrock in a temperate climate. Three approaches are developed: 1) an analysis of long-term records (30-40 years) of nitrate fluxes and nitrate concentrations in 30 coastal rivers of Western France, which were well-marked by meso-scale cycles in the fluxes and concentration with a slight hysteresis; 2) a test of the climatic control using a lumped two box model, which demonstrates that hydrological assumptions are sufficient to explain these meso-scale cycles; and 3) a model of nitrate fluxes and concentrations in two contrasted catchments subjected to recent mitigation measures, which analyses nitrate fluxes and concentrations in relation to N stored in groundwater. In coastal rivers, hydrological drivers (i.e., effective rainfall), and particularly the dynamics of the water table and rather stable nitrate concentration, explain the meso-scale cyclic patterns. In the headwater catchment, agricultural and hydrological drivers can interact according their settings. The requirements to better distinguish the effect of climate and human changes in integrated water management are addressed: long term monitoring, coupling the analysis and the modelling of large sets of catchments incorporating different sizes, land uses and environmental factors. (Figure : Discharge, nitrate concentrations and fluxes in the Aulne river from 1973 to 2007.)

  5. Numerical simulation of inter-annual variations in the properties of the upper mixed layer in the Black Sea over the last 34 years

    Science.gov (United States)

    Shapiro, Georgy I.; Wobus, Fred; Zatsepin, Andrei G.; Akivis, Tatiana M.; Zanacchi, Marcus; Stanichny, Sergey

    2014-05-01

    The Black Sea is a nearly land-locked basin where a combination of salt and heat budgets results in a unique thermohaline water mass structure. An important feature of the Black Sea is that oxygen is dissolved and rich sea life made possible only in the upper water levels. This is due to a strong pycnocline which cannot be mixed even by strong winds or winter convection (Shapiro, 2008). The upper mixed layer (UML) with a nearly uniform temperature profile and a very sharp seasonal thermocline at its lower boundary develops during the summer season (Sur & Ilyin, 1997). The deepening of the UML has an important effect on the supply of nutrients into the euphotic upper layer from the underlying nutrient-rich water mass. The temperature of the UML at any given location is dependent on the surface heat flux, horizontal advection of heat, the depth and the rate of deepening of the UML. In this study we use a 3D ocean circulation model, NEMO-SHELF (O'Dea et al, 2012) to simulate the parameters of the UML in the Black Sea over the last 34 years. The model has horizontal resolution of 1/12×1/16 degrees and 33 layers in the vertical. The vertical discretization uses a hybrid enveloped s-z grid developed in Shapiro et al. (2012). The model is spun up from climatology (Suvorov et al., 2004); it is forced by the Drakkar Forcing Set v5.2 (Brodeau et al., 2010, Meinvielle et al., 2013) and river discharges from 8 major rivers are included. For each year the model is run from 1st January and the data for the period April to October are used for analysis. The sea surface temperature produced by the model is compared with satellite data ( Modis-Aqua, 2013) to show a good agreement. The model simulations are validated against in-situ observations (BSERP-3, 2004; Piotukh et al., 2011). The analysis is performed for the deep basin where the depth of the sea is greater than 1000m. It clearly shows the inter-annual variations of both the SST and the depth of UML. The depth of UML is

  6. Influence of inter-annual variations of stratospheric dynamics in model simulations of ozone losses by aircraft emissions

    Energy Technology Data Exchange (ETDEWEB)

    Jadin, E.A. [Central Aerological Observatory, Dolgoprudny (Russian Federation)

    1997-12-31

    The questions of model predictions of aircraft emission impacts on the ozone variations are considered. Using the NMC data it is shown that the stratospheric circulation underwent the abrupt transition to a new regime in summer 1980. The strong correlations are found between the monthly mean total ozone and stratospheric angular momentum anomalies during 1979-1991. The natural long-term changes of transport processes are necessary to take into account in model simulations of anthropogenic impacts on the ozone layer. (author) 12 refs.

  7. Combined role of heat and water stresses on wheat, maize and rice inter-annual variability and trend from 1980 to 2010.

    Science.gov (United States)

    Zampieri, M.; Ceglar, A., , Dr; Dentener, F., , Dr; van den Berg, M., , Dr; Toreti, A., , Dr

    2017-12-01

    Heat waves and drought are often considered the most damaging climatic stressors for wheat and maize. In this study, based on data derived from observations, we characterize and attribute the effects of these climate extremes on wheat and maize yield anomalies (at global and national scales) with respect to the mean trend from 1980 to 2010. Using a combination of up-to-date heat wave and drought indexes (i.e. the Heat Magnitude Day, HMD, and the Standardized Precipitation Evapotranspiration Index, SPEI), we have developed a composite indicator (i.e. the Combined Stress Index, CSI) that is able to capture the spatio-temporal characteristics of the underlying physical processes in the different agro-climatic regions of the world. At the global level, our diagnostic explains the 42% and the 50% of the inter-annual wheat and maize production variabilities, respectively. The relative importance of heat stress and drought in determining the yield anomalies depends on the region. Compared to maize, and in contrast to common perception, water excess affects wheat production more than drought in several countries. The index definition can be modified in order to quantify the role of combined heat and water stress events occurrence in determining the recorded yield trends as well. Climate change is increasingly limiting maize yields in several countries, especially in Europe and China. A comparable opposite signal, albeit less statistically significant, is found for the USA, which is the main world producer. As for rice, we provide a statistical evidence pointing out to the importance of considering the interactions with the horizontal surface waters fluxes carried out by the rivers. In fact, compared to wheat and maize, the CSI statistical skills in explaining rice production variability are quite reduced. This issue is particularly relevant in paddy fields and flooded lowlands where rice is mainly grown. Therefore, we have modified the procedure including a proxy for the

  8. The inter-annual variations and the long-term trends of monthly air temperatures in Iraq over the period 1941-2013

    Science.gov (United States)

    Muslih, Khamis Daham; Błażejczyk, Krzysztof

    2017-10-01

    Mean annual and monthly averages of mean (Tmean), maximum (Tmax) and minimum (Tmin) air temperature from seven stations in Iraq were analysed to detect the inter-annual variation, long-term temporal and spatial trends distribution over the period 1941-2013. Due to non-homogeneous problems, this period has been divided into two short separated periods (1941-1980 and 1995-2013), in order to compute temperature trends. In this context two statistical tests were used: linear regression and Mann-Kendall. The time series of mean annual temperature indicate the current warming period over Iraq identical with the global warming, which has started since the middle of seventh decade of the last century. The 2010 was the warmest year in all stations. Three distinct inter-annual temperature variation patterns were observed. These were probably the effects of micro-scale and meso-scale factors. The first one represents central and northern Iraq. The second represents the south of Iraq and Kirkuk station and the third one is a characteristic for eastern Iraq. Temperature trend analysis revealed that there are general upward trends with the strongest warming trends identified in the summer months which are around 89 % of the total significant monthly trends. Spatially, in both periods the southern region of Iraq is most affected by the warming trend in Tmean and Tmax. When considering Tmin, the southern and northern regions both are affected by warming with more pronounced trend intensity in the northern stations. No significant trend occurs Hai station in both periods and Baghdad has the still less trend value. In the first period the highest rise of Tmean and Tmax values are observed in July and June in Nasiriya station at 0.61 °C/decade and 0.63 °C/decade, respectively and in Mosul station for Tmin in August is 1.41 °C/decade. Moreover, in the period from 1995 to 2013, the highest warming trend of Tmean and Tmax were in Hai station for March at 1.48 °C/decade and at 1.85

  9. Seasonal and inter-annual variability of sea surface temperature at the east coast fishing area off Peninsular Malaysia

    Science.gov (United States)

    Nurul Ridani, S.; Mustapha, M. A.; Lihan, T.; Ku Kassim, K. Y.; Raja Bidin, R. H.

    2015-09-01

    Empirical orthogonal function (EOF) analysis was used to study a time-series of the aqua MODIS data imageries in the exclusive economic zone of east coast off Peninsular Malaysia. Temporal and spatial characteristics were examined to determine the dominant pattern of sea surface temperature (SST) variability from January 2003 to December 2011.The data were analysed from daily Level 1A (1km spatial resolution) to monthly composites Level 3 data using SeaDAS and ERDAS imagine software. Four modes was obtained from the analysis with the highest variance (7.9%) represented by mode 1 which explained the seasonal cycle. Mode 2 (5.11 % of total variance) showed positive and negative peak signal during March and April and in October and November with variability near the Kelantan and Pahang waters that indicated the inter monsoon. Mode 3 (3.8 % of variance) shows variability near the Terengganu, Kelantan and Johor waters to the open sea during July and August and in May and June representing the Southwest monsoon. Mode 4 (3.36 %) showed positive signal during November and December with strong signal near Pahang and Kelantan waters while weak signal was detected near Terengganu and Kelantan's open sea representing the Northeast monsoon. The SST variability was influenced by the monsoonal system which originated by the wind forcing condition that influences circulation in the study area.

  10. Spatial and temporal variability of past rainfall in western Australia inferred from tree rings

    Science.gov (United States)

    O'Donnell, Alison; Cook, Edward; Turney, Chris; Palmer, Jonathan; Skrzypek, Grzegorz; Grierson, Pauline

    2017-04-01

    For much of the Southern Hemisphere, the ability to identify spatial and temporal patterns of past climatic variability is constrained by the short length of instrumental records and the sparse spatial distribution of proxy records. This is particularly true for continental Australia, where instrumental records are generally Australia. These chronologies are currently the only multi-century tree-ring records for mainland Australia. Both chronologies are strongly correlated with hydroclimate and allow robust reconstructions of past hydroclimatic variability over spatially broad areas (i.e., > 3° x 3°) of inland western Australia. These reconstructions represent significant extensions of the instrumental rainfall records and reveal inter-annual to multidecadal-scale variation in past hydroclimate over the last two centuries for northwest Australia and four centuries for southwest Australia. In both the northwest and southwest regions, periods of prolonged drought (typically extending between one and three decades) have been interspersed with shorter periods of above-average rainfall (typically less than a decade). Of particular note our northwest record reveals that the last two decades (1995-2012) have been unusually wet in inland northwest Australia compared to the previous two centuries. This period of unusually high rainfall coincided with both an anomalously high frequency and intensity of tropical cyclones in northwest Australia and the dominance of the positive phase of the Southern Annular Mode, both of which are major mechanisms of rainfall delivery to inland northwest Australia. Our tree-ring records also reveal the occurrence of several prolonged drought periods as well as extreme wet events in the last two centuries that were synchronous between northwest and southwest Australia, suggesting possible teleconnections between the two regions. In addition, there appears to have been a generally anti-phase relationship between the hydroclimate of inland

  11. Inter-annual variability of the Pelagic-Benthic coupling in the upwelling system off central Chile

    Directory of Open Access Journals (Sweden)

    M. Graco

    2006-01-01

    Full Text Available The coastal region of central Chile (36° S is one of the most productive coastal systems, characterized by a marked seasonality in the upwelling regime, that brings subsurface waters rich in nutrient and poor in oxygen (ESSW into the euphotic zone. This oceanographic condition depends basically on the equatorward wind strength and is modified on different time scales, with the El Niño-Southern Oscillation (ENSO phenomenon as the main source of interannual variability in the Pacific Ocean. Here we present an effort to integrate physical and biogeochemical variability associated with in situ information and experiments at coastal stations off central Chile (36° S in order to improve the knowledge on the pelagic-benthic coupling in this upwelling system during the warm ENSO phase or El Niño. Carbon fluxes exported from the water column to the sediments and the ammonium exchange across the sediment-water interface are discussed together with oceanographic and benthic conditions. All measurements and estimations were carried out from May 1997 until April 2001 at two stations, one located inside Concepción Bay (~28 m depth, and the other on the continental shelf at ~36° S (~88 m depth. The results show that the pelagic and benthic systems are strongly coupled off central Chile (36° S. Oceanographic variability associated with upwelling events (seasonal scale and an El Niño event (interannual scale was observed. The carbon fluxes exported to the sediments, the benthic conditions (i.e., quantity and quality of the sediment organic matter, and the ammonium exchange across the sediment-water interface, responded to the seasonal regime of upwelling during non El Niño years as well as to the ENSO related oceanographic variability.

  12. What drives inter-annual variations in C flux and balance in a tropical rainforest of French Guiana?

    Science.gov (United States)

    Aguilos, Maricar; Herault, Bruno; Burban, Benoit; Wagner, Fabien; Bonal, Damien

    2017-04-01

    Amazon rainforests, a major contributor to the global carbon sink, is not on steady state and information about the long-term impact of climate change on carbon fluxes between this ecosystem and the atmosphere and the resulting balance is lacking. A thorough understanding of the forest responses to climate is indeed important to improve ecosystem process models and to reduce uncertainties in the contemporary carbon balance calculations for tropical forests. To address these issues, we examined the interannual variations in gross primary photosynthesis (GPP), ecosystem respiration (RE) and net ecosystem exchange (NEE) in a tropical rainforest in French Guiana and identified key climatic drivers influencing such changes across a 12-year long period (2004 - 2015). The study period was characterized by strong differences in climate conditions, particularly in the intensity of the long dry and the long wet seasons. Fluctuations in annual average GPP vary from 9.27 ± 1.68 g C m?2 d?1 to 11.13 ± 2.21 g C m?2 d?1. RE is more varied than GPP having a difference of 2.53 C m?2 d?1 between the minimum (8.28 ± 0.85 g C m?2 d?1) and maximum (10.80 ± 1.67 g C m?2 d?1). GPP was always higher than RE annually and the forest remained a carbon sink in an annual basis although NEE has huge interannual variability, from -0.18 ± 1.64 g C m?2 d?1 to -1.62 ± 1.65 g C m?2 d?1. Annually, the combination of global radiation (Rg), relative extractable water (REW) and soil temperature (Ts) explained 51% of the variations of GPP, 30% for RE, and 39% for NEE, but global radiation was always the best predictor variable. Seasonally, Rg was the major controlling factor for GPP (r2 = 0.58; P dry season, variations in C fluxes and balance were poorly explained by climate factors. Yet, relative extractable water was the key driver of variations in RE (r2 = 0.16; P < 0.0001) and NEE (r2 = 0.10; P < 0.0001). Biotic factors such as plant area index, tree growth or litterfall did not contribute much

  13. Rainfall analysis and its implication on the mass balance and hydrological regime of the Zongo Glacier (Bolivia) Cinthya Ramallo, Thomas Condom, Jean-Emmanuel Sicart, and Thierry Lebel IRD/UJF-Grenoble1/CNRS/G-INP, LTHE, Grenoble, France

    Science.gov (United States)

    Ramallo, C.; Condom, Thomas; Sicart, Jean-Emmanuel; Lebel, Thierry

    2013-05-01

    The general context of the study is to describe the changes in the mass balance and in the hydrological regime of the Zongo glacier in relation with the rainfall variability. The hypothesis considered is that the characteristics of the rainy season strongly influence the mass balance and the hydrological regime with a control on the fusion. A new daily rainfall database for the last thirty years in the real cordillera region has been elaborated and two climatic regions can be distinguished: the Altiplano and Zongo Valley. Several methods are tested for each region to characterize the rainy season (duration, onset, end, amount of rain) considering different thresholds. Results show that annual rainfall is controlled by the number of rainy days on the Altiplano and by the intensity in the Zongo Valley. No strong correlations between ENSO and annual rainfall have been found. Comparing the last two decades, we observe a decrease of the amount of rain during the installation of the rainy season but an increase of the intensity. Inter-annual variability of the rainy day number is constant for the decades [1990-2000] and [2000-2010] but a change in the seasonal cycle is shown especially during the onset and the heart of the rainy season. The second part of the study quantifies the impact of the rainy season on the Mass balance and the hydrological regime considering each characteristic: duration, onset and end of the rainy season. The correlation between different properties and the runoff from the fusion is stronger than the correlation between the mass balance and the rainy season properties. The properties of the rainy season that explain better the hydrological behavior are the duration and the amount of rain. Finally, this study propose a link between the rainy season with hydrological functioning and mass balance for the Cordillera Real in Bolivia and these results have to be generalized for the other mountainous tropical regions.

  14. Inter-annual variability in flowering of orchids: lessons learned from 8 years of monitoring in a Mediterranean region of France

    Directory of Open Access Journals (Sweden)

    Hélène Vogt-Schilb

    2013-12-01

    Full Text Available It is important to evaluate the loss of biodiversity caused by global changes. In the case of orchids, it is still unclear how long the monitoring duration should be chosen in order to achieve a good compromise between the reliability of the orchid dynamics recorded and sampling duration (e.g. years of monitoring. This study aims to propose a method of monitoring orchids. Using a large database, we investigated the inter-annual variability in flowering of orchids in a French Mediterranean region. The database includes an 8-year-long study (2006–2013 of 47 species at 26 locations in three different types of habitats. The number of individual plants that flowered per species varied significantly between years, but not the number of species. Depending on habitat, two to four years were needed to observe the total number of species per location. Therefore, in Mediterranean regions a one-year-study seems to be insufficient to produce reliable results.

  15. Inter-annual differences of ichthyofauna structure of the Guadiana estuary and adjacent coastal area (SE Portugal/SW Spain): Before and after Alqueva dam construction

    Science.gov (United States)

    Chícharo, M. Alexandra; Chícharo, Luis; Morais, Pedro

    2006-10-01

    The objective of this study was to evaluate how inter-annual changes in the volume of freshwater input and water parameters (salinity, temperature, major dissolved nutrients, seston and chlorophyll a) affect fish assemblages in the Guadiana estuary (South Portugal). During the sampling period (two distinct hydrological years), 56 fish species were identified. Anchovies ( Engraulis encrasicolus) and barbells ( Barbus species) dominated the abundances in the high inflow year (2001), but Pomatoschistus species were the most important taxa in the low inflow year (2002). Barbells and Portuguese toadfish ( Halobatrachus didactylus) dominated the biomass in both years under different inflow conditions, but a reduction in barbells' biomass occurred during the low inflow year. Multivariate analysis indicated a persistent spatial structuring of the estuarine community for both years and in different seasonal periods. Changes in salinity and seston, which were mainly due to changes in freshwater input, had an important influence on the structure of the fish assemblages. In 2002, the increased salinity in the upper estuary allowed colonization by marine species of an area that usually contains freshwater, decreasing even more the habitat for indigenous freshwater species in the downstream area of the Guadiana River. There was also a decrease in the abundances of planktivorous and omnivorous fishes and an increase in carnivorous fishes during the low inflow year. As fishes in these systems are important regulators of processes in the trophic web, changes in the dominant feeding groups can have consequences on water quality, particularly in relation to the occurrence of plankton blooms.

  16. Assessment of a new seasonal to inter-annual operational Great Lakes water supply, water levels, and connecting channel flow forecasting system

    Science.gov (United States)

    Gronewold, A.; Fry, L. M.; Hunter, T.; Pei, L.; Smith, J.; Lucier, H.; Mueller, R.

    2017-12-01

    The U.S. Army Corps of Engineers (USACE) has recently operationalized a suite of ensemble forecasts of Net Basin Supply (NBS), water levels, and connecting channel flows that was developed through a collaboration among USACE, NOAA's Great Lakes Environmental Research Laboratory, Ontario Power Generation (OPG), New York Power Authority (NYPA), and the Niagara River Control Center (NRCC). These forecasts are meant to provide reliable projections of potential extremes in daily discharge in the Niagara and St. Lawrence Rivers over a long time horizon (5 years). The suite of forecasts includes eight configurations that vary by (a) NBS model configuration, (b) meteorological forcings, and (c) incorporation of seasonal climate projections through the use of weighting. Forecasts are updated on a weekly basis, and represent the first operational forecasts of Great Lakes water levels and flows that span daily to inter-annual horizons and employ realistic regulation logic and lake-to-lake routing. We will present results from a hindcast assessment conducted during the transition from research to operation, as well as early indications of success rates determined through operational verification of forecasts. Assessment will include an exploration of the relative skill of various forecast configurations at different time horizons and the potential for application to hydropower decision making and Great Lakes water management.

  17. From egg production to recruits: Connectivity and inter-annual variability in the recruitment patterns of European anchovy in the northwestern Mediterranean

    Science.gov (United States)

    Ospina-Alvarez, Andres; Catalán, Ignacio A.; Bernal, Miguel; Roos, David; Palomera, Isabel

    2015-11-01

    We show the application of a Spatially-Explicit Individual-Based Model (SEIBM) to understand the recruitment process of European anchovy. The SEIBM is applied to simulate the effects of inter-annual variability in parental population spawning behavior and intensity, and ocean dynamics, on the dispersal of eggs and larvae from the spawning area in the Gulf of Lions (GoL) towards the coastal nursery areas in the GoL and Catalan Sea (northwestern Mediterranean Sea). For each of seven years (2003-2009), we initialize the SEIBM with the real positions of anchovy eggs during the spawning peak, from an acoustics-derived eggs production model. We analyze the effect of spawners' distribution, timing of spawning, and oceanographic conditions on the connectivity patterns, growth, dispersal distance and late-larval recruitment (14 mm larva recruits, R14) patterns. The area of influence of the Rhône river plume was identified as having a high probability of larval recruitment success (64%), but up to 36% of R14 larvae end up in the Catalan Coast. We demonstrate that the spatial paths of larvae differ dramatically from year to year, and suggest potential offshore nursery grounds. We showed that our simulations are coherent with existing recruitment proxies and therefore open new possibilities for fisheries management.

  18. Rainfall Variability across the Agneby Watershed at the Agboville Outlet in Côte d’Ivoire, West Africa

    Directory of Open Access Journals (Sweden)

    Akissi Bienve Pélagie Kouakou

    2016-12-01

    Full Text Available This study analyzes, at local and regional scales, the rainfall variability across the Agneby watershed at the Agboville outlet over the period 1950–2013. Daily rainfall data from 14 rain gauges are used. The methods used are based, firstly, on the rainfall index which aims to characterize the inter-annual and decadal variability of rainfall and, secondly, on the moving average to determine the dynamics of the mean seasonal cycle of the precipitations. Furthermore, the Pettitt test and the Hubert segmentation are applied to detect change-point in the rainfall series. At the basin scale, analysis of rainfall signals composites has shown that the rainfall deficit was more pronounced after the leap of monsoon. Dry years were characterized by an early monsoon demise which is remarkable after 1968. Moreover, the years after 1969 presented a shift of the peaks in precipitation for about 12 days. These peaks were reached early. The rainfall signal showed that the rainfall deficit for the period after 1968, relatively to the period before, was 10% in June against 36% in October for the average rainfall in the Agneby basin. At the local scale, the deficit of the peaks depends on the location. These rainfall deficits were 23% against 36.3% in June for the Agboville and Bongouanou rain gauges, respectively.

  19. Monitoring the Change in Urban Vegetation in 13 Chilean Cities Located in a Rainfall Gradient. What is the Contribution of the Widespread Creation of New Urban Parks?

    Science.gov (United States)

    de la Barrera, Francisco; Henríquez, Cristian

    2017-10-01

    The well-being of people living in cities is strongly dependent on the existence of urban vegetation because of the ecosystem services or benefits it provides. This is why governments develop plans to create green spaces, plant trees, promote the maintenance of vegetation in private spaces and also monitor their status over time. In Latin America, and particularly in Chile, the increase of urban vegetation has been stimulated through different initiatives and regulations. However, development of monitoring programs at the national level is scarce, so it is yet unknown if these initiatives and regulations have had positive effects. In this article, we monitor the change in urban vegetation in 13 Chilean cities located in a latitudinal gradient of practically zero to almost 1800 mm of annual rainfall. We calculated the trends in NDVI (2000-2016) as an indicator of change in urban greenery using data from the MODIS Subsets platform. Likewise, to assess whether the initiatives have had an effect we quantified the number of urban parks existing at the beginning of the period and how many were created during the study period. For this, we analysed official databases and high spatial resolution satellite images. Armed with said data, we assessed whether these new parks had impacted the tendency toward change in urban greenery. The results indicate that, in general, Chilean cities vary greatly inter-annually in urban greenery and have lost urban vegetation in the last 16 years, with significant losses in four of those cities. Two cities located in desert ecosystems represent an exception and showed positive trends in their urban vegetation. The rainfall in cities has an impact on the amount of vegetation, but not on their tendency to change, i.e. there are cities with loss of vegetation at all levels of precipitation. The creation of parks has not been able to reverse negative trends, which indicates the prevalence of other drivers of change that are not sufficiently

  20. Secular change and inter-annual variability of the Gulf Stream position, 1993-2013, 70°-55°W

    Science.gov (United States)

    Bisagni, James J.; Gangopadhyay, Avijit; Sanchez-Franks, Alejandra

    2017-07-01

    The Gulf Stream (GS) is the northeastward-flowing surface limb of the Atlantic Ocean's meridional overturning circulation (AMOC) ;conveyer belt; that flows towards Europe and the Nordic Seas. Changes in the GS position after its separation from the coast at Cape Hatteras, i.e., from 75°W to 50°W, may be key to understanding the AMOC, sea level variability and ecosystem behavior along the east coast of North America. In this study we compare secular change and inter-annual variability (IAV) of the Gulf Stream North Wall (GSNW) position with equator-ward Labrador Current (LC) transport along the southwestern Grand Banks near 52°W using 21 years (1993-2013) of satellite altimeter data. Results at 55°, 60°, and 65°W show a significant southward (negative) secular trend for the GSNW, decreasing to a small but insignificant southward trend at 70°W. IAV of de-trended GSNW position residuals also decreases to the west. The long-term secular trend of annual mean upper layer (200 m) LC transport near 52°W is positive. Furthermore, IAV of LC transport residuals near 52°W along the southwestern Grand Banks are significantly correlated with GSNW position residuals at 55°W at a lag of +1-year, with positive (negative) LC transport residuals corresponding to southward (northward) GSNW positions one year later. The Taylor-Stephens index (TSI) computed from the first principal component of the GSNW position from 79° to 65°W shows a similar relationship with a more distal LC index computed along altimeter ground track 250 located north of the Grand Banks across Hamilton Bank in the western Labrador Sea. Increased (decreased) sea height differences along ground track 250 are significantly correlated with a more southward (northward) TSI two years later (lag of +2-years). Spectral analysis of IAV reveals corresponding spectral peaks at 5-7 years and 2-3 years for the North Atlantic Oscillation (NAO), GSNW (70°-55°W) and LC transport near 52°W for the 1993-2013 period

  1. Inter-annual trend of the primary contribution of ship emissions to PM2.5 concentrations in Venice (Italy): Efficiency of emissions mitigation strategies

    Science.gov (United States)

    Contini, Daniele; Gambaro, Andrea; Donateo, Antonio; Cescon, Paolo; Cesari, Daniela; Merico, Eva; Belosi, Franco; Citron, Marta

    2015-02-01

    Ships and harbour emissions are currently increasing, due to the increase of tourism and trade, with potential impact on global air pollution and climate. At local scale, in-port ship emissions influence air quality in coastal areas impacting on health of coastal communities. International legislations to reduce ship emissions, both at Worldwide and European levels, are mainly based on the use of low-sulphur content fuel. In this work an analysis of the inter-annual trends of primary contribution, ε, of tourist shipping to the atmospheric PM2.5 concentrations in the urban area of Venice has been performed. Measurements have been taken in the summer periods of 2007, 2009 and 2012. Results show a decrease of ε from 7% (±1%) in 2007 to 5% (±1%) in 2009 and to 3.5% (±1%) in 2012. The meteorological and micrometeorological conditions of the campaigns were similar. Tourist ship traffic during measurement campaigns increased, in terms of gross tonnage, of about 25.4% from 2007 to 2009 and of 17.6% from 2009 to 2012. The decrease of ε was associated to the effect of a voluntary agreement (Venice Blue Flag) for the use of low-sulphur content fuel enforced in the area between 2007 and 2009 and to the implementation of the 2005/33/CE Directive in 2010. Results show that the use of low-sulphur fuel could effectively reduce the impact of shipping to atmospheric primary particles at local scale. Further, voluntary agreement could also be effective in reducing the impact of shipping on local air quality in coastal areas.

  2. Seasonal and inter-annual variations in methyl mercury concentrations in zooplankton from boreal lakes impacted by deforestation or natural forest fires.

    Science.gov (United States)

    Garcia, Edenise; Carignan, Richard; Lean, David R S

    2007-08-01

    We compared the effects of natural and anthropogenic watershed disturbances on methyl mercury (MeHg) concentration in bulk zooplankton from boreal Shield lakes. MeHg in zooplankton was monitored for three years in nine lakes impacted by deforestation, in nine lakes impacted by wildfire, and in twenty lakes with undisturbed catchments. Lakes were sampled during spring, mid- and late summer. MeHg in zooplankton showed a seasonal trend: concentrations were the lowest in spring, then peaked in mid-summer and decreased in late summer. Over the three study years, MeHg concentrations observed in mid-summer in zooplankton from forest harvested lakes were significantly higher than in reference and fire-impacted lakes, whereas differences between these two groups of lakes were not significant. The pattern of distribution of MeHg in zooplankton during the different seasons paralleled that of dissolved organic carbon (DOC), which is known as a vector of Hg from watershed soils to lake water. Besides DOC, MeHg in zooplankton also showed a positive significant correlation with epilimnetic temperature and sulfate concentrations. An inter-annual decreasing trend in MeHg was observed in zooplankton from reference and fire-impacted lakes. In forest harvested lakes, however, MeHg concentrations remained higher and nearly constant over three years following the impact. Overall these results indicate that the MeHg pulse observed in zooplankton following deforestation by harvesting is relatively long-lived, and may have repercussions to the accumulation of MeHg along the food chain. Therefore, potential effects of deforestation on the Hg contamination of fish should be taken into account in forest management practices.

  3. CMIP5 land surface models systematically underestimate inter-annual variability of net ecosystem exchange in semi-arid southwestern North America.

    Science.gov (United States)

    MacBean, N.; Scott, R. L.; Biederman, J. A.; Vuichard, N.; Hudson, A.; Barnes, M.; Fox, A. M.; Smith, W. K.; Peylin, P. P.; Maignan, F.; Moore, D. J.

    2017-12-01

    Recent studies based on analysis of atmospheric CO2 inversions, satellite data and terrestrial biosphere model simulations have suggested that semi-arid ecosystems play a dominant role in the interannual variability and long-term trend in the global carbon sink. These studies have largely cited the response of vegetation activity to changing moisture availability as the primary mechanism of variability. However, some land surface models (LSMs) used in these studies have performed poorly in comparison to satellite-based observations of vegetation dynamics in semi-arid regions. Further analysis is therefore needed to ensure semi-arid carbon cycle processes are well represented in global scale LSMs before we can fully establish their contribution to the global carbon cycle. In this study, we evaluated annual net ecosystem exchange (NEE) simulated by CMIP5 land surface models using observations from 20 Ameriflux sites across semi-arid southwestern North America. We found that CMIP5 models systematically underestimate the magnitude and sign of NEE inter-annual variability; therefore, the true role of semi-arid regions in the global carbon cycle may be even more important than previously thought. To diagnose the factors responsible for this bias, we used the ORCHIDEE LSM to test different climate forcing data, prescribed vegetation fractions and model structures. Climate and prescribed vegetation do contribute to uncertainty in annual NEE simulations, but the bias is primarily caused by incorrect timing and magnitude of peak gross carbon fluxes. Modifications to the hydrology scheme improved simulations of soil moisture in comparison to data. This in turn improved the seasonal cycle of carbon uptake due to a more realistic limitation on photosynthesis during water stress. However, the peak fluxes are still too low, and phenology is poorly represented for desert shrubs and grasses. We provide suggestions on model developments needed to tackle these issues in the future.

  4. Rainfall extremes, weather and climatic characterization over complex terrain: A data-driven approach based on signal enhancement methods and extreme value modeling

    Science.gov (United States)

    Pineda, Luis E.; Willems, Patrick

    2017-04-01

    Weather and climatic characterization of rainfall extremes is both of scientific and societal value for hydrometeorogical risk management, yet discrimination of local and large-scale forcing remains challenging in data-scarce and complex terrain environments. Here, we present an analysis framework that separate weather (seasonal) regimes and climate (inter-annual) influences using data-driven process identification. The approach is based on signal-to-noise separation methods and extreme value (EV) modeling of multisite rainfall extremes. The EV models use a semi-automatic parameter learning [1] for model identification across temporal scales. At weather scale, the EV models are combined with a state-based hidden Markov model [2] to represent the spatio-temporal structure of rainfall as persistent weather states. At climatic scale, the EV models are used to decode the drivers leading to the shift of weather patterns. The decoding is performed into a climate-to-weather signal subspace, built via dimension reduction of climate model proxies (e.g. sea surface temperature and atmospheric circulation) We apply the framework to the Western Andean Ridge (WAR) in Ecuador and Peru (0-6°S) using ground data from the second half of the 20th century. We find that the meridional component of winds is what matters for the in-year and inter-annual variability of high rainfall intensities alongside the northern WAR (0-2.5°S). There, low-level southerly winds are found as advection drivers for oceanic moist of the normal-rainy season and weak/moderate the El Niño (EN) type; but, the strong EN type and its unique moisture surplus is locally advected at lowlands in the central WAR. Moreover, the coastal ridges, south of 3°S dampen meridional airflows, leaving local hygrothermal gradients to control the in-year distribution of rainfall extremes and their anomalies. Overall, we show that the framework, which does not make any prior assumption on the explanatory power of the weather

  5. Relationships between Tropical Rainfall Events and Regional Annual Rainfall Anomalies

    Science.gov (United States)

    Painter, C.; Varble, A.; Zipser, E. J.

    2016-12-01

    Regional annual precipitation anomalies strongly impact the health of regional ecosystems, water resources, agriculture, and the probability of flood and drought conditions. Individual event characteristics, including rain rate, areal coverage, and stratiform fraction are also crucial in considering large-scale impacts on these resources. Therefore, forecasting individual event characteristics is important and could potentially be improved through correlation with longer and better predicted timescale environmental variables such as annual rainfall. This study examines twelve years of retrieved rainfall characteristics from the Tropical Rainfall Measuring Mission (TRMM) satellite at a 5° x 5° resolution between 35°N and 35°S, as a function of annual rainfall anomaly derived from Global Precipitation Climatology Project data. Rainfall event characteristics are derived at a system scale from the University of Utah TRMM Precipitation Features database and at a 5-km pixel scale from TRMM 2A25 products. For each 5° x 5° grid box and year, relationships between these characteristics and annual rainfall anomaly are derived. Additionally, years are separated into wet and dry groups for each grid box and are compared versus one another. Convective and stratiform rain rates, along with system area and volumetric rainfall, generally increase during wetter years, and this increase is most prominent over oceans. This is in agreement with recent studies suggesting that convective systems become larger and rainier when regional annual rainfall increases or when the climate warms. Over some land regions, on the other hand, system rain rate, volumetric rainfall, and area actually decrease as annual rainfall increases. Therefore, land and ocean regions generally exhibit different relationships. In agreement with recent studies of extreme rainfall in a changing climate, the largest and rainiest systems increase in relative size and intensity compared to average systems, and do

  6. Assessing the capability of CORDEX models in simulating onset of rainfall in West Africa

    Science.gov (United States)

    Mounkaila, Moussa S.; Abiodun, Babatunde J.; `Bayo Omotosho, J.

    2015-01-01

    Reliable forecasts of rainfall-onset dates (RODs) are crucial for agricultural planning and food security in West Africa. This study evaluates the ability of nine CORDEX regional climate models (RCMs: ARPEGE, CRCM5, RACMO, RCA35, REMO, RegCM3, PRECIS, CCLM and WRF) in simulating RODs over the region. Four definitions are used to compute RODs, and two observation datasets (GPCP and TRMM) are used in the model evaluation. The evaluation considers how well the RCMs, driven by ERA-Interim reanalysis (ERAIN), simulate the observed mean, standard deviation and inter-annual variability of RODs over West Africa. It also investigates how well the models link RODs with the northward movement of the monsoon system over the region. The model performances are compared to that of the driving reanalysis—ERAIN. Observations show that the mean RODs in West Africa have a zonal distribution, and the dates increase from the Guinea coast northward. ERAIN fails to reproduce the spatial distribution of the RODs as observed. The performance of some RCMs in simulating the RODs depends on the ROD definition used. For instance, ARPEGE, RACMO, PRECIS and CCLM produce a better ROD distribution than that of ERAIN when three of the ROD definitions are used, but give a worse ROD distribution than that of ERAIN when the fourth definition is used. However, regardless of the definition used, CCRM5, RCA35, REMO, RegCM3 and WRF show a remarkable improvement over ERAIN. The study shows that the ability of the RCMs in simulating RODs over West Africa strongly depends on how well the models reproduce the northward movement of the monsoon system and the associated features. The results show that there are some differences in the RODs obtained between the two observation datasets and RCMs, and the differences are magnified by differences in the ROD definitions. However, the study shows that most CORDEX RCMs have remarkable skills in predicting the RODs in West Africa.

  7. Heterogeneity of Dutch rainfall

    NARCIS (Netherlands)

    Witter, J.V.

    1984-01-01

    Rainfall data for the Netherlands have been used in this study to investigate aspects of heterogeneity of rainfall, in particular local differences in rainfall levels, time trends in rainfall, and local differences in rainfall trend. The possible effect of urbanization and industrialization on the

  8. Inter-annual variability of surface ozone at coastal (Dumont d'Urville, 2004–2014 and inland (Concordia, 2007–2014 sites in East Antarctica

    Directory of Open Access Journals (Sweden)

    M. Legrand

    2016-07-01

    Full Text Available Surface ozone has been measured since 2004 at the coastal East Antarctic site of Dumont d'Urville (DDU, and since 2007 at the Concordia station located on the high East Antarctic plateau. This paper discusses long-term changes, seasonal and diurnal cycles, as well as inter-annual summer variability observed at these two East Antarctic sites. At Concordia, near-surface ozone data were complemented by balloon soundings and compared to similar measurements done at the South Pole. The DDU record is compared to those obtained at the coastal site of Syowa, also located in East Antarctica, as well as the coastal sites of Neumayer and Halley, both located on the coast of the Weddell Sea in West Antarctica. Surface ozone mixing ratios exhibit very similar seasonal cycles at Concordia and the South Pole. However, in summer the diurnal cycle of ozone is different at the two sites with a drop of ozone in the afternoon at Concordia but not at the South Pole. The vertical distribution of ozone above the snow surface also differs. When present, the ozone-rich layer located near the ground is better mixed and deeper at Concordia (up to 400 m than at the South Pole during sunlight hours. These differences are related to different solar radiation and wind regimes encountered at these two inland sites. DDU appears to be the coastal site where the impact of the late winter/spring bromine chemistry is the weakest, but where the impact of elevated ozone levels caused by NOx snow emissions from the high Antarctic plateau is the highest. The highest impact of the bromine chemistry is seen at Halley and Neumayer, and to a lesser extent at Syowa. These three sites are only weakly impacted by the NOx chemistry and the net ozone production occurring on the high Antarctic plateau. The differences in late winter/spring are attributed to the abundance of sea ice offshore from the sites, whereas those in summer are related to the topography of East Antarctica that promotes

  9. Differential responses of seabirds to inter-annual environmental change in the continental shelf and oceanic habitats of southeastern Bering Sea

    Science.gov (United States)

    Yamamoto, T.; Kokubun, N.; Kikuchi, D. M.; Sato, N.; Takahashi, A.; Will, A.; Kitaysky, A. S.; Watanuki, Y.

    2015-11-01

    Seasonal sea-ice cover has been decreasing in the southeastern Bering Sea shelf, which might affect ecosystem dynamics and availability of food resources to marine top predators breeding in the region. In this study, we investigated the foraging responses of two seabird species, surface-foraging red-legged kittiwakes Rissa brevirostris (hereafter, RLKI) and pursuit-diving foraging thick-billed murres Uria lomvia (TBMU) to the inter-annual change in environmental conditions. Between the study years, winter ice retreated earlier and summer water temperatures were warmer in 2014 compared to those in 2013. At-sea distributions of RLKI and TBMU breeding on St. George Island, the largest seabird colony in the region, were recorded using GPS loggers, and blood samples were taken to examine their physiological condition and isotopic foraging niche in a given year. RLKI foraging occurred mostly over the oceanic basin in both years. TBMU, however, foraged mostly over the shelf, but showed a relatively higher use of the shelf break and oceanic basin in the colder year, 2013. The foraging distances from the colony peaked at 250-300 km in 2013 and, bimodally, at 150-250 and 300-350 km in 2014 for RLKI, and tended to be farther in 2013 compared to those in 2014 for TBMU. Plasma levels of corticosterone did not differ between years in RLKI, but differed in TBMU, showing higher levels of physiological stress incurred by murres during the colder year, 2013. δ13N (a proxy of trophic level of prey) did not differ between the years in either RLKI or TBMU, while δ13C (a proxy of prey origin) were lower in 2014 than in 2013 in both species, suggesting possible differences in influx of oceanic prey items into foraging areas. These results suggest that the response of ecosystem dynamics to climate variability in the southeast Bering Sea may differ between the ocean basin and continental shelf regions, which, in turn, may generate differential responses in seabirds relying on those

  10. Intra- and Inter- annual PM2.5 variations in the Arctic region during 2003-2017 based on the NASA's MERRA-2 re-analysis data

    Science.gov (United States)

    Yasunari, T. J.; Kim, K. M.; da Silva, A. M., Jr.

    2017-12-01

    We examined the intra- and inter-annual variations of PM2.5 in the Arctic region based on monthly mean aerosols (dust, sulfate, sea salt, and carbonaceous aerosols) and PM2.5 from NASA's latest reanalysis, MERRA2. We focus on the time period from January 2003 to the recent month (May 2017). The domain of the Arctic region was defined as North of 66.5N in this study. Although there are some exceptions, the largest contributions of dust, ammonium sulfate, sea salt, and carbonaceous aerosols (i.e., Black Carbon, BC, and Particulate Organic Matter, POM) to the fractions of PM2.5 were mainly seen in spring, spring, fall, and summer, respectively. During the focused time period, the fractions of dust, ammonium sulfate, sea salt, BC, and POM explains 2.7-42.5%, 9.5-37.5%, 16.7-73.1%, 0.5-2.8%, 1.5-58.0% of the Arctic PM2.5, respectively. If we picked up the top 10 high PM2.5 months during the period, those were separated into two seasons: summer (eight months) and winter (two months). For the composites of the summer months above, the areas with higher PM2.5 were Siberia, Far East, Alaska, and Canada and the regions where POM fractions were larger, implying the contributions from smokes due to active wildfires in summer seasons. For the winter months, the mixture of increased dust, ammonium sulfate, and sea salt was seen. However, the highest PM2.5 in the Arctic region was seen from the Kara Sea, Barents Sea, and Greenland Sea over which the contribution of sea salt was very large. This means the sea salt aerosols were the main contributor to the high PM2.5 winter months there. Based on our MERRA-2 analyses, continuous monitoring and development for better forecasting wildfire activities in summer and sea salt emissions in winter would be the keys for better understanding of the air quality in the Arctic region including mitigation and measures of it in the future.

  11. Rainfall: Features and Variations over Saudi Arabia, A Review

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    Hosny Hasanean

    2015-08-01

    Full Text Available The Saudi Arabia (SA climate varies greatly, depending on the geography and the season. According to K ppen and Geiger, the climates of SA is “desert climate”. The analysis of the seasonal rainfall detects that spring and winter seasons have the highestrainfall incidence, respectively. Through the summer,small quantities of precipitation are observed, while autumn received more precipitation more than summer season considering the total annual rainfall. In all seasons, the SW area receives rainfall, with a maximum in spring, whereas in the summer season, the NE and NW areas receive very little quantities of precipitation. The Rub Al-Khali (the SE region is almost totally dry. The maximum amount of annual rainfall does not always happen at the highest elevation. Therefore, the elevation is not the only factor in rainfall distribution.A great inter-annual change in the rainfall over the SA for the period (1978–2009 is observed. In addition, in the same period, a linear decreasing trend is found in the observed rainfall, whilst in the recent past (1994–2009 a statistically significant negative trend is observed. In the Southern part of the Arabian Peninsula (AP and along the coast of the Red Sea, it is interesting to note that rainfall increased, whilst it decreased over most areas of SA during the 2000–2009 decade, compared to 1980–1989.Statistical and numerical models are used to predict rainfall over Saudi Arabia (SA. The statistical models based on stochastic models of ARIMA and numerical models based on Providing Regional Climates for Impact Studies of Hadley Centre (PRECIS. Climate and its qualitative character and quantified range of possible future changes are investigated. The annual total rainfall decreases in most regions of the SA and only increases in the south. The summertime precipitation will be the highest between other seasons over the southern, the southwestern provinces and Asir mountains, while the wintertime

  12. Future rainfall variability in Indonesia under different ENSO and IOD composites based on decadal predictions of CMIP5 datasets

    Science.gov (United States)

    Bilhaqqi Qalbi, Harisa; Faqih, Akhmad; Hidayat, Rahmat

    2017-01-01

    El Niño-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) are amongst important climate drivers that play a significant role in driving rainfall variability in Indonesia, especially on inter-annual timescales. The phenomena are suggested to have an association with interdecadal climate variability through the modulation of their oscillations. This study aims to analyse the characteristics of future rainfall variability in Indonesia during different condition of ENSO and IOD events based on decadal predictions of near-term climate change CMIP5 GCM data outputs up to year 2035. Monthly data of global rainfall data with 5x5 km grid resolutions of CHIRPS dataset is used in this study to represent historical rainfall variability as well to serve as a reference for future rainfall predictions. The current and future rainfall and sea surface temperature data have been bias corrected before performing the analysis. Given the comparison between rainfall composites during El-Nino and positive IOD events, the study showed that the future rainfall conditions in Indonesia will become drier than the historical condition resulted from the same composite approach. In general, this study showed the Indonesian rainfall variability in the future is expected to respond differently to a different combination of ENSO and IOD conditions.

  13. [Spatiotemporal distribution characteristics of rainfall erosivity in Three Gorges Reservoir Area].

    Science.gov (United States)

    Wu, Chang-Guang; Lin, De-Sheng; Xiao, Wen-Fa; Wang, Peng-Cheng; Ma, Hao; Zhou, Zhi-Xiang

    2011-01-01

    Based on the 1976-2005 daily rainfall records from 25 weather stations in the Three Gorges Reservoir Area and its surrounding regions, this paper studied the spatiotemporal distribution characteristics of rainfall erosivity in the Area, with the focus on the annual and inter-annual trends of the rainfall erosivity around seven main weather stations. In 1976-2005, the average annual rainfall erosivity (R) in the Area was from 4389.0 to 8021.0 MJ x mm x hm(-2) x h(-1) x a(-1), being increased first from the northeast to the southwest, reached the peak in the central, and then decreased. The annual rainfall erosivity around the seven main weather stations mostly concentrated in the period from April to October, with the R value increased first from April, reached the highest in June or July, and then decreased. The maximum rainfall erosivity in consecutive three months around each of the seven weather stations accounted for 54.2%-60.7% of the total annual rainfall erosivity. In the study period, the coefficients of variation of the annual rainfall erosivity around the seven main weather stations varied moderately from 0.278 to 0.387, and the tendency rate ranged from -431.1 to 263.5 MJ x mm x hm(-2) x h(-1) x (10 a)(-1). However, the coefficients of tendency did not pass the confidence test with 5% level of significance, and the changes of annual rainfall erosivity showed random fluctuation. The variation degree of monthly rainfall erosivity was larger than the variation of annual rainfall erosivity, but only showed an obvious climate trend in a few months around parts of the weather stations.

  14. Inter-annual variability of air mass and acidified pollutants transboundary exchange in the north-eastern part of the EANET region

    Science.gov (United States)

    Gromov, Sergey A.; Trifonova-Yakovleva, Alisa; Gromov, Sergey S.

    2016-04-01

    ]. This dataset provides comprehensive monthly statistics on the wind meteorological regime at the stations of interest in a given range of altitudes. Based on long-term source observational data, the dataset is assumed being representative up to date, which allowed us to estimate monthly pollutant fluxes for the years 2006-2008 over segments of the Russian border and its whole [4]. In the current phase of our study, we calculate the inter-annual variations in the transboundary pollutant fluxes for 2000-2012 using longer-term EANET data and transient changes in air mass fluxes derived from the meteorological wind fields from ERA INTERIM re-analysis [5]. We gauge similar average air transport terms and dynamics from the statistical and reanalysis data, which bolsters our earlier findings. The reanalysis data, being naturally more variable, convolutes the variations in net air fluxes and pollutant concentrations into several episodes we emphasise, in addition to the integral pollutant transfer terms we estimate. At last, we discuss on the possibility of climate change effect on the flux strength and dynamics together with regional air quality tendencies in North-East Asia countries. References: Izrael, Yu.A., et al.: Monitoring of the Transboundary Air Pollution Transport. Gidrometeoizdat, Leningrad, 303 p., 187 (in Russian). Akimoto H., et al.: Periodic Report of the State of Acid Deposition in East Asia. Part I: Regional Assessment. EANET-UNEP/RRC.AP-ADORC, 258 p., 2006. Brukhan, F.F.: Aeroclimatic Characteristics of the Mean Winds over USSR (ed. Ignatjushina E.N.). Gidrometeoizdat, Moscow, 54 p., 1984 (in Russian). Gromov S.A., et al.: First-order evaluation of transboundary pollution fluxes in areas of EANET stations in Eastern Siberia and the Russian Far East. EANET Science Bulletin, vol. 3, pp. 195-203, 2013. Dee, D. P., et al.: The ERA-Interim reanalysis: configuration and performance of the data assimilation system, Quart. J. Royal Met. Soc., 137, 553-597, doi: 10

  15. Inter-annual and seasonal variations in transport to a measuring site in western Siberia, and their impact on the observed atmospheric CO2 mixing ratio

    International Nuclear Information System (INIS)

    Eneroth, Kristina

    2002-01-01

    Inter-annual and seasonal variations in atmospheric transport to a CO 2 measuring site in western Siberia were studied using three-dimensional trajectories. We identified large differences in transport between summer and winter, but also some differences between the years. Cluster analysis was applied to the trajectory data to determine to what degree different atmospheric flow patterns influence the variability of the atmospheric CO 2 mixing ratio. The observed CO 2 mixing ratio was also compared to observed CO 2 surface fluxes to study the impact of local sources and sinks. It was found that during July the correlation between atmospheric transport from distant source regions and CO 2 mixing ratios was poor. Furthermore the correlation was also weak between the CO 2 mixing ratio and the local eddy flux measurements. We conclude that the short-term variability in atmospheric CO 2 during summer probably is dominated by larger scale (tens up to one hundred kilometers) CO 2 surface fluxes and local meteorology. The weaker biogenic CO 2 fluxes during winter, resulted in CO 2 mixing ratios more clearly influenced by long-range transport Of CO 2 . However, the highest atmospheric CO 2 concentrations were not observed in connection with westerly winds representing transport of polluted air from Europe, but during periods with stagnant flow conditions. It was conjected that these high CO 2 mixing ratios were due to respired CO 2 trapped and accumulated in the lower parts of the planetary boundary layer. The mean duration for the identified flow patterns was in the order of two days, with a maximum duration of a week. This means that to have a chance to detect variations in CO 2 mixing ratio due to air mass changes the sampling frequency (e.g. flask samples and flight measurements) must be at least every other day. Our results show that the atmospheric transport varies with season, year and altitude. This, together with the heterogeneity of the source and sink regions are

  16. Spatial and Temporal Variability of Rainfall in the Gandaki River Basin of Nepal Himalaya

    Directory of Open Access Journals (Sweden)

    Jeeban Panthi

    2015-03-01

    Full Text Available Landslides, floods, and droughts are recurring natural disasters in Nepal related to too much or too little water. The summer monsoon contributes more than 80% of annual rainfall, and rainfall spatial and inter-annual variation is very high. The Gandaki River, one of the three major rivers of Nepal and one of the major tributaries of the Ganges River, covers all agro-ecological zones in the central part of Nepal. Time series tests were applied for different agro-ecological zones of the Gandaki River Basin (GRB for rainfall trends of four seasons (pre-monsoon, monsoon, post-monsoon and winter from 1981 to 2012. The non-parametric Mann-Kendall and Sen’s methods were used to determine the trends. Decadal anomalies relative to the long-term average were analyzed using the APHRODITE precipitation product. Trends in number of rainy days and timing of the monsoon were also analyzed. We found that the post-monsoon, pre-monsoon and winter rainfalls are decreasing significantly in most of the zones but monsoon rainfall is increasing throughout the basin. In the hill region, the annual rainfall is increasing but the rainy days do not show any trend. There is a tendency toward later departure of monsoon from Nepal, indicating an increase in its duration. These seasonally and topographically variable trends may have significant impacts for the agriculture and livestock smallholders that form the majority of the population in the GRB.

  17. Evaluation of CMIP5 twentieth century rainfall simulation over the equatorial East Africa

    Science.gov (United States)

    Ongoma, Victor; Chen, Haishan; Gao, Chujie

    2018-02-01

    This study assesses the performance of 22 Coupled Model Intercomparison Project Phase 5 (CMIP5) historical simulations of rainfall over East Africa (EA) against reanalyzed datasets during 1951-2005. The datasets were sourced from Global Precipitation Climatology Centre (GPCC) and Climate Research Unit (CRU). The metrics used to rank CMIP5 Global Circulation Models (GCMs) based on their performance in reproducing the observed rainfall include correlation coefficient, standard deviation, bias, percentage bias, root mean square error, and trend. Performances of individual models vary widely. The overall performance of the models over EA is generally low. The models reproduce the observed bimodal rainfall over EA. However, majority of them overestimate and underestimate the October-December (OND) and March-May (MAM) rainfall, respectively. The monthly (inter-annual) correlation between model and reanalyzed is high (low). More than a third of the models show a positive bias of the annual rainfall. High standard deviation in rainfall is recorded in the Lake Victoria Basin, central Kenya, and eastern Tanzania. A number of models reproduce the spatial standard deviation of rainfall during MAM season as compared to OND. The top eight models that produce rainfall over EA relatively well are as follows: CanESM2, CESM1-CAM5, CMCC-CESM, CNRM-CM5, CSIRO-Mk3-6-0, EC-EARTH, INMCM4, and MICROC5. Although these results form a fairly good basis for selection of GCMs for carrying out climate projections and downscaling over EA, it is evident that there is still need for critical improvement in rainfall-related processes in the models assessed. Therefore, climate users are advised to use the projections of rainfall from CMIP5 models over EA cautiously when making decisions on adaptation to or mitigation of climate change.

  18. Long term (2006-2016) seasonal and inter-annual variability of soil electrical resistivity in a Laotian catchment of the OZCAR network. Impact of land use change, soil type and rainfall

    Science.gov (United States)

    Robain, Henri; Ribolzi, Olivier; De Rouw, Anneke; Silvera, Norbert; Souniaphong, Phabvilay; Soulileuth, Bousamai; Latchasak, Keooudone; Sengtaheuanghoung, Oloth; Valentin, Christian; Gaillardet, Jerome

    2017-04-01

    The MSEC(1) observatory of the critical zone in south-east Asia, which is part of the OZCAR(2) Network, has been monitored since 1999 (Laos, Thailand, Vietnam) to study the long term impact of land use changes in tropical mountainous regions, in terms of soil properties (porosity, depth, SOC, nutrients…), biodiversity (weeds, soil macro fauna), plant roots (architecture, functions,…), and transfers within the critical zone at various temporal and space scales: partition between infiltration and runoff, water quality (physical, chemical and bacteriological) and erosion processes (splash, inter-rill and rill, tillage, mass-movement). In the Houay Pano catchment located in Northern Laos, a long-term monitoring system was implemented in 2006 combining Electrical Resistivity Tomography (ERT), with soil and hydrological equipments to better analyse the interactions between bank and hillslopes groundwater, and streamwater, in a context of steep slopes (>50%) and rapid land use change (conversion of annual crops to teak plantation). This continuous ERT monitoring has been carried out along a representative 100 m long transect in the middle of the 65 ha catchment perpendicular to the stream. The data were collected every week during rainy season and every second week during dry season. It has been associated with hydrological monitoring (piezometers, limnimeters, gauging weirs). Such high resolution geophysical monitoring data set (approx. 900 apparent resistivity measurements for each acquisition) provides an invaluable non-invasive proxy of soil water content variations in the different layers of the vadose zone. It demonstrates: i) the influence of plant cover on water infiltration; ii) the pathways for vertical and horizontal water fluxes within the soil cover; iii) the control of soil organisation along the hillslope over the hydrological behaviour of the unsaturated part of the critical zone. (1) «Multi-Scale Environmental Changes» : http://msec.obs-mip.fr/ (2) «Observatoires de la Zone Critique Applications et Recherches» Including the former RBV (Réseau de Bassins Versants) : http://portailrbv.sedoo.fr/

  19. Modelling persistence in annual Australia point rainfall

    Directory of Open Access Journals (Sweden)

    J. P. Whiting

    2003-01-01

    Full Text Available Annual rainfall time series for Sydney from 1859 to 1999 is analysed. Clear evidence of nonstationarity is presented, but substantial evidence for persistence or hidden states is more elusive. A test of the hypothesis that a hidden state Markov model reduces to a mixture distribution is presented. There is strong evidence of a correlation between the annual rainfall and climate indices. Strong evidence of persistence of one of these indices, the Pacific Decadal Oscillation (PDO, is presented together with a demonstration that this is better modelled by fractional differencing than by a hidden state Markov model. It is shown that conditioning the logarithm of rainfall on PDO, the Southern Oscillation index (SOI, and their interaction provides realistic simulation of rainfall that matches observed statistics. Similar simulation models are presented for Brisbane, Melbourne and Perth. Keywords: Hydrological persistence,hidden state Markov models, fractional differencing, PDO, SOI, Australian rainfall

  20. Acidity in rainfall

    International Nuclear Information System (INIS)

    Tisue, G.T.; Kacoyannakis, J.

    1975-01-01

    The reported increasing acidity of rainfall raises many interesting ecological and chemical questions. In spite of extensive studies in Europe and North America there are, for example, great uncertainties in the relative contributions of strong and weak acids to the acid-base properties of rainwater. Unravelling this and similar problems may require even more rigorous sample collection and analytical procedures than previously employed. Careful analysis of titration curves permits inferences to be made regarding chemical composition, the possible response of rainwater to further inputs of acidic components to the atmosphere, and the behavior to be expected when rainwater interacts with the buffers present in biological materials and natural waters. Rainwater samples collected during several precipitation events at Argonne National Laboratory during October and November 1975 have been analyzed for pH, acid and base neutralizing properties, and the ions of ammonium, nitrate, chloride, sulfate, and calcium. The results are tabulated

  1. Flexible Strategies for Coping with Rainfall Variability: Seasonal Adjustments in Cropped Area in the Ganges Basin.

    Science.gov (United States)

    Siderius, Christian; Biemans, Hester; van Walsum, Paul E V; van Ierland, Ekko C; Kabat, Pavel; Hellegers, Petra J G J

    2016-01-01

    One of the main manifestations of climate change will be increased rainfall variability. How to deal with this in agriculture will be a major societal challenge. In this paper we explore flexibility in land use, through deliberate seasonal adjustments in cropped area, as a specific strategy for coping with rainfall variability. Such adjustments are not incorporated in hydro-meteorological crop models commonly used for food security analyses. Our paper contributes to the literature by making a comprehensive model assessment of inter-annual variability in crop production, including both variations in crop yield and cropped area. The Ganges basin is used as a case study. First, we assessed the contribution of cropped area variability to overall variability in rice and wheat production by applying hierarchical partitioning on time-series of agricultural statistics. We then introduced cropped area as an endogenous decision variable in a hydro-economic optimization model (WaterWise), coupled to a hydrology-vegetation model (LPJmL), and analyzed to what extent its performance in the estimation of inter-annual variability in crop production improved. From the statistics, we found that in the period 1999-2009 seasonal adjustment in cropped area can explain almost 50% of variability in wheat production and 40% of variability in rice production in the Indian part of the Ganges basin. Our improved model was well capable of mimicking existing variability at different spatial aggregation levels, especially for wheat. The value of flexibility, i.e. the foregone costs of choosing not to crop in years when water is scarce, was quantified at 4% of gross margin of wheat in the Indian part of the Ganges basin and as high as 34% of gross margin of wheat in the drought-prone state of Rajasthan. We argue that flexibility in land use is an important coping strategy to rainfall variability in water stressed regions.

  2. Flexible Strategies for Coping with Rainfall Variability: Seasonal Adjustments in Cropped Area in the Ganges Basin.

    Directory of Open Access Journals (Sweden)

    Christian Siderius

    Full Text Available One of the main manifestations of climate change will be increased rainfall variability. How to deal with this in agriculture will be a major societal challenge. In this paper we explore flexibility in land use, through deliberate seasonal adjustments in cropped area, as a specific strategy for coping with rainfall variability. Such adjustments are not incorporated in hydro-meteorological crop models commonly used for food security analyses. Our paper contributes to the literature by making a comprehensive model assessment of inter-annual variability in crop production, including both variations in crop yield and cropped area. The Ganges basin is used as a case study. First, we assessed the contribution of cropped area variability to overall variability in rice and wheat production by applying hierarchical partitioning on time-series of agricultural statistics. We then introduced cropped area as an endogenous decision variable in a hydro-economic optimization model (WaterWise, coupled to a hydrology-vegetation model (LPJmL, and analyzed to what extent its performance in the estimation of inter-annual variability in crop production improved. From the statistics, we found that in the period 1999-2009 seasonal adjustment in cropped area can explain almost 50% of variability in wheat production and 40% of variability in rice production in the Indian part of the Ganges basin. Our improved model was well capable of mimicking existing variability at different spatial aggregation levels, especially for wheat. The value of flexibility, i.e. the foregone costs of choosing not to crop in years when water is scarce, was quantified at 4% of gross margin of wheat in the Indian part of the Ganges basin and as high as 34% of gross margin of wheat in the drought-prone state of Rajasthan. We argue that flexibility in land use is an important coping strategy to rainfall variability in water stressed regions.

  3. Estimation of Rainfall Erosivity via 1-Minute to Hourly Rainfall Data from Taipei, Taiwan

    Science.gov (United States)

    Huang, Ting-Yin; Yang, Ssu-Yao; Jan, Chyan-Deng

    2017-04-01

    Soil erosion is a natural process on hillslopes that threats people's life and properties, having a considerable environmental and economic implications for soil degradation, agricultural activity and water quality. The rainfall erosivity factor (R-factor) in the Universal Soil Loss Equation (USLE), composed of total kinetic energy (E) and the maximum 30-min rainfall intensity (I30), is widely used as an indicator to measure the potential risks of soil loss caused by rainfall at a regional scale. This R factor can represent the detachment and entrainment involved in climate conditions on hillslopes, but lack of 30-min rainfall intensity data usually lead to apply this factor more difficult in many regions. In recent years, fixed-interval, hourly rainfall data is readily available and widely used due to the development of automatic weather stations. Here we assess the estimations of R, E, and I30 based on 1-, 5-, 10-, 15-, 30-, 60-minute rainfall data, and hourly rainfall data obtained from Taipei weather station during 2004 to 2010. Results show that there is a strong correlation among R-factors estimated from different interval rainfall data. Moreover, the shorter time-interval rainfall data (e.g., 1-min) yields larger value of R-factor. The conversion factors of rainfall erosivity (ratio of values estimated from the resolution lower than 30-min rainfall data to those estimated from 60-min and hourly rainfall data, respectively) range from 1.85 to 1.40 (resp. from 1.89 to 1.02) for 60-min (resp. hourly) rainfall data as the time resolution increasing from 30-min to 1-min. This paper provides useful information on estimating R-factor when hourly rainfall data is only available.

  4. Disturbance and long-term patterns of rainfall and throughfall nutrient fluxes in a subtropical wet forest in Puerto Rico

    Science.gov (United States)

    Heartsill-Scalley, T.; Scatena, F. N.; Estrada, C.; McDowell, W. H.; Lugo, A. E.

    2007-02-01

    SummaryNutrient fluxes in rainfall and throughfall were measured weekly in a mature subtropical wet forest in NE Puerto Rico over a 15-year period that included the effects of 10 named tropical storms, several prolonged dry periods, and volcanic activity in the region. Mean annual rainfall and throughfall were 3482 and 2131 mm yr -1, respectively. Average annual rainfall and throughfall fluxes of K, Ca, Mg, Cl, Na, and SO 4-S were similar but somewhat larger than those reported for most tropical forests. Rainfall inputs of nitrogen were comparatively low and reflect the relative isolation of the airshed. More constituents had seasonal differences in rainfall fluxes (6 out of 12) than throughfall fluxes (4 out of 12) and all volume weighted throughfall enrichment ratios calculated for the 15-year period were greater than one. However, median weekly enrichment ratios were less than 1 for sea salts and dissolved organic carbon, between 1 and 2 for Mg, Ca, SiO 2 and SO 4-S, and greater than 10 for NH 4-N, PO 4-P, and K. Droughts tended to reduce enrichment ratios of cations and sea-salts, but increased enrichment ratios of NH 4-N, PO 4-P, and K. In the weeks following hurricanes and tropical storms, relative throughfall tended to be higher and enrichment ratios tended to be lower. Saharan dust and the activity of Caribbean volcanoes can also be detected in the time series. Nevertheless, the impacts of particular events are variable and modified by the magnitude of the event, the pre- and post-event rainfall, and the time since the previous event. Rainfall, throughfall, rainfall pH, and rainfall fluxes of seven constituents had decreasing trends over the 15-year period. However, these decreases were small, less than inter-annual and annual variations, and not considered to be ecologically significant. These long-term observations indicate that physical and biological processes associated with water passing through the canopy act to buffer internal nutrient cycles from

  5. Origins of streamflow in a crystalline basement catchment in a sub-humid Sudanian zone: The Donga basin (Benin, West Africa): Inter-annual variability of water budget

    Science.gov (United States)

    Séguis, L.; Kamagaté, B.; Favreau, G.; Descloitres, M.; Seidel, J.-L.; Galle, S.; Peugeot, C.; Gosset, M.; Le Barbé, L.; Malinur, F.; Van Exter, S.; Arjounin, M.; Boubkraoui, S.; Wubda, M.

    2011-05-01

    SummaryDuring the last quarter of the 20th century, West Africa underwent a particularly intense and generalized drought. During this period, the biggest drops in streamflow were observed in the Sudanian zone rather than in the Sahelian zone, but the reasons are still poorly understood. In 2000, a meso-scale hydrological observatory was set up in the sub-humid Sudanian zone of the Upper Ouémé Valley (Benin). Three embedded catchments of 12-586 km 2 located on a crystalline bedrock were intensively instrumented to document the different terms of the water budget and to identify the main streamflow generating processes and base-flow mechanisms at different scales. Geophysical, hydrological and geochemical data were collected throughout the catchments from 2002 to 2006. Crossing these data helped define their hydrological functioning. The region has seasonal streamflow, and the permanent groundwater in the weathered mantle does not drain to rivers, instead, seasonal perched groundwaters are the major contributor to annual streamflow. The perched groundwaters are mainly located in seasonally waterlogged sandy layers in the headwater bottom-lands called bas-fonds in French-speaking West Africa of 1st order streams. During the period 2003-2006, regolith groundwater recharge ranged between 10% and 15% of the annual rainfall depth. Depletion of permanent groundwater during the dry season is probably explained by local evapotranspiration which was seen not to be limited to gallery forests. During the 4-year study period, a reduction of 20% in annual rainfall led to a 50% reduction in streamflow. This reduction was observed in the two components of the flow: direct runoff and drainage of perched groundwater. Thanks to the comprehensive dataset obtained, the results obtained for the Donga experimental catchment are now being extrapolated to the whole upper Ouémé valley, which can be considered as representative of sub-humid Sudanian rivers flowing on a crystalline

  6. Stochastic Modeling of Rainfall Series in Kelantan Using an Advanced Weather Generator

    Directory of Open Access Journals (Sweden)

    A. H. Syafrina

    2018-02-01

    Full Text Available Weather generator is a numerical tool that uses existing meteorological records to generate series of synthetic weather data. The AWE-GEN (Advanced Weather Generator model has been successful in producing a broad range of temporal scale weather variables, ranging from the high-frequency hourly values to the low-frequency inter-annual variability. In Malaysia, AWE-GEN has produced reliable projections of extreme rainfall events for some parts of Peninsular Malaysia. This study focuses on the use of AWE-GEN model to assess rainfall distribution in Kelantan. Kelantan is situated on the north east of the Peninsular, a region which is highly susceptible to flood. Embedded within the AWE-GEN model is the Neyman Scott process which employs parameters to represent physical rainfall characteristics. The use of correct probability distributions to represent the parameters is imperative to allow reliable results to be produced. This study compares the performance of two probability distributions, Weibull and Gamma to represent rainfall intensity and the better distribution found was used subsequently to simulate hourly scaled rainfall series. Thirty years of hourly scaled meteorological data from two stations in Kelantan were used in model construction. Results indicate that both probability distributions are capable of replicating the rainfall series at both stations very well, however numerical evaluations suggested that Gamma performs better. Despite Gamma not being a heavy tailed distribution, it is able to replicate the key characteristics of rainfall series and particularly extreme values. The overall simulation results showed that the AWE-GEN model is capable of generating tropical rainfall series which could be beneficial in flood preparedness studies in areas vulnerable to flood.

  7. Rainfall Variability of South East Queensland

    Science.gov (United States)

    Wilson, Louise; Manton, Michael; Siems, Steven

    2010-05-01

    February, with peak falls tending to be in February. The ‘wet' regimes are responsible for the majority of the region's rainfall. Southeasterly wind regimes are commonly associated with trade wind or ‘stream' showers and coastal trade wind cumulus. When there is significant moisture such as for the ‘moist' southeasterly regime these systems can bring significant rainfall to the region. The northwesterly regime can produce deep convection and contributes greatly to the total annual rainfall (21.7%) despite occurring less than 7% of the time. The easterly and westerly regimes also are major contributors to annual rainfall. There are also significant rainfall events during the dry season such as intense sub-tropical cyclones (east-coast lows) that bring sustained strong winds and intense rainfall to the region. In general, however, the winter season is dry and is well described by a southwesterly regime and a ‘dry' southeasterly regime. The dominant synoptic regime, the southeasterly regime, does not contribute significantly to the total rainfall in any month. The relationship between the Southern Oscillation Index (SOI) and rainfall over most of Queensland is strong. The correlation between SEQ monthly rainfall anomalies and the Southern Oscillation Index (SOI) was calculated over the period 1858-2008. A small but significant correlation is found between the SOI and rainfall in southeastern Queensland. The low correlation indicates that the rainfall is controlled by other factors in addition to the El Nino - Southern Oscillation.

  8. Darfur: rainfall and conflict

    International Nuclear Information System (INIS)

    Kevane, Michael; Gray, Leslie

    2008-01-01

    Data on rainfall patterns only weakly corroborate the claim that climate change explains the Darfur conflict that began in 2003 and has claimed more than 200 000 lives and displaced more than two million persons. Rainfall in Darfur did not decline significantly in the years prior to the eruption of major conflict in 2003; rainfall exhibited a flat trend in the thirty years preceding the conflict (1972-2002). The rainfall evidence suggests instead a break around 1971. Rainfall is basically stationary over the pre- and post-1971 sub-periods. The break is larger for the more northerly rainfall stations, and is less noticeable for En Nahud. Rainfall in Darfur did indeed decline, but the decline happened over 30 years before the conflict erupted. Preliminary analysis suggests little merit to the proposition that a structural break several decades earlier is a reasonable predictor of the outbreak of large-scale civil conflict in Africa

  9. Extreme Rainfall In A City

    Science.gov (United States)

    Nkemdirim, Lawrence

    industrialization. The development of small cloud droplets into larger particles requires time. A single thunderstorm cell has a mean development time of about 20 minutes and a life time of around 45 minutes with a mean mind of 10m/s, an air parcel would travel 12 km from the beginning of droplet formation to the first precipitation. That means that the precipitation field is shifted downwind of settlements. It could also explain the the higher frequency of the trace to small amounts observed in Calgary since those events occur under relatively calm weather. Whereas the majority of studies have focused on summer convectional type events, little appears to have been done on the extreme rainfall events on which most structural designs are based. Is there a detectable urban bias in these events? Do urban areas intensify them? What are the implications of point distribution of extreme rainfall events on flood frequency across a city. This paper examines the spatial distribution of the mean annual maximum rainfall event in Calgary, Canada, with a view to determining the relative contribution of geographical setting and urbanisation to point patterns. The data are subsequently maximized to produce maps of probable maximum precipitation for the city. The major results are as follows: (a) position along storm path is the most important variable determining maximum rainfall hazard, (b) higher grounds receive up to seventy percent more maximum rainfall than values based on spatial trend, (c) urban structure and geometry correlate negatively with maximum rainfall intensity, however, (d) zones of maximum flood peaks are found down slope of areas of maximum precipitation increasing flood hazard in the inner city in spite of its lower precipitation. Drainage networks based on point rainfall patterns have proved grossly inadequate for flood mitigation. The new design based on this study recognizes the strong moisture gradients caused by rapid movement of water and other elements down slope. Snow

  10. Integration Of Spa Tio- Temporal Analysis Of Rainfall And Community Information System To Reduce Landslide Risk In Indonesia

    Directory of Open Access Journals (Sweden)

    Sudibyakto .

    2013-07-01

    Full Text Available Indonesia is vulnerable to many type of disasters including natural and anthropogenic disasters. Indonesian seasonal rainfall also shows inter annual variation. Sediment-related disaster such as landslide is the mostji-equent disaster occurred and significantly was impacted to natural, human. and social environment. Although. many disaster mitigation e.Oorts have been conducted to reduce disaster risk there are still urgently need to improve the early 1varning .\\~ystem by communicating the risk into local community. Integration qf spatialtemporal analysis qf rainfall and disaster management information !o~vstem would be required to improve the better disaster management in Indonesia. Application of Disaster A1anagement Information System in the study area will presented including evacuation map that used by the local community.

  11. Will seasonally dry tropical forests be sensitive or resistant to future changes in rainfall regimes?

    Science.gov (United States)

    Allen, Kara; Dupuy, Juan Manuel; Gei, Maria G.; Hulshof, Catherine; Medvigy, David; Pizano, Camila; Salgado-Negret, Beatriz; Smith, Christina M.; Trierweiler, Annette; Van Bloem, Skip J.; Waring, Bonnie G.; Xu, Xiangtao; Powers, Jennifer S.

    2017-02-01

    Seasonally dry tropical forests (SDTF) are located in regions with alternating wet and dry seasons, with dry seasons that last several months or more. By the end of the 21st century, climate models predict substantial changes in rainfall regimes across these regions, but little is known about how individuals, species, and communities in SDTF will cope with the hotter, drier conditions predicted by climate models. In this review, we explore different rainfall scenarios that may result in ecological drought in SDTF through the lens of two alternative hypotheses: 1) these forests will be sensitive to drought because they are already limited by water and close to climatic thresholds, or 2) they will be resistant/resilient to intra- and inter-annual changes in rainfall because they are adapted to predictable, seasonal drought. In our review of literature that spans microbial to ecosystem processes, a majority of the available studies suggests that increasing frequency and intensity of droughts in SDTF will likely alter species distributions and ecosystem processes. Though we conclude that SDTF will be sensitive to altered rainfall regimes, many gaps in the literature remain. Future research should focus on geographically comparative studies and well-replicated drought experiments that can provide empirical evidence to improve simulation models used to forecast SDTF responses to future climate change at coarser spatial and temporal scales.

  12. Comparison between Vegetation and Rainfall of Bioclimatic Ecoregions in Central Africa

    Directory of Open Access Journals (Sweden)

    Sonfack Rousvel

    2013-11-01

    Full Text Available This paper investigates the relationship between the Normalized Difference Vegetation Index (NDVI and extracted rainfall in the Global Precipitation Climatology Project (GPCP in Central Africa between latitudes 15°S and 20°N and longitudes 0°E and 31°E. Monthly NDVI and GPCP datasets for the period 1982–2000 have been used. The Index of Segmentation of Fourier Components (ISFC has been applied on the NDVI dataset to segment Central Africa into four bioclimatic ecoregions (BCERs. In order to compare the differential response of vegetation growth to rainfall, an analysis of the inter-annual, intra-annual and seasonal variability for each BCER has been carried out, and the correlations between NDVI and rainfall have been assessed. The plot of the annual cycles of both variables revealed a coherent onset, peak and decay, with a time lag of 1 month for almost all the zones, except the zones, semi-desert and steppe, where a season of short and intense rainfall was observed. The correlation coefficients computed between the two variables are relatively high, especially in brush-grass savannah, where they reach up to 0.90 at a time lag of 1 month. The phenological transition points and phases show that the range between the +1 and

  13. Rainfall simulation in education

    Science.gov (United States)

    Peters, Piet; Baartman, Jantiene; Gooren, Harm; Keesstra, Saskia

    2016-04-01

    Rainfall simulation has become an important method for the assessment of soil erosion and soil hydrological processes. For students, rainfall simulation offers an year-round, attractive and active way of experiencing water erosion, while not being dependent on (outdoors) weather conditions. Moreover, using rainfall simulation devices, they can play around with different conditions, including rainfall duration, intensity, soil type, soil cover, soil and water conservation measures, etc. and evaluate their effect on erosion and sediment transport. Rainfall simulators differ in design and scale. At Wageningen University, both BSc and MSc student of the curriculum 'International Land and Water Management' work with different types of rainfall simulation devices in three courses: - A mini rainfall simulator (0.0625m2) is used in the BSc level course 'Introduction to Land Degradation and Remediation'. Groups of students take the mini rainfall simulator with them to a nearby field location and test it for different soil types, varying from clay to more sandy, slope angles and vegetation or litter cover. The groups decide among themselves which factors they want to test and they compare their results and discuss advantage and disadvantage of the mini-rainfall simulator. - A medium sized rainfall simulator (0.238 m2) is used in the MSc level course 'Sustainable Land and Water Management', which is a field practical in Eastern Spain. In this course, a group of students has to develop their own research project and design their field measurement campaign using the transportable rainfall simulator. - Wageningen University has its own large rainfall simulation laboratory, in which a 15 m2 rainfall simulation facility is available for research. In the BSc level course 'Land and Water Engineering' Student groups will build slopes in the rainfall simulator in specially prepared containers. Aim is to experience the behaviour of different soil types or slope angles when (heavy) rain

  14. An all-timescales rainfall probability distribution

    Science.gov (United States)

    Papalexiou, S. M.; Koutsoyiannis, D.

    2009-04-01

    The selection of a probability distribution for rainfall intensity at many different timescales simultaneously is of primary interest and importance as typically the hydraulic design strongly depends on the rainfall model choice. It is well known that the rainfall distribution may have a long tail, is highly skewed at fine timescales and tends to normality as the timescale increases. This behaviour, explained by the maximum entropy principle (and for large timescales also by the central limit theorem), indicates that the construction of a "universal" probability distribution, capable to adequately describe the rainfall in all timescales, is a difficult task. A search in hydrological literature confirms this argument, as many different distributions have been proposed as appropriate models for different timescales or even for the same timescale, such as Normal, Skew-Normal, two- and three-parameter Log-Normal, Log-Normal mixtures, Generalized Logistic, Pearson Type III, Log-Pearson Type III, Wakeby, Generalized Pareto, Weibull, three- and four-parameter Kappa distribution, and many more. Here we study a single flexible four-parameter distribution for rainfall intensity (the JH distribution) and derive its basic statistics. This distribution incorporates as special cases many other well known distributions, and is capable of describing rainfall in a great range of timescales. Furthermore, we demonstrate the excellent fitting performance of the distribution in various rainfall samples from different areas and for timescales varying from sub-hourly to annual.

  15. Seasonal and inter-annual eutrophication dynamics in a hypereutrophic shallow coastal lagoon from ten years of satellite observations and in-situ data

    Science.gov (United States)

    Pitarch, Jaime; Ruiz-Verdú, Antonio; Soria, Juan M.; Santoleri, Rosalia

    2016-04-01

    The Albufera de Valencia (39.33 N, 0.37 W) is a hypereutrophic shallow coastal lagoon, having a near round shape of ~ 5 km diameter and ~ 1 m average depth. At the west side, the lake is separated from the sea by a narrow land strip, but three artificial channels allow connection to the sea, regulated by gates. The rest of the lake is surrounded by rice fields that were made by gaining surface from the lake around a century ago. Nowadays, the ecological state of the lake is very degraded. Freshwater inflow is insufficient and residence time is too high. Despite some improvements in waste water treatment, high loads of sediment-stored nutrients are often resuspended due to habitual strong winds and made available for primary production. The previously abundant bottom vegetation disappeared decades ago and secchi depth does not reach more than few tens of centimeters. The lake suffers from cyanobacterial blooms and massive fish deaths. Despite its vital importance as a coastal wetland in the western Mediterranean region, its water quality is not routinely monitored, so its seasonality and eventual blooming events have not been sistematically studied. In this study, we aim at filling this gap using satellite data. Medium-resolution satellite-borne sensors constitute an appropriate tool for this sake due to the lake's medium size and little cloud cover time over the region. In particular, the European MERIS sensor (2002-2012) is specially well suited due to its unique spectral bands configuration for cyanobacterial detection. Apart from the utility of the results themselves, study of this sensor provides a strong baseline for operational utilization of its successor, the new-coming European Sentinel 3-OLCI sensor. We have processed the full archived MERIS archived data. By adequate choice of band ratios and posterior calibration to in-situ samples, the time series of chlorophyll concentration is derived. Derived seasonality reveals a pattern that is determined by the

  16. Optimization of rainfall networks using information entropy and temporal variability analysis

    Science.gov (United States)

    Wang, Wenqi; Wang, Dong; Singh, Vijay P.; Wang, Yuankun; Wu, Jichun; Wang, Lachun; Zou, Xinqing; Liu, Jiufu; Zou, Ying; He, Ruimin

    2018-04-01

    Rainfall networks are the most direct sources of precipitation data and their optimization and evaluation are essential and important. Information entropy can not only represent the uncertainty of rainfall distribution but can also reflect the correlation and information transmission between rainfall stations. Using entropy this study performs optimization of rainfall networks that are of similar size located in two big cities in China, Shanghai (in Yangtze River basin) and Xi'an (in Yellow River basin), with respect to temporal variability analysis. Through an easy-to-implement greedy ranking algorithm based on the criterion called, Maximum Information Minimum Redundancy (MIMR), stations of the networks in the two areas (each area is further divided into two subareas) are ranked during sliding inter-annual series and under different meteorological conditions. It is found that observation series with different starting days affect the ranking, alluding to the temporal variability during network evaluation. We propose a dynamic network evaluation framework for considering temporal variability, which ranks stations under different starting days with a fixed time window (1-year, 2-year, and 5-year). Therefore, we can identify rainfall stations which are temporarily of importance or redundancy and provide some useful suggestions for decision makers. The proposed framework can serve as a supplement for the primary MIMR optimization approach. In addition, during different periods (wet season or dry season) the optimal network from MIMR exhibits differences in entropy values and the optimal network from wet season tended to produce higher entropy values. Differences in spatial distribution of the optimal networks suggest that optimizing the rainfall network for changing meteorological conditions may be more recommended.

  17. Understanding litter decomposition in semiarid ecosystems: linking leaf traits, UV exposure and rainfall variability.

    Science.gov (United States)

    Gaxiola, Aurora; Armesto, Juan J

    2015-01-01

    Differences in litter quality, microbial activity or abiotic conditions cannot fully account for the variability in decomposition rates observed in semiarid ecosystems. Here we tested the role of variation in litter quality, water supply, and UV radiation as drivers of litter decomposition in arid lands. And show that carry-over effects of litter photodegradation during dry periods can regulate decomposition during subsequent wet periods. We present data from a two-phase experiment, where we first exposed litter from a drought-deciduous and an evergreen shrub to natural UV levels during five, rainless summer months and, subsequently, in the laboratory, we assessed the carry-over effects of photodegradation on biomass loss under different irrigation treatments representing the observed range of local rainfall variation among years (15-240 mm). Photodegradation of litter in the field produced average carbon losses of 12%, but deciduous Proustia pungens lost >25%, while evergreen Porlieria chilensis less than 5%. Natural exposure to UV significantly reduced carbon-to-nitrogen and lignin:N ratios in Proustia litter but not in Porlieria. During the subsequent wet phase, remaining litter biomass was lower in Proustia than in Porlieria. Indeed UV exposure increased litter decomposition of Proustia under low and medium rainfall treatments, whereas no carry-over effects were detected under high rainfall treatment. Consequently, for deciduous Proustia carry-over effects of UV exposure were negligible under high irrigation. Litter decomposition of the evergreen Porlieria depended solely on levels of rainfall that promote microbial decomposers. Our two-phase experiment revealed that both the carry-over effects of photodegradation and litter quality, modulated by inter-annual variability in rainfall, can explain the marked differences in decomposition rates and the frequent decoupling between rainfall and litter decomposition observed in semiarid ecosystems.

  18. Understanding litter decomposition in semiarid ecosystems: linking leaf traits, UV exposure and rainfall variability.

    Directory of Open Access Journals (Sweden)

    Aurora eGaxiola

    2015-03-01

    Full Text Available Differences in litter quality, microbial activity or abiotic conditions cannot fully account for the variability in decomposition rates observed in semiarid ecosystems. Here we tested the role of variation in litter quality, water supply, and UV radiation as drivers of litter decomposition in arid lands. And show that carry-over effects of litter photodegradation during dry periods can regulate decomposition during subsequent wet periods. We present data from a two-phase experiment, where we first exposed litter from a drought-deciduous and an evergreen shrub to natural UV levels during five, rainless summer-months and, subsequently, in the laboratory, we assessed the carry-over effects of photodegradation on biomass loss under different irrigation treatments representing the observed range of local rainfall variation among years (15 to 240 mm. Photodegradation of litter in the field produced average carbon losses of 12%, but deciduous Proustia pungens lost >25%, while evergreen Porlieria chilensis less than 5%. Natural exposure to UV significantly reduced carbon-to-nitrogen and lignin:N ratios in Proustia litter but not in Porlieria. During the subsequent wet phase, remaining litter biomass was lower in Proustia than in Porlieria. Indeed UV exposure increased litter decomposition of Proustia under low and medium rainfall treatments, whereas no carry-over effects were detected under high rainfall treatment. Consequently, for decidous Proustia carry-over effects of UV exposure were negligible under high irrigation. Litter decomposition of the evergreen Porlieria depended solely on levels of rainfall that promote microbial decomposers. Our two-phase experiment revealed that both the carry-over effects of photodegradation and litter quality, modulated by inter-annual variability in rainfall, can explain the marked differences in decomposition rates and the frequent decoupling between rainfall and litter decomposition observed in semiarid ecosystems.

  19. Tree-Ring Reconstruction of Wet Season Rainfall Totals in the Amazon

    Science.gov (United States)

    Stahle, D. W.; Lopez, L.; Granato-Souza, D.; Barbosa, A. C. M. C.; Torbenson, M.; Villalba, R.; Pereira, G. D. A.; Feng, S.; Schongart, J.; Cook, E. R.

    2017-12-01

    The Amazon Basin is a globally important center of deep atmospheric convection, energy balance, and biodiversity, but only a handful of weather stations in this vast Basin have recorded rainfall measurements for at least 50 years. The available rainfall and river level observations suggest that the hydrologic cycle in the Amazon may have become amplified in the last 40-years, with more extreme rainfall and streamflow seasonality, deeper droughts, and more severe flooding. These changes in the largest hydrological system on earth may be early evidence of the expected consequences of anthropogenic climate change and deforestation in the coming century. Placing these observed and simulated changes in the context of natural climate variability during the late Holocene is a significant challenge for high-resolution paleoclimatology. We have developed exactly dated and well-replicated annual tree-ring chronologies from two native Amazonian tree species (Cedrela sp and Centrolobium microchaete). These moisture sensitive chronologies have been used to compute two reconstructions of wet season rainfall totals, one in the southern Amazon based on Centrolobium and another in the eastern equatorial Amazon using Cedrela. Both reconstructions are over 200-years long and extend the available instrumental observations in each region by over 150-years. These reconstructions are well correlated with the same regional and large-scale climate dynamics that govern the inter-annual variability of the instrumental wet season rainfall totals. Increased multi-decadal variability is reconstructed after 1950 with the Centrolobium chronologies in the southern Amazon. The Cedrela reconstruction from the eastern Amazon exhibits changes in the spatial pattern of correlation with regional rainfall stations and the large-scale sea surface temperature field after 1990 that may be consistent with recent changes in the mean position of the Inter-Tropical Convergence Zone in March over the western

  20. Inter-annual and geographical variations in the extent of bare ice and dark ice on the Greenland ice sheet derived from MODIS satellite images

    Directory of Open Access Journals (Sweden)

    Rigen eShimada

    2016-04-01

    Full Text Available Areas of dark ice have appeared on the Greenland ice sheet every summer in recent years. These are likely to have a great impact on the mass balance of the ice sheet because of their low albedo. We report annual and geographical variations in the bare ice and dark ice areas that appeared on the Greenland Ice Sheet from 2000 to 2014 by using MODIS satellite images. The July monthly mean of the extent of bare ice showed a positive trend over these 15 years, and large annual variability ranging from 89,975 km2 to 279,075 km2, 5% and 16% of the entire ice sheet, respectively. The extent of dark ice also showed a positive trend and varied annually, ranging from 3,575 km2 to 26,975 km2, 4% and 10% of the bare ice extent. These areas are geographically varied, and their expansion is the greatest on the western side, particularly the southwestern side of the ice sheet. The bare ice extent correlates strongly with the monthly mean air temperature in July, suggesting that the extent was determined by snow melt. The dark ice extent also correlates with the air temperature; however, the correlation is weaker. The dark ice extent further correlates negatively with solar radiation. This suggests that the extent of dark ice is not only controlled by snow melt on the ice, but also by changes in the surface structures of the bare ice surface, such as cryoconite holes, which are associated with impurities appearing on the ice surface.

  1. Inter-annual and geographical variations in the extent of bare ice and dark ice on the Greenland ice sheet derived from MODIS satellite images

    Science.gov (United States)

    Shimada, Rigen; Takeuchi, Nozomu; Aoki, Teruo

    2016-04-01

    Areas of dark ice have appeared on the Greenland ice sheet every summer in recent years. These are likely to have a great impact on the mass balance of the ice sheet because of their low albedo. We report annual and geographical variations in the bare ice and dark ice areas that appeared on the Greenland Ice Sheet from 2000 to 2014 by using MODIS satellite images. The July monthly mean of the extent of bare ice showed a positive trend over these 15 years, and large annual variability ranging from 89,975 km2 to 279,075 km2, 5% and 16% of the entire ice sheet, respectively. The extent of dark ice also showed a positive trend and varied annually, ranging from 3,575 km2 to 26,975 km2, 4% and 10% of the bare ice extent. These areas are geographically varied, and their expansion is the greatest on the western side, particularly the southwestern side of the ice sheet. The bare ice extent correlates strongly with the monthly mean air temperature in July, suggesting that the extent was determined by snow melt. The dark ice extent also correlates with the air temperature; however, the correlation is weaker. The dark ice extent further correlates negatively with solar radiation. This suggests that the extent of dark ice is not only controlled by snow melt on the ice, but also by changes in the surface structures of the bare ice surface, such as cryoconite holes, which are associated with impurities appearing on the ice surface.

  2. Rainfall erosivity: An historical review

    Science.gov (United States)

    Rainfall erosivity is the capability of rainfall to cause soil loss from hillslopes by water. Modern definitions of rainfall erosivity began with the development of the Universal Soil Loss Equation (USLE), where rainfall characteristics were statistically related to soil loss from thousands of plot...

  3. Occurrence of heavy rainfall around the confluence line in monsoon ...

    Indian Academy of Sciences (India)

    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 ...

  4. Numerical representation of rainfall field in the Yarmouk River Basin

    Science.gov (United States)

    Shentsis, Isabella; Inbar, Nimrod; Magri, Fabien; Rosenthal, Eliyahu

    2017-04-01

    Rainfall is the decisive factors in evaluating the water balance of river basins and aquifers. Accepted methods rely on interpolation and extrapolation of gauged rain to regular grid with high dependence on the density and regularity of network, considering the relief complexity. We propose an alternative method that makes up to those restrictions by taking into account additional physical features of the rain field. The method applies to areas with (i) complex plain- and mountainous topography, which means inhomogeneity of the rainfall field and (ii) non-uniform distribution of a rain gauge network with partial lack of observations. The rain model is implemented in two steps: 1. Study of the rainfall field, based on the climatic data (mean annual precipitation), its description by the function of elevation and other factors, and estimation of model parameters (normalized coefficients of the Taylor series); 2. Estimation of rainfall in each historical year using the available data (less complete and irregular versus climatic data) as well as the a-priori known parameters (by the basic hypothesis on inter-annual stability of the model parameters). The proposed method was developed by Shentsis (1990) for hydrological forecasting in Central Asia and was later adapted to the Lake Kinneret Basin. Here this model (the first step) is applied to the Yarmouk River Basin. The Yarmouk River is the largest tributary of the Jordan River. Its transboundary basin (6,833 sq. km) extends over Syria (5,257 sq.km), Jordan (1,379 sq. km) and Israel (197 sq. km). Altitude varies from 1800 m (and more) to -235 m asl. The total number of rain stations in use is 36 (17 in Syria, 19 in Jordan). There is evidently lack and non-uniform distribution of a rain gauge network in Syria. The Yarmouk Basin was divided into five regions considering typical relationship between mean annual rain and elevation for each region. Generally, the borders of regions correspond to the common topographic

  5. Multifractals and the temporal structure of rainfall

    NARCIS (Netherlands)

    Lima, de M.I.P.

    1998-01-01

    Rainfall is a highly non-linear hydrological process that exhibits wide variability over a broad range of time and space scales. The strongly irregular fluctuations of rain are difficult to capture instrumentally and to handle mathematically. The purpose of this work is to contribute to a

  6. Reduced-complexity multi-site rainfall generation: one million years over night using the model TripleM

    Science.gov (United States)

    Breinl, Korbinian; Di Baldassarre, Giuliano; Girons Lopez, Marc

    2017-04-01

    We assess uncertainties of multi-site rainfall generation across spatial scales and different climatic conditions. Many research subjects in earth sciences such as floods, droughts or water balance simulations require the generation of long rainfall time series. In large study areas the simulation at multiple sites becomes indispensable to account for the spatial rainfall variability, but becomes more complex compared to a single site due to the intermittent nature of rainfall. Weather generators can be used for extrapolating rainfall time series, and various models have been presented in the literature. Even though the large majority of multi-site rainfall generators is based on similar methods, such as resampling techniques or Markovian processes, they often become too complex. We think that this complexity has been a limit for the application of such tools. Furthermore, the majority of multi-site rainfall generators found in the literature are either not publicly available or intended for being applied at small geographical scales, often only in temperate climates. Here we present a revised, and now publicly available, version of a multi-site rainfall generation code first applied in 2014 in Austria and France, which we call TripleM (Multisite Markov Model). We test this fast and robust code with daily rainfall observations from the United States, in a subtropical, tropical and temperate climate, using rain gauge networks with a maximum site distance above 1,000km, thereby generating one million years of synthetic time series. The modelling of these one million years takes one night on a recent desktop computer. In this research, we first start the simulations with a small station network of three sites and progressively increase the number of sites and the spatial extent, and analyze the changing uncertainties for multiple statistical metrics such as dry and wet spells, rainfall autocorrelation, lagged cross correlations and the inter-annual rainfall

  7. Effect of climate, intra and inter-annual variability, on nutrients emission (C,N, P) in stream water: lessons from an agricultural long term observatory of the temperate zone

    Science.gov (United States)

    Gascuel-Odoux, Chantal; Remi, Dupas; Patrick, Durand; Ophélie, Fovet; Gerard, Gruau; Anne, Jaffrezic; Guillaume, Humbert; Philippe, Merot; Gu, Sen

    2016-04-01

    Agriculture greatly contributes to modify C, N and P cycles, particularly in animal breeding regions due to high inputs. Climatic conditions, intra and inter-annual variabilities, modify nutrient stream water emissions, acting in time on transfer and transformation, accumulation and mobilization processes, connecting and disconnecting in time different compartments (soil, riparian areas, groundwater). In agricultural catchments, nutrient perturbations are dominated by agricultural land use, and decoupling human activities and climate effects is far from easy. Climate change generally appears as a secondary driver compared to land use. If studied, generally only one nutrient is considered. Only long term, high frequency and multiple element data series can decouple these two drivers. The Kervidy-Naizin watershed belongs to the AgrHyS environmental research observatory (http://www6.inra.fr/ore_agrhys_eng), itself included in RBV (French catchment network of the CZO). On this catchment, 6 years of daily data on DOC, NO3, SRP, TP concentrations allow us to analyze the effect of seasonal and inter-annual climatic variabilities on water quality (C, N, P). Different papers have been published on the effect of climate on nitrate (Molenat et al, 2008), SRP and TP (Dupas et al, 2015) and DOC (Humbert et al, 2015). We will present first results comparing the effect of climate on these three major solute forms of C, N and P. While C and P dynamics are very close and controlled by fluctuation of water table downslope, i.e. in riparian areas, mobilizing C and P in time, nitrate dynamics is controlled by GW dynamics upslope acting as the major N reservoir. As example, the dryness conditions in summer appears a key factor of the C and P emissions in autumn. All the three solute forms interact when anoxic conditions are observed in riparian zones. These basic processes explain how climatic variability can influence and explain interactions between C, N and P emissions in stream

  8. Seasonal and inter-annual variability of aerosol optical properties during 2005-2010 over Red Mountain Pass and Impact on the Snow Cover of the San Juan Mountains

    Science.gov (United States)

    Singh, R. P.; Gautam, R.; Painter, T. H.

    2011-12-01

    Growing body of evidence suggests the significant role of aerosol solar absorption in accelerated seasonal snowmelt in the cryosphere and elevated mountain regions via snow contamination and radiative warming processes. Characterization of aerosol optical properties over seasonal snow cover and snowpacks is therefore important towards the better understanding of aerosol radiative effects and associated impact on snow albedo. In this study, we present seasonal variations in column-integrated aerosol optical properties retrieved from AERONET sunphotometer measurements (2005-2010) at Red Mountain Pass (37.90° N, 107.72° W, 3368 msl) in the San Juan Mountains, in the vicinity of the North American Great Basin and Colorado Plateau deserts. The aerosol optical depth (AOD) measured at 500nm is generally low (pollutant transport. In addition, the possibility of the observed increased coarse-mode influence associated with mineral dust influx cannot be ruled out, due to westerly-airmass driven transport from arid/desert regions as suggested by backward trajectory simulations. A meteorological coupling is also found in the summer season between AOD and column water vapor retrieved from AERONET with co-occurring enhanced water vapor and AOD. Based on column measurements, it is difficult to ascertain the aerosol composition, however, the summer-time enhanced aerosol loading as presented here is consistent with the increased dust deposition in the San Juan mountain snow cover as reported in recent studies. In summary, this study is expected to better understand the seasonal and inter-annual aerosol column variations and is an attempt to provide an insight into the effects of aerosol solar absorption on accelerated seasonal snowmelt in the San Juan mountains.

  9. Rainfall erosivity in Europe.

    Science.gov (United States)

    Panagos, Panos; Ballabio, Cristiano; Borrelli, Pasquale; Meusburger, Katrin; Klik, Andreas; Rousseva, Svetla; Tadić, Melita Perčec; Michaelides, Silas; Hrabalíková, Michaela; Olsen, Preben; Aalto, Juha; Lakatos, Mónika; Rymszewicz, Anna; Dumitrescu, Alexandru; Beguería, Santiago; Alewell, Christine

    2015-04-01

    Rainfall is one the main drivers of soil erosion. The erosive force of rainfall is expressed as rainfall erosivity. Rainfall erosivity considers the rainfall amount and intensity, and is most commonly expressed as the R-factor in the USLE model and its revised version, RUSLE. At national and continental levels, the scarce availability of data obliges soil erosion modellers to estimate this factor based on rainfall data with only low temporal resolution (daily, monthly, annual averages). The purpose of this study is to assess rainfall erosivity in Europe in the form of the RUSLE R-factor, based on the best available datasets. Data have been collected from 1541 precipitation stations in all European Union (EU) Member States and Switzerland, with temporal resolutions of 5 to 60 min. The R-factor values calculated from precipitation data of different temporal resolutions were normalised to R-factor values with temporal resolutions of 30 min using linear regression functions. Precipitation time series ranged from a minimum of 5 years to a maximum of 40 years. The average time series per precipitation station is around 17.1 years, the most datasets including the first decade of the 21st century. Gaussian Process Regression (GPR) has been used to interpolate the R-factor station values to a European rainfall erosivity map at 1 km resolution. The covariates used for the R-factor interpolation were climatic data (total precipitation, seasonal precipitation, precipitation of driest/wettest months, average temperature), elevation and latitude/longitude. The mean R-factor for the EU plus Switzerland is 722 MJ mm ha(-1) h(-1) yr(-1), with the highest values (>1000 MJ mm ha(-1) h(-1) yr(-1)) in the Mediterranean and alpine regions and the lowest (<500 MJ mm ha(-1) h(-1) yr(-1)) in the Nordic countries. The erosivity density (erosivity normalised to annual precipitation amounts) was also the highest in Mediterranean regions which implies high risk for erosive events and floods

  10. Possible impacts of spring sea surface temperature anomalies over South Indian Ocean on summer rainfall in Guangdong-Guangxi region of China

    Science.gov (United States)

    Jin, Dachao; Guan, Zhaoyong; Huo, Liwei; Wang, Xudong

    2017-11-01

    Based on observational and reanalysis data for 1979-2015, the possible impacts of spring sea surface temperature anomalies (SSTA) over the South Indian Ocean on the inter-annual variations of summer rainfall in Guangdong and Guangxi Provinces (i.e., the Guangdong-Guangxi area, GG) were analysed in this study. The physical mechanism behind these impacts was explored. Two geographic regions over [65°E-95°E, 35°S-25°S] and [90°E-110°E, 20°S-5°S] were defined as the western pole region and the eastern pole region, respectively, for the GG summer precipitation (PGG)-related South Indian Ocean dipole SSTA pattern (R-SIODP). The difference between springtime SST anomalies averaged over the western pole region and that averaged over the eastern pole region was defined as the R-SIODP index. The correlation between the spring R-SIODP index and GG summer precipitation can reach up to 0.52. In the spring of positive R-SIODP anomaly, southerly winds over the western pole of the R-SIODP weaken, whereas the southeast trade winds over the eastern pole strengthen. By means of the wind-evaporation-SST feedback mechanism, the enhanced southeast trade winds can weaken the evaporation over the western pole of the R-SIODP and enhance the evaporation over the eastern pole. This results in a sustained positive SSTA in the western pole of the R-SIODP and a sustained negative SSTA in the eastern pole, whereby the distribution of the SSTAs maintains until summer. The SST dipole abnormally enhances the cross-equatorial airflow near 105°E, which intensifies the anomalous anti-cyclonic circulation over South China Sea at 850 hPa and simultaneously results in abnormal enhancement of water vapour transport to GG. Additionally, the SST dipole promotes abnormal divergence in the lower troposphere and abnormal convergence in the upper troposphere over the maritime continent (MC) region. Moreover, the low-level convergence in GG is enhanced, which results in abnormal enhancement of ascending

  11. Relating rainfall characteristics to cloud top temperatures at different scales

    Science.gov (United States)

    Klein, Cornelia; Belušić, Danijel; Taylor, Christopher

    2017-04-01

    Extreme rainfall from mesoscale convective systems (MCS) poses a threat to lives and livelihoods of the West African population through increasingly frequent devastating flooding and loss of crops. However, despite the significant impact of such extreme events, the dominant processes favouring their occurrence are still under debate. In the data-sparse West African region, rainfall radar data from the Tropical Rainfall Measuring Mission (TRMM) gives invaluable information on the distribution and frequency of extreme rainfall. The TRMM 2A25 product provides a 15-year dataset of snapshots of surface rainfall from 2-4 overpasses per day. Whilst this sampling captures the overall rainfall characteristics, it is neither long nor frequent enough to diagnose changes in MCS properties, which may be linked to the trend towards rainfall intensification in the region. On the other hand, Meteosat geostationary satellites provide long-term sub-hourly records of cloud top temperatures, raising the possibility of combining these with the high-quality rainfall data from TRMM. In this study, we relate TRMM 2A25 rainfall to Meteosat Second Generation (MSG) cloud top temperatures, which are available from 2004 at 15 minutes intervals, to get a more detailed picture of the structure of intense rainfall within the life cycle of MCS. We find TRMM rainfall intensities within an MCS to be strongly coupled with MSG cloud top temperatures: the probability for extreme rainfall increases from power spectra at scales between 15 and 200km. From these, cloud sub-structures are identified as circular areas of respective scale with local power maxima in their centre. These areas are then mapped onto coinciding TRMM rainfall, allowing us to assign rainfall fields to sub-cloud features of different scales. We find a higher probability for extreme rainfall for cloud features above a scale of 30km, with features 100km contributing most to the number of extreme rainfall pixels. Over the average diurnal

  12. Historical and future seasonal rainfall variability in Nusa Tenggara Barat Province, Indonesia: Implications for the agriculture and water sectors

    Directory of Open Access Journals (Sweden)

    Dewi G.C. Kirono

    2016-01-01

    Full Text Available Climate change impacts are most likely to be felt by resource-dependent communities, and consequently locally-relevant data are necessary to inform livelihood adaptation planning. This paper presents information for historical and future seasonal rainfall variability in Nusa Tenggara Barat (NTB Province, Indonesia, where rural livelihoods are highly vulnerable to current climate variability and future change. Historical rainfall variability is investigated using observational data from two stations located on the islands of Lombok and Sumbawa. Future rainfall is examined using an ensemble of six downscaled climate model simulations at a spatial resolution of 14 km for 1971–2100, applying the IPCC SRES-A2 ‘Business as Usual’ emissions scenario, and the six original global climate models (GCMs. Analyses of the observed seasonal rainfall data highlight cyclical variability and long-term declines. The observed periodicities are of about 2–4, 5, 8, 11, and 40–50 years. Furthermore, dry season rainfall is significantly correlated with the El Niño Southern Oscillation (ENSO, while wet season rainfall is weakly correlated with ENSO. The simulated rainfall data reproduce the observed seasonal cycle very well, but overestimate the magnitude of rainfall and underestimate inter-annual rainfall variability. The models also show that the observed rainfall periodicities will continue throughout the 21st century. The models project that rainfall will decline, although with wide ranges of uncertainty, depending on season and location. Crop water demand estimates show that the projected changes will potentially impact the first growing period for rice during November–March. Rainfall may also be insufficient to meet water demand for many crops in the second growing period of March–June, when high value commodities such as chillies and tobacco are produced. The results reinforce the importance to consider all uncertainties when utilizing climate

  13. Analysis of the temporal structure of the daily rainfall observed at ...

    African Journals Online (AJOL)

    West African rainfall is characterized by a strong variability. In order to quantify the hydrological impacts of such variability, analysis of rainfall patterns is highly essential. This study aims to characterize the Sudanese rainfall, using a raingauge data set collected on the upper Oueme River catchment (Benin) between 1999 ...

  14. Spatial Variability of Rainfall

    DEFF Research Database (Denmark)

    Jensen, N.E.; Pedersen, Lisbeth

    2005-01-01

    As a part of a Local Area Weather Radar (LAWR) calibration exercise 15 km south of Århus, Denmark, the variability in accumulated rainfall within a single radar pixel (500 by 500 m) was measured using nine high-resolution rain gauges. The measured values indicate up to a 100% variation between...

  15. 100 years of Belgian rainfall: are there trends?

    Science.gov (United States)

    Vaes, G; Willems, P; Berlamont, J

    2002-01-01

    In 1999 the digitisation of old rainfall records of measurements at Uccle (Belgium) was completed, which resulted in a unique rainfall series of 100 years (period 1898-1997). This is an ideal opportunity to search for trends in the rainfall over the last century. Large variations in rainfall probability over the century have been observed. For small aggregation levels there is a small decrease in extreme rainfall events over the century. For large aggregation levels there is a more explicit increase in extreme rainfall. Because the rainfall on seasonal aggregation level is only slightly increased, the increase in extreme rainfall events for aggregation levels between a few days and a few months can only occur due to larger clustering. However, the final conclusion is that no significant trend can be observed. A pure random variation of the rainfall can cause equally large variations. This does not exclude a possible trend in flooding frequency, due to the strong increase in urbanisation over the last century.

  16. Rainfall Distributions in Sri Lanka in Time and Space: An Analysis Based on Daily Rainfall Data

    Directory of Open Access Journals (Sweden)

    T. P. Burt

    2014-09-01

    Full Text Available Daily rainfall totals are analyzed for the main agro-climatic zones of Sri Lanka for the period 1976–2006. The emphasis is on daily rainfall rather than on longer-period totals, in particular the number of daily falls exceeding given threshold totals. For one station (Mapalana, where a complete daily series is available from 1950, a longer-term perspective on changes over half a century is provided. The focus here is particularly on rainfall in March and April, given the sensitivity of agricultural decisions to early southwest monsoon rainfall at the beginning of the Yala cultivation season but other seasons are also considered, in particular the northeast monsoon. Rainfall across Sri Lanka over three decades is investigated in relation to the main atmospheric drivers known to affect climate in the region: sea surface temperatures in the Pacific and Indian Oceans, of which the former are shown to be more important. The strong influence of El Niño and La Niña phases on various aspects of the daily rainfall distribution in Sri Lanka is confirmed: positive correlations with Pacific sea-surface temperatures during the north east monsoon and negative correlations at other times. It is emphasized in the discussion that Sri Lanka must be placed in its regional context and it is important to draw on regional-scale research across the Indian subcontinent and the Bay of Bengal.

  17. Understanding the relationship between rainfall and river discharge: trends in an Amazonian watershed

    Science.gov (United States)

    Nóbrega, Rodolfo; Guzha, Alphonce; Freire, Paula; Santos, Celso; Gerold, Gerhard

    2013-04-01

    A research challenge in the Amazon rainforest is to understand different environmental patterns in a five million km2 region which with poor and/or unavailable environmental data. Deforestation and degradation in this forest have motivated intense monitoring activities in order to understand its impact and support the formulation of sustainable environmental policies. Time series analysis of hydrologic data is often use as a tool to evaluate watershed responses to climatic and anthropogenic influences. In this study, trend analysis of stream discharge from a 35600 km² watershed (Curuá River), located in southern Amazon was performed using 31 years discharge and rainfall data (1976-2006). The Curuá River is a tributary of Xingu River, site of the controversial Belo Monte dam. The aim of this work was to investigate the temporal variability of discharge, in relation to associated rainfall variability in order to contribute to a better understanding of the hydrological status of the watershed. The Mann Kendall non parametric tests were performed on daily, seasonal and annual discharge data. Frequency analysis using wavelet transform was also done, and annual and seasonal rainfall data was analyzed and correlated to discharge. Results from this study indicate decreasing trends in discharge (intra- and inter-annual) but while there is no evidence of a decreasing trend in in rainfall. Further interpretation of the data for possible causes of discharge changes is needed at the local study level, and implications of these results discussed in the context of climate change, deforestation and water resource management (including dam's constructions last decades). Results from this study do not confirm findings from other regional scale trend analyses, and therefore is it important to quantify the spatial extension of these decreasing stream flow trends in the Amazonia.

  18. Climate and the inter-annual variability of fire in southern Africa: a meta-analysis using long-term field data and satellite-derived burnt area data

    CSIR Research Space (South Africa)

    Archibald, S

    2010-11-01

    Full Text Available -sensed burned area data to test whether it is possible to develop a general model. Location: Africa south of the equator Methods: Linear mixed e ects models were used to determine the e ect of rainfall, season- ality, and re weather in driving variation... in re extent between years, and to test whether the e ect of these variables changes across the sub-continent, and in areas more and less impacted by human activities. Results: A simple model including rainfall and seasonality explained 40...

  19. Principal components of monsoon rainfall

    OpenAIRE

    BEDI, H. S.; BINDRA, M. M. S.

    2011-01-01

    Monsoon rainfall over India during the 120-day period from the beginning of June to the end of September exhibits interesting oscillations over the country. According to an analysis by Sub-bramayya (1968), there is a negative correlation in rainfall between the north-eastern and west-central parts of India. But his analysis does not indicate how much of the total variance of rainfall is explained by different rainfall patterns. We examined this aspect by expressing rainfall as a linear combin...

  20. ANALYSIS OF THE STATISTICAL BEHAVIOUR OF DAILY MAXIMUM AND MONTHLY AVERAGE RAINFALL ALONG WITH RAINY DAYS VARIATION IN SYLHET, BANGLADESH

    Directory of Open Access Journals (Sweden)

    G. M. J. HASAN

    2014-10-01

    Full Text Available Climate, one of the major controlling factors for well-being of the inhabitants in the world, has been changing in accordance with the natural forcing and manmade activities. Bangladesh, the most densely populated countries in the world is under threat due to climate change caused by excessive use or abuse of ecology and natural resources. This study checks the rainfall patterns and their associated changes in the north-eastern part of Bangladesh mainly Sylhet city through statistical analysis of daily rainfall data during the period of 1957 - 2006. It has been observed that a good correlation exists between the monthly mean and daily maximum rainfall. A linear regression analysis of the data is found to be significant for all the months. Some key statistical parameters like the mean values of Coefficient of Variability (CV, Relative Variability (RV and Percentage Inter-annual Variability (PIV have been studied and found to be at variance. Monthly, yearly and seasonal variation of rainy days also analysed to check for any significant changes.

  1. Tree ring reconstructed rainfall over the southern Amazon Basin

    Science.gov (United States)

    Lopez, Lidio; Stahle, David; Villalba, Ricardo; Torbenson, Max; Feng, Song; Cook, Edward

    2017-07-01

    Moisture sensitive tree ring chronologies of Centrolobium microchaete have been developed from seasonally dry forests in the southern Amazon Basin and used to reconstruct wet season rainfall totals from 1799 to 2012, adding over 150 years of rainfall estimates to the short instrumental record for the region. The reconstruction is correlated with the same atmospheric variables that influence the instrumental measurements of wet season rainfall. Anticyclonic circulation over midlatitude South America promotes equatorward surges of cold and relatively dry extratropical air that converge with warm moist air to form deep convection and heavy rainfall over this sector of the southern Amazon Basin. Interesting droughts and pluvials are reconstructed during the preinstrumental nineteenth and early twentieth centuries, but the tree ring reconstruction suggests that the strong multidecadal variability in instrumental and reconstructed wet season rainfall after 1950 may have been unmatched since 1799.

  2. Interannual variability of rainfall characteristics over southwestern Madagascar

    Science.gov (United States)

    Randriamahefasoa, T. S. M.; Reason, C. J. C.

    2017-04-01

    The interannual variability of daily frequency of rainfall [>1 mm/day] and heavy rainfall [>30 mm/day] is studied for the southwestern region of Madagascar, which is relatively arid compared to the rest of the island. Attention is focused on the summer rainy season from December to March at four stations (Morondava, Ranohira, Toliara and Taolagnaro), whose daily rainfall data covering the period 1970-2000 were obtained from the Madagascar Meteorological Service. El Niño Southern Oscillation (ENSO) was found to have a relatively strong correlation with wet day frequency at each station and, particularly, for Toliara in the extreme southwest. In terms of seasonal rainfall totals, most El Niño (La Niña) summers receive below (above) average amounts. An ENSO connection with heavy rainfall events was less clear. However, for heavy rainfall events, the associated atmospheric circulation displays a Southern Annular Mode-like pattern throughout the hemisphere. For ENSO years and the neutral seasons 1979/80, 1981/82 which had large anomalies in wet day frequency, regional atmospheric circulation patterns consisted of strong anomalies in low-level moisture convergence and uplift over and near southwestern Madagascar that made conditions correspondingly more or less favourable for rainfall. Dry (wet) summers in southern Madagascar were also associated with an equatorward (poleward) displacement of the ITCZ in the region.

  3. Rainfall erosivity map for Ghana

    International Nuclear Information System (INIS)

    Oduro Afriyie, K.

    1995-10-01

    Monthly rainfall data, spanning over a period of more than thirty years, were used to compute rainfall erosivity indices for various stations in Ghana, using the Fournier index, c, defined as p 2 /P, where p is the rainfall amount in the wettest month and P is the annual rainfall amount. Values of the rainfall erosivity indices ranged from 24.5 mm at Sunyani in the mid-portion of Ghana to 180.9 mm at Axim in the south western coastal portion. The indices were used to construct a rainfall erosivity map for the country. The map revealed that Ghana may be broadly divided into five major erosion risk zones. The middle sector of Ghana is generally in the low erosion risk zone; the northern sector is in the moderate to severe erosion risk zone, while the coastal sector is in the severe to extreme severe erosion risk zone. (author). 11 refs, 1 fig., 1 tab

  4. Flood risk reduction and flow buffering as ecosystem services - Part 2: Land use and rainfall intensity effects in Southeast Asia

    Science.gov (United States)

    van Noordwijk, Meine; Tanika, Lisa; Lusiana, Betha

    2017-05-01

    case studies may not hold, even within the same climatic zone. A wet-season Fp value above 0.7 was achievable in forest-agroforestry mosaic case studies. Inter-annual variability in Fp is large relative to effects of land cover change. Multiple (5-10) years of paired-plot data would generally be needed to reject no-change null hypotheses on the effects of land use change (degradation and restoration). Fp trends over time serve as a holistic scale-dependent performance indicator of degrading/recovering watershed health and can be tested for acceptability and acceptance in a wider social-ecological context.

  5. An Atlantic influence on Amazon rainfall

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Jin-Ho [University of Maryland, Department of Atmospheric and Oceanic Science, College Park, MD (United States); Zeng, Ning [University of Maryland, Earth System Science Interdisciplinary Center, College Park, MD (United States); University of Maryland, Department of Atmospheric and Oceanic Science, College Park, MD (United States)

    2010-02-15

    Rainfall variability over the Amazon basin has often been linked to variations in Pacific sea surface temperature (SST), and in particular, to the El Nino/Southern Oscillation (ENSO). However, only a fraction of Amazon rainfall variability can be explained by ENSO. Building upon the recent work of Zeng (Environ Res Lett 3:014002, 2008), here we provide further evidence for an influence on Amazon rainfall from the tropical Atlantic Ocean. The strength of the North Atlantic influence is found to be comparable to the better-known Pacific ENSO connection. The tropical South Atlantic Ocean also shows some influence during the wet-to-dry season transition period. The Atlantic influence is through changes in the north-south divergent circulation and the movement of the ITCZ following warm SST. Therefore, it is strongest in the southern part of the Amazon basin during the Amazon's dry season (July-October). In contrast, the ENSO related teleconnection is through anomalous east-west Walker circulation with largely concentrated in the eastern (lower) Amazon. This ENSO connection is seasonally locked to boreal winter. A complication due to the influence of ENSO on Atlantic SST causes an apparent North Atlantic SST lag of Amazon rainfall. Removing ENSO from North Atlantic SST via linear regression resolves this causality problem in that the residual Atlantic variability correlates well and is in phase with the Amazon rainfall. A strong Atlantic influence during boreal summer and autumn is particularly significant in terms of the impact on the hydro-ecosystem which is most vulnerable during the dry season, as highlighted by the severe 2005 Amazon drought. Such findings have implications for both seasonal-interannual climate prediction and understanding the longer-term changes of the Amazon rainforest. (orig.)

  6. Rainfall statistics changes in Sicily

    Directory of Open Access Journals (Sweden)

    E. Arnone

    2013-07-01

    Full Text Available Changes in rainfall characteristics are one of the most relevant signs of current climate alterations. Many studies have demonstrated an increase in rainfall intensity and a reduction of frequency in several areas of the world, including Mediterranean areas. Rainfall characteristics may be crucial for vegetation patterns formation and evolution in Mediterranean ecosystems, with important implications, for example, in vegetation water stress or coexistence and competition dynamics. At the same time, characteristics of extreme rainfall events are fundamental for the estimation of flood peaks and quantiles that can be used in many hydrological applications, such as design of the most common hydraulic structures, or planning and management of flood-prone areas. In the past, Sicily has been screened for several signals of possible climate change. Annual, seasonal and monthly rainfall data in the entire Sicilian region have been analyzed, showing a global reduction of total annual rainfall. Moreover, annual maximum rainfall series for different durations have been rarely analyzed in order to detect the presence of trends. Results indicated that for short durations, historical series generally exhibit increasing trends, while for longer durations the trends are mainly negative. Starting from these premises, the aim of this study is to investigate and quantify changes in rainfall statistics in Sicily, during the second half of the last century. Time series of about 60 stations over the region have been processed and screened by using the nonparametric Mann–Kendall test. In particular, extreme events have been analyzed using annual maximum rainfall series at 1, 3, 6, 12 and 24 h duration, while daily rainfall properties have been analyzed in terms of frequency and intensity, also characterizing seasonal rainfall features. Results of extreme events analysis confirmed an increasing trend for rainfall of short durations, especially for 1 h rainfall

  7. Rainfall Erosivity in Europe

    DEFF Research Database (Denmark)

    Panagos, Panos; Ballabio, Cristiano; Borrelli, Pasquale

    2015-01-01

    on the best available datasets. Data have been collected from 1541 precipitation stations in all European Union (EU) Member States and Switzerland, with temporal resolutions of 5 to 60 min. The R-factor values calculated from precipitation data of different temporal resolutions were normalised to R......-factor values with temporal resolutions of 30 min using linear regression functions. Precipitation time series ranged from a minimum of 5 years to a maximum of 40 years. The average time series per precipitation station is around 17.1 years, the most datasets including the first decade of the 21st century....... Gaussian Process Regression (GPR) has been used to interpolate the R-factor station values to a European rainfall erosivity map at 1 km resolution. The covariates used for the R-factor interpolation were climatic data (total precipitation, seasonal precipitation, precipitation of driest/wettest months...

  8. Observed magnified runoff response to rainfall intensification under global warming

    International Nuclear Information System (INIS)

    Huang, Jr-Chuan; Lee, Tsung-Yu; Lee, Jun-Yi

    2014-01-01

    Runoff response to rainfall intensification under global warming is crucial, but is poorly discussed due to the limited data length and human alteration. Historical rainfall and runoff records in pristine catchments in Taiwan were investigated through trend analysis and cross temperature difference analysis. Trend analysis showed that both rainfall and runoff in the 99.9-percentile have been significantly increasing in terms of frequency and intensity over the past four decades. Cross temperature difference analysis quantified that the rainfall and runoff extremes (including the 99.0–99.9-percentiles) may increase by 69.5% and 99.8%, respectively, under a future scenario of 1  ° C increase in temperature. This increase in intensity resembles the increase in intensity observed between 1971–1990 and 1991–2010. The amplified runoff response can be related to the limited catchment storage capacity being preoccupied by rainfall extremes. The quantified temperature effect on rainfall and runoff intensification can be a strong basis for designing scenarios, confirming and fusing GCMs’ results. In addition, the runoff amplification should be a warning for other regions with significant rainfall intensification. Appropriate strategies are indispensable and urgently needed to maintain and protect the development of societies. (paper)

  9. Wheat yield vulnerability: relation to rainfall and suggestions for adaptation

    Directory of Open Access Journals (Sweden)

    Khalid Tafoughalti

    2018-04-01

    Full Text Available Wheat production is of paramount importance in the region of Meknes, which is mainly produced under rainfed conditions. It is the dominant cereal, the greater proportion being the soft type. During the past few decades, rainfall flaws have caused a number of cases of droughts. These flaws have seriously affecting wheat production. The main objective of this study is the assessment of rainfall variability at monthly, seasonal and annual scales and to determine their impact on wheat yields. To reduce this impact we suggested some mechanisms of adaptation. We used monthly rainfall records for three decades and wheat yields records of fifteen years. Rainfall variability is assessed utilizing the precipitation concentration index and the variation coefficient. The association between wheat yields and cumulative rainfall amounts of different scales was calculated based on a regression model to evaluate the impact of rainfall on wheat yields. Data analysis shown moderate seasonal and irregular annual rainfall distribution. Yields fluctuated from 210 to 4500 Kg/ha with 52% of coefficient of variation. The correlation results shows that soft wheat and hard wheat are strongly correlated with the period of January to March than with the whole growing-season. While they are adversely correlated with the mid-spring. This investigation concluded that synchronizing appropriate adaptation with the period of January to March was crucial to achieving success yield of wheat.

  10. Probabilistic rainfall thresholds for landslide occurrence using a Bayesian approach

    Science.gov (United States)

    Berti, M.; Martina, M.; Franceschini, S.; Pignone, S.; Simoni, A.; Pizziolo, M.

    2012-04-01

    resulted in landslides must be considered in the analysis. The result is a value of landslide probability (from 0 to 1) for each combination of the selected rainfall variables. The method has been applied to the historical dataset of the Emilia-Romagna Region (Italy). The dataset contains more than 9000 landslide records, for 4141 of which the date of occurrence is reported with a daily accuracy. Among these, 2741 landslides are characterized by a well-defined triggering rainfall (objectively identifiable in terms of duration and intensity) suitable for the analysis. Rainfall that non resulted in landslides account for more than 250000 events. The results clearly show that landslide triggering in the study area is strongly related to rainfall event parameters (duration, intensity, total rainfall) while antecedent rainfall seem to be less important. Moreover, the lines of equal Bayes probability in the rainfall duration- intensity chart are roughly parallel to the regional threshold proposed by Guzzetti et al. (2007), which in our case indicates a landslide probability of about 0.1. The abrupt increase of landslide probability in the duration-intensity plane indicates a radical change of state of the system, proving the existence of a real physical threshold.

  11. Radar rainfall image repair techniques

    Directory of Open Access Journals (Sweden)

    Stephen M. Wesson

    2004-01-01

    Full Text Available There are various quality problems associated with radar rainfall data viewed in images that include ground clutter, beam blocking and anomalous propagation, to name a few. To obtain the best rainfall estimate possible, techniques for removing ground clutter (non-meteorological echoes that influence radar data quality on 2-D radar rainfall image data sets are presented here. These techniques concentrate on repairing the images in both a computationally fast and accurate manner, and are nearest neighbour techniques of two sub-types: Individual Target and Border Tracing. The contaminated data is estimated through Kriging, considered the optimal technique for the spatial interpolation of Gaussian data, where the 'screening effect' that occurs with the Kriging weighting distribution around target points is exploited to ensure computational efficiency. Matrix rank reduction techniques in combination with Singular Value Decomposition (SVD are also suggested for finding an efficient solution to the Kriging Equations which can cope with near singular systems. Rainfall estimation at ground level from radar rainfall volume scan data is of interest and importance in earth bound applications such as hydrology and agriculture. As an extension of the above, Ordinary Kriging is applied to three-dimensional radar rainfall data to estimate rainfall rate at ground level. Keywords: ground clutter, data infilling, Ordinary Kriging, nearest neighbours, Singular Value Decomposition, border tracing, computation time, ground level rainfall estimation

  12. Spatial dependence of extreme rainfall

    Science.gov (United States)

    Radi, Noor Fadhilah Ahmad; Zakaria, Roslinazairimah; Satari, Siti Zanariah; Azman, Muhammad Az-zuhri

    2017-05-01

    This study aims to model the spatial extreme daily rainfall process using the max-stable model. The max-stable model is used to capture the dependence structure of spatial properties of extreme rainfall. Three models from max-stable are considered namely Smith, Schlather and Brown-Resnick models. The methods are applied on 12 selected rainfall stations in Kelantan, Malaysia. Most of the extreme rainfall data occur during wet season from October to December of 1971 to 2012. This period is chosen to assure the available data is enough to satisfy the assumption of stationarity. The dependence parameters including the range and smoothness, are estimated using composite likelihood approach. Then, the bootstrap approach is applied to generate synthetic extreme rainfall data for all models using the estimated dependence parameters. The goodness of fit between the observed extreme rainfall and the synthetic data is assessed using the composite likelihood information criterion (CLIC). Results show that Schlather model is the best followed by Brown-Resnick and Smith models based on the smallest CLIC's value. Thus, the max-stable model is suitable to be used to model extreme rainfall in Kelantan. The study on spatial dependence in extreme rainfall modelling is important to reduce the uncertainties of the point estimates for the tail index. If the spatial dependency is estimated individually, the uncertainties will be large. Furthermore, in the case of joint return level is of interest, taking into accounts the spatial dependence properties will improve the estimation process.

  13. Seasonal predictability of Kiremt rainfall in coupled general circulation models

    Science.gov (United States)

    Gleixner, Stephanie; Keenlyside, Noel S.; Demissie, Teferi D.; Counillon, François; Wang, Yiguo; Viste, Ellen

    2017-11-01

    The Ethiopian economy and population is strongly dependent on rainfall. Operational seasonal predictions for the main rainy season (Kiremt, June-September) are based on statistical approaches with Pacific sea surface temperatures (SST) as the main predictor. Here we analyse dynamical predictions from 11 coupled general circulation models for the Kiremt seasons from 1985-2005 with the forecasts starting from the beginning of May. We find skillful predictions from three of the 11 models, but no model beats a simple linear prediction model based on the predicted Niño3.4 indices. The skill of the individual models for dynamically predicting Kiremt rainfall depends on the strength of the teleconnection between Kiremt rainfall and concurrent Pacific SST in the models. Models that do not simulate this teleconnection fail to capture the observed relationship between Kiremt rainfall and the large-scale Walker circulation.

  14. Sahel rainfall variability and response to greenhouse warming

    Science.gov (United States)

    Haarsma, Reindert J.; Selten, Frank M.; Weber, Suzanne L.; Kliphuis, Michael

    2005-09-01

    The NCEP/NCAR re-analyses as well as ensemble integrations with an atmospheric GCM indicate that interannual variations in Sahel rainfall are related to variations in the mean sea level pressure (MSLP) over the Sahara. In turn the MSLP variations are related to the global distribution of surface air temperature (SAT). An increase in SAT over the Sahara, relative to the surrounding oceans, decreases the MSLP over the Sahara, thereby increasing the Sahel rainfall. We hypothesize that through this mechanism greenhouse warming will cause an increase in Sahel rainfall, because the warming is expected to be more prominent over the summer continents than over the oceans. This has been confirmed using an ensemble of 62 coupled model runs forced with a business as usual scenario. The ensemble mean increase in Sahel rainfall between 1980 and 2080 is about 1-2 mm day-1 (25-50%) during July-September, thereby strongly reducing the probability of prolonged droughts.

  15. On the relationship between large-scale climate modes and regional synoptic patterns that drive Victorian rainfall

    Directory of Open Access Journals (Sweden)

    D. C. Verdon-Kidd

    2009-04-01

    Full Text Available In this paper regional (synoptic and large-scale climate drivers of rainfall are investigated for Victoria, Australia. A non-linear classification methodology known as self-organizing maps (SOM is used to identify 20 key regional synoptic patterns, which are shown to capture a range of significant synoptic features known to influence the climate of the region. Rainfall distributions are assigned to each of the 20 patterns for nine rainfall stations located across Victoria, resulting in a clear distinction between wet and dry synoptic types at each station. The influence of large-scale climate modes on the frequency and timing of the regional synoptic patterns is also investigated. This analysis revealed that phase changes in the El Niño Southern Oscillation (ENSO, the Indian Ocean Dipole (IOD and/or the Southern Annular Mode (SAM are associated with a shift in the relative frequency of wet and dry synoptic types on an annual to inter-annual timescale. In addition, the relative frequency of synoptic types is shown to vary on a multi-decadal timescale, associated with changes in the Inter-decadal Pacific Oscillation (IPO. Importantly, these results highlight the potential to utilise the link between the regional synoptic patterns derived in this study and large-scale climate modes to improve rainfall forecasting for Victoria, both in the short- (i.e. seasonal and long-term (i.e. decadal/multi-decadal scale. In addition, the regional and large-scale climate drivers identified in this study provide a benchmark by which the performance of Global Climate Models (GCMs may be assessed.

  16. Fluvial signatures of modern and paleo orographic rainfall gradients

    Science.gov (United States)

    Schildgen, Taylor; Strecker, Manfred

    2016-04-01

    The morphology of river profiles is intimately linked to both climate and tectonic forcing. While much interest recently has focused on how river profiles can be inverted to derive uplift histories, here we show how in regions of strong orographic rainfall gradients, rivers may primarily record spatial patterns of precipitation. As a case study, we examine the eastern margin of the Andean plateau in NW Argentina, where the outward (eastward) growth of a broken foreland has led to a eastward shift in the main orographic rainfall gradient over the last several million years. Rivers influenced by the modern rainfall gradient are characterized by normalized river steepness values in tributary valleys that closely track spatial variations in rainfall, with higher steepness values in drier areas and lower steepness values in wetter areas. The same river steepness pattern has been predicted in landscape evolution models that apply a spatial gradient in rainfall to a region of uniform erosivity and uplift rate (e.g., Han et al., 2015). Also, chi plots from river networks on individual ranges affected by the modern orographic rainfall reveal patterns consistent with assymmetric precipitation across the range: the largest channels on the windward slopes are characterized by capture, while the longest channels on the leeward slopes are dominated by beheadings. Because basins on the windward side both lengthen and widen, tributary channels in the lengthening basins are characterized by capture, while tributary channels from neighboring basins on the windward side are dominated by beheadings. These patterns from the rivers influenced by the modern orographic rainfall gradient provide a guide for identifying river morphometric signatures of paleo orographic rainfall gradients. Mountain ranges to the west of the modern orographic rainfall have been interpreted to mark the location of orographic rainfall in the past, but these ranges are now in spatially near-uniform semi-arid to

  17. NEXRAD Rainfall Data: Eureka, California

    Data.gov (United States)

    National Aeronautics and Space Administration — Next-Generation Radar (NEXRAD) Weather Surveillance Radar 1988 (WSR-88D) measurements were used to support AMSR-E rainfall validation efforts in Eureka, California,...

  18. Predicting extreme rainfall over eastern Asia by using complex networks

    International Nuclear Information System (INIS)

    He Su-Hong; Gong Yan-Chun; Huang Yan-Hua; Wu Cheng-Guo; Feng Tai-Chen; Gong Zhi-Qiang

    2014-01-01

    A climate network of extreme rainfall over eastern Asia is constructed for the period of 1971–2000, employing the tools of complex networks and a measure of nonlinear correlation called event synchronization (ES). Using this network, we predict the extreme rainfall for several cases without delay and with n-day delay (1 ≤ n ≤ 10). The prediction accuracy can reach 58% without delay, 21% with 1-day delay, and 12% with n-day delay (2 ≤ n ≤ 10). The results reveal that the prediction accuracy is low in years of a weak east Asia summer monsoon (EASM) or 1 year later and high in years of a strong EASM or 1 year later. Furthermore, the prediction accuracy is higher due to the many more links that represent correlations between different grid points and a higher extreme rainfall rate during strong EASM years. (geophysics, astronomy, and astrophysics)

  19. Should seasonal rainfall forecasts be used for flood preparedness?

    Directory of Open Access Journals (Sweden)

    E. Coughlan de Perez

    2017-09-01

    Full Text Available In light of strong encouragement for disaster managers to use climate services for flood preparation, we question whether seasonal rainfall forecasts should indeed be used as indicators of the likelihood of flooding. Here, we investigate the primary indicators of flooding at the seasonal timescale across sub-Saharan Africa. Given the sparsity of hydrological observations, we input bias-corrected reanalysis rainfall into the Global Flood Awareness System to identify seasonal indicators of floodiness. Results demonstrate that in some regions of western, central, and eastern Africa with typically wet climates, even a perfect tercile forecast of seasonal total rainfall would provide little to no indication of the seasonal likelihood of flooding. The number of extreme events within a season shows the highest correlations with floodiness consistently across regions. Otherwise, results vary across climate regimes: floodiness in arid regions in southern and eastern Africa shows the strongest correlations with seasonal average soil moisture and seasonal total rainfall. Floodiness in wetter climates of western and central Africa and Madagascar shows the strongest relationship with measures of the intensity of seasonal rainfall. Measures of rainfall patterns, such as the length of dry spells, are least related to seasonal floodiness across the continent. Ultimately, identifying the drivers of seasonal flooding can be used to improve forecast information for flood preparedness and to avoid misleading decision-makers.

  20. Bayesian spatiotemporal interpolation of rainfall in the Central Chilean Andes

    Science.gov (United States)

    Ossa-Moreno, Juan; Keir, Greg; McIntyre, Neil

    2016-04-01

    Water availability in the populous and economically significant Central Chilean region is governed by complex interactions between precipitation, temperature, snow and glacier melt, and streamflow. Streamflow prediction at daily time scales depends strongly on accurate estimations of precipitation in this predominantly dry region, particularly during the winter period. This can be difficult as gauged rainfall records are scarce, especially in the higher elevation regions of the Chilean Andes, and topographic influences on rainfall are not well understood. Remotely sensed precipitation and topographic products can be used to construct spatiotemporal multivariate regression models to estimate rainfall at ungauged locations. However, classical estimation methods such as kriging cannot easily accommodate the complicated statistical features of the data, including many 'no rainfall' observations, as well as non-normality, non-stationarity, and temporal autocorrelation. We use a separable space-time model to predict rainfall using the R-INLA package for computationally efficient Bayesian inference, using the gridded CHIRPS satellite-based rainfall dataset and digital elevation models as covariates. We jointly model both the probability of rainfall occurrence on a given day (using a binomial likelihood) as well as amount (using a gamma likelihood or similar). Correlation in space and time is modelled using a Gaussian Markov Random Field (GMRF) with a Matérn spatial covariance function which can evolve over time according to an autoregressive model if desired. It is possible to evaluate the GMRF at relatively coarse temporal resolution to speed up computations, but still produce daily rainfall predictions. We describe the process of model selection and inference using an information criterion approach, which we use to objectively select from competing models with various combinations of temporal smoothing, likelihoods, and autoregressive model orders.

  1. Using naive Bayes classifier for classification of convective rainfall ...

    Indian Academy of Sciences (India)

    ... based on 'naiveBayes classifier' is applied. This is a simple probabilistic classifier based on applying 'Bayes' theoremwith strong (naive) independent assumptions. For a 9-month period, the ability of SEVIRI to classifythe rainfall intensity in the convective clouds is evaluated using weather radar over the northern Algeria.

  2. Should seasonal rainfall forecasts be used for flood preparedness?

    NARCIS (Netherlands)

    Coughlan, E.R.; Stephens, E.; Bischiniotis, K.; van Aalst, M.; van den Hurk, B.J.J.M.; Mason, S.; Nissan, H.; Pappenberger, F.

    2017-01-01

    In light of strong encouragement for disaster managers to use climate services for flood preparation, we question whether seasonal rainfall forecasts should indeed be used as indicators of the likelihood of flooding. Here, we investigate the primary indicators of flooding at the seasonal timescale

  3. Rainfall erosivity in Central Chile

    Science.gov (United States)

    Bonilla, Carlos A.; Vidal, Karim L.

    2011-11-01

    SummaryOne of the most widely used indicators of potential water erosion risk is the rainfall-runoff erosivity factor ( R) of the Revised Universal Soil Loss Equation (RUSLE). R is traditionally determined by calculating a long-term average of the annual sum of the product of a storm's kinetic energy ( E) and its maximum 30-min intensity ( I30), known as the EI30. The original method used to calculate EI30 requires pluviograph records for at most 30-min time intervals. Such high resolution data is difficult to obtain in many parts of the world, and processing it is laborious and time-consuming. In Chile, even though there is a well-distributed rain gauge network, there is no systematic characterization of the territory in terms of rainfall erosivity. This study presents a rainfall erosivity map for most of the cultivated land in the country. R values were calculated by the prescribed method for 16 stations with continuous graphical record rain gauges in Central Chile. The stations were distributed along 800 km (north-south), and spanned a precipitation gradient of 140-2200 mm yr -1. More than 270 years of data were used, and 5400 storms were analyzed. Additionally, 241 spatially distributed R values were generated by using an empirical procedure based on annual rainfall. Point estimates generated by both methods were interpolated by using kriging to create a map of rainfall erosivity for Central Chile. The results show that the empirical procedure used in this study predicted the annual rainfall erosivity well (model efficiency = 0.88). Also, an increment in the rainfall erosivities was found as a result of the rainfall depths, a regional feature determined by elevation and increasing with latitude from north to south. R values in the study area range from 90 MJ mm ha -1 h -1 yr -1 in the north up to 7375 MJ mm ha -1 h -1 yr -1 in the southern area, at the foothills of the Andes Mountains. Although the map and the estimates could be improved in the future by

  4. Rainfall-Runoff Parameters Uncertainity

    Science.gov (United States)

    Heidari, A.; Saghafian, B.; Maknoon, R.

    2003-04-01

    Karkheh river basin, located in southwest of Iran, drains an area of over 40000 km2 and is considered a flood active basin. A flood forecasting system is under development for the basin, which consists of a rainfall-runoff model, a river routing model, a reservior simulation model, and a real time data gathering and processing module. SCS, Clark synthetic unit hydrograph, and Modclark methods are the main subbasin rainfall-runoff transformation options included in the rainfall-runoff model. Infiltration schemes, such as exponentioal and SCS-CN methods, account for infiltration losses. Simulation of snow melt is based on degree day approach. River flood routing is performed by FLDWAV model based on one-dimensional full dynamic equation. Calibration and validation of the rainfall-runoff model on Karkheh subbasins are ongoing while the river routing model awaits cross section surveys.Real time hydrometeological data are collected by a telemetry network. The telemetry network is equipped with automatic sensors and INMARSAT-C comunication system. A geographic information system (GIS) stores and manages the spatial data while a database holds the hydroclimatological historical and updated time series. Rainfall runoff parameters uncertainty is analyzed by Monte Carlo and GLUE approaches.

  5. Multi-decadal classification of synoptic weather types, observed trends and links to rainfall characteristics over Saudi Arabia

    KAUST Repository

    El Kenawy, Ahmed M.

    2014-09-15

    An automated version of the Lamb weather type classification scheme was employed to characterize daily circulation conditions in Saudi Arabia from 1960 to 2005. Daily gridded fields of sea level pressure (SLP) from both the NCEP/NCAR and the European Center for Medium-Range Weather Forecast (ECMWF) reanalysis data (ERA40) were used as input data for this classification. The output catalog included 10 basic types, which describe the direction and vorticity of airflow in the region (i.e., cyclonic, anti-cyclonic, and directional). In general, our findings indicate that cyclonic (C) days represent the most frequent type among all days, with 69.2% of the annual count of days from 1960 to 2005, followed by SE directional flows (21%). It was also determined that airflows originating from the Indian Ocean (i.e., S, SE, and E) are more frequent than those from the Mediterranean and Red Seas (i.e., W, NW, and SW). The defined weather types were assessed for the presence of inter-annual and intra-annual trends using the Mann–Kendall tau statistic. The trend analysis suggests statistically significant changes in the frequencies of a majority of the weather types from 1960 to 2005. The relationship between the daily occurrence of rainfall and the frequency of individual weather types was also described using daily rainfall data from a network of 87 weather observatories. Results demonstrate that increasing frequencies of weather types connected to easterly inflows support higher precipitation amounts over the study domain. Characterizing the association between atmospheric circulation patterns and rainfall in Saudi Arabia is important for understanding potential impacts related to climate variability and also for developing circulation-based downscaling methods.

  6. Carbon-cycle implications of asymmetry in response of semi-arid ecosystem phenology and productivity to rainfall

    Science.gov (United States)

    Smith, Benjamin; Haverd, Vanessa; Ahlström, Anders; Canadell, Josep

    2017-04-01

    Semi-arid savannahs and shrublands of the tropics and subtropics play a key role in the inter-annual variability of the global carbon cycle and are emerging as an important player - comparable with tropical forests - in terms of their contribution to the ongoing sink trend of the carbon exchange between the global land surface and atmosphere. Both the variability and carbon balance trend of the savannah-shrubland biome are characterised by shifting phenology, mediated by changes in the seasonality and relative contributions to ecosystem productivity of woody vegetation elements and grasses. Shifts in water availability associated with the impacts of global circulation systems on the distribution and amount of rainfall are a key driver of vegetation response in these ecosystems, which tolerate drought, but spring to life, becoming highly productive, during episodes of ample water supply. This "boom or bust" behaviour with respect to water availability may be expected to translate into an asymmetric response to rainfall change, positive anomalies in rainfall tending to lead to larger increases in productivity compared with the corresponding decrease in productivity resulting from a negative anomaly of comparable size. As rainfall distributions over time themselves exhibit asymmetry, an 'intrinsic' (ecosystem response-driven) and 'extrinsic' (climate or weather forcing-driven) component of asymmetry may be distinguished. We investigated the prevalence of asymmetry in forcing and response of ecosystem productivity to rainfall variability globally and for the illustrative case of Australia, which emerges as a global 'hot spot' for rainfall-driven variability in ecosystem gross primary production (GPP) and associated net ecosystem productivity (NEP). Employing two climate-driven ecosystem models, informed by multiple observation types (land-atmosphere fluxes, biomass, streamflow and remotely-sensed vegetation cover), we show that the inland region of Australia, dominated

  7. Chapman Conference on Rainfall Fields

    Science.gov (United States)

    Gupta, V. K.

    The Chapman Conference on Rainfall Fields, sponsored by AGU, was the first of its kind; it was devoted to strengthening scientific interaction between the North American and Latin American geophysics communities. It was hosted by Universidad Simon Bolivar and Instituto Internacional de Estudios Avanzados, in Caracas, Venezuela, during March 24-27, 1986. A total of 36 scientists from Latin America, the United States, Canada, and Europe participated. The conference, which was convened by I. Rodriguez-Iturbe (Universidad Simon Bolivar) and V. K. Gupta (University of Mississippi, University), brought together hydrologists, meteorologists, and mathematicians/statisticians in the name of enhancing an interdisciplinary focus on rainfall research.

  8. Rainfall simulation for environmental application

    Energy Technology Data Exchange (ETDEWEB)

    Shriner, D.S.; Abner, C.H.; Mann, L.K.

    1977-08-01

    Rain simulation systems have been designed for field and greenhouse studies which have the capability of reproducing the physical and chemical characteristics of natural rainfall. The systems permit the simulation of variations in rainfall and droplet size similar to that of natural precipitation. The systems are completely automatic and programmable, allowing unattended operation for periods of up to one week, and have been used to expose not only vegetation but also soils and engineering materials, making them versatile tools for studies involving simulated precipitation.

  9. Impact of rainfall spatial variability on Flash Flood Forecasting

    Science.gov (United States)

    Douinot, Audrey; Roux, Hélène; Garambois, Pierre-André; Larnier, Kevin

    2014-05-01

    built for each studied catchment. The proposed methodology is applied on three Mediterranean catchments often submitted to flash floods. The new forecasting method as well as the Flash Flood Guidance method (uniform rainfall threshold) are tested on 25 flash floods events that had occurred on those catchments. Results show a significant impact of rainfall spatial variability. Indeed, it appears that the uniform rainfall threshold (FFG threshold) always overestimates the observed rainfall threshold. The difference between the FFG threshold and the proposed threshold ranges from 8% to 30%. The proposed methodology allows the calculation of a threshold more representative of the observed one. However, results strongly depend on the related event duration and on the catchment properties. For instance, the impact of the rainfall spatial variability seems to be correlated with the catchment size. According to these results, it seems to be interesting to introduce information on the catchment properties in the threshold calculation. Flash Flood Guidance Improvement Team, 2003. River Forecast Center (RFC) Development Management Team. Final Report. Office of Hydrologic Development (OHD), Silver Spring, Mary-land. Le Lay, M. and Saulnier, G.-M., 2007. Exploring the signature of climate and landscape spatial variabilities in flash flood events: Case of the 8-9 September 2002 Cévennes-Vivarais catastrophic event. Geophysical Research Letters, 34(L13401), doi:10.1029/2007GL029746. Roux, H., Labat, D., Garambois, P.-A., Maubourguet, M.-M., Chorda, J. and Dartus, D., 2011. A physically-based parsimonious hydrological model for flash floods in Mediterranean catchments. Nat. Hazards Earth Syst. Sci. J1 - NHESS, 11(9), 2567-2582. Zoccatelli, D., Borga, M., Zanon, F., Antonescu, B. and Stancalie, G., 2010. Which rainfall spatial information for flash flood response modelling? A numerical investigation based on data from the Carpathian range, Romania. Journal of Hydrology, 394(1-2), 148-161.

  10. The influence of seasonal rainfall upon Sahel vegetation

    DEFF Research Database (Denmark)

    Proud, Simon Richard; Rasmussen, Laura Vang

    2011-01-01

    include changes in total yearly rainfall, land-use change and migration. But these factors are not fully explanatory. This study addresses other possible factors for variation in vegetation patterns through the analysis of the Normalized Difference Vegetation Index (NDVI) produced by satellite sensors. We...... focus on precipitation, but instead of looking at the total yearly amount of rainfall, the intra-annual variation is examined. Here we show that plant growth is strongly correlated with the number and frequency of days within the rainy season upon which there is no rainfall. Furthermore, we find...... that if the start of the growing season, or the period in which the peak growth of vegetation occurs, is especially dry then plant growth may be stunted throughout the remainder of the season. These results enable better understanding of climate dynamics in the Sahel and allow more accurate forecasting of crop...

  11. Where do forests influence rainfall?

    Science.gov (United States)

    Wang-Erlandsson, Lan; van der Ent, Ruud; Fetzer, Ingo; Keys, Patrick; Savenije, Hubert; Gordon, Line

    2017-04-01

    Forests play a major role in hydrology. Not only by immediate control of soil moisture and streamflow, but also by regulating climate through evaporation (i.e., transpiration, interception, and soil evaporation). The process of evaporation travelling through the atmosphere and returning as precipitation on land is known as moisture recycling. Whether evaporation is recycled depends on wind direction and geography. Moisture recycling and forest change studies have primarily focused on either one region (e.g. the Amazon), or one biome type (e.g. tropical humid forests). We will advance this via a systematic global inter-comparison of forest change impacts on precipitation depending on both biome type and geographic location. The rainfall effects are studied for three contemporary forest changes: afforestation, deforestation, and replacement of mature forest by forest plantations. Furthermore, as there are indications in the literature that moisture recycling in some places intensifies during dry years, we will also compare the rainfall impacts of forest change between wet and dry years. We model forest change effects on evaporation using the global hydrological model STEAM and trace precipitation changes using the atmospheric moisture tracking scheme WAM-2layers. This research elucidates the role of geographical location of forest change driven modifications on rainfall as a function of the type of forest change and climatic conditions. These knowledge gains are important at a time of both rapid forest and climate change. Our conclusions nuance our understanding of how forests regulate climate and pinpoint hotspot regions for forest-rainfall coupling.

  12. The effects of rainfall regimes and terracing on runoff and erosion in the Three Gorges area, China.

    Science.gov (United States)

    Xu, Qin-Xue; Wu, Pan; Dai, Jun-Feng; Wang, Tian-Wei; Li, Zhao-Xia; Cai, Chong-Fa; Shi, Zhi-Hua

    2018-04-01

    Changes in natural rainfall regimes have taken place and are expected to become more pronounced in future decades. These changes are also likely to be accompanied by changes in crop management practices. The main purpose of this study was to analyze runoff and soil loss in relation to rainfall regimes and terracing in the Three Gorges area, China. Based on 10 years of field observation and k-mean clusters, 101 rainfall events were grouped into three rainfall regimes. Rainfall regime I was the group of events with strong rainfall intensity, high frequency, and short duration. Rainfall regime III consisted of events with low intensity, long duration, and high rainfall amount. Rainfall regime II was the aggregation of events of high intensity and amount, and less frequent occurrence. The results showed that event runoff coefficients were not significantly different among rainfall regimes. However, the average soil erosion rates in rainfall regimes I and II were significantly higher than that in regime III. The average erosion rates under rainfall regimes I, II, and III were 21.6, 39.7, and 9.8 g m -2 , respectively. The effect of rainfall regime on soil erosion also was changed by terracing. On unterraced cropland, soil erosion rate in rainfall regime I is significantly higher than that in regime III. However, the situation did not exist in unterraced orchard. Terracing significantly reduced runoff and soil erosion, and compensated the effects of rainfall regime on soil erosion, which indicated that runoff and erosion in terraced system may be little influenced by climate change. Based on these results, it was suggested more attention should be paid to the timing of rainfall events in relation to crop development and the high erosion on unterraced citrus orchard to control soil erosion in this area.

  13. Origins and interrelationship of Intraseasonal rainfall variations around the Maritime Continent during boreal winter

    Science.gov (United States)

    Cao, Xi; Wu, Renguang

    2018-04-01

    Large intraseasonal rainfall variations are identified over the southern South China Sea (SSCS), tropical southeastern Indian Ocean (SEIO), and east coast of the Philippines (EPHI) in boreal winter. The present study contrasts origins and propagations and investigates interrelations of intraseasonal rainfall variations on the 10-20- and 30-60-day time scales in these regions. Different origins are identified for intraseasonal rainfall anomalies over the SSCS, SEIO, and EPHI on both time scales. On the 10-20-day time scale, strong northerly or northeasterly wind anomalies related to the East Asian winter monsoon (EAWM) play a major role in intraseasonal rainfall variations over the SSCS and EPHI. On the 30-60-day time scale, both the intraseasonal signal from the tropical Indian Ocean and the EAWM-related wind anomalies contribute to intraseasonal rainfall variations over the SSCS, whereas the EAWM-related wind anomalies have a major contribution to the intraseasonal rainfall variations over the EPHI. No relation is detected between the intraseasonal rainfall variations over the SEIO and the EAWM on both the 10-20-day and 30-60-day time scales. The anomalies associated with intraseasonal rainfall variations over the SSCS and EPHI propagate northwestward and northeastward, respectively, on the 10-20- and 30-60-day time scales. The intraseasonal rainfall anomalies display northwestward and northward propagation over the Bay of Bengal, respectively, on the 10-20- and 30-60-day time scales.

  14. Northern-hemispheric differential warming is the key to understanding the discrepancies in the projected Sahel rainfall.

    Science.gov (United States)

    Park, Jong-Yeon; Bader, Jürgen; Matei, Daniela

    2015-01-21

    Future projections of the Sahel rainfall are highly uncertain, with different climate models showing widely differing rainfall trends. Moreover, the twentieth-century cross-model consensus linking Sahel rainfall to tropical sea-surface temperatures (SSTs) is no longer applicable in the twenty-first century. Here we show that the diverse future Northern Hemisphere differential warming between extratropical and tropical SSTs can explain the discrepancy in the projected Sahel rainfall. The relationship between SST and Sahel rainfall that holds for the twentieth-century persists into the twenty-first century when the differential SST warming is taken into account. A suite of SST-sensitivity experiments confirms that strong Northern Hemisphere extratropical warming induces a significant increase in Sahel rainfall, which can predominate over the drying impact of tropical SST warming. These results indicate that a trustworthy projection of Sahel rainfall requires the estimation of the most likely future Northern-hemispheric differential warming.

  15. Increased rainfall variability and N addition accelerate litter decomposition in a restored prairie.

    Science.gov (United States)

    Schuster, Michael J

    2016-03-01

    Anthropogenic nitrogen deposition and projected increases in rainfall variability (the frequency of drought and heavy rainfall events) are expected to strongly influence ecosystem processes such as litter decomposition. However, how these two global change factors interact to influence litter decomposition is largely unknown. I examined how increased rainfall variability and nitrogen addition affected mass and nitrogen loss of litter from two tallgrass prairie species, Schizachyrium scoparium and Solidago canadensis, and isolated the effects of each during plant growth and during litter decomposition. I increased rainfall variability by consolidating ambient rainfall into larger events and simulated chronic nitrogen deposition using a slow-release urea fertilizer. S. scoparium litter decay was more strongly regulated by the treatments applied during plant growth than by those applied during decomposition. During plant growth, increased rainfall variability resulted in S. scoparium litter that subsequently decomposed more slowly and immobilized more nitrogen than litter grown under ambient conditions, whereas nitrogen addition during plant growth accelerated subsequent mass loss of S. scoparium litter. In contrast, S. canadensis litter mass and N losses were enhanced under either N addition or increased rainfall variability both during plant growth and during decomposition. These results suggest that ongoing changes in rainfall variability and nitrogen availability are accelerating nutrient cycling in tallgrass prairies through their combined effects on litter quality, environmental conditions, and plant community composition.

  16. Cross-timescale Interference and Rainfall Extreme Events in South Eastern South America

    Science.gov (United States)

    Munoz, Angel G.

    different timescales increases the predictive skill. This fact is in agreement with the Cross-timescale Interference Conjecture proposed in the first part of the thesis. At seasonal scale, a combination of those weather types tends to outperform all the other potential predictors explored, i.e., sea surface temperature patterns, phases of the Madden-Julian Oscillation, and combinations of both. Spatially averaged Kendall’s τ improvements of 43% for the potential predictability and 23% for realtime predictions are attained with respect to standard models considering sea-surface temperature fields alone. A new subseasonal-to-seasonal predictive methodology for extreme rainfall events is proposed, based on probability forecasts of seasonal sequences of these weather types. The cross-validated realtime skill of the new probabilistic approach, as measured by the Hit Score and the Heidke Skill Score, is on the order of twice that associated with climatological values. The approach is designed to offer useful subseasonal-to-seasonal climate information to decision-makers interested not only in how many extreme events will happen in the season, but also in how, when and where those events will probably occur. In order to gain further understanding about how the cross-timescale interference occurs, an externally-forced Lorenz model is used to explore the impact of different kind of forcings, at inter-annual and decadal scales, in the establishment of constructive interactions associated with the simulated “extreme events”. Using a wavelet analysis, it is shown that this simple model is capable of reproducing the same kind of cross-timescale structures observed in the wavelet power spectrum of the Nino3.4 index only when it is externally forced by both inter-annual and decadal signals: the annual cycle and a decadal forcing associated with the natural solar variability. The nature of this interaction is non-linear, and it impacts both mean and extreme values in the time series

  17. Sediment output from a post-mining catchment - Centennial impacts using stochastically generated rainfall

    Science.gov (United States)

    Hancock, G. R.; Verdon-Kidd, D.; Lowry, J. B. C.

    2017-01-01

    Computer based landscape evolution models can provide insight into both erosion rates and processes (i.e. sheetwash, rill, gully erosion). One important data requirement of these models is long term, high quality, high-temporal resolution rainfall data (given that the physical nature of the erosion process is strongly related to rainfall). However, in many cases such data is limited - data is often short, incomplete or not of a sufficient temporal resolution. Therefore, the aim of this study was to test the sensitivity of modelled erosion rates to small changes in rainfall input. To achieve this we firstly assess the existing rainfall data from an established weather station and secondly, stochastically generate rainfall time series based on the longest and most reliable rainfall data. We then test the sensitivity of different rainfall sequences on sediment output using a well-tested landscape evolution and sediment transport model (CAESAR-Lisflood) over a simulated period of 100 y on a proposed rehabilitated mine landform. It was found that each rainfall scenario produces a unique pattern of erosion (i.e. the location and extent of the gullies is variable). Further, each rainfall scenario produces a unique pattern of sediment output that suggests non-linear processes. Importantly, this is the first time stochastically generated rainfall has been employed in landform evolution modeling and provides a statistical approach to quantify sediment transport and landform evolution. The method demonstrates a risk based approach and allows rainfall, runoff and sediment transport studies to be conducted in data poor environments. The findings clearly demonstrate that rainfall variability can greatly affect sediment transport and form of erosion as well as landscape evolution. This information is of particular importance for the design and testing of rehabilitated landscape systems such as post-mining landscapes.

  18. Spatial variability and rainfall characteristics of Kerala

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    the Palghat gap, which is about 24kms in length. The south-west monsoon current, which brings in most of the annual rainfall, gets a forced ascent at the Ghats and the windward slopes experience very heavy rainfall. However, rainfall is not uniformly distributed on the windward slopes and there are pockets of very heavy ...

  19. Stochastic modelling of daily rainfall sequences

    NARCIS (Netherlands)

    Buishand, T.A.

    1977-01-01

    Rainfall series of different climatic regions were analysed with the aim of generating daily rainfall sequences. A survey of the data is given in I, 1. When analysing daily rainfall sequences one must be aware of the following points:
    a. Seasonality. Because of seasonal variation

  20. North Pacific Westerly Jet Influence of the Winter Hawaii Rainfall in the last 21,000 years

    Science.gov (United States)

    Li, S.; Elison Timm, O.

    2017-12-01

    Hawaii rainfall has a strong seasonality which has more rainfall during the winter than summer. Part of the winter rainfall is from extratropical weather disturbances. Kona lows (KL) are important contributors to the annual rainfall budget of the Hawaiian Islands. KL activity is found to have a strong relationship with the North Pacific climate variability. The goal of the research is to test the hypothesis that changes in the strength and position of the upper level zonal wind jet is a key driver for regional rainfall changes. The main objectives are (1) to identify the relationship between North Pacific westerly jet strength and KL activity in present day climate, (2) to test the stability of this relationship under past climatic conditions, and (3) to explore the teleconnection between Hawaii and North America. For the present-day analysis of the westerly jet, the zonal wind at 250hPa is used from ERA-interim data from 1979-2014. The potential vorticity is used as a measure of extratropical synoptic activity. The Hawaii Rainfall Index is from the Rainfall Atlas of Hawaii (seasonal means, 1920-2012). For the paleoclimatic study, the transient TraCE-21ka simulation is used for the zonal wind - Hawaii rainfall analysis. The results of present-day analysis show that when the jet extends farther into the eastern Pacific sector the Kona Low activity is reduced, less winter rainfall is observed over Hawaii and more rainfall over the California region. The jet position-rainfall relationship was investigated within the TrACE-21 simulation. For the TraCE-21ka dataset, there is an increasing rainfall trend from 21kBP to 14kBP; this period coincides with a gradual decrease in the strength of the westerly wind jet. The results show that the westerly jet strength has a strong influence of the Kona Low activity and the rainfall over Hawaii both in the present and the past.

  1. Intensive rainfall recharges tropical groundwaters

    International Nuclear Information System (INIS)

    Jasechko, Scott; Taylor, Richard G

    2015-01-01

    Dependence upon groundwater to meet rising agricultural and domestic water needs is expected to increase substantially across the tropics where, by 2050, over half of the world’s population is projected to live. Rare, long-term groundwater-level records in the tropics indicate that groundwater recharge occurs disproportionately from heavy rainfalls exceeding a threshold. The ubiquity of this bias in tropical groundwater recharge to intensive precipitation is, however, unknown. By relating available long-term records of stable-isotope ratios of O and H in tropical precipitation (15 sites) to those of local groundwater, we reveal that groundwater recharge in the tropics is near-uniformly (14/15 sites) biased to intensive monthly rainfall, commonly exceeding the ∼70th intensity decile. Our results suggest that the intensification of precipitation brought about by global warming favours groundwater replenishment in the tropics. Nevertheless, the processes that transmit intensive rainfall to groundwater systems and enhance the resilience of tropical groundwater storage in a warming world, remain unclear. (letter)

  2. Assessing spatio-temporal rainfall variability in a tropical mountain area (Ethiopia) using NOAA's rainfall estimates

    OpenAIRE

    Jacob, Miro; Frankl, Amaury; Haile, Mitiku; Zwertvaegher, Ann; Nyssen, Jan

    2013-01-01

    Seasonal and interannual variation in rainfall can cause massive economic loss for farmers and pastoralists, not only because of deficient total rainfall amounts but also because of long dry spells within the rainy season. The semi-arid to sub-humid mountain climate of the North Ethiopian Highlands is especially vulnerable to rainfall anomalies. In this article, spatio-temporal rainfall patterns are analysed on a regional scale in the North Ethiopian Highlands using satellite-derived rainfall...

  3. Seasonal and inter-annual dynamics in the stable oxygen isotope compositions of water pools in a temperate humid grassland ecosystem: results from MIBA sampling and MuSICA modelling

    Science.gov (United States)

    Hirl, Regina; Schnyder, Hans; Auerswald, Karl; Vetter, Sylvia; Ostler, Ulrike; Schleip, Inga; Wingate, Lisa; Ogée, Jérôme

    2015-04-01

    The oxygen isotope composition (δ18O) of water in terrestrial ecosystems usually shows strong and dynamic variations within and between the various compartments. These variations originate from changes in the δ18O of water inputs (e.g. rain or water vapour) and from 18O fractionation phenomena in the soil-plant-atmosphere continuum. Investigations of δ18O in ecosystem water pools and of their main drivers can help us understand water relations at plant, canopy or ecosystem scale and interpret δ18O signals in plant and animal tissues as paleo-climate proxies. During the vegetation periods of 2006 to 2012, soil, leaf and stem water as well as atmospheric humidity, rain water and groundwater were sampled at bi-weekly intervals in a temperate humid pasture of the Grünschwaige Grassland Research Station near Munich (Germany). The sampling was performed following standardised MIBA (Moisture Isotopes in the Biosphere and Atmosphere) protocols. Leaf water samples were prepared from a mixture of co-dominant species in the plant community in order to obtain a canopy-scale leaf water δ18O signal. All samples were then analysed for their δ18O compositions. The measured δ18O of leaf, stem and soil water were then compared with the δ18O signatures simulated by the process-based isotope-enabled ecosystem model MuSICA (Multi-layer Simulator of the Interactions between a vegetation Canopy and the Atmosphere). MuSICA integrates current mechanistic understanding of processes in the soil-plant-atmosphere continuum. Hence, the comparison of modelled and measured data allows the identification of gaps in current knowledge and of questions to be tackled in the future. Soil and plant characteristics for model parameterisation were derived from investigations at the experimental site and supplemented by values from the literature. Eddy-covariance measurements of ecosystem CO2 (GPP, NEE) and energy (H, LE) fluxes and soil temperature data were used for model evaluation. The

  4. Observed daily large-scale rainfall patterns during BOBMEX-1999

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    A daily rainfall dataset and the corresponding rainfall maps have been produced by objective analysis of rainfall data. The satellite estimate of rainfall and the raingauge values are merged to form the final analysis. Associated with epochs of monsoon these rainfall maps are able to show the rainfall activities over India and ...

  5. Response of African humid tropical forests to recent rainfall anomalies.

    Science.gov (United States)

    Asefi-Najafabady, Salvi; Saatchi, Sassan

    2013-01-01

    During the last decade, strong negative rainfall anomalies resulting from increased sea surface temperature in the tropical Atlantic have caused extensive droughts in rainforests of western Amazonia, exerting persistent effects on the forest canopy. In contrast, there have been no significant impacts on rainforests of West and Central Africa during the same period, despite large-scale droughts and rainfall anomalies during the same period. Using a combination of rainfall observations from meteorological stations from the Climate Research Unit (CRU; 1950-2009) and satellite observations of the Tropical Rainfall Measuring Mission (TRMM; 1998-2010), we show that West and Central Africa experienced strong negative water deficit (WD) anomalies over the last decade, particularly in 2005, 2006 and 2007. These anomalies were a continuation of an increasing drying trend in the region that started in the 1970s. We monitored the response of forests to extreme rainfall anomalies of the past decade by analysing the microwave scatterometer data from QuickSCAT (1999-2009) sensitive to variations in canopy water content and structure. Unlike in Amazonia, we found no significant impacts of extreme WD events on forests of Central Africa, suggesting potential adaptability of these forests to short-term severe droughts. Only forests near the savanna boundary in West Africa and in fragmented landscapes of the northern Congo Basin responded to extreme droughts with widespread canopy disturbance that lasted only during the period of WD. Time-series analyses of CRU and TRMM data show most regions in Central and West Africa experience seasonal or decadal extreme WDs (less than -600 mm). We hypothesize that the long-term historical extreme WDs with gradual drying trends in the 1970s have increased the adaptability of humid tropical forests in Africa to droughts.

  6. Characterization of the Sahelian-Sudan rainfall based on observations and regional climate models

    Science.gov (United States)

    Salih, Abubakr A. M.; Elagib, Nadir Ahmed; Tjernström, Michael; Zhang, Qiong

    2018-04-01

    The African Sahel region is known to be highly vulnerable to climate variability and change. We analyze rainfall in the Sahelian Sudan in terms of distribution of rain-days and amounts, and examine whether regional climate models can capture these rainfall features. Three regional models namely, Regional Model (REMO), Rossby Center Atmospheric Model (RCA) and Regional Climate Model (RegCM4), are evaluated against gridded observations (Climate Research Unit, Tropical Rainfall Measuring Mission, and ERA-interim reanalysis) and rain-gauge data from six arid and semi-arid weather stations across Sahelian Sudan over the period 1989 to 2008. Most of the observed rain-days are characterized by weak (0.1-1.0 mm/day) to moderate (> 1.0-10.0 mm/day) rainfall, with average frequencies of 18.5% and 48.0% of the total annual rain-days, respectively. Although very strong rainfall events (> 30.0 mm/day) occur rarely, they account for a large fraction of the total annual rainfall (28-42% across the stations). The performance of the models varies both spatially and temporally. RegCM4 most closely reproduces the observed annual rainfall cycle, especially for the more arid locations, but all of the three models fail to capture the strong rainfall events and hence underestimate its contribution to the total annual number of rain-days and rainfall amount. However, excessive moderate rainfall compensates this underestimation in the models in an annual average sense. The present study uncovers some of the models' limitations in skillfully reproducing the observed climate over dry regions, will aid model users in recognizing the uncertainties in the model output and will help climate and hydrological modeling communities in improving models.

  7. Evaluation of empirical relationships between extreme rainfall and daily maximum temperature in Australia

    Science.gov (United States)

    Herath, Sujeewa Malwila; Sarukkalige, Ranjan; Nguyen, Van Thanh Van

    2018-01-01

    Understanding the relationships between extreme daily and sub-daily rainfall events and their governing factors is important in order to analyse the properties of extreme rainfall events in a changing climate. Atmospheric temperature is one of the dominant climate variables which has a strong relationship with extreme rainfall events. In this study, a temperature-rainfall binning technique is used to evaluate the dependency of extreme rainfall on daily maximum temperature. The Clausius-Clapeyron (C-C) relation was found to describe the relationship between daily maximum temperature and a range of rainfall durations from 6 min up to 24 h for seven Australian weather stations, the stations being located in Adelaide, Brisbane, Canberra, Darwin, Melbourne, Perth and Sydney. The analysis shows that the rainfall - temperature scaling varies with location, temperature and rainfall duration. The Darwin Airport station shows a negative scaling relationship, while the other six stations show a positive relationship. To identify the trend in scaling relationship over time the same analysis is conducted using data covering 10 year periods. Results indicate that the dependency of extreme rainfall on temperature also varies with the analysis period. Further, this dependency shows an increasing trend for more extreme short duration rainfall and a decreasing trend for average long duration rainfall events at most stations. Seasonal variations of the scale changing trends were analysed by categorizing the summer and autumn seasons in one group and the winter and spring seasons in another group. Most of 99th percentile of 6 min, 1 h and 24 h rain durations at Perth, Melbourne and Sydney stations show increasing trend for both groups while Adelaide and Darwin show decreasing trend. Furthermore, majority of scaling trend of 50th percentile are decreasing for both groups.

  8. Examining rainfall and cholera dynamics in Haiti using statistical and dynamic modeling approaches.

    Science.gov (United States)

    Eisenberg, Marisa C; Kujbida, Gregory; Tuite, Ashleigh R; Fisman, David N; Tien, Joseph H

    2013-12-01

    Haiti has been in the midst of a cholera epidemic since October 2010. Rainfall is thought to be associated with cholera here, but this relationship has only begun to be quantitatively examined. In this paper, we quantitatively examine the link between rainfall and cholera in Haiti for several different settings (including urban, rural, and displaced person camps) and spatial scales, using a combination of statistical and dynamic models. Statistical analysis of the lagged relationship between rainfall and cholera incidence was conducted using case crossover analysis and distributed lag nonlinear models. Dynamic models consisted of compartmental differential equation models including direct (fast) and indirect (delayed) disease transmission, where indirect transmission was forced by empirical rainfall data. Data sources include cholera case and hospitalization time series from the Haitian Ministry of Public Health, the United Nations Water, Sanitation and Health Cluster, International Organization for Migration, and Hôpital Albert Schweitzer. Rainfall data was obtained from rain gauges from the U.S. Geological Survey and Haiti Regeneration Initiative, and remote sensing rainfall data from the National Aeronautics and Space Administration Tropical Rainfall Measuring Mission. A strong relationship between rainfall and cholera was found for all spatial scales and locations examined. Increased rainfall was significantly correlated with increased cholera incidence 4-7 days later. Forcing the dynamic models with rainfall data resulted in good fits to the cholera case data, and rainfall-based predictions from the dynamic models closely matched observed cholera cases. These models provide a tool for planning and managing the epidemic as it continues. Copyright © 2013 Elsevier B.V. All rights reserved.

  9. Polarimetric rainfall retrieval from a C-Band weather radar in a tropical environment (The Philippines)

    Science.gov (United States)

    Crisologo, I.; Vulpiani, G.; Abon, C. C.; David, C. P. C.; Bronstert, A.; Heistermann, Maik

    2014-11-01

    We evaluated the potential of polarimetric rainfall retrieval methods for the Tagaytay C-Band weather radar in the Philippines. For this purpose, we combined a method for fuzzy echo classification, an approach to extract and reconstruct the differential propagation phase, Φ DP , and a polarimetric self-consistency approach to calibrate horizontal and differential reflectivity. The reconstructed Φ DP was used to estimate path-integrated attenuation and to retrieve the specific differential phase, K DP . All related algorithms were transparently implemented in the Open Source radar processing software wradlib. Rainfall was then estimated from different variables: from re-calibrated reflectivity, from re-calibrated reflectivity that has been corrected for path-integrated attenuation, from the specific differential phase, and from a combination of reflectivity and specific differential phase. As an additional benchmark, rainfall was estimated by interpolating the rainfall observed by rain gauges. We evaluated the rainfall products for daily and hourly accumulations. For this purpose, we used observations of 16 rain gauges from a five-month period in the 2012 wet season. It turned out that the retrieval of rainfall from K DP substantially improved the rainfall estimation at both daily and hourly time scales. The measurement of reflectivity apparently was impaired by severe miscalibration while K DP was immune to such effects. Daily accumulations of rainfall retrieved from K DP showed a very low estimation bias and small random errors. Random scatter was, though, strongly present in hourly accumulations.

  10. Recurrent daily rainfall patterns over South Africa and associated dynamics during the core of the austral summer

    CSIR Research Space (South Africa)

    Cretat, J

    2010-12-01

    Full Text Available . Amongst them, one cluster looks most like the rainfall and circulation mean picture. Another one, representing 37% of the days, describes strong negative rainfall anomalies over South Africa resulting from a regional barotropic trough-ridge-trough wave...

  11. Effects of rainfall patterns on runoff and soil erosion in field plots

    Directory of Open Access Journals (Sweden)

    Mohamad Ayob Mohamadi

    2015-12-01

    Full Text Available Soil erosion processes during a storm are strongly affected by intra-storm variations in rainfall characteristics. Four storm patterns, each with a different rainfall intensity variation were separated. The storm patterns were: (1 increasing rainfall intensity (2 increasing then decreasing intensity (3 decreasing intensity (4 decreasing then increasing intensity. After each erosive rainfall (12 events, Runoff and suspended sediment samples were collected in each plot׳s tank which is located on hillslopes of the basin of Khamsan. Main storm characteristics and soil losses were plotted and equation of the line of best fit were selected. Analysis of variance (ANOVA was used to determine response of runoff and soil erosion to storm patterns. Results showed that in lower rainfall intensities a linear function fits the relationship between soil loss and rainfall intensity whereas this function tends to be non-linear at higher intensities. Also a strong non-linear relationship was found between different quartiles of storm and soil loss. Statistical analysis revealed significant differences in total runoff, soil loss and sediment concentration across four storm patterns (P<0.001 but no differences in the runoff coefficient. In particular, storms with increasing rainfall intensity yielded highest quantities of eroded sediments, total runoff and highest sediment concentrations followed by increasing then decreasing, decreasing then increasing and decreasing intensity, respectively.

  12. Contrasting response of rainfall extremes to increase in surface air and dewpoint temperatures at urban locations in India.

    Science.gov (United States)

    Ali, Haider; Mishra, Vimal

    2017-04-27

    Rainfall extremes are projected to increase under the warming climate. The Clausius-Clapeyron (C-C) relationship provides a physical basis to understand the sensitivity of rainfall extremes in response to warming, however, relationships between rainfall extremes and air temperature over tropical regions remain uncertain. Here, using station based observations and remotely sensed rainfall, we show that at a majority of urban locations, rainfall extremes show a negative scaling relationship against surface air temperature (SAT) in India. The negative relationship between rainfall extremes and SAT in India can be attributed to cooling (SAT) due to the monsoon season rain events in India, suggesting that SAT alone is not a good predictor of rainfall extremes in India. In contrast, a strong (higher than C-C rate) positive relationship between rainfall extremes and dew point (DPT) and tropospheric temperature (T850) is shown for most of the stations, which was previously unexplored. Subsequently, DPT and T850 were used as covariates for non-stationary daily design storms. Higher magnitude design storms were obtained under the assumption of a non-stationary climate. The contrasting relationship between rainfall extremes with SAT and DPT has implications for understanding the changes in rainfall extremes in India under the projected climate.

  13. Deforestation and rainfall recycling in Brazil: Is decreased forest cover connectivity associated with decreased rainfall connectivity?

    Science.gov (United States)

    Adera, S.; Larsen, L.; Levy, M. C.; Thompson, S. E.

    2017-12-01

    In the Brazilian rainforest-savanna transition zone, deforestation has the potential to significantly affect rainfall by disrupting rainfall recycling, the process by which regional evapotranspiration contributes to regional rainfall. Understanding rainfall recycling in this region is important not only for sustaining Amazon and Cerrado ecosystems, but also for cattle ranching, agriculture, hydropower generation, and drinking water management. Simulations in previous studies suggest complex, scale-dependent interactions between forest cover connectivity and rainfall. For example, the size and distribution of deforested patches has been found to affect rainfall quantity and spatial distribution. Here we take an empirical approach, using the spatial connectivity of rainfall as an indicator of rainfall recycling, to ask: as forest cover connectivity decreased from 1981 - 2015, how did the spatial connectivity of rainfall change in the Brazilian rainforest-savanna transition zone? We use satellite forest cover and rainfall data covering this period of intensive forest cover loss in the region (forest cover from the Hansen Global Forest Change dataset; rainfall from the Climate Hazards Infrared Precipitation with Stations dataset). Rainfall spatial connectivity is quantified using transfer entropy, a metric from information theory, and summarized using network statistics. Networks of connectivity are quantified for paired deforested and non-deforested regions before deforestation (1981-1995) and during/after deforestation (2001-2015). Analyses reveal a decline in spatial connectivity networks of rainfall following deforestation.

  14. Rainfall variability in the Netherlands from radars, rain gauges, and disdrometers

    NARCIS (Netherlands)

    Beek, van de R.

    2013-01-01

    <strong>Chapter 1strong>. This thesis presents studies on the variability of precipitation in the Netherlands from datasets collected by radars, rain gauges and disdrometers. Accurate rainfall estimates are highly relevant in hydrology, meteorology and climatology as precipitation has a large

  15. Fluctuations of the relationship between ENSO and northeast Australian rainfall

    Science.gov (United States)

    Cai, W.; Whetton, P. H.; Pittock, A. B.

    It is well known that during an El Niño-Southern Oscillation (ENSO) warm event, drought occurs in regions of northeastern (NE) Australia, leading to anomalously low annual rainfall. The present study explores fluctuations of this ENSO-rainfall relationship. It is found that the relationship tends to weaken when the linearly detrended global mean temperature is rising or particularly high, as in the period of 1931-45 period and since the late 1970s. Prior to a weakening, a correlation pattern of increased rainfall during El Niño events is seen first in northwestern Australia, then in eastern and southeastern Australia, and eventually in NE Australia. The 1931-45 period was particularly intriguing, when in terms of rainfall variability over NE Australia, the interannual ENSO-rainfall relationship went through a process of weakening, reversal, and rapid recovery. Features associated with the reversal are therefore examined and these features are: (1) the global background anomaly pattern (upon which internnal ENSO events operate) is ENSO-like; (2) ENSO sea surface temperature (SST) anomalies in tropical Pacific are weaker compared with those averaged over all ENSO events, whereas SST anomalies in the mid- to-high latitude Pacific (which have opposing polarity to those in tropical Pacific) are larger; (3) there is strong coherence between ENSO and variability in northern mid- to high-latitudes; and (4) the relationship that an El Niño event contributes to a warming anomaly of global mean SST weakens. Possible interrelationship among these features are discussed.

  16. Interannual rainfall variability and SOM-based circulation classification

    Science.gov (United States)

    Wolski, Piotr; Jack, Christopher; Tadross, Mark; van Aardenne, Lisa; Lennard, Christopher

    2018-01-01

    Self-Organizing Maps (SOM) based classifications of synoptic circulation patterns are increasingly being used to interpret large-scale drivers of local climate variability, and as part of statistical downscaling methodologies. These applications rely on a basic premise of synoptic climatology, i.e. that local weather is conditioned by the large-scale circulation. While it is clear that this relationship holds in principle, the implications of its implementation through SOM-based classification, particularly at interannual and longer time scales, are not well recognized. Here we use a SOM to understand the interannual synoptic drivers of climate variability at two locations in the winter and summer rainfall regimes of South Africa. We quantify the portion of variance in seasonal rainfall totals that is explained by year to year differences in the synoptic circulation, as schematized by a SOM. We furthermore test how different spatial domain sizes and synoptic variables affect the ability of the SOM to capture the dominant synoptic drivers of interannual rainfall variability. Additionally, we identify systematic synoptic forcing that is not captured by the SOM classification. The results indicate that the frequency of synoptic states, as schematized by a relatively disaggregated SOM (7 × 9) of prognostic atmospheric variables, including specific humidity, air temperature and geostrophic winds, captures only 20-45% of interannual local rainfall variability, and that the residual variance contains a strong systematic component. Utilising a multivariate linear regression framework demonstrates that this residual variance can largely be explained using synoptic variables over a particular location; even though they are used in the development of the SOM their influence, however, diminishes with the size of the SOM spatial domain. The influence of the SOM domain size, the choice of SOM atmospheric variables and grid-point explanatory variables on the levels of explained

  17. Solar induced inter-annual variability of ozone

    Science.gov (United States)

    Fytterer, Tilo; Nieder, Holger; Perot, Kristell; Sinnhuber, Miriam; Stiller, Gabriele; Urban, Joachim

    2014-05-01

    Measurements by the Michelson Interferometer for Passive Atmospheric Sounding instrument on board the ENVIromental SATellite from 2005 - 2011 are used to investigate the impact of solar and geomagnetic activity on O3 in the stratosphere and mesosphere inside the Antarctic polar vortex. It is known from observations that energetic particles, mainly originating from the sun, precipitate in the Earth atmosphere and produce odd nitrogen NOx (N + NO + NO2) in the upper mesosphere and lower thermosphere, which is transported downwards into the stratosphere during polar winter. Results from global chemistry-transport models suggest that this leads to a depletion of O3 down to ~30 km at high latitudes during winter. Therefore it appears promising to search for a link between high energetic particles and O3 in actual data sets. Thus in this study, correlation analysis between a 26 days average centred around 1 Apr, 1 May and 1 Jun of several solar/geomagnetic indices (Ap index, F10.7 cm solar radio flux, Lyman-alpha, 2 MeV electrons flux) and 26 day running means from 1 Apr - 1 Nov of O3 in the altitude range from 20 - 70 km were performed. The results reveal negative correlation coefficients propagating downwards throughout the polar winter, at least for the Ap index and the 2 MeV electrons flux. Comparisons with TIMED/SABER and Odin/SMR O3 data are in moderate agreement, also showing a descending negative signal in either indices, but only for the correlation with 1 Apr.

  18. Non-parametric characterization of long-term rainfall time series

    Science.gov (United States)

    Tiwari, Harinarayan; Pandey, Brij Kishor

    2018-03-01

    The statistical study of rainfall time series is one of the approaches for efficient hydrological system design. Identifying, and characterizing long-term rainfall time series could aid in improving hydrological systems forecasting. In the present study, eventual statistics was applied for the long-term (1851-2006) rainfall time series under seven meteorological regions of India. Linear trend analysis was carried out using Mann-Kendall test for the observed rainfall series. The observed trend using the above-mentioned approach has been ascertained using the innovative trend analysis method. Innovative trend analysis has been found to be a strong tool to detect the general trend of rainfall time series. Sequential Mann-Kendall test has also been carried out to examine nonlinear trends of the series. The partial sum of cumulative deviation test is also found to be suitable to detect the nonlinear trend. Innovative trend analysis, sequential Mann-Kendall test and partial cumulative deviation test have potential to detect the general as well as nonlinear trend for the rainfall time series. Annual rainfall analysis suggests that the maximum changes in mean rainfall is 11.53% for West Peninsular India, whereas the maximum fall in mean rainfall is 7.8% for the North Mountainous Indian region. The innovative trend analysis method is also capable of finding the number of change point available in the time series. Additionally, we have performed von Neumann ratio test and cumulative deviation test to estimate the departure from homogeneity. Singular spectrum analysis has been applied in this study to evaluate the order of departure from homogeneity in the rainfall time series. Monsoon season (JS) of North Mountainous India and West Peninsular India zones has higher departure from homogeneity and singular spectrum analysis shows the results to be in coherence with the same.

  19. Real-time adjusting of rainfall estimates from commercial microwave links

    Science.gov (United States)

    Fencl, Martin; Dohnal, Michal; Bareš, Vojtěch

    2017-04-01

    at the beginning of rainfall events and during strong convective rainfalls, whereas performance during longer frontal rainfalls is almost unchanged. Our results clearly demonstrate that adjusting of CMLs to existing RGs represents a viable approach with great potential for real-time applications in stormwater management. This work was supported by the project of Czech Science Foundation (GACR) No.17-16389S. References: Fencl, M., Dohnal, M., Rieckermann, J. and Bareš, V.: Gauge-Adjusted Rainfall Estimates from Commercial Microwave Links, Hydrol Earth Syst. Sci., 2017 (accepted).

  20. Evaluation of Surface Runoff Generation Processes Using a Rainfall Simulator: A Small Scale Laboratory Experiment

    Science.gov (United States)

    Danáčová, Michaela; Valent, Peter; Výleta, Roman

    2017-12-01

    of 5 mm/min was used to irrigate a corrupted soil sample. The experiment was undertaken for several different slopes, under the condition of no vegetation cover. The results of the rainfall simulation experiment complied with the expectations of a strong relationship between the slope gradient, and the amount of surface runoff generated. The experiments with higher slope gradients were characterised by larger volumes of surface runoff generated, and by shorter times after which it occurred. The experiments with rainfall simulators in both laboratory and field conditions play an important role in better understanding of runoff generation processes. The results of such small scale experiments could be used to estimate some of the parameters of complex hydrological models, which are used to model rainfall-runoff and erosion processes at catchment scale.

  1. Trends in rainfall and rainfall-related extremes in the east coast of ...

    Indian Academy of Sciences (India)

    The east of peninsular Malaysia is not an exception for this, considering the evidence of heavy rainfall resulting in floods as an annual phenomenon and also water scarcity due to long dry spells in the region. This study examines recent trends in rainfall and rainfallrelated extremes such as, maximum daily rainfall, number of ...

  2. Spatiotemporal patterns and trends of Indian monsoonal rainfall extremes.

    Science.gov (United States)

    Malik, Nishant; Bookhagen, Bodo; Mucha, Peter J

    2016-02-28

    In this study, we provide a comprehensive analysis of trends in the extremes during the Indian summer monsoon (ISM) months (June to September) at different temporal and spatial scales. Our goal is to identify and quantify spatiotemporal patterns and trends that have emerged during the recent decades and may be associated with changing climatic conditions. Our analysis primarily relies on quantile regression that avoids making any subjective choices on spatial, temporal, or intensity pattern of extreme rainfall events. Our analysis divides the Indian monsoon region into climatic compartments that show different and partly opposing trends. These include strong trends towards intensified droughts in Northwest India, parts of Peninsular India, and Myanmar; in contrast, parts of Pakistan, Northwest Himalaya, and Central India show increased extreme daily rain intensity leading to higher flood vulnerability. Our analysis helps explain previously contradicting results of trends in average ISM rainfall.

  3. High-Resolution Discharge Forecasting for Snowmelt and Rainfall Mixed Events

    Directory of Open Access Journals (Sweden)

    Tomasz Berezowski

    2018-01-01

    Full Text Available Discharge events induced by mixture of snowmelt and rainfall are strongly nonlinear due to consequences of rain-on-snow phenomena and snowmelt dependence on energy balance. However, they received relatively little attention, especially in high-resolution discharge forecasting. In this study, we use Random Forests models for 24 h discharge forecasting in 1 h resolution in a 105.9 km 2 urbanized catchment in NE Poland: Biala River. The forcing data are delivered by Weather Research and Forecasting (WRF model in 1 h temporal and 4 × 4 km spatial resolutions. The discharge forecasting models are set in two scenarios with snowmelt and rainfall and rainfall only predictors in order to highlight the effect of snowmelt on the results (both scenarios use also pre-forecast discharge based predictors. We show that inclusion of snowmelt decrease the forecast errors for longer forecasts’ lead times. Moreover, importance of discharge based predictors is higher in the rainfall only models then in the snowmelt and rainfall models. We conclude that the role of snowmelt for discharge forecasting in mixed snowmelt and rainfall environments is in accounting for nonlinear physical processes, such as initial wetting and rain on snow, which cannot be properly modelled by rainfall only.

  4. Maximum daily rainfall in South Korea

    Indian Academy of Sciences (India)

    extreme value distributions to model rainfall data from South Korea. Keywords. Annual maximum daily rainfall; extreme value theory; generalized extreme value distribution; Gumbel distribution; return levels; trend; data analysis, ..... Pareto distribution and Markov chain based mod- els. One could fit these distributions to the ...

  5. Maximum daily rainfall in South Korea

    Indian Academy of Sciences (India)

    data at Belgrade, Yugoslavia; Atmosfera 5 47–56. Nguyen V T V, Nguyen T D and Wang H 1998 Regional estimation of short duration rainfall extremes; Water Sci- ence and Technology 37 15–19. Nguyen V T V, Nguyen T D and Ashkar F 2002 Regional fre- quency analysis of extreme rainfalls; Water Science and.

  6. Statistical Modelling of Extreme Rainfall in Taiwan

    NARCIS (Netherlands)

    L-F. Chu (Lan-Fen); M.J. McAleer (Michael); C-C. Chang (Ching-Chung)

    2012-01-01

    textabstractIn this paper, the annual maximum daily rainfall data from 1961 to 2010 are modelled for 18 stations in Taiwan. We fit the rainfall data with stationary and non-stationary generalized extreme value distributions (GEV), and estimate their future behaviour based on the best fitting model.

  7. Statistical Modelling of Extreme Rainfall in Taiwan

    NARCIS (Netherlands)

    L. Chu (LanFen); M.J. McAleer (Michael); C-H. Chang (Chu-Hsiang)

    2013-01-01

    textabstractIn this paper, the annual maximum daily rainfall data from 1961 to 2010 are modelled for 18 stations in Taiwan. We fit the rainfall data with stationary and non-stationary generalized extreme value distributions (GEV), and estimate their future behaviour based on the best fitting model.

  8. Rainfall and Development of Zika Virus

    African Journals Online (AJOL)

    2017-11-01

    Nov 1, 2017 ... between rainfall and incidence of arbovirus disease such as dengue is well demonstrated (2). For Zika virus an infection, a similar observation can be expected. A recent report from Thailand can also show the expected pattern of the prevalence of Zika virus infection in the areas with high rainfall (3).

  9. modelling relationship between rainfall variability and yields

    African Journals Online (AJOL)

    yield models should be used for planning and forecasting the yield of millet and sorghum in the study area. Key words: modelling, rainfall, yields, millet, sorghum. INTRODUCTION. Meteorological variables, such as rainfall parameters, temperature, sunshine hours, relative humidity, and wind velocity and soil moisture are.

  10. Maximum daily rainfall in South Korea

    Indian Academy of Sciences (India)

    Annual maxima of daily rainfall for the years 1961–2001 are modeled for five locations in South Korea (chosen to give a good geographical representation of the country). The generalized extreme value distribution is fitted to data from each location to describe the extremes of rainfall and to predict its future behavior.

  11. Relationship between summer monsoon rainfall and cyclogenesis ...

    Indian Academy of Sciences (India)

    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 ...

  12. Relationship between rainfall and microbiological contamination of ...

    African Journals Online (AJOL)

    Outbreaks of contamination events in many developing countries occur during periods of peak rainfall. This study presents evidence of direct pulse response of shallow groundwater contamination events to rainfall in Northern Mozambique. The objective of the paper is to establish both a statistical relationship between ...

  13. 10 Characterisation of Seasonal Rainfall.cdr

    African Journals Online (AJOL)

    Administrator

    These observations seem to reveal that long-term or climatological observations alone are no longer sufficient for seasonal rainfall prediction to aid .... W. Index values for six consecutive months are considered. If the index values are ..... could be described as extreme ENSO events, have high rainfall variability during the.

  14. Spatial variability and rainfall characteristics of Kerala

    Indian Academy of Sciences (India)

    Geographical regions of covariability in precipitation over the Kerala state are exposed using factor analysis. The results suggest that Kerala can be divided into three unique rainfall regions, each region having a similar covariance structure of annual rainfall. Stations north of 10°N (north Kerala) fall into one group and they ...

  15. ANALYSIS OF RAINFALL TREND IN ETHIOPIA INTRODUCTION

    African Journals Online (AJOL)

    Agricultural production in Ethiopia highly depends on rainfall and it is predominantly rain- fed. Variation of rainfall in space and time affects even the agricultural production system in the country. These have made the country vulnerable to famine. The famine is usually caused by drought. Historically, Ethiopia was affected ...

  16. Weather radar rainfall data in urban hydrology

    DEFF Research Database (Denmark)

    Thorndahl, Søren; Einfalt, Thomas; Willems, Patrick

    2017-01-01

    Application of weather radar data in urban hydrological applications has evolved significantly during the past decade as an alternative to traditional rainfall observations with rain gauges. Advances in radar hardware, data processing, numerical models, and emerging fields within urban hydrology...... necessitate an updated review of the state of the art in such radar rainfall data and applications. Three key areas with significant advances over the past decade have been identified: (1) temporal and spatial resolution of rainfall data required for different types of hydrological applications, (2) rainfall...... estimation, radar data adjustment and data quality, and (3) nowcasting of radar rainfall and real-time applications. Based on these three fields of research, the paper provides recommendations based on an updated overview of shortcomings, gains, and novel developments in relation to urban hydrological...

  17. Assessment of satellite rainfall products over the Andean plateau

    Science.gov (United States)

    Satgé, Frédéric; Bonnet, Marie-Paule; Gosset, Marielle; Molina, Jorge; Hernan Yuque Lima, Wilson; Pillco Zolá, Ramiro; Timouk, Franck; Garnier, Jérémie

    2016-01-01

    Nine satellite rainfall estimations (SREs) were evaluated for the first time over the South American Andean plateau watershed by comparison with rain gauge data acquired between 2005 and 2007. The comparisons were carried out at the annual, monthly and daily time steps. All SREs reproduce the salient pattern of the annual rain field, with a marked north-south gradient and a lighter east-west gradient. However, the intensity of the gradient differs among SREs: it is well marked in the Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis 3B42 (TMPA-3B42), Precipitation Estimation from remotely Sensed Information using Artificial Neural Networks (PERSIANN) and Global Satellite Mapping of Precipitation (GSMaP) products, and it is smoothed out in the Climate prediction center MORPHing (CMORPH) products. Another interesting difference among products is the contrast in rainfall amounts between the water surfaces (Lake Titicaca) and the surrounding land. Some products (TMPA-3B42, PERSIANN and GSMaP) show a contradictory rainfall deficit over Lake Titicaca, which may be due to the emissivity contrast between the lake and the surrounding lands and warm rain cloud processes. An analysis differentiating coastal Lake Titicaca from inland pixels confirmed this trend. The raw or Real Time (RT) products have strong biases over the study region. These biases are strongly positive for PERSIANN (above 90%), moderately positive for TMPA-3B42 (28%), strongly negative for CMORPH (- 42%) and moderately negative for GSMaP (- 18%). The biases are associated with a deformation of the rain rate frequency distribution: GSMaP underestimates the proportion of rainfall events for all rain rates; CMORPH overestimates the proportion of rain rates below 2 mm day- 1; and the other products tend to overestimate the proportion of moderate to high rain rates. These biases are greatly reduced by the gauge adjustment in the TMPA-3B42, PERSIANN and CMORPH products, whereas a

  18. Trends in rainfall and rainfall-related extremes in the east coast of peninsular Malaysia

    Science.gov (United States)

    Mayowa, Olaniya Olusegun; Pour, Sahar Hadi; Shahid, Shamsuddin; Mohsenipour, Morteza; Harun, Sobri Bin; Heryansyah, Arien; Ismail, Tarmizi

    2015-12-01

    The coastlines have been identified as the most vulnerable regions with respect to hydrological hazards as a result of climate change and variability. The east of peninsular Malaysia is not an exception for this, considering the evidence of heavy rainfall resulting in floods as an annual phenomenon and also water scarcity due to long dry spells in the region. This study examines recent trends in rainfall and rainfall- related extremes such as, maximum daily rainfall, number of rainy days, average rainfall intensity, heavy rainfall days, extreme rainfall days, and precipitation concentration index in the east coast of peninsular Malaysia. Recent 40 years (1971-2010) rainfall records from 54 stations along the east coast of peninsular Malaysia have been analyzed using the non-parametric Mann-Kendall test and the Sen's slope method. The Monte Carlo simulation technique has been used to determine the field significance of the regional trends. The results showed that there was a substantial increase in the annual rainfall as well as the rainfall during the monsoon period. Also, there was an increase in the number of heavy rainfall days during the past four decades.

  19. Addressing rainfall data selection uncertainty using connections between rainfall and streamflow.

    Science.gov (United States)

    Levy, Morgan C; Cohn, Avery; Lopes, Alan Vaz; Thompson, Sally E

    2017-03-16

    Studies of the hydroclimate at regional scales rely on spatial rainfall data products, derived from remotely-sensed (RS) and in-situ (IS, rain gauge) observations. Because regional rainfall cannot be directly measured, spatial data products are biased. These biases pose a source of uncertainty in environmental analyses, attributable to the choices made by data-users in selecting a representation of rainfall. We use the rainforest-savanna transition region in Brazil to show differences in the statistics describing rainfall across nine RS and interpolated-IS daily rainfall datasets covering the period of 1998-2013. These differences propagate into estimates of temporal trends in monthly rainfall and descriptive hydroclimate indices. Rainfall trends from different datasets are inconsistent at river basin scales, and the magnitude of index differences is comparable to the estimated bias in global climate model projections. To address this uncertainty, we evaluate the correspondence of different rainfall datasets with streamflow from 89 river basins. We demonstrate that direct empirical comparisons between rainfall and streamflow provide a method for evaluating rainfall dataset performance across multiple areal (basin) units. These results highlight the need for users of rainfall datasets to quantify this "data selection uncertainty" problem, and either justify data use choices, or report the uncertainty in derived results.

  20. FLASH-FLOOD MODELLING WITH ARTIFICIAL NEURAL NETWORKS USING RADAR RAINFALL ESTIMATES

    Directory of Open Access Journals (Sweden)

    Dinu Cristian

    2017-09-01

    Full Text Available The use of artificial neural networks (ANNs in modelling the hydrological processes has become a common approach in the last two decades, among side the traditional methods. In regard to the rainfall-runoff modelling, in both traditional and ANN models the use of ground rainfall measurements is prevalent, which can be challenging in areas with low rain gauging station density, especially in catchments where strong focused rainfall can generate flash-floods. The weather radar technology can prove to be a solution for such areas by providing rain estimates with good time and space resolution. This paper presents a comparison between different ANN setups using as input both ground and radar observations for modelling the rainfall-runoff process for Bahluet catchment, with focus on a flash-flood observed in the catchment.

  1. Modeling Rainfall-Runoff Response to Land Use and Land Cover Change in Rwanda (1990–2016

    Directory of Open Access Journals (Sweden)

    Fidele Karamage

    2017-02-01

    Full Text Available Stormwater runoff poses serious environmental problems and public health issues in Rwanda, a tropical country that is increasingly suffering from severe floods, landslides, soil erosion and water pollution. Using the WetSpa Extension model, this study assessed the changes in rainfall runoff depth in Rwanda from 1990 to 2016 in response to precipitation and land use changes. Our results show that Rwanda has experienced a significant conversion of natural forest and grassland to cropland and built-up areas. During the period 1990–2016, 7090.02 km2 (64.5% and 1715.26 km2 (32.1% of forest and grassland covers were lost, respectively, while the cropland and built-up areas increased by 135.3% (8503.75 km2 and 304.3% (355.02 km2, respectively. According to our estimates, the land use change effect resulted in a national mean runoff depth increase of 2.33 mm/year (0.38%. Although precipitation change affected the inter-annual fluctuation of runoff, the long-term trend of runoff was dominated by land use change. The top five districts that experienced the annual runoff depth increase (all >3.8 mm/year are Rubavu, Nyabihu, Ngororero, Gakenke, and Musanze. Their annual runoff depths increased at a rate of >3.8 mm/year during the past 27 years, due to severe deforestation (ranging from 62% to 85% and cropland expansion (ranging from 123% to 293%. These areas require high priority in runoff control using terracing in croplands and rainwater harvesting systems such as dam/reservoirs, percolation tanks, storage tanks, etc. The wet season runoff was three times higher than the dry season runoff in Rwanda; appropriate rainwater management and reservation could provide valuable irrigation water for the dry season or drought years (late rainfall onsets or early rainfall cessations. It was estimated that a reservation of 30.5% (3.99 km3 of the runoff in the wet season could meet the cropland irrigation water gap during the dry season in 2016.

  2. Assessing vegetation structure and ANPP dynamics in a grassland-shrubland Chihuahuan ecotone using NDVI-rainfall relationships

    Science.gov (United States)

    Moreno-de las Heras, M.; Diaz-Sierra, R.; Turnbull, L.; Wainwright, J.

    2015-01-01

    , and to (b) decompose the NDVI signal into partial primary production components for herbaceous vegetation and shrubs across the study site. We further apply remote-sensed annual net primary production (ANPP) estimations and landscape type classification to explore the influence of inter-annual variations in seasonal precipitation on the production of herbaceous and shrub vegetation. Our results suggest that changes in the amount and temporal pattern of precipitation comprising reductions in monsoonal summer rainfall and/or increases in winter precipitation may enhance the shrub-encroachment process in desert grasslands of the American Southwest.

  3. Constraining relationships between rainfall and landsliding with satellite derived rainfall measurements and landslide inventories.

    Science.gov (United States)

    Marc, Odin; Malet, Jean-Philippe; Stumpf, Andre; Gosset, Marielle

    2017-04-01

    In mountainous and hilly regions, landslides are an important source of damage and fatalities. Landsliding correlates with extreme rainfall events and may increase with climate change. Still, how precipitation drives landsliding at regional scales is poorly understood quantitatively in part because constraining simultaneously landsliding and rainfall across large areas is challenging. By combining optical images acquired from satellite observation platforms and rainfall measurements from satellite constellations we are building a database of landslide events caused by with single storm events. We present results from storm-induced landslides from Brazil, Taiwan, Micronesia, Central America, Europe and the USA. We present scaling laws between rainfall metrics derived by satellites (total rainfall, mean intensity, antecedent rainfall, ...) and statistical descriptors of landslide events (total area and volume, size distribution, mean runout, ...). Total rainfall seems to be the most important parameter driving non-linearly the increase in total landslide number, and area and volume. The maximum size of bedrock landslides correlates with the total number of landslides, and thus with total rainfall, within the limits of available topographic relief. In contrast, the power-law scaling exponent of the size distribution, controlling the relative abundance of small and large landslides, appears rather independent of the rainfall metrics (intensity, duration and total rainfall). These scaling laws seem to explain both the intra-storm pattern of landsliding, at the scale of satellite rainfall measurements ( 25kmx25km), and the different impacts observed for various storms. Where possible, we evaluate the limits of standard rainfall products (TRMM, GPM, GSMaP) by comparing them to in-situ data. Then we discuss how slope distribution and other geomorphic factors (lithology, soil presence,...) modulate these scaling laws. Such scaling laws at the basin scale and based only on a

  4. Topographic relationships for design rainfalls over Australia

    Science.gov (United States)

    Johnson, F.; Hutchinson, M. F.; The, C.; Beesley, C.; Green, J.

    2016-02-01

    Design rainfall statistics are the primary inputs used to assess flood risk across river catchments. These statistics normally take the form of Intensity-Duration-Frequency (IDF) curves that are derived from extreme value probability distributions fitted to observed daily, and sub-daily, rainfall data. The design rainfall relationships are often required for catchments where there are limited rainfall records, particularly catchments in remote areas with high topographic relief and hence some form of interpolation is required to provide estimates in these areas. This paper assesses the topographic dependence of rainfall extremes by using elevation-dependent thin plate smoothing splines to interpolate the mean annual maximum rainfall, for periods from one to seven days, across Australia. The analyses confirm the important impact of topography in explaining the spatial patterns of these extreme rainfall statistics. Continent-wide residual and cross validation statistics are used to demonstrate the 100-fold impact of elevation in relation to horizontal coordinates in explaining the spatial patterns, consistent with previous rainfall scaling studies and observational evidence. The impact of the complexity of the fitted spline surfaces, as defined by the number of knots, and the impact of applying variance stabilising transformations to the data, were also assessed. It was found that a relatively large number of 3570 knots, suitably chosen from 8619 gauge locations, was required to minimise the summary error statistics. Square root and log data transformations were found to deliver marginally superior continent-wide cross validation statistics, in comparison to applying no data transformation, but detailed assessments of residuals in complex high rainfall regions with high topographic relief showed that no data transformation gave superior performance in these regions. These results are consistent with the understanding that in areas with modest topographic relief, as

  5. On the dust load and rainfall relationship in South Asia: an analysis from CMIP5

    Science.gov (United States)

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

    2018-01-01

    This study is aimed at examining the consistency of the relationship between load of dust and rainfall simulated by different climate models and its implication for the Indian summer monsoon system. Monthly mean outputs of 12 climate models, obtained from the archive of the Coupled Model Intercomparison Project phase 5 (CMIP5) for the period 1951-2004, are analyzed to investigate the relationship between dust and rainfall. Comparative analysis of the model simulated precipitation with the India Meteorological Department (IMD) gridded rainfall, CRU TS3.21 and GPCP version 2.2 data sets show significant differences between the spatial patterns of JJAS rainfall as well as annual cycle of rainfall simulated by various models and observations. Similarly, significant inter-model differences are also noted in the simulation of load of dust, nevertheless it is further noted that most of the CMIP5 models are able to capture the major dust sources across the study region. Although the scatter plot analysis and the lead-lag pattern correlation between the dust load and the rainfall show strong relationship between the dust load over distant sources and the rainfall in the South Asian region in individual models, the temporal scale of this association indicates large differences amongst the models. Our results caution that it would be pre-mature to draw any robust conclusions on the time scale of the relationship between dust and the rainfall in the South Asian region based on either CMIP5 results or limited number of previous studies. Hence, we would like to emphasize upon the fact that any conclusions drawn on the relationship between the dust load and the South Asian rainfall using model simulation is highly dependent on the degree of complexity incorporated in those models such as the representation of aerosol life cycle, their interaction with clouds, precipitation and other components of the climate system.

  6. Remote sensing-based characterization of rainfall during atmospheric rivers over the central United States

    Science.gov (United States)

    Nayak, Munir A.; Villarini, Gabriele

    2018-01-01

    Atmospheric rivers (ARs) play a central role in the hydrology and hydroclimatology of the central United States. More than 25% of the annual rainfall is associated with ARs over much of this region, with many large flood events tied to their occurrence. Despite the relevance of these storms for flood hydrology and water budget, the characteristics of rainfall associated with ARs over the central United has not been investigated thus far. This study fills this major scientific gap by describing the rainfall during ARs over the central United States using five remote sensing-based precipitation products over a 12-year study period. The products we consider are: Stage IV, Tropical Rainfall Measuring Mission - Multi-satellite Precipitation Analysis (TMPA, both real-time and research version); Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks (PERSIANN); the CPC MORPHing Technique (CMORPH). As part of the study, we evaluate these products against a rain gauge-based dataset using both graphical- and metrics-based diagnostics. Based on our analyses, Stage IV is found to better reproduce the reference data. Hence, we use it for the characterization of rainfall in ARs. Most of the AR-rainfall is located in a narrow region within ∼150 km on both sides of the AR major axis. In this region, rainfall has a pronounced positive relationship with the magnitude of the water vapor transport. Moreover, we have also identified a consistent increase in rainfall intensity with duration (or persistence) of AR conditions. However, there is not a strong indication of diurnal variability in AR rainfall. These results can be directly used in developing flood protection strategies during ARs. Further, weather prediction agencies can benefit from the results of this study to achieve higher skill of resolving precipitation processes in their models.

  7. Quality‐control of an hourly rainfall dataset and climatology of extremes for the UK

    Science.gov (United States)

    Lewis, Elizabeth; Chan, Steven C.; Fowler, Hayley J.

    2016-01-01

    ABSTRACT Sub‐daily rainfall extremes may be associated with flash flooding, particularly in urban areas but, compared with extremes on daily timescales, have been relatively little studied in many regions. This paper describes a new, hourly rainfall dataset for the UK based on ∼1600 rain gauges from three different data sources. This includes tipping bucket rain gauge data from the UK Environment Agency (EA), which has been collected for operational purposes, principally flood forecasting. Significant problems in the use of such data for the analysis of extreme events include the recording of accumulated totals, high frequency bucket tips, rain gauge recording errors and the non‐operation of gauges. Given the prospect of an intensification of short‐duration rainfall in a warming climate, the identification of such errors is essential if sub‐daily datasets are to be used to better understand extreme events. We therefore first describe a series of procedures developed to quality control this new dataset. We then analyse ∼380 gauges with near‐complete hourly records for 1992–2011 and map the seasonal climatology of intense rainfall based on UK hourly extremes using annual maxima, n‐largest events and fixed threshold approaches. We find that the highest frequencies and intensities of hourly extreme rainfall occur during summer when the usual orographically defined pattern of extreme rainfall is replaced by a weaker, north–south pattern. A strong diurnal cycle in hourly extremes, peaking in late afternoon to early evening, is also identified in summer and, for some areas, in spring. This likely reflects the different mechanisms that generate sub‐daily rainfall, with convection dominating during summer. The resulting quality‐controlled hourly rainfall dataset will provide considerable value in several contexts, including the development of standard, globally applicable quality‐control procedures for sub‐daily data, the validation of the new

  8. Spatial and temporal distribution of rainfall and drought characteristics across the Pearl River basin.

    Science.gov (United States)

    Deng, Shulin; Chen, Tan; Yang, Ni; Qu, Lean; Li, Manchun; Chen, Dong

    2018-04-01

    Understanding rainfall trends as well as drought characteristics plays a key role in watershed development and management. In this study, the spatial and temporal characteristics of rainfall and drought based on temperature and precipitation data observed in 48 meteorological stations from 1959 to 2012 across the Pearl River Basin in China were analyzed. The possible influence of El Nino-Southern Oscillation (ENSO) and El Nino Modoki (ENSO_M) events on seasonal drought based on the Standardized Precipitation-evapotranspiration Index (SPEI) were also investigated. The results show that annual and seasonal rainfall decreased slightly in most areas, annual and seasonal daily precipitation concentration decreased in a few areas, monthly rainfall had an irregular distribution but with no significant trend detected, and rainfall seasonality increased in most areas. Drought tended to worsen during recent years, especially in the upper reaches, and seasonal drought also tended to become serious or occurred frequently across the Pearl River Basin. The drought patterns are not only related to the decreasing trends in rainfall but also to changes in the daily rainfall concentration, monthly rainfall heterogeneity, and rainfall seasonality. Both ENSO and ENSO_M events had an influence on summer drought in the middle-upper reaches. The ENSO events dominated the patterns of autumn drought in the Pearl River Delta, and the ENSO_M events strongly affected the changing patterns of autumn drought in the middle-upper reaches and northern parts of the middle-lower reaches. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Heavy rainfall equations for Santa Catarina, Brazil

    Directory of Open Access Journals (Sweden)

    Álvaro José Back

    2011-12-01

    Full Text Available Knowledge of intensity-duration-frequency (IDF relationships of rainfall events is extremely important to determine the dimensions of surface drainage structures and soil erosion control. The purpose of this study was to obtain IDF equations of 13 rain gauge stations in the state of Santa Catarina in Brazil: Chapecó, Urussanga, Campos Novos, Florianópolis, Lages, Caçador, Itajaí, Itá, Ponte Serrada, Porto União, Videira, Laguna and São Joaquim. The daily rainfall data charts of each station were digitized and then the annual maximum rainfall series were determined for durations ranging from 5 to 1440 min. Based on these, with the Gumbel-Chow distribution, the maximum rainfall was estimated for durations ranging from 5 min to 24 h, considering return periods of 2, 5, 10, 20, 25, 50, and 100 years,. Data agreement with the Gumbel-Chow model was verified by the Kolmogorov-Smirnov test, at 5 % significance level. For each rain gauge station, two IDF equations of rainfall events were adjusted, one for durations from 5 to 120 min and the other from 120 to 1440 min. The results show a high variability in maximum intensity of rainfall events among the studied stations. Highest values of coefficients of variation in the annual maximum series of rainfall were observed for durations of over 600 min at the stations of the coastal region of Santa Catarina.

  10. The Effects of Amazon Deforestation on Rainfall

    Science.gov (United States)

    Starr, David OC. (Technical Monitor); Negri, Andrew J.; Adler, Robert F.; Surratt, Jason

    2002-01-01

    This study begins with the hypothesis that heavily deforested regions will experience increased surface heating, leading to local circulations that will ultimately enhance the rainfall, or at least, change the pattern of diurnal evolution of rainfall. This would be an important finding because several modeling studies have concluded that widespread deforestation would lead to decreased rainfall. Towards that end rain estimates from a combined GOES infrared/TRMM microwave technique were analyzed with respect to percent forest cover from Landsat data (courtesy of TRFIC at Michigan State University) and GOES visible channel data over a deforested area in Rondonia (southwest Brazil). Five 1" x 1" areas of varying forest cover were examined during the onset of the wet season in Amazonia (Aug-Sept), when the effects of the surface would not be dominated by large-scale synoptic weather patterns. Preliminary results revealed that: maximum rainfall fell in most deforested area; heavily forested areas received the least rainfall; cumulus cloud development initiated at borders; the amplitude of the diurnal cycle of precipitation was a function of th surface cover. Further work will be presented detailing effects of land surface cover on the GOES infrared-measured surface heating, GOES visible observed cumulus development, thunderstorm initiation based on the location of temperature minima in the infrared data, and estimated rainfall and its diurnal cycle from a combined GOES/TRMM technique. Rainfall estimates derived from non-geosynchronous microwave observations (i.e. Goddard Profiling Algorithm, GPROF) will also be examined.

  11. Rainfall variability in Bulgaria and its relation with NAO

    International Nuclear Information System (INIS)

    Nikolova, Nina

    2004-01-01

    The variation of climate exerts strong influence on the productivity of agriculture and on the various aspects of human activity. Many research programs at local, regional and global levels show as a main task the action to reduce, avoid, and better understand the risk associated with the climate change. The precipitation determines the availability of drinking water and the level of the soil moisture. The paper is intended to provide information about seasonal and geographical variation of precipitation in Bulgaria and its relation with North Atlantic Oscillation (NAO). A Statistical test is applied to test the homogeneity and distribution of the initial data. In order to characterize the long-term and more recent trends linear regression equations are calculated. Correlation analysis is used to define the relationship between precipitation and global circulation mechanisms. The main question of the research is: whether the observed trend in Bulgaria corresponds to the global climate change? The tasks are: - Investigation of short-term and long-term rainfall variability - Assessment of statistical significance of the linear trend - Establishing the relationship between rainfall variability and NAO - what is the influence of the NAO on rainfall variability in Bulgaria In order to characterize the long-term and more recent trends linear regression equations were calculated individually for each station for two periods 1931-2000 and 1961-2000. The trend is negative or close to 0 for the first period. For the second period it is a negative with the values for January to April between -0.2 and -0.7. Correlation analysis is applied to define the relationship between rainfall variability in Bulgaria and NAO. The relationship is stronger for more recent period 1960-2000. The correlation coefficients are negative. Statistical significant coefficients are found for January, February and March. The paper gives information about climate change in regional scale. The results

  12. Testing strong interaction theories

    International Nuclear Information System (INIS)

    Ellis, J.

    1979-01-01

    The author discusses possible tests of the current theories of the strong interaction, in particular, quantum chromodynamics. High energy e + e - interactions should provide an excellent means of studying the strong force. (W.D.L.)

  13. Rainfall Variability, Drought Characterization, and Efficacy of Rainfall Data Reconstruction: Case of Eastern Kenya

    Directory of Open Access Journals (Sweden)

    M. Oscar Kisaka

    2015-01-01

    Full Text Available This study examined the extent of seasonal rainfall variability, drought occurrence, and the efficacy of interpolation techniques in eastern Kenya. Analyses of rainfall variability utilized rainfall anomaly index, coefficients of variance, and probability analyses. Spline, Kriging, and inverse distance weighting interpolation techniques were assessed using daily rainfall data and digital elevation model using ArcGIS. Validation of these interpolation methods was evaluated by comparing the modelled/generated rainfall values and the observed daily rainfall data using root mean square errors and mean absolute errors statistics. Results showed 90% chance of below cropping threshold rainfall (500 mm exceeding 258.1 mm during short rains in Embu for one year return period. Rainfall variability was found to be high in seasonal amounts (CV = 0.56, 0.47, and 0.59 and in number of rainy days (CV = 0.88, 0.49, and 0.53 in Machang’a, Kiritiri, and Kindaruma, respectively. Monthly rainfall variability was found to be equally high during April and November (CV = 0.48, 0.49, and 0.76 with high probabilities (0.67 of droughts exceeding 15 days in Machang’a and Kindaruma. Dry-spell probabilities within growing months were high, (91%, 93%, 81%, and 60% in Kiambere, Kindaruma, Machang’a, and Embu, respectively. Kriging interpolation method emerged as the most appropriate geostatistical interpolation technique suitable for spatial rainfall maps generation for the study region.

  14. Effects of experimental rainfall manipulations on Chihuahuan Desert grassland and shrubland plant communities.

    Science.gov (United States)

    Báez, Selene; Collins, Scott L; Pockman, William T; Johnson, Jennifer E; Small, Eric E

    2013-08-01

    Aridland ecosystems are predicted to be responsive to both increases and decreases in precipitation. In addition, chronic droughts may contribute to encroachment of native C3 shrubs into C4-dominated grasslands. We conducted a long-term rainfall manipulation experiment in native grassland, shrubland and the grass-shrub ecotone in the northern Chihuahuan Desert, USA. We evaluated the effects of 5 years of experimental drought and 4 years of water addition on plant community structure and dynamics. We assessed the effects of altered rainfall regimes on the abundance of dominant species as well as on species richness and subdominant grasses, forbs and shrubs. Nonmetric multidimensional scaling and MANOVA were used to quantify changes in species composition in response to chronic addition or reduction of rainfall. We found that drought consistently and strongly decreased cover of Bouteloua eriopoda, the dominant C4 grass in this system, whereas water addition slightly increased cover, with little variation between years. In contrast, neither chronic drought nor increased rainfall had consistent effects on the cover of Larrea tridentata, the dominant C3 shrub. Species richness declined in shrub-dominated vegetation in response to drought whereas richness increased or was unaffected by water addition or drought in mixed- and grass-dominated vegetation. Cover of subdominant shrubs, grasses and forbs changed significantly over time, primarily in response to interannual rainfall variability more so than to our experimental rainfall treatments. Nevertheless, drought and water addition shifted the species composition of plant communities in all three vegetation types. Overall, we found that B. eriopoda responded strongly to drought and less so to irrigation, whereas L. tridentata showed limited response to either treatment. The strong decline in grass cover and the resistance of shrub cover to rainfall reduction suggest that chronic drought may be a key factor promoting shrub

  15. Shallow and deep landslides induced by rainfall in the Lisbon region (Portugal: assessment of relationships with the North Atlantic Oscillation

    Directory of Open Access Journals (Sweden)

    J. L. Zêzere

    2005-01-01

    Full Text Available The aim of this study is to assess the impact of the North Atlantic Oscillation (NAO on both the winter precipitation and the temporal occurrence of different landslide types in Portugal. The analysis is applied to five sample areas located just north of Lisbon, the capital of Portugal. These sites are particularly relevant because actual dates of most of the recent landslide events are known but also because the landslides occurred in a suburban area with growing urbanization pressure. Results show that the large inter-annual variability of winter precipitation observed in western Iberia, i.e. Portugal and parts of Spain, is largely modulated by the NAO mode. In particular, precipitation falling in Portugal between November and March presents a correlation coefficient of R=–0.66 with the NAO index. Precipitation distribution for the reference rain gauge in the study area reveals that the probability of a wet month to occur is much higher for low NAO index composites than for the corresponding high NAO index composite. It is shown that this control, exerted by NAO on the precipitation regime, is related to corresponding changes in the associated activity of North-Atlantic storm tracks that affect the western Iberia. Landslide activity in the study area is related to both intense, short duration precipitation events (1–15 days and long-lasting rainfall episodes (1–3 months. The former events trigger shallow translational slides while the later episodes are usually associated with deeper and larger slope movements. This second group of landslides is shown to be statistically associated with the 3-month average of the NAO index.

  16. Enhancement of seasonal prediction of East Asian summer rainfall related to the western tropical Pacific convection

    Science.gov (United States)

    Lee, D. Y.; Ahn, J. B.; Yoo, J. H.

    2014-12-01

    The prediction skills of climate model simulations in the western tropical Pacific (WTP) and East Asian region are assessed using the retrospective forecasts of seven state-of-the-art coupled models and their multi-model ensemble (MME) for boreal summers (June-August) during the period 1983-2005, along with corresponding observed and reanalyzed data. The prediction of summer rainfall anomalies in East Asia is difficult, while the WTP has a strong correlation between model prediction and observation. We focus on developing a new approach to further enhance the seasonal prediction skill for summer rainfall in East Asia and investigate the influence of convective activity in the WTP on East Asian summer rainfall. By analyzing the characteristics of the WTP convection, two distinct patterns associated with El Niño-Southern Oscillation (ENSO) developing and decaying modes are identified. Based on the multiple linear regression method, the East Asia Rainfall Index (EARI) is developed by using the interannual variability of the normalized Maritime continent-WTP indices (MPIs), as potentially useful predictors for rainfall prediction over East Asia, obtained from the above two main patterns. For East Asian summer rainfall, the EARI has superior performance to the East Asia summer monsoon index (EASMI) or each MP index (MPI). Therefore, the regressed rainfall from EARI also shows a strong relationship with the observed East Asian summer rainfall pattern. In addition, we evaluate the prediction skill of the East Asia reconstructed rainfall obtained by statistical-empirical approach using the cross-validated EARI from the individual models and their MME. The results show that the rainfalls reconstructed from simulations capture the general features of observed precipitation in East Asia quite well. This study convincingly demonstrates that rainfall prediction skill is considerably improved by using the statistical-empirical method compared to the dynamical models

  17. Analysis of Rainfall Characteristicsfor Flood Estimation in Way Awi Watershed

    Directory of Open Access Journals (Sweden)

    Kusumastuti D.I.

    2016-03-01

    Full Text Available This study investigates rainfall intensity distribution in Way Awi watershed located in Bandar Lampung, and how their impacts on flood peak and flood hydrographs. Hourly rainfall data is examined to obtain design rainfall intensity and rainfall intensity distribution at rainfall duration from three to eight hours. Rainfall-runoff model, i.e. Rational method is used to calculate flood peak while unit hydrograph method is used to develop flood hydrograph. This study shows that in Way Awi watershed 88.3% to 96.4% of 24-hour rain occurs in three to eight hour durations. In addition, rainfall with three hour duration generates the highest flood peak, followed by four hour duration rainfall. When rainfall duration and design rainfall intensity are the same but rainfall intensity distribution is different, generated flood hydrograph may have different flood peak magnitude and timing. Result of this study is useful for flood analysis and mitigation in Way Awi watershed.

  18. Weather radar rainfall data in urban hydrology

    DEFF Research Database (Denmark)

    Thorndahl, Søren; Einfalt, Thomas; Willems, Patrick

    2017-01-01

    Application of weather radar data in urban hydrological applications has evolved significantly during the past decade as an alternative to traditional rainfall observations with rain gauges. Advances in radar hardware, data processing, numerical models, and emerging fields within urban hydrology...

  19. Properties of Extreme Point Rainfall I

    DEFF Research Database (Denmark)

    Harremoës, Poul; Mikkelsen, Peter Steen

    1995-01-01

    Extreme rainfall has been recorded by the larger municipalities in Denmark since 1933. National intensity-duration-frequency curves were produced on this basis for engineering application in the whole of Denmark. In 1979, on the initiative of The Danish Water Pollution Control Committee under...... of the engineering application of rainfall data for design. The article describes the engineering purpose and design of sewer systems, the initial data treatment, the results from the first statistical analysis and the consequence for engineering application....

  20. Weather radar rainfall data in urban hydrology

    Science.gov (United States)

    Thorndahl, Søren; Einfalt, Thomas; Willems, Patrick; Ellerbæk Nielsen, Jesper; ten Veldhuis, Marie-Claire; Arnbjerg-Nielsen, Karsten; Rasmussen, Michael R.; Molnar, Peter

    2017-03-01

    Application of weather radar data in urban hydrological applications has evolved significantly during the past decade as an alternative to traditional rainfall observations with rain gauges. Advances in radar hardware, data processing, numerical models, and emerging fields within urban hydrology necessitate an updated review of the state of the art in such radar rainfall data and applications. Three key areas with significant advances over the past decade have been identified: (1) temporal and spatial resolution of rainfall data required for different types of hydrological applications, (2) rainfall estimation, radar data adjustment and data quality, and (3) nowcasting of radar rainfall and real-time applications. Based on these three fields of research, the paper provides recommendations based on an updated overview of shortcomings, gains, and novel developments in relation to urban hydrological applications. The paper also reviews how the focus in urban hydrology research has shifted over the last decade to fields such as climate change impacts, resilience of urban areas to hydrological extremes, and online prediction/warning systems. It is discussed how radar rainfall data can add value to the aforementioned emerging fields in current and future applications, but also to the analysis of integrated water systems.

  1. Association of Taiwan’s Rainfall Patterns with Large-Scale Oceanic and Atmospheric Phenomena

    Directory of Open Access Journals (Sweden)

    Yi-Chun Kuo

    2016-01-01

    Full Text Available A 50-year (1960–2009 monthly rainfall gridded dataset produced by the Taiwan Climate Change Projection and Information Platform Project was presented in this study. The gridded data (5 × 5 km displayed influence of topography on spatial variability of rainfall, and the results of the empirical orthogonal functions (EOFs analysis revealed the patterns associated with the large-scale sea surface temperature variability over Pacific. The first mode (65% revealed the annual peaks of large rainfall in the southwestern mountainous area, which is associated with southwest monsoons and typhoons during summertime. The second temporal EOF mode (16% revealed the rainfall variance associated with the monsoon and its interaction with the slopes of the mountain range. This pattern is the major contributor to spatial variance of rainfall in Taiwan, as indicated by the first mode (40% of spatial variance EOF analysis. The second temporal EOF mode correlated with the El Niño Southern Oscillation (ENSO. In particular, during the autumn of the La Niña years following the strong El Niño years, the time-varying amplitude was substantially greater than that of normal years. The third temporal EOF mode (7% revealed a north-south out-of-phase rainfall pattern, the slowly evolving variations of which were in phase with the Pacific Decadal Oscillation. Because of Taiwan’s geographic location and the effect of local terrestrial structures, climate variability related to ENSO differed markedly from other regions in East Asia.

  2. Soil degradation level under particular annual rainfall at Jenawi District– Karanganyar, Indonesia

    Science.gov (United States)

    Herawati, A.; Suntoro; Widijanto, H.; Pusponegoro, I.; Sutopo, N. R.; Mujiyo

    2018-03-01

    The study of the climatic elements such as rainfall is vital for the sustainable development of agriculture at a region. The aims of the study were to evaluate the soil degradation based on the annual rainfall and to determine the key factors which responsible for the soil degradation at in Jenawi Sub-District. The mapping of soil degradation potency is an identification of initial soil condition to discover the potential of the land degradation. The mapping was done by overlaying the map of soil, slope, rainfall and land use with the standard procedures to obtain the value and status of Soil Degradation Potency (SDP). The result showed that SDP in Jenawi District categorized in very low (SDP I) 0.00 ha (0.00%); low (SDP II) 109.01 ha (2.57%); moderate (SDP III) 1,935.92 ha (45.63%); high (SDP IV) 1,959.54 ha (46.19%) and very high (SDP V) 238.08 ha (5.61%). The rainfall is the factor which has the strong correlation with the SDP (r = 0.65, P < 0.01, n = 306). The changes in the rainfall as the impact of climate change need to be anticipated to minimize soil degradation. The result can be adapted to the rainfall changes in various ways based on local soil-land characteristics.

  3. Are estimates of anthropogenic and natural influences on Australia's extreme 2010-2012 rainfall model-dependent?

    Science.gov (United States)

    Lewis, Sophie C.; Karoly, David J.

    2015-08-01

    Australia experienced much above average rainfall in association with strong, extended La Niña conditions during 2010-2012. Was the heavy Australian rainfall influenced by La Niña conditions and/or anthropogenic greenhouse gases? We investigate the relative contributions of anthropogenic climate change and natural climatic variability to the likelihood of heavy Australian rainfall using three distinct model datasets. Area-average rainfall anomalies for model simulations with natural forcings only were compared to simulations with both anthropogenic and natural forcings using 16 models participating in the Coupled Model Intercomparison Project Phase 5. Using fraction of attributable risk to compare the likelihood of unusual rainfall between the parallel experiments, we find attribution statements are uncertain, with FAR values sensitive to the attribution parameters considered, including thresholds, regions and seasons. When heavy rainfall probabilities were next investigated in ensembles of two atmospheric general circulation models, run with and without anthropogenically-induced sea surface temperature changes, results were model-dependent. Overall, the attribution of seasonal-scale heavy Australia rainfall to a particular cause is likely more complicated than for temperature extremes. As estimates of the greenhouse gas attributable change in rainfall risk may depend on the model datasets considered, it is also useful to consider model outputs from several datasets and using various estimates of counterfactual surface conditions to establish robust attribution statements for extreme rainfall events. In contrast, comparing the likelihoods of heavy rainfall during simulated La Niña years with El Niño/neutral years reveals a substantial La Niña influence on Australian rainfall during 2010-2012 that is robust to changes in the attribution framework.

  4. Location-Based Rainfall Nowcasting Service for Public

    Science.gov (United States)

    Woo, Wang-chun

    2013-04-01

    The Hong Kong Observatory has developed the "Short-range Warning of Intense Rainstorms in Localized Systems (SWIRLS)", a radar-based rainfall nowcasting system originally to support forecasters in rainstorm warning and severe weather forecasting such as hail, lightning and strong wind gusts in Hong Kong. The system has since been extended to provide rainfall nowcast service direct for the public in recent years. Following the launch of "Rainfall Nowcast for the Pearl River Delta Region" service provided via a Geographical Information System (GIS) platform in 2008, a location-based rainfall nowcast service served through "MyObservatory", a smartphone app for iOS and Android developed by the Observatory, debuted in September 2012. The new service takes advantage of the capability of smartphones to detect own locations and utilizes the quantitative precipitation forecast (QPF) from SWIRLS to provide location-based rainfall nowcast to the public. The conversion of radar reflectivity data (at 2 or 3 km above ground) to rainfall in SWIRLS is based on the Z-R relationship (Z=aRb) with dynamical calibration of the coefficients a and b determined using real-time rain gauge data. Adopting the "Multi-scale Optical-flow by Variational Analysis (MOVA)" scheme to track the movement of radar echoes and Semi-Lagrangian Advection (SLA) scheme to extrapolate their movement, the system is capable of producing QPF for the next six hours in a grid of 480 x 480 that covers a domain of 256 km x 256 km once every 6 minutes. Referencing the closest point in a resampled 2-km grid over the territory of Hong Kong, a prediction as to whether there will be rainfall exceeding 0.5 mm in every 30 minute intervals for the next two hours at users' own or designated locations are made available to the users in both textual and graphical format. For those users who have opted to receive notifications, a message would pop up on the user's phone whenever rain is predicted in the next two hours in a user

  5. Conditions for the Occurrence of Slaking and Other Disaggregation Processes under Rainfall

    Directory of Open Access Journals (Sweden)

    Frédéric Darboux

    2016-07-01

    Full Text Available Under rainfall conditions, aggregates may suffer breakdown by different mechanisms. Slaking is a very efficient breakdown mechanism. However, its occurrence under rainfall conditions has not been demonstrated. Therefore, the aim of this study was to evaluate the occurrence of slaking under rain. Two soils with silt loam (SL and clay loam (CL textures were analyzed. Two classes of aggregates were utilized: 1–3 mm and 3–5 mm. The aggregates were submitted to stability tests and to high intensity (90 mm·h−1 and low intensity (28 mm·h−1 rainfalls, and different kinetic energy impacts (large and small raindrops using a rainfall simulator. The fragment size distributions were determined both after the stability tests and rainfall simulations, with the calculation of the mean weighted diameter (MWD. After the stability tests the SL presented smaller MWDs for all stability tests when compared to the CL. In both soils the lowest MWD was obtained using the fast wetting test, showing they were sensitive to slaking. For both soils and the two aggregate classes evaluated, the MWDs were recorded from the early beginning of the rainfall event under the four rainfall conditions. The occurrence of slaking in the evaluated soils was not verified under the simulated rainfall conditions studied. The early disaggregation was strongly related to the cumulative kinetic energy, advocating for the occurrence of mechanical breakdown. Because slaking requires a very high wetting rate on initially dry aggregates, it seems unlikely to occur under field conditions, except perhaps for furrow irrigation.

  6. Reconstruction of rainfall events responsible for landslides using an algorithm

    Science.gov (United States)

    Melillo, Massimo; Brunetti, Maria Teresa; Gariano, Stefano Luigi; Guzzetti, Fausto; Peruccacci, Silvia

    2014-05-01

    In Italy, intense or prolonged rainfall is the primary trigger of damaging landslides. The identification of the rainfall conditions responsible for the initiation of landslides is a crucial issue and may contribute to reduce landslide risk. Objective criteria for the identification of rainfall conditions that could initiate slope failures are still lacking or ambiguous. The reconstruction of rainfall events able to trigger past landslides is usually performed manually by expert investigators. Here, we propose an algorithm that reconstructs automatically rainfall events from a series of hourly rainfall data. The automatic reconstruction reproduces the actions performed by an expert investigator that adopts empirical rules to define rainfall conditions that presumably initiated the documented landslides. The algorithm, which is implemented in R (http://www.r-project.org), performs three actions on the data series: (i) removes isolated events with negligible amount of rainfall and random noise generated by the rain gauge; (ii) aggregates rainfall measurements in order to obtain a sequence of distinct rainfall events; (iii) identifies single or multiple rainfall conditions responsible for the slope failures. In particular, the algorithm calculates the duration, D, and the cumulated rainfall, E, for rainfall events, and for rainfall conditions that have resulted in landslides. A set of input parameters allows the automatic reconstruction of rainfall events in different physical settings and climatic conditions. We tested the algorithm using rainfall and landslide information available to us for Sicily, Southern Italy, in the period between January 2002 and December 2012. The algorithm reconstructed 13,537 rainfall events and 343 rainfall conditions as possible triggers of the 163 documented landslides. Most (87.7%) of the rainfall conditions obtained manually were reconstructed accurately. Use of the algorithm shall contribute to an objective and reproducible

  7. Heavy daily-rainfall characteristics over the Gauteng Province

    African Journals Online (AJOL)

    2009-02-09

    Feb 9, 2009 ... A significant rainfall event is defined when the average rainfall exceeds 10 mm, a heavy rainfall event when the average rainfall ..... in October (72 mm) even though the number of days with some rain was very similar (15 to 17 d). The standard deviation of the average monthly rain- fall in March was 54 mm ...

  8. Rainfall characteristics and thresholds for periglacial debris flows in ...

    Indian Academy of Sciences (India)

    The Parlung Zangbo Basin in the southeastern Tibet Plateau is affected by the summer monsoon from the Indian Ocean, which produces large rainfall gradients in the basin. Rainfall data during 2012–2015 from five new meteorological stations are used to analyse the rainfall characteristics. The daily rainfall, rainfallduration ...

  9. Temporal and spatial variability of rainfall distribution and ...

    African Journals Online (AJOL)

    Rainfall and evapotranspiration are the two major climatic factors affecting agricultural production. This study examined the extent and nature of rainfall variability from measured data while estimation of evapotranspiration was made from recorded weather data. Analysis of rainfall variability is made by the rainfall anomaly ...

  10. Satellite-based estimation of rainfall erosivity for Africa

    NARCIS (Netherlands)

    Vrieling, A.; Sterk, G.; Jong, S.M. de

    2010-01-01

    Rainfall erosivity is a measure for the erosive force of rainfall. Rainfall kinetic energy determines the erosivity and is in turn greatly dependent on rainfall intensity. Attempts for its large-scale mapping are rare. Most are based on interpolation of erosivity values derived from rain gauge

  11. Changes in the interannual SST-forced signals on West African rainfall. AGCM intercomparison

    Energy Technology Data Exchange (ETDEWEB)

    Mohino, Elsa [LOCEAN/IPSL, Universite Pierre et Marie Curie, Paris Cedex 05 (France); Universidad de Sevilla, Sevilla (Spain); Rodriguez-Fonseca, Belen [Universidad Complutense de Madrid, Dpto. Geofisica y Meteorologia, Madrid (Spain); Instituto de Geociencias (CSIC-UCM), Madrid (Spain); Losada, Teresa [Universidad Complutense de Madrid, Dpto. Geofisica y Meteorologia, Madrid (Spain); Gervois, Sebastien [LOCEAN/IPSL, Universite Pierre et Marie Curie, Paris Cedex 05 (France); Janicot, Serge [LOCEAN/IPSL, IRD, Universite Pierre et Marie Curie, Paris (France); Bader, Juergen [Bjerknes Centre for Climate Research, Bergen (Norway); Ruti, Paolo [Progetto Speciale Clima Globale, Ente Nazionale per le Nuove Tecnologie, l' Energia e l' Ambiente, Rome (Italy); Chauvin, Fabrice [GAME/CNRM, Meteo-France/CNRS, Toulouse (France)

    2011-11-15

    Rainfall over West Africa shows strong interannual variability related to changes in Sea Surface Temperature (SST). Nevertheless, this relationship seem to be non-stationary. A particular turning point is the decade of the 1970s, which witnessed a number of changes in the climatic system, including the climate shift of the late 1970s. The first aim of this study is to explore the change in the interannual variability of West African rainfall after this shift. The analysis indicates that the dipolar features of the rainfall variability over this region, related to changes in the Atlantic SST, disappear after this period. Also, the Pacific SST variability has a higher correlation with Guinean rainfall in the recent period. The results suggest that the current relationship between the Atlantic and Pacific El Nino phenomena is the principal responsible for these changes. A fundamental goal of climate research is the development of models simulating a realistic current climate. For this reason, the second aim of this work is to test the performance of Atmospheric General Circulation models in simulating rainfall variability over West Africa. The models have been run with observed SSTs for the common period 1957-1998 as part of an intercomparison exercise. The results show that the models are able to reproduce Guinean interannual variability, which is strongly related to SST variability in the Equatorial Atlantic. Nevertheless, problems in the simulation of the Sahelian interannual variability appear: not all models are able to reproduce the observed negative link between rainfall over the Sahel and El Nino-like anomalies in the Pacific, neither the positive correlation between Mediterranean SSTs and Sahelian rainfall. (orig.)

  12. Trends analysis of rainfall and rainfall extremes in Sarawak, Malaysia using modified Mann-Kendall test

    Science.gov (United States)

    Sa'adi, Zulfaqar; Shahid, Shamsuddin; Ismail, Tarmizi; Chung, Eun-Sung; Wang, Xiao-Jun

    2017-11-01

    This study assesses the spatial pattern of changes in rainfall extremes of Sarawak in recent years (1980-2014). The Mann-Kendall (MK) test along with modified Mann-Kendall (m-MK) test, which can discriminate multi-scale variability of unidirectional trend, was used to analyze the changes at 31 stations. Taking account of the scaling effect through eliminating the effect of autocorrelation, m-MK was employed to discriminate multi-scale variability of the unidirectional trends of the annual rainfall in Sarawak. It can confirm the significance of the MK test. The annual rainfall trend from MK test showed significant changes at 95% confidence level at five stations. The seasonal trends from MK test indicate an increasing rate of rainfall during the Northeast monsoon and a decreasing trend during the Southwest monsoon in some region of Sarawak. However, the m-MK test detected an increasing trend in annual rainfall only at one station and no significant trend in seasonal rainfall at any stations. The significant increasing trends of the 1-h maximum rainfall from the MK test are detected mainly at the stations located in the urban area giving concern to the occurrence of the flash flood. On the other hand, the m-MK test detected no significant trend in 1- and 3-h maximum rainfalls at any location. On the contrary, it detected significant trends in 6- and 72-h maximum rainfalls at a station located in the Lower Rajang basin area which is an extensive low-lying agricultural area and prone to stagnant flood. These results indicate that the trends in rainfall and rainfall extremes reported in Malaysia and surrounding region should be verified with m-MK test as most of the trends may result from scaling effect.

  13. How effective is the new generation of GPM satellite precipitation in characterizing the rainfall variability over Malaysia?

    Science.gov (United States)

    Mahmud, Mohd Rizaludin; Hashim, Mazlan; Reba, Mohd Nadzri Mohd

    2017-08-01

    We investigated the potential of the new generation of satellite precipitation product from the Global Precipitation Mission (GPM) to characterize the rainfall in Malaysia. Most satellite precipitation products have limited ability to precisely characterize the high dynamic rainfall variation that occurred at both time and scale in this humid tropical region due to the coarse grid size to meet the physical condition of the smaller land size, sub-continent and islands. Prior to the status quo, an improved satellite precipitation was required to accurately measure the rainfall and its distribution. Subsequently, the newly released of GPM precipitation product at half-hourly and 0.1° resolution served an opportunity to anticipate the aforementioned conflict. Nevertheless, related evidence was not found and therefore, this study made an initiative to fill the gap. A total of 843 rain gauges over east (Borneo) and west Malaysia (Peninsular) were used to evaluate the rainfall the GPM rainfall data. The assessment covered all critical rainy seasons which associated with Asian Monsoon including northeast (Nov. - Feb.), southwest (May - Aug.) and their subsequent inter-monsoon period (Mar. - Apr. & Sep. - Oct.). The ability of GPM to provide quantitative rainfall estimates and qualitative spatial rainfall patterns were analysed. Our results showed that the GPM had good capacity to depict the spatial rainfall patterns in less heterogeneous rainfall patterns (Spearman's correlation, 0.591 to 0.891) compared to the clustered one (r = 0.368 to 0.721). Rainfall intensity and spatial heterogeneity that is largely driven by seasonal monsoon has significant influence on GPM ability to resolve local rainfall patterns. In quantitative rainfall estimation, large errors can be primarily associated with the rainfall intensity increment. 77% of the error variation can be explained through rainfall intensity particularly the high intensity (> 35 mm d-1). A strong relationship between GPM

  14. Ensemble climate projections of mean and extreme rainfall over Vietnam

    Science.gov (United States)

    Raghavan, S. V.; Vu, M. T.; Liong, S. Y.

    2017-01-01

    A systematic ensemble high resolution climate modelling study over Vietnam has been performed using the PRECIS model developed by the Hadley Center in UK. A 5 member subset of the 17-member Perturbed Physics Ensembles (PPE) of the Quantifying Uncertainty in Model Predictions (QUMP) project were simulated and analyzed. The PRECIS model simulations were conducted at a horizontal resolution of 25 km for the baseline period 1961-1990 and a future climate period 2061-2090 under scenario A1B. The results of model simulations show that the model was able to reproduce the mean state of climate over Vietnam when compared to observations. The annual cycles and seasonal averages of precipitation over different sub-regions of Vietnam show the ability of the model in also reproducing the observed peak and magnitude of monthly rainfall. The climate extremes of precipitation were also fairly well captured. Projections of future climate show both increases and decreases in the mean climate over different regions of Vietnam. The analyses of future extreme rainfall using the STARDEX precipitation indices show an increase in 90th percentile precipitation (P90p) over the northern provinces (15-25%) and central highland (5-10%) and over southern Vietnam (up to 5%). The total number of wet days (Prcp) indicates a decrease of about 5-10% all over Vietnam. Consequently, an increase in the wet day rainfall intensity (SDII), is likely inferring that the projected rainfall would be much more severe and intense which have the potential to cause flooding in some regions. Risks due to extreme drought also exist in other regions where the number of wet days decreases. In addition, the maximum 5 day consecutive rainfall (R5d) increases by 20-25% over northern Vietnam but decreases in a similar range over the central and southern Vietnam. These results have strong implications for the management water resources, agriculture, bio diversity and economy and serve as some useful findings to be

  15. Changes in rainfall seasonality in the tropics

    Science.gov (United States)

    Feng, X.; Porporato, A. M.; Rodriguez-Iturbe, I.

    2012-12-01

    Climate change has altered not only the overall magnitude of rainfall but also their seasonal distribution and interannual variability across the world. Such changes in the rainfall regimes will be most keenly felt in arid and semiarid regions, where the availability and timing of water are key factors controlling biogeochemical cycles, primary productivity, and phenology, in addition to regulating regional agricultural production and economic output. Nevertheless, due to the inherent complexity of the signals, a comprehensive framework to understand seasonal rainfall profiles across multiple timescales and geographical regions is still lacking. Here, we formulate a global measure of seasonality and investigate changes in the seasonal rainfall regime across the tropics in the past century. The seasonality index, which captures the effects of both the magnitude and concentration of the rainy season, is highest in the northeast region of Brazil, western and central Africa, northern Australia, and parts of the Caribbean and Southeast Asia (the seasonally dry tropics). Further decomposing rainfall seasonality into its magnitude, duration, and timing components using spectral techniques and information theory, we find marked increase in the interannual variability of seasonality over most of the dry tropics, implying increasing uncertainty in the intensity, duration, and arrival of seasonal rainfall over the past century. We also show that such increase in variability has occurred in conjunction with shifts in the seasonal timing and changes in its overall magnitude. Thus, it is importance to place the analysis of rainfall regimes in these regions into a seasonal context that is most relevant to local ecological and social processes. These changes, if sustained into the next century, will portend significant shifts in the timing of plant activities and ecosystem composition and distribution, with consequences for water and carbon cycling and water resource management in

  16. Analyses of the temporal and spatial structures of heavy rainfall from a catalog of high-resolution radar rainfall fields

    DEFF Research Database (Denmark)

    Thorndahl, Søren; Smith, James A.; Baeck, Mary Lynn

    2014-01-01

    that relate to size, structure and evolution of heavy rainfall. Extreme rainfall is also linked with severe weather (tornados, large hail and damaging wind). The diurnal cycle of rainfall for heavy rain days is characterized by an early peak in the largest rainfall rates, an afternoon-evening peak in rain...

  17. Global rainfall erosivity assessment based on high-temporal resolution rainfall records.

    Science.gov (United States)

    Panagos, Panos; Borrelli, Pasquale; Meusburger, Katrin; Yu, Bofu; Klik, Andreas; Jae Lim, Kyoung; Yang, Jae E; Ni, Jinren; Miao, Chiyuan; Chattopadhyay, Nabansu; Sadeghi, Seyed Hamidreza; Hazbavi, Zeinab; Zabihi, Mohsen; Larionov, Gennady A; Krasnov, Sergey F; Gorobets, Andrey V; Levi, Yoav; Erpul, Gunay; Birkel, Christian; Hoyos, Natalia; Naipal, Victoria; Oliveira, Paulo Tarso S; Bonilla, Carlos A; Meddi, Mohamed; Nel, Werner; Al Dashti, Hassan; Boni, Martino; Diodato, Nazzareno; Van Oost, Kristof; Nearing, Mark; Ballabio, Cristiano

    2017-06-23

    The exposure of the Earth's surface to the energetic input of rainfall is one of the key factors controlling water erosion. While water erosion is identified as the most serious cause of soil degradation globally, global patterns of rainfall erosivity remain poorly quantified and estimates have large uncertainties. This hampers the implementation of effective soil degradation mitigation and restoration strategies. Quantifying rainfall erosivity is challenging as it requires high temporal resolution(rainfall recordings. We present the results of an extensive global data collection effort whereby we estimated rainfall erosivity for 3,625 stations covering 63 countries. This first ever Global Rainfall Erosivity Database was used to develop a global erosivity map at 30 arc-seconds(~1 km) based on a Gaussian Process Regression(GPR). Globally, the mean rainfall erosivity was estimated to be 2,190 MJ mm ha -1 h -1 yr -1 , with the highest values in South America and the Caribbean countries, Central east Africa and South east Asia. The lowest values are mainly found in Canada, the Russian Federation, Northern Europe, Northern Africa and the Middle East. The tropical climate zone has the highest mean rainfall erosivity followed by the temperate whereas the lowest mean was estimated in the cold climate zone.

  18. The all-year rainfall region of South Africa: Satellite rainfall-estimate perspective

    CSIR Research Space (South Africa)

    Engelbrecht, CJ

    2012-09-01

    Full Text Available southwest (Figure 3, node [0;2]). FIG. 3: Average frequency of occurrence of the SOM nodes in TRMM (blue) and FEWS (green). 4. CONCLUSION The bi-modal rainfall distribution over the all-year rainfall region of South Africa as previously determined...

  19. Rainfall variability and seasonality in northern Bangladesh

    Science.gov (United States)

    Bari, Sheikh Hefzul; Hussain, Md. Manjurul; Husna, Noor-E.-Ashmaul

    2017-08-01

    This paper aimed at the analysis of rainfall seasonality and variability for the northern part of South-Asian country, Bangladesh. The coefficient of variability was used to determine the variability of rainfall. While rainfall seasonality index ( SI ) and mean individual seasonality index ( \\overline{SI_i} ) were used to identify seasonal contrast. We also applied Mann-Kendall trend test and sequential Mann-Kendall test to determine the trend in seasonality. The lowest variability was found for monsoon among the four seasons whereas winter has the highest variability. Observed variability has a decreasing tendency from the northwest region towards the northeast region. The mean individual seasonality index (0.815378 to 0.977228) indicates that rainfall in Bangladesh is "markedly seasonal with a long dry season." It was found that the length of the dry period is lower at the northeastern part of northern Bangladesh. Trend analysis results show no significant change in the seasonality of rainfall in this region. Regression analysis of \\overline{SI_i} and SI, and longitude and mean individual seasonality index show a significant linear correlation for this area.

  20. Mapping monthly rainfall erosivity in Europe

    DEFF Research Database (Denmark)

    Ballabio, C; Meusburger, K; Klik, A

    2017-01-01

    Rainfall erosivity as a dynamic factor of soil loss by water erosion is modelled intra-annually for the first time at European scale. The development of Rainfall Erosivity Database at European Scale (REDES) and its 2015 update with the extension to monthly component allowed to develop monthly and...... events. Consequently, spatio-temporal mapping of rainfall erosivity permits to identify the months and the areas with highest risk of soil loss where conservation measures should be applied in different seasons of the year....... and seasonal R-factor maps and assess rainfall erosivity both spatially and temporally. During winter months, significant rainfall erosivity is present only in part of the Mediterranean countries. A sudden increase of erosivity occurs in major part of European Union (except Mediterranean basin, western part...... to Eastern Europe. The maps also show a clear delineation of areas with different erosivity seasonal patterns, whose spatial outline was evidenced by cluster analysis. The monthly erosivity maps can be used to develop composite indicators that map both intra-annual variability and concentration of erosive...

  1. Evaluating the impacts of cumulus, land surface and ocean surface schemes on summertime rainfall simulations over East-to-southeast Asia and the western north Pacific by RegCM4

    Science.gov (United States)

    Li, Yu-Bin; Tam, Chi-Yung; Huang, Wan-Ru; Cheung, Kevin K. W.; Gao, Zhiqiu

    2016-04-01

    This study evaluates the sensitivity of summertime rainfall simulations over East-to-southeast Asia and the western north Pacific in the regional climate model version 4 (RegCM4) to cumulus (including Grell with Arakawa-Schubert type closure, Grell with Fritsch-Chappell type closure, and Emanuel), land surface (Biosphere-atmosphere transfer scheme or BATS, and the community land model or CLM) and ocean surface (referred to as Zeng1, Zeng2 and BATS1e in the model) schemes by running the model with different combinations of these parameterization packages. For each of these experiments, ensemble integration of the model was carried out in the extended boreal summer of May-October from 1998 to 2007. The simulated spatial distribution, intensity and inter-annual variation of the precipitation, latent heat flux, position of the subtropical high and tropical cyclone genesis patterns from these numerical experiments were analyzed. Examinations show that the combination of Emanuel, CLM and Zeng2 (E-C-Z2) yields the best overall results, consistent with the fact that physical mechanisms considered in E-C-Z2 tend to be more comprehensive in comparison with the others. Additionally, the rainfall quantity is found very sensitive to sea surface roughness length, and the reduction of the roughness length constant (from 2 × 10-4 to 5 × 10-5 m) in our modified BATS1e mitigates the drastic overestimation of latent heat flux and rainfall, and is therefore preferable to the default value for simulations in the western north Pacific region in RegCM4.

  2. Lightning activity with rainfall during El Nino and La Nina events over India

    Science.gov (United States)

    Tinmaker, M. I. R.; Aslam, M. Y.; Ghude, Sachin D.; Chate, D. M.

    2017-10-01

    This paper appraises the association of lightning flash count (FC) with rainfall using the satellite-borne Lightning Imaging Sensor's (LIS) data along with gridded rainfall data (0.5o × 0.5o) for Indian summer monsoon seasons over 10 years (2001-2010). During strong El Nino years, 2002 and 2009, FCs were greater in magnitude by about 26.5 % and 37 %, than the long-term average, respectively, while during weak El Nino year (2004), it was more by 8 %. During the same years, the rainfall was deficient by about 10 % than the long-term average. Similarly, a rise in aerosol optical depth (AOD) over its average value (by about 15 % and 20 %) reduces the ratio of rainfall to FC (RLR) by 41 % and 44 % for strong El Nino years 2002 and 2009, respectively, and for weak El Nino year (2004), a 6.5 % rise in AOD lowers the RLR by 20 %. Bowen ratio more by 11 % and 17 % of its average value reduces the RLR by 41 % and 44 % for strong El Nino years 2002 and 2009, respectively, and, also, Bowen ratio higher by 8 % for 2004 declines RLR by 20 %. On the other hand, Bowen ratio less by 9 % and 6 % raises the RLR by 19 % and 56 % for moderate La Nina year (2007) and strong La Nina year (2010), respectively. Results for the daily rainfall, AOD and Bowen ratio over Indian regions, are discussed for strong El Nino and La Nina years. Correlations of FC with AOD and Bowen ratio of 0.66 and 0.71, respectively, while, that of FC with ONI of 0.56 indicates numerous (fewer) break days during El Nino (La Nina) years.

  3. Spatial moments of catchment rainfall: rainfall spatial organisation, basin morphology, and flood response

    Directory of Open Access Journals (Sweden)

    D. Zoccatelli

    2011-12-01

    Full Text Available This paper describes a set of spatial rainfall statistics (termed "spatial moments of catchment rainfall" quantifying the dependence existing between spatial rainfall organisation, basin morphology and runoff response. These statistics describe the spatial rainfall organisation in terms of concentration and dispersion statistics as a function of the distance measured along the flow routing coordinate. The introduction of these statistics permits derivation of a simple relationship for the quantification of catchment-scale storm velocity. The concept of the catchment-scale storm velocity takes into account the role of relative catchment orientation and morphology with respect to storm motion and kinematics. The paper illustrates the derivation of the statistics from an analytical framework recently proposed in literature and explains the conceptual meaning of the statistics by applying them to five extreme flash floods occurred in various European regions in the period 2002–2007. High resolution radar rainfall fields and a distributed hydrologic model are employed to examine how effective are these statistics in describing the degree of spatial rainfall organisation which is important for runoff modelling. This is obtained by quantifying the effects of neglecting the spatial rainfall variability on flood modelling, with a focus on runoff timing. The size of the study catchments ranges between 36 to 982 km2. The analysis reported here shows that the spatial moments of catchment rainfall can be effectively employed to isolate and describe the features of rainfall spatial organization which have significant impact on runoff simulation. These statistics provide useful information on what space-time scales rainfall has to be monitored, given certain catchment and flood characteristics, and what are the effects of space-time aggregation on flood response modeling.

  4. Spatial variability of trends in hydrological extremes induced by orographically enhanced rainfall events due to westerly atmospheric circulations.

    Science.gov (United States)

    Pfister, L; Drogue, G; Poirier, C; Hoffmann, L

    2005-01-01

    Since the mid 1970s, the number of days with westerly atmospheric circulations has strongly increased during winter months. As a consequence, rainfall totals, rainfall event duration and intensity have been subject to significant positive trends throughout the Mosel river basin. However, the trends identified through the non-parametrical test named Kendall's tau have shown to be spatially varying. The intensity of the trends appears to be directly linked to orographic obstacles that are well known to have a strong influence on average rainfall totals. A direct consequence of the changes having affected winter rainfall under westerly atmospheric circulations on the one hand and the spatial variability of these changes on the other hand, is a spatially varying positive trend in maximum winter streamflow. Thus, even though a clear large-scale change has affected winter rainfall over the past decades, its intensity is either strongly moderated or enhanced by orographic obstacles. The related changes in streamflow are directly dependent on the spatial variability of the changed rainfall characteristics.

  5. Strongly Correlated Topological Insulators

    Science.gov (United States)

    2016-02-03

    Strongly Correlated Topological Insulators In the past year, the grant was used for work in the field of topological phases, with emphasis on finding...surface of topological insulators. In the past 3 years, we have started a new direction, that of fractional topological insulators. These are materials...in which a topologically nontrivial quasi-flat band is fractionally filled and then subject to strong interactions. The views, opinions and/or

  6. A review of the Southern Oscillation - Oceanic-atmospheric circulation changes and related rainfall anomalies

    Science.gov (United States)

    Kousky, V. E.; Kagano, M. T.; Cavalcanti, I. F. A.

    1984-01-01

    The region of South America is emphasized in the present consideration of the Southern Oscillation (SO) oceanic and atmospheric circulation changes. The persistence of climate anomalies associated with El Nino-SO events is due to strong atmosphere-ocean coupling. Once initiated, the SO follows a certain sequence of events with clearly defined effects on tropical and subtropical rainfall. Excessive rainfall related to the SO in the central and eastern Pacific, Peru, Ecuador, and southern Brazil, are complemented by drought in Australia, Indonesia, India, West Africa, and northeast Brazil. El Nino-SO events are also associated with dramatic changes in the tropospheric flow pattern over a broad area of both hemispheres.

  7. Strong Cosmic Censorship

    Science.gov (United States)

    Isenberg, James

    2017-01-01

    The Hawking-Penrose theorems tell us that solutions of Einstein's equations are generally singular, in the sense of the incompleteness of causal geodesics (the paths of physical observers). These singularities might be marked by the blowup of curvature and therefore crushing tidal forces, or by the breakdown of physical determinism. Penrose has conjectured (in his `Strong Cosmic Censorship Conjecture`) that it is generically unbounded curvature that causes singularities, rather than causal breakdown. The verification that ``AVTD behavior'' (marked by the domination of time derivatives over space derivatives) is generically present in a family of solutions has proven to be a useful tool for studying model versions of Strong Cosmic Censorship in that family. I discuss some of the history of Strong Cosmic Censorship, and then discuss what is known about AVTD behavior and Strong Cosmic Censorship in families of solutions defined by varying degrees of isometry, and discuss recent results which we believe will extend this knowledge and provide new support for Strong Cosmic Censorship. I also comment on some of the recent work on ``Weak Null Singularities'', and how this relates to Strong Cosmic Censorship.

  8. A method for predicting monthly rainfall patterns

    International Nuclear Information System (INIS)

    Njau, E.C.

    1987-11-01

    A brief survey is made of previous methods that have been used to predict rainfall trends or drought spells in different parts of the earth. The basic methodologies or theoretical strategies used in these methods are compared with contents of a recent theory of Sun-Weather/Climate links (Njau, 1985a; 1985b; 1986; 1987a; 1987b; 1987c) which point towards the possibility of practical climatic predictions. It is shown that not only is the theoretical basis of each of these methodologies or strategies fully incorporated into the above-named theory, but also this theory may be used to develop a technique by which future monthly rainfall patterns can be predicted in further and finer details. We describe the latter technique and then illustrate its workability by means of predictions made on monthly rainfall patterns in some East African meteorological stations. (author). 43 refs, 11 figs, 2 tabs

  9. Contribution of raindrop impact to the change of soil physical properties and water erosion under semi-arid rainfalls.

    Science.gov (United States)

    Vaezi, Ali Reza; Ahmadi, Morvarid; Cerdà, Artemi

    2017-04-01

    Soil erosion by water is a three-phase process that consists of detachment of soil particles from the soil mass, transportation of detached particles either by raindrop impact or surface water flow, and sedimentation. Detachment by raindrops is a key component of the soil erosion process. However, little information is available on the role of raindrop impact on soil losses in the semi-arid regions where vegetation cover is often poor and does not protect the soil from rainfall. The objective of this study is to determine the contribution of raindrop impact to changes in soil physical properties and soil losses in a semiarid weakly-aggregated agricultural soil. Soil losses were measured under simulated rainfalls of 10, 20, 30, 40, 50, 60 and 70mmh -1 , and under two conditions: i) with raindrop impact; and, ii) without raindrop impact. Three replications at each rainfall intensity and condition resulted in a total of 42 microplots of 1m×1.4m installed on a 10% slope according to a randomized complete block design. The contribution of raindrop impact to soil loss was computed using the difference between soil loss with raindrop impact and without raindrop impact at each rainfall intensity. Soil physical properties (aggregate size, bulk density and infiltration rate) were strongly damaged by raindrop impact as rainfall intensity increased. Soil loss was significantly affected by rainfall intensity under both soil surface conditions. The contribution of raindrop impact to soil loss decreased steadily with increasing rainfall intensity. At the lower rainfall intensities (20-30mmh -1 ), raindrop impact was the dominant factor controlling soil loss from the plots (68%) while at the higher rainfall intensities (40-70mmh -1 ) soil loss was mostly affected by increasing runoff discharge. At higher rainfall intensities the sheet flow protected the soil from raindrop impact. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Monsoon rainfall over India in June and link with northwest tropical pacific - June ISMR and link with northwest tropical pacific

    Science.gov (United States)

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

    2018-03-01

    Recent years have witnessed large interannual variation of all-India rainfall (AIR) in June, with intermittent large deficits and excesses. Variability of June AIR is found to have the strongest link with variation of rainfall over northwest tropical Pacific (NWTP), with AIR deficit (excess) associated with enhancement (suppression) of NWTP rainfall. This association is investigated using high-resolution Meteorological Research Institute model which shows high skill in simulating important features of Asian summer monsoon, its variability and the inverse relationship between NWTP rainfall and AIR. Analysis of the variation of NWTP rainfall shows that it is associated with a change in the latitudinal position of subtropical westerly jet over the region stretching from West of Tibetan Plateau (WTP) to NWTP and the phase of Rossby wave steered in it with centres over NWTP and WTP. In years with large rainfall excess/deficit, the strong link between AIR and NWTP rainfall exists through differences in Rossby wave phase steered in the jet. The positive phase of the WTP-NWTP pattern, with troughs over WTP and west of NWTP, tends to be associated with increased rainfall over NWTP and decreased AIR. This scenario is reversed in the opposite phase. Thus, the teleconnection between NWTP rainfall and AIR is a manifestation of the difference in the phase of Rossby wave between excess and deficit years, with centres over WTP and NWTP. This brings out the importance of prediction of phase of Rossby waves over WTP and NWTP in advance, for prediction of June rainfall over India.

  11. Does GPM-based multi-satellite precipitation enhance rainfall estimates over Pakistan and Bolivia arid regions?

    Science.gov (United States)

    Hussain, Y.; Satgé, F.; Bonnet, M. P.; Pillco, R.; Molina, J.; Timouk, F.; Roig, H.; Martinez-Carvajal, H., Sr.; Gulraiz, A.

    2016-12-01

    Arid regions are sensitive to rainfall variations which are expressed in the form of flooding and droughts. Unfortunately, those regions are poorly monitored and high quality rainfall estimates are still needed. The Global Precipitation Measurement (GPM) mission released two new satellite rainfall products named Integrated Multisatellite Retrievals GPM (IMERG) and Global Satellite Mapping of Precipitation version 6 (GSMaP-v6) bringing the possibility of accurate rainfall monitoring over these countries. This study assessed both products at monthly scale over Pakistan considering dry and wet season over the 4 main climatic zones from 2014 to 2016. With similar climatic conditions, the Altiplano region of Bolivia is considered to quantify the influence of big lakes (Titicaca and Poopó) in rainfall estimates. For comparison, the widely used TRMM-Multisatellite Precipitation Analysis 3B43 (TMPA-3B43) version 7 is also involved in the analysis to observe the potential enhancement in rainfall estimate brought by GPM products. Rainfall estimates derived from 110 rain-gauges are used as reference to compare IMERG, GSMaP-v6 and TMPA-3B43 at the 0.1° and 0.25° spatial resolution. Over both regions, IMERG and GSMaP-v6 capture the spatial pattern of precipitation as well as TMPA-3B43. All products tend to over estimates rainfall over very arid regions. This feature is even more marked during dry season. However, during this season, both reference and estimated rainfall remain very low and do not impact seasonal water budget computation. On a general way, IMERG slightly outperforms TMPA-3B43 and GSMaP-v6 which provides the less accurate rainfall estimate. The TMPA-3B43 rainfall underestimation previously found over Lake Titicaca is still observed in IMERG estimates. However, GSMaP-v6 considerably decreases the underestimation providing the most accurate rainfall estimate over the lake. MOD11C3 Land Surface Temperature (LST) and ASTER Global Emissivity Dataset reveal strong

  12. Weak linkage between the heaviest rainfall and tallest storms.

    Science.gov (United States)

    Hamada, Atsushi; Takayabu, Yukari N; Liu, Chuntao; Zipser, Edward J

    2015-02-24

    Conventionally, the heaviest rainfall has been linked to the tallest, most intense convective storms. However, the global picture of the linkage between extreme rainfall and convection remains unclear. Here we analyse an 11-year record of spaceborne precipitation radar observations and establish that a relatively small fraction of extreme convective events produces extreme rainfall rates in any region of the tropics and subtropics. Robust differences between extreme rainfall and convective events are found in the rainfall characteristics and environmental conditions, irrespective of region; most extreme rainfall events are characterized by less intense convection with intense radar echoes not extending to extremely high altitudes. Rainfall characteristics and environmental conditions both indicate the importance of warm-rain processes in producing extreme rainfall rates. Our results demonstrate that, even in regions where severe convective storms are representative extreme weather events, the heaviest rainfall events are mostly associated with less intense convection.

  13. Tropical Rainfall Measurement Mission (TRMM) Operation Summary

    Science.gov (United States)

    Nio, Tomomi; Saito, Susumu; Stocker, Erich; Pawloski, James H.; Murayama, Yoshifumi; Ohata, Takeshi

    2015-01-01

    The Tropical Rainfall Measurement Mission (TRMM) is a joint U.S. and Japan mission to observe tropical rainfall, which was launched by H-II No. 6 from Tanegashima in Japan at 6:27 JST on November 28, 1997. After the two-month commissioning of TRMM satellite and instruments, the original nominal mission lifetime was three years. In fact, the operations has continued for approximately 17.5 years. This paper provides a summary of the long term operations of TRMM.

  14. Entropy of stable seasonal rainfall distribution in Kelantan

    Science.gov (United States)

    Azman, Muhammad Az-zuhri; Zakaria, Roslinazairimah; Satari, Siti Zanariah; Radi, Noor Fadhilah Ahmad

    2017-05-01

    Investigating the rainfall variability is vital for any planning and management in many fields related to water resources. Climate change can gives an impact of water availability and may aggravate water scarcity in the future. Two statistics measurements which have been used by many researchers to measure the rainfall variability are variance and coefficient of variation. However, these two measurements are insufficient since rainfall distribution in Malaysia especially in the East Coast of Peninsular Malaysia is not symmetric instead it is positively skewed. In this study, the entropy concept is used as a tool to measure the seasonal rainfall variability in Kelantan and ten rainfall stations were selected. In previous studies, entropy of stable rainfall (ESR) and apportionment entropy (AE) were used to describe the rainfall amount variability during years for Australian rainfall data. In this study, the entropy of stable seasonal rainfall (ESSR) is suggested to model rainfall amount variability during northeast monsoon (NEM) and southwest monsoon (SWM) seasons in Kelantan. The ESSR is defined to measure the long-term average seasonal rainfall amount variability within a given year (1960-2012). On the other hand, the AE measures the rainfall amounts variability across the months. The results of ESSR and AE values show that stations in east coastline are more variable as compared to other stations inland for Kelantan rainfall. The contour maps of ESSR for Kelantan rainfall stations are also presented.

  15. Analysis of Rainfall Infiltration Law in Unsaturated Soil Slope

    Science.gov (United States)

    Zhang, Gui-rong; Qian, Ya-jun; Wang, Zhang-chun; Zhao, Bo

    2014-01-01

    In the study of unsaturated soil slope stability under rainfall infiltration, it is worth continuing to explore how much rainfall infiltrates into the slope in a rain process, and the amount of rainfall infiltrating into slope is the important factor influencing the stability. Therefore, rainfall infiltration capacity is an important issue of unsaturated seepage analysis for slope. On the basis of previous studies, rainfall infiltration law of unsaturated soil slope is analyzed. Considering the characteristics of slope and rainfall, the key factors affecting rainfall infiltration of slope, including hydraulic properties, water storage capacity (θ s - θ r), soil types, rainfall intensities, and antecedent and subsequent infiltration rates on unsaturated soil slope, are discussed by using theory analysis and numerical simulation technology. Based on critical factors changing, this paper presents three calculation models of rainfall infiltrability for unsaturated slope, including (1) infiltration model considering rainfall intensity; (2) effective rainfall model considering antecedent rainfall; (3) infiltration model considering comprehensive factors. Based on the technology of system response, the relationship of rainfall and infiltration is described, and the prototype of regression model of rainfall infiltration is given, in order to determine the amount of rain penetration during a rain process. PMID:24672332

  16. Land cover and rainfall interact to shape waterbird community composition.

    Directory of Open Access Journals (Sweden)

    Colin E Studds

    Full Text Available Human land cover can degrade estuaries directly through habitat loss and fragmentation or indirectly through nutrient inputs that reduce water quality. Strong precipitation events are occurring more frequently, causing greater hydrological connectivity between watersheds and estuaries. Nutrient enrichment and dissolved oxygen depletion that occur following these events are known to limit populations of benthic macroinvertebrates and commercially harvested species, but the consequences for top consumers such as birds remain largely unknown. We used non-metric multidimensional scaling (MDS and structural equation modeling (SEM to understand how land cover and annual variation in rainfall interact to shape waterbird community composition in Chesapeake Bay, USA. The MDS ordination indicated that urban subestuaries shifted from a mixed generalist-specialist community in 2002, a year of severe drought, to generalist-dominated community in 2003, of year of high rainfall. The SEM revealed that this change was concurrent with a sixfold increase in nitrate-N concentration in subestuaries. In the drought year of 2002, waterbird community composition depended only on the direct effect of urban development in watersheds. In the wet year of 2003, community composition depended both on this direct effect and on indirect effects associated with high nitrate-N inputs to northern parts of the Bay, particularly in urban subestuaries. Our findings suggest that increased runoff during periods of high rainfall can depress water quality enough to alter the composition of estuarine waterbird communities, and that this effect is compounded in subestuaries dominated by urban development. Estuarine restoration programs often chart progress by monitoring stressors and indicators, but rarely assess multivariate relationships among them. Estuarine management planning could be improved by tracking the structure of relationships among land cover, water quality, and waterbirds

  17. Experimental rainfall-runoff data: Reconsidering the concept of infiltration capacity

    Science.gov (United States)

    Langhans, Christoph; Govers, Gerard; Diels, Jan; Leys, Annemie; Clymans, Wim; Putte, An Van den; Valckx, Jan

    2011-03-01

    SummaryMany infiltration models rely on an effective hydraulic conductivity parameter ( Ke) which is often determined in the field from rainfall simulation experiments on small plots. Ke can be defined as the spatially averaged infiltration capacity when the soil is 'field-saturated' and steady state is reached. Then it equals the infiltration rate ( f), provided ponding occurs. When a homogeneous surface is assumed, with negligible ponding depth, Ke is constant and does not vary with rainfall intensity ( r). We developed a drop infiltrometer that allows measuring Ke on small plots under simulated rainfall intensities that vary between experiments. Infiltration experiments were conducted on a winter wheat field in the Belgian Loess Belt and various surface and soil properties were measured. Furthermore, photos were taken of the soil surface during the infiltration experiments for the determination of the inundated surface fraction. The results of the experiments show that Ke is strongly dependent on rainfall intensity. In a statistical approach a dynamic Ke could be estimated with a function of rainfall intensity, tillage treatment, percentage residue cover and bulk density. Observations indicate that microtopography, surface fraction covered by a sedimentary seal and macroporosity interact with rainfall intensity, surface ponding and infiltration. We propose that Ke in physically based infiltration models should either be made dependent on dynamic state variables in a mechanistic way, such as ponding depth and water content or made dependent on rainfall intensity using an empirical relationship. With such adaptations, both surface runoff and erosion models might have more potential to deal with scale effects in runoff generation.

  18. Factors controlling January-April rainfall over southern India and Sri Lanka

    Energy Technology Data Exchange (ETDEWEB)

    Vialard, J. [Universite Pierre et Marie Curie, Laboratoire d' Oceanographie Experimentation et Approches Numeriques (LOCEAN), CNRS, IRD, Paris (France); National Institute of Oceanography, Dona Paula, Goa (India); Terray, P. [Universite Pierre et Marie Curie, Laboratoire d' Oceanographie Experimentation et Approches Numeriques (LOCEAN), CNRS, IRD, Paris (France); Duvel, J.P. [CNRS, Laboratoire de Meteorologie Dynamique, Paris (France); Nanjundiah, R.S. [IISc, Center of Atmospheric and Oceanic Sciences, Bangalore (India); Shenoi, S.S.C. [Indian National Centre for Ocean Information Services, Hyderabad (India); Shankar, D. [National Institute of Oceanography, Dona Paula, Goa (India)

    2011-08-15

    Most of the annual rainfall over India occurs during the Southwest (June-September) and Northeast (October-December) monsoon periods. In March 2008, however, Southern peninsular India and Sri Lanka received the largest rainfall anomaly on record since 1979, with amplitude comparable to summer-monsoon interannual anomalies. This anomalous rainfall appeared to be modulated at intraseasonal timescale by the Madden Julian Oscillation, and was synchronous with a decaying La Nina event in the Pacific Ocean. Was this a coincidence or indicative of a teleconnection pattern? In this paper, we explore factors controlling rainfall over southern India and Sri Lanka between January and April, i.e. outside of the southwest and northeast monsoons. This period accounts for 20% of annual precipitation over Sri Lanka and 10% over the southern Indian states of Kerala and Tamil Nadu. Interannual variability is strong (about 40% of the January-April climatology). Intraseasonal rainfall anomalies over southern India and Sri Lanka are significantly associated with equatorial eastward propagation, characteristic of the Madden Julian Oscillation. At the interannual timescale, we find a clear connection with El Nino-Southern Oscillation (ENSO); with El Ninos being associated with decreased rainfall (correlation of -0.46 significant at the 98% level). There is also a significant link with local SST anomalies over the Indian Ocean, and in particular with the inter-hemispheric sea surface temperature (SST) gradient over the Indian Ocean (with colder SST south of the equator being conducive to more rainfall, correlation of 0.55 significant at the 99% level). La Ninas/cold SSTs south of the equator tend to have a larger impact than El Ninos. We discuss two possible mechanisms that could explain these statistical relationships: (1) subsidence over southern India remotely forced by Pacific SST anomalies; (2) impact of ENSO-forced regional Indian Ocean SST anomalies on convection. However, the

  19. Synergistic effects of seasonal rainfall, parasites and demography on fluctuations in springbok body condition

    Science.gov (United States)

    Turner, Wendy C.; Versfeld, Wilferd D.; Kilian, J. Werner; Getz, Wayne M.

    2011-01-01

    Summary 1. Seasonality of rainfall can exert a strong influence on animal condition and on host-parasite interactions. The body condition of ruminants fluctuates seasonally in response to changes in energy requirements, foraging patterns and resource availability, and seasonal variation in parasite infections may further alter ruminant body condition. 2. This study disentangles effects of rainfall and gastrointestinal parasite infections on springbok (Antidorcas marsupialis) body condition and determines how these factors vary among demographic groups. 3. Using data from four years and three study areas, we investigated i) the influence of rainfall variation, demographic factors and parasite interactions on parasite prevalence or infection intensity, ii) whether parasitism or rainfall is a more important predictor of springbok body condition and iii) how parasitism and condition vary among study areas along a rainfall gradient. 4. We found that increased parasite intensity is associated with reduced body condition only for adult females. For all other demographic groups, body condition was significantly related to prior rainfall and not to parasitism. Rainfall lagged by two months had a positive effect on body condition. 5. Adult females showed evidence of a “periparturient rise” in parasite intensity, and had higher parasite intensity and lower body condition than adult males after parturition and during early lactation. After juveniles were weaned, adult females had lower parasite intensity than adult males. Sex differences in parasitism and condition may be due to differences between adult females and males in the seasonal timing of reproductive effort and its effects on host immunity, as well as documented sex differences in vulnerability to predation. 6. Our results highlight that parasites and the environment can synergistically affect host populations, but that these interactions might be masked by their interwoven relationships, their differential

  20. Analysis of the influence of rainfall variables on urban effluents concentrations and fluxes in wet weather

    Science.gov (United States)

    Gooré Bi, Eustache; Monette, Frédéric; Gasperi, Johnny

    2015-04-01

    Urban rainfall runoff has been a topic of increasing importance over the past years, a result of both the increase in impervious land area arising from constant urban growth and the effects of climate change on urban drainage. The main goal of the present study is to assess and analyze the correlations between rainfall variables and common indicators of urban water quality, namely event mean concentrations (EMCs) and event fluxes (EFs), in order to identify and explain the impacts of each of the main rainfall variables on the generation process of urban pollutants during wet periods. To perform this analysis, runoff from eight summer rainfall events that resulted in combined sewer overflow (CSO) was sampled simultaneously from two distinct catchment areas in order to quantify discharges at the respective outfalls. Pearson statistical analysis of total suspended solids (TSS), chemical oxygen demand (COD), carbonaceous biochemical oxygen demand at 5 days (CBOD5), total phosphorus (Ptot) and total kedjal nitrogen (N-TKN) showed significant correlations (ρ = 0.05) between dry antecedent time (DAT) and EMCs on one hand, and between total rainfall (TR) and the volume discharged (VD) during EFs, on the other. These results show that individual rainfall variables strongly affect either EMCs or EFs and are good predictors to consider when selecting variables for statistical modeling of urban runoff quality. The results also show that in a combined sewer network, there is a linear relationship between TSS event fluxes and COD, CBOD5, Ptot, and N-TKN event fluxes; this explains 97% of the variability of these pollutants which adsorb onto TSS during wet weather, which therefore act as tracers. Consequently, the technological solution selected for TSS removal will also lead to a reduction of these pollutants. Given the huge volumes involved, urban runoffs contribute substantially to pollutant levels in receiving water bodies, a situation which, in a climate change context, may

  1. Prediction of heavy rainfall over Chennai Metropolitan City, Tamil Nadu, India: Impact of microphysical parameterization schemes

    Science.gov (United States)

    Singh, K. S.; Bonthu, Subbareddy; Purvaja, R.; Robin, R. S.; Kannan, B. A. M.; Ramesh, R.

    2018-04-01

    This study attempts to investigate the real-time prediction of a heavy rainfall event over the Chennai Metropolitan City, Tamil Nadu, India that occurred on 01 December 2015 using Advanced Research Weather Research and Forecasting (WRF-ARW) model. The study evaluates the impact of six microphysical (Lin, WSM6, Goddard, Thompson, Morrison and WDM6) parameterization schemes of the model on prediction of heavy rainfall event. In addition, model sensitivity has also been evaluated with six Planetary Boundary Layer (PBL) and two Land Surface Model (LSM) schemes. Model forecast was carried out using nested domain and the impact of model horizontal grid resolutions were assessed at 9 km, 6 km and 3 km. Analysis of the synoptic features using National Center for Environmental Prediction Global Forecast System (NCEP-GFS) analysis data revealed strong upper-level divergence and high moisture content at lower level were favorable for the occurrence of heavy rainfall event over the northeast coast of Tamil Nadu. The study signified that forecasted rainfall was more sensitive to the microphysics and PBL schemes compared to the LSM schemes. The model provided better forecast of the heavy rainfall event using the logical combination of Goddard microphysics, YSU PBL and Noah LSM schemes, and it was mostly attributed to timely initiation and development of the convective system. The forecast with different horizontal resolutions using cumulus parameterization indicated that the rainfall prediction was not well represented at 9 km and 6 km. The forecast with 3 km horizontal resolution provided better prediction in terms of timely initiation and development of the event. The study highlights that forecast of heavy rainfall events using a high-resolution mesoscale model with suitable representations of physical parameterization schemes are useful for disaster management and planning to minimize the potential loss of life and property.

  2. Influence of rainfall spatial variability on rainfall-runoff modelling: Benefit of a simulation approach?

    Science.gov (United States)

    Emmanuel, I.; Andrieu, H.; Leblois, E.; Janey, N.; Payrastre, O.

    2015-12-01

    No consensus has yet been reached regarding the influence of rainfall spatial variability on runoff modelling at catchment outlets. To eliminate modelling and measurement errors, in addition to controlling rainfall variability and both the characteristics and hydrological behaviour of catchments, we propose to proceed by simulation. We have developed a simulation chain that combines a stream network model, a rainfall simulator and a distributed hydrological model (with four production functions and a distributed transfer function). Our objective here is to use this simulation chain as a simplified test bed in order to better understand the impact of the spatial variability of rainfall forcing. We applied the chain to contrasted situations involving catchments ranging from a few tens to several hundreds of square km2, thus corresponding to urban and peri-urban catchments for which surface runoff constitutes the dominant process. The results obtained confirm that the proposed simulation approach is helpful to better understand the influence of rainfall spatial variability on the catchment response. We have shown that significant dispersion exists not only between the various simulation scenarios (defined by a rainfall configuration and a catchment configuration), but also within each simulation scenario. These results show that the organisation of rainfall during the study event over the study catchment plays an important role, leading us to examine rainfall variability indexes capable of summarising the influence of rainfall spatial organisation on the catchment response. Thanks to the simulation chain, we have tested the variability indexes of Zoccatelli et al. (2010) and improved them by proposing two other indexes.

  3. Strong Arcwise Connectedness

    OpenAIRE

    Espinoza, Benjamin; Gartside, Paul; Kovan-Bakan, Merve; Mamatelashvili, Ana

    2012-01-01

    A space is `n-strong arc connected' (n-sac) if for any n points in the space there is an arc in the space visiting them in order. A space is omega-strong arc connected (omega-sac) if it is n-sac for all n. We study these properties in finite graphs, regular continua, and rational continua. There are no 4-sac graphs, but there are 3-sac graphs and graphs which are 2-sac but not 3-sac. For every n there is an n-sac regular continuum, but no regular continuum is omega-sac. There is an omega-sac ...

  4. Abortion: Strong's counterexamples fail

    DEFF Research Database (Denmark)

    Di Nucci, Ezio

    2009-01-01

    This paper shows that the counterexamples proposed by Strong in 2008 in the Journal of Medical Ethics to Marquis's argument against abortion fail. Strong's basic idea is that there are cases--for example, terminally ill patients--where killing an adult human being is prima facie seriously morally......'s scenarios have some valuable future or admitted that killing them is not seriously morally wrong. Finally, if "valuable future" is interpreted as referring to objective standards, one ends up with implausible and unpalatable moral claims....

  5. Impacts of the Pacific meridional mode on rainfall over the maritime continent and australia: potential for seasonal predictions

    Science.gov (United States)

    Zhang, Wei; Villarini, Gabriele; Vecchi, Gabriel A.

    2017-11-01

    This study assesses whether, the extent to which and why the Pacific Meridional Mode (PMM) modulates rainfall in Australia and the Maritime Continent. We find a statistically significant time-lagged association between March-to-May (MAM) PMM and September-to-November (SON) rainfall in the Maritime Continent and Australia. The association is largely caused by the contribution of PMM to the El Niño Southern Oscillation (ENSO). Positive (negative) MAM PMM is generally followed by El Niño (La Niña) events in the following SON and December-to-February (DJF), which then suppresses (enhances) rainfall in the Maritime Continent and Australia. The suppression (enhancement) of rainfall is closely tied to the dynamical changes of moisture flux using moisture flux potential and its divergent components. Following the positive (negative) PMM phases, there is a strong moisture flux potential sink (source) in SON over the Maritime Continent and Australia, which act to suppress (enhance) rainfall there. Using MAM PMM as a predictor for SON rainfall in the Maritime Continent and Australia, the prediction skill is comparable to the North American Multimodel Ensemble project (NMME) forecasts initialized in June over the period 1981-2014. This suggests that MAM PMM may be used as a predictor for SON rainfall in the Maritime Continent and Australia.

  6. Impact assessment of El Nino and La Nina episodes on local/regional monsoon rainfall in India

    International Nuclear Information System (INIS)

    Singh, Sureuder; Rao, V.U.M.; Shigh, Diwan

    2002-08-01

    Large scale atmospheric circulation's and climatic anomalies have been shown to have a significant impact on seasonal weather over many parts of the world. In the present paper an attempt has been made to examine regional monsoon dynamics in relation with El Nino and La Nina episodes. The investigation was earned out for the meteorological sub- division's comprising the areas of Haryana, Delhi and Chandigarh in India. The monthly monsoon rainfall data of different locations in the region and corresponding data on El Nino and La Nina episodes for the period of 30 years (1970-99) were used for this investigation. During the El Nino episodes, various locations experienced excess rainfall in monsoon ranged between 11 and 22 percent. Under the influence of La Nina episodes, the probability of excess monsoon rainfall at different locations in the sub-division ranged between 13 and 25 percent. However, many locations viz., Hisar, Bhiwani, Gurgaon, Delhi and Chandigarh received deficient monsoon rainfall which was contrary to the global belief of the association between SST anomalies and rainfall distribution. No significant association was observed between El Nino and La Nina and monsoon rainfall at different locations in the entire sub-division. However, there was a strong relationship between these SST anomalies and all India monsoon rainfall over the period under study (1970-99). (author)

  7. Introducing a rainfall compound distribution model based on weather patterns sub-sampling

    Directory of Open Access Journals (Sweden)

    F. Garavaglia

    2010-06-01

    Full Text Available This paper presents a probabilistic model for daily rainfall, using sub-sampling based on meteorological circulation. We classified eight typical but contrasted synoptic situations (weather patterns for France and surrounding areas, using a "bottom-up" approach, i.e. from the shape of the rain field to the synoptic situations described by geopotential fields. These weather patterns (WP provide a discriminating variable that is consistent with French climatology, and allows seasonal rainfall records to be split into more homogeneous sub-samples, in term of meteorological genesis.

    First results show how the combination of seasonal and WP sub-sampling strongly influences the identification of the asymptotic behaviour of rainfall probabilistic models. Furthermore, with this level of stratification, an asymptotic exponential behaviour of each sub-sample appears as a reasonable hypothesis. This first part is illustrated with two daily rainfall records from SE of France.

    The distribution of the multi-exponential weather patterns (MEWP is then defined as the composition, for a given season, of all WP sub-sample marginal distributions, weighted by the relative frequency of occurrence of each WP. This model is finally compared to Exponential and Generalized Pareto distributions, showing good features in terms of robustness and accuracy. These final statistical results are computed from a wide dataset of 478 rainfall chronicles spread on the southern half of France. All these data cover the 1953–2005 period.

  8. Increased Spatial Variability and Intensification of Extreme Monsoon Rainfall due to Urbanization.

    Science.gov (United States)

    Paul, Supantha; Ghosh, Subimal; Mathew, Micky; Devanand, Anjana; Karmakar, Subhankar; Niyogi, Dev

    2018-03-02

    While satellite data provides a strong robust signature of urban feedback on extreme precipitation; urbanization signal is often not so prominent with station level data. To investigate this, we select the case study of Mumbai, India and perform a high resolution (1 km) numerical study with Weather Research and Forecasting (WRF) model for eight extreme rainfall days during 2014-2015. The WRF model is coupled with two different urban schemes, the Single Layer Urban Canopy Model (WRF-SUCM), Multi-Layer Urban Canopy Model (WRF-MUCM). The differences between the WRF-MUCM and WRF-SUCM indicate the importance of the structure and characteristics of urban canopy on modifications in precipitation. The WRF-MUCM simulations resemble the observed distributed rainfall. WRF-MUCM also produces intensified rainfall as compared to the WRF-SUCM and WRF-NoUCM (without UCM). The intensification in rainfall is however prominent at few pockets of urban regions, that is seen in increased spatial variability. We find that the correlation of precipitation across stations within the city falls below statistical significance at a distance greater than 10 km. Urban signature on extreme precipitation will be reflected on station rainfall only when the stations are located inside the urban pockets having intensified precipitation, which needs to be considered in future analysis.

  9. Hydraulic properties for interrill erosion on steep slopes using a portable rainfall simulator

    Science.gov (United States)

    Shin, Seung Sook; Hwang, Yoonhee; Deog Park, Sang; Yun, Minu; Park, Sangyeon

    2017-04-01

    The hydraulic parameters for sheet flow on steep slopes have been not frequently measured because the shallow flow depth and slow flow velocity are difficult to measure. In this study hydraulic values of sheet flow were analyzed to evaluate interrill erosion on steep slopes. A portable rainfall simulator was used to conduct interrill erosion test. The kinetic energy of rainfall simulator was obtained by disdrometer being capable of measuring the drop size distribution and velocity of falling raindrops. The sheet flow velocity was determined by the taken time for a dye transferring fixed points using video images. Surface runoff discharge and sediment yield increased with increase of rainfall intensity and kinetic energy and slope steepness. Especially sediment yield was strongly correlated with sheet flow velocity. The maximum velocity of sheet flow was 2.3cm/s under rainfall intensity of 126.8mm/h and slope steepness of 53.2%. The sheet flow was laminar and subcritical flow as the flow Reynolds number and Froude number are respectively the ranges of 10 22 and 0.05 0.25. The roughness coefficient (Manning's n) for sheet flow on steep slopes was relatively large compared to them on the gentle slope. Keywords: Sheet flow velocity; Rainfall simulator; Interrill erosion; Steep slope This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIP) (No. 2015R1C1A2A01055469).

  10. Seasonal prediction of Indian summer monsoon rainfall in NCEP CFSv2: forecast and predictability error

    Science.gov (United States)

    Pokhrel, Samir; Saha, Subodh Kumar; Dhakate, Ashish; Rahman, Hasibur; Chaudhari, Hemantkumar S.; Salunke, Kiran; Hazra, Anupam; Sujith, K.; Sikka, D. R.

    2016-04-01

    A detailed analysis of sensitivity to the initial condition for the simulation of the Indian summer monsoon using retrospective forecast by the latest version of the Climate Forecast System version-2 (CFSv2) is carried out. This study primarily focuses on the tropical region of Indian and Pacific Ocean basin, with special emphasis on the Indian land region. The simulated seasonal mean and the inter-annual standard deviations of rainfall, upper and lower level atmospheric circulations and Sea Surface Temperature (SST) tend to be more skillful as the lead forecast time decreases (5 month lead to 0 month lead time i.e. L5-L0). In general spatial correlation (bias) increases (decreases) as forecast lead time decreases. This is further substantiated by their averaged value over the selected study regions over the Indian and Pacific Ocean basins. The tendency of increase (decrease) of model bias with increasing (decreasing) forecast lead time also indicates the dynamical drift of the model. Large scale lower level circulation (850 hPa) shows enhancement of anomalous westerlies (easterlies) over the tropical region of the Indian Ocean (Western Pacific Ocean), which indicates the enhancement of model error with the decrease in lead time. At the upper level circulation (200 hPa) biases in both tropical easterly jet and subtropical westerlies jet tend to decrease as the lead time decreases. Despite enhancement of the prediction skill, mean SST bias seems to be insensitive to the initialization. All these biases are significant and together they make CFSv2 vulnerable to seasonal uncertainties in all the lead times. Overall the zeroth lead (L0) seems to have the best skill, however, in case of Indian summer monsoon rainfall (ISMR), the 3 month lead forecast time (L3) has the maximum ISMR prediction skill. This is valid using different independent datasets, wherein these maximum skill scores are 0.64, 0.42 and 0.57 with respect to the Global Precipitation Climatology Project

  11. Selection at the Y chromosome of the African buffalo driven by rainfall.

    Directory of Open Access Journals (Sweden)

    Pim van Hooft

    Full Text Available Selection coefficients at the mammalian Y chromosome typically do not deviate strongly from neutrality. Here we show that strong balancing selection, maintaining intermediate frequencies of DNA sequence variants, acts on the Y chromosome in two populations of African buffalo (Syncerus caffer. Significant correlations exist between sequence variant frequencies and annual rainfall in the years before conception, with five- to eightfold frequency changes over short time periods. Annual rainfall variation drives the balancing of sequence variant frequencies, probably by affecting parental condition. We conclude that sequence variants confer improved male reproductive success after either dry or wet years, making the population composition and dynamics very sensitive to climate change. The mammalian Y chromosome, interacting with ecological processes, may affect male reproductive success much more strongly than previously thought.

  12. Flexible strategies for coping with rainfall variability

    NARCIS (Netherlands)

    Siderius, Christian; Biemans, Hester; Walsum, Van Paul E.V.; Ierland, Van Ekko C.; Kabat, Pavel; Hellegers, Petra J.G.J.

    2016-01-01

    One of the main manifestations of climate change will be increased rainfall variability. How to deal with this in agriculture will be a major societal challenge. In this paper we explore flexibility in land use, through deliberate seasonal adjustments in cropped area, as a specific strategy for

  13. Characterisation of Seasonal Rainfall for Cropping Schedules ...

    African Journals Online (AJOL)

    El Nino-South Oscillation (ENSO) phenomenon occurs in the Equatorial Eastern Pacific Ocean and has been noted to account significantly for rainfall variability in many parts of the world, particularly tropical regions. This variability is very important in rainfed crop production and needs to be well understood. Thirty years of ...

  14. Coping with rainfall variability in northern Tanzania

    DEFF Research Database (Denmark)

    Trærup, Sara Lærke Meltofte

    2012-01-01

    This chapter explores a potential relationship between rainfall data and household self-reported harvest shocks and local (spatial) variability of harvest shocks and coping strategies based on a survey of 2700 rural households in the Kagera region of northern Tanzania. In addition, correlations...

  15. Weather radar rainfall data in urban hydrology

    NARCIS (Netherlands)

    Thorndahl, Søren; Einfalt, Thomas; Willems, Patrick; Ellerbæk Nielsen, Jesper; ten Veldhuis, J.A.E.; Arnbjerg-Nielsen, Karsten; Rasmussen, Michael R.; Molnar, Peter

    2017-01-01

    Application of weather radar data in urban hydrological applications has evolved significantly during the past decade as an alternative to traditional rainfall observations with rain gauges. Advances in radar hardware, data processing, numerical models, and emerging fields within urban hydrology

  16. Comparison of radar data versus rainfall data.

    Science.gov (United States)

    Espinosa, B; Hromadka, T V; Perez, R

    2015-01-01

    Doppler radar data are increasingly used in rainfall-runoff synthesis studies, perhaps due to radar data availability, among other factors. However, the veracity of the radar data are often a topic of concern. In this paper, three Doppler radar outcomes developed by the United States National Weather Service at three radar sites are examined and compared to actual rain gage data for two separate severe storm events in order to assess accuracy in the published radar estimates of rainfall. Because the subject storms were very intense rainfall events lasting approximately one hour in duration, direct comparisons between the three radar gages themselves can be made, as well as a comparison to rain gage data at a rain gage location subjected to the same storm cells. It is shown that topographic interference with the radar outcomes can be a significant factor leading to differences between radar and rain gage readings, and that care is needed in calibrating radar outcomes using available rain gage data in order to interpolate rainfall estimates between rain gages using the spatial variation observed in the radar readings. The paper establishes and describes•the need for "ground-truthing" of radar data, and•possible errors due to topographic interference.

  17. Improving the understanding of rainfall distribution and ...

    African Journals Online (AJOL)

    The characterisation of rainfall variability, spatially and temporally, is essential for hydrological and ecological analyses. Inherently, this variability is distinctly more obvious in mountainous areas compared to lowlands. The objective of this study was to ascertain if the use of the regression-Kriging technique would provide ...

  18. Spatial variability and rainfall characteristics of Kerala

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    The rain gauge network of Kerala, whose data for. 1950–1990 was used in this study, is shown in fig- ure 2. ... gauge stations and north Kerala has 39 rainfall stations. The details of the stations are given in table 1. ..... pressure systems that move into the Bay of Bengal. (Das 1995). The tapering shape of the peninsula.

  19. Rainfall erosivity in Brazil: A Review

    Science.gov (United States)

    In this paper, we review the erosivity studies conducted in Brazil to verify the quality and representativeness of the results generated and to provide a greater understanding of the rainfall erosivity (R-factor) in Brazil. We searched the ISI Web of Science, Scopus, SciELO, and Google Scholar datab...

  20. Improving the understanding of rainfall distribution and ...

    African Journals Online (AJOL)

    2016-10-04

    Oct 4, 2016 ... deep ravines (Scott et al., 2000; Briggs, 2008). The Cathedral. Peak research catchments fall within the summer rainfall region of South Africa, thus the area experiences wet, humid summers and cold, dry winters (Everson et al., 1998).The mean annual precipitation (MAP) for the area is approximately 1 400 ...

  1. Searching regional rainfall homogeneity using atmospheric fields

    Science.gov (United States)

    Gabriele, Salvatore; Chiaravalloti, Francesco

    2013-03-01

    The correct identification of homogeneous areas in regional rainfall frequency analysis is fundamental to ensure the best selection of the probability distribution and the regional model which produce low bias and low root mean square error of quantiles estimation. In an attempt at rainfall spatial homogeneity, the paper explores a new approach that is based on meteo-climatic information. The results are verified ex-post using standard homogeneity tests applied to the annual maximum daily rainfall series. The first step of the proposed procedure selects two different types of homogeneous large regions: convective macro-regions, which contain high values of the Convective Available Potential Energy index, normally associated with convective rainfall events, and stratiform macro-regions, which are characterized by low values of the Q vector Divergence index, associated with dynamic instability and stratiform precipitation. These macro-regions are identified using Hot Spot Analysis to emphasize clusters of extreme values of the indexes. In the second step, inside each identified macro-region, homogeneous sub-regions are found using kriging interpolation on the mean direction of the Vertically Integrated Moisture Flux. To check the proposed procedure, two detailed examples of homogeneous sub-regions are examined.

  2. Relationship between summer monsoon rainfall and cyclogenesis ...

    Indian Academy of Sciences (India)

    S; 120. ◦. –160. ◦. E) are useful to predict TNDC during post-monsoon (October–. December) season. The influence of ENSO (El-Nino. Southern Oscillation) and IOD (Indian ... 1984). Following this methodology, the correlations with the first differences (current season minus previous season) in rainfall and TNDC are used in.

  3. A strong comeback

    International Nuclear Information System (INIS)

    Marier, D.

    1992-01-01

    This article presents the results of a financial rankings survey which show a strong economic activity in the independent energy industry. The topics of the article include advisor turnover, overseas banks, and the increase in public offerings. The article identifies the top project finance investors for new projects and restructurings and rankings for lenders

  4. Temporal and spatial variability of rainfall over Greece

    Science.gov (United States)

    Markonis, Y.; Batelis, S. C.; Dimakos, Y.; Moschou, E.; Koutsoyiannis, D.

    2017-10-01

    Recent studies have showed that there is a significant decrease in rainfall over Greece during the last half of the pervious century, following an overall decrease of the precipitation at the eastern Mediterranean. However, during the last decade an increase in rainfall was observed in most regions of the country, contrary to the general circulation climate models forecasts. An updated high-resolution dataset of monthly sums and annual daily maxima records derived from 136 stations during the period 1940-2012 allowed us to present some new evidence for the observed change and its statistical significance. The statistical framework used to determine the significance of the slopes in annual rain was not limited to the time independency assumption (Mann-Kendall test), but we also investigated the effect of short- and long-term persistence through Monte Carlo simulation. Our findings show that (a) change occurs in different scales; most regions show a decline since 1950, an increase since 1980 and remain stable during the last 15 years; (b) the significance of the observed decline is highly dependent to the statistical assumptions used; there are indications that the Mann-Kendall test may be the least suitable method; and (c) change in time is strongly linked with the change in space; for scales below 40 years, relatively close regions may develop even opposite trends, while in larger scales change is more uniform.

  5. A 130 ka reconstruction of rainfall on the Bolivian Altiplano

    Science.gov (United States)

    Placzek, C. J.; Quade, J.; Patchett, P. J.

    2013-02-01

    New efforts to link climate reconstructions from shoreline deposits and sediment cores yield an improved and more detailed lake history from the Bolivian Altiplano. On the Southern Altiplano, 10 lake oscillations have been identified from this new unified chronology, each coincident with North Atlantic cold events such as Heinrich Events H5, H2, H1, and the Younger Dryas. By coupling this new lake history to a hydrologic budget model we are able to evaluate precipitation variability on the Southern Bolivian Altiplano over the last 130 ka. These modeling efforts underscore the relative aridity of the Altiplano during the rare and small lake cycles occurring between 80 and 20 ka, when colder temperatures combined with little or no change in rainfall produced smaller paleolakes. Relative aridity between 80 and 20 ka contrasts with the immense Tauca lake cycle (18.1-14.1 ka), which was six times larger than modern Lake Titicaca and coincided with Heinrich Event 1. This improved paleolake record from the Southern Altiplano reveals a strong link between central Andean climate and Atlantic sea-surface temperature gradients during the late Pleistocene, even though today rainfall variability is driven mostly by Pacific sea-surface temperature anomalies associated with El Niño/Southern Oscillation. However, not all Heinrich Events appear to result in lake expansions, most conspicuously during the global cold interval between 80 and 20 ka when the Altiplano and Amazon Basin were relatively arid.

  6. Temporal rainfall estimation using input data reduction and model inversion

    Science.gov (United States)

    Wright, A. J.; Vrugt, J. A.; Walker, J. P.; Pauwels, V. R. N.

    2016-12-01

    Floods are devastating natural hazards. To provide accurate, precise and timely flood forecasts there is a need to understand the uncertainties associated with temporal rainfall and model parameters. The estimation of temporal rainfall and model parameter distributions from streamflow observations in complex dynamic catchments adds skill to current areal rainfall estimation methods, allows for the uncertainty of rainfall input to be considered when estimating model parameters and provides the ability to estimate rainfall from poorly gauged catchments. Current methods to estimate temporal rainfall distributions from streamflow are unable to adequately explain and invert complex non-linear hydrologic systems. This study uses the Discrete Wavelet Transform (DWT) to reduce rainfall dimensionality for the catchment of Warwick, Queensland, Australia. The reduction of rainfall to DWT coefficients allows the input rainfall time series to be simultaneously estimated along with model parameters. The estimation process is conducted using multi-chain Markov chain Monte Carlo simulation with the DREAMZS algorithm. The use of a likelihood function that considers both rainfall and streamflow error allows for model parameter and temporal rainfall distributions to be estimated. Estimation of the wavelet approximation coefficients of lower order decomposition structures was able to estimate the most realistic temporal rainfall distributions. These rainfall estimates were all able to simulate streamflow that was superior to the results of a traditional calibration approach. It is shown that the choice of wavelet has a considerable impact on the robustness of the inversion. The results demonstrate that streamflow data contains sufficient information to estimate temporal rainfall and model parameter distributions. The extent and variance of rainfall time series that are able to simulate streamflow that is superior to that simulated by a traditional calibration approach is a

  7. Event-based stochastic point rainfall resampling for statistical replication and climate projection of historical rainfall series

    DEFF Research Database (Denmark)

    Thorndahl, Søren; Korup Andersen, Aske; Larsen, Anders Badsberg

    2017-01-01

    events. Due to climate change, however, these series are most likely not representative of future rainfall. There is therefore a demand for climate-projected long rainfall series, which can represent a specific region and rainfall pattern as well as fulfil requirements of long rainfall series which...... for the future climate, such as winter and summer precipitation, and representation of extreme events, the resampled historical series are projected to represent rainfall properties in a future climate. Climate-projected rainfall series are simulated by brute force randomization of model parameters, which leads...

  8. Deforestation alters rainfall: a myth or reality

    Science.gov (United States)

    Hanif, M. F.; Mustafa, M. R.; Hashim, A. M.; Yusof, K. W.

    2016-06-01

    To cope with the issue of food safety and human shelter, natural landscape has gone through a number of alterations. In the coming future, the expansion of urban land and agricultural farms will likely disrupt the natural environment. Researchers have claimed that land use change may become the most serious issue of the current century. Thus, it is necessary to understand the consequences of land use change on the climatic variables, e.g., rainfall. This study investigated the impact of deforestation on local rainfall. An integrated methodology was adopted to achieve the objectives. Above ground biomass was considered as the indicator of forest areas. Time series data of a Moderate Resolution Imaging Spectroradiometer (MODIS) sensor were obtained for the year of 2000, 2005, and 2010. Rainfall data were collected from the Department of Irrigation and Drainage, Malaysia. The MODIS time series data were classified and four major classes were developed based on the Normalised Difference Vegetation Index (NDVI) ranges. The results of the classification showed that water, and urban and agricultural lands have increased in their area by 2, 3, and 6%, respectively. On the other hand, the area of forest has decreased 10% collectively from 2000 to 2010. The results of NDVI and rainfall data were analysed by using a linear regression analysis. The results showed a significant relationship at a 90% confidence interval between rainfall and deforestation (t = 1.92, p = 0.06). The results of this study may provide information about the consequences of land use on the climate on the local scale.

  9. Changing rainfall and humidity within Southeast Texas.

    Science.gov (United States)

    Smith, Robert Kennedy

    2015-01-01

    Southeast Texas houses a precipitation transition zone between drier conditions to the North and West and some of the wettest parts of the continental U.S. to the East. The Region has seen an increase in its reported normal annual precipitation totals in recent decades. In order to determine if the additional rainfall has been influenced by warming temperatures or is within the variability of the State's long-term drought cycles, several analyses were performed on historical climate data. The analyses answered several questions: Have global and regional climate change models predicted precipitation increases in Southeast Texas and are future increases expected? Do historical monthly precipitation totals at various sites in the region provide clear trends of wetter conditions that can be discerned from long-term drought cycles? Are rainfall patterns changing with less frequent, heavier rain events? Do the reported increases in annual rainfall actually lead to wetter conditions in the region? Climate models have not predicted larger annual average precipitation totals nor do they forecast increases for Southeast Texas. While recent decades may have seen more rain relative to earlier periods, a combined analysis of observation stations across different parts of the Region shows that long-term trends are dependent on when the data is selected relative to a drought cycle. While some stations show larger amounts of rain falling during fewer days, these trends do not hold across all periods. An examination of hourly data does not show an increase in extreme rainfall events or a decrease in the number of hours during which rain has fallen. Even though rainfall has not decreased, average relative humidity has fallen. This suggests that the area is drying even with steady or increasing amounts of rain.

  10. Hydrologic response in karstic-ridge wetlands to rainfall and evapotranspiration, central Florida, 2001-2003

    Science.gov (United States)

    Knowles, Leel; Phelps, G.G.; Kinnaman, Sandra L.; German, Edward R.

    2005-01-01

    Two internally drained karstic wetlands in central Florida-Boggy Marsh at the Hilochee Wildlife Management Area and a large unnamed wetland at the Lyonia Preserve-were studied during 2001-03 to gain a better understanding of the net-recharge function that these wetlands provide, the significance of exchanges with ground water with regard to wetland water budgets, and the variability in wetland hydrologic response to a range of climate conditions. These natural, relatively remote and unaltered wetlands were selected to provide a baseline of natural wetland hydrologic variability to which anthropogenic influences on wetland hydrology could be compared. Large departures from normal rainfall during the study were fortuitous, and allowed monitoring of hydrologic processes over a wide range of climate conditions. Wetland responses varied greatly as a result of climate conditions that ranged from moderate drought to extremely moist. Anthropogenic activities influenced water levels at both study sites; however, because these activities were brief relative to the duration of the study, sufficient data were collected during unimpacted periods to allow for the following conclusions to be made. Water budgets developed for Boggy Marsh and the Lyonia large wetland showed strong similarity between the flux terms of rainfall, evaporation, net change in storage, and the net ground-water exchange residual. Runoff was assumed to be negligible. Of the total annual flux at Boggy Marsh, rainfall accounted for 45 percent; evaporation accounted for 25 percent; net change in storage accounted for 25 percent; and the net residual accounted for 5 percent. At the Lyonia large wetland, rainfall accounted for 44 percent; evaporation accounted for 29 percent; net change in storage accounted for 21 percent; and the net residual accounted for 6 percent of the total annual flux. Wetland storage and ground-water exchange were important when compared to the total water budget at both wetlands. Even

  11. Mechanism of shallow disrupted slide induced by extreme rainfall

    Science.gov (United States)

    Igwe, O.; Fukuoka, H.

    2010-12-01

    On July 16, 2010, extreme rainfall attacked western Japan and it caused very intense rainfall in Shobara city, Hiroshima prefecture, Japan. This rainfall induced hundreds of shallow disrupted slides and many of those became debris flows. One of this debris flows attacked a house standing in front of the exit of a channel, and claimed a resident’s life. Western Japan had repeatedly similar disasters in the past. Last event took place from July 19 to 26, 2009, when western Japan had a severe rainstorms and caused floods and landslides. Most of the landslides are debris slide - debris flows. Most devastated case took place in Hofu city, Japan. On July 21, extremely intense rainstorm caused numerous debris flows and mud flows in the hillslopes. Some of the debris flows destroyed residential houses and home for elderly people, and finally killed 14 residents. One of the unusual feature of both disaster was that landslides are distributed in very narrow area. In the 2010 Shobara city disaster, all of the landslides were distributed in 5 km x 3 km, and in the 2009 Hofu city disaster, most devastated zone of landslides were 10 km x 5 km. Rain radars of Meteorological Agency of Government of Japan detected the intense rainfall, however, the spatial resolution is usually larger than 5 km and the disaster area is too small to predict landslides nor issue warning. Furthermore, it was found that the growth rate of baby clouds was very quick. The geology of both areas are rhyolite (Shobara) and granite (Hofu), so the areal assessment of landslide hazard should be prepared before those intense rainfall will come. As for the Hofu city case, it was proved that debris flows took place in the high precipitation area and covered by covered by weathered granite sands and silts which is called “masa". This sands has been proved susceptible against landslides under extreme rainfall conditions. However, the transition from slide - debris flow process is not well revealed, except

  12. Impact of rainfall pattern on interrill erosion process

    Science.gov (United States)

    The impact of rainfall pattern on the interrill erosion process is not fully understood despite its importance. Systematic rainfall simulation experiments involving different rain intensities, stages, intensity sequences, and surface cover conditions were conducted to investigate the impacts of rain...

  13. Strong Electroweak Symmetry Breaking

    CERN Document Server

    Grinstein, Benjamin

    2011-01-01

    Models of spontaneous breaking of electroweak symmetry by a strong interaction do not have fine tuning/hierarchy problem. They are conceptually elegant and use the only mechanism of spontaneous breaking of a gauge symmetry that is known to occur in nature. The simplest model, minimal technicolor with extended technicolor interactions, is appealing because one can calculate by scaling up from QCD. But it is ruled out on many counts: inappropriately low quark and lepton masses (or excessive FCNC), bad electroweak data fits, light scalar and vector states, etc. However, nature may not choose the minimal model and then we are stuck: except possibly through lattice simulations, we are unable to compute and test the models. In the LHC era it therefore makes sense to abandon specific models (of strong EW breaking) and concentrate on generic features that may indicate discovery. The Technicolor Straw Man is not a model but a parametrized search strategy inspired by a remarkable generic feature of walking technicolor,...

  14. Bias adjustment of infrared-based rainfall estimation using Passive Microwave satellite rainfall data

    Science.gov (United States)

    Karbalaee, Negar; Hsu, Kuolin; Sorooshian, Soroosh; Braithwaite, Dan

    2017-04-01

    This study explores using Passive Microwave (PMW) rainfall estimation for spatial and temporal adjustment of Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks-Cloud Classification System (PERSIANN-CCS). The PERSIANN-CCS algorithm collects information from infrared images to estimate rainfall. PERSIANN-CCS is one of the algorithms used in the Integrated Multisatellite Retrievals for GPM (Global Precipitation Mission) estimation for the time period PMW rainfall estimations are limited or not available. Continued improvement of PERSIANN-CCS will support Integrated Multisatellite Retrievals for GPM for current as well as retrospective estimations of global precipitation. This study takes advantage of the high spatial and temporal resolution of GEO-based PERSIANN-CCS estimation and the more effective, but lower sample frequency, PMW estimation. The Probability Matching Method (PMM) was used to adjust the rainfall distribution of GEO-based PERSIANN-CCS toward that of PMW rainfall estimation. The results show that a significant improvement of global PERSIANN-CCS rainfall estimation is obtained.

  15. Plasmons in strong superconductors

    International Nuclear Information System (INIS)

    Baldo, M.; Ducoin, C.

    2011-01-01

    We present a study of the possible plasmon excitations that can occur in systems where strong superconductivity is present. In these systems the plasmon energy is comparable to or smaller than the pairing gap. As a prototype of these systems we consider the proton component of Neutron Star matter just below the crust when electron screening is not taken into account. For the realistic case we consider in detail the different aspects of the elementary excitations when the proton, electron components are considered within the Random-Phase Approximation generalized to the superfluid case, while the influence of the neutron component is considered only at qualitative level. Electron screening plays a major role in modifying the proton spectrum and spectral function. At the same time the electron plasmon is strongly modified and damped by the indirect coupling with the superfluid proton component, even at moderately low values of the gap. The excitation spectrum shows the interplay of the different components and their relevance for each excitation modes. The results are relevant for neutrino physics and thermodynamical processes in neutron stars. If electron screening is neglected, the spectral properties of the proton component show some resemblance with the physical situation in high-T c superconductors, and we briefly discuss similarities and differences in this connection. In a general prospect, the results of the study emphasize the role of Coulomb interaction in strong superconductors.

  16. Rainfall spatiotemporal variability relation to wetlands hydroperiods

    Science.gov (United States)

    Serrano-Hidalgo, Carmen; Guardiola-Albert, Carolina; Fernandez-Naranjo, Nuria

    2017-04-01

    Doñana natural space (Southwestern Spain) is one of the largest protected wetlands in Europe. The wide marshes present in this natural space have such ecological value that this wetland has been declared a Ramsar reserve in 1982. Apart from the extensive marsh, there are also small lagoons and seasonally flooded areas which are likewise essential to maintain a wide variety of valuable habitats. Hydroperiod, the length of time each point remains flooded along an annual cycle, is a critical ecological parameter that shapes aquatic plants and animals distribution and determines available habitat for many of the living organisms in the marshes. Recently, there have been published two different works estimating the hydroperiod of Doñana lagoons with Landsat Time Series images (Cifuentes et al., 2015; Díaz-Delgado et al., 2016). In both works the flooding cycle hydroperiod in Doñana marshes reveals a flooding regime mainly driven by rainfall, evapotranspiration, topography and local hydrological management actions. The correlation found between rainfall and hydroperiod is studied differently in both works. While in one the rainfall is taken from one raingauge (Cifuentes et al., 2015), the one performed by Díaz-Delgado (2016) uses annual rainfall maps interpolated with the inverse of the distance method. The rainfall spatiotemporal variability in this area can be highly significant; however the amount of this importance has not been quantified at the moment. In the present work the geostatistical tool known as spatiotemporal variogram is used to study the rainfall spatiotemporal variability. The spacetime package implemented in R (Pebesma, 2012) facilities its computation from a high rainfall data base of more than 100 raingauges from 1950 to 2016. With the aid of these variograms the rainfall spatiotemporal variability is quantified. The principal aim of the present work is the study of the relation between the rainfall spatiotemporal variability and the

  17. Trends in Extreme Rainfall Events in Tasmania, Australia

    OpenAIRE

    Orpita U. Laz; Ataur Rahman

    2014-01-01

    Climate change will affect various aspects of hydrological cycle such as rainfall. A change in rainfall will affect flood magnitude and frequency in future which will affect the design and operation of hydraulic structures. In this paper, trends in subhourly, sub-daily, and daily extreme rainfall events from 18 rainfall stations located in Tasmania, Australia are examined. Two nonparametric tests (Mann-Kendall and Spearman’s Rho) are applied to detect trends at 10%, 5%, a...

  18. Investigating changes over time of annual rainfall in Zimbabwe

    Directory of Open Access Journals (Sweden)

    D. Mazvimavi

    2010-12-01

    Full Text Available There is increasing concern in southern Africa about the possible decline of rainfall as a result of global warming. Some studies concluded that average rainfall in Zimbabwe had declined by 10% or 100 mm during the last 100 years. This paper investigates the validity of the assumption that rainfall is declining in Zimbabwe. Time series of annual rainfall, and total rainfall for (a the early part of the rainy season, October-November-December (OND, and (b the mid to end of the rainy season, January-February-March (JFM are analysed for the presence of trends using the Mann-Kendall test, and for the decline or increase during years with either high or low rainfall using quantile regression analysis. The Pettitt test has also been utilized to examine the possible existence of change or break-points in the rainfall time series. The analysis has been done for 40 rainfall stations with records starting during the 1892–1940 period and ending in 2000, and representative of all the rainfall regions.

    The Mann-Kendal test did not identify a significant trend at all the 40 stations, and therefore there is no proof that the average rainfall at each of these stations has changed. Quantile regression analysis revealed a decline in annual rainfall less than the tenth percentile at only one station, and increasing of rainfall greater than the ninetieth percentile at another station. All the other stations had no changes over time in both the low and high rainfall at the annual interval. Climate change effects are therefore not yet statistically significant within time series of total seasonal and annual rainfall in Zimbabwe. The general perception about declining rainfall is likely due to the presence of multidecadal variability characterized by bunching of years with above (e.g. 1951–1958, 1973–1980 and below (e.g. 1959–1972, 1982–1994 average rainfall.

  19. Rainfall Patterns and U.S. Migration from Rural Mexico.

    Science.gov (United States)

    Hunter, Lori M; Murray, Sheena; Riosmena, Fernando

    2013-12-01

    In many rural regions of developing countries, natural resource dependency means changes in climate patterns hold tremendous potential to impact livelihoods. When environmentally-based livelihood options are constrained, migration can become an important adaptive strategy. Using data from the Mexican Migration Project, we model U.S. emigration from rural communities as related to community, household and climate factors. The results suggest that households subjected to recent drought conditions are far more likely to send a U.S. migrant, but only in communities with strong migration histories. In regions lacking such social networks, rainfall deficits actually reduce migration propensities, perhaps reflecting constraints in the ability to engage in migration as a coping strategy. Policy implications emphasize diversification of rural Mexican livelihoods in the face of contemporary climate change.

  20. Soil seal development under simulated rainfall: Structural, physical and hydrological dynamics

    Science.gov (United States)

    Armenise, Elena; Simmons, Robert W.; Ahn, Sujung; Garbout, Amin; Doerr, Stefan H.; Mooney, Sacha J.; Sturrock, Craig J.; Ritz, Karl

    2018-01-01

    contrasting behaviour was related to different dynamics and processes of seal formation which depended on the soil properties. The impact of rainfall-induced surface sealing on the hydrological behaviour of soil (as represented by WDTP and Kun) was rapid and substantial: an average 60% reduction in Kun occurred for all soils between 2 and 9 min rainfall, and water repellent surfaces were identified for SZL and ZCL. This highlights that the condition of the immediate surface of agricultural soils involving rainfall-induced structural seals has a strong impact in the overall ability of soil to function as water reservoir.

  1. Soil seal development under simulated rainfall: Structural, physical and hydrological dynamics.

    Science.gov (United States)

    Armenise, Elena; Simmons, Robert W; Ahn, Sujung; Garbout, Amin; Doerr, Stefan H; Mooney, Sacha J; Sturrock, Craig J; Ritz, Karl

    2018-01-01

    . This contrasting behaviour was related to different dynamics and processes of seal formation which depended on the soil properties. The impact of rainfall-induced surface sealing on the hydrological behaviour of soil (as represented by WDTP and K un ) was rapid and substantial: an average 60% reduction in K un occurred for all soils between 2 and 9 min rainfall, and water repellent surfaces were identified for SZL and ZCL. This highlights that the condition of the immediate surface of agricultural soils involving rainfall-induced structural seals has a strong impact in the overall ability of soil to function as water reservoir.

  2. Mapping monthly rainfall erosivity in Europe.

    Science.gov (United States)

    Ballabio, Cristiano; Borrelli, Pasquale; Spinoni, Jonathan; Meusburger, Katrin; Michaelides, Silas; Beguería, Santiago; Klik, Andreas; Petan, Sašo; Janeček, Miloslav; Olsen, Preben; Aalto, Juha; Lakatos, Mónika; Rymszewicz, Anna; Dumitrescu, Alexandru; Tadić, Melita Perčec; Diodato, Nazzareno; Kostalova, Julia; Rousseva, Svetla; Banasik, Kazimierz; Alewell, Christine; Panagos, Panos

    2017-02-01

    Rainfall erosivity as a dynamic factor of soil loss by water erosion is modelled intra-annually for the first time at European scale. The development of Rainfall Erosivity Database at European Scale (REDES) and its 2015 update with the extension to monthly component allowed to develop monthly and seasonal R-factor maps and assess rainfall erosivity both spatially and temporally. During winter months, significant rainfall erosivity is present only in part of the Mediterranean countries. A sudden increase of erosivity occurs in major part of European Union (except Mediterranean basin, western part of Britain and Ireland) in May and the highest values are registered during summer months. Starting from September, R-factor has a decreasing trend. The mean rainfall erosivity in summer is almost 4 times higher (315MJmmha -1 h -1 ) compared to winter (87MJmmha -1 h -1 ). The Cubist model has been selected among various statistical models to perform the spatial interpolation due to its excellent performance, ability to model non-linearity and interpretability. The monthly prediction is an order more difficult than the annual one as it is limited by the number of covariates and, for consistency, the sum of all months has to be close to annual erosivity. The performance of the Cubist models proved to be generally high, resulting in R 2 values between 0.40 and 0.64 in cross-validation. The obtained months show an increasing trend of erosivity occurring from winter to summer starting from western to Eastern Europe. The maps also show a clear delineation of areas with different erosivity seasonal patterns, whose spatial outline was evidenced by cluster analysis. The monthly erosivity maps can be used to develop composite indicators that map both intra-annual variability and concentration of erosive events. Consequently, spatio-temporal mapping of rainfall erosivity permits to identify the months and the areas with highest risk of soil loss where conservation measures should be

  3. Rainfall interception of three trees in Oakland, California

    Science.gov (United States)

    Qingfu Xiao; E. Gregory McPherson

    2011-01-01

    A rainfall interception study was conducted in Oakland, California to determine the partitioning of rainfall and the chemical composition of precipitation, throughfall, and stemflow. Rainfall interception measurements were conducted on a gingko (Ginkgo biloba) (13.5 m tall deciduous tree), sweet gum (Liquidambar styraciflua) (8...

  4. Some characteristics of very heavy rainfall over Orissa during ...

    Indian Academy of Sciences (India)

    Orissa is one of the most flood prone states of India. The floods in Orissa mostly occur during monsoon season due to very heavy rainfall caused by synoptic scale monsoon disturbances. Hence a study is undertaken to find out the characteristic features of very heavy rainfall (24 hours rainfall. ≥ 125mm) over Orissa during ...

  5. RAINFALL-RUNOFF MODELING IN THE TURKEY RIVER USING ...

    African Journals Online (AJOL)

    2015-01-15

    Jan 15, 2015 ... a logical relationship with one and two days ago flow rate and one, two and three days ago rainfall values. ... back propagation artificial neural network (BPANN) to simulate rainfall-runoff process for two sub-basins of ... [6] used ANN and fuzzy logic for predicting event based rainfall runoff and tested these.

  6. Effect of rainfall variability on grassland herbage production and ...

    African Journals Online (AJOL)

    Even though rainfall amount influences herbage production, there is a wide range outside which there can be depression of forage dry matter yield on the Accra plains. Low rainfall amount does not seem to depress livestock numbers but may affect the performance of individual animals. However, very heavy rainfall may ...

  7. Gridded daily Indian monsoon rainfall for 14 seasons: Merged ...

    Indian Academy of Sciences (India)

    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 ...

  8. Ostrich recruitment dynamics in relation to rainfall in the Mara ...

    African Journals Online (AJOL)

    Animal population dynamics can be driven by rainfall variability through its influence on habitat suitability, availability and nutritional sufficiency of forage. To understand how rainfall influences ostriches, we related changes in ostrich recruitment in the Mara–Serengeti ecosystem to rainfall. Over a 15-year period, monthly ...

  9. Urban Run-off Volumes Dependency on Rainfall Measurement Method

    DEFF Research Database (Denmark)

    Pedersen, L.; Jensen, N. E.; Rasmussen, Michael R.

    2005-01-01

    suggests that rainfall needs to be measured with a much higher spatial resolution (Jensen and Pedersen, 2004). This paper evaluates the impact of using high-resolution rainfall information from weather radar compared to the conventional single gauge approach. The radar rainfall in three different...

  10. Variations in the Statistical Measures of Mean Rainfall | Egbuniwe ...

    African Journals Online (AJOL)

    Rainfall records are required for planning and development of water resources projects. Long term averages of rainfall are often needed. Decisions often have to be made with short term records, as long term rainfall records are not available for most parts of Nigeria. This study describes variations in some statistical ...

  11. Cascade rainfall disaggregation application in U.S. Central Plains

    Science.gov (United States)

    Hourly rainfall are increasingly used in complex, process-based simulations of the environment. Long records of daily rainfall are common, but long continuous records of hourly rainfall are rare and must be developed. A Multiplicative Random Cascade (MRC) model is proposed to disaggregate observed d...

  12. Rainfall Variability and Agricultural Vulnerability in the Amhara ...

    African Journals Online (AJOL)

    Surprisingly, however, the relationships between rainfall variability and fluctuations in agricultural production at regional and sub-regional scales have not been studied in detail. The objective of this study is to analyze rainfall variability and trends, and examine vulnerability of food grain production to rainfall variability in the ...

  13. Effect of rainfall on cropping pattern in mid Himalayan region ...

    African Journals Online (AJOL)

    The analysis of effect of rainfall during the last 20 years is needed to evaluate cropping pattern in the rain-fed region. In this study, trends in annual, seasonal and monthly rainfall of district of Himachal Pradesh in India over the past 20 years were examined. The annual rainfall varies from 863.3 to 1470.0 mm. During the ...

  14. Investigation of the influence of Atlantic ocean on rainfall variability ...

    African Journals Online (AJOL)

    The SVD analysis on the anomalous JJAS rainfall and anomalous Sea Surface Temperature (SST) in the Atlantic Ocean reveals two dominant coupled modes. The first couple mode that dominates the covariability between the anomalous rainfall and the SST reveals positive covariability between anomalous rainfall in ...

  15. The changing rainfall pattern and its implication for flood frequency ...

    African Journals Online (AJOL)

    The study deals with analysis of recent changes in the characteristics of extreme rainfall and their implication for flood frequency in Makurdi. Data on extreme daily rainfall, evapotranspiration and flood occurrences were collected for analysis. The annual rainfall was analysed for trends using spearman rank correlation ...

  16. Estimating Rainfall in Rodrigues by Geostatistics: (b) Application ...

    African Journals Online (AJOL)

    The previous paper described the kriging method and its possible applications. This paper checks whether kriging may be used to estimate rainfall. Four test stations were selected in Rodrigues. Rainfall data from surrounding stations were used to estimate rainfall at these stations, after first establishing a suitable ...

  17. A comparison of spatial rainfall estimation techniques: a case study ...

    African Journals Online (AJOL)

    Many hydrological models for watershed management and planning require rainfall as an input in a continuous format. This study analyzed four different rainfall interpolation techniques in Nyando river basin, Kenya. Interpolation was done for a period of 30 days using 19 rainfall stations. Two geostatistical interpolation ...

  18. Identification of homogeneous rainfall regimes in parts of Western ...

    Indian Academy of Sciences (India)

    Therefore, it is essential to understand rainfall distribution and its variation in relevance to such activities. ... puted differ from that of normal rainfall values reported by IMD as the length of the data record differs for .... sharp decrease in the rainfall value corresponding to the fall in elevation. It can be inferred that, the rise in the ...

  19. Rainfall intensity characteristics at coastal and high altitude stations ...

    Indian Academy of Sciences (India)

    a given amount of rain occurs is important because heavier rainfall leads to greater runoff, greater soil erosion and less infiltration into the water table. A knowledge of rainfall intensity therefore becomes. Keywords. Rainfall intensity; Kerala; cumulative distribution. J. Earth Syst. Sci. 116, No. 5, October 2007, pp. 451–463.

  20. Rainfall reliability, drought and flood vulnerability in Botswana ...

    African Journals Online (AJOL)

    Rainfall data from 14 stations (cities, towns and major villages) spanning 26 years (1970 to 1995) were used to calculate reliability and vulnerability of rainfall in Botswana. Time series data for 72 years were generated from the long-term rainfall gauging stations and the number of wet and dry years determined. Apart from ...

  1. Rainfall Downscaling Conditional on Upper-air Variables: Assessing Rainfall Statistics in a Changing Climate

    Science.gov (United States)

    Langousis, Andreas; Deidda, Roberto; Marrocu, Marino; Kaleris, Vassilios

    2014-05-01

    Due to its intermittent and highly variable character, and the modeling parameterizations used, precipitation is one of the least well reproduced hydrologic variables by both Global Climate Models (GCMs) and Regional Climate Models (RCMs). This is especially the case at a regional level (where hydrologic risks are assessed) and at small temporal scales (e.g. daily) used to run hydrologic models. In an effort to remedy those shortcomings and assess the effect of climate change on rainfall statistics at hydrologically relevant scales, Langousis and Kaleris (2013) developed a statistical framework for simulation of daily rainfall intensities conditional on upper air variables. The developed downscaling scheme was tested using atmospheric data from the ERA-Interim archive (http://www.ecmwf.int/research/era/do/get/index), and daily rainfall measurements from western Greece, and was proved capable of reproducing several statistical properties of actual rainfall records, at both annual and seasonal levels. This was done solely by conditioning rainfall simulation on a vector of atmospheric predictors, properly selected to reflect the relative influence of upper-air variables on ground-level rainfall statistics. In this study, we apply the developed framework for conditional rainfall simulation using atmospheric data from different GCM/RCM combinations. This is done using atmospheric data from the ENSEMBLES project (http://ensembleseu.metoffice.com), and daily rainfall measurements for an intermediate-sized catchment in Italy; i.e. the Flumendosa catchment. Since GCM/RCM products are suited to reproduce the local climatology in a statistical sense (i.e. in terms of relative frequencies), rather than ensuring a one-to-one temporal correspondence between observed and simulated fields (i.e. as is the case for ERA-interim reanalysis data), we proceed in three steps: a) we use statistical tools to establish a linkage between ERA-Interim upper-air atmospheric forecasts and

  2. Strong-coupling approximations

    International Nuclear Information System (INIS)

    Abbott, R.B.

    1984-03-01

    Standard path-integral techniques such as instanton calculations give good answers for weak-coupling problems, but become unreliable for strong-coupling. Here we consider a method of replacing the original potential by a suitably chosen harmonic oscillator potential. Physically this is motivated by the fact that potential barriers below the level of the ground-state energy of a quantum-mechanical system have little effect. Numerically, results are good, both for quantum-mechanical problems and for massive phi 4 field theory in 1 + 1 dimensions. 9 references, 6 figures

  3. Strong interaction and QFD

    International Nuclear Information System (INIS)

    Ebata, T.

    1981-01-01

    With an assumed weak multiplet structure for bosonic hadrons, which is consistent with the ΔI = 1/2 rule, it is shown that the strong interaction effective hamiltonian is compatible with the weak SU(2) x U(1) gauge transformation. Especially the rho-meson transforms as a triplet under SU(2)sub(w), and this is the origin of the rho-photon analogy. It is also shown that the existence of the non-vanishing Cabibbo angle is a necessary condition for the absence of the exotic hadrons. (orig.)

  4. Improving the Quality of Extreme Precipitation Estimates Using Satellite Passive Microwave Rainfall Retrievals

    Science.gov (United States)

    Petkovic, Veljko

    Satellite rainfall estimates are invaluable in assessing global precipitation. As a part of the Global Precipitation Measurement (GPM) mission, a constellation of orbiting sensors, dominated by passive microwave imagers, provides a full coverage of the planet approximately every 2-3 hours. Several decades of development have resulted in passive microwave rainfall retrievals that are indispensable in addressing global precipitation climatology. However, this prominent achievement is often overshadowed by the retrieval's performance at finer spatial and temporal scales, where large variability in cloud morphology poses an obstacle for accurate rainfall measurements. This is especially true over land, where rainfall estimates are based on an observed mean relationship between high frequency (e.g., 89 GHz) brightness temperature (Tb) depression (i.e., the ice-scattering signature) and rainfall rate. In the first part of this study, an extreme precipitation event that caused historical flooding over south-east Europe is analyzed using the GPM constellation. Performance of the rainfall retrieval is evaluated against ground radar and gage reference. It is concluded that satellite observations fully address the temporal evolution of the event but greatly underestimate total rainfall accumulation (by factor of 2.5). A primary limitation of the rainfall algorithm is found to be its inability to recognize variability in precipitating system structure. This variability is closely related to the structure of the precipitation regime and the large-scale environment. To address this influence of rainfall physics on the overall retrieval bias, the second part of this study utilizes TRMM radar (PR) and radiometer (TMI) observations to first confirm that the Tb-to-rain-rate relationship is governed by the amount of ice in the atmospheric column. Then, using the Amazon and Central African regions as testbeds, it demonstrates that the amount of ice aloft is strongly linked to a

  5. Development and application of artificial rainfall device

    International Nuclear Information System (INIS)

    Gao Xiaomei; Li Zhaolin; Jia Xue; Tadatoshi Yamamoto; Shinichi Takebe

    2000-01-01

    An artificial sprinkling simulation device was designed and developed to be used for radioactive nuclides migration tests. In this device water drops are sprinkled through medical syringe needles which vibrate along a circle. After several year operation at the field test site, it was demonstrated that this device is stable and sprinkling homogeneous, with the rainfall intensity from 2 mm/h to 100 mm/h and the low limit of 2 mm/h. Compared with spraying nozzle, it is easy to control the rainfall quantity and sprinkling area, and the evaporation loss is small. The device can meet the requirement of radioactive nuclide migration test and may also be used for other purpose

  6. Strong Coupling Holography

    CERN Document Server

    Dvali, Gia

    2009-01-01

    We show that whenever a 4-dimensional theory with N particle species emerges as a consistent low energy description of a 3-brane embedded in an asymptotically-flat (4+d)-dimensional space, the holographic scale of high-dimensional gravity sets the strong coupling scale of the 4D theory. This connection persists in the limit in which gravity can be consistently decoupled. We demonstrate this effect for orbifold planes, as well as for the solitonic branes and string theoretic D-branes. In all cases the emergence of a 4D strong coupling scale from bulk holography is a persistent phenomenon. The effect turns out to be insensitive even to such extreme deformations of the brane action that seemingly shield 4D theory from the bulk gravity effects. A well understood example of such deformation is given by large 4D Einstein term in the 3-brane action, which is known to suppress the strength of 5D gravity at short distances and change the 5D Newton's law into the four-dimensional one. Nevertheless, we observe that the ...

  7. Spatial variability of extreme rainfall at radar subpixel scale

    Science.gov (United States)

    Peleg, Nadav; Marra, Francesco; Fatichi, Simone; Paschalis, Athanasios; Molnar, Peter; Burlando, Paolo

    2018-01-01

    Extreme rainfall is quantified in engineering practice using Intensity-Duration-Frequency curves (IDF) that are traditionally derived from rain-gauges and more recently also from remote sensing instruments, such as weather radars. These instruments measure rainfall at different spatial scales: rain-gauge samples rainfall at the point scale while weather radar averages precipitation on a relatively large area, generally around 1 km2. As such, a radar derived IDF curve is representative of the mean areal rainfall over a given radar pixel and neglects the within-pixel rainfall variability. In this study, we quantify subpixel variability of extreme rainfall by using a novel space-time rainfall generator (STREAP model) that downscales in space the rainfall within a given radar pixel. The study was conducted using a unique radar data record (23 years) and a very dense rain-gauge network in the Eastern Mediterranean area (northern Israel). Radar-IDF curves, together with an ensemble of point-based IDF curves representing the radar subpixel extreme rainfall variability, were developed fitting Generalized Extreme Value (GEV) distributions to annual rainfall maxima. It was found that the mean areal extreme rainfall derived from the radar underestimate most of the extreme values computed for point locations within the radar pixel (on average, ∼70%). The subpixel variability of rainfall extreme was found to increase with longer return periods and shorter durations (e.g. from a maximum variability of 10% for a return period of 2 years and a duration of 4 h to 30% for 50 years return period and 20 min duration). For the longer return periods, a considerable enhancement of extreme rainfall variability was found when stochastic (natural) climate variability was taken into account. Bounding the range of the subpixel extreme rainfall derived from radar-IDF can be of major importance for different applications that require very local estimates of rainfall extremes.

  8. Impacts of Rainfall Variability and Expected Rainfall Changes on Cost-Effective Adaptation of Water Systems to Climate Change

    NARCIS (Netherlands)

    Pol, van der T.D.; Ierland, van E.C.; Gabbert, S.G.M.; Weikard, H.P.; Hendrix, E.M.T.

    2015-01-01

    Stormwater drainage and other water systems are vulnerable to changes in rainfall and runoff and need to be adapted to climate change. This paper studies impacts of rainfall variability and changing return periods of rainfall extremes on cost-effective adaptation of water systems to climate change

  9. Event-based stochastic point rainfall resampling for statistical replication and climate projection of historical rainfall series

    Science.gov (United States)

    Thorndahl, Søren; Korup Andersen, Aske; Badsberg Larsen, Anders

    2017-09-01

    Continuous and long rainfall series are a necessity in rural and urban hydrology for analysis and design purposes. Local historical point rainfall series often cover several decades, which makes it possible to estimate rainfall means at different timescales, and to assess return periods of extreme events. Due to climate change, however, these series are most likely not representative of future rainfall. There is therefore a demand for climate-projected long rainfall series, which can represent a specific region and rainfall pattern as well as fulfil requirements of long rainfall series which includes climate changes projected to a specific future period. This paper presents a framework for resampling of historical point rainfall series in order to generate synthetic rainfall series, which has the same statistical properties as an original series. Using a number of key target predictions for the future climate, such as winter and summer precipitation, and representation of extreme events, the resampled historical series are projected to represent rainfall properties in a future climate. Climate-projected rainfall series are simulated by brute force randomization of model parameters, which leads to a large number of projected series. In order to evaluate and select the rainfall series with matching statistical properties as the key target projections, an extensive evaluation procedure is developed.

  10. Investigating recent trends in the rainfall structure: an overview across Portugal

    Science.gov (United States)

    de Lima, M. I. P.; Coelho, M. F. E. S.; Carvalho, S. C. P.; de Lima, J. L. M. P.

    2009-09-01

    The spatial and temporal structure of rain, which typically exhibits extreme variability, is a core issue in studies that span a number of research areas, e.g. hydrology, hydraulics, environment, energy, economics, society. The interest in this process demands its comprehensive study and characterization at a variety of space- and time-scales. Local studies of the rainfall climate can play an important role as they may contribute to characterizing rainfall. In this work the study area is mainland Portugal. Mainland Portugal is located in the transitional region between the sub-tropical anticyclone and the sub-polar depression zones. The characteristics of global circulation (specifically the Atlantic origin of many synoptic disturbances such as seasonal movements of the Azores high pressure system) in the context of regional geography (e.g. latitude, orography, oceanic and continental influences) greatly influence the spatial distribution of precipitation over the territory. The climatic variables exhibit strong north-south and west-east gradients, and precipitation also exhibits strong seasonal variability. The dominant climate in mainland Portugal is mild Mediterranean with a warm, dry summer period. These characteristics are more pronounced in the south, where the climate is sometimes classified as semi-arid. These regions are also well known for their vulnerability to climate variability. Several studies have reported increased rainfall variability in recent years, largely on the basis of annual and monthly point rainfall data, and for different geographical locations across the Iberian Peninsula, including Portugal. The main aim of this work, which complements those trend studies, is to contribute to identifying and clarifying recent changes in rain variability in Portugal by analysing trends in the small-scale temporal behaviour and statistics of this process. Thus the analyses reported here concentrate on the statistics of short-term rainfall events. The

  11. Trend analysis of long-term rainfall

    Directory of Open Access Journals (Sweden)

    Fabio de Oliveira Sanches

    2013-12-01

    Full Text Available In the Pampas Region in the southwest of the State of Rio Grande do Sul, there are areas that show fragility in relation to soil and climatic characteristics. The sandy areas of this region have attracted special attention in the recent decades due to historical, socio economic and environmental issues. An increase in the amount of sand, or “sandization”, occurred due to natural phenomena such as rainfall and wind. Therefore, the sandization process could be influenced by an increase of precipitation in the area. The goal of this work was to analyze precipitation during different time periods in Alegrete, Rio Grande do Sul, from 1928 to 2009 in order to identify evidence of changes in rainfall behavior. Rainfall data from the Brazilian National Water Agency (Portuguese acronym ANA provided by the system hidroweb (http://hidroweb.ana.gov.br were analyzed. After the data were organized on total monthly, trimestral and annual values, they were analyzed for their linear trend over time. The Mann-Kendall test was used to quantitatively evaluate positive and negative trends; however, the data did not provide evidence of climatic changes, but rather of normal random weather events during the time period studied.

  12. Runoff generation in a Mediterranean semi-arid landscape: Thresholds, scale, rainfall and catchment characteristics

    Science.gov (United States)

    Ries, Fabian; Schmidt, Sebastian; Sauter, Martin; Lange, Jens

    2016-04-01

    Surface runoff acts as an integrated response of catchment characteristics and hydrological processes. In the Eastern Mediterranean region, a lack of runoff data has hindered a better understanding of runoff generation processes on the catchment scale, despite the importance of surface runoff as a water resource or flood hazard. Our main aim was to identify and explain differences in catchment runoff reactions across a variety of scales. Over a period of five years, we observed runoff in ephemeral streams of seven watersheds with sizes between 3 and 129 km2. Landuse and surface cover types (share of vegetation, bare soil and rock outcrops) were derived from aerial images by objective classification techniques. Using data from a dense rainfall network we analysed the effects of scale, catchment properties and aridity on runoff generation. Thereby we extracted rainfall and corresponding runoff events from our time-series to calculate event based rainfall characteristics and catchment runoff coefficients. Soil moisture observations provided additional information on antecedent moisture conditions, infiltration characteristics and the evolution of saturated areas. In contrast to the prevailing opinion that the proportion of Hortonian overland flow increases with aridity, we found that in our area the largest share (> 95 %) of runoff is generated by saturation excess overland flow in response to long lasting, rainfall events of high amount. This was supported by a strong correlation between event runoff and precipitation totals. Similar rainfall thresholds (50 mm) for runoff generation were observed in all investigated catchments. No scale effects on runoff coefficients were found; instead we identified up to three-fold runoff coefficients in catchments with larger extension of arid areas, higher percentage of rock outcrops and urbanization. Comparing two headwater catchments with noticeable differences in extent of olive orchards, no difference in runoff generation was

  13. EVALUATION OF RAINFALL-RUNOFF EROSIVITY FACTOR FOR CAMERON HIGHLAND, PAHANG, MALAYSIA

    Directory of Open Access Journals (Sweden)

    Abdulkadir Taofeeq Sholagberu

    2016-07-01

    Full Text Available Rainfall-runoff is the active agent of soil erosion which often resulted in land degradation and water quality deterioration. Its aggressiveness to induce erosion is usually termed as rainfall erosivity index or factor (R. R-factor is one of the factors to be parameterized in the evaluation of soil loss using the Universal Soil Loss Equation and its reversed versions (USLE/RUSLE. The computation of accurate R-factor for a particular watershed requires high temporal resolution rainfall (pluviograph data with less than 30-minutes intensities for at least 20 yrs, which is available only in a few regions of the world. As a result, various simplified models have been proposed by researchers to evaluate R-factor using readily available daily, monthly or annual precipitation data. This study is thus aimed at estimating R-factor and to establish an approximate relationship between R-factor and rainfall for subsequent usage in the estimation of soil loss in Cameron highlands watershed. The results of the analysis showed that the least and peak (critical R-factors occurred in the months of January and April with 660.82 and 2399.18 MJ mm ha-1 h-1year-1 respectively. Also, it was observed that erosivity power starts to increase from the month of January through April before started falling in the month of July. The monthly and annual peaks (critical periods may be attributed to increased rainfall amount due to climate change which in turn resulted to increased aggressiveness of rains to cause erosion in the study area. The correlation coefficient of 0.985 showed that there was a strong relationship rainfall and R-factor.

  14. Month-to-month variability of Indian summer monsoon rainfall in 2016: role of the Indo-Pacific climatic conditions

    Science.gov (United States)

    Chowdary, Jasti S.; Srinivas, G.; Du, Yan; Gopinath, K.; Gnanaseelan, C.; Parekh, Anant; Singh, Prem

    2018-03-01

    Indian summer monsoon (ISM) rainfall during 2016 exhibited a prominent month-to-month fluctuations over India, with below normal rainfall in June and August and above normal rainfall in July. The factors determining the month-to-month fluctuations in ISM rainfall during 2016 are investigated with main focus on the Indo-Pacific climatic anomalies. Warm sea surface temperature (SST) anomalies associated with super El Niño 2015 disappeared by early summer 2016 over the central and eastern Pacific. On the other hand, negative Indian Ocean dipole (IOD) like SST anomaly pattern over the equatorial Indian Ocean and anomalous anticyclonic circulation over the western North Pacific (WNP) are reported in summer 2016 concurrently with decaying El Niño/developing La Niña phase. Observations revealed that the low rainfall over central north India in June is due to moisture divergence caused by the westward extension of ridge corresponding to WNP anticyclone and subsidence induced by local Hadley cell partly related to negative IOD. Low level convergence of southeasterly wind from Bay of Bengal associated with weak WNP anticyclone and northwesterly wind corresponding to anticyclonic circulation over the northwest India remarkably contributed to positive rainfall in July over most of the Indian subcontinent. While reduced rainfall over the Indian subcontinent in August 2016 is associated with the anomalous moisture transport from ISM region to WNP region, in contrast to July, due to local cyclogenesis corroborated by number of tropical cyclones in the WNP. In addition to this, subsidence related to strong convection supported by cyclonic circulation over the WNP also resulted in low rainfall over the ISM region. Coupled General Circulation model sensitivity experiments confirmed that strong convective activities associated with cyclonic circulation over the WNP is primarily responsible for the observed negative ISM rainfall anomalies in August 2016. It is noted that the Indo

  15. LIGO: The strong belief

    CERN Multimedia

    Antonella Del Rosso

    2016-01-01

    Twenty years of designing, building and testing a number of innovative technologies, with the strong belief that the endeavour would lead to a historic breakthrough. The Bulletin publishes an abstract of the Courier’s interview with Barry Barish, one of the founding fathers of LIGO.   The plots show the signals of gravitational waves detected by the twin LIGO observatories at Livingston, Louisiana, and Hanford, Washington. (Image: Caltech/MIT/LIGO Lab) On 11 February, the Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo collaborations published a historic paper in which they showed a gravitational signal emitted by the merger of two black holes. These results come after 20 years of hard work by a large collaboration of scientists operating the two LIGO observatories in the US. Barry Barish, Linde Professor of Physics, Emeritus at the California Institute of Technology and former Director of the Global Design Effort for the Internat...

  16. Deterministic Approach for Estimating Critical Rainfall Threshold of Rainfall-induced Landslide in Taiwan

    Science.gov (United States)

    Chung, Ming-Chien; Tan, Chih-Hao; Chen, Mien-Min; Su, Tai-Wei

    2013-04-01

    Taiwan is an active mountain belt created by the oblique collision between the northern Luzon arc and the Asian continental margin. The inherent complexities of geological nature create numerous discontinuities through rock masses and relatively steep hillside on the island. In recent years, the increase in the frequency and intensity of extreme natural events due to global warming or climate change brought significant landslides. The causes of landslides in these slopes are attributed to a number of factors. As is well known, rainfall is one of the most significant triggering factors for landslide occurrence. In general, the rainfall infiltration results in changing the suction and the moisture of soil, raising the unit weight of soil, and reducing the shear strength of soil in the colluvium of landslide. The stability of landslide is closely related to the groundwater pressure in response to rainfall infiltration, the geological and topographical conditions, and the physical and mechanical parameters. To assess the potential susceptibility to landslide, an effective modeling of rainfall-induced landslide is essential. In this paper, a deterministic approach is adopted to estimate the critical rainfall threshold of the rainfall-induced landslide. The critical rainfall threshold is defined as the accumulated rainfall while the safety factor of the slope is equal to 1.0. First, the process of deterministic approach establishes the hydrogeological conceptual model of the slope based on a series of in-situ investigations, including geological drilling, surface geological investigation, geophysical investigation, and borehole explorations. The material strength and hydraulic properties of the model were given by the field and laboratory tests. Second, the hydraulic and mechanical parameters of the model are calibrated with the long-term monitoring data. Furthermore, a two-dimensional numerical program, GeoStudio, was employed to perform the modelling practice. Finally

  17. Application of seasonal rainfall forecasts and satellite rainfall observations to crop yield forecasting for Africa

    Science.gov (United States)

    Greatrex, H. L.; Grimes, D. I. F.; Wheeler, T. R.

    2009-04-01

    Rain-fed agriculture is of utmost importance in sub-Saharan Africa; the FAO estimates that over 90% of food consumed in the region is grown in rain-fed farming systems. As the climate in sub-Saharan Africa has a high interannual variability, this dependence on rainfall can leave communities extremely vulnerable to food shortages, especially when coupled with a lack of crop management options. The ability to make a regional forecast of crop yield on a timescale of months would be of enormous benefit; it would enable both governmental and non-governmental organisations to be alerted in advance to crop failure and could facilitate national and regional economic planning. Such a system would also enable individual communities to make more informed crop management decisions, increasing their resilience to climate variability and change. It should be noted that the majority of crops in the region are rainfall limited, therefore the ability to create a seasonal crop forecast depends on the ability to forecast rainfall at a monthly or seasonal timescale and to temporally downscale this to a daily time-series of rainfall. The aim of this project is to develop a regional-scale seasonal forecast for sub-Saharan crops, utilising the General Large Area Model for annual crops (GLAM). GLAM would initially be driven using both dynamical and statistical seasonal rainfall forecasts to provide an initial estimate of crop yield. The system would then be continuously updated throughout the season by replacing the seasonal rainfall forecast with daily weather observations. TAMSAT satellite rainfall estimates are used rather than rain-gauge data due to the scarcity of ground based observations. An important feature of the system is the use of the geo-statistical method of sequential simulation to create an ensemble of daily weather inputs from both the statistical seasonal rainfall forecasts and the satellite rainfall estimates. This allows a range of possible yield outputs to be

  18. Automatic Extraction of High-Resolution Rainfall Series from Rainfall Strip Charts

    Science.gov (United States)

    Saa-Requejo, Antonio; Valencia, Jose Luis; Garrido, Alberto; Tarquis, Ana M.

    2015-04-01

    Soil erosion is a complex phenomenon involving the detachment and transport of soil particles, storage and runoff of rainwater, and infiltration. The relative magnitude and importance of these processes depends on a host of factors, including climate, soil, topography, cropping and land management practices among others. Most models for soil erosion or hydrological processes need an accurate storm characterization. However, this data are not always available and in some cases indirect models are generated to fill this gap. In Spain, the rain intensity data known for time periods less than 24 hours back to 1924 and many studies are limited by it. In many cases this data is stored in rainfall strip charts in the meteorological stations but haven't been transfer in a numerical form. To overcome this deficiency in the raw data a process of information extraction from large amounts of rainfall strip charts is implemented by means of computer software. The method has been developed that largely automates the intensive-labour extraction work based on van Piggelen et al. (2011). The method consists of the following five basic steps: 1) scanning the charts to high-resolution digital images, 2) manually and visually registering relevant meta information from charts and pre-processing, 3) applying automatic curve extraction software in a batch process to determine the coordinates of cumulative rainfall lines on the images (main step), 4) post processing the curves that were not correctly determined in step 3, and 5) aggregating the cumulative rainfall in pixel coordinates to the desired time resolution. A colour detection procedure is introduced that automatically separates the background of the charts and rolls from the grid and subsequently the rainfall curve. The rainfall curve is detected by minimization of a cost function. Some utilities have been added to improve the previous work and automates some auxiliary processes: readjust the bands properly, merge bands when

  19. Projected changes of rainfall event characteristics for the Czech Republic

    Directory of Open Access Journals (Sweden)

    Svoboda Vojtěch

    2016-12-01

    Full Text Available Projected changes of warm season (May–September rainfall events in an ensemble of 30 regional climate model (RCM simulations are assessed for the Czech Republic. Individual rainfall events are identified using the concept of minimum inter-event time and only heavy events are considered. The changes of rainfall event characteristics are evaluated between the control (1981–2000 and two scenario (2020–2049 and 2070–2099 periods. Despite a consistent decrease in the number of heavy rainfall events, there is a large uncertainty in projected changes in seasonal precipitation total due to heavy events. Most considered characteristics (rainfall event depth, mean rainfall rate, maximum 60-min rainfall intensity and indicators of rainfall event erosivity are projected to increase and larger increases appear for more extreme values. Only rainfall event duration slightly decreases in the more distant scenario period according to the RCM simulations. As a consequence, the number of less extreme heavy rainfall events as well as the number of long events decreases in majority of the RCM simulations. Changes in most event characteristics (and especially in characteristics related to the rainfall intensity depend on changes in radiative forcing and temperature for the future periods. Only changes in the number of events and seasonal total due to heavy events depend significantly on altitude.

  20. Tropical cyclone rainfall area controlled by relative sea surface temperature.

    Science.gov (United States)

    Lin, Yanluan; Zhao, Ming; Zhang, Minghua

    2015-03-12

    Tropical cyclone rainfall rates have been projected to increase in a warmer climate. The area coverage of tropical cyclones influences their impact on human lives, yet little is known about how tropical cyclone rainfall area will change in the future. Here, using satellite data and global atmospheric model simulations, we show that tropical cyclone rainfall area is controlled primarily by its environmental sea surface temperature (SST) relative to the tropical mean SST (that is, the relative SST), while rainfall rate increases with increasing absolute SST. Our result is consistent with previous numerical simulations that indicated tight relationships between tropical cyclone size and mid-tropospheric relative humidity. Global statistics of tropical cyclone rainfall area are not expected to change markedly under a warmer climate provided that SST change is relatively uniform, implying that increases in total rainfall will be confined to similar size domains with higher rainfall rates.

  1. Spatial Interpolation of Historical Seasonal Rainfall Indices over Peninsular Malaysia

    Science.gov (United States)

    Hassan, Zulkarnain; Haidir, Ahmad; Saad, Farah Naemah Mohd; Ayob, Afizah; Rahim, Mustaqqim Abdul; Ghazaly, Zuhayr Md.

    2018-03-01

    The inconsistency in inter-seasonal rainfall due to climate change will cause a different pattern in the rainfall characteristics and distribution. Peninsular Malaysia is not an exception for this inconsistency, in which it is resulting extreme events such as flood and water scarcity. This study evaluates the seasonal patterns in rainfall indices such as total amount of rainfall, the frequency of wet days, rainfall intensity, extreme frequency, and extreme intensity in Peninsular Malaysia. 40 years (1975-2015) data records have been interpolated using Inverse Distance Weighted method. The results show that the formation of rainfall characteristics are significance during the Northeast monsoon (NEM), as compared to Southwest monsoon (SWM). Also, there is a high rainfall intensity and frequency related to extreme over eastern coasts of Peninsula during the NEM season.

  2. Spatial Interpolation of Historical Seasonal Rainfall Indices over Peninsular Malaysia

    Directory of Open Access Journals (Sweden)

    Hassan Zulkarnain

    2018-01-01

    Full Text Available The inconsistency in inter-seasonal rainfall due to climate change will cause a different pattern in the rainfall characteristics and distribution. Peninsular Malaysia is not an exception for this inconsistency, in which it is resulting extreme events such as flood and water scarcity. This study evaluates the seasonal patterns in rainfall indices such as total amount of rainfall, the frequency of wet days, rainfall intensity, extreme frequency, and extreme intensity in Peninsular Malaysia. 40 years (1975-2015 data records have been interpolated using Inverse Distance Weighted method. The results show that the formation of rainfall characteristics are significance during the Northeast monsoon (NEM, as compared to Southwest monsoon (SWM. Also, there is a high rainfall intensity and frequency related to extreme over eastern coasts of Peninsula during the NEM season.

  3. STOCHASTIC GENERATION OF THE OCCURRENCE AND AMOUNT OF DAILY RAINFALL

    Directory of Open Access Journals (Sweden)

    M Al Baqui Barkotulla

    2010-09-01

    Full Text Available Rainfall is the main source of irrigation water in the northwest part of Bangladesh where the inhabitants derive their income primarily from farming. Stochastic rainfall models were concerned with the occurrence of wet day and depth of rainfall. The first order Markov chain model was used to simulate the sequence of rainfall occurrence using the method of transitional probability matrices, while daily rainfall amount was generated using a gamma distribution. The model parameters were estimated from historical rainfall records. The shape and scale parameters were estimated by moment method and hence it became possible to find the parameter values at the study area and then to generate synthetic sequences according to the gamma distribution. The parameters necessary for the whole generation include the means, variance or standard deviation and conditional probabilities of wet and dry days. Results obtained showed that the model could be used to generate rainfall data satisfactorily.

  4. Long range forecasting of summer monsoon rainfall from SST in the central equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Sadhuram, Y.; Murthy, T.V.R.

    southwest monsoon season (June- September). As India's economy mainly depends on agriculture, monsoon rainfall is very important for the country.Besidesagriculture,itis the mainsourceforfresh water to millions of people living in the country. Floods... and droughts associated with strong and weak monsoons greatly influence the economy of the country. Most of the droughts and floods are associated with EI-Nino and La- Nina respectively (Webster andYang3 and krishna Kumar et al\\. The relationship between ENSO...

  5. Simulation of extreme rainfall event of November 2009 over Jeddah, Saudi Arabia: the explicit role of topography and surface heating

    Science.gov (United States)

    Almazroui, Mansour; Raju, P. V. S.; Yusef, A.; Hussein, M. A. A.; Omar, M.

    2018-04-01

    In this paper, a nonhydrostatic Weather Research and Forecasting (WRF) model has been used to simulate the extreme precipitation event of 25 November 2009, over Jeddah, Saudi Arabia. The model is integrated in three nested (27, 9, and 3 km) domains with the initial and boundary forcing derived from the NCEP reanalysis datasets. As a control experiment, the model integrated for 48 h initiated at 0000 UTC on 24 November 2009. The simulated rainfall in the control experiment depicts in well agreement with Tropical Rainfall Measurement Mission rainfall estimates in terms of intensity as well as spatio-temporal distribution. Results indicate that a strong low-level (850 hPa) wind over Jeddah and surrounding regions enhanced the moisture and temperature gradient and created a conditionally unstable atmosphere that favored the development of the mesoscale system. The influences of topography and heat exchange process in the atmosphere were investigated on the development of extreme precipitation event; two sensitivity experiments are carried out: one without topography and another without exchange of surface heating to the atmosphere. The results depict that both surface heating and topography played crucial role in determining the spatial distribution and intensity of the extreme rainfall over Jeddah. The topography favored enhanced uplift motion that further strengthened the low-level jet and hence the rainfall over Jeddah and adjacent areas. On the other hand, the absence of surface heating considerably reduced the simulated rainfall by 30% as compared to the observations.

  6. Evaluation of TRMM 3B42 V7 Rainfall Product over the Oum Er Rbia Watershed in Morocco

    Directory of Open Access Journals (Sweden)

    Hamza Ouatiki

    2017-01-01

    Full Text Available In arid and semi-arid areas, rainfall is often characterized by a strong spatial and temporal variability. These environmental factors, combined with the sparsity of the measurement networks in developing countries, constitute real constraints for water resources management. In recent years, several spatial rainfall measurement sources have become available, such as TRMM data (Tropical Rainfall Measurement Mission. In this study, the TRMM 3B42 Version 7 product was evaluated using rain gauges measurements from 19 stations in the Oum-Er-Bia (OER basin located in the center of Morocco. The relevance of the TRMM product was tested by direct comparison with observations at different time scales (daily, monthly, and annual between 1998 and 2010. Results show that the satellite product provides poor estimations of rainfall at the daily time scale giving an average Pearson correlation coefficient (r of 0.2 and average Root Mean Square Error (RMSE of 10 mm. However, the accuracy of TRMM rainfall is improved when temporally averaged to monthly time scale (r of 0.8 and RMSE of 28 mm or annual time scale (r of 0.71 and RMSE of 157 mm. Moreover, improved correlation with observed data was obtained for data spatially averaged at the watershed scale. Therefore, at the monthly and annual time scales, TRMM data can be a useful source of rainfall data for water resources monitoring and management in ungauged basins in semi-arid regions.

  7. John Strong (1941 - 2006)

    CERN Multimedia

    Wickens, F

    Our friend and colleague John Strong was cruelly taken from us by a brain tumour on Monday 31st July, a few days before his 65th birthday John started his career working with a group from Westfield College, under the leadership of Ted Bellamy. He obtained his PhD and spent the early part of his career on experiments at Rutherford Appleton Laboratory (RAL), but after the early 1970s his research was focussed on experiments in CERN. Over the years he made a number of notable contributions to experiments in CERN: The Omega spectrometer adopted a system John had originally developed for experiments at RAL using vidicon cameras to record the sparks in the spark chambers; He contributed to the success of NA1 and NA7, where he became heavily involved in the electronic trigger systems; He was responsible for the second level trigger system for the ALEPH detector and spent five years leading a team that designed and built the system, which ran for twelve years with only minor interventions. Following ALEPH he tur...

  8. Stirring Strongly Coupled Plasma

    CERN Document Server

    Fadafan, Kazem Bitaghsir; Rajagopal, Krishna; Wiedemann, Urs Achim

    2009-01-01

    We determine the energy it takes to move a test quark along a circle of radius L with angular frequency w through the strongly coupled plasma of N=4 supersymmetric Yang-Mills (SYM) theory. We find that for most values of L and w the energy deposited by stirring the plasma in this way is governed either by the drag force acting on a test quark moving through the plasma in a straight line with speed v=Lw or by the energy radiated by a quark in circular motion in the absence of any plasma, whichever is larger. There is a continuous crossover from the drag-dominated regime to the radiation-dominated regime. In the crossover regime we find evidence for significant destructive interference between energy loss due to drag and that due to radiation as if in vacuum. The rotating quark thus serves as a model system in which the relative strength of, and interplay between, two different mechanisms of parton energy loss is accessible via a controlled classical gravity calculation. We close by speculating on the implicati...

  9. Strong-interaction nonuniversality

    International Nuclear Information System (INIS)

    Volkas, R.R.; Foot, R.; He, X.; Joshi, G.C.

    1989-01-01

    The universal QCD color theory is extended to an SU(3) 1 direct product SU(3) 2 direct product SU(3) 3 gauge theory, where quarks of the ith generation transform as triplets under SU(3)/sub i/ and singlets under the other two factors. The usual color group is then identified with the diagonal subgroup, which remains exact after symmetry breaking. The gauge bosons associated with the 16 broken generators then form two massive octets under ordinary color. The interactions between quarks and these heavy gluonlike particles are explicitly nonuniversal and thus an exploration of their physical implications allows us to shed light on the fundamental issue of strong-interaction universality. Nonuniversality and weak flavor mixing are shown to generate heavy-gluon-induced flavor-changing neutral currents. The phenomenology of these processes is studied, as they provide the major experimental constraint on the extended theory. Three symmetry-breaking scenarios are presented. The first has color breaking occurring at the weak scale, while the second and third divorce the two scales. The third model has the interesting feature of radiatively induced off-diagonal Kobayashi-Maskawa matrix elements

  10. Interception of rainfall and surface runoff in the Brazilian Cerrado

    Science.gov (United States)

    Tarso Oliveira, Paulo; Wendland, Edson; Nearing, Mark; Perea Martins, João

    2014-05-01

    CI. The average surface runoff under undisturbed Cerrado was less than 1% of the P, and did not have significant correlation (p > 0.05) with P, but had a significant correlation with maximum 30 minute rainfall intensity (I30). This low value for surface runoff indicates that the forest ?oor has a strong influence over surface runoff generation under undisturbed Cerrado. This process is poorly studied; however, we believe this can be a key to understanding the surface runoff generation under undisturbed Cerrado, and in other tropical vegetation, such as the Amazon rainforest.

  11. Rainfall thresholds for possible landslide occurrence in Italy

    Science.gov (United States)

    Peruccacci, Silvia; Brunetti, Maria Teresa; Gariano, Stefano Luigi; Melillo, Massimo; Rossi, Mauro; Guzzetti, Fausto

    2017-08-01

    The large physiographic variability and the abundance of landslide and rainfall data make Italy an ideal site to investigate variations in the rainfall conditions that can result in rainfall-induced landslides. We used landslide information obtained from multiple sources and rainfall data captured by 2228 rain gauges to build a catalogue of 2309 rainfall events with - mostly shallow - landslides in Italy between January 1996 and February 2014. For each rainfall event with landslides, we reconstructed the rainfall history that presumably caused the slope failure, and we determined the corresponding rainfall duration D (in hours) and cumulated event rainfall E (in mm). Adopting a power law threshold model, we determined cumulated event rainfall-rainfall duration (ED) thresholds, at 5% exceedance probability, and their uncertainty. We defined a new national threshold for Italy, and 26 regional thresholds for environmental subdivisions based on topography, lithology, land-use, land cover, climate, and meteorology, and we used the thresholds to study the variations of the rainfall conditions that can result in landslides in different environments, in Italy. We found that the national and the environmental thresholds cover a small part of the possible DE domain. The finding supports the use of empirical rainfall thresholds for landslide forecasting in Italy, but poses an empirical limitation to the possibility of defining thresholds for small geographical areas. We observed differences between some of the thresholds. With increasing mean annual precipitation (MAP), the thresholds become higher and steeper, indicating that more rainfall is needed to trigger landslides where the MAP is high than where it is low. This suggests that the landscape adjusts to the regional meteorological conditions. We also observed that the thresholds are higher for stronger rocks, and that forested areas require more rainfall than agricultural areas to initiate landslides. Finally, we

  12. The Saharan Air Layer as an Early Rainfall Season Suppressant in the Eastern Caribbean: The 2015 Puerto Rico Drought

    Science.gov (United States)

    Mote, Thomas L.; Ramseyer, Craig A.; Miller, Paul W.

    2017-10-01

    Eastern Puerto Rico and the surrounding Caribbean experienced a severe drought in 2015 that resulted in record-low reservoir and river levels. Rainfall deficits in April and May, which represent the period when the drought began, were more severe in 2015 than recent droughts of record. While El Niño has been associated with drought in the Caribbean, onset of the 2015 drought was strongly associated with lower-than-average values of a recently developed tool used by weather forecasters in San Juan, the Gálvez-Davison Index (GDI), which is used to measure the potential for thunderstorm development and rainfall. Persistently low GDI values indicate strong and frequent intrusions of hot, dry air in the low to middle troposphere, suppressing convection, both locally and in development regions for tropical waves that impact Puerto Rico. The Saharan Air Layer (SAL) is largely responsible for this anomalously hot, dry air, which produced thermodynamically stable conditions and limited thunderstorms and rainfall. Moreover, higher-than-normal aerosol concentrations, typically associated with SAL intrusion over the Caribbean, were recorded in April and May 2015. A comparison to advanced very high resolution radiometer aerosol optical thickness demonstrates that higher Caribbean aerosols in the early rainfall season, particularly June, are associated with decreased rainfall in eastern Puerto Rico. Results here demonstrate a direct link between the early and more pronounced SAL intrusions into the Caribbean and the suppression of the early rainfall season. More broadly, a reduction in the GDI and increase in the trade wind inversion was associated with reduced early season rainfall in the eastern Caribbean.

  13. Subsurface flow in a soil-mantled subtropical dolomite karst slope: A field rainfall simulation study

    Science.gov (United States)

    Fu, Z. Y.; Chen, H. S.; Zhang, W.; Xu, Q. X.; Wang, S.; Wang, K. L.

    2015-12-01

    Soil and epikarst co-evolve resulting in complex structures, but their coupled structural effects on hydrological processes are poorly understood in karst regions. This study examined the plot-scale subsurface flow characteristics from an integrated soil-epikarst system perspective in a humid subtropical cockpit karst region of Southwest China. A trench was excavated to the epikarst lower boundary for collecting individual subsurface flows in five sections with different soil thicknesses. Four field rainfall simulation experiments were carried out under different initial moisture conditions (dry and wet) and rainfall intensities (114 mm h- 1 (high) and 46 mm h- 1 (low) on average). The soil-epikarst system was characterized by shallow soil overlaying a highly irregular epikarst surface with a near-steady infiltration rate of about 35 mm h- 1. The subsurface flows occurred mainly along the soil-epikarst interface and were dominated by preferential flow. The subsurface flow hydrographs showed strong spatial variability and had high steady-state coefficients (0.52 and 0.36 for high and low rainfall intensity events). Irregular epikarst surface combining with high vertical drainage capacity resulted in high threshold rainfall depths for subsurface flows: 67 mm and 263 mm for initial wet and dry conditions, respectively. The above results evidenced that the irregular and permeable soil-epikarst interface was a crucial component of soil-epikarst architecture and consequently should be taken into account in the hydrological modeling for karst regions.

  14. Impacts of northern Tibetan Plateau on East Asian summer rainfall via modulating midlatitude transient eddies

    Science.gov (United States)

    Deng, Jiechun; Xu, Haiming; Shi, Ning; Zhang, Leying; Ma, Jing

    2017-08-01

    Roles of the Tibetan Plateau (TP) in forming and changing the seasonal Asian climate system have been widely explored. However, little is known about modulation effects of the TP on extratropical transient eddies (TEs) and subsequent synoptic responses of the East Asian rainfall. In this study, the Community Atmosphere Model version 5.1 coupled with a slab ocean model is employed to highlight the important role of the TP in regulating the upper-tropospheric transient wave train. Comparison between sensitivity experiments with and without the TP shows that the northern TP excites a strong anomalous anticyclone, which shifts the upper-level East Asian westerly jet northward and helps transfer barotropic and baroclinic energy from the mean flow to the synoptic TE flow. The transient wave train is primarily shifted northward by northern TP and is forced to propagate southeastward along the eastern flank of the TP until reaching eastern China. Before the strengthening of monsoonal southerlies, the TP-modulated transient wave train cools the troposphere, which decreases the static stability over northern China. Meanwhile, the associated anomalous warm advection induces ascending motion, leading to excessive rainfall by releasing unstable energy as the southerly strengthens. Due to the southeastward propagation of the wave train, anomalous heavy rainfall subsequently appears over eastern China from north to south, which increases day-to-day rainfall variation in this region. Additionally, occurrence of this upper-tropospheric transient wave train associated with low-level southerly peak is substantially increased by northern TP.

  15. Variability in rainfall over tropical Australia during summer and relationships with the Bilybara High

    Science.gov (United States)

    Reason, C. J. C.

    2018-04-01

    Variability in summer rainfall over tropical Australia, defined here as that part of the continent north of 25° S, and its linkages with regional circulation are examined. In particular, relationships with the mid-level anticyclone (termed the Bilybara High) that exists over the northwestern Australia/Timor Sea region between August and April are considered. This High forms to the southwest of the upper-level anticyclone via a balance between the upper-level divergence over the region of tropical precipitation maximum and planetary vorticity advection and moves south and strengthens during the spring and summer. It is shown that variations in the strength and position of the Bilybara High are related to anomalies in precipitation and temperature over large parts of tropical Australia as well as some areas in the south and southeast of the landmass. Some of the interannual variations in the High are related to ENSO, but there are also a number of neutral years with large anomalies in the High and hence in rainfall. On decadal time scales, a strong relationship exists between the leading mode of tropical Australian rainfall and the Bilybara High. On both interannual and decadal scales, the relationships between the High and the regional rainfall involve changes in the monsoonal northwesterlies blowing towards northern Australia, and further south, in the easterly trade winds over the region.

  16. Accuracy of rainfall measurement for scales of hydrological interest

    Directory of Open Access Journals (Sweden)

    S. J. Wood

    2000-01-01

    Full Text Available The dense network of 49 raingauges over the 135 km2 Brue catchment in Somerset, England is used to examine the accuracy of rainfall estimates obtained from raingauges and from weather radar. Methods for data quality control and classification of precipitation types are first described. A super-dense network comprising eight gauges within a 2 km grid square is employed to obtain a 'true value' of rainfall against which the 2 km radar grid and a single 'typical gauge' estimate can be compared. Accuracy is assessed as a function of rainfall intensity, for different periods of time-integration (15 minutes, 1 hour and 1 day and for two 8-gauge networks in areas of low and high relief. In a similar way, the catchment gauge network is used to provide the 'true catchment rainfall' and the accuracy of a radar estimate (an area-weighted average of radar pixel values and a single 'typical gauge' estimate of catchment rainfall evaluated as a function of rainfall intensity. A single gauge gives a standard error of estimate for rainfall in a 2 km square and over the catchment of 33% and 65% respectively, at rain rates of 4 mm in 15 minutes. Radar data at 2 km resolution give corresponding errors of 50% and 55%. This illustrates the benefit of using radar when estimating catchment scale rainfall. A companion paper (Wood et al., 2000 considers the accuracy of rainfall estimates obtained using raingauge and radar in combination. Keywords: rainfall, accuracy, raingauge, radar

  17. Statistical Analysis of 30 Years Rainfall Data: A Case Study

    Science.gov (United States)

    Arvind, G.; Ashok Kumar, P.; Girish Karthi, S.; Suribabu, C. R.

    2017-07-01

    Rainfall is a prime input for various engineering design such as hydraulic structures, bridges and culverts, canals, storm water sewer and road drainage system. The detailed statistical analysis of each region is essential to estimate the relevant input value for design and analysis of engineering structures and also for crop planning. A rain gauge station located closely in Trichy district is selected for statistical analysis where agriculture is the prime occupation. The daily rainfall data for a period of 30 years is used to understand normal rainfall, deficit rainfall, Excess rainfall and Seasonal rainfall of the selected circle headquarters. Further various plotting position formulae available is used to evaluate return period of monthly, seasonally and annual rainfall. This analysis will provide useful information for water resources planner, farmers and urban engineers to assess the availability of water and create the storage accordingly. The mean, standard deviation and coefficient of variation of monthly and annual rainfall was calculated to check the rainfall variability. From the calculated results, the rainfall pattern is found to be erratic. The best fit probability distribution was identified based on the minimum deviation between actual and estimated values. The scientific results and the analysis paved the way to determine the proper onset and withdrawal of monsoon results which were used for land preparation and sowing.

  18. Regional rainfall thresholds for landslide occurrence using a centenary database

    Science.gov (United States)

    Vaz, Teresa; Luís Zêzere, José; Pereira, Susana; Cruz Oliveira, Sérgio; Garcia, Ricardo A. C.; Quaresma, Ivânia

    2018-04-01

    This work proposes a comprehensive method to assess rainfall thresholds for landslide initiation using a centenary landslide database associated with a single centenary daily rainfall data set. The method is applied to the Lisbon region and includes the rainfall return period analysis that was used to identify the critical rainfall combination (cumulated rainfall duration) related to each landslide event. The spatial representativeness of the reference rain gauge is evaluated and the rainfall thresholds are assessed and calibrated using the receiver operating characteristic (ROC) metrics. Results show that landslide events located up to 10 km from the rain gauge can be used to calculate the rainfall thresholds in the study area; however, these thresholds may be used with acceptable confidence up to 50 km from the rain gauge. The rainfall thresholds obtained using linear and potential regression perform well in ROC metrics. However, the intermediate thresholds based on the probability of landslide events established in the zone between the lower-limit threshold and the upper-limit threshold are much more informative as they indicate the probability of landslide event occurrence given rainfall exceeding the threshold. This information can be easily included in landslide early warning systems, especially when combined with the probability of rainfall above each threshold.

  19. Effect of rainfall regimes and mulch decomposition on the dissipation and leaching of S-metolachlor and glyphosate: a soil column experiment.

    Science.gov (United States)

    Aslam, Sohaib; Iqbal, Akhtar; Deschamps, Marjolaine; Recous, Sylvie; Garnier, Patricia; Benoit, Pierre

    2015-02-01

    Interception by plant residues is a major process affecting pesticide persistence and leaching in conservation agriculture. Dissipation and leaching of S-metolachlor and glyphosate was studied in repacked soil columns covered with a mulch of maize and lablab residues. The columns were submitted to two contrasting simulated rainfall regimes: one with light but frequent rain (LF) and one with less frequent but more intense rain (HI). In both treatments, columns received the same amount of rainwater by the end of the experiment. Decomposing crop residues on the soil surface retained more than 50% of the applied amount of pesticide. S-metolachlor dissipation in mulch residues was faster under the LF rainfall regime. This was attributed to more humid surface conditions, under which mulch decomposition was also faster. The formation of metabolites of both molecules was higher under the LF rainfall regime. However, leaching of S-metolachlor and its metabolites to deeper soil layers was greater under the HI rainfall regime, whereas they accumulated in the surface layer under the LF rainfall regime. Glyphosate remained in the surface soil layer because of its strong adsorption capacity, whereas aminomethylphosphonic acid leached down in small amounts without any difference between the two rainfall regimes. The impact of mulch residues on herbicide dissipation was strongly dependent on molecule type and rainfall regime. © 2014 Society of Chemical Industry. © 2014 Society of Chemical Industry.

  20. Extreme rainfall events in the Sinai Peninsula

    Science.gov (United States)

    Baldi, Marina; Amin, Doaa; Zayed, Islam Sabry Al; Dalu, Giovanni A.

    2017-04-01

    In the present paper Authors discuss results from the first phase of a project carried out in the framework of the Agreement on Scientific Cooperation between the Academy of Scientific Research and Technology of Egypt (ASRT) and the National Research Council of Italy (CNR). As in ancient times, today heavy rainfall, often resulting in flash floods, affects Egypt, not only in the coastal areas along the Mediterranean Sea and the Red Sea, but also in arid and semi-arid areas such as Upper Egypt (Luxor, Aswan, and Assiut) and in the Sinai Peninsula, and their distribution has been modified due to the current climate variability. These episodes, although rare, can be catastrophic in regions characterized by a very low annual total amount of precipitation, with large impacts on lives, infrastructures, properties and last but not least, to the great cultural heritage of the Country. Flash flood episodes in the Sinai Peninsula result from heavy, sudden, and short duration rainfall, influenced also by the peculiar orography and soil conditions of the Region, and represent a risk for the population, infrastructures, properties, and sectors like industry and agriculture. On the other hand, flash floods in Sinai and southern/southeastern Egypt represent a potential source for non-conventional fresh water resources. In particular flash flood water, which usually drains into the Gulf of Suez and the Gulf of Aqaba, can fulfill a non-negligible amount of water demand, and/or recharge shallow groundwater aquifers, and the harvested rainfall can represent a source of water for rain-fed agriculture in the region. A general overview of the Sinai current climate is presented, including a climatology of extreme rainfalls events in the last decades. In addition, few selected heavy rainfall episodes which occurred in the Sinai in recent years have been analyzed and their characteristics and links to larger scale circulation will be discussed. Results of the study provide a better

  1. Properties of Extreme Poin Rainfall II

    DEFF Research Database (Denmark)

    Mikkelsen, Peter Steen; Harremoës, Poul; Rosbjerg, Dan

    1995-01-01

    into account a possible intersite dependence structure, is developed. Adding one total design standard deviation to the regionally averaged T-year events yields increased design values between 5 and 17%. This result brings up a number of questions with respect to application of historical rainfall data....... A statistically significant regional variation is documented and shown to be of importance to engineering application. The apparent variability is divided into sampling uncertainty and uncertainty caused by true regional variability. Further, a method for assessing the total inherent design uncertainty, taking...

  2. Impacts of rainfall variability and expected rainfall changes on cost-effective adaptation of water systems to climate change.

    Science.gov (United States)

    van der Pol, T D; van Ierland, E C; Gabbert, S; Weikard, H-P; Hendrix, E M T

    2015-05-01

    Stormwater drainage and other water systems are vulnerable to changes in rainfall and runoff and need to be adapted to climate change. This paper studies impacts of rainfall variability and changing return periods of rainfall extremes on cost-effective adaptation of water systems to climate change given a predefined system performance target, for example a flood risk standard. Rainfall variability causes system performance estimates to be volatile. These estimates may be used to recurrently evaluate system performance. This paper presents a model for this setting, and develops a solution method to identify cost-effective investments in stormwater drainage adaptations. Runoff and water levels are simulated with rainfall from stationary rainfall distributions, and time series of annual rainfall maxima are simulated for a climate scenario. Cost-effective investment strategies are determined by dynamic programming. The method is applied to study the choice of volume for a storage basin in a Dutch polder. We find that 'white noise', i.e. trend-free variability of rainfall, might cause earlier re-investment than expected under projected changes in rainfall. The risk of early re-investment may be reduced by increasing initial investment. This can be cost-effective if the investment involves fixed costs. Increasing initial investments, therefore, not only increases water system robustness to structural changes in rainfall, but could also offer insurance against additional costs that would occur if system performance is underestimated and re-investment becomes inevitable. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. Rainfall simulation experiments in the Southwestern USA using the Walnut Gulch rainfall simulator

    Science.gov (United States)

    The dataset contains hydrological, erosion, vegetation, ground cover, and other supplementary information from 272 rainfall simulation experiments conducted on 23 semi-arid rangeland locations in Arizona and Nevada between 2002 and 2013. On 30% of the plots simulations were conducted up to five time...

  4. Inter-comparison of satellite rainfall products for representing rainfall diurnal cycle over the Nile basin

    NARCIS (Netherlands)

    Haile, A.T.; Haile, Alemseged Tamiru; Habib, Emad; Elsaadani, Mohamed; Rientjes, T.H.M.

    2013-01-01

    In this study, the authors inter-compared the performance of three satellite-rainfall products in representing the diurnal cycle of rain occurrence and rain rate over the Nile basin in eastern Africa. These products are the real time (RT) and post-real-time (PRT) (bias adjusted) versions of Tropical

  5. Characterization of Future Caribbean Rainfall and Temperature Extremes across Rainfall Zones

    Directory of Open Access Journals (Sweden)

    Natalie Melissa McLean

    2015-01-01

    Full Text Available End-of-century changes in Caribbean climate extremes are derived from the Providing Regional Climate for Impact Studies (PRECIS regional climate model (RCM under the A2 and B2 emission scenarios across five rainfall zones. Trends in rainfall, maximum temperature, and minimum temperature extremes from the RCM are validated against meteorological stations over 1979–1989. The model displays greater skill at representing trends in consecutive wet days (CWD and extreme rainfall (R95P than consecutive dry days (CDD, wet days (R10, and maximum 5-day precipitation (RX5. Trends in warm nights, cool days, and warm days were generally well reproduced. Projections for 2071–2099 relative to 1961–1989 are obtained from the ECHAM5 driven RCM. Northern and eastern zones are projected to experience more intense rainfall under A2 and B2. There is less consensus across scenarios with respect to changes in the dry and wet spell lengths. However, there is indication that a drying trend may be manifest over zone 5 (Trinidad and northern Guyana. Changes in the extreme temperature indices generally suggest a warmer Caribbean towards the end of century across both scenarios with the strongest changes over zone 4 (eastern Caribbean.

  6. Past, present and future variations of extreme rainfall in Denmark

    DEFF Research Database (Denmark)

    Gregersen, Ida Bülow

    of non-stationary extreme rainfall behaviour, in Denmark as well as worldwide. To provide recommendations on future design intensities it is necessary to explore and understand patterns of temporal variation in urban design rainfall and identify potential drivers behind past, present and future changes....... In addition, there is a need for an extreme value model that can include both regional and temporal explanatory variables, evaluate their significance and on this basis estimate the design rainfall. Both topics are addressed in this thesis. The analysed data material includes 137 years of observed daily...... of sub-daily extreme rainfall have increased over the last 34 years. Analysis of the long daily rainfall series show that the number of extreme rainfall events, smoothed by a 10-year moving average, fluctuates between periods of relative high and periods of relatively low number of extremes. The increase...

  7. Satellite and gauge rainfall merging using geographically weighted regression

    Directory of Open Access Journals (Sweden)

    Q. Hu

    2015-05-01

    Full Text Available A residual-based rainfall merging scheme using geographically weighted regression (GWR has been proposed. This method is capable of simultaneously blending various satellite rainfall data with gauge measurements and could describe the non-stationary influences of geographical and terrain factors on rainfall spatial distribution. Using this new method, an experimental study on merging daily rainfall from the Climate Prediction Center Morphing dataset (CMOROH and gauge measurements was conducted for the Ganjiang River basin, in Southeast China. We investigated the capability of the merging scheme for daily rainfall estimation under different gauge density. Results showed that under the condition of sparse gauge density the merging rainfall scheme is remarkably superior to the interpolation using just gauge data.

  8. Engineering of an Extreme Rainfall Detection System using Grid Computing

    Directory of Open Access Journals (Sweden)

    Olivier Terzo

    2012-10-01

    Full Text Available This paper describes a new approach for intensive rainfall data analysis. ITHACA's Extreme Rainfall Detection System (ERDS is conceived to provide near real-time alerts related to potential exceptional rainfalls worldwide, which can be used by WFP or other humanitarian assistance organizations to evaluate the event and understand the potentially floodable areas where their assistance is needed. This system is based on precipitation analysis and it uses rainfall data from satellite at worldwide extent. This project uses the Tropical Rainfall Measuring Mission Multisatellite Precipitation Analysis dataset, a NASA-delivered near real-time product for current rainfall condition monitoring over the world. Considering the great deal of data to process, this paper presents an architectural solution based on Grid Computing techniques. Our focus is on the advantages of using a distributed architecture in terms of performances for this specific purpose.

  9. From meteorological to hydrological drought in the Upper Niger Basin: trend and uncertainty analysis in the monitoring and the modeling of rainfall deficits and low flow responses

    Science.gov (United States)

    Fournet, S.; Aich, V.; Liersch, S.; Hattermann, F. F.

    2012-04-01

    From 1970 to 2002, the Sahel experienced a fairly abrupt, severe and continuous dry episode. The main reason is the oceanic forcing ruling the West African monsoon dynamic. Also, a combinative effect of climate and anthropogenic changes (demographic pressure on land associated to inappropriate land-use practices) initiates and supports the interactive processes of drying and land cover degradation forming a complex land atmosphere feedback convection. The Great Drought in Mali largely affected the regional food security, the human societies and economic development and the conservation of wet and semi-arid ecosystems. It results in an increasing competition and conflicts for water access between vulnerable local stakeholders (rainfed and controlled irrigation farming, nomad pastoralism, traditional fishing) and steers national investments with the construction of dams and diversion channels for development of hydropower energy and fully governed irrigated agriculture. To support drought adaptations in regional development strategies, climate and hydrological forecasting are thus of paramount importance. Whilst climate change is typically associated with an increase in mean global surface temperature, what matters regionally and still remains uncertain is the change in rainfall, discharge and drought patterns from daily intensity to large inter-annual and multi-decadal variability. Different climate data sources exist for investigation of climate variability and change: daily measurements, reanalysis data and climate scenarios using Global and Regional Circulation Models (GCMs and RCMs). This study aims at analyzing the suitability of the different data sources for drought investigation in the target area, the Upper Niger Basin. First, the performance of meteorological data sets based on climate reanalysis is assessed in comparison of data of synoptic stations. Second, one statistical (STAR) and two dynamical regional RCMs (CCLM, REMO) are compared to IPCC-GCM data

  10. Rainfall Downscaling Conditional on Upper-air Atmospheric Predictors: Improved Assessment of Rainfall Statistics in a Changing Climate

    Science.gov (United States)

    Langousis, Andreas; Mamalakis, Antonis; Deidda, Roberto; Marrocu, Marino

    2015-04-01

    To improve the level skill of Global Climate Models (GCMs) and Regional Climate Models (RCMs) in reproducing the statistics of rainfall at a basin level and at hydrologically relevant temporal scales (e.g. daily), two types of statistical approaches have been suggested. One is the statistical correction of climate model rainfall outputs using historical series of precipitation. The other is the use of stochastic models of rainfall to conditionally simulate precipitation series, based on large-scale atmospheric predictors produced by climate models (e.g. geopotential height, relative vorticity, divergence, mean sea level pressure). The latter approach, usually referred to as statistical rainfall downscaling, aims at reproducing the statistical character of rainfall, while accounting for the effects of large-scale atmospheric circulation (and, therefore, climate forcing) on rainfall statistics. While promising, statistical rainfall downscaling has not attracted much attention in recent years, since the suggested approaches involved complex (i.e. subjective or computationally intense) identification procedures of the local weather, in addition to demonstrating limited success in reproducing several statistical features of rainfall, such as seasonal variations, the distributions of dry and wet spell lengths, the distribution of the mean rainfall intensity inside wet periods, and the distribution of rainfall extremes. In an effort to remedy those shortcomings, Langousis and Kaleris (2014) developed a statistical framework for simulation of daily rainfall intensities conditional on upper air variables, which accurately reproduces the statistical character of rainfall at multiple time-scales. Here, we study the relative performance of: a) quantile-quantile (Q-Q) correction of climate model rainfall products, and b) the statistical downscaling scheme of Langousis and Kaleris (2014), in reproducing the statistical structure of rainfall, as well as rainfall extremes, at a

  11. Satellite rainfall retrieval by logistic regression

    Science.gov (United States)

    Chiu, Long S.

    1986-01-01

    The potential use of logistic regression in rainfall estimation from satellite measurements is investigated. Satellite measurements provide covariate information in terms of radiances from different remote sensors.The logistic regression technique can effectively accommodate many covariates and test their significance in the estimation. The outcome from the logistical model is the probability that the rainrate of a satellite pixel is above a certain threshold. By varying the thresholds, a rainrate histogram can be obtained, from which the mean and the variant can be estimated. A logistical model is developed and applied to rainfall data collected during GATE, using as covariates the fractional rain area and a radiance measurement which is deduced from a microwave temperature-rainrate relation. It is demonstrated that the fractional rain area is an important covariate in the model, consistent with the use of the so-called Area Time Integral in estimating total rain volume in other studies. To calibrate the logistical model, simulated rain fields generated by rainfield models with prescribed parameters are needed. A stringent test of the logistical model is its ability to recover the prescribed parameters of simulated rain fields. A rain field simulation model which preserves the fractional rain area and lognormality of rainrates as found in GATE is developed. A stochastic regression model of branching and immigration whose solutions are lognormally distributed in some asymptotic limits has also been developed.

  12. Bias correction of satellite-based rainfall data

    Science.gov (United States)

    Bhattacharya, Biswa; Solomatine, Dimitri

    2015-04-01

    Limitation in hydro-meteorological data availability in many catchments limits the possibility of reliable hydrological analyses especially for near-real-time predictions. However, the variety of satellite based and meteorological model products for rainfall provides new opportunities. Often times the accuracy of these rainfall products, when compared to rain gauge measurements, is not impressive. The systematic differences of these rainfall products from gauge observations can be partially compensated by adopting a bias (error) correction. Many of such methods correct the satellite based rainfall data by comparing their mean value to the mean value of rain gauge data. Refined approaches may also first find out a suitable time scale at which different data products are better comparable and then employ a bias correction at that time scale. More elegant methods use quantile-to-quantile bias correction, which however, assumes that the available (often limited) sample size can be useful in comparing probabilities of different rainfall products. Analysis of rainfall data and understanding of the process of its generation reveals that the bias in different rainfall data varies in space and time. The time aspect is sometimes taken into account by considering the seasonality. In this research we have adopted a bias correction approach that takes into account the variation of rainfall in space and time. A clustering based approach is employed in which every new data point (e.g. of Tropical Rainfall Measuring Mission (TRMM)) is first assigned to a specific cluster of that data product and then, by identifying the corresponding cluster of gauge data, the bias correction specific to that cluster is adopted. The presented approach considers the space-time variation of rainfall and as a result the corrected data is more realistic. Keywords: bias correction, rainfall, TRMM, satellite rainfall

  13. Seasonal Trends of Rainfall and Surface Temperature over Southern Africa

    OpenAIRE

    MORISHIMA, Wataru; AKASAKA, Ikumi

    2010-01-01

    This study investigated seasonal trends of surface temperature and rainfall from 1979 to 2007 in southern Africa. In recent years, annual rainfall has decreased over the African continent from the equator to 20ºS, as well as in Madagascar. On the other hand, annual mean surface temperature has shown an increasing trend across the whole region, with particularly large rates of increase in Namibia and Angola. The spatial and temporal structures of trends in rainfall and surface temperature have...

  14. A Metastatistical Approach to Satellite Estimates of Extreme Rainfall Events

    Science.gov (United States)

    Zorzetto, E.; Marani, M.

    2017-12-01

    The estimation of the average recurrence interval of intense rainfall events is a central issue for both hydrologic modeling and engineering design. These estimates require the inference of the properties of the right tail of the statistical distribution of precipitation, a task often performed using the Generalized Extreme Value (GEV) distribution, estimated either from a samples of annual maxima (AM) or with a peaks over threshold (POT) approach. However, these approaches require long and homogeneous rainfall records, which often are not available, especially in the case of remote-sensed rainfall datasets. We use here, and tailor it to remotely-sensed rainfall estimates, an alternative approach, based on the metastatistical extreme value distribution (MEVD), which produces estimates of rainfall extreme values based on the probability distribution function (pdf) of all measured `ordinary' rainfall event. This methodology also accounts for the interannual variations observed in the pdf of daily rainfall by integrating over the sample space of its random parameters. We illustrate the application of this framework to the TRMM Multi-satellite Precipitation Analysis rainfall dataset, where MEVD optimally exploits the relatively short datasets of satellite-sensed rainfall, while taking full advantage of its high spatial resolution and quasi-global coverage. Accuracy of TRMM precipitation estimates and scale issues are here investigated for a case study located in the Little Washita watershed, Oklahoma, using a dense network of rain gauges for independent ground validation. The methodology contributes to our understanding of the risk of extreme rainfall events, as it allows i) an optimal use of the TRMM datasets in estimating the tail of the probability distribution of daily rainfall, and ii) a global mapping of daily rainfall extremes and distributional tail properties, bridging the existing gaps in rain gauges networks.

  15. Extreme Rainfall Mechanisms Exhibited by Typhoon Morakot (2009

    Directory of Open Access Journals (Sweden)

    Ching-Yuang Huang

    2011-01-01

    Full Text Available Moderate Typhoon Morakot (2009 became the most catastrophic typhoon in Taiwan on record. The MM5 numerical experiments with and without bogus data assimilation (BDA were used to investigate the extreme rainfall mechanisms in Taiwan associated with the westbound typhoon. The BDA, based on 4DVAR, helps MM5 to maintain a more consolidated typhoon vortex and better predict the observed track after landfall, thus producing realistic extreme rainfall (about 2400 mm at the southern and Central Mountain Range (CMR of Taiwan. Severe rainfall in Taiwan is dominated by the CMR that hence modulates rainfall predictability.

  16. Analysis of rainfall distribution in Kelantan river basin, Malaysia

    Science.gov (United States)

    Che Ros, Faizah; Tosaka, Hiroyuki

    2018-03-01

    Using rainfall gauge on its own as input carries great uncertainties regarding runoff estimation, especially when the area is large and the rainfall is measured and recorded at irregular spaced gauging stations. Hence spatial interpolation is the key to obtain continuous and orderly rainfall distribution at unknown points to be the input to the rainfall runoff processes for distributed and semi-distributed numerical modelling. It is crucial to study and predict the behaviour of rainfall and river runoff to reduce flood damages of the affected area along the Kelantan river. Thus, a good knowledge on rainfall distribution is essential in early flood prediction studies. Forty six rainfall stations and their daily time-series were used to interpolate gridded rainfall surfaces using inverse-distance weighting (IDW), inverse-distance and elevation weighting (IDEW) methods and average rainfall distribution. Sensitivity analysis for distance and elevation parameters were conducted to see the variation produced. The accuracy of these interpolated datasets was examined using cross-validation assessment.

  17. A rainfall simulation model for agricultural development in Bangladesh

    Directory of Open Access Journals (Sweden)

    M. Sayedur Rahman

    2000-01-01

    Full Text Available A rainfall simulation model based on a first-order Markov chain has been developed to simulate the annual variation in rainfall amount that is observed in Bangladesh. The model has been tested in the Barind Tract of Bangladesh. Few significant differences were found between the actual and simulated seasonal, annual and average monthly. The distribution of number of success is asymptotic normal distribution. When actual and simulated daily rainfall data were used to drive a crop simulation model, there was no significant difference of rice yield response. The results suggest that the rainfall simulation model perform adequately for many applications.

  18. Distributional changes in rainfall and river flow in Sarawak, Malaysia

    Science.gov (United States)

    Sa'adi, Zulfaqar; Shahid, Shamsuddin; Ismail, Tarmizi; Chung, Eun-Sung; Wang, Xiao-Jun

    2017-11-01

    Climate change may not change the rainfall mean, but the variability and extremes. Therefore, it is required to explore the possible distributional changes of rainfall characteristics over time. The objective of present study is to assess the distributional changes in annual and northeast monsoon rainfall (November-January) and river flow in Sarawak where small changes in rainfall or river flow variability/distribution may have severe implications on ecology and agriculture. A quantile regression-based approach was used to assess the changes of scale and location of empirical probability density function over the period 1980-2014 at 31 observational stations. The results indicate that diverse variation patterns exist at all stations for annual rainfall but mainly increasing quantile trend at the lowers, and higher quantiles for the month of January and December. The significant increase in annual rainfall is found mostly in the north and central-coastal region and monsoon month rainfalls in the interior and north of Sarawak. Trends in river flow data show that changes in rainfall distribution have affected higher quantiles of river flow in monsoon months at some of the basins and therefore more flooding. The study reveals that quantile trend can provide more information of rainfall change which may be useful for climate change mitigation and adaptation planning.

  19. Analysis of rainfall distribution in Kelantan river basin, Malaysia

    Directory of Open Access Journals (Sweden)

    Che Ros Faizah

    2018-01-01

    Full Text Available Using rainfall gauge on its own as input carries great uncertainties regarding runoff estimation, especially when the area is large and the rainfall is measured and recorded at irregular spaced gauging stations. Hence spatial interpolation is the key to obtain continuous and orderly rainfall distribution at unknown points to be the input to the rainfall runoff processes for distributed and semi-distributed numerical modelling. It is crucial to study and predict the behaviour of rainfall and river runoff to reduce flood damages of the affected area along the Kelantan river. Thus, a good knowledge on rainfall distribution is essential in early flood prediction studies. Forty six rainfall stations and their daily time-series were used to interpolate gridded rainfall surfaces using inverse-distance weighting (IDW, inverse-distance and elevation weighting (IDEW methods and average rainfall distribution. Sensitivity analysis for distance and elevation parameters were conducted to see the variation produced. The accuracy of these interpolated datasets was examined using cross-validation assessment.

  20. Characterizing rainfall parameters which influence erosivity in southeastern Nigeria

    International Nuclear Information System (INIS)

    Obi, M.E.; Salako, F.K.

    1993-12-01

    An investigation was carried out to characterize some selected parameters which influence rainfall erosivity in southeastern Nigeria. Rainfall amount, distribution, duration, intensity, storm types, energy loads and frequency of rain events in the region were studied using data from stations located in three major agroecological zones. Raindrop size and detaching capacity were evaluated in one of the stations for two months. The mean annual rainfall erosivity values for southeastern Nigeria point to the fact that rainfall tend to be highly erosive. 25 refs, 6 figs, 8 tabs

  1. Runoff Analysis Considering Orographical Features Using Dual Polarization Radar Rainfall

    Science.gov (United States)

    Noh, Hui-seong; Shin, Hyun-seok; Kang, Na-rae; Lee, Choong-Ke; Kim, Hung-soo

    2013-04-01

    Recently, the necessity for rainfall estimation and forecasting using the radar is being highlighted, due to the frequent occurrence of torrential rainfall resulting from abnormal changes of weather. Radar rainfall data represents temporal and spatial distributions properly and replace the existing rain gauge networks. It is also frequently applied in many hydrologic field researches. However, the radar rainfall data has an accuracy limitation since it estimates rainfall, by monitoring clouds and precipitation particles formed around the surface of the earth(1.5-3km above the surface) or the atmosphere. In a condition like Korea where nearly 70% of the land is covered by mountainous areas, there are lots of restrictions to use rainfall radar, because of the occurrence of beam blocking areas by topography. This study is aiming at analyzing runoff and examining the applicability of (R(Z), R(ZDR) and R(KDP)) provided by the Han River Flood Control Office(HRFCO) based on the basin elevation of Nakdong river watershed. For this purpose, the amount of radar rainfall of each rainfall event was estimated according to three sub-basins of Nakdong river watershed with the average basin elevation above 400m which are Namgang dam, Andong dam and Hapcheon dam and also another three sub-basins with the average basin elevation below 150m which are Waegwan, Changryeong and Goryeong. After runoff analysis using a distribution model, Vflo model, the results were reviewed and compared with the observed runoff. This study estimated the rainfall by using the radar-rainfall transform formulas, (R(Z), R(Z,ZDR) and R(Z,ZDR,KDP) for four stormwater events and compared the results with the point rainfall of the rain gauge. As the result, it was overestimated or underestimated, depending on rainfall events. Also, calculation indicates that the values from R(Z,ZDR) and R(Z,ZDR,KDP) relatively showed the most similar results. Moreover the runoff analysis using the estimated radar rainfall is

  2. Regional frequency analysis of extreme rainfall in Belgium based on radar estimates

    Directory of Open Access Journals (Sweden)

    E. Goudenhoofdt

    2017-10-01

    Full Text Available In Belgium, only rain gauge time series have been used so far to study extreme rainfall at a given location. In this paper, the potential of a 12-year quantitative precipitation estimation (QPE from a single weather radar is evaluated. For the period 2005–2016, 1 and 24 h rainfall extremes from automatic rain gauges and collocated radar estimates are compared. The peak intensities are fitted to the exponential distribution using regression in Q-Q plots with a threshold rank which minimises the mean squared error. A basic radar product used as reference exhibits unrealistic high extremes and is not suitable for extreme value analysis. For 24 h rainfall extremes, which occur partly in winter, the radar-based QPE needs a bias correction. A few missing events are caused by the wind drift associated with convective cells and strong radar signal attenuation. Differences between radar and gauge rainfall values are caused by spatial and temporal sampling, gauge underestimations and radar errors. Nonetheless the fit to the QPE data is within the confidence interval of the gauge fit, which remains large due to the short study period. A regional frequency analysis for 1 h duration is performed at the locations of four gauges with 1965–2008 records using the spatially independent QPE data in a circle of 20 km. The confidence interval of the radar fit, which is small due to the sample size, contains the gauge fit for the two closest stations from the radar. In Brussels, the radar extremes are significantly higher than the gauge rainfall extremes, but similar to those observed by an automatic gauge during the same period. The extreme statistics exhibit slight variations related to topography. The radar-based extreme value analysis can be extended to other durations.

  3. Satellite observations of rainfall effect on sea surface salinity in the waters adjacent to Taiwan

    Science.gov (United States)

    Ho, Chung-Ru; Hsu, Po-Chun; Lin, Chen-Chih; Huang, Shih-Jen

    2017-10-01

    Changes of oceanic salinity are highly related to the variations of evaporation and precipitation. To understand the influence of rainfall on the sea surface salinity (SSS) in the waters adjacent to Taiwan, satellite remote sensing data from the year of 2012 to 2014 are employed in this study. The daily rain rate data obtained from Special Sensor Microwave Imager (SSM/I), Tropical Rainfall Measuring Mission's Microwave Imager (TRMM/TMI), Advanced Microwave Scanning Radiometer (AMSR), and WindSat Polarimetric Radiometer. The SSS data was derived from the measurements of radiometer instruments onboard the Aquarius satellite. The results show the average values of SSS in east of Taiwan, east of Luzon and South China Sea are 33.83 psu, 34.05 psu, and 32.84 psu, respectively, in the condition of daily rain rate higher than 1 mm/hr. In contrast to the rainfall condition, the average values of SSS are 34.07 psu, 34.26 psu, and 33.09 psu in the three areas, respectively at no rain condition (rain rate less than 1 mm/hr). During the cases of heavy rainfall caused by spiral rain bands of typhoon, the SSS is diluted with an average value of -0.78 psu when the average rain rate is higher than 4 mm/hr. However, the SSS was increased after temporarily decreased during the typhoon cases. A possible reason to explain this phenomenon is that the heavy rainfall caused by the spiral rain bands of typhoon may dilute the sea surface water, but the strong winds can uplift the higher salinity of subsurface water to the sea surface.

  4. Performance of high-resolution X-band radar for rainfall measurement in The Netherlands

    Directory of Open Access Journals (Sweden)

    C. Z. van de Beek

    2010-02-01

    Full Text Available This study presents an analysis of 195 rainfall events gathered with the X-band weather radar SOLIDAR and a tipping bucket rain gauge network near Delft, The Netherlands, between May 1993 and April 1994. The aim of this paper is to present a thorough analysis of a climatological dataset using a high spatial (120 m and temporal (16 s resolution X-band radar. This makes it a study of the potential for high-resolution rainfall measurements with non-polarimetric X-band radar over flat terrain. An appropriate radar reflectivity – rain rate relation is derived from measurements of raindrop size distributions and compared with radar – rain gauge data. The radar calibration is assessed using a long-term comparison of rain gauge measurements with corresponding radar reflectivities as well as by analyzing the evolution of the stability of ground clutter areas over time. Three different methods for ground clutter correction as well as the effectiveness of forward and backward attenuation correction algorithms have been studied. Five individual rainfall events are discussed in detail to illustrate the strengths and weaknesses of high-resolution X-band radar and the effectiveness of the presented correction methods. X-band radar is found to be able to measure the space-time variation of rainfall at high resolution, far greater than what can be achieved by rain gauge networks or a typical operational C-band weather radar. On the other hand, SOLIDAR can suffer from receiver saturation, wet radome attenuation as well as signal loss along the path. During very strong convective situations the signal can even be lost completely. In combination with several rain gauges for quality control, high resolution X-band radar is considered to be suitable for rainfall monitoring over relatively small (urban catchments. These results offer great prospects for the new high resolution polarimetric doppler X-band radar IDRA.

  5. Regional frequency analysis of extreme rainfall in Belgium based on radar estimates

    Science.gov (United States)

    Goudenhoofdt, Edouard; Delobbe, Laurent; Willems, Patrick

    2017-10-01

    In Belgium, only rain gauge time series have been used so far to study extreme rainfall at a given location. In this paper, the potential of a 12-year quantitative precipitation estimation (QPE) from a single weather radar is evaluated. For the period 2005-2016, 1 and 24 h rainfall extremes from automatic rain gauges and collocated radar estimates are compared. The peak intensities are fitted to the exponential distribution using regression in Q-Q plots with a threshold rank which minimises the mean squared error. A basic radar product used as reference exhibits unrealistic high extremes and is not suitable for extreme value analysis. For 24 h rainfall extremes, which occur partly in winter, the radar-based QPE needs a bias correction. A few missing events are caused by the wind drift associated with convective cells and strong radar signal attenuation. Differences between radar and gauge rainfall values are caused by spatial and temporal sampling, gauge underestimations and radar errors. Nonetheless the fit to the QPE data is within the confidence interval of the gauge fit, which remains large due to the short study period. A regional frequency analysis for 1 h duration is performed at the locations of four gauges with 1965-2008 records using the spatially independent QPE data in a circle of 20 km. The confidence interval of the radar fit, which is small due to the sample size, contains the gauge fit for the two closest stations from the radar. In Brussels, the radar extremes are significantly higher than the gauge rainfall extremes, but similar to those observed by an automatic gauge during the same period. The extreme statistics exhibit slight variations related to topography. The radar-based extreme value analysis can be extended to other durations.

  6. Adjusting Satellite Rainfall Error in Mountainous Areas for Flood Modeling Applications

    Science.gov (United States)

    Zhang, X.; Anagnostou, E. N.; Astitha, M.; Vergara, H. J.; Gourley, J. J.; Hong, Y.

    2014-12-01

    This study aims to investigate the use of high-resolution Numerical Weather Prediction (NWP) for evaluating biases of satellite rainfall estimates of flood-inducing storms in mountainous areas and associated improvements in flood modeling. Satellite-retrieved precipitation has been considered as a feasible data source for global-scale flood modeling, given that satellite has the spatial coverage advantage over in situ (rain gauges and radar) observations particularly over mountainous areas. However, orographically induced heavy precipitation events tend to be underestimated and spatially smoothed by satellite products, which error propagates non-linearly in flood simulations.We apply a recently developed retrieval error and resolution effect correction method (Zhang et al. 2013*) on the NOAA Climate Prediction Center morphing technique (CMORPH) product based on NWP analysis (or forecasting in the case of real-time satellite products). The NWP rainfall is derived from the Weather Research and Forecasting Model (WRF) set up with high spatial resolution (1-2 km) and explicit treatment of precipitation microphysics.In this study we will show results on NWP-adjusted CMORPH rain rates based on tropical cyclones and a convective precipitation event measured during NASA's IPHEX experiment in the South Appalachian region. We will use hydrologic simulations over different basins in the region to evaluate propagation of bias correction in flood simulations. We show that the adjustment reduced the underestimation of high rain rates thus moderating the strong rainfall magnitude dependence of CMORPH rainfall bias, which results in significant improvement in flood peak simulations. Further study over Blue Nile Basin (western Ethiopia) will be investigated and included in the presentation. *Zhang, X. et al. 2013: Using NWP Simulations in Satellite Rainfall Estimation of Heavy Precipitation Events over Mountainous Areas. J. Hydrometeor, 14, 1844-1858.

  7. Does the GPM mission improve the systematic error component in satellite rainfall estimates over TRMM? An evaluation at a pan-India scale

    Science.gov (United States)

    Beria, Harsh; Nanda, Trushnamayee; Singh Bisht, Deepak; Chatterjee, Chandranath

    2017-12-01

    The last couple of decades have seen the outburst of a number of satellite-based precipitation products with Tropical Rainfall Measuring Mission (TRMM) as the most widely used for hydrologic applications. Transition of TRMM into the Global Precipitation Measurement (GPM) promises enhanced spatio-temporal resolution along with upgrades to sensors and rainfall estimation techniques. The dependence of systematic error components in rainfall estimates of the Integrated Multi-satellitE Retrievals for GPM (IMERG), and their variation with climatology and topography, was evaluated over 86 basins in India for year 2014 and compared with the corresponding (2014) and retrospective (1998-2013) TRMM estimates. IMERG outperformed TRMM for all rainfall intensities across a majority of Indian basins, with significant improvement in low rainfall estimates showing smaller negative biases in 75 out of 86 basins. Low rainfall estimates in TRMM showed a systematic dependence on basin climatology, with significant overprediction in semi-arid basins, which gradually improved in the higher rainfall basins. Medium and high rainfall estimates of TRMM exhibited a strong dependence on basin topography, with declining skill in higher elevation basins. The systematic dependence of error components on basin climatology and topography was reduced in IMERG, especially in terms of topography. Rainfall-runoff modeling using the Variable Infiltration Capacity (VIC) model over two flood-prone basins (Mahanadi and Wainganga) revealed that improvement in rainfall estimates in IMERG did not translate into improvement in runoff simulations. More studies are required over basins in different hydroclimatic zones to evaluate the hydrologic significance of IMERG.

  8. Does the GPM mission improve the systematic error component in satellite rainfall estimates over TRMM? An evaluation at a pan-India scale

    Directory of Open Access Journals (Sweden)

    H. Beria

    2017-12-01

    Full Text Available The last couple of decades have seen the outburst of a number of satellite-based precipitation products with Tropical Rainfall Measuring Mission (TRMM as the most widely used for hydrologic applications. Transition of TRMM into the Global Precipitation Measurement (GPM promises enhanced spatio-temporal resolution along with upgrades to sensors and rainfall estimation techniques. The dependence of systematic error components in rainfall estimates of the Integrated Multi-satellitE Retrievals for GPM (IMERG, and their variation with climatology and topography, was evaluated over 86 basins in India for year 2014 and compared with the corresponding (2014 and retrospective (1998–2013 TRMM estimates. IMERG outperformed TRMM for all rainfall intensities across a majority of Indian basins, with significant improvement in low rainfall estimates showing smaller negative biases in 75 out of 86 basins. Low rainfall estimates in TRMM showed a systematic dependence on basin climatology, with significant overprediction in semi-arid basins, which gradually improved in the higher rainfall basins. Medium and high rainfall estimates of TRMM exhibited a strong dependence on basin topography, with declining skill in higher elevation basins. The systematic dependence of error components on basin climatology and topography was reduced in IMERG, especially in terms of topography. Rainfall-runoff modeling using the Variable Infiltration Capacity (VIC model over two flood-prone basins (Mahanadi and Wainganga revealed that improvement in rainfall estimates in IMERG did not translate into improvement in runoff simulations. More studies are required over basins in different hydroclimatic zones to evaluate the hydrologic significance of IMERG.

  9. Correlations of Rainfall and Forest Type with Papilionid Assemblages in Assam in Northeast India

    Directory of Open Access Journals (Sweden)

    Kamini Kusum Barua

    2010-01-01

    Full Text Available No comprehensive community studies have been done on the butterflies of the tropical monsoon forests of the East Himalayan region. We described the Papilionidae at one site within the continuous moist deciduous forest belt of Northeast India and their variation with season and forest type. We surveyed 20 permanent line transects, varying with respect to canopy openness and observed levels of disturbance. A total sample effort of 131 days during the dry and wet seasons of a two-year study resulted in 18,373 individuals identified from 28 Papilionidae species. Constrained canonical correspondence ordination was used to examine the effects of season, forest type, rainfall, year, altitude, and geographical position on the species assemblages. Results showed that rainfall, forest type, and season accounted for most variance in papilionid abundance. Rainfall was strongly correlated with the abundance of some species. Nine species were associated with gaps, 16 species were restricted to closed forest, and three species were encountered in both gaps and closed forest. Six species with narrow geographic range were found only in closed forest. The results confirm the strong seasonality of continental Southeast Asian butterfly assemblages.

  10. Multivariate Analysis of Erosivity Indices and Rainfall Physical Characteristics Associated with Rainfall Patterns in Rio de Janeiro

    Directory of Open Access Journals (Sweden)

    Roriz Luciano Machado

    2017-12-01

    Full Text Available ABSTRACT The identification of areas with greater erosive potential is important for planning soil and water conservation. The objective of this study was to evaluate the physical characteristics of rainfall events in the state of Rio de Janeiro, Brazil, and their interactions with rainfall patterns through multivariate statistical analysis. Rainfall depth, kinetic energy, 30-min intensity (I30, duration of rainfall events, and the erosivity indices KE >10, KE >25, and EI30 in 36 locations (stations were subjected to principal component analysis (PCA and canonical discriminant analysis (CDA. Based on evaluation of the respective historical series of hyetographs, it was found that the advanced pattern occurs with highest frequency (51.8 %, followed by the delayed pattern (26.1 %, and by the intermediate pattern (22.1 %. All the evaluated rainfall characteristics have high response capacity in describing localities and rainfall patterns through PCA and CDA. In CDA, the Tukey test (p<0.05 applied to the scores of the first canonical discriminant function (CDF1 allowed differentiation of the stations with respect to the rainfall and erosivity characteristics for the advanced and delayed patterns. In the delayed pattern, the localities of Angra dos Reis, Campos, Eletrobrás, Manuel Duarte, Santa Isabel do Rio Preto, Tanguá, Teresópolis, Vila Mambucaba, and Xerém had the highest CDF1 scores, indicating that they have rainfalls with higher depth, I30, and duration because the standardized canonical coefficient (SCC and the correlation coefficient (“r” of these characteristics were positive. The rainfall events in the state of Rio de Janeiro differ from one locality to another in relation to the advanced and delayed rainfall patterns, mainly due to the physical characteristics of rainfall depth, I30, and duration, indicating a higher risk of soil loss and runoff in the localities where rainfall events with the delayed pattern prevail.

  11. Multi-century cool- and warm-season rainfall reconstructions for Australia's major climatic regions

    Science.gov (United States)

    Freund, Mandy; Henley, Benjamin J.; Karoly, David J.; Allen, Kathryn J.; Baker, Patrick J.

    2017-11-01

    Australian seasonal rainfall is strongly affected by large-scale ocean-atmosphere climate influences. In this study, we exploit the links between these precipitation influences, regional rainfall variations, and palaeoclimate proxies in the region to reconstruct Australian regional rainfall between four and eight centuries into the past. We use an extensive network of palaeoclimate records from the Southern Hemisphere to reconstruct cool (April-September) and warm (October-March) season rainfall in eight natural resource management (NRM) regions spanning the Australian continent. Our bi-seasonal rainfall reconstruction aligns well with independent early documentary sources and existing reconstructions. Critically, this reconstruction allows us, for the first time, to place recent observations at a bi-seasonal temporal resolution into a pre-instrumental context, across the entire continent of Australia. We find that recent 30- and 50-year trends towards wetter conditions in tropical northern Australia are highly unusual in the multi-century context of our reconstruction. Recent cool-season drying trends in parts of southern Australia are very unusual, although not unprecedented, across the multi-century context. We also use our reconstruction to investigate the spatial and temporal extent of historical drought events. Our reconstruction reveals that the spatial extent and duration of the Millennium Drought (1997-2009) appears either very much below average or unprecedented in southern Australia over at least the last 400 years. Our reconstruction identifies a number of severe droughts over the past several centuries that vary widely in their spatial footprint, highlighting the high degree of diversity in historical droughts across the Australian continent. We document distinct characteristics of major droughts in terms of their spatial extent, duration, intensity, and seasonality. Compared to the three largest droughts in the instrumental period (Federation Drought

  12. Multi-century cool- and warm-season rainfall reconstructions for Australia's major climatic regions

    Directory of Open Access Journals (Sweden)

    M. Freund

    2017-11-01

    Full Text Available Australian seasonal rainfall is strongly affected by large-scale ocean–atmosphere climate influences. In this study, we exploit the links between these precipitation influences, regional rainfall variations, and palaeoclimate proxies in the region to reconstruct Australian regional rainfall between four and eight centuries into the past. We use an extensive network of palaeoclimate records from the Southern Hemisphere to reconstruct cool (April–September and warm (October–March season rainfall in eight natural resource management (NRM regions spanning the Australian continent. Our bi-seasonal rainfall reconstruction aligns well with independent early documentary sources and existing reconstructions. Critically, this reconstruction allows us, for the first time, to place recent observations at a bi-seasonal temporal resolution into a pre-instrumental context, across the entire continent of Australia. We find that recent 30- and 50-year trends towards wetter conditions in tropical northern Australia are highly unusual in the multi-century context of our reconstruction. Recent cool-season drying trends in parts of southern Australia are very unusual, although not unprecedented, across the multi-century context. We also use our reconstruction to investigate the spatial and temporal extent of historical drought events. Our reconstruction reveals that the spatial extent and duration of the Millennium Drought (1997–2009 appears either very much below average or unprecedented in southern Australia over at least the last 400 years. Our reconstruction identifies a number of severe droughts over the past several centuries that vary widely in their spatial footprint, highlighting the high degree of diversity in historical droughts across the Australian continent. We document distinct characteristics of major droughts in terms of their spatial extent, duration, intensity, and seasonality. Compared to the three largest droughts in the instrumental

  13. Secular spring rainfall variability at local scale over Ethiopia: trend and associated dynamics

    Science.gov (United States)

    Tsidu, Gizaw Mengistu

    2017-10-01

    Spring rainfall secular variability is studied using observations, reanalysis, and model simulations. The joint coherent spatio-temporal secular variability of gridded monthly gauge rainfall over Ethiopia, ERA-Interim atmospheric variables and sea surface temperature (SST) from Hadley Centre Sea Ice and SST (HadISST) data set is extracted using multi-taper method singular value decomposition (MTM-SVD). The contemporaneous associations are further examined using partial Granger causality to determine presence of causal linkage between any of the climate variables. This analysis reveals that only the northwestern Indian Ocean secular SST anomaly has direct causal links with spring rainfall over Ethiopia and mean sea level pressure (MSLP) over Africa inspite of the strong secular covariance of spring rainfall, SST in parts of subtropical Pacific, Atlantic, Indian Ocean and MSLP. High secular rainfall variance and statistically significant linear trend show consistently that there is a massive decline in spring rain over southern Ethiopia. This happened concurrently with significant buildup of MSLP over East Africa, northeastern Africa including parts of the Arabian Peninsula, some parts of central Africa and SST warming over all ocean basins with the exception of the ENSO regions. The east-west pressure gradient in response to the Indian Ocean warming led to secular southeasterly winds over the Arabian Sea, easterly over central Africa and equatorial Atlantic. These flows weakened climatological northeasterly flow over the Arabian Sea and southwesterly flow over equatorial Atlantic and Congo basins which supply moisture into the eastern Africa regions in spring. The secular divergent flow at low level is concurrent with upper level convergence due to the easterly secular anomalous flow. The mechanisms through which the northwestern Indian Ocean secular SST anomaly modulates rainfall are further explored in the context of East Africa using a simplified atmospheric

  14. Empirical rainfall thresholds for landslide occurrence in Portugal

    Science.gov (United States)

    Zêzere, José Luis; Vaz, Teresa; Pereira, Susana; Oliveira, Sérgio C.; Marques, Rui; Garcia, Ricardo A. C.

    2015-04-01

    Rainfall is the most important physical process responsible for the landslide triggering in Portugal. Following the work of Zêzere et al. (2014), we present the state of the art concerning the proposition of empirical rainfall thresholds in Portugal for different types of landslides observed in different zones of the country: the Lisbon region, the Douro Valley and the NW Mountains, and the Povoação Municipality in São Miguel Island (Azores). The empirical thresholds applied in Portugal are based on the identification of 120 landslide events and include (i) the computation of antecedent rainfall threshold defined by linear regression, (ii) the normalization of rainfall by the mean annual precipitation, (iii) the definition of combined rainfall thresholds, which integrates the rainfall event and the antecedent rainfall for different time periods, and (iv) the definition of lower limit and upper limit rainfall thresholds. The intensity-duration (ID) threshold is the empirical rainfall threshold more used worldwide. In mainland Portugal, the highest ID rainfall threshold is registered in the NW Mountains, which is the rainiest zone of the country. The Lisbon Region typically receives less rain per year and the corresponding ID threshold is lower than that obtained in the north part of the country. The Povoação study area evidence a contrasting situation, which is associated to the highest value of the negative exponential of the threshold (-0.66). As a consequence, for short duration (1,000 h) it is below the remaining thresholds. The normalization of the ID threshold by the mean annual precipitation (MAP) has showed that, in relative terms: (i) the ID threshold is highest in Lisbon Region for duration less than 50 h; (ii) in the north of the country, the ID threshold is more exigent in the Douro Valley than in the NW Mountains and (iii) the ID threshold in Povoação Municipality is lower when compared with the other areas, independently on the considered

  15. Influences of Appalachian orography on heavy rainfall and rainfall variability associated with the passage of hurricane Isabel by ensemble simulations

    Science.gov (United States)

    Oldaker, Guy; Liu, Liping; Lin, Yuh-Lang

    2017-12-01

    This study focuses on the heavy rainfall event associated with hurricane Isabel's (2003) passage over the Appalachian mountains of the eastern United States. Specifically, an ensemble consisting of two groups of simulations using the Weather Research and Forecasting model (WRF), with and without topography, is performed to investigate the orographic influences on heavy rainfall and rainfall variability. In general, the simulated ensemble mean with full terrain is able to reproduce the key observed 24-h rainfall amount and distribution, while the flat-terrain mean lacks in this respect. In fact, 30-h rainfall amounts are reduced by 75% with the removal of topography. Rainfall variability is also significantly increased with the presence of orography. Further analysis shows that the complex interaction between the hurricane and terrain along with contributions from varied microphysics, cumulus parametrization, and planetary boundary layer schemes have a pronounced effect on rainfall and rainfall variability. This study follows closely with a previous study, but for a different TC case of Isabel (2003). It is an important sensitivity test for a different TC in a very different environment. This study reveals that the rainfall variability behaves similarly, even with different settings of the environment.

  16. Simulation of rainfall effects on sediment transport on steep slopes in an Alpine catchment

    Directory of Open Access Journals (Sweden)

    A. Kaiser

    2015-03-01

    Full Text Available The Alps represent a young, high mountain range which displays strong geomorphological activity. As the major source area in Central Europe, they deliver large quantities of sediment to the lowlands. However, our knowledge on process differentiation is still not sufficient to distinguish between the summer and winter periods of denudation. To increase our understanding of soil detachment, artificial rainfall experiments were carried out to generate data for the physically-based soil erosion model EROSION 2D/3D. Additionally, state-of-the-art, close-range remote sensing methods were applied to validate the results. The first rainfall simulations showed promising results for predicting denudation during the summer period, thus indicating the applicability of this experimental approach. However, further research is required for seasonal dynamics during other times of the year.

  17. Fitting monthly Peninsula Malaysian rainfall using Tweedie distribution

    Science.gov (United States)

    Yunus, R. M.; Hasan, M. M.; Zubairi, Y. Z.

    2017-09-01

    In this study, the Tweedie distribution was used to fit the monthly rainfall data from 24 monitoring stations of Peninsula Malaysia for the period from January, 2008 to April, 2015. The aim of the study is to determine whether the distributions within the Tweedie family fit well the monthly Malaysian rainfall data. Within the Tweedie family, the gamma distribution is generally used for fitting the rainfall totals, however the Poisson-gamma distribution is more useful to describe two important features of rainfall pattern, which are the occurrences (dry months) and the amount (wet months). First, the appropriate distribution of the monthly rainfall was identified within the Tweedie family for each station. Then, the Tweedie Generalised Linear Model (GLM) with no explanatory variable was used to model the monthly rainfall data. Graphical representation was used to assess model appropriateness. The QQ plots of quantile residuals show that the Tweedie models fit the monthly rainfall data better for majority of the stations in the west coast and mid land than those in the east coast of Peninsula. This significant finding suggests that the best fitted distribution depends on the geographical location of the monitoring station. In this paper, a simple model is developed for generating synthetic rainfall data for use in various areas, including agriculture and irrigation. We have showed that the data that were simulated using the Tweedie distribution have fairly similar frequency histogram to that of the actual data. Both the mean number of rainfall events and mean amount of rain for a month were estimated simultaneously for the case that the Poisson gamma distribution fits the data reasonably well. Thus, this work complements previous studies that fit the rainfall amount and the occurrence of rainfall events separately, each to a different distribution.

  18. Coping with Rainfall Variability in Northern Tanzania

    DEFF Research Database (Denmark)

    Trærup, Sara Lærke Meltofte

    2012-01-01

    This paper explores a potential relationship between rainfall data and household self-reported harvest shocks and local (spatial) variability of harvest shocks and coping strategies based on a survey of 2700 rural households in the Kagera region of northern Tanzania. In addition, correlations...... of household reported harvest shocks differs significantly between districts and correspond to the observed variability in local climate patterns. Coping strategies are focused on spreading risks and include reduced consumption, casual employment, new crops, external support and the selling of assets....... There are no large differences in applied coping strategies across the region, but district-level data demonstrate how local strategies differ between localities within the districts. The results emphasize that in order to target rural policies and make them efficient, it is important to take into account the local...

  19. A rainfall simulator based on multifractal generator

    Science.gov (United States)

    Akrour, Nawal; mallet, Cecile; barthes, Laurent; chazottes, Aymeric

    2015-04-01

    The Precipitations are due to complex meteorological phenomenon's and unlike other geophysical constituents such as water vapour concentration they present a relaxation behaviour leading to an alternation of dry and wet periods. Thus, precipitations can be described as intermittent process. The spatial and temporal variability of this phenomenon is significant and covers large scales. This high variability can cause extreme events which are difficult to observe properly because of their suddenness and their localized character. For all these reasons, the precipitations are therefore difficult to model. This study aims to adapt a one-dimensional time series model previously developed by the authors [Akrour et al., 2013, 2014] to a two-dimensional rainfall generator. The original time series model can be divided into 3 major steps : rain support generation, intra event rain rates generation using multifractal and finally calibration process. We use the same kind of methodology in the present study. Based on dataset obtained from meteorological radar of Météo France with a spatial resolution of 1 km x 1 km we present the used approach : Firstly, the extraction of rain support (rain/no rain area) allowing the retrieval of the rain support structure function (variogram) and fractal properties. This leads us to use either the rain support modelisation proposed by ScleissXXX [ref] or directly real rain support extracted from radar rain maps. Then, the generation (over rain areas) of rain rates is made thanks to a 2D multifractal Fractionnally Integrated Flux (FIF) model [ref]. This second stage is followed by a calibration/forcing step (forcing average rain rate per events) added in order to provide rain rate coherent with observed rain-rate distribution. The forcing process is based on a relation identified from the average rain rate of observed events and their surfaces. The presentation will first explain the different steps presented above, then some results

  20. Rainfall simulators - innovations seeking rainfall uniformity and automatic flow rate measurements

    Science.gov (United States)

    Bauer, Miroslav; Kavka, Petr; Strouhal, Luděk; Dostál, Tomáš; Krása, Josef

    2016-04-01

    Field rainfall simulators are used worldwide for many experimental purposes, such as runoff generation and soil erosion research. At CTU in Prague a laboratory simulator with swinging nozzles VeeJet has been operated since 2001. Since 2012 an additional terrain simulator is being used with 4 fixed FullJet 40WSQ nozzles with 2,4 m spacing and operating over two simultaneously sprinkled experimental plots sizing 8x2 and 1x1 m. In parallel to other research projects a specific problem was solved: improving rainfall spatial uniformity and overall intensity and surface runoff measurements. These fundamental variables significantly affect investigated processes as well as resulting water balance of the plot, therefore they need to be determined as accurately as possible. Although the original nozzles setting produced (commonly used) Christiansen uniformity index CU over 80 %, detailed measurements proved this index insufficient and showed many unrequired rainfall extremes within the plot. Moreover the number of rainfall intensity scenarios was limited and some of them required problematic multi-pressure operation of the water distribution system. Therefore the simulator was subjected to many substantial changes in 2015. Innovations ranged from pump intensification to control unit upgrade. As essential change was considered increase in number of nozzles to 9 in total and reducing their spacing to 1,2 m. However new uniformity measurements did not bring any significant improvement. Tested scenarios showed equal standard deviations of interpolated intensity rasters and equal or slightly lower CU index. Imperfections of sprinkling nozzles were found to be the limiting factor. Still many other benefits were brought with the new setup. Whole experimental plot 10x2 m is better covered with the rainfall while the water consumption is retained. Nozzles are triggered in triplets, which enables more rainfall intensity scenarios. Water distribution system is more stable due to

  1. The effect of the Madden-Julian Oscillation on station rainfall and river level in the Fly River system, Papua New Guinea

    Science.gov (United States)

    Matthews, Adrian J.; Pickup, Geoff; Peatman, Simon C.; Clews, Peter; Martin, Jason

    2013-10-01

    The Madden-Julian oscillation (MJO) is the dominant mode of intraseasonal variability in tropical rainfall on the large scale, but its signal is often obscured in individual station data, where effects are most directly felt at the local level. The Fly River system, Papua New Guinea, is one of the wettest regions on Earth and is at the heart of the MJO envelope. A 16 year time series of daily precipitation at 15 stations along the river system exhibits strong MJO modulation in rainfall. At each station, the difference in rainfall rate between active and suppressed MJO conditions is typically 40% of the station mean. The spread of rainfall between individual MJO events was small enough such that the rainfall distributions between wet and dry phases of the MJO were clearly separated at the catchment level. This implies that successful prediction of the large-scale MJO envelope will have a practical use for forecasting local rainfall. In the steep topography of the New Guinea Highlands, the mean and MJO signal in station precipitation is twice that in the satellite Tropical Rainfall Measuring Mission 3B42HQ product, emphasizing the need for ground-truthing satellite-based precipitation measurements. A clear MJO signal is also present in the river level, which peaks simultaneously with MJO precipitation input in its upper reaches but lags the precipitation by approximately 18 days on the flood plains.

  2. Elevated CO2 and warming effects on grassland plant mortality are determined by the timing of rainfall.

    Science.gov (United States)

    Hovenden, Mark J; Newton, Paul C D; Porter, Meagan

    2017-05-01

    Global warming is expected to increase the mortality rate of established plants in water-limited systems because of its effect on evapotranspiration. The rising CO 2 concentration ([CO 2 ]), however, should have the opposite effect because it reduces plant transpiration, delaying the onset of drought. This potential for elevated [CO 2 ] (eCO 2 ) to modify the warming effect on mortality should be related to prevailing moisture conditions. This study aimed to determine the impacts of warming by 2 °C and eCO 2 (550 μmol mol -1 ) on plant mortality in an Australian temperate grassland over a 6-year period and to test how interannual variation in rainfall influenced treatment effects. Analyses were based on results from a field experiment, TasFACE, in which grassland plots were exposed to a combination of eCO 2 by free air CO 2 enrichment (FACE) and warming by infrared heaters. Using an annual census of established plants and detailed estimates of recruitment, annual mortality of all established plants was calculated. The influence of rainfall amount and timing on the relative impact of treatments on mortality in each year was analysed using multiple regression techniques. Warming and eCO 2 effects had an interactive influence on mortality which varied strongly from year to year and this variation was determined by temporal rainfall patterns. Warming tended to increase density-adjusted mortality and eCO 2 moderated that effect, but to a greater extent in years with fewer dry periods. These results show that eCO 2 reduced the negative effect of warming but this influence varied strongly with rainfall timing. Importantly, indices involving the amount of rainfall were not required to explain interannual variation in mortality or treatment effects on mortality. Therefore, predictions of global warming effects on plant mortality will be reliant not only on other climate change factors, but also on the temporal distribution of rainfall.

  3. Application of the rainfall infiltration breakthrough (RIB) model for ...

    African Journals Online (AJOL)

    Application of the rainfall infiltration breakthrough (RIB) model for groundwater recharge estimation in west coastal South Africa. ... the data from Oudebosch with different rainfall and groundwater abstraction inputs are simulated to explore individual effects on water levels as well as recharge rate estimated on a daily basis.

  4. Spatio-temporal variability of summer monsoon rainfall over Orissa ...

    Indian Academy of Sciences (India)

    on the performance of monsoon rainfall over India. The southwest sector of a monsoon depression gets more rainfall due to maximum low level conver- gence and vertical motion (Rajamani and Rao. 1981). Dhar et al (1981) have noted a significant relationship of tropical disturbances (depression and cyclonic storms) only ...

  5. Gridded daily Indian monsoon rainfall for 14 seasons: Merged ...

    Indian Academy of Sciences (India)

    grid consists of around 1250 grid points. Daily IMD analysed rainfall values at these 1250 grids are con- sidered as proxy gauge data for our 1. ◦ lat./long. resolution merged satellite gauge rainfall analysis for the Indian monsoon region. Since the basic gauge analysed data is at 0.5. ◦ lat./long. resolution, we decided to make ...

  6. Variability in Rainfall, Temperature and Relative Humidity at Bahir ...

    African Journals Online (AJOL)

    This study was conducted to assess change in rainfall, temperature and relative humidity at Bahir Dar city in relation to global climate change. The study focused on analyzing changes in meteorological data, specifically temperature, rainfall and relative humidity. Bahir Dar city was selected due to its proximity to Lake Tana ...

  7. Application of the rainfall infiltration breakthrough (RIB) model for ...

    African Journals Online (AJOL)

    2012-05-23

    May 23, 2012 ... rec har ge. (m m. ) W ater lev el fluc tuation. (m. ) Months of simulation rainfall. Recharge amount. WLF dh(crd) dh(rib). (c) TMG544. Figure 4. Daily/monthly rainfall, observed. WLF as well as calculated WLF and groundwater recharge in Riverlands and Oudebosch obtained from the. RIB model and CRD.

  8. Post-Adaptation Vulnerability of Cereals to Rainfall and ...

    African Journals Online (AJOL)

    USER

    2014-09-04

    Sep 4, 2014 ... challenges on a global scale (Scholze et al.,. 2006; Mendelsohn et al., 2006). Climate change have ... stress, longer dry seasons and uncertain rainfall patterns putting areas that depend strictly on rainfall ..... season as the greatest hindrance to increased yield of cereals which is more serious in the northern ...

  9. The impact of Amazonian deforestation on Amazon basin rainfall

    Science.gov (United States)

    Spracklen, D. V.; Garcia-Carreras, L.

    2015-11-01

    We completed a meta-analysis of regional and global climate model simulations (n = 96) of the impact of Amazonian deforestation on Amazon basin rainfall. Across all simulations, mean (±1σ) change in annual mean Amazon basin rainfall was -12 ± 11%. Variability in simulated rainfall was not explained by differences in model resolution or surface parameters. Across all simulations we find a negative linear relationship between rainfall and deforestation extent, although individual studies often simulate a nonlinear response. Using the linear relationship, we estimate that deforestation in 2010 has reduced annual mean rainfall across the Amazon basin by 1.8 ± 0.3%, less than the interannual variability in observed rainfall. This may explain why a reduction in Amazon rainfall has not consistently been observed. We estimate that business-as-usual deforestation (based on deforestation rates prior to 2004) would lead to an 8.1 ± 1.4% reduction in annual mean Amazon basin rainfall by 2050, greater than natural variability.

  10. Probabilistic Analysis of Peak Daily Rainfall for Prediction purposes ...

    African Journals Online (AJOL)

    The obtained peak daily rainfall values were subjected to Gumbel, Log-Gumbel, Normal, Log-Normal, Pearson and Log-Pearson probability distributions. Mathematical equation for probability distribution functions were established for each town and used to predict peak rainfall. The predicted values were subjected to ...

  11. Fractal analysis of rainfall occurrence observed in the synoptic ...

    African Journals Online (AJOL)

    Fractal analysis is important for characterizing and modeling rainfall's space-time variations in hydrology. The purpose of this study consists on determining, in a mono-fractal framework, the scale invariance of rainfall series in Benin synopticstations located in two main geographical area: Cotonou, Bohicon , Savè in a sub ...

  12. Assessment of the Growing Season over the Unimodal Rainfall ...

    African Journals Online (AJOL)

    Most part of Tanzania experiences unimodal rainfall. The characteristics of rainfall such as its onset and cessation dates, dry and wet spell lengths, frequency and number of rainy days can be, used to determine the nature of growing season length of growing season end of season and its geographical variation both ...

  13. Rainfall response to Dam/Irrigation projects in Northern Nigeria ...

    African Journals Online (AJOL)

    In this paper, we examine the possibility that the increasing number and size of dam/irrigation projects in northern Nigeria are having a corresponding increase in rainfall in spite of the threat of climate change. We modeled the rainfall trends over 11 meteorological stations over a period of 34 years (1971 - 2004). The trends ...

  14. Fitting the Statistical Distribution for Daily Rainfall in Ibadan, Based ...

    African Journals Online (AJOL)

    PROF. O. E. OSUAGWU

    2013-06-01

    Jun 1, 2013 ... followed by normal and poisson model that has the same estimated rainfall amount for describing the daily rainfall in Ibadan metropolis. Keywords : scale parameter, asymptotically, exponential distribution, gamma distribution, poisson and kolmogorov-smirnov. .... Equation (7) can be simply written as.

  15. Rainfall intensity effects on crusting and mode of seedling ...

    African Journals Online (AJOL)

    Predicted changes in rainfall intensity due to climate change are likely to influence key soil health parameters, especially structural attributes and crop growth. Variations in rainfall intensity will impact crop ... and growth in these soils. Keywords: climate change, crusting, mineralogy, penetration resistance, soil organic matter ...

  16. Seasonal prediction of summer monsoon rainfall over cluster ...

    Indian Academy of Sciences (India)

    Shared nearest neighbour (SNN) cluster algorithm has been applied to seasonal (June–September) rainfall departures over 30 sub-divisions of India to identify the contiguous homogeneous cluster regions over India. Five cluster regions are identified. Rainfall departure series for these cluster regions are prepared by area ...

  17. Trends in Moderate Rainfall Extremes : A Regional Monotone Regression Approach

    NARCIS (Netherlands)

    Roth, M.; Buishand, T.A.; Jongbloed, G.

    2015-01-01

    Rainfall extremes are thought to have increased over recent years. Typically linear trends have been considered to describe the temporal evolution of high quantiles of the daily rainfall distribution. For long records it is important to allow more flexibility. Quantile regression methods are

  18. Dynamic Hydrological Modeling in Drylands with TRMM Based Rainfall

    Directory of Open Access Journals (Sweden)

    Elena Tarnavsky

    2013-12-01

    Full Text Available This paper introduces and evaluates DryMOD, a dynamic water balance model of the key hydrological process in drylands that is based on free, public-domain datasets. The rainfall model of DryMOD makes optimal use of spatially disaggregated Tropical Rainfall Measuring Mission (TRMM datasets to simulate hourly rainfall intensities at a spatial resolution of 1-km. Regional-scale applications of the model in seasonal catchments in Tunisia and Senegal characterize runoff and soil moisture distribution and dynamics in response to varying rainfall data inputs and soil properties. The results highlight the need for hourly-based rainfall simulation and for correcting TRMM 3B42 rainfall intensities for the fractional cover of rainfall (FCR. Without FCR correction and disaggregation to 1 km, TRMM 3B42 based rainfall intensities are too low to generate surface runoff and to induce substantial changes to soil moisture storage. The outcomes from the sensitivity analysis show that topsoil porosity is the most important soil property for simulation of runoff and soil moisture. Thus, we demonstrate the benefit of hydrological investigations at a scale, for which reliable information on soil profile characteristics exists and which is sufficiently fine to account for the heterogeneities of these. Where such information is available, application of DryMOD can assist in the spatial and temporal planning of water harvesting according to runoff-generating areas and the runoff ratio, as well as in the optimization of agricultural activities based on realistic representation of soil moisture conditions.

  19. On the asymmetric distribution of shear-relative typhoon rainfall

    Science.gov (United States)

    Gao, Si; Zhai, Shunan; Li, Tim; Chen, Zhifan

    2018-02-01

    The Tropical Rainfall Measuring Mission (TRMM) 3B42 precipitation, the National Centers for Environmental Prediction (NCEP) Final analysis and the Regional Specialized Meteorological Center (RSMC) Tokyo best-track data during 2000-2015 are used to compare spatial rainfall distribution associated with Northwest Pacific tropical cyclones (TCs) with different vertical wind shear directions and investigate possible mechanisms. Results show that the maximum TC rainfall are all located in the downshear left quadrant regardless of shear direction, and TCs with easterly shear have greater magnitudes of rainfall than those with westerly shear, consistent with previous studies. Rainfall amount of a TC is related to its relative position and proximity from the western Pacific subtropical high (WPSH) and the intensity of water vapor transport, and low-level jet is favorable for water vapor transport. The maximum of vertically integrated moisture flux convergence (MFC) are located on the downshear side regardless of shear direction, and the contribution of wind convergence to the total MFC is far larger than that of moisture advection. The cyclonic displacement of the maximum rainfall relative to the maximum MFC is possibly due to advection of hydrometeors by low- and middle-level cyclonic circulation of TCs. The relationship between TC rainfall and the WPSH through water vapor transport and vertical wind shear implies that TC rainfall may be highly predictable given the high predictability of the WPSH.

  20. Spatio-temporal variability of summer monsoon rainfall over Orissa ...

    Indian Academy of Sciences (India)

    The summer monsoon rainfall over Orissa occurs mostly due to low pressure systems (LPS)developing over the Bay of Bengal and moving along the monsoon trough.A study is hence undertaken to find out characteristic features of the relationship between LPS over different regions and rainfall over Orissa during the ...