WorldWideScience

Sample records for african equatorial rain

  1. Sulfur gases and aerosols in and above the equatorial African rain forest

    Science.gov (United States)

    Bingemer, H. G.; Andreae, M. O.; Andreae, T. W.; Artaxo, P.; Helas, G.; Jacob, D. J.; Mihalopoulos, N.; Nguyen, B. C.

    1992-04-01

    The distribution of gaseous and particulate sulfur compounds in the canopy of the tropical rain forest of northern Congo and the overlying atmosphere was determined during February 12-25, 1988. Hydrogen sulfide and dimethylsulfide decayed exponentially with altitude from approximately 30-40 ppt at ground level to 3-5 ppt at around 3 km altitude. Emission fluxes from the forest to the atmosphere were estimated by fitting a one-dimensional time-dependent numerical model of chemistry and transport of the sulfur compounds to their observed vertical profiles. Emission fluxes of 0.6-1.0 nmol H2S/sq m per min and 0.3-0.7 nmol DMS/sq m per min were consistent with the observed vertical profiles of H2S and DMS. These fluxes compare well with fluxes reported previously for the Amazon rain forest during the dry season and support the view of a subordinate role of land biota in the global cycling of sulfur. The particulate sulfur concentration of 248 ppt was found below the forest canopy. Biomass burning is considered to be an important contributor to this particulate sulfur. Carbonyl sulfide was found to be enhanced above the 500 ppt tropospheric background throughout the mixing layer of 2-3 km depth, likely due to biomass burning.

  2. Investigation of TEC variations over the magnetic equatorial and equatorial anomaly regions of the African sector

    Science.gov (United States)

    Oryema, B.; Jurua, E.; D'ujanga, F. M.; Ssebiyonga, N.

    2015-11-01

    This paper presents the annual, seasonal and diurnal variations in ionospheric TEC along the African equatorial region. The study also investigated the effects of a geomagnetic storm on ionospheric TEC values. Dual-frequency GPS derived TEC data obtained from four stations within the African equatorial region for the high solar activity year 2012 were used in this study. Annual variations showed TEC having two peaks in the equinoctial months, while minima values were observed in the summer and winter solstices. The diurnal pattern showed a pre-dawn minimum, a steady increase from about sunrise to an afternoon maximum and then a gradual fall after sunset to attain a minimum just before sunrise. Nighttime enhancements of TEC were observed mostly in the equinoctial months. There was comparably higher percentage TEC variability during nighttime than daytime and highest during equinoxes, moderate in winter and least during summer solstice. TEC was observed to exhibit a good correlation with geomagnetic storm indices.

  3. Disturbance, diversity and distributions in Central African rain forest

    NARCIS (Netherlands)

    Gemerden, van B.S.

    2004-01-01

    The aim of this study is to gain insight in the impact of human land use on plant community composition, diversity and levels of endemism in Central African rain forest. Human disturbance in this region is causing large-scale habitat degradation. The two most widespread forms of land use are selecti

  4. Evidence of Late Palaeocene-Early Eocene equatorial rain forest refugia in southern Western Ghats, India

    Indian Academy of Sciences (India)

    V Prasad; A Farooqui; S K M Tripathi; R Garg; B Thakur

    2009-11-01

    Equatorial rain forests that maintain a balance between speciation and extinction are hot-spots for studies of biodiversity. Western Ghats in southern India have gained attention due to high tropical biodiversity and endemism in their southern most area. We attempted to track the affinities of the pollen flora of the endemic plants of Western Ghat area within the fossil palynoflora of late Palaeocene-early Eocene (∼55–50 Ma) sedimentary deposits of western and northeastern Indian region. The study shows striking similarity of extant pollen with twenty eight most common fossil pollen taxa of the early Palaeogene. Widespread occurrences of coal and lignite deposits during early Palaeogene provide evidence of existence of well diversified rain forest community and swampy vegetation in the coastal low lying areas all along the western and northeastern margins of the Indian subcontinent. Prevalence of excessive humid climate during this period has been seen as a result of equatorial positioning of Indian subcontinent, superimposed by a long term global warming phase (PETM and EECO) during the early Palaeogene. The study presents clear evidence that highly diversified equatorial rain forest vegetation once widespread in the Indian subcontinent during early Palaeogene times, are now restricted in a small area as a refugia in the southernmost part of the Western Ghat area. High precipitation and shorter periods of dry months seem to have provided suitable environment to sustain lineages of ancient tropical vegetation in this area of Western Ghats in spite of dramatic climatic changes subsequent to the post India-Asia collision and during the Quaternary and Recent times.

  5. Rain ratio variation in the Tropical Ocean: Tests with surface sediments in the eastern equatorial Pacific

    Science.gov (United States)

    Mekik, Figen; Loubere, Paul; Richaud, Mathieu

    2007-03-01

    The organic carbon to calcite flux ratio (rain ratio) has a profound effect on the preservation of carbonates in the deep sea and may influence atmospheric pCO 2 over millennia. Unfortunately, the degree to which the rain ratio varies in the more productive regions of the oceans is not well determined with sediment trap data. The rain ratio in the upper ocean appears dominantly linked to diatom productivity, which is not necessarily directly linked to total production and may be regionally variable. However, ballasting and protection of organic carbon by calcareous particles in the deeps may limit ratio variability at the seafloor. Sediment trap data do not exist for the regional determination of rain ratios in key highly productive areas like the eastern equatorial Pacific (EEP). To overcome this, we turn to surface sediment composition and accumulation rates as a representation of modern ratio variation. We present 230Thorium ( 230Th)-normalized carbonate, opal, organic carbon and detrital matter accumulation rates from core top samples in the EEP. We demonstrate a novel approach for estimating modern rain ratios from sedimentary proxies by (1) calculating vertical calcite flux from 230Th-normalized carbonate accumulation rates (CARs) with correction for preservation and (2) calculating organic carbon fluxes with multiple algorithms that depend in varying degrees on ballasting. We find that organic carbon flux estimates from algorithms with and without a ballasting function produce results different from one another. Sediment accumulation rates for opal reflect the likely pattern of diatom production. By contrast, the organic carbon accumulation rate does not correlate well with surface ocean productivity or any of our algorithm-based organic carbon flux estimates. Instead, it correlates with the detrital component of the sediments suggesting an allochthonous input to sedimentary organic carbon accumulation in the EEP, which reduces its value as a productivity

  6. Surface response to rain events throughout the West African monsoon

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    F. Lohou

    2013-07-01

    Full Text Available This study analyses the response of the continental surface to a rain event, taking advantage of the long-term near-surface measurements over different vegetation covers at different latitudes, acquired during the African Monsoon Multidisciplinary Analysis (AMMA experiment. The simulated surface response by nine land surface models involved in AMMA Land Model Intercomparison Project (ALMIP, is compared to the observations. The surface response, described via the evaporative fraction, evolves in two steps: the immediate surface response and the surface recovery. The immediate surface response corresponds to an increase in the evaporative fraction occurring immediately after the rain. For all the experimental sites, the immediate surface response is strongest when the surface is relatively dry. From the simulation point of view, this relationship is highly model and latitude dependent. The recovery period, characterized by a decrease of the evaporative fraction during several days after the rain, follows an exponential relationship whose rate is vegetation dependent: from 1 day over bare soil to 70 days over the forest. Land surface models correctly simulate the decrease of EF over vegetation covers whereas a slower and more variable EF decrease is simulated over bare soil.

  7. A multi-model approach to the Atlantic Equatorial mode: impact on the West African monsoon

    Energy Technology Data Exchange (ETDEWEB)

    Losada, T.; Rodriguez-Fonseca, B. [Universidad Complutense de Madrid, Madrid (Spain); Janicot, S.; Gervois, S. [LOCEAN/IPSL, CNRS, Universite Pierre et Marie Curie, Paris (France); Chauvin, F. [GAME/CNRM, Meteo-France/CNRS, Toulouse (France); Ruti, P. [Progetto Speciale Clima Globale, Ente Nazionale per le NuoveTecnologie, Rome (Italy)

    2010-07-15

    This paper is focused on the West African anomalous precipitation response to an Atlantic Equatorial mode whose origin, development and damping resembles the observed one during the last decades of the XXth century. In the framework of the AMMA-EU project, this paper analyses the atmospheric response to the Equatorial mode using a multimodel approach with an ensemble of integrations from 4 AGCMs under a time varying Equatorial SST mode. The Guinean Gulf precipitation, which together with the Sahelian mode accounts for most of the summer West African rainfall variability, is highly coupled to this Equatorial Atlantic SST mode or Atlantic Nino. In a previous study, done with the same models under 1958-1997 observed prescribed SSTs, most of the models identify the Equatorial Atlantic SST mode as the one most related to the Guinean Gulf precipitation. The models response to the positive phase of equatorial Atlantic mode (warm SSTs) depicts a direct impact in the equatorial Atlantic, leading to a decrease of the local surface temperature gradient, weakening the West African Monsoon flow and the surface convergence over the Sahel. (orig.)

  8. Multifractal analysis of African monsoon rain fields, taking into account the zero rain-rate problem

    Science.gov (United States)

    Verrier, S.; de Montera, L.; Barthès, L.; Mallet, C.

    2010-07-01

    SummaryNonlinear rain dynamics, due to strong coupling with turbulence, can be described by stochastic scale invariant (such as multifractal) models. In this study, attention is focused on the three-parameter fractionally integrated flux (FIF), based on the universal multifractal (UM) model developed by Schertzer and Lovejoy (1987). Multifractal analysis techniques were applied to experimental radar data measured during the African monsoon multidisciplinary analysis (AMMA) campaign, during the summer of 2006. The non-conservation parameter H, which has often been estimated at 0, was found to be more likely close to 0.4, meaning that rain is not a conserved cascade. Moreover, it is shown that the presence of numerous zero values in the data has an influence, which has until now been underestimated, but should in fact be accounted for. UM parameters are therefore estimated from the full dataset, and then only from maps in which almost all pixels have a non-zero value. Significant differences were found, attributed to on-off intermittency, and their role was checked by means of simulations. Finally, these results are compared with those previously based on time series, and collected by a co-localized disdrometer. The sets of parameters obtained in the spatial and time domains are found to be quite close to each other, contrary to most results published in the literature. This generally reported incoherency is believed to result mainly from the influence of on-off intermittency, whose effects are stronger for time series than for selected radar maps.

  9. Validation of the TEC2F2 model over the African equatorial region

    Science.gov (United States)

    Ssessanga, Nicholas

    2016-06-01

    In this paper a statistical method, TEC2F2, of estimating critical F2 layer frequency (foF2) from Global Positioning System (GPS) Vertical Total Electron content (VTEC) is extended from Africa's mid-latitudes to the equatorial region, and the results validated. The equatorial region is one of the most dynamic yet under-represented over Africa in ionospheric studies. The TEC2F2 method was first considered for the South African region (mid-latitudes). This region is covered by a network of ionosondes that provided a validation platform for the TEC2F2 method before being applied to other parts of Africa. The results show that over the African equatorial region, the TEC2F2 method is a potential candidate in more accurately estimating the foF2 parameter than the most recent version of the International Reference Ionosphere (IRI-2012) model.

  10. Molecular phylogenetics reveal multiple tertiary vicariance origins of the African rain forest trees

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    Sosef Marc SM

    2008-12-01

    Full Text Available Abstract Background Tropical rain forests are the most diverse terrestrial ecosystems on the planet. How this diversity evolved remains largely unexplained. In Africa, rain forests are situated in two geographically isolated regions: the West-Central Guineo-Congolian region and the coastal and montane regions of East Africa. These regions have strong floristic affinities with each other, suggesting a former connection via an Eocene pan-African rain forest. High levels of endemism observed in both regions have been hypothesized to be the result of either 1 a single break-up followed by a long isolation or 2 multiple fragmentation and reconnection since the Oligocene. To test these hypotheses the evolutionary history of endemic taxa within a rain forest restricted African lineage of the plant family Annonaceae was studied. Molecular phylogenies and divergence dates were estimated using a Bayesian relaxed uncorrelated molecular clock assumption accounting for both calibration and phylogenetic uncertainties. Results Our results provide strong evidence that East African endemic lineages of Annonaceae have multiple origins dated to significantly different times spanning the Oligocene and Miocene epochs. Moreover, these successive origins (c. 33, 16 and 8 million years – Myr coincide with known periods of aridification and geological activity in Africa that would have recurrently isolated the Guineo-Congolian rain forest from the East African one. All East African taxa were found to have diversified prior to Pleistocene times. Conclusion Molecular phylogenetic dating analyses of this large pan-African clade of Annonaceae unravels an interesting pattern of diversification for rain forest restricted trees co-occurring in West/Central and East African rain forests. Our results suggest that repeated reconnections between the West/Central and East African rain forest blocks allowed for biotic exchange while the break-ups induced speciation via vicariance

  11. Investigating the effect of geomagnetic storm and equatorial electrojet on equatorial ionospheric irregularity over East African sector

    Science.gov (United States)

    Seba, Ephrem Beshir; Nigussie, Melessew

    2016-11-01

    The variability of the equatorial ionosphere is still a big challenge for ionospheric dependent radio wave technology users. To mitigate the effect of equatorial ionospheric irregularity on trans-ionospheric radio waves considerable efforts are being done to understand and model the equatorial electrodynamics and its connection to the creation of ionospheric irregularity. However, the effect of the East-African ionospheric electrodynamics on ionospheric irregularity is not yet well studied due to lack of multiple ground based instruments. But, as a result of International Heliophysical Year (IHY) initiative, which was launched in 2007, some facilities are being deployed in Africa since then. Therefore, recently deployed instruments, in the Ethiopian sector, such as SCINDA-GPS receiver (2.64°N dip angle) for TEC and amplitude scintillation index (S4) data and two magnetometers, which are deployed on and off the magnetic equator, data collected in the March equinoctial months of the years 2011, 2012, and 2015 have been used for this study in conjunction with geomagnetic storm data obtained from high resolution OMNI WEB data center. We have investigated the triggering and inhibition mechanisms for ionospheric irregularities using, scintillation index (S4), equatorial electrojet (EEJ), interplanetary electric field (IEFy), symH index, AE index and interplanetary magnetic field (IMF) Bz on five selected storm and two storm free days. We have found that when the eastward EEJ fluctuates in magnitude due to storm time induced electric fields at around noontime, the post-sunset scintillation is inhibited. All observed post-sunset scintillations in equinox season are resulted when the daytime EEJ is non fluctuating. The strength of noontime EEJ magnitude has shown direct relation with the strength of the post-sunset scintillations. This indicates that non-fluctuating EEJ stronger than 20 nT, can be precursor for the occurrence of the evening time ionospheric irregularities

  12. Possible causes of the Central Equatorial African long-term drought

    Science.gov (United States)

    Hua, Wenjian; Zhou, Liming; Chen, Haishan; Nicholson, Sharon E.; Raghavendra, Ajay; Jiang, Yan

    2016-12-01

    Previous studies found that Central Equatorial Africa (CEA) has experienced a long-term drying trend over the past two decades. To further evaluate this finding, we investigate possible mechanisms for this drought by analyzing multiple sources of observations and reanalysis data. We examine the atmospheric circulation changes related to sea surface temperature (SST) variations that control the equatorial African rainfall. Our results indicate that the long-term drought during April, May and June over CEA may reflect the large-scale response of the atmosphere to tropical SST variations. Likely the drought results primarily from SST variations over Indo-Pacific associated with the enhanced and westward extended tropical Walker circulation. These are consistent with the weakened ascent over Central Africa that is associated with the reduced low-level moisture transport. The large-scale atmospheric circulation changes associated with a weaker West African monsoon also have some contribution. These results reinforce the notion that tropical SSTs have large impacts on rainfall over equatorial Africa and highlight the need to further distinguish the contribution of SSTs changes (e.g., La Niña-like pattern and Indian Ocean warming) due to natural variability and anthropogenic forcing to the drought.

  13. From the African Coast, the invention of two territories: Equatorial Guinea and Ivory Coast

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    Adjoa Nathalie Chiyé Kessé

    2014-08-01

    Full Text Available From the African coast starts Latin American history and part of Europe’s. This article includes a comprehensive analysis on the cultural influence of Africa especially Equatorial Guinea and Côte d’Ivoire in Latin America. From the first European incursions into African coast (xvi century and throughout the colonial era, the paper highlights interethnic relations that occurred following the meeting and coexistence between cultures of both continents, an analysis that is essential to study the survival of traditions, beliefs and African customs that survive today in many regions of Latin America. Considering the importance now given to the recovery of identity traits of the past for studies of multi-ethnicity and re-construction of identities, this article can be used by researchers at Afro-descendance, notable in Latin America, whose research is related to African identity traits in their respective nations. Equatorial Guinea was a Spanish colony along with the Protectorate of Morocco and Western Sahara. The duration of this colony ran from 1885 to 1968. In 1926, it became the Spanish Guinea, and in 1968 it acquired its independance from Spain while retaining the Spanish cultural architecture. Furthermore, the French presence in this first stage of the conquest in Côte d’Ivoire, is provided by the army. The colonial authorities in Paris were not yet sufficiently organized to move their representatives to what was then known as the Poor or Bad People Coast or Coast of teeth. It was the military from Senegal, as base of the French colonial army who assumed the conquest and organization of the Ivorian territory for immediate exploitation of economic resources. It is this improvised framework without legal planning, which led to the idea of the invention of Africa supported by Valentin Mudimbe (1988 and Achille Mbembe (2000.

  14. Hydroclimatogical Changes and Impacts on Seasonal Regimes of African Equatorial Rivers

    Science.gov (United States)

    Mahe, G. M.

    2015-12-01

    In recent decades, changes in the pattern of hydroclimatogical cycle have been observed with impacts on seasonal regimes of African equatorial rivers. This communication reports on studies carried out for a set of river basins in equatorial Africa, tributaries of the Atlantic Gulf of Guinea: the Ogooue River in Gabon, the Kouilou River in Congo, and the basins of South Cameroon. These rivers are compared to the Congo River. A new monthly gridded rainfall dataset, and streamflow from selected rivers where used in the analysis. The observed changes include changes in seasonal pattern of rainfall and changes in monthly streamflow regimes. The study shows a decrease of rainfall in the southern hemisphere during February to May since the end of the 80s, while the decrease is much more limited in the Northern hemisphere. For the equatorial rivers, the March-June flood decreased steadily between the 70s and 80s, in correlation with a slight decrease of the rainfall between March and June, while the October-December flood showed no change. This trend was confirmed during the 2000s for the Ogooue River from updated times series, including a shift of the maximum in April instead of May. Locally, the dry season (July-September) disappeared on the coastal basin of the Kienke River at Kribi in Cameroon. It seems that these two months of July and August have become part of a 'single' large rainy season instead of separating the former two rainy seasons. A slight decrease in seasonal rainfall together with a small change in the intra-seasonal rainfall distribution, most probably led to one of the biggest change in hydrological regimes in Equatorial Africa, which could be a clue to understanding climate change in the region. This rainfall change is different for the Congo River which large basins integrates various climatic forcings.

  15. Fungus-Growing Termites Originated in African Rain Forest

    DEFF Research Database (Denmark)

    Aanen, Duur Kornelis; Eggleton, Paul

    2005-01-01

    are consumed (cf. [ [1] and [2] ]). Fungus-growing termites are found throughout the Old World tropics, in rain forests and savannas, but are ecologically dominant in savannas [ 3 ]. Here, we reconstruct the ancestral habitat and geographical origin of fungus-growing termites. We used a statistical model......Fungus-growing termites (subfamily Macrotermitinae, Isoptera) cultivate fungal crops (genus Termitomyces, Basidiomycotina) in gardens inside their colonies. Those fungus gardens are continuously provided with plant substrates, whereas older parts that have been well decomposed by the fungus...... extant savanna species are found in most genera, this moreover suggests that the savanna has repeatedly been colonized by fungus-growing termites. Furthermore, at least four independent "out-of-Africa" migrations into Asia, and at least one independent migration to Madagascar, have occurred. Although...

  16. Taxonomy of Atlantic Central African Orchids 1. A New Species of Angraecum set. Pectinaria (Orchidaceae) from Gabon and Equatorial Guinea.

    NARCIS (Netherlands)

    Stévart, T.; Cawoy, V.; Damen, T.H.J.; Droissart, V.

    2010-01-01

    During a recent survey of Atlantic central African orchids, we collected four orchid specimens in Rio Muni (Equatorial Guinea) that share the general morphology of Angraecum gabonense, the most frequent member of Angraecum section Pectinaria in Central Africa, but differ in leaf shape and flower siz

  17. Western equatorial African forest-savanna mosaics: a legacy of late Holocene climatic change?

    Directory of Open Access Journals (Sweden)

    A. Ngomanda

    2009-10-01

    Full Text Available Past vegetation and climate changes reconstructed using two pollen records from Lakes Maridor and Nguène, located in the coastal savannas and inland rainforest of Gabon, respectively, provide new insights into the environmental history of western equatorial African rainforests during the last 4500 cal yr BP. These pollen records indicate that the coastal savannas of western equatorial Africa did not exist during the mid-Holocene and instead the region was covered by evergreen rainforests. From ca. 4000 cal yr BP a progressive decline of inland evergreen rainforest, accompanied by the expansion of semi-deciduous rainforest, occurred synchronously with grassland colonisation in the coastal region of Gabon. The contraction of moist evergreen rainforest and the establishment of coastal savannas in Gabon suggest decreasing humidity from ca. 4000 cal yr BP. The marked reduction in evergreen rainforest and subsequent savanna expansion was followed from 2700 cal yr BP by the colonization of secondary forests dominated by the palm, Elaeis guineensis, and the shrub, Alchornea cordifolia (Euphorbiaceae. A return to wetter climatic conditions from about 1400 cal yr BP led to the renewed spread of evergreen rainforest inland, whereas a forest-savanna mosaic still persists in the coastal region. There is no evidence to suggest that the major environmental changes observed were driven by human impact.

  18. Western equatorial African forest-savanna mosaics: a legacy of late Holocene climatic change?

    Science.gov (United States)

    Ngomanda, A.; Chepstow-Lusty, A.; Makaya, M.; Favier, C.; Schevin, P.; Maley, J.; Fontugne, M.; Oslisly, R.; Jolly, D.

    2009-10-01

    Past vegetation and climate changes reconstructed using two pollen records from Lakes Maridor and Nguène, located in the coastal savannas and inland rainforest of Gabon, respectively, provide new insights into the environmental history of western equatorial African rainforests during the last 4500 cal yr BP. These pollen records indicate that the coastal savannas of western equatorial Africa did not exist during the mid-Holocene and instead the region was covered by evergreen rainforests. From ca. 4000 cal yr BP a progressive decline of inland evergreen rainforest, accompanied by the expansion of semi-deciduous rainforest, occurred synchronously with grassland colonisation in the coastal region of Gabon. The contraction of moist evergreen rainforest and the establishment of coastal savannas in Gabon suggest decreasing humidity from ca. 4000 cal yr BP. The marked reduction in evergreen rainforest and subsequent savanna expansion was followed from 2700 cal yr BP by the colonization of secondary forests dominated by the palm, Elaeis guineensis, and the shrub, Alchornea cordifolia (Euphorbiaceae). A return to wetter climatic conditions from about 1400 cal yr BP led to the renewed spread of evergreen rainforest inland, whereas a forest-savanna mosaic still persists in the coastal region. There is no evidence to suggest that the major environmental changes observed were driven by human impact.

  19. Mesozoic Source-to-Sink of the African margin of the Equatorial Atlantic

    Science.gov (United States)

    ye, jing; Chardon, Dominique; rouby, delphine; Guillocheau, François; Robin, Cecile; Loparev, Artiom; Huyghe, damien; Dall'Asta, Massimo; Brown, Roderick; wildman, mark; webster, david

    2016-04-01

    The objective of the Transform Source to Sink Project (TS2P) is to link the dynamics of the erosion of the West African Craton to the offshore sedimentary basins of the African margin of the Equatorial Atlantic at geological time scales. This margin, alternating transform and oblique segments from Guinea to Nigeria, shows a strong structural variability in the margin width, continental geology and relief, drainage networks and subsidence/accumulation patterns. We analyzed this system combining onshore geology and geomorphology as well as offshore sub-surface data. We produced paleogeographic maps at the scale of West Africa spanning the continental domain and offshore basins since 200 Ma. Mapping spatial and temporal distribution of domains either in erosion (sources) or in accumulation (sinks) document the impact of the successive rifting of Central and Equatorial Atlantic on the physiography of the area. We use low temperature thermochronology dating along three transects perpendicular to the margin (Guinea, Ivory Coast and Benin) to determine periods and domains of denudation in that framework. We compare these data to the Mesozoic accumulation histories in passive margin basins and discuss their stratigraphic expression according to the type of margin segment they are preserved in. Syn-rift architectures (Early Cretaceous) are largely impacted by transform faults that define sub-basins with contrasted width of crustal necking zone (narrower in transform segments than in oblique/normal segments). During the Late Cretaceous post-rift, sedimentary wedges record a transgression along the all margin. Proximal parts of the sedimentary wedge are preserved in basins developing on segments with wide crustal necking zone while they were eroded away in basins developing on narrow segments. As a difference, the Cenozoic wedge is everywhere preserved across the whole width of the margin.

  20. Interannual modulation of East African early short rains by the winter Arctic Oscillation

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    Gong, Dao-Yi; Guo, Dong; Mao, Rui; Yang, Jing; Gao, Yongqi; Kim, Seong-Joong

    2016-08-01

    In the present study, we analyzed the interannual linkage between the boreal winter Arctic Oscillation (AO) and East African early short rains. When the Indian Ocean Dipole and El Niño-Southern Oscillation variance are excluded by linear regression, the boreal winter AO index is significantly correlated with the October East African precipitation over the domain of 5°N-5°S and 35°-45°E for the period 1979-2014, r =+ 0.46. The upper ocean heat content likely acts as a medium that links the AO and East African precipitation. Significant subsurface warming and positive upper ocean heat content anomalies occur over the western Indian Ocean during the autumn following positive AO winters, which enriches the atmospheric moisture, intensifies convection, and enhances precipitation. Oceanic dynamics play a key role in causing this subsurface warming. Winter AO-related atmospheric circulation creates anomalous wind stress, which forces a downwelling oceanic Rossby wave between 60°-75°E and 5°-10°S, where the thermocline significantly deepens. This Rossby wave propagates westward and accompanies significant subsurface warming along the thermocline. The Rossby wave arrives at the western Indian Ocean in the late summer, significantly warming the region to the west of 55°E at a depth of 60-100 m. This warming remains significant through October. Correspondingly, the upper ocean heat content significantly increases by approximately 2-3 × 108 J m-2 in the region west of 60°E between 5° and 10°S. The role of these oceanic dynamics in linking the winter AO, and anomalous subsurface warming was tested by numerical experiments with an oceanic general circulation model. The experiments were performed with the forcing of AO-related wind stress anomalies over the Indian Ocean in the winter. The oceanic Rossby wave generated in the central Indian Ocean during boreal winter, the consequent subsurface warming, and the anomalous upper ocean heat content in October over the

  1. Assessment of IRI and IRI-Plas models over the African equatorial and low-latitude region

    Science.gov (United States)

    Adebiyi, S. J.; Adimula, I. A.; Oladipo, O. A.; Joshua, B. W.

    2016-07-01

    A reliable ionospheric specification by empirical models is important to mitigate the effects of the ionosphere on the operations of satellite-based positioning and navigation systems. This study evaluates the capability of the International Reference Ionosphere (IRI) and IRI extended to the plasmasphere (IRI-Plas) models in predicting the total electron content (TEC) over stations located in the southern hemisphere of the African equatorial and low-latitude region. TEC derived from Global Positioning System (GPS) measurements were compared with TEC predicted by both the IRI-Plas 2015 model and the three topside options of the IRI 2012 model (i.e., NeQuick (NeQ), IRI 2001 corrected factor (IRI-01 Corr), and the IRI 2001(IRI-01)). Generally, the diurnal and the seasonal structures of modeled TEC follow quite well with the observed TEC in all the stations, although with some upward and downward offsets observed during the daytime and nighttime. The prediction errors of both models exhibit latitudinal variation and these showed seasonal trends. The values generally decrease with increase in latitude. The TEC data-model divergence of both models is most significant at stations in the equatorial region during the daytime and nighttime. Conversely, both models demonstrate most pronounced convergence during the nighttime at stations outside the equatorial region. The IRI-Plas model, in general, performed better in months and seasons when the three options of the IRI model underestimate TEC. Factors such as the height limitation of the IRI model, the inaccurate predictions of the bottomside and topside electron density profiles were used to explain the data-model discrepancies.

  2. Stratospheric variability of wave activity and parameters in equatorial coastal and tropical sites during the West African monsoon

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    Kafando, P.; Chane-Ming, F.; Petitdidier, M.

    2016-12-01

    Recent numerical studies in stratospheric dynamics and its variability as well as climate, have highlighted the need of more observational analyses to improve simulation of the West African monsoon (WAM). In this paper, activity and spectral characteristics of short-scale vertical waves (wavelengths tropical lower stratosphere during the WAM. A first detailed description of such waves over West Africa is derived from high-resolution vertical profiles of temperature and horizontal wind obtained during Intensive Observation Period of the African Monsoon Multidisciplinary Analyses (AMMA) Campaign 2006. Monthly variation of wave energy density is revealed to trace the progression of the inter-tropical convergence zone (ITCZ) over West Africa. Mesoscale inertia gravity-waves structures with vertical and horizontal wavelengths of 1.5-2.5 and 400-1100 km respectively and intrinsic frequencies of 1.1-2.2 f or periods tropical LS with intense activity during July and August when the WAM is installed over the tropical West Africa. Over equatorial region, gravity waves with intrinsic frequencies of 1.4-4 f or periods tropical stations.

  3. Assessing the distribution of monthly mean hourly solar irradiation at an African Equatorial site

    Energy Technology Data Exchange (ETDEWEB)

    Mubiru, J.; Banda, E.J.K.B.; D' Ujanga, F.; Senyonga, T. [Department of Physics, Makerere University, P.O. Box 7062, Kampala (Uganda)

    2007-02-15

    Existing literature lacks information on the distribution of total solar radiation and its components for locations within the Equatorial region. Locations in this region have substantial amounts of the solar energy resource. Distributions of solar radiation can provide a convenient format for reading solar radiation data. This data is required by modelers of solar energy applications. The objective of this study is to draw and assess the distributions of the monthly means of hourly total, diffuse and direct solar irradiation at a selected site in the Equatorial region. A location at latitude 02 17'N, longitude 32 56'E and altitude 1189 m, was selected for this study. The results have shown the distribution of global solar irradiation to have the highest peak of 4.0 MJ/m{sup 2} in December and peaks of 3.0 MJ/m{sup 2} throughout the year. A four peaked diffuse solar irradiation distribution was evident where the highest diffuse peak of 1.8 MJ/m{sup 2} was observed in September. The distribution of the direct solar irradiation exhibited peaks of 2.0 MJ/m{sup 2} during the first and last quarters of the year. (author)

  4. Magnetic storm effect on the occurrence of ionospheric irregularities at an equatorial station in the African sector

    Directory of Open Access Journals (Sweden)

    Olushola Abel Oladipo

    2014-01-01

    Full Text Available Large-scale ionospheric irregularities usually measured by GPS TEC fluctuation indices are regular occurrence at the equatorial region shortly after sunset around solar maximum. Magnetic storm can trigger or inhibit the generation of these irregularities depending on the local time the main phase of a particular storm occurs. We studied the effect of nine (9 distinct storms on the occurrence of ionospheric irregularities at Fraceville in Gabon (Lat = −1.63˚, Long = 13.55˚, dip lat. = −15.94˚, an equatorial station in the African sector. These storms occurred between November 2001 and September 2002. We used TEC fluctuation indices (i.e. ROTI and ROTIAVE estimated from 30 s interval Rinex data and also we used the storm indices (i.e. Dst, dDst/dt, and IMF BZ to predict the likely effect of each storm on the irregularities occurrence at this station. The results obtained showed that most of the storms studied inhibited ionospheric irregularities. Only one out of all the storms studied (i.e. September 4, 2002 storms with the main phase on the night of September 7-8 triggered post-midnight ionospheric irregularities. There are two of the storms during which ionospheric irregularities were observed. However, these may not be solely attributed to the storms event because the level of irregularities observed during these two storms is comparable to that observed during previous days before the storms. For this station and for the storms investigated, it seems like a little modification to the use of Aarons categories in terms of the local time the maximum negative Dst occurs could lead to a better prediction. However, it would require investigating many storms during different level of solar activities and at different latitudes to generalize this modification.

  5. Phylogeography of the genus Podococcus (Palmae/Arecaceae) in Central African rain forests: Climate stability predicts unique genetic diversity.

    Science.gov (United States)

    Faye, A; Deblauwe, V; Mariac, C; Richard, D; Sonké, B; Vigouroux, Y; Couvreur, T L P

    2016-12-01

    The tropical rain forests of Central Africa contain high levels of species diversity. Paleovegetation or biodiversity patterns suggested successive contraction/expansion phases on this rain forest cover during the last glacial maximum (LGM). Consequently, the hypothesis of the existence of refugia e.g. habitat stability that harbored populations during adverse climatic periods has been proposed. Understory species are tightly associated to forest cover and consequently are ideal markers of forest dynamics. Here, we used two central African rain forest understory species of the palm genus, Podococcus, to assess the role of past climate variation on their distribution and genetic diversity. Species distribution modeling in the present and at the LGM was used to estimate areas of climatic stability. Genetic diversity and phylogeography were estimated by sequencing near complete plastomes for over 120 individuals. Areas of climatic stability were mainly located in mountainous areas like the Monts de Cristal and Monts Doudou in Gabon, but also lowland coastal forests in southeast Cameroon and northeast Gabon. Genetic diversity analyses shows a clear North-South structure of genetic diversity within one species. This divide was estimated to have originated some 500,000years ago. We show that, in Central Africa, high and unique genetic diversity is strongly correlated with inferred areas of climatic stability since the LGM. Our results further highlight the importance of coastal lowland rain forests in Central Africa as harboring not only high species diversity but also important high levels of unique genetic diversity. In the context of strong human pressure on coastal land use and destruction, such unique diversity hotspots need to be considered in future conservation planning.

  6. GPS and GIS Methods in an African Rain Forest: Applications to Tropical Ecology and Conservation

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    Brean Duncan

    2002-01-01

    Full Text Available Since the completion of the Navstar Global Positioning System (GPS in 1995, the integration of GPS and Geographical Information Systems (GIS technology has expanded to a great number of ecological and conservation applications. In tropical rain forest ecology, however, the technology has remained relatively neglected, despite its great potential. Notwithstanding cost, this is principally due to (1 the difficulty of quality satellite reception beneath a dense forest canopy, and (2 a degree of spatial error unacceptable to fine-scale vegetation mapping. Here, we report on the technical use of GPS/GIS in the rain forest of Kibale National Park, Uganda, and the methodology necessary to acquire high-accuracy spatial measurements. We conclude that the stringent operating parameters necessary for high accuracy were rarely obtained while standing beneath the rain forest canopy. Raising the GPS antenna to heights of 25–30 m resolved this problem, allowing swift data collection on the spatial dispersion of individual rain forest trees. We discuss the impact of the 1996 Presidential Decision Directive that suspended U.S. military-induced GPS error on 1 May 2000, and comment on the potential applications of GPS/GIS technology to the ecological study and conservation of tropical rain forests.

  7. Nighttime ionospheric saturation effect estimation in the African equatorial anomaly trough: A comparison of two approaches

    Science.gov (United States)

    Ikubanni, Stephen O.; Adeniyi, Jacob O.

    2016-02-01

    Using the two-segmented and the quadratic regression analyses methods, the existence of saturation effect in the ionospheric electron content has been established in published literatures. With data set that spans an 11 year period (one solar cycle) from an African low-latitude station—Ouagadougou, Burkina Faso (Geographical coordinates 12oN, 1.8oW, dip ~3oN)—and adopting the quadratic and the two-segmented regression methods, we have studied nighttime saturation effect on the critical frequency of ionospheric F2 layer (foF2) around the magnetic dip. Both methods revealed that saturation effect in foF2 cuts across all seasons during nighttime. This phenomenon was least at the peak of the prereversal enhancement (PRE) period and increases significantly beyond midnight. Either of the two approaches can be adopted for saturation effect studies. The advantage of the two-segmented over the quadratic is that the change point (breakpoint), which is the solar flux level where saturation effects first become observable, can be determined. The effect seen around the PRE period may be attributed to the E × B drift while the effect beyond the PRE period is masked by other mechanisms.

  8. West African equatorial ionospheric parameters climatology based on Ouagadougou ionosonde station data from June 1966 to February 1998

    Directory of Open Access Journals (Sweden)

    F. Ouattara

    2009-06-01

    Full Text Available This study is the first which gives the climatology of West African equatorial ionosphere by using Ouagadougou station through three solar cycles. It has permitted to show the complete morphology of ionosphere parameters by analyzing yearly variation, solar cycle and geomagnetic activity, seasonal evolution and diurnal development. This work shows that almost all ionospheric parameters have 11-year solar cycle evolution. Seasonal variation shows that only foF2 exhibits annual, winter and semiannual anomaly. foF2 seasonal variation has permitted us to identify and characterize solar events effects on F2 layer in this area. In fact (1 during quiet geomagnetic condition foF2 presents winter and semiannual anomalies asymmetric peaks in March/April and October. (2 The absence of winter anomaly and the presence of equinoctial peaks are the most visible effects of fluctuating activity in foF2 seasonal time profiles. (3 Solar wind shock activity does not modify the profile of foF2 but increases ionization. (4 The absence of asymmetry peaks, the location of the peaks in March and October and the increase of ionization characterize recurrent storm activity. F1 layers shows increasing trend from cycle 20 to cycle 21. Moreover, E layer parameters seasonal variations exhibit complex structure. It seems impossible to detect fluctuating activity effect in E layer parameters seasonal variations but shock activity and wind stream activity act to decrease E layer ionization. It can be seen from Es layer parameters seasonal variations that wind stream activity effect is fairly independent of solar cycle. E and Es layers critical frequencies and virtual heights diurnal variations let us see the effects of the greenhouse gases in these layers.

  9. Study of zonal large scale wave structure (LSWS) and equatorial scintillation with low-latitude GRBR network over Southeast Asia and African sectors

    Science.gov (United States)

    Ram Sudarsanam, Tulasi; Yamamoto, Mamoru; Gurubaran, Subramanian; Tsunoda, Roland

    2012-07-01

    The day-to-day variability of Equatorial Spread-F, when and where the equatorial plasma bubbles (EPBs) may initiate, were the challenging problems that puzzling the space weather researchers for several decades. The zonal large scale wave structure (LSWS) at the base of F-layer is the earliest manifestation of seed perturbation for the evolution of EPBs by R-T instability processes, hence, found to play deterministic role on the development of ESF. Yet, only a little is known about LSWS with lack of sufficient observations, primarily because of inability to detect the LSWS with the currently existing instruments except with steerable incoherent scatter radar such as ALTAIR radar. This situation, however, was recently changed with launch of C/NOFS in a unique low-inclination (13 ^{o}) orbit. With the availability of CERTO beacon transmissions from C/NOFS in a near equatorial orbit, it is now possible to detect and resolve the roles by LSWS on a regular basis. A ground based low-latitude GNU Radio Beacon Receiver (GRBR) Network has been recently established that provide coverage of Southeast Asia, Pacific and African low-latitude regions. Recent observations suggest that these wave structures with zonal wave lengths varying between 200 and 800 km can be earliest detected even before E-region sunset and found to grow significantly after sunset, probably, aided by the polarization electric fields. Further, these zonal structures consistently found to be aligned with field lines for several hundreds of kilometers and EPBs were found to grow from the westward walls of upwellings. The characteristic differences on the strength of LSWS between the Asian and African longitudes were identified during the recent increasing solar activity and discussed in this paper.

  10. Duffy negative antigen is no longer a barrier to Plasmodium vivax--molecular evidences from the African West Coast (Angola and Equatorial Guinea.

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    Cristina Mendes

    2011-06-01

    Full Text Available BACKGROUND: Plasmodium vivax shows a small prevalence in West and Central Africa due to the high prevalence of Duffy negative people. However, Duffy negative individuals infected with P. vivax have been reported in areas of high prevalence of Duffy positive people who may serve as supply of P. vivax strains able to invade Duffy negative erythrocytes. We investigated the presence of P. vivax in two West African countries, using blood samples and mosquitoes collected during two on-going studies. METHODOLOGY/FINDINGS: Blood samples from a total of 995 individuals were collected in seven villages in Angola and Equatorial Guinea, and 820 Anopheles mosquitoes were collected in Equatorial Guinea. Identification of the Plasmodium species was achieved by nested PCR amplification of the small-subunit rRNA genes; P. vivax was further characterized by csp gene analysis. Positive P. vivax-human isolates were genotyped for the Duffy blood group through the analysis of the DARC gene. Fifteen Duffy-negative individuals, 8 from Equatorial Guinea (out of 97 and 7 from Angola (out of 898, were infected with two different strains of P. vivax (VK210 and VK247. CONCLUSIONS: In this study we demonstrated that P. vivax infections were found both in humans and mosquitoes, which means that active transmission is occurring. Given the high prevalence of infection in mosquitoes, we may speculate that this hypnozoite-forming species at liver may not be detected by the peripheral blood samples analysis. Also, this is the first report of Duffy negative individuals infected with two different strains of P. vivax (VK247 and classic strains in Angola and Equatorial Guinea. This finding reinforces the idea that this parasite is able to use receptors other than Duffy to invade erythrocytes, which may have an enormous impact in P. vivax current distribution.

  11. The odd man out? Might climate explain the lower tree alpha-diversity of African rain forests relative to Amazonian rain forests?

    NARCIS (Netherlands)

    Parmentier, I.; Malhi, Y.; Senterre, B.; Whittaker, R.J.; Alonso, A.; Balinga, M.P.B.; Bakayoko, A.; Bongers, F.J.J.M.; Chatelain, C.; Comiskey, J.; Cortay, R.; Djuikouo Kamdem, M.N.; Doucet, J.L.; Gauier, L.; Hawthorne, W.D.; Issembe, Y.A.; Kouamé, F.N.; Kouka, L.; Leal, M.E.; Lejoly, J.; Lewis, S.L.; Newbery, D.; Nusbaumer, L.; Parren, M.P.E.; Peh, K.S.H.; Phillips, O.L.; Sheil, D.; Sonké, B.; Sosef, M.S.M.; Sunderland, T.; Stropp, J.; Steege, ter H.; Swaine, M.; Tchouto, P.; Gemerden, van B.S.; Valkenburg, van J.; Wöll, H.

    2007-01-01

    1. Comparative analyses of diversity variation among and between regions allow testing of alternative explanatory models and ideas. Here, we explore the relationships between the tree alpha-diversity of small rain forest plots in Africa and in Amazonia and climatic variables, to test the explanatory

  12. Effects of the intense geomagnetic storm of September-October 2012 on the equatorial, low- and mid-latitude F region in the American and African sector during the unusual 24th solar cycle

    Science.gov (United States)

    de Jesus, R.; Fagundes, P. R.; Coster, A.; Bolaji, O. S.; Sobral, J. H. A.; Batista, I. S.; de Abreu, A. J.; Venkatesh, K.; Gende, M.; Abalde, J. R.; Sumod, S. G.

    2016-02-01

    The main purpose of this paper is to investigate the response of the ionospheric F layer in the American and African sectors during the intense geomagnetic storm which occurred on 30 September-01 October 2012. In this work, we used observations from a chain of 20 GPS stations in the equatorial, low- and mid-latitude regions in the American and African sectors. Also, in this study ionospheric sounding data obtained during 29th September to 2nd October, 2012 at Jicamarca (JIC), Peru, São Luis (SL), Fortaleza (FZ), Brazil, and Port Stanley (PST), are presented. On the night of 30 September-01 October, in the main and recovery phase, the h´F variations showed an unusual uplifting of the F region at equatorial (JIC, SL and FZ) and mid- (PST) latitude stations related with the propagations of traveling ionospheric disturbances (TIDs) generated by Joule heating at auroral regions. On 30 September, the VTEC variations and foF2 observations at mid-latitude stations (American sector) showed a long-duration positive ionospheric storm (over 6 h of enhancement) associated with large-scale wind circulations and equatorward neutral winds. Also, on 01 October, a long-duration positive ionospheric storm was observed at equatorial, low- and mid- latitude stations in the African sector, related with the large-scale wind circulations and equatorward neutral winds. On 01 and 02 October, positive ionospheric storms were observed at equatorial, low- and mid-latitude stations in the American sector, possibly associated with the TIDs and an equatorward neutral wind. Also, on 01 October negative ionospheric storms were observed at equatorial, low- and mid-latitude regions in the American sector, probably associated with the changes in the O/N2 ratio. On the night of 30 September-01 October, ionospheric plasma bubbles were observed at equatorial, low- and mid- latitude stations in the South American sector, possibly associated with the occurrence of geomagnetic storm.

  13. Size variation in Tachyoryctes splendens (East African mole-rat) and its implications for late Quaternary temperature change in equatorial East Africa

    Science.gov (United States)

    Faith, J. Tyler; Patterson, David B.; Blegen, Nick; O'Neill, Chris J.; Marean, Curtis W.; Peppe, Daniel J.; Tryon, Christian A.

    2016-05-01

    This study develops a new proxy for Quaternary temperature change in tropical Africa through analysis of size variation in East African mole-rat (Tachyoryctes splendens). In modern mole-rats, mandibular alveolar length is unrelated to annual precipitation, precipitation seasonality, temperature seasonality, or primary productivity. However, it is inversely correlated with mean annual temperature, in agreement with Bergmann's rule. This relationship is observed at temperatures below ˜17.3 °C, but not at higher temperatures. We apply these observations to late Quaternary mole-rats from Wakondo (˜100 ka) and Kisaaka (˜50 ka) in the Lake Victoria region and Enkapune ya Muto (EYM; ˜7.2-3.2 ka) in Kenya's central rift. The Lake Victoria mole-rats are larger than expected for populations from warm climates typical of the area today, implying cooler temperatures in the past. The magnitude of temperature decline needed to drive the size shift is substantial (˜4-6 °C), similar in magnitude to the degree of change between the Last Glacial Maximum and Holocene, but is consistent with regional temperature records and with scenarios linking equatorial African temperature to northern hemisphere summer insolation. Size changes through time at EYM indicate that rising temperatures during the middle Holocene accompanied and potentially contributed to a decline in Lake Naivasha and expansion of grassland vegetation.

  14. Characterisation of GPS-TEC in the African equatorial and low latitude region and the regional evaluation of the IRI model

    Science.gov (United States)

    Adebiyi, S. J.; Adimula, I. A.; Oladipo, O. A.

    2016-06-01

    With the increasing application of Global Navigation Satellite System (GNSS) products and services, knowledge of the Total Electron Content (TEC) variation is vital, particularly in historically under-sampled regions. The ionospheric induced-error, which is the largest and most variable error source of GNSS applications, is proportional to TEC along the satellite-receiver path. Simultaneous Global Positioning System (GPS) measurements from six African equatorial and low latitude stations in the southern hemisphere are used to investigate the latitudinal variation of TEC over the region during the year 2013, a year of moderate solar activity. The analysis reveals some detailed features of seasonal, month-to-month and solar activity dependence of TEC. The seasonal variation of TEC revealed that the daytime and the pre-midnight values of TEC for stations located close to the geographic equator is considerably higher in equinoxes and June solstice compared to stations farther from the equator, however, the difference is insignificant during the December solstice. The month-to-month variation of TEC shows semi-annual symmetry/asymmetry in TEC values for stations closer/farther from the equator. TEC sensitivity to solar activity shows significant seasonal and latitudinal characteristics. Generally, a relatively good correlation exists between TEC and F10.7 for stations around the Equatorial Ionization Anomaly (EIA) region compared to those found at stations close to the equator. Beyond the EIA region, the correlation coefficients drop in all seasons. TEC predicted by the three topside options of the International Reference Ionosphere (IRI) 2012 model [i.e. the NeQuick (NeQ), IRI-2001 Corrected (IRI-01 Corr) and the IRI-2001 (IRI-01) options] exhibits latitudinal and seasonal characteristics. The NeQ option performed better than the other two options at stations located within the equatorial region in most of the months and seasons. Outside the EIA region, the IRI-01 Corr

  15. Molecular Evidence of a Trypanosoma brucei gambiense Sylvatic Cycle in the Human African Trypanosomiasis Foci of Equatorial Guinea

    Directory of Open Access Journals (Sweden)

    Carlos eCordon-Obras

    2015-07-01

    Full Text Available Gambiense trypanosomiasis is considered an anthroponotic disease. Consequently, control programs are generally aimed at stopping transmission of Trypanosoma brucei gambiense (T. b. gambiense by detecting and treating human cases. However, the persistence of numerous foci despite efforts to eliminate this disease questions this strategy as unique tool to pursue the eradication. The role of animals as a reservoir of T. b. gambiense is still controversial, but could partly explain maintenance of the infection at hypo-endemic levels. In the present study, we evaluated the presence of T. b. gambiense in wild animals in Equatorial Guinea. The infection rate ranged from 0.8% in the insular focus of Luba to more than 12% in Mbini, a focus with a constant trickle of human cases. The parasite was detected in a wide range of animal species including four species never described previously as putative reservoirs. Our study comes to reinforce the hypothesis that animals may play a role in the persistence of T. b. gambiense transmission, being particularly relevant in low transmission settings. Under these conditions the integration of sustained vector control and medical interventions should be considered to achieve the elimination of Gambiense trypanosomiasis.

  16. The influence of biomass burning and transport on tropospheric composition over the tropical Atlantic Ocean and Equatorial Africa during the West African monsoon in 2006

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    J. E. Williams

    2010-10-01

    Full Text Available Biomass burning (BB in southern Africa is the largest emission source of CO and O3 precursors within Africa during the West African Monsoon (WAM between June and August. The long range transport and chemical processing of such emissions thus has the potential to exert a dominant influence on the composition of the tropical troposphere over Equatorial Africa (EA and the Tropical Atlantic Ocean (TAO. We have performed simulations using a three-dimensional global chemistry-transport model (CTM to quantify the effect that continental transport of such BB plumes has on the EA region. BB emissions from southern Africa were found to exert a significant influence over the TAO and EA between 10° S–20° N. The maximum concentrations in CO and O3 occur between 0–5° S near the position of the African Easterly Jet – South as placed by the European Centre for Medium range Weather Forecasts (ECMWF meteorological analysis data. By comparing co-located model output with in-situ measurements we show that the CTM fails to capture the tropospheric profile of CO in southern Africa near the main source region of the BB emissions, as well as the "extreme" concentrations of both CO and O3 seen between 600–700 hPa over EA around 6° N. For more northerly locations the model exhibits high background concentrations in both CO and O3 related to BB emissions from southern Africa. By altering both the temporal resolution and the vertical distribution of BB emissions in the model we show that changes in temporal resolution have the largest influence on the transport of trace gases near the source regions, EA, and in the outflow towards the west of Central Africa. Using a set of trajectory calculations we show that the performance of the CTM is heavily constrained by the ECMWF meteorological fields used to drive the CTM, which transport biomass burning plumes from southern Africa into the lower troposphere of the TAO rather

  17. The Development of Chinese Companies in African Construction Market:A Case of Equatorial Guinea%中国公司在非洲建筑市场的发展:赤道几内亚案例

    Institute of Scientific and Technical Information of China (English)

    龚财君

    2013-01-01

      在中国的“走出去”战略要求下,中国公司大量进入非洲建筑市场。以赤道几内亚为例,本文描述了中国公司在赤道几内亚承接的项目情况、经营情况、成功原因以及存在的问题。%A large number of Chinese companies enter the African construction market based on the requirements for China's "Going Global" strategy. Taking Equatorial Guinea for example, the problems, reasons for the success, operating conditions and projects situation which is undertook by Chinese companies in Equatorial Guinea were described in this article.

  18. Coupled marine productivity and salinity and West African monsoon variability over the last 30,000 years in the eastern equatorial Atlantic Ocean

    Science.gov (United States)

    Marret, F.; Kim, S.-Y.; Scourse, J.; Kennedy, H.

    2009-04-01

    Marine cores collected off west equatorial Africa have highlighted transfer of terrigenous material in the close ocean that have had a deep influence on the marine productivity for the last 30,000 years. The strength of the West African Monsoon has varied though time, from weak during glacial periods to strong during interglacials. In consequence, the amount of precipitation on the continent had drastic effect on the vegetation cover and soil erosion. Studies of marine cores have enabled the observation of changes in vegetation cover, from extended equatorial rainforest to expansion of savannahs. In association with open grassland association, soil is open to erosion, although precipitation is less; conversely, during periods of extended rainforest in a context of strong monsoon, soil erosion is minimised to the presence of trees. In both cases, terrigenous material is flushed out to the adjacent marine domain and has a profound influence on the marine biota. Three marine cores were studied from a north south transect, from Cameroon to Angola (off Sanaga, off Ogouée, and off Congo rivers), for their palynomorph contents. All cores contain a robust chronology based on radiocarbon dates and two have stable isotope data, allowing comparison. Dinoflagellate cysts were studied for retracing sea-surface conditions such as temperature, salinity and productivity whereas pollen were used to assess changes in the vegetation on the close continent for the last 30,000 years (1). A number of pollen records from terrestrial sequences from equatorial central Africa document the dynamics of the lowland rainforest and savannah in relation to climatic changes during the Holocene. Prior to the Holocene, continental records are scarce in this vast region and/or only allow reconstruction of the local vegetation. In our records, terrestrial proxies (pollen, spores, and charred grass cuticles) signal changes in the expansion/regression of the lowland rainforest which we relate to the

  19. Equatorial Guinea.

    Science.gov (United States)

    1984-06-01

    Attention in this discussion of Equatorial Guinea is directed to the following: the people, history, geography, government, political conditions, the economy, foreign relations, and relations between the US and Equatorial Guinea. The population was estimated at 304,000 in 1983 and the annual growth rate was estimated in the range of 1.7-2.5. The infant mortality rate is 142.9/1000 with a life expectancy of 44.4 years for males and 47.6 years for females. The majority of the Equatoguinean people are of Bantu origin. The largest tribe, the Fang, is indigenous to the mainland, although many now also live on Bioko Island. Portuguese explorers found the island of Bioko in 1471, and the Portuguese retained control until 1778, when the island, adjacent islets, and the commercial rights to the mainland between the Niger and Ogooue Rivers were ceded to Spain. Spain lacked the wealth and the interest to develop an extensive economic infrastructure in Equatorial Guinea during the 1st half of this century, but the Spanish did help Equatorial Guinea achieve 1 of the highest literacy rates in Africa. They also founded a good network of health care facilities. In March 1968, under pressure from Guinean nationalists, Spain announced that it would grant independence to Equatorial Guinea as rapidly as possible. A referendum was held on August 11, 1968, and 63% of the electorate voted in favor of the constitution, which provided for a government with a general assembly and presidentially appointed judges in the Supreme Court. After the coup in August 1979, power was placed in the hands of a Supreme Military Council. A new constitution came into effect after a popular vote in August 1982, abolishing the Supreme Military Council. Under the terms of the constitution, the president was given extensive powers. By the end of 1983, a 60-member Chamber of Representatives of the people had been formed. The government, which is credited with restoring greater personal freedom, is regarded

  20. The effect of subtropical aerosol loading on equatorial precipitation

    Science.gov (United States)

    Dagan, G.; Chemke, R.

    2016-10-01

    Cloud-aerosol interactions are considered as one of the largest sources of uncertainties in the study of climate change. Here another possible cloud-aerosol effect on climate is proposed. A series of large eddy simulations (LES) with bin microphysics reveal a sensitivity of the total atmospheric water vapor amount to aerosol concentration. Under polluted conditions the rain is suppressed and the total amount of water vapor in the atmosphere increases with time compared to clean precipitating conditions. Theoretical examination of this aerosol effect on water vapor transport from the subtropics to the tropics, and hence on the equatorial rain and Hadley circulation, is conducted using an idealized general circulation model (GCM). It is shown that a reduction in the subtropical rain amount results in increased water vapor advection to the tropics and enhanced equatorial rain and Hadley circulation. This joins previously proposed mechanisms on the radiative aerosol effect on the general circulation.

  1. Aerosol Transport Over Equatorial Africa

    Science.gov (United States)

    Gatebe, C. K.; Tyson, P. D.; Annegarn, H. J.; Kinyua, A. M.; Piketh, S.; King, M.; Helas, G.

    1999-01-01

    Long-range and inter-hemispheric transport of atmospheric aerosols over equatorial Africa has received little attention so far. Most aerosol studies in the region have focussed on emissions from rain forest and savanna (both natural and biomass burning) and were carried out in the framework of programs such as DECAFE (Dynamique et Chimie Atmospherique en Foret Equatoriale) and FOS (Fires of Savanna). Considering the importance of this topic, aerosols samples were measured in different seasons at 4420 meters on Mt Kenya and on the equator. The study is based on continuous aerosol sampling on a two stage (fine and coarse) streaker sampler and elemental analysis by Particle Induced X-ray Emission. Continuous samples were collected for two seasons coinciding with late austral winter and early austral spring of 1997 and austral summer of 1998. Source area identification is by trajectory analysis and sources types by statistical techniques. Major meridional transports of material are observed with fine-fraction silicon (31 to 68 %) in aeolian dust and anthropogenic sulfur (9 to 18 %) being the major constituents of the total aerosol loading for the two seasons. Marine aerosol chlorine (4 to 6 %), potassium (3 to 5 %) and iron (1 to 2 %) make up the important components of the total material transport over Kenya. Minimum sulfur fluxes are associated with recirculation of sulfur-free air over equatorial Africa, while maximum sulfur concentrations are observed following passage over the industrial heartland of South Africa or transport over the Zambian/Congo Copperbelt. Chlorine is advected from the ocean and is accompanied by aeolian dust recirculating back to land from mid-oceanic regions. Biomass burning products are transported from the horn of Africa. Mineral dust from the Sahara is transported towards the Far East and then transported back within equatorial easterlies to Mt Kenya. This was observed during austral summer and coincided with the dying phase of 1997/98 El

  2. Acid Rain

    Science.gov (United States)

    Bricker, Owen P.; Rice, Karen C.; Dietrich, W.E.; Sposito, Garrison

    1997-01-01

    Acid deposition, or acid rain as it is more commonly referred to, has become a widely publicized environmental issue in the U.S. over the past decade. The term usually conjures up images of fish kills, dying forests, "dead" lakes, and damage to monuments and other historic artifacts. The primary cause of acid deposition is emission of S02 and NOx to the atmosphere during the combustion of fossil fuels. Oxidation of these compounds in the atmosphere forms strong acids - H2SO4 and HNO3 - which are returned to the Earth in rain, snow, fog, cloud water, and as dry deposition.Although acid deposition has only recently been recognized as an environmental problem in the U.S., it is not a new phenomenon (Cogbill & Likens 1974). As early as the middle of the 17th century in England, the deleterious effects of industrial emissions on plants, animals, and humans, and the atmospheric transport of pollutants between England and France had become issues of concern (Evelyn 1661, Graunt 1662). It is interesting that well over three hundred years ago in England, recommendations were made to move industry outside of towns and build higher chimneys to spread the pollution into "distant parts." Increasing the height of smokestacks has helped alleviate local problems, but has exacerbated others. In the U.S. the height of the tallest smokestack has more than doubled, and the average height of smokestacks has tripled since the 1950s (Patrick et al 1981). This trend occurred in most industrialized nations during the 20th century and has had the effect of transforming acid rain from a local urban problem into a problem of global scale.

  3. Distribution of tetraether lipids in the 25-ka sedimentary record of Lake Challa: extracting reliable TEX86 and MBT/CBT palaeotemperatures from an equatorial African lake

    Science.gov (United States)

    Sinninghe Damsté, Jaap S.; Ossebaar, Jort; Schouten, Stefan; Verschuren, Dirk

    2012-09-01

    The distribution of isoprenoid and branched glycerol dialkyl glycerol tetraether (GDGT) lipids was studied in the sedimentary record of Lake Challa, a permanently stratified, partly anoxic crater lake on the southeastern slope of Mt. Kilimanjaro (Kenya/Tanzania), to examine if the GDGTs could be used to reconstruct past variation in regional temperature. The study material comprised 230 samples from a continuous sediment sequence spanning the last 25 ka with excellent age control based on high-resolution AMS 14C dating. The distribution of GDGTs showed large variation through time. In some time intervals (i.e., from 20.4 to 15.9 ka BP and during the Younger Dryas, 12.9-11.7 ka BP) crenarchaeol was the most abundant GDGT, whereas at other times (i.e., during the Early Holocene) branched GDGTs and GDGT-0 were the major GDGT constituents. In some intervals of the sequence the relative abundance of GDGT-0 and GDGT-2 was too high to be derived exclusively from lacustrine Thaumarchaeota, suggesting a sizable contribution from methanogens and other archaea. This severely complicated application of TEX86 palaeothermometry in this lake, and limited reliable reconstruction of lake water temperature to the time interval 25-13 ka BP, i.e. the Last Glacial Maximum and the period of post-glacial warming. The TEX86-inferred timing of this warming is similar to that recorded previously in two of the large African rift lakes, while its magnitude is slightly or much higher than that recorded at these other sites, depending on which lake-based TEX86 calibration is used. Application of calibration models based on distributions of branched GDGTs developed for lakes inferred temperatures of 15-18 °C for the Last Glacial Maximum and 19-22 °C for the Holocene. However, the MBT/CBT palaeothermometer reconstructs temperatures as low as 12 °C for a Lateglacial period centred on 15 ka BP. Variation in down-core values of the BIT index are mainly determined by the varying production rate of

  4. Rain Barrels in Utah

    OpenAIRE

    Greene, Brian; Mesner, Nancy; Brain, Roslynn

    2015-01-01

    Rain barrels are an easy way to conserve rain water and help protect our environment. This fact sheet tells how to find out about the current regulations in Utah and how to build a rain barrel for your own home.

  5. Intermonsoonal equatorial jets

    Digital Repository Service at National Institute of Oceanography (India)

    Muraleedharan, P.M.

    , respectively. Hydrographic features and transport computations favour a well developed equatorial jet during both seasons. The net surface eastward and subsurface westward flows are well balanced during the premonsoon transition period and appear...

  6. A Colorful Equatorial Wonderland

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ Papua New Guinea (PNG) is one of the least visited countries in the world... a last frontier for international travelers. PNG is a colorful equatorial wonderland as well as a living example of human's culture 1000 years ago.

  7. Re-imaging the Modernity of Sierra Leone and Equatorial Guinea: Africa past and Africa present

    OpenAIRE

    Codling, Rosetta

    2011-01-01

    This paper engages the concept of the imposed Modernity of Europe upon the African republics of Sierra Leone and Equatorial Guinea. Evidence of the encroachment of a ‘false’ Modernity upon Africa’s Sierra Leone and Equatorial Guinea are chronicled in the works of Donato Ndongo (Shadows of Your Black Memory) and Syl Cheney Coker (The Last Harmattan of Alusine Dunbar).

  8. Earth-To-Space Improved Model for Rain Attenuation Prediction at Ku-Band

    Directory of Open Access Journals (Sweden)

    Mandeep S.J. Singh

    2006-01-01

    Full Text Available A model for predicting rain attenuation on earth-to-space was developed by using the measurement data obtained from tropical and equatorial region. The proposed rain attenuation model uses the complete rainfall rate cumulative distribution as input data. It was shown that significant improvements in terms of prediction error over existing attenuation model obtained.

  9. Rain Gauges Handbook

    Energy Technology Data Exchange (ETDEWEB)

    Bartholomew, M. J. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2016-01-01

    To improve the quantitative description of precipitation processes in climate models, the Atmospheric Radiation Measurement (ARM) Climate Research Facility deployed rain gauges located near disdrometers (DISD and VDIS data streams). This handbook deals specifically with the rain gauges that make the observations for the RAIN data stream. Other precipitation observations are made by the surface meteorology instrument suite (i.e., MET data stream).

  10. Acid Rain Study Guide.

    Science.gov (United States)

    Hunger, Carolyn; And Others

    Acid rain is a complex, worldwide environmental problem. This study guide is intended to aid teachers of grades 4-12 to help their students understand what acid rain is, why it is a problem, and what possible solutions exist. The document contains specific sections on: (1) the various terms used in conjunction with acid rain (such as acid…

  11. The Acid Rain Reader.

    Science.gov (United States)

    Stubbs, Harriett S.; And Others

    A topic which is often not sufficiently dealt with in elementary school textbooks is acid rain. This student text is designed to supplement classroom materials on the topic. Discussed are: (1) "Rain"; (2) "Water Cycle"; (3) "Fossil Fuels"; (4) "Air Pollution"; (5) "Superstacks"; (6) "Acid/Neutral/Bases"; (7) "pH Scale"; (8) "Acid Rain"; (9)…

  12. Seasonal trends of dry and bulk concentration of nitrogen compounds over a rain forest in Ghana

    Directory of Open Access Journals (Sweden)

    F. Fattore

    2013-09-01

    Full Text Available African tropical forests of the equatorial belt might receive significant input of extra nitrogen derived from biomass burning occurring in the north savanna belt and transported equator wards by NE winds. In order to test this hypothesis an experiment was set up in a tropical rain forest in the National park of Ankasa (Ghana aiming at: quantifying magnitude and seasonal variability of concentrations of N compounds, present as gas and aerosol (dry nitrogen or in the rainfall (bulk nitrogen, over the studied forest; relating their seasonal variability to trends of local and regional winds and rainfall and to variations of fire events in the region. Three Delta systems, implemented for monthly measurements of NO2, were mounted over a tower at 45 m height, 20 m above forest canopy to sample gas (NH3, NO2, HNO3, HCl, SO2 and aerosol (NH4+, NO3−, and several ions, together with three tanks for bulk rainfall collection (to analyze NH4+, NO3− and ion concentration. The tower was provided with a sonic anemometer to estimate local wind data. The experiment started in October 2011 and data up to October 2012 are presented. To interpret the observed seasonal trends of measured compounds, local and regional meteo data and regional satellite fire data were analyzed. The concentration of N compounds significantly increased from December to April, during the drier period, peaking in December-February when North Eastern winds (Harmattan were moving dry air masses over the West central African region and the inter tropical convergence zone (ITCZ was at its minimum latitude over the equator. This period also coincided with peaks of fire in the whole region. On the contrary, N concentration in gas, aerosol and rain decreased from May to October when prevalent winds arrived from the sea (South-East, during the Monsoon period. Both ionic compositions of rain and analysis of local wind direction showed a significant and continuous presence of see-breeze at site

  13. Understanding the Longitudinal Variability of Equatorial Electrodynamics using integrated Ground- and Space-based Observations

    Science.gov (United States)

    Yizengaw, E.; Moldwin, M.; Zesta, E.

    2015-12-01

    The currently funded African Meridian B-Field Education and Research (AMBER) magnetometer array comprises more than thirteen magnetometers stationed globally in the vicinity of geomagnetic equator. One of the main objectives of AMBER network is to understand the longitudinal variability of equatorial electrodynamics as function of local time, magnetic activity, and season. While providing complete meridian observation in the region and filling the largest land-based gap in global magnetometer coverage, the AMBER array addresses two fundamental areas of space physics: first, the processes governing electrodynamics of the equatorial ionosphere as a function of latitude (or L-shell), local time, longitude, magnetic activity, and season, and second, ULF pulsation strength at low/mid-latitude regions and its connection with equatorial electrojet and density fluctuation. The global AMBER network can also be used to augment observations from space-based instruments, such us the triplet SWARM mission and the upcoming ICON missions. Thus, in coordination with space-based and other ground-based observations, the AMBER magnetometer network provides a great opportunity to understand the electrodynamics that governs equatorial ionosphere motions. In this paper we present the longitudinal variability of the equatorial electrodynamics using the combination of instruments onboard SWARM and C/NOFS satellites and ground-based AMBER network. Both ground- and pace-based observations show stronger dayside and evening sector equatorial electrodynamics in the American and Asian sectors compared to the African sector. On the other hand, the African sector is home to stronger and year-round ionospheric bubbles/irregularities compared to the American and Asian sectors. This raises the question if the evening sector equatorial electrodynamics (vertical drift), which is believed to be the main cause for the enhancement of Rayleigh-Taylor (RT) instability growth rate, is stronger in the

  14. Identity crisis in "The Rain Child"

    Institute of Scientific and Technical Information of China (English)

    赵亭亭

    2008-01-01

    In the short story "The Rain Child" , Canadian Margaret Laurence gives a clear outline of encounters between the European culture and the African culture. This thesis analyzes the meaning of culture and cultural identity. It focuses on the different psychological states of Ruth, the heroine, under different social circumstances. It explains how her cultural identity crisis is generated. As the final analysis, fierce cultural conflicts and contradictions are caused by the misunderstanding of different cultural groups.

  15. ACTS Rain Fade Compensation

    Science.gov (United States)

    Coney, Thom A.

    1996-01-01

    Performance status of the Adaptive Rain Fade Compensation includes: (1) The rain fade protocol is functional detecting fades, providing an additional 10 dB of margin and seamless transitions to and from coded operation; (2) The stabilization of the link margins and the optimization of rain fade decision thresholds has resulted in improved BER performance; (3) Characterization of the fade compensation algorithm is ongoing.

  16. Rain Forest Murals

    Science.gov (United States)

    Kleiner, Cheryl

    2010-01-01

    The rain forest murals in the author's school began as a request from her principal to have students decorate the cafeteria with their own paintings. She decided to brainstorm ideas with her eighth-grade students. Taking into consideration the architectural space and the environmental concerns they wanted to convey, students chose the rain forest…

  17. Geologic mapping of Indonesian rain forest with analysis of multiple SIR-B incidence angles

    Science.gov (United States)

    Ford, J. P.; Sabins, F. F., Jr.; Asmoro, P., Jr.

    1984-01-01

    The discrimination and mapping capabilities are to be evaluated for shuttle imaging radar-B (SIR-B) images of geologic features in Indonesia that are covered by equatorial rain forest canopy. The SIR-B backscatter from the rain forest at L-band is to be compared to backscatter acquired by the SEASAT scatterometer system at Ku-band ever corresponding areas. The approach for data acquisition, handling, and analysis and the expected results of the investigation are discussed.

  18. RAINE Public Communities

    Data.gov (United States)

    U.S. Environmental Protection Agency — The file geodatabase (fgdb) contains the New England Town Boundaries and information related specifically to the Resilience and Adaptation in New England (RAINE) web...

  19. Acid rain: An overview

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Summary of the effects of acid rain and related processes, sources, issues, corrective actions, research, current law, potential solutions, political solutions,...

  20. The Equatorial Ekman Layer

    CERN Document Server

    Marcotte, Florence; Soward, Andrew

    2016-01-01

    The steady incompressible viscous flow in the wide gap between spheres rotating about a common axis at slightly different rates (small Ekman number E) has a long and celebrated history. The problem is relevant to the dynamics of geophysical and planetary core flows, for which, in the case of electrically conducting fluids, the possible operation of a dynamo is of considerable interest. A comprehensive asymptotic study, in the limit E<<1, was undertaken by Stewartson (J. Fluid Mech. 1966, vol. 26, pp. 131-144). The mainstream flow, exterior to the E^{1/2} Ekman layers on the inner/outer boundaries and the shear layer on the inner sphere tangent cylinder C, is geostrophic. Stewartson identified a complicated nested layer structure on C, which comprises relatively thick quasi-geostrophic E^{2/7} (inside C) and E^{1/4} (outside C) layers. They embed a thinner E^{1/3} ageostrophic shear layer (on C), which merges with the inner sphere Ekman layer to form the E^{2/5} Equatorial Ekman layer of axial length E^{...

  1. Observations of ULF wave related equatorial electrojet and density fluctuations

    Science.gov (United States)

    Yizengaw, E.; Zesta, E.; Biouele, C. M.; Moldwin, M. B.; Boudouridis, A.; Damtie, B.; Mebrahtu, A.; Anad, F.; Pfaff, R. F.; Hartinger, M.

    2013-10-01

    We report on Pc5 wave related electric field and vertical drift velocity oscillations at the equator as observed by ground magnetometers for an extended period on 9 August 2008. We show that the magnetometer-estimated equatorial E×B drift oscillates with the same frequency as ULF Pc5 waves, creating significant ionospheric density fluctuations. We also show ionospheric density fluctuations during the period when we observed ULF wave activity. At the same time, we detect the ULF activity on the ground using ground-based magnetometer data from the African Meridian B-field Education and Research (AMBER) and the South American Meridional B-field Array (SAMBA). From space, we use magnetic field observations from the GOES 12 and the Communication/Navigation Outage and Forecast System (C/NOFS) satellites. Upstream solar wind conditions are provided by the ACE spacecraft. We find that the wave power observed on the ground also occurs in the upstream solar wind and in the magnetosphere. All these observations demonstrate that Pc5 waves with a likely driver in the solar wind can penetrate to the equatorial ionosphere and modulate the equatorial electrodynamics. While no direct drift measurements from equatorial radars exist for the 9 August 2008 event, we used JULIA 150 km radar drift velocities observed on 2 May 2010 and found similar fluctuations with the period of 5-8 min, as a means of an independent confirmation of our magnetometer derived drift dynamics.

  2. Waving in the rain

    CERN Document Server

    Cavaleri, Luigi; Bidlot, Jean-Raymond

    2015-01-01

    We consider the effect of rain on wind wave generation and dissipation. Rain falling on a wavy surface may have a marked tendency to dampen the shorter waves in the tail of the spectrum, the related range increasing with the rain rate. Following the coupling between meteorological and wave models, we derive that on the whole this should imply stronger wind and higher waves in the most energetic part of the spectrum. This is supported by numerical experiments. However, a verification based on the comparison between operational model results and measured data suggests that the opposite is true. This leads to a keen analysis of the overall process, in particular on the role of the tail of the spectrum in modulating the wind input and the white-capping. We suggest that the relationship between white-capping and generation by wind is deeper and more implicative than presently generally assumed.

  3. Whither Acid Rain?

    Directory of Open Access Journals (Sweden)

    Peter Brimblecombe

    2000-01-01

    Full Text Available Acid rain, the environmental cause célèbre of the 1980s seems to have vanished from popular conscience. By contrast, scientific research, despite funding difficulties, has continued to produce hundreds of research papers each year. Studies of acid rain taught much about precipitation chemistry, the behaviour of snow packs, long-range transport of pollutants and new issues in the biology of fish and forested ecosystems. There is now evidence of a shift away from research in precipitation and sulfur chemistry, but an impressive theoretical base remains as a legacy.

  4. PMP-2: Equatorial wave dynamics

    Science.gov (United States)

    Hirota, I.

    1982-01-01

    After the discovery of the quasi-biennial oscillation (QBO) in the stratospheric zonal wind, there were, in the last two decades, a large number of observational and theoretical studies on the structure and behavior of the mean zonal wind and waves in the tropical stratosphere. Planetary-scale, vertically propagating equatorial waves play an important role in producing the QBO through the mechanism of wave-mean flow interaction. Concerning the dynamics of the equatorial upper stratosphere and mesosphere, however, little was known about the possible wave motions, except for tides, mainly because of the lack of adequate observations in this region. The main purpose is to provide the nature of various types of equatorial wave modes, with the aid of improved sounding techniques and sophisticated numerical modelings.

  5. The value of rain

    NARCIS (Netherlands)

    Snellen, W.B.

    2006-01-01

    This paper explores the gains that can be made by shifting the focus of water resources management from the water towards the rain. This causes also a shift in perception of what is the largest user of water: instead of irrigation it is the evapotranspiration

  6. Rain Forest Dance Residency.

    Science.gov (United States)

    Watson, Dawn

    1997-01-01

    Outlines the author's experience as a dancer and choreographer artist-in-residence with third graders at a public elementary school, providing a cultural arts experience to tie in with a theme study of the rain forest. Details the residency and the insights she gained working with students, teachers, and theme. (SR)

  7. Rain of Seattle

    Institute of Scientific and Technical Information of China (English)

    Julie Jindal

    2006-01-01

    @@ I've got a deep secret few people understand and even fewer will admit to sharing. It's time to tell the truth: I love the rain, deeply and passionately and more than the sun. At least I live in the right place, famous for its damp weather and spawning its own genuine rainforest.

  8. After the Rain: Animals.

    Science.gov (United States)

    Old Elk, Arlene; Stoklas, Jackie

    The Heard Museum (Phoenix, Arizona) has developed and updated an integrated curriculum for use in grades K-3. The goals for this curriculum are to: (1) share museum resources with schools; (2) promote cross-cultural understanding through a focus on rain, a universal requirement for life; (3) help students understand that Native Americans are…

  9. Acid Rain Investigations.

    Science.gov (United States)

    Hugo, John C.

    1992-01-01

    Presents an activity in which students investigate the formation of solid ammonium chloride aerosol particles to help students better understand the concept of acid rain. Provides activity objectives, procedures, sample data, clean-up instructions, and questions and answers to help interpret the data. (MDH)

  10. The Acid Rain Game.

    Science.gov (United States)

    Rakow, Steven J.; Glenn, Allen

    1982-01-01

    Provides rationale for and description of an acid rain game (designed for two players), a problem-solving model for elementary students. Although complete instructions are provided, including a copy of the game board, the game is also available for Apple II microcomputers. Information for the computer program is available from the author.…

  11. Acid Rain Classroom Projects.

    Science.gov (United States)

    Demchik, Michael J.

    2000-01-01

    Describes a curriculum plan in which students learn about acid rain through instructional media, research and class presentations, lab activities, simulations, design, and design implementation. Describes the simulation activity in detail and includes materials, procedures, instructions, examples, results, and discussion sections. (SAH)

  12. Authigenic Uranium in Eastern Equatorial Pacific Sediments

    Science.gov (United States)

    Marcantonio, F.; Lyle, M. W.; Loveley, M. R.; Ibrahim, R.

    2014-12-01

    Authigenic U concentrations have been used as an indicator of redox state in marine sediments. Soluble U(VI) in porewaters is reduced to insoluble U(IV) under suboxic conditions setting up a diffusion gradient through which U in bottom waters is supplied to reducing sediments. Researchers have used sedimentary redox enrichment of U as a tool to identify past redox changes, which may be caused by changes in organic carbon rain rates and/or bottom water oxygen levels. Differentiating between these two explanations is important, as the former is tied to the use of authigenic U as a paleoproductivity proxy. We examined sediments from 4 sediment cores retrieved from two different localities in the Panama Basin in the eastern equatorial Pacific. Two cores were retrieved from the northern Panama basin at the Cocos Ridge, (4JC at 5° 44.7'N 85° 45.5' W, 1730 m depth; 8JC at 6° 14.0'N 86° 2.6' W, 1993 m depth), and two were retrieved from the south at the Carnegie Ridge, (11JC at 0° 41.6'S 85° 20.0' W, 2452 m depth; 17JC at 0° 10.8'S 85° 52.0' W, 2846 m depth). Using 230Th systematics and seismic profiling at each of the sites, we've identified significant sediment winnowing (4JC and 11JC) and focusing (8JC and 17JC). At all sites, we believe that changes in age-model-derived sand (i.e., >63µm) mass accumulation rates (MAR) best represent changes in rain rates. Glacial rain rates are higher than those in the Holocene by a factor of 2-3 at both sites. Peak Mn levels (>1%), the brown-to-green color transition (which likely represents the oxic/post-oxic boundary), and peak U concentrations all appear in the same order with increasing depth down core. At the Carnegie sites, where MARs are greater than those at the Cocos sites, increases in authigenic U (up to 4 ppm) occur during the mid- to late Holocene at depths of 10-15 cm. At the Cocos sites, increases in authigenic U (up to 12 ppm) occur lower in the sediment column (25-30 cm) during the late glacial. The decrease

  13. Rain Drop Charge Sensor

    Science.gov (United States)

    S, Sreekanth T.

    begin{center} Large Large Rain Drop Charge Sensor Sreekanth T S*, Suby Symon*, G. Mohan Kumar (1) , S. Murali Das (2) *Atmospheric Sciences Division, Centre for Earth Science Studies, Thiruvananthapuram 695011 (1) D-330, Swathi Nagar, West Fort, Thiruvananthapuram 695023 (2) Kavyam, Manacaud, Thiruvananthapuram 695009 begin{center} ABSTRACT To study the inter-relations with precipitation electricity and precipitation microphysical parameters a rain drop charge sensor was designed and developed at CESS Electronics & Instrumentation Laboratory. Simultaneous measurement of electric charge and fall speed of rain drops could be done using this charge sensor. A cylindrical metal tube (sensor tube) of 30 cm length is placed inside another thick metal cover opened at top and bottom for electromagnetic shielding. Mouth of the sensor tube is exposed and bottom part is covered with metal net in the shielding cover. The instrument is designed in such a way that rain drops can pass only through unhindered inside the sensor tube. When electrically charged rain drops pass through the sensor tube, it is charged to the same magnitude of drop charge but with opposite polarity. The sensor tube is electrically connected the inverted input of a current to voltage converter operational amplifier using op-amp AD549. Since the sensor is electrically connected to the virtual ground of the op-amp, the charge flows to the ground and the generated current is converted to amplified voltage. This output voltage is recorded using a high frequency (1kHz) voltage recorder. From the recorded pulse, charge magnitude, polarity and fall speed of rain drop are calculated. From the fall speed drop diameter also can be calculated. The prototype is now under test running at CESS campus. As the magnitude of charge in rain drops is an indication of accumulated charge in clouds in lightning, this instrument has potential application in the field of risk and disaster management. By knowing the charge

  14. Variability In Sloan's Equatorial Stripe

    Science.gov (United States)

    Rashkov, Valery; Spergel, D.; Strauss, M.; Ivezic, Z.; Sesar, B.

    2007-12-01

    The Sloan Digital Sky Survey (SDSS) equatorial Stripe 82 is located between 22h 24min Branimir Sesar (Sesar et al., 2007) have put together a list of 13051 variable sources, each of which was observed an average of 20 times. I have calculated fits for two variability parameters (amplitude and characteristic timescale) for these objects using maximum likelihood statistics. The list is being probed for violent variability, as from BL Lac Objects and OVVs. Knowledge of these objects' parameters will help separate their contribution in the microwave from that of the CMB when the equatorial Stripe 82 is eventually observed with the Atacama Cosmology Telescope.

  15. Weighing Rain Gauge Recording Charts

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Weighing rain gauge charts record the amount of precipitation that falls at a given location. The vast majority of the Weighing Rain Gauge Recording Charts...

  16. When It Rains, It Pours

    Science.gov (United States)

    Mills, Linda

    2012-01-01

    "It's raining, it's pouring, the old man is snoring!" "The itsy, bitsy spider crawled up the waterspout, down came the rain and washed the spider out. Out came the sun and dried up all the rain, and the itsy, bitsy spider went up the spout again." What do children's nursery rhymes have to do with the school library? The author begins by telling a…

  17. Adaptive rain fade compensation

    Science.gov (United States)

    Rautio, J. C.

    1980-01-01

    A large available margin must be provided for satellite communications systems operating near 20 GHz, which occasionally experience fades due to rain attenuation. It is proposed that this margin may be achieved in high-capacity FDMA satellites by dynamically providing a large margin to those links which are experiencing deep fades, while maintaining a small fade margin on all others. Single-beam SCPC operation and multiple-beam, satellite-switched FDMA systems are described, and the optimization of the dynamic FDMA links in a severely fading environment is investigated. A solution is derived which takes into account: (1) transponder intermodulation distortion, (2) cochannel and cross-polarization antenna interference, and (3) rain fade characteristics. The sample system configuration presented shows that such systems reach availability levels approaching 0.9999 at Ka-Band.

  18. Decisive Thaw: The Changing Pattern of Relations between Nigeria and Equatorial Guinea, 1980-2005

    Directory of Open Access Journals (Sweden)

    David Aworawo

    2010-04-01

    Full Text Available This article examines the nature and changing pattern of relations between Nigeria and Equatorial Guinea from 1980-2005. It states that relations between the countries improved tremendously in the quarter century covered in this study compared to the two decades preceding that time frame (1960-1980 due to of a number of domesticpolitical and economic changes that occurred in both countries, as well as the transformation of the international system in the late 1980s and early 1990s. The paper explores the specific changes that took place in Nigerian-Equatorial Guinean relations from1980 onwards and the factors that influenced them. The termination of the brutal and violent rule of President Macias Nguema in Equatorial Guinea opened the way for improved relations between Nigeria and Equatorial Guinea. The shift from dependence on cocoa to petroleum exports in Equatorial Guinea also helped to promote cordial relations since the ill-treatment of Nigerian workers in Equatorial Guinea’s cocoa plantations had been a thorny issue in Nigerian-Equatorial Guinean relations in previous decades. The end of the Cold War and apartheid between 1989 and 1994 were also important factors that shaped relations. All these were issues that had previously negatively affected cordial relations between the countries. Thisarticle therefore discusses relations between Nigeria and Equatorial Guinea within the context of the post-Cold War international system and intra-African relations. It also argues that although improvements were recorded in Nigerian-Equatorial Guinean relations between 1980 and 2005, there remain numerous avenues that could be explored for yet better relations.

  19. Equatorial Spread F Fossil Plumes

    Science.gov (United States)

    2010-11-01

    Satyanarayana , P., and Ossakow, S. L.: The morphology of a multi-bubble system in the ionosphere, J. Geophys. Res., 88, 5528–5536, 1983. de La Beaujardiere...Haerendel, G.: Theory of equatorial spread F , preprint, Max Planck Inst. Extraterr. Phys., Munich, Germany, 1974. Haerendel, G., Eccles, J. V ., and...weather issues, J. Atmos. Terr. Phys., 58, 1527–1574, 1996. Sekar, R., Chakrabarty, D., Sarkhel, S., Patra, A. K., Devasia, C. V ., and Kelley, M. C

  20. Music after the rain

    CERN Multimedia

    2006-01-01

    The group Home Cooking (left to right: Jean-Marie Planche, Tony Arnold, Serge Waeffler, Django Manglunki) entertains the crowd with a humoristic blues/rock performance. The earth moved in Prévessin on 29 July. This was not an earthquake but an 'international' music event, the seventeenth CERN Hardronic Festival, which saw musicians from many different countries, including Russia, Britain, Spain, France, Belgium and the USA, take to the stage. The audience rocked to music from eight different groups until the early hours. About a thousand people flocked to CERN to hear what the best of its musical talents had to offer. The evening was very nearly a wash-out, though. After a week of scorching hot temperatures, the heavens suddenly opened and the rain didn't stop until a few minutes before the first act came on stage. Thanks to this narrow escape, the organisers can boast a 17-year run of rain-free Hardronic festivals. All the different musical styles were given a warm reception, from traditional Russian folk...

  1. A local index of Maritime Continent intraseasonal variability based on rain rates over the land and sea

    Science.gov (United States)

    Vincent, C. L.; Lane, T. P.; Wheeler, M. C.

    2016-09-01

    A local index for describing intraseasonal variability over the Maritime Continent is developed. The index is based on the ratio of area-averaged rain rate over the land to that over the sea. It takes advantage of the fact that the main convective envelope of intraseasonal variability events tends to modulate the diurnal precipitation cycle over the land over the entire Maritime Continent. Lagged analysis is used to create composite intraseasonal variability events, where "day 0" is chosen according to when the normalized rain rate over the sea becomes greater than that over the land. The index identifies intraseasonal variability events associated with the Madden Julian Oscillation as well as equatorial Kelvin waves and westward propagating equatorial Rossby waves. The results suggest a similar local impact of all such events in suppressing the rain rate over land relative to that over the sea when the main convective envelope approaches.

  2. Optimal Broadcasting of Mixed Equatorial Qubits

    Institute of Scientific and Technical Information of China (English)

    YU Zong-Wen

    2009-01-01

    We derive an optimal 2→M phase-covariant quantum broadcasting of mixed equatorial qubits.This quantum broadcasting is optimal in the sense that the shrinking factor between the input and the output single qubit achieves the upper bound.The result shows that we can copy two identical mixed equatorial qubits with the same quality as those of two identical pure equatorial states.

  3. The Rain Keeps Falling

    Directory of Open Access Journals (Sweden)

    Deborah Rose

    2013-08-01

    Full Text Available The force of disaster hit me in the heart when, as a young woman, I heard Bob Dylan sing ‘Hard Rain’. In a voice stunned by violence, the young man reports on a multitude of forces that drag the world into catastrophe. In the 1960s I heard the social justice in the song. In 2004 the environmental issues ambush me. The song starts and ends in the dying world of trees and rivers. The poet’s words in both domains of justice are eerily prophetic. They call across the music, and across the years, saying that a hard rain is coming. The words bear no story at all; they give us a series of compelling images, an account of impending calamity. The artistry of the poet—Bob (Billy Boy Dylan—offers sequences of reports that, like Walter Benjamin’s storm from paradise, pile wreckage upon wreckage.

  4. Dust Rains Deliver Diverse Assemblages of Microorganisms to the Eastern Mediterranean

    Science.gov (United States)

    Itani, Ghida Nouhad; Smith, Colin Andrew

    2016-03-01

    Dust rains may be particularly effective at delivering microorganisms, yet their biodiversities have been seldom examined. During 2011 and 2012 in Beirut, Lebanon, 16 of 21 collected rainfalls appeared dusty. Trajectory modelling of air mass origins was consistent with North African sources and at least one Southwest Asian source. As much as ~4 g particulate matter, ~20 μg DNA, and 50 million colony forming units were found deposited per square meter during rainfalls each lasting less than one day. Sequencing of 93 bacteria and 25 fungi cultured from rain samples revealed diverse bacterial phyla, both Gram positive and negative, and Ascomycota fungi. Denaturing Gradient Gel Electrophoresis of amplified 16S rDNA of 13 rains revealed distinct and diverse assemblages of bacteria. Dust rain 16S libraries yielded 131 sequences matching, in decreasing order of abundance, Betaproteobacteria, Alphaproteobacteria, Firmicutes, Actinobacteria, Bacteroidetes, Cyanobacteria, Epsilonproteobacteria, Gammaproteobacteria, and Deltaproteobacteria. Clean rain 16S libraries yielded 33 sequences matching only Betaproteobacteria family Oxalobacteraceae. Microbial composition varied between dust rains, and more diverse and different microbes were found in dust rains than clean rains. These results show that dust rains deliver diverse communities of microorganisms that may be complex products of revived desert soil species and fertilized cloud species.

  5. Acid Rain Limits Global Warming

    Institute of Scientific and Technical Information of China (English)

    Will Knight; 张林玲

    2004-01-01

    @@ Acid rain restricts global warming by reducing methane① emissions from natural wetland areas, suggests a global climate study. Acid rain is the result of industrial pollution,which causes rainwater to carry small quantities of acidic compoumds② such as sulphuric and nitric acid③. Contaminated rainwater can upset rivers and lakes, killing fish and other organisms and also damage plants, trees and buildings.

  6. Acid Rain: The Scientific Challenge.

    Science.gov (United States)

    Godfrey, Paul J.

    1991-01-01

    Documents the workings and findings of the Massachusetts Acid Rain Monitoring Project, which has pooled the volunteer efforts of more than 1,000 amateur and professional scientists since 1983. Reports on the origins of air pollution, the prediction of acid rain, and its effects on both water life and land resources. (JJK)

  7. Acid Rain: What's the Forecast?

    Science.gov (United States)

    Bybee, Rodger

    1984-01-01

    Discusses various types of acid rain, considered to be a century-old problem. Topics include: wet and dry deposition, effects on a variety of environments, ecosystems subject to detrimental effects, and possible solutions to the problem. A list of recommended resources on acid rain is provided. (BC)

  8. Morphological Characterization of African Bush Mango trees (Irvingia species) in the Dahomey Gap (West Africa)

    NARCIS (Netherlands)

    Vihotogbe, R.; Berg, van den R.G.; Sosef, M.S.M.

    2013-01-01

    The variation of the morphological characters of bitter and sweet African bush mango trees (Irvingia species) was investigated in the Dahomey Gap which is the West African savannah woodland area separating the Upper and the Lower Guinean rain forest blocks. African bush mangoes have been rated as th

  9. Structural characteristics of rain fields

    Science.gov (United States)

    Mesnard, FréDéRic; Sauvageot, Henri

    2003-07-01

    This paper analyzes the shape of rain area size distributions (RASDs) observed by radar in tropical and midlatitude regions. The rain area is defined, with respect to a rain threshold τ, as the area, inside a contour, where the rain rate is higher than τ. The size considered is the diameter of the equivalent circular area D. The reflectivity peaks inside the rain areas are numbered and the rain areas put together by classes having the same peak number. The size distributions of the rain areas containing the same number of peaks p are well fitted by lognormal functions, the parameters of which, μp and σp, are weakly dependent on the conditions of the peak determination. The parameters μp and σp are found to be linked by a power relation. For D RASD without peak number distinction is a lognormal mixture. Using the relations obtained for μp, σp, and the rain area number as functions of p enables one to simulate RASDs with results in good agreement with the observations. Because of the limitation in the radar sampling at both ends of the RASD and the decrease of area number with increasing size, the radar-observed RASDs are severely truncated. The possibility of an approximate fitting of the truncated RASD with diverse functions is discussed. At the intermediary values of the threshold, i.e., for τ ranging between 3 and 12 mm h-1, where the RASD is easiest to compute, the slope of these truncated distributions is not strongly dependent on the threshold. This slope appears not to be very sensitive to the minimum and maximum distances bounding the domain where the rain field is observed. The RASD is found to be sloping more over sea than over land. The slope of the RASDs shows a small diurnal variation but no significant annual variation. The "perimeter to area" (fractal) dimension of the rain area for the sample without peak number distinction is around 1.35. Single-peaked and multipeaked rain areas have different perimeter to area dimensions, ˜1.23 and 1

  10. On the modelling of equatorial waves

    Science.gov (United States)

    Constantin, A.

    2012-03-01

    The present theory of geophysical waves that either raise or lower the equatorial thermocline, based on the reduced-gravity shallow-water equations on the β-plane, ignores vertical variations of the flow. In particular, the vertical structure of the Equatorial Undercurrent is absent. As a remedy we propose a simple approach by modeling this geophysical process as a wave-current interaction in the f-plane approximation, the underlying current being of positive constant vorticity. The explicit dispersion relation allows us to conclude that, despite its simplicity, the proposed model captures to a reasonable extent essential features of equatorial waves.

  11. Ozone and Aitken nuclei over equatorial Africa - Airborne observations during DECAFE 88

    Science.gov (United States)

    Andreae, M. O.; Chapuis, A.; Cros, B.; Fontan, J.; Helas, G.; Justice, C.; Kaufman, Y. J.; Minga, A.; Nganga, D.

    1992-04-01

    Results of ozone and Aitken condensation nuclei measurements made over the rain forest in equatorial Africa during February 12-25, 1988 are presented. The results indicate the presence of a layer between 1 and 4 km altitude where these species are strongly enriched. Based on information derived from simultaneous measurements of other chemical and meteorological parameters, satellite imagery, and trajectory calculations, this enrichment is attributed to emissions from biomass burning in sub-Saharan Africa, from which ozone is formed by photochemical reactions.

  12. Ozone and Aitken nuclei over equatorial Africa - Airborne observations during DECAFE 88

    Science.gov (United States)

    Andreae, M. O.; Chapuis, A.; Cros, B.; Fontan, J.; Helas, G.; Justice, C.; Kaufman, Y. J.; Minga, A.; Nganga, D.

    1992-01-01

    Results of ozone and Aitken condensation nuclei measurements made over the rain forest in equatorial Africa during February 12-25, 1988 are presented. The results indicate the presence of a layer between 1 and 4 km altitude where these species are strongly enriched. Based on information derived from simultaneous measurements of other chemical and meteorological parameters, satellite imagery, and trajectory calculations, this enrichment is attributed to emissions from biomass burning in sub-Saharan Africa, from which ozone is formed by photochemical reactions.

  13. Diversity among African pygmies.

    Directory of Open Access Journals (Sweden)

    Fernando V Ramírez Rozzi

    Full Text Available Although dissimilarities in cranial and post-cranial morphology among African pygmies groups have been recognized, comparative studies on skull morphology usually pull all pygmies together assuming that morphological characters are similar among them and different with respect to other populations. The main aim of this study is to compare cranial morphology between African pygmies and non-pygmies populations from Equatorial Africa derived from both the Eastern and the Western regions in order to test if the greatest morphological difference is obtained in the comparison between pygmies and non-pygmies. Thirty three-dimensional (3D landmarks registered with Microscribe in four cranial samples (Western and Eastern pygmies and non-pygmies were obtained. Multivariate analysis (generalized Procrustes analysis, Mahalanobis distances, multivariate regression and complementary dimensions of size were evaluated with ANOVA and post hoc LSD. Results suggest that important cranial shape differentiation does occur between pygmies and non-pygmies but also between Eastern and Western populations and that size changes and allometries do not affect similarly Eastern and Western pygmies. Therefore, our findings raise serious doubt about the fact to consider African pygmies as a homogenous group in studies on skull morphology. Differences in cranial morphology among pygmies would suggest differentiation after divergence. Although not directly related to skull differentiation, the diversity among pygmies would probably suggest that the process responsible for reduced stature occurred after the split of the ancestors of modern Eastern and Western pygmies.

  14. Swarm equatorial electric field chain: First results

    OpenAIRE

    Alken, P; Maus, S.; A. Chulliat; Vigneron, P.; Sirol, O.; Hulot, G.

    2015-01-01

    International audience; The eastward equatorial electric field (EEF) in the E region ionosphere drives many important phenomena at low latitudes. We developed a method of estimating the EEF from magnetometer measurements of near-polar orbiting satellites as they cross the magnetic equator, by recovering a clean signal of the equatorial electrojet current and modeling the observed current to determine the electric field present during the satellite pass. This algorithm is now implemented as an...

  15. Statistical and Physical Descriptions of Raindrop Size Distributions in Equatorial Malaysia from Disdrometer Observations

    Directory of Open Access Journals (Sweden)

    Hong Yin Lam

    2015-01-01

    Full Text Available This work investigates the physical characteristics of raindrop size distribution (DSD in an equatorial heavy rain region based on three years of disdrometer observations carried out at Universiti Teknologi Malaysia’s (UTM’s campus in Kuala Lumpur, Malaysia. The natural characteristics of DSD are deduced, and the statistical results are found to be in accordance with the findings obtained from others disdrometer measurements. Moreover, the parameters of the Gamma distribution and the normalized Gamma model are also derived by means of method of moment (MoM and maximum likelihood estimation (MLE. Their performances are subsequently validated using the rain rate estimation accuracy: the normalized Gamma model with the MLE-generated shape parameter µ was found to provide better accuracy in terms of long-term rainfall rate statistics, which reflects the peculiarities of the local climatology in this heavy rain region. These results not only offer a better understanding of the microphysical nature of precipitation in this heavy rain region but also provide essential information that may be useful for the scientific community regarding remote sensing and radio propagation.

  16. African Literature

    OpenAIRE

    Recek, Denis

    2011-01-01

    The topic of this diploma is the formation and shaping of African literature. The first chapter is about the beginning of African literature. It describes oral literature and its transmission into written literature. Written African literature had great problems in becoming a part of world literature because of its diversity of languages and dialects. Christianity and Islam are mentioned as two religions which had a great impact on African literature. Colonialism is broadly described as an es...

  17. Benefiting Africans

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    Along with thriving Sino-African economic and trade ties,Chinese companies have attached greater importance to their social responsibility to Africans.More than 2,000 sweaters woven by Chinese mothers were sent to orphans and disabled children in Kenya and four other African countries in September. This activity was launched by Hengyuanxiang,aleading Chinese wool manufacturer.

  18. Benefiting Africans

    Institute of Scientific and Technical Information of China (English)

    ZHANG ZHIPING

    2011-01-01

    Along with thriving Sino-African economic and trade ties,Chinese companies have attached greater importance to their social responsibility to Africans.More than 2,000 sweaters woven by Chinese mothers were sent to orphans and disabled children in Kenya and four other African countries in September.This activity was launched by Hengyuanxiang,a leading Chinese wool manufacturer.

  19. Central African Republic.

    Science.gov (United States)

    1986-02-01

    Focus in this discussion of the Central African Republic is on: geography; the people; history and political conditions; government; the economy; foreign relations; and relations with the US. The population of the Central African Republic totaled 2.7 million in 1985 with an annual growth rate of 2.8%. The infant mortality rate is 134/1000 with life expectancy at 49 years. The Central African Republic is at almost the precise center of Africa, about 640 km from the nearest ocean. More than 70% of the population live in rural areas. There are more than 80 ethnic groups, each with its own language. The precolonial history of the area was marked by successive waves of migration, of which little is known. These migrations are responsible for the complex ethnic and linguistic patterns today. United with Chad in 1906, it formed the Oubangui-Chari-Chad colony. In 1910, it became 1 of the 4 territories of the Federation of French Equatorial Africa, along with Chad, Congo, and Gabon. After World War II, the French Constitution of 1946 inaugurated the first of a series of reforms that led eventually to complete independence for all French territories in western and equatorial Africa. The nation became an autonomous republic within the newly established French Community on December 1, 1958, and acceded to complete independence as the Central Africa Republic on August 13, 1960. The government is made up of the executive and the judicial branches. The constitution and legislature remain suspended. All executive and legislative powers, as well as judicial oversight, are vested in the chief of state. The Central African Republic is 1 of the world's least developed countries, with an annual per capita income of $310. 85% of the population is engaged in subsistence farming. Diamonds account for nearly 1/3 of export earnings; the industrial sector is limited. The US terminated bilateral assistance programs in 1979, due to the human rights violations of the Bokassa regime, but modest

  20. Asian irrigation, African rain: Remote impacts of irrigation

    Science.gov (United States)

    Vrese, Philipp; Hagemann, Stefan; Claussen, Martin

    2016-04-01

    Irrigation is not only vital for global food security but also constitutes an anthropogenic land use change, known to have strong effects on local hydrological and energy cycles. Using the Max Planck Institute for Meteorology's Earth System Model, we show that related impacts are not confined regionally but that possibly as much as 40% of the present-day precipitation in some of the arid regions in Eastern Africa are related to irrigation-based agriculture in Asia. Irrigation in South Asia also substantially influences the climate throughout Southeast Asia and China via the advection of water vapor and by altering the Asian monsoon. The simulated impact of irrigation on remote regions is sensitive to the magnitude of the irrigation-induced moisture flux. Therefore, it is likely that a future extension or decline of irrigated areas due to increasing food demand or declining fresh water resources will also affect precipitation and temperatures in remote regions.

  1. Acid Rain Program Opt-in Factsheet

    Science.gov (United States)

    Learn about the Opt-in Program, which allows sources not required to participate in the Acid Rain Program the opportunity to enter the program on a voluntary basis and receive Acid Rain Program allowances.

  2. Acid Rain: What We Must Do.

    Science.gov (United States)

    Gorham, Eville

    1983-01-01

    Addresses questions about the nature, source, and history of acid rain. In addition, discusses the questions: Why is acid rain a problem? Is acid rain getting worse? What is the threat of further problems? Concludes that it is time to act on the problem and recommends an appropriate course of action. (JN)

  3. Lunar influence on equatorial atmospheric angular momentum

    Science.gov (United States)

    Bizouard, C.; Zotov, L.; Sidorenkov, N.

    2015-08-01

    This study investigates the relationship between the equatorial atmospheric angular momentum oscillation in the non-rotating frame and lunar tidal potential. Between 2 and 30 days, the corresponding equatorial component is mostly constituted of prograde circular motions, especially of a harmonic at 13.6 days, and of a weekly broad band variation. A simple equilibrium tide model explains the 13.6-day pressure term as result of the O1 lunar tide; the tidal lunar origin of the whole band from 2 to 30 days is attested by specific features, not occurring for seasonal band dominated by the solar thermal effect.

  4. The Specifications for Monitoring of Acid Rain

    Institute of Scientific and Technical Information of China (English)

    Tang Jie

    2011-01-01

    Background Since China is a country seriously affected by acid rain pollution,it is a long-term fundamental work for acid rain pollution prevention and control in China by getting well informed of the characteristics of spatial and temporal changes in acid rain and long-term trends of these changes.In order to reach the national demand for acid rain monitoring data,the China Meteorological Administration (CMA) began to construct the network of acid rain monitoring stations in 1992.By the end of 2010,the total number of monitoring stations has exceeded 340.

  5. The rain-powered cart

    Science.gov (United States)

    Mungan, Carl E.; Lipscombe, Trevor C.

    2016-09-01

    A frictionless cart in the shape of a right triangle (with the vertical side forward) is elastically impacted by vertically falling raindrops. The speed of the cart as a function of time can be analytically deduced as an exercise in the use of trigonometric and hyperbolic functions. A characteristic time defines the approach to a terminal speed which is a sizeable fraction of the speed of the rain. The treatment is accessible to a student in a calculus-based mechanics course.

  6. Acid Rain: What It Is -- How You Can Help!

    Science.gov (United States)

    National Wildlife Federation, Washington, DC.

    This publication discusses the nature and consequences of acid precipitation (commonly called acid rain). Topic areas include: (1) the chemical nature of acid rain; (2) sources of acid rain; (3) geographic areas where acid rain is a problem; (4) effects of acid rain on lakes; (5) effect of acid rain on vegetation; (6) possible effects of acid rain…

  7. PMP-2 Report: Equatorial Wave Dynamics

    Science.gov (United States)

    Hirota, I.

    1982-01-01

    The activities of the pre-MAP project 2 (PMP-2) from 1978 through 1981 are described. The following topics relating to the equatorial middle atmosphere are discussed briefly: (1) the semi-annual oscillation and Kelvin waves; (2) planetary Rossby waves; (3) upper mesospheric waves; and (4) gravity waves.

  8. Coccolithophores in the equatorial Atlantic Ocean

    DEFF Research Database (Denmark)

    Kinkel, Hanno; Baumann, K.-H.; Cepek, M.

    2000-01-01

    The present study was initiated to ascertain the significance of coccolithophores as a proxy for paleoceanographic and paleoproductivity studies in the equatorial Atlantic. Data from a range of different samples, from the plankton, surface sediments as well as sediment cores are shown and compare...

  9. Eastward traverse of equatorial plasma plumes observed with the Equatorial Atmosphere Radar in Indonesia

    OpenAIRE

    S. Fukao; Yokoyama, T.; Tayama, T.; Yamamoto, M.; Maruyama, T.; Saito, S.

    2006-01-01

    The zonal structure of radar backscatter plumes associated with Equatorial Spread F (ESF), probably modulated by atmospheric gravity waves, has been investigated with the Equatorial Atmosphere Radar (EAR) in West Sumatra, Indonesia (0.20° S, 100.32° E; dip latitude 10.1° S) and the FM-CW ionospheric sounders on the same magnetic meridian as the EAR. The occurrence locations and zonal distances of the ESF plumes were determined with multi-beam obs...

  10. Rain on small tropical islands

    Science.gov (United States)

    Sobel, A. H.; Burleyson, C. D.; Yuter, S. E.

    2011-04-01

    A high-resolution rainfall climatology based on observations from the Tropical Rainfall Measuring Mission's Precipitation Radar (PR) instrument is used to evaluate the influence of small tropical islands on climatological rainfall. Islands with areas between one hundred and several thousand km2 are considered in both the Indo-Pacific Maritime Continent and Caribbean regions. Annual mean climatological (1997-2007) rainfall over each island is compared with that over the surrounding ocean region, and the difference is expressed as a percentage. In addition to total rainfall, rain frequency and intensity are also analyzed. Results are stratified into two 12 h halves of the diurnal cycle as well as eight 3 h periods, and also by a measure of each island's topographic relief. In both regions, there is a clear difference between larger islands (areas of a few hundred km2 or greater) and smaller ones. Both rain frequency and total rainfall are significantly enhanced over larger islands compared to the surrounding ocean. For smaller islands the enhancement is either negligibly small, statistically insignificant, or, in the case of Caribbean rain frequency, negative. The enhancement in total rainfall over larger islands is partly attributable to greater frequency and partly to greater intensity. A diurnal cycle in island enhancement is evident in frequency but not intensity, except over small Caribbean islands where the converse is true. For the larger islands, higher orography is associated with greater rainfall enhancements. The orographic effect is larger (percentagewise) in the Caribbean than in the Maritime Continent. Orographic precipitation enhancement manifests more strongly as increased frequency of precipitation rather than increased intensity and is present at night as well as during the day. The lack of a clear diurnal cycle in orographic enhancement suggests that much of the orographic rainfall enhancement is attributable to mechanically forced upslope flow

  11. Human Dark Skin and Equatorial Africa: Toward a Critique

    Directory of Open Access Journals (Sweden)

    Sylvain K. Cibangu

    2015-07-01

    Full Text Available While skin color represents one of the most common markers of humans, the theories that explain it remain largely unknown both in academia and industry. Meanwhile, fraught with theoretical shortcomings about skin color, as clear from its body of knowledge, racial studies has not addressed skin color with needed attention. Consequently, misconceptions about human skin color have proliferated. This paper discusses anew Gloger’s theory and its widespread impact in the social sciences and general public. Gloger explained dark skin by heat. Not surprisingly, dark skin is believed to be the product of and response to ultra violet radiation in Equatorial Africa. One reason might be the fixation of the debate on the white-black binary. Another reason might be the commonplace belief about the African heat. The present paper calls into question the Equator-Africa presentation of black skin. To this end, the paper situates the debate in the broader spectrum of social science disciplines, and investigates the ways in which black skin is presented. The paper advocates for the consideration of skin complexity and of minorities in the field of skin color. The goal is to work toward a deeper understanding of others and their traits, with a view to raise awareness among policy makers, the general public, and social science experts. The paper takes an encyclopedic approach to best cater to these audiences.

  12. Acid rain information book. Draft final report

    Energy Technology Data Exchange (ETDEWEB)

    None

    1980-12-01

    Acid rain is one of the most widely publicized environmental issues of the day. The potential consequences of increasingly widespread acid rain demand that this phenomenon be carefully evaluated. Reveiw of the literature shows a rapidly growing body of knowledge, but also reveals major gaps in understanding that need to be narrowed. This document discusses major aspects of the acid rain phenomenon, points out areas of uncertainty, and summarizes current and projected research by responsible government agencies and other concerned organizations.

  13. Extension of the prognostic model of sea surface temperature to rain-induced cool and fresh lenses

    Science.gov (United States)

    Bellenger, Hugo; Drushka, Kyla; Asher, William; Reverdin, Gilles; Katsumata, Masaki; Watanabe, Michio

    2017-01-01

    The Zeng and Beljaars (2005) sea surface temperature prognostic scheme, developed to represent diurnal warming, is extended to represent rain-induced freshening and cooling. Effects of rain on salinity and temperature in the molecular skin layer (first few hundred micrometers) and the near-surface turbulent layer (first few meters) are separately parameterized by taking into account rain-induced fluxes of sensible heat and freshwater, surface stress, and mixing induced by droplets penetrating the water surface. Numerical results from this scheme are compared to observational data from two field studies of near-surface ocean stratifications caused by rain, to surface drifter observations and to previous computations with an idealized ocean mixed layer model, demonstrating that the scheme produces temperature variations consistent with in situ observations and model results. It reproduces the dependency of salinity on wind and rainfall rate and the lifetime of fresh lenses. In addition, the scheme reproduces the observed lag between temperature and salinity minimum at low wind speed and is sensitive to the peak rain rate for a given amount of rain. Finally, a first assessment of the impact of these fresh lenses on ocean surface variability is given for the near-equatorial western Pacific. In particular, the variability due to the mean rain-induced cooling is comparable to the variability due to the diurnal warming so that they both impact large-scale horizontal surface temperature gradients. The present parameterization can be used in a variety of models to study the impact of rain-induced fresh and cool lenses at different spatial and temporal scales.

  14. Variability of the TRMM-PR total and convective and stratiform rain fractions over the Indian region during the summer monsoon

    Science.gov (United States)

    Pokhrel, Samir; Sikka, D. R.

    2013-07-01

    Level 3 (3A25) TRMM Precipitation Radar (PR) data are used for 13 years period (1998-2010) to prepare climatology of TRMM PR derived near surface rain (Total rain) and rain fractions for the 4-months duration of Indian Summer Monsoon season (June-September) as well as for individual months. It is found that the total rain is contributed mostly (99 %) by two rain fractions i.e. stratiform and convective rain fractions for the season as well as on the monthly basis. It is also found that total rain estimates by PR are about 65 % of the gauge measured rain over continental India as well as on sub-regional basis. Inter-annual variability of TRMM-PR rain estimates for India mainland and its sub-regions as well as over the neighboring oceanic regions, in terms of coefficient of variability (CV) is discussed. The heaviest rain region over north Bay of Bengal (BoB) is found to have the lowest CV. Another sub-region of low CV lies over the eastern equatorial Indian ocean (EEIO). The CVs of total rain as well as its two major constituents are found to be higher on monthly basis compared to seasonal basis. Existence of a well known dipole between the EEIO and the north BoB is well recognized in PR data also. Significant variation in PR rainfall is found over continental India between excess and deficit monsoon seasons as well as between excess and deficit rainfall months of July and August. Examination of rainfall fractions between the BoB and Central India on year to year basis shows that compensation in rainfall fractions exists on monthly scale on both the regions. Also on the seasonal and monthly scales, compensation is observed in extreme monsoon seasons between the two regions. However, much less compensation is observed between the north BoB and EEIO belts in extreme rain months. This leads to speculation that the deficit and excess seasons over India may result from slight shift of the rainfall from Central India to the neighboring oceanic regions of north Bo

  15. Moon influence on equatorial atmospheric angular momentum

    Science.gov (United States)

    Bizouard, Christian; Zotov, Leonid; Sidorenkov, Nikolay

    2014-05-01

    The variation of the equatorial atmospheric angular momentum function, coordinated with respect to a star-fixed system, is investigated in relation with the lunar tide. We isolate the rapid fluctuations, below 30 days, where Moon motion has a possible influence. First we notice that pressure term and wind term are almost proportional, by contrast to celestial seasonal band (S1). This would mean that, in this frequency band, the torque of the atmosphere on the solid Earth mostly results from the equatorial bulge. Spectrum reveals sharp lunar tidal peaks at 13.66 days (O1 diurnal tide in the terrestrial frame) and 13.63 days, reflecting the Moon influence on meridional circulation. We also observe powerful episodic fluctuations between 5 and 8 days (up to 10 mas), possibly resulting from non linear effect of the O1 tide, or tidal waves 2Q1 (6.86 days) and σ1 (7.095 days).

  16. Understanding the Unique Equatorial Density Irregularities

    Science.gov (United States)

    2015-04-01

    HF Coherent Backscatter Radar (Blue Nile Radar) at Bahir Dar University in collaboration with AFRL in November 2014. Ionospheric empirical models such...equatorial plasma bubbles, Africa 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT SAR 18, NUMBER OF PAGES 12 19a. NAME OF RESPONSIBLE...satellite signal receivers, VLF, VHF and so on in collaborating with institutions found outside Ethiopia. As a continua- tion of hosting instruments, HF

  17. Anomalous opening of the Equatorial Atlantic due to an equatorial mantle thermal minimum

    Science.gov (United States)

    Bonatti, Enrico

    1996-09-01

    The geology of the Equatorial Atlantic is dominated by a broad east-west megashear belt where a cluster of large fracture zones offsets anomalously deep segments of the Mid-Atlantic Ridge (MAR). The origin and evolution of this megashear region may lie ultimately in an equatorial mantle thermal minimum. The notion of a mantle thermal minimum in the Equatorial Atlantic is supported by an equatorial minimum of zero-age topography, a maximum in mantle shear waves seismic velocity and a minimum in the degree of melting, indicated by the chemistry of MAR basalts and peridotites. This thermal minimum has probably been a stable feature since before the Cretaceous separation of Africa from South America; it caused a pre-opening equatorial continental lithosphere thicker and colder than normal. The Cretaceous Benue Trough in western Africa and the Amazon depression in South America are interpreted as morphostructural depressions created or rejuvenated by strike-slip, transpressional and transtensional tectonics ducing extension of the cold/thick equatorial lithosphere. The oceanic rift propagating northward from the South Atlantic impinged against the equatorial thicker, colder and, therefore, stronger than normal continental, lithosphere that consequently acted as a 'locked zone'. This, and a low magmatic budget due to the cold upper mantle, caused a lower than normal rate of propagation of the oceanic rift into the equatorial belt, with diffuse deformation during mostly amagmatic extension. The thick/cold lithosphere prevented major Cretaceous igneous activity from the St. Helena plume. Eventually initial 'weak' isolated nuclei oceanic lithosphere were emplaced, separated by E-W continent/continent transforms. Opening occurred largely by strike-slip motion along these initial transforms. The consequences were that the Equatorial Atlantic opened prevalently along an E-W direction, in contrast to the N-S opening of the North and South Atlantic, and that sheared continental

  18. Acid Thunder: Acid Rain and Ancient Mesoamerica

    Science.gov (United States)

    Kahl, Jonathan D. W.; Berg, Craig A.

    2006-01-01

    Much of Mesoamerica's rich cultural heritage is slowly eroding because of acid rain. Just as water dissolves an Alka-Seltzer tablet, acid rain erodes the limestone surfaces of Mexican archaeological sites at a rate of about one-half millimeter per century (Bravo et al. 2003). A half-millimeter may not seem like much, but at this pace, a few…

  19. Acid Rain. LC Science Tracer Bullet.

    Science.gov (United States)

    Hollmann, Pauline, Comp.

    The term "acid rain," also called "acid precipitation," generally refers to any precipitation having a pH value of less than 5.6. This guide to the literature on acid rain in the collections of the Library of Congress is not necessarily intended to be a comprehensive bibliography. It is designed to provide the reader with a set…

  20. Scale Dependence of Spatiotemporal Intermittence of Rain

    Science.gov (United States)

    Kundu, Prasun K.; Siddani, Ravi K.

    2011-01-01

    It is a common experience that rainfall is intermittent in space and time. This is reflected by the fact that the statistics of area- and/or time-averaged rain rate is described by a mixed distribution with a nonzero probability of having a sharp value zero. In this paper we have explored the dependence of the probability of zero rain on the averaging space and time scales in large multiyear data sets based on radar and rain gauge observations. A stretched exponential fannula fits the observed scale dependence of the zero-rain probability. The proposed formula makes it apparent that the space-time support of the rain field is not quite a set of measure zero as is sometimes supposed. We also give an ex.planation of the observed behavior in tenus of a simple probabilistic model based on the premise that rainfall process has an intrinsic memory.

  1. FLUID EXCHANGE ACROSS THE EQUATORIAL FRONT

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In this paper, the cusp-shaped wave pattern (Legeckis wave) along the Equatorial Front (EF) is modeled by a meandering jet, and the motion of fluid parcels in a two-dimensional kinematic model of the meandering jet along EF is studied using Melnikov's method. Results indicated that the velocity field of the cusp-shaped wave pattern can indeed be modeled by a meandering jet; that the EF will act as a barrier to fluid exchange if there is no variability, but that it is just the variability that moves the buoy across the EF.

  2. FLUID EXCHANGE ACROSS THE EQUATORIAL FRONT

    Institute of Scientific and Technical Information of China (English)

    姜传丽; 吕建; 吴德星

    2001-01-01

    In this paper, the cusp-shaped wave pattern (Legeckis wave) along the Equatorial Front (EF) is modeled by a meandering jet, and the motion of fluid parcels in a two-dimensional kine-matic model of the meandering jet along EF is studied using Melnikov's method. Results indicated that the velocity field of the cusp-shaped wave pattern can indeed be modeled by a meandering jet; that the EF will act as a barrier to fluid exchange if there is no variability, but that it is just the variability that moves the buoy across the EF.

  3. Republic of Equatorial Guinea; Statistical Appendix

    OpenAIRE

    International Monetary Fund

    2010-01-01

    This report discusses the IMF estimates and projections of the Republic of Equatorial Guinea's central government financial operations, 2001–06; the tax system as of march 2007; public investment program during 2004–06 (execution) and 2007–08 (budgeted); monetary survey during 2001–06; details of central bank and commercial bank assets during 2001–06; fiscal indicators during 2001–06; and estimates on public debts during 2001–06, etc.

  4. Equatorial Oscillations in Jupiter's and Saturn's Atmospheres

    Science.gov (United States)

    Flasar, F. Michael; Guerlet, S.; Fouchet, T.; Schinder, P. J.

    2011-01-01

    Equatorial oscillations in the zonal-mean temperatures and zonal winds have been well documented in Earth's middle atmosphere. A growing body of evidence from ground-based and Cassini spacecraft observations indicates that such phenomena also occur in the stratospheres of Jupiter and Saturn. Earth-based midinfrared measurements spanning several decades have established that the equatorial stratospheric temperatures on Jupiter vary with a cycle of 4-5 years and on Saturn with a cycle of approximately 15 years. Spectra obtained by the Composite Infrared Spectrometer (CIRS) during the Cassini swingby at the end of 2000, with much better vertical resolution than the ground-based data, indicated a series of vertically stacked warm and cold anomalics at Jupiter's equator; a similar structurc was seen at Saturn's equator in CIRS limb measurements made in 2005, in the early phase of Cassini's orbital tour. The thermal wind equation implied similar patterns of mean zonal winds increasing and decreasing with altitude. On Saturn the peak-to-pcak amplitude of this variation was nearly 200 meters per second. The alternating vertical pattern of wanner and colder cquatorial tcmperatures and easterly and westerly tendencies of the zonal winds is seen in Earth's equatorial oscillations, where the pattern descends with time, The Cassini Jupiter and early Saturn observations were snapshots within a limited time interval, and they did not show the temporal evolution of the spatial patterns. However, more recent Saturn observations by CIRS (2010) and Cassini radio-occultation soundings (2009-2010) have provided an opportunity to follow the change of the temperature-zonal wind pattern, and they suggest there is descent, at a rate of roughly one scale height over four years. On Earth, the observed descent in the zonal-mean structure is associated with the absorption of a combination of vertically propagating waves with easlerly and westerly phase velocities. The peak-to-peak zonal wind

  5. The equatorial F-layer: progress and puzzles

    Directory of Open Access Journals (Sweden)

    H. Rishbeth

    Full Text Available This work reviews some aspects of the ionospheric F-layer in the vicinity of the geomagnetic equator. Starting with a historical introduction, brief summaries are given of the physics that makes the equatorial ionosphere so interesting, concentrating on the large-scale structure rather than the smaller-scale instability phenomena. Several individual topics are then discussed, including eclipse effects, the asymmetries of the `equatorial trough', variations with longitude, the semiannual variation, the effects of the global thermospheric circulation, and finally the equatorial neutral thermosphere, including `superrotation' and possible topographic influences.

    Keyword: Ionosphere (equatorial ionosphere

  6. Equatorial electrojet in the south Atlantic anomaly region

    Indian Academy of Sciences (India)

    R G Rastogi; H Chandra; N B Trivedi; V Doumbia

    2011-04-01

    Features of the equatorial electrojet are studied at Sao Luiz (2.6°S, 44.2°W, inclination −0.25°) in eastern Brazil and Sikasso (11.3°N, 5.7°W, inclination 0.1°) in the western African sector. The stations are situated on either side of the lowest magnetic field intensity in the region of rapid changes in the declination. The daily variations of X at the two stations are almost similar with the peak around noon with maximum values during equinoxes and minimum values during J-solstices. Daily variations of Y differ with the maximum deviation of about −35 nT around noon at Sao Luiz and much smaller value of about −10 nT around 14 h LT for Sikasso. The direction of the vector varies from 15°W of north at 08 h to more than 30°W of north at 17 h for Sao Luiz and from 14°E of north to 25°W of north at 18 h for Sikasso. The plot of the deviations in X and Y at different hours for the two stations shows the points along narrow ellipses with major axis aligned along 22°W of north for Sao Luiz and along 3°W of north for Sikasso as compared to declination of 20°W for Sao Luiz and 6°W for Sikasso. The deviations in X at the two stations are fairly well correlated.

  7. Central Equatorial Pacific Experiment (CEPEX). Design document

    Energy Technology Data Exchange (ETDEWEB)

    1993-04-01

    The Earth`s climate has varied significantly in the past, yet climate records reveal that in the tropics, sea surface temperatures seem to have been remarkably stable, varying by less than a few degrees Celsius over geologic time. Today, the large warm pool of the western Pacific shows similar characteristics. Its surface temperature always exceeds 27{degree}C, but never 31{degree}C. Heightened interest in this observation has been stimulated by questions of global climate change and the exploration of stabilizing climate feedback processes. Efforts to understand the observed weak sensitivity of tropical sea surface temperatures to climate forcing has led to a number of competing ideas about the nature of this apparent thermostat. Although there remains disagreement on the processes that regulate tropical sea surface temperature, most agree that further progress in resolving these differences requires comprehensive field observations of three-dimensional water vapor concentrations, solar and infrared radiative fluxes, surface fluxes of heat and water vapor, and cloud microphysical properties. This document describes the Central Equatorial Pacific Experiment (CEPEX) plan to collect such observations over the central equatorial Pacific Ocean during March of 1993.

  8. Observational features of equatorial coronal hole jets

    Directory of Open Access Journals (Sweden)

    G. Zimbardo

    2010-03-01

    Full Text Available Collimated ejections of plasma called "coronal hole jets" are commonly observed in polar coronal holes. However, such coronal jets are not only a specific features of polar coronal holes but they can also be found in coronal holes appearing at lower heliographic latitudes. In this paper we present some observations of "equatorial coronal hole jets" made up with data provided by the STEREO/SECCHI instruments during a period comprising March 2007 and December 2007. The jet events are selected by requiring at least some visibility in both COR1 and EUVI instruments. We report 15 jet events, and we discuss their main features. For one event, the uplift velocity has been determined as about 200 km s−1, while the deceleration rate appears to be about 0.11 km s−2, less than solar gravity. The average jet visibility time is about 30 min, consistent with jet observed in polar regions. On the basis of the present dataset, we provisionally conclude that there are not substantial physical differences between polar and equatorial coronal hole jets.

  9. Midday reversal of equatorial ionospheric electric field

    Directory of Open Access Journals (Sweden)

    R. G. Rastogi

    Full Text Available A comparative study of the geomagnetic and ionospheric data at equatorial and low-latitude stations in India over the 20 year period 1956–1975 is described. The reversal of the electric field in the ionosphere over the magnetic equator during the midday hours indicated by the disappearance of the equatorial sporadic E region echoes on the ionograms is a rare phenomenon occurring on about 1% of time. Most of these events are associated with geomagnetically active periods. By comparing the simultaneous geomagnetic H field at Kodaikanal and at Alibag during the geomagnetic storms it is shown that ring current decreases are observed at both stations. However, an additional westward electric field is superimposed in the ionosphere during the main phase of the storm which can be strong enough to temporarily reverse the normally eastward electric field in the dayside ionosphere. It is suggested that these electric fields associated with the V×Bz electric fields originate at the magnetopause due to the interaction of the solar wind and the interplanetary magnetic field.

  10. Fading of Jupiter's South Equatorial Belt

    Science.gov (United States)

    Sola, Michael A.; Orton, Glenn; Baines, Kevin; Yanamandra-Fisher, Padma

    2011-01-01

    One of Jupiter's most dominant features, the South Equatorial Belt, has historically gone through a "fading" cycle. The usual dark, brownish clouds turn white, and after a period of time, the region returns to its normal color. Understanding this phenomenon, the latest occurring in 2010, will increase our knowledge of planetary atmospheres. Using the near infrared camera, NSFCAM2, at NASA's Infrared Telescope Facility in Hawaii, images were taken of Jupiter accompanied by data describing the circumstances of each observation. These images are then processed and reduced through an IDL program. By scanning the central meridian of the planet, graphs were produced plotting the average values across the central meridian, which are used to find variations in the region of interest. Calculations using Albert4, a FORTRAN program that calculates the upwelling reflected sunlight from a designated cloud model, can be used to determine the effects of a model atmosphere due to various absorption, scattering, and emission processes. Spectra that were produced show ammonia bands in the South Equatorial Belt. So far, we can deduce from this information that an upwelling of ammonia particles caused a cloud layer to cover up the region. Further investigations using Albert4 and other models will help us to constrain better the chemical make up of the cloud and its location in the atmosphere.

  11. African America.

    Science.gov (United States)

    Brodie, Carolyn S.; Brown, Gloria

    1994-01-01

    Presents an annotated bibliography of quality materials by and about African Americans in the areas of poetry, music, folklore, women, picture books, history/collective biography, authors, and professional materials. Activities are suggested in each area for Black History Month. (LRW)

  12. Pre-rain green-up is ubiquitous across southern tropical Africa: implications for temporal niche separation and model representation.

    Science.gov (United States)

    Ryan, Casey M; Williams, Mathew; Grace, John; Woollen, Emily; Lehmann, Caroline E R

    2017-01-01

    Tree phenology mediates land-atmosphere mass and energy exchange and is a determinant of ecosystem structure and function. In the dry tropics, including African savannas, many trees grow new leaves during the dry season - weeks or months before the rains typically start. This syndrome of pre-rain green-up has long been recognized at small scales, but the high spatial and interspecific variability in leaf phenology has precluded regional generalizations. We used remote sensing data to show that this precocious phenology is ubiquitous across the woodlands and savannas of southern tropical Africa. In 70% of the study area, green-up preceded rain onset by > 20 d (42% > 40 d). All the main vegetation formations exhibited pre-rain green-up, by as much as 53 ± 18 d (in the wet miombo). Green-up showed low interannual variability (SD between years = 11 d), and high spatial variability (> 100 d). These results are consistent with a high degree of local phenological adaptation, and an insolation trigger of green-up. Tree-tree competition and niche separation may explain the ubiquity of this precocious phenology. The ubiquity of pre-rain green-up described here challenges existing model representations and suggests resistance (but not necessarily resilience) to the delay in rain onset predicted under climate change.

  13. Chemistry of rain events in West Africa: evidence of dust and biogenic influence in convective systems

    Directory of Open Access Journals (Sweden)

    K. Desboeufs

    2010-10-01

    Full Text Available This paper documents the chemical composition of 7 rain events associated with mesoscale convective systems sampled at the supersite of Banizoumbou, Niger, during the first special observation periods (June–July 2006 of the African Monsoon Multidisciplinary Analyses (AMMA experiment. Time-resolved rain sampling was performed in order to discriminate the local dust scavenged at the beginning of rain event from the aerosol particles incorporated in the cloud at the end of the rain. The total elemental composition is dominated by Al, Si, Fe and Ca, indicating a high influence of dust and limited marine or anthropogenic contribution. After the aerosol wash-out, the elemental concentrations normalized to Al and the microscopic observations of diatoms, a tracer of the Bodélé depression, both indicate that the total elemental composition of rainwater is controlled by dust originating from North-eastern Saharan sources and probably incorporated in the convective cloud from the Harmattan layer. The low variability of the rain composition over the measurement period indicates a regional and temporal homogeneity of dust composition in the Harmattan layer. In the dissolved phase, the dominant anions are nitrate (NO3, sulphate (SO42− and chloride (Cl. However, between June and July we observe an increasing contribution of the organic anions (formate, acetate, oxalate associated with biogenic emissions to the total ion composition. These results confirm the large influence of biogenic emissions on the rain composition over Sahel during the wet season. The paper concludes on the capacity of mesoscale convective systems to carry simultaneously dust and biogenic compounds originating from different locations and depose them jointly. It also discusses the potential biogeochemical impact of such a phenomenon.

  14. NESDIS Blended Rain Rate (RR) Products

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The blended Rain Rate (RR) product is derived from multiple sensors/satellites. The blended products were merged from polar-orbiting and geostationary satellite...

  15. Rain Erosion/Measurement Impact Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — The FARM Rain Erosion/Impact Measurement Lab develops solutions for deficiencies in the ability of materials, coatings and designs to withstand a severe operational...

  16. TECHNOLOGICAL OPTIONS FOR ACID RAIN CONTROL

    Science.gov (United States)

    Discussed are acid rain control options available to the electric utility industry. They include coal switching, flue gas desulfurization, and such emerging lower cost technologies as Limestone Injection Multistage Burners (LIMB) and Advanced Silicate (ADVACATE), both developed ...

  17. Raine syndrome: expanding the radiological spectrum

    Energy Technology Data Exchange (ETDEWEB)

    Koob, Meriam; Dietemann, Jean-Louis [CHU de Strasbourg Hopital de Hautepierre, Service de Radiologie 2, Strasbourg (France); Doray, Berenice; Fradin, Melanie [CHU de Strasbourg, Hopital de Hautepierre, Laboratoire de Genetique Medicale, Strasbourg (France); Astruc, Dominique [CHU de Strasbourg Hopital de Hautepierre, Service de Neonatologie, Strasbourg (France)

    2011-03-15

    We describe ante- and postnatal imaging of a 1-year-old otherwise healthy girl with Raine syndrome. She presented with neonatal respiratory distress related to a pyriform aperture stenosis, which was diagnosed on CT. Signs of chondrodysplasia punctata, sagittal vertebral clefting and intervertebral disc and renal calcifications were also found on imaging. This new case confirms that Raine syndrome is not always lethal. The overlapping imaging signs with chondrodysplasia punctata and the disseminated calcifications give new insights into its pathophysiology. (orig.)

  18. Simulating Rain Fade In A Communication System

    Science.gov (United States)

    Shalkhauser, Kurt A.; Nagy, Lawrence A.; Svoboda, James K.

    1994-01-01

    Automated, computer-controlled assembly of electronic equipment developed for use in simulation testing of downlink portion of Earth/satellite microwave digital communication system. Designed to show effects upon performance of system of rain-induced fading in received signal and increases in transmitted power meant to compensate for rain-induced fading. Design of communication system improved iteratively in response to results of simulations, leading eventually to design ensuring clear, uninterrupted transmission of digital signals.

  19. Acid rain may cause senile dementia

    Energy Technology Data Exchange (ETDEWEB)

    Pearce, F.

    1985-04-25

    Aluminium, released from the soil by acid rain, may be a cause of several forms of senile dementia including Parkinson's disease and Alzheimer's disease. Many upland reservoirs, fed by acid rain, supply homes with water laced with significant amounts of aluminium. Studies in the Pacific have shown that communities living on soils that are extremely rich in bauxite, the rock containing aluminium, have a very high incidence of Alzheimer's disease.

  20. A mid-Holocene thermal maximum at the end of the African Humid Period

    NARCIS (Netherlands)

    Berke, M.A.; Johnson, T.C.; Werne, J.P.; Schouten, S.; Sinninghe Damsté, J.S.

    2012-01-01

    The termination of the African Humid Period (AHP) about 5 thousand years ago (ka) was the most dramatic climate shift in northern and equatorial Africa since the end of the Pleistocene. Based on TEX86 paleotemperature data from lake Turkana, Kenya, we show that a temperature shift of 2-4 degrees C o

  1. Phytochelatin concentrations in the equatorial Pacific

    Science.gov (United States)

    Ahner, Beth A.; Lee, Jennifer G.; Price, Neil M.; Morel, François M. M.

    1998-11-01

    Phytochelatin, an intracellular metal-binding polypeptide synthesized in eucaryotic algae in response to metals such as Cd and Cu, was measured in particulate samples collected from the equatorial Pacific. The concentrations in these samples (normalized to total particulate chl a) were unexpectedly high compared to laboratory culture data and were on average slightly more than in coastal areas where the metal concentrations are typically much greater. In part, the high field concentrations can be explained by the low cellular concentrations of chlorophyll a resulting from very low ambient Fe, but laboratory experiments provide a possible explanation for the rest of the difference. At low concentrations of inorganic Cd (Cd'=3 pM), increasing amounts of phytochelatin were induced by decreasing Zn concentrations in the culture medium of two diatoms: Thalassiosira weissflogii, a coastal species, and T. parthenaia, an isolate from the equatorial Pacific. In all previous studies, phytochelatin production has been directly correlated with increasing metal concentrations. Decreasing Co also resulted in higher phytochelatin concentrations in T. weissflogii and Emiliania huxleyi. Replicating the field concentrations of Zn, Co, and Cd in the laboratory results in cellular concentrations (amol -1 cell) that are very similar to those estimated for the field. Contrary to the expectation that high metal concentrations in the equatorial upwelling would cause elevated phytochelatin concentrations, there was no increase in phytochelatin concentrations from 20° S to 10° N—near surface samples were roughly the same at all stations. Also, most of the depth profiles had a distinct subsurface maximum. Neither of these features is readily explained by the available Zn and Cd data. Incubations with additions of Cd and Cu performed on water sampled at four separate stations induced significantly higher concentrations of phytochelatins than those in controls in a majority of the samples

  2. African-American Biography.

    Science.gov (United States)

    Martin, Ron

    1995-01-01

    Suggests sources of information for African American History Month for library media specialists who work with students in grades four through eight. Gale Research's "African-American Reference Library," which includes "African-America Biography,""African-American Chronology," and "African-American Almanac,"…

  3. Alkylmercury species in the equatorial Pacific

    Science.gov (United States)

    Mason, R. P.; Fitzgerald, W. F.

    1990-10-01

    HIGH levels of mercury in piscivorous fish constitute a long-standing health hazard1-6. Monomethyl mercury, the main form of mercury in fish, is more toxic than inorganic mercury. But although something is known of the ability of organisms to methylate mercury7,8, the sources, synthesis and fate of methyl mercury in aquatic waters are not well understood. Inorganic and alkylated mercury has been studied in natural waters9-11, precipitation and the atmosphere12,13. We now report evidence of monomethyl and dimethyl mercury in the low-oxygen waters of the equatorial Pacific. The presence of these species has important implications for our understanding of the biogeochemical cycling of mercury in the marine environment. Although the source of monomethyl mercury in open-ocean fish is still unknown, our data show that a pathway exists for the accumulation of methylated mercury in marine pelagic fish.

  4. Dynamical variability in Saturn Equatorial Atmosphere

    Science.gov (United States)

    Sánchez-Lavega, A.; Pérez-Hoyos, S.; Hueso, R.; Rojas, J. F.; French, R. G.; Grupo Ciencias Planetarias Team

    2003-05-01

    Historical ground-based and recent HST observations show that Saturn's Equatorial Atmosphere is the region where the most intense large-scale dynamical variability took place at cloud level in the planet. Large-scale convective storms (nicknamed the ``Great White Spots") occurred in 1876, 1933 and 1990. The best studied case (the 1990 storm), produced a dramatic change in the cloud aspect in the years following the outburst of September 1990. Subsequently, a new large storm formed in 1994 and from 1996 to 2002 our HST observations showed periods of unusual cloud activity in the southern part of the Equator. This contrast with the aspect observed during the Voyager 1 and 2 encounters in 1980 and 1981 when the Equator was calm, except for some mid-scale plume-like features seen in 1981. Cloud-tracking of the features have revealed a dramatic slow down in the equatorial winds from maximum velocities of ˜ 475 m/s in 1980-1981 to ˜ 275 m/s during 1996-2002, as we have recently reported in Nature, Vol. 423, 623 (2003). We discuss the possibility that seasonal and ring-shadowing effects are involved in generating this activity and variability. Acknowledgements: This work was supported by the Spanish MCYT PNAYA 2000-0932. SPH acknowledges a PhD fellowship from the Spanish MECD and RH a post-doc fellowship from Gobierno Vasco. RGF was supported in part by NASA's Planetary Geology and Geophysics Program NAG5-10197 and STSCI Grant GO-08660.01A.

  5. Variation of slant path Ka/V-band rain attenuation over seven tropical locations in Nigeria using synthetic storm techniques

    Science.gov (United States)

    Ojo, J. S.; Adediji, A. T.; Mandeep, J. S.; Ismail, M.

    2016-04-01

    In this paper, rain characteristics and slant path rain attenuation at 30 and 40 GHz using synthetic storm techniques over seven tropical locations in Nigeria have been presented. The technique can be used to predict the local first-order statistical rain attenuation to mitigate the severe fade experienced at higher frequency bands by employing local rainfall rate statistics. Three years rain rate data at seven tropical and equatorial locations in Nigeria were utilized for the purpose of this work. The predicted statistics are in good agreement with those obtained from the propagation beacon measurement (EUTELSAT W4/W7 satellite-12.245 GHz) It could be observed that at 99.99 % link availability over these locations, the fade margin of higher dB (74 and 81 dB) are required at 30 and 40 GHz frequency bands, respectively. When diurnal variation was observed for four time intervals: 00:00-06:00, 06:00-12:00, 12:00-18:00, and 18:00-24:00, there is a variation of the fade margin over the hours of the day. The overall results will be needed for an acceptable planning that can effectively reduce the fade margin to a very low value for an optimum data communication over the studied locations.

  6. The importance of ionospheric measurements in Africa for understanding global equatorial electrodynmics

    Science.gov (United States)

    Basu, Santimay; Basu, Santimay; Basu, Sunanda

    The major driver of equatorial electrodynamics is the zonal electric field that develops under the action of the zonal neutral wind and is influenced by the east-west conductivity gradient at sunrise and sunset. During daytime, the eastward electric field at the dip equator coupled with the earth's magnetic field creates an upward drift of the plasma and transport to higher latitudes forming the equatorial anomaly in F-region plasma density with a minimum at the dip equator and maxima at 15o north and south dip latitudes. Further, at sunset, the east-west conductivity gradient causes an enhancement in the eastward electric field and sets off plasma instabilities to generate irregularities of electron density. The equatorial anomaly usually persisting beyond dusk, introduces a latitude variation in the magnitude of electron density deviation, thus causing a latitude variation of amplitude and phase scintillations. This pronounced latitude variation of F-region plasma density, the total electron content and scintillations impact greatly the operation of communication and navigation systems in this region. Such measurements in low latitude regions in the Asian and South American sectors show a great deal of day-to-day, seasonal-cum-longitudinal, magnetic disturbance and solar cycle variation. Currently, there is a gap in such long-term measurements at African longitudes. It is therefore extremely important to deploy arrays of instruments under the auspices of IHY and UNBSS Programs to obtain genuinely global measurement set to satisfy the needs of modern space-based communication and navigation systems and development of space weather ionosphere-thermosphere models for use in low latitude regions.

  7. African Trypanosomiasis

    Science.gov (United States)

    2011-06-01

    Histol. 1977;375:53- 70. 42. Poltera AA, Owor R, Cox JN. Pathological aspects of human African trypanosomiasis (HAT) in Uganda. A post - mortem survey of...nodular lesions , including anthrax or tick bite associated with Rickettsia conorii infection. The chancre is followed by a hemolymphatic stage, dur- ing...electrocardiograph- ic changes and, at times, terminal cardiac insufficiency.41 Pulmonary lesions specifically related to trypanosomiasis are not

  8. Genotype distribution of cervical human papillomavirus DNA in women with cervical lesions in Bioko, Equatorial Guinea

    Directory of Open Access Journals (Sweden)

    Carro-Campos Patricia

    2009-09-01

    Full Text Available Abstract Background The HVP vaccine is a useful tool for preventing cervical cancer. The purpose of this study is to determine the most frequent HPV genotypes in Equatorial Guinea in order to develop future vaccination strategies to apply in this country. Methods A campaign against cervical cancer was carried out in the area on a total of 1,680 women. 26 of the women, following cytological screening, were treated surgically with a loop electrosurgical excision procedure (LEEP. Cases were studied histologically and were genotyped from paraffin blocks by applying a commercial kit that recognized 35 HPV types. Results Cytological diagnoses included 17 HSIL, 1 LSIL, 5 ASC-H and 3 AGUS. Histological diagnosis resulted in 3 cases of microinvasive squamous cell carcinoma stage IA of FIGO, 9 CIN-3, 8 CIN-2, 2 CIN-1, 3 flat condylomas and mild dysplasia of the endocervical epithelium. Fifteen of twenty-five cases genotyped were positive for HPV (60%. HPV 16 and 33 were identified in four cases each, HPV 58 in two other cases, and HPV 18, 31, 52, and 82 in one case, with one HPV 16 and 58 coinfection. Conclusion The frequency of HPV types in the African area varies in comparison to other regions, particularly in Europe and USA. Vaccination against the five most common HPV types (16, 33, 58, 18, and 31 should be considered in the geographic region of West Africa and specifically in Equatorial Guinea.

  9. Are the equatorial electrojet and the Sq coupled systems? Transfer entropy approach

    Science.gov (United States)

    Vichare, Geeta; Bhaskar, Ankush; Ramesh, Durbha Sai

    2016-05-01

    Whether equatorial electrojet (EEJ) and solar quiet (Sq) are independent systems or not is a long standing question. Techniques such as correlation analysis, interpretation of the westward currents observed between EEJ and Sq focus, along with the simulation studies have been used to address this question, hitherto. In this article, we revisit this problem using a method based on transfer entropy that examines the relationship between day-to-day variability in EEJ and Sq during low solar activity period (year 2007-08). Magnetic field variations in the horizontal component from the geomagnetic observatory, Tirunelveli (TIR) from the Indian region are used as a proxy for EEJ currents. To represent variations of Sq current system, two stations outside the EEJ belt, Nagpur (NGP) and Jaipur (JAI) are analyzed. Our analyses clearly demonstrate that significant information is exchanged between EEJ and Sq variations, and hence they are in a cross-talk with each other, indicating EEJ and Sq are coupled systems. Variations of time scales less than 2 h appear at the equatorial station before Sq stations. Similar analyses carried out for the African sector also validate the above results.

  10. Obesity and African Americans

    Science.gov (United States)

    ... Data > Minority Population Profiles > Black/African American > Obesity Obesity and African Americans African American women have the ... ss6304.pdf [PDF | 3.38MB] HEALTH IMPACT OF OBESITY More than 80 percent of people with type ...

  11. Quiet time enhancements over African latitudes

    Science.gov (United States)

    Orford, Nicola; Katamzi, Zama; Buresova, Dalia

    2016-07-01

    F2 layer disturbances not related to geomagnetic activity are known as quiet time enhancements (QTEs). The phenomenon of QTEs has not yet been studied over African latitudes. We therefore explore the occurrence of QTEs over Africa in order to expand our knowledge on the behaviour of the ionosphere over this region. Several GPS stations in the middle to equatorial latitudes, during the solar minimum (2009) and near solar maximum (2013), are used. This data was examined for possible trends in variation with solar cycle, season and latitude as well as time of commencement of enhancements. Over the southern mid-latitude region of Africa we have observed that the QTEs are more likely to commence during the night in both solar minimum and maximum, however a slightly larger portion of daytime commencements during solar minimum than during solar maximum were observed. The total number of enhancements for the solar minimum period appears greater than during solar maximum. A seasonal trend is seen with the maximum number of enhancements occurring in summer during solar minimum and in winter during solar maximum. We explore further whether these trends are mirrored or different at low latitude/equatorial African regions.

  12. MULTIDIMENSIONAL MODELING OF CORONAL RAIN DYNAMICS

    Energy Technology Data Exchange (ETDEWEB)

    Fang, X.; Xia, C.; Keppens, R. [Centre for mathematical Plasma Astrophysics, Department of Mathematics, KU Leuven, B-3001 Leuven (Belgium)

    2013-07-10

    We present the first multidimensional, magnetohydrodynamic simulations that capture the initial formation and long-term sustainment of the enigmatic coronal rain phenomenon. We demonstrate how thermal instability can induce a spectacular display of in situ forming blob-like condensations which then start their intimate ballet on top of initially linear force-free arcades. Our magnetic arcades host a chromospheric, transition region, and coronal plasma. Following coronal rain dynamics for over 80 minutes of physical time, we collect enough statistics to quantify blob widths, lengths, velocity distributions, and other characteristics which directly match modern observational knowledge. Our virtual coronal rain displays the deformation of blobs into V-shaped features, interactions of blobs due to mostly pressure-mediated levitations, and gives the first views of blobs that evaporate in situ or are siphoned over the apex of the background arcade. Our simulations pave the way for systematic surveys of coronal rain showers in true multidimensional settings to connect parameterized heating prescriptions with rain statistics, ultimately allowing us to quantify the coronal heating input.

  13. RAINS: Regional Air Pollution Information and Simulation

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-12-01

    Only one computer model has ever been at the center of major international environmental negotiations. That model is RAINS. Twice it has been central to renegotiation of the Convention of Long-range Transboundary Air Pollution, the umbrella convention regarding air pollution across all Europe. It also underpins the European Union policy and directives on air pollution. Countries in Southeast Asia are turning to the model for help with their growing air pollution problems. RAINS will be used to determine emission ceilings for emissions of four key pollutants in EU countries - sulphur, ammonia, nitrogen oxides and volatile organic compounds. The same four pollutants are also the subject of a parallel negotiation in Geneva under the convention on Long-range Transboundary Air Pollution. The article and illustrations outline the model`s development and its structure in 1998, the historic role it has played in negotiations and some examples of its output. They highlight the central role of IIASA`s Transboundary Air Pollution project where a team of 12 works on the RAINS model and related issues. IIASA`s next goal is to develop a model of particulates pollution and incorporate it into RAINS. The information needed (such as particle sizes and chemical properties) and at what geographical scale must be identified to create an inventory of emissions suitable for RAINS modelling. 6 figs., 1 tab.

  14. Acid rain and its ecological consequences.

    Science.gov (United States)

    Singh, Anita; Agrawal, Madhoolika

    2008-01-01

    Acidification of rain-water is identified as one of the most serious environmental problems of transboundary nature. Acid rain is mainly a mixture of sulphuric and nitric acids depending upon the relative quantities of oxides of sulphur and nitrogen emissions. Due to the interaction of these acids with other constituents of the atmosphere, protons are released causing increase in the soil acidity Lowering of soil pH mobilizes and leaches away nutrient cations and increases availability of toxic heavy metals. Such changes in the soil chemical characteristics reduce the soil fertility which ultimately causes the negative impact on growth and productivity of forest trees and crop plants. Acidification of water bodies causes large scale negative impact on aquatic organisms including fishes. Acidification has some indirect effects on human health also. Acid rain affects each and every components of ecosystem. Acid rain also damages man-made materials and structures. By reducing the emission of the precursors of acid rain and to some extent by liming, the problem of acidification of terrestrial and aquatic ecosystem has been reduced during last two decades.

  15. Lidar Observation of Tropopause Ozone Profiles in the Equatorial Region

    Science.gov (United States)

    Shibata, Yasukuni; Nagasawa, Chikao; Abo, Makoto

    2016-06-01

    Tropospheric ozone in the tropics zone is significant in terms of the oxidizing efficiency and greenhouse effect. However, in the upper troposphere, the ozone budget in the tropics has not been fully understood yet because of the sparsity of the range-resolved observations of vertical ozone concentration profiles. A DIAL (differential absorption lidar) system for vertical ozone profiles have been installed in the equatorial tropopause region over Kototabang, Indonesia (100.3E, 0.2S). We have observed large ozone enhancement in the upper troposphere, altitude of 13 - 17 km, concurring with a zonal wind oscillation associated with the equatorial Kelvin wave around the tropopause at equatorial region.

  16. Equatorial Rossby Solitary Wave Under the External Forcing

    Institute of Scientific and Technical Information of China (English)

    FU Zun-Tao; LIU Shi-Kuo; LIU Shi-Da

    2005-01-01

    A simple shallow-water model with influence of external forcing on a β-plane is applied to investigate the nonlinear equatorial Rossby waves in a shear flow. By the perturbation method, the extended variable-coefficient KdV equation under an external forcing is derived for large amplitude equatorial Rossby wave in a shear flow. And then various periodic-like structures for these equatorial Rossby waves are obtained with the help of Jacobi elliptic functions.It is shown that the external forcing plays an important role in various periodic-like structures.

  17. Equatorial cloud level convection on Venus

    Science.gov (United States)

    Lee, Yeon Joo; Imamura, Takeshi; Sugiyama, Koichiro; Sato, Takao M.; Maejima, Yasumitsu

    2016-10-01

    In the equatorial region on Venus, a clear cloud top morphology difference depending on solar local time has been observed through UV images. Laminar flow shaped clouds are shown on the morning side, and convective-like cells on the afternoon side (Titov et al. 2012). Baker et al. (1998) suggested that deep convective motions in the low-to-middle cloud layers at the 40–60 km range can explain cellular shapes. Imamura et al. (2014), however argued that this cannot be a reason, as convection in the low-to-middle cloud layers can be suppressed near sub solar regions due to a stabilizing effect by strong solar heating. We suggest that the observed feature may be related to strong solar heating at local noon time (Lee et al. 2015). Horizontal uneven distribution of an unknown UV absorber and/or cloud top structure may trigger horizontal convection (Toigo et al. 1994). In order to examine these possibilities, we processed 1-D radiative transfer model calculations from surface to 100 km altitude (SHDOM, Evans 1998), which includes clouds at 48-71 km altitudes (Crisp et al. 1986). The results on the equatorial thermal cooling and solar heating profiles were employed in a 2D fluid dynamic model calculation (CReSS, Tsuboki and Sakakibara 2007). The calculation covered an altitude range of 40-80 km and a 100-km horizontal distance. We compared three conditions; an 'effective' global circulation condition that cancels out unbalanced net radiative energy at equator, a condition without such global circulation effect, and the last condition assumed horizontally inhomogeneous unknown UV absorber distribution. Our results show that the local time dependence of lower level cloud convection is consistent with Imamura et al.'s result, and suggest a possible cloud top level convection caused by locally unbalanced net energy and/or horizontally uneven solar heating. This may be related to the observed cloud morphology in UV images. The effective global circulation condition, however

  18. A novel rain removal technology based on video image

    Science.gov (United States)

    Liu, Shuo; Piao, Yan

    2016-11-01

    Due to the effect of bad weather conditions, it often conducts visual distortions on images for outdoor vision systems. Rain is one specific example of bad weather. Generally, rain streak is small and falls at high velocity. Traditional rain removal methods often cause blued visual effect. In addition, there is high time complexity. Moreover, some rain streaks are still in the de-rained image. Based on the characteristics of rain streak, a novel rain removal technology is proposed. The proposed method is not only removing the rain streak effectively, but also retaining much detail information. The experiments show that the proposed method outperform traditional rain removal methods. It can be widely used in intelligent traffic, civilian surveillance and national security so on.

  19. Multidimensional modeling of coronal rain dynamics

    CERN Document Server

    Fang, X; Keppens, R

    2013-01-01

    We present the first multidimensional, magnetohydrodynamic simulations which capture the initial formation and the long-term sustainment of the enigmatic coronal rain phenomenon. We demonstrate how thermal instability can induce a spectacular display of in-situ forming blob-like condensations which then start their intimate ballet on top of initially linear force-free arcades. Our magnetic arcades host chromospheric, transition region, and coronal plasma. Following coronal rain dynamics for over 80 minutes physical time, we collect enough statistics to quantify blob widths, lengths, velocity distributions, and other characteristics which directly match with modern observational knowledge. Our virtual coronal rain displays the deformation of blobs into $V$-shaped like features, interactions of blobs due to mostly pressure-mediated levitations, and gives the first views on blobs which evaporate in situ, or get siphoned over the apex of the background arcade. Our simulations pave the way for systematic surveys o...

  20. Propagating Characteristics of Pulsed Laser in Rain

    Directory of Open Access Journals (Sweden)

    Jing Guo

    2015-01-01

    Full Text Available To understand the performance of laser ranging system under the rain weather condition, we need to know the propagating characteristics of laser pulse in rain. In this paper, the absorption and attenuation coefficients were calculated based on the scattering theories in discrete stochastic media, and the propagating characteristics of laser pulse in rain were simulated and analyzed using Monte-Carlo method. Some simulation results were verified by experiments, and the simulation results are well matched with the experimental data, with the maximal deviation not less than 7.5%. The results indicated that the propagating laser beam would be attenuated and distorted due to the scattering and absorption of raindrops, and the energy attenuation and pulse shape distortion strongly depended on the laser pulse widths.

  1. Equatorial airglow depletions induced by thermospheric winds

    Energy Technology Data Exchange (ETDEWEB)

    Meriwether, J.W.; Biondi, M.A.; Anderson, D.N.

    1985-08-01

    Interferometric observations on the 630.0 nm nightglow brightness at the equatorial station at Arequipa, Peru (16.2 S, 71.4 W geographic, 3.2 S dip latitude) have revealed widespread areas of airglow depletion, with reductions in intensity as large as factors of 3 or 4. These depletions correlated closely with large increases of the equatorward (northward) wind and the 630.0 nm kinetic temperature. On occasion, the usually small meridional wind reached a velocity of 100 m/s near 22h LT lasting for 1 to 2 hours. The temperature increases of 100K or more existed only in the poleware (southward) direction. Comparisons with modeling calculations suggest that this effect results from an upward movement of the ionosphere along the inclined magnetic field lines, driven by the equatorward neutral wind. The airglow column integrated emission rate is consequently decreased by the slower rate of formation and subsequent dissociative recombination of molecular oxygen ions within the higher F-layer. We conclude that the transient period of equatorward wind is a result of the passage of the midnight pressure bulge. (Author)

  2. Equatorial airglow depletions induced by thermospheric winds

    Energy Technology Data Exchange (ETDEWEB)

    Meriwether J.W. Jr.; Biondi, M.A.; Anderson, D.N.

    1985-08-01

    Interferometric observations of the 630.0 nm nightglow brightness at the equatorial station of Arequipa. Peru (16.2/sup 0/S, 71.4/sup 0/W geographic, 3.2/sup 0/S dip latitude) have revealed widespread areas of airglow depletion, with reductions in intensity as large as factors of 3 or 4. These depletions correlated closely with large increases of the equatorward (northward) wind and the 630.0 nm kinetic temperature. On occasion, the usually small meridonal wind reached a velocity of 100 m/s near 22/sup h/ LT lasting for 1 or 2 hours. The temperature increases of 10 K or more existed only in the poleward (southward) direction. Comparisons with modeling calculations suggest that this effect results from an upward movement of the ionosphere along the inclined magnetic field lines, driven by the equatorward neutral wind. The airglow column integrated emission rate is consequently decreased by the slower rate of formation and subsequent dissociative recombination of molecular oxygen ions within the higher F-layer. We conclude that the transient period of equatorward wind is a result of the passage of the midnight pressure bulge.

  3. Observational features of equatorial coronal hole jets

    CERN Document Server

    Nistico', G; Patsourakos, S; Zimbardo, G

    2010-01-01

    Collimated ejections of plasma called "coronal hole jets" are commonly observed in polar coronal holes. However, such coronal jets are not only a specific features of polar coronal holes but they can also be found in coronal holes appearing at lower heliographic latitudes. In this paper we present some observations of "equatorial coronal hole jets" made up with data provided by the STEREO/SECCHI instruments during a period comprising March 2007 and December 2007. The jet events are selected by requiring at least some visibility in both COR1 and EUVI instruments. We report 15 jet events, and we discuss their main features. For one event, the uplift velocity has been determined as about 200 km/s, while the deceleration rate appears to be about 0.11 km/s2, less than solar gravity. The average jet visibility time is about 30 minutes, consistent with jet observed in polar regions. On the basis of the present dataset, we provisionally conclude that there are not substantial physical differences between polar and eq...

  4. Equatorial Kelvin waves: A UARS MLS view

    Energy Technology Data Exchange (ETDEWEB)

    Canziani, P.O.; Holton, J.R.; Fishbein, E.; Froidevaux, L.; Waters, J.W.

    1994-10-01

    Data from the Microwave Limb Sounder (MLS) instrument on the Upper Atmosphere Research Satellite (UARS) are used to compare two periods of Kelvin wave activity during different stages of the equatorial quasi-biennial oscillation. The analysis is carried out using an asynoptic mapping technique. A wide bandpass filter is used to isolate the frequency bands where Kelvin waves have been identified in previous studies. Time-height and time-latitude plots of the bandpassed data are used to identify Kelvin wave activity in the temperature and ozone fields. Frequency spectra of temperature and ozone amplitudes are constructed to further analyze the latitudinal and meridional distribution of Kelvin wave activity in zonal wavenumbers 1 and 2. The characteristics identified in these plots agree well with theoretical predictions and previous observations of middle atmosphere Kelvin waves. The time-height and time-latitude plots support the existence of Kelvin waves in discrete frequency bands; the slow, fast, and ultrafast Kelvin modes are all identified in the data. The characteristics of these modes do not vary much despite different mean flow conditions in the two periods examined. For the Kelvin wave-induced perturbations in ozone, the change from a transport-dominated regime below 10 hPa to a photochemically controlled regime above 10 hPa is clearly apparent in the height dependence of the phase difference between temperature and ozone.

  5. Equatorial electrojet in east Brazil longitudes

    Indian Academy of Sciences (India)

    R G Rastogi; H Chandra; K Yumuto

    2010-08-01

    This paper describes the morphology of the equatorial electrojet (EEJ) along 45°W longitude in east Brazil, where the ground magnetic (dip) equator is associated with the largest declination in the world. Daily range of the horizontal field ( ), as expected, was largest at the station in the chain closest to the dip equator, Sao Luiz (inclination −0.25°S). was largest positive at Eusebio (inclination 9.34°S) and largest negative at Belem (inclination 7.06°N); both near the fringe of EEJ belt. at Sao Luiz during the daytime was unexpectedly large negative in-spite of a small dip and also located south of the dip equator where should be positive. Center of EEJ was found to be shifted southward of the dip equator by about 1° in latitude. During southern summer, started decreasing from 00 h and reached a minimum value in the afternoon, an abnormal feature not discussed for any station so far. The mid-day value of the direction of vector was 22°-24°W compared to the declination of 19°–21°W in the region.

  6. The formation of an equatorial coronal hole

    Science.gov (United States)

    Yang, Liheng; Jiang, Yunchun; Zhang, Jun

    2010-02-01

    The formation of an equatorial coronal hole (CH) from 2006 January 9 to 12 was simultaneously observed by GOES-12/SXI, SOHO/EIT and SOHO/MDI instruments. The varieties of soft X-ray and EUV brightness, coronal temperature, and total magnetic flux in the CH were examined and compared with that of a quiet-sun (QS) region nearby. The following results are obtained. (1) A preexisting dark lane appeared on the location of the followed CH and was reinforced by three enhanced networks. (2) The CH gradually formed in about 81 hours and was predominated by positive magnetic flux. (3) During the formation, the soft X-ray and EUV brightness, coronal temperature, and total magnetic flux obviously decreased in the CH, but were almost no change in the QS region. The decrease of the total magnetic flux may be the result of magnetic reconnection between the open and closed magnetic lines, probably indicating the physical mechanism for the birth of the CH.

  7. Tilts of the Master Equatorial Tower

    Science.gov (United States)

    Ahlstrom, H. G., Jr.; Gawronski, W.; Girdner, D.; Noskoff, E.; Sommerville, J. N.

    2000-07-01

    At the center of the DSS-14 antenna, a tower reaches to the focal point of the antenna dish. The master equatorial (ME) instrument is located at the top of the tower. This instrument precisely (with an accuracy that exceeds that of the antenna) follows the commanded trajectory. Through the optical coupling, the antenna focal point follows the ME. One factor of the antenna pointing precision is the movement of the ME base, i.e., the top of the tower. For this reason, measurements of the ME tower tilts have been taken in order to quantify the tilts, to determine possible causes of the tilting, and to update the antenna pointing budget. They were conducted under three antenna operating modes: during tracking, slewing, and antenna stowing. The measurements indicate that the ME tower tilts introduce significant pointing errors that exceed the required 32-GHz (Ka-band) pointing precision (estimated as 0.8 mdeg for a 0.1-dB gain loss). Four different sources of tilt were identified and require verification.

  8. Geomagnetic storm and equatorial spread-F

    Directory of Open Access Journals (Sweden)

    F. Becker-Guedes

    2004-09-01

    Full Text Available In August 2000, a new ionospheric sounding station was established at Sao Jose dos Campos (23.2° S, 45.9° W; dip latitude 17.6° S, Brazil, by the University of Vale do Paraiba (UNIVAP. Another ionospheric sounding station was established at Palmas (10.2° S, 48.2° W; dip latitude 5.5° S, Brazil, in April 2002, by UNIVAP in collaboration with the Lutheran University Center of Palmas (CEULP, Lutheran University of Brazil (ULBRA. Both the stations are equipped with digital ionosonde of the type known as Canadian Advanced Digital Ionosonde (CADI. In order to study the effects of geomagnetic storms on equatorial spread-F, we present and discuss three case studies, two from the ionospheric sounding observations at Sao Jose dos Campos (September and November 2000 and one from the simultaneous ionospheric sounding observations at Sao Jose dos Campos and Palmas (July 2003. Salient features from these ionospheric observations are presented and discussed in this paper. It has been observed that sometimes (e.g. 4-5 November 2000 the geomagnetic storm acts as an inhibitor (high strong spread-F season, whereas at other times (e.g. 11-12 July 2003 they act as an initiator (low strong spread-F season, possibly due to corresponding changes in the quiet and disturbed drift patterns during different seasons.

  9. Multiple equilibria of cross-equatorial Inertial jets

    Institute of Scientific and Technical Information of China (English)

    CHAO JiPing; LIU Fei

    2007-01-01

    Based on the developed Anderson and Moore's theory about cross-equatorial inertial jets and a nonlinear equivalence shallow water model, new universal functions are determined by the characters of the vortical large-scale air flow (atmosphere) or ocean current (ocean) related to the jet, then the potential vorticity and energy conservation equations along the streamline in the cross-equatorial inertial jets can be obtained. Because the governing equations are nonlinear, some limited multiple equilibria of cross-equatorial inertial jets may exist. According to the character of large-scale air flow or ocean current outside the jets, the existent criterion for multiple eqnilibria in cross-equatorial inertial jets is discussed, and two examples for multiple equilibia of nonlinear governing equations are given.

  10. Multiple equilibria of cross-equatorial Inertial jets

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Based on the developed Anderson and Moore’s theory about cross-equatorial inertial jets and a nonlinear equivalence shallow water model, new universal functions are determined by the characters of the vortical large-scale air flow (atmosphere) or ocean current (ocean) related to the jet, then the potential vorticity and energy conservation equations along the streamline in the cross-equatorial in-ertial jets can be obtained. Because the governing equations are nonlinear, some limited multiple equi-libria of cross-equatorial inertial jets may exist. According to the character of large-scale air flow or ocean current outside the jets, the existent criterion for multiple eqnilibria in cross-equatorial inertial jets is discussed, and two examples for multiple equilibia of nonlinear governing equations are given.

  11. Modelling the development of mixing height in near equatorial region

    Energy Technology Data Exchange (ETDEWEB)

    Samah, A.A. [Univ. of Malaya, Air Pollution Research Unit, Kuala Lumpur (Malaysia)

    1997-10-01

    Most current air pollution models were developed for mid-latitude conditions and as such many of the empirical parameters used were based on observations taken in the mid-latitude boundary layer which is physically different from that of the equatorial boundary layer. In the equatorial boundary layer the Coriolis parameter f is small or zero and moisture plays a more important role in the control of stability and the surface energy balance. Therefore air pollution models such as the OMLMULTI or the ADMS which were basically developed for mid-latitude conditions must be applied with some caution and would need some adaptation to properly simulate the properties of equatorial boundary layer. This work elucidates some of the problems of modelling the evolution of mixing height in the equatorial region. The mixing height estimates were compared with routine observations taken during a severe air pollution episodes in Malaysia. (au)

  12. Eastern Equatorial Pacific Sea Level Pressure (1949-present)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This is one of the CPC?s Monthly Atmospheric and SST Indices. It contains standardized sea level pressure anomalies over the equatorial eastern Pacific region...

  13. Periodic equatorial water flows from a Hamiltonian perspective

    Science.gov (United States)

    Ionescu-Kruse, Delia; Martin, Calin Iulian

    2017-04-01

    The main result of this paper is a Hamiltonian formulation of the nonlinear governing equations for geophysical periodic stratified water flows in the equatorial f-plane approximation allowing for piecewise constant vorticity.

  14. Climate Prediction Center Equatorial Southern Oscillation Index (1949-present)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This is one of the CPC?s Monthly Atmospheric and SST Indices. It contains Equatorial Southern Oscillation Index (standardized sea level pressure differences between...

  15. On Irrotational Flows Beneath Periodic Traveling Equatorial Waves

    Science.gov (United States)

    Quirchmayr, Ronald

    2016-08-01

    We discuss some aspects of the velocity field and particle trajectories beneath periodic traveling equatorial surface waves over a flat bed in a flow with uniform underlying currents. The system under study consists of the governing equations for equatorial ocean waves within a non-inertial frame of reference, where Euler's equation of motion has to be suitably adjusted, in order to account for the influence of the earth's rotation.

  16. Republic of Equatorial Guinea; Staff Report 2006 Article IV Consultation

    OpenAIRE

    International Monetary Fund

    2006-01-01

    Equatorial Guinea’s macroeconomic performance in the recent period has been broadly satisfactory. Despite the macroeconomic environment, however, progress in alleviating poverty and meeting the MDGs has been slow. Executive Directors welcome the government’s intention to prepare a National Poverty Reduction Strategy. In the meantime, the budget process needs to be modified. The pegged exchange rate regime has served Equatorial Guinea well, providing an anchor to hold down inflation and a ...

  17. Meridional equatorial electrojet current in the American sector

    Directory of Open Access Journals (Sweden)

    R. G. Rastogi

    Full Text Available Huancayo is the only equatorial electrojet station where the daytime increase of horizontal geomagnetic field (H is associated with a simultaneous increase of eastward geomagnetic field (Y. It is shown that during the counter electrojet period when ∆H is negative, ∆Y also becomes negative. Thus, the diurnal variation of ∆Y at equatorial latitudes is suggested to be a constituent part of the equatorial electrojet current system. Solar flares are known to increase the H field at an equatorial station during normal electrojet conditions (nej. At Huancayo, situated north of the magnetic equator, the solar flare effect, during nej, consists of positive impulses in H and Y and negative impulse in Z field. During counter electrojet periods (cej, a solar flare produces a negative impulse in H and Y and a positive impulse in Z at Huancayo. It is concluded that both the zonal and meridional components of the equatorial electrojet in American longitudes, as in Indian longitudes, flows in the same, E region of the ionosphere.

    Key words. Geomagnetism and paleomagnetism (dynamo theories · Ionosphere (equatorial ionosphere; ionosphere disturbances

  18. Disdrometer and Tipping Bucket Rain Gauge Handbook

    Energy Technology Data Exchange (ETDEWEB)

    Bartholomew. MJ

    2009-12-01

    The Distromet disdrometer model RD-80 and NovaLynx tipping bucket rain gauge model 260-2500E-12 are two devices deployed a few meters apart to measure the character and amount of liquid precipitation. The main purpose of the disdrometer is to measure drop size distribution, which it does over 20 size classes from 0.3 mm to 5.4 mm. The data from both instruments can be used to determine rain rate. The disdrometer results can also be used to infer several properties including drop number density, radar reflectivity, liquid water content, and energy flux. Two coefficients, N0 and Λ, from an exponential fit between drop diameter and drop number density, are routinely calculated. Data are collected once a minute. The instruments make completely different kinds of measurements. Rain that falls on the disdrometer sensor moves a plunger on a vertical axis. The disdrometer transforms the plunger motion into electrical impulses whose strength is proportional to drop diameter. The rain gauge is the conventional tipping bucket type. Each tip collects an amount equivalent to 0.01 in. of water, and each tip is counted by a data acquisition system anchored by a Campbell CR1000 data logger.

  19. Acid Rain. Teacher's Guide. LHS GEMS.

    Science.gov (United States)

    Hocking, Colin; Barber, Jacqueline; Coonrod, Jan

    This teacher's guide presents a unit on acid rain and introduces hands-on activities for sixth through eighth grade students. In each unit, students act as real scientists and gather evidence by using science process skills such as observing, measuring and recording data, classifying, role playing, problem solving, critical thinking, synthesizing…

  20. Acid Rain Materials for Classroom Use.

    Science.gov (United States)

    Factor, Lance; Kooser, Robert G.

    This booklet contains three separate papers suitable for use in an advanced high school or college chemistry course. The first paper provides background information on acids and bases. The second paper provides additional background information, focusing on certain aspects of atmospheric chemistry as it relates to the acid rain problem. An attempt…

  1. Acid Rain: A Student's First Sourcebook.

    Science.gov (United States)

    Kyle, Beth Ann; And Others

    The purpose of this guide is to help students better understand the science, citizen action, and research issues that are part of the acid rain problem. The guide is designed for students in grades 4-8 and their teachers. Following an introduction, the first seven sections are informative in nature. They include: (1) "Observations about Acidity";…

  2. Eastward traverse of equatorial plasma plumes observed with the Equatorial Atmosphere Radar in Indonesia

    Directory of Open Access Journals (Sweden)

    S. Fukao

    2006-07-01

    Full Text Available The zonal structure of radar backscatter plumes associated with Equatorial Spread F (ESF, probably modulated by atmospheric gravity waves, has been investigated with the Equatorial Atmosphere Radar (EAR in West Sumatra, Indonesia (0.20° S, 100.32° E; dip latitude 10.1° S and the FM-CW ionospheric sounders on the same magnetic meridian as the EAR. The occurrence locations and zonal distances of the ESF plumes were determined with multi-beam observations with the EAR. The ESF plumes drifted eastward while keeping distances of several hundred to a thousand kilometers. Comparing the occurrence of the plumes and the F-layer uplift measured by the FM-CW sounders, plumes were initiated within the scanned area around sunset only, when the F-layer altitude rapidly increased. Therefore, the PreReversal Enhancement (PRE is considered as having a zonal variation with the scales mentioned above, and this variation causes day-to-day variability, which has been studied for a long time. Modulation of the underlying E-region conductivity by gravity waves, which causes inhomogeneous sporadic-E layers, for example, is a likely mechanism to determine the scale of the PRE.

  3. Eastward traverse of equatorial plasma plumes observed with the Equatorial Atmosphere Radar in Indonesia

    Science.gov (United States)

    Fukao, S.; Yokoyama, T.; Tayama, T.; Yamamoto, M.; Maruyama, T.; Saito, S.

    2006-07-01

    The zonal structure of radar backscatter plumes associated with Equatorial Spread F (ESF), probably modulated by atmospheric gravity waves, has been investigated with the Equatorial Atmosphere Radar (EAR) in West Sumatra, Indonesia (0.20° S, 100.32° E; dip latitude 10.1° S) and the FM-CW ionospheric sounders on the same magnetic meridian as the EAR. The occurrence locations and zonal distances of the ESF plumes were determined with multi-beam observations with the EAR. The ESF plumes drifted eastward while keeping distances of several hundred to a thousand kilometers. Comparing the occurrence of the plumes and the F-layer uplift measured by the FM-CW sounders, plumes were initiated within the scanned area around sunset only, when the F-layer altitude rapidly increased. Therefore, the PreReversal Enhancement (PRE) is considered as having a zonal variation with the scales mentioned above, and this variation causes day-to-day variability, which has been studied for a long time. Modulation of the underlying E-region conductivity by gravity waves, which causes inhomogeneous sporadic-E layers, for example, is a likely mechanism to determine the scale of the PRE.

  4. RELATIONSHIPS BETWEEN PRECEDING PACIFIC SEA SURFACE TEMPERATURES AND SUBTROPICAL HIGH INDEXES OF MAIN RAINING SEASONS

    Institute of Scientific and Technical Information of China (English)

    YAO Yu; YAN Hua-sheng

    2009-01-01

    With correlation analysis and factor analysis methods,the effects of preceding Pacific SSTs on subtropical high indexes of main raining seasons are discussed. The results of correlation analysis show that the effects of SSTs on five subtropical high indexes differ in seasons and regions. The variation of SSTs mostly affects the area and intensity indexes of the subtropical high,followed by the western ridge index,and the effect on the ridge line index is more remarkable than on the north boundary index. The results of factor analysis reveals that the first common thctor of SST of each season reflected mainly the inverse relation of SSTs variation between the central and eastern part of equatorial Pacific and the western Pacific,which correlates better with the subtropical high indexes in the main raining seasons than other common factors of SST. The analysis of interdecadal variation indicated that the variation of SSTs was conducive to the emergence of the La Ni(n)a event before the end of 1970s,such that in the summer the subtropical high is likely to be weaker and smaller and located eastward and northward. After the 1980s,the opposite characteristics prevailed.

  5. Neotectonics in the northern equatorial Brazilian margin

    Science.gov (United States)

    Rossetti, Dilce F.; Souza, Lena S. B.; Prado, Renato; Elis, Vagner R.

    2012-08-01

    An increasing volume of publications has addressed the role of tectonics in inland areas of northern Brazil during the Neogene and Quaternary, despite its location in a passive margin. Hence, northern South America plate in this time interval might have not been as passive as usually regarded. This proposal needs further support, particularly including field data. In this work, we applied an integrated approach to reveal tectonic structures in Miocene and late Quaternary strata in a coastal area of the Amazonas lowland. The investigation, undertaken in Marajó Island, mouth of the Amazonas River, consisted of shallow sub-surface geophysical data including vertical electric sounding and ground penetrating radar. These methods were combined with morphostructural analysis and sedimentological/stratigraphic data from shallow cores and a few outcrops. The results revealed two stratigraphic units, a lower one with Miocene age, and an upper one of Late Pleistocene-Holocene age. An abundance of faults and folds were recorded in the Miocene deposits and, to a minor extent, in overlying Late Pleistocene-Holocene strata. In addition to characterize these structures, we discuss their origin, considering three potential mechanisms: Andean tectonics, gravity tectonics related to sediment loading in the Amazon Fan, and rifting at the continental margin. Amongst these hypotheses, the most likely is that the faults and folds recorded in Marajó Island reflect tectonics associated with the history of continental rifting that gave rise to the South Atlantic Ocean. This study supports sediment deposition influenced by transpression and transtension associated with strike-slip divergence along the northern Equatorial Brazilian margin in the Miocene and Late Pleistocene-Holocene. This work records tectonic evidence only for the uppermost few ten of meters of this sedimentary succession. However, available geological data indicate a thickness of up to 6 km, which is remarkably thick for

  6. Effects of simulated acid rain on germination, seedling growth and oxidative metabolism of recalcitrant-seeded Trichilia dregeana grown in its natural seed bank.

    Science.gov (United States)

    Ramlall, Chandika; Varghese, Boby; Ramdhani, Syd; Pammenter, Norman W; Bhatt, Arvind; Berjak, Patricia; Sershen

    2015-01-01

    Increased air pollution in a number of developing African countries, together with the reports of vegetation damage typically associated with acid precipitation in commercial forests in South Africa, has raised concerns over the potential impacts of acid rain on natural vegetation in these countries. Recalcitrant (i.e. desiccation sensitive) seeds of many indigenous African species, e.g. must germinate shortly after shedding and hence, may not be able to avoid exposure to acid rain in polluted areas. This study investigated the effects of simulated acid rain (rainwater with pH adjusted to pH 3.0 and 4.5 with 70:30, H2 SO4 :HNO3 ) on germination, seedling growth and oxidative metabolism in a recalcitrant-seeded African tree species Trichilia dregeana Sond., growing in its natural seed bank. The results suggest that acid rain did not compromise T. dregeana seed germination and seedling establishment significantly, relative to the control (non-acidified rainwater). However, pH 3.0 treated seedlings exhibited signs of stress typically associated with acid rain: leaf tip necrosis, abnormal bilobed leaf tips, leaf necrotic spots and chlorosis, reduced leaf chlorophyll concentration, increased stomatal density and indications of oxidative stress. This may explain why total and root biomass of pH 3.0 treated seedlings were significantly lower than the control. Acid rain also induced changes in the species composition and relative abundance of the different life forms emerging from T. dregeana's natural seed bank and in this way could indirectly impact on T. dregeana seedling establishment success.

  7. Urban Water-Quality Management. Rain Garden Plants

    OpenAIRE

    French, Sue (Sue C.); Fox, Laurie; Andruczyk, Mike; Gilland, Traci; Swanson, Lynette

    2009-01-01

    A rain garden is a landscaped area specially designed to collect rainfall and storm-water runoff. The plants and soil in the rain garden clean pollutants from the water as it seeps into the ground and evaporates back into the atmosphere. For a rain garden to work, plants must be selected, installed, and maintained properly.

  8. 40 CFR 76.3 - General Acid Rain Program provisions.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 16 2010-07-01 2010-07-01 false General Acid Rain Program provisions. 76.3 Section 76.3 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) ACID RAIN NITROGEN OXIDES EMISSION REDUCTION PROGRAM § 76.3 General Acid Rain Program...

  9. Biomass and carbon dynamics of a tropical mountain rain forest in China

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Biometric inventories for 25 years,from 1983 to 2005,indicated that the Jianfengling tropical mountain rain forest in Hainan,China,was either a source or a modest sink of carbon.Overall,this forest was a small carbon sink with an accumulation rate of(0.56±0.22) Mg C ha-1yr-1,integrated from the long-term measurement data of two plots(P9201 and P8302).These findings were similar to those for African and American rain forests((0.62±0.23) Mg C ha-1yr-1).The carbon density varied between(201.43±29.38) Mg C ha-1 and(229.16±39.2) Mg C ha-1,and averaged(214.17±32.42) Mg C ha-1 for plot P9201.Plot P8302,however,varied between(223.95±45.92) Mg C ha-1 and(254.85±48.86) Mg C ha-1,and averaged(243.35±47.64) Mg C ha-1.Quadratic relationships were found between the strength of carbon sequestration and heavy rainstorms and dry months.Precipitation and evapotranspiration are two major factors controlling carbon sequestration in the tropical mountain rain forest.

  10. Does a ruderal strategy dominate the endemic flora of the West African forests?

    NARCIS (Netherlands)

    Holmgren, M.; Poorter, L.

    2007-01-01

    Aim To understand the distribution pattern of endemic plant species in West African rain forests, one of the global priority areas for biodiversity conservation. Location Upper Guinean forests, West Africa (Senegal, Guinea-Bissau, Guinea, Sierra Leone, Liberia, Côte d'Ivoire, Ghana and Togo). Method

  11. Research on the Propagation Acting of the Equatorial Planetary Waves on the Western Equatorial Pacific Warm Pool Heat

    Institute of Scientific and Technical Information of China (English)

    Shi Qiang; Xu Jianping; Zhu Bokang

    2003-01-01

    Based on the long-term buoy data from the Tropical Atmosphere Ocean ( TAO ) array during the TOGA ( Tropical Ocean and Global Atmosphere) Program (1980-1996), the propagation acting of the Equatorial planetary waves on the Western Equatorial Pacific warm pool heat is analyzed. Results show that the zonal heat transmission in the Western Equatorial Pacific takes palace mainly in the subsurface water and spreads eastwards along the thermocline; while the seasonal westward-spreading heat change structure occurs in the mixed layers in the middle and western Pacific. The standing-form transmission in the western Pacific appears in the thermocline layer, while in the eastern pacific, it exists in the mixed layer as well as in the thermocline layer. The standing-form and eastward-spreading sign of zonal heat transmitting in the upper water is predominant and strong, and the westward sign is weak.The component force of Kelvin Equatorial wave pressure runs through the western and eastern Equatorial pacific, and transmits heat energy eastwards. And the heat transmitted by zonal current component occurs mostly in the western Pacific; The heat transmitted by the component force of Rossby wave pressure mainly appears in the eastern and middle areas of the Pacific, while the zonal current component transmitting occurs mainly in the western Pacific; Mixed-Rossby gravity wave's action on the zonal current is stronger than that of the thermocline layer. In the mean state, the standing wave model of Equatorial Pacific up layer ocean temperature confines the transport of western Pacific warm pool heat to the eastern Pacific. Under abnormal conditions, the standing wave model of Equatorial Pacific up layer ocean temperature weakens, the eastwardly transmitting model enhances, and subsequently the El Ni n o event occurs.

  12. Equatorial particle precipitation during magnetic storms and relationship to equatorial thermospheric heating

    Energy Technology Data Exchange (ETDEWEB)

    Tinsley, B.A.; Sahai, Y.; Biondi, M.A.; Meriwether J.W. Jr.

    1988-01-01

    We compare optical observations of ring current particle precipitation from a near equatorial site in Brazil with variations in the AE and Dst indices. Precipitation occurs during ring current injection when AE is large, but for AE large without ring current injection, little precipitation is seen. Comparisons are also made with 630-nm observations of thermospheric heating made simultaneously in Peru. The thermospheric temperatures have been corrected for instrumental drift and temperature enhancements of several hundred kelvins are present. It is not possible to associate clearly the heating with direct precipitation nor in the short term with transport of heat from higher latitudes. On a longer time scale it is likely that both mid-latitude ring current sources and high-latitude Joule heating sources are involved. copyright American Geophysical Union 1988

  13. Pollution problem: acid rain and beekeeping

    Energy Technology Data Exchange (ETDEWEB)

    Hayes, B.

    1979-11-01

    Some of the problems caused by acid rain are presented with emphasis on the effects on bees, especially in the Northeast. Scientists believe that rain east of the Mississippi is below 5.6 and average Northeastern rainfall is now down to pH 4. Trace minerals are being leached out of the soils and nectar that lacks calcium is being passed by when the bees forage. The first plants to show the effects will be the wild varieties of the legumes, such as clover. This leaves only plants on the extreme end of the acid scale such as the blueberry for bee forage. This leads to the side effect of the movement of calcium in nectar which will be restricted due to a lack of calcium-lime.

  14. Heart Disease and African Americans

    Science.gov (United States)

    ... Minority Population Profiles > Black/African American > Heart Disease Heart Disease and African Americans Although African American adults are ... were 30 percent more likely to die from heart disease than non-Hispanic whites. African American women are ...

  15. Acid rain in Europe and the United States: an update

    Energy Technology Data Exchange (ETDEWEB)

    Fredric C. Menz; Hans M. Seip [Clarkson University, Potsdam, NY (US). Bertrand Snell Hall, School of Business

    2004-08-01

    This paper discusses the evolution of science and policies to control acid rain in Europe and the United States over the past several decades. Acid rain gained prominence in the late 1960s because of its perceived effects on ecosystem integrity. Extensive research efforts in both Europe and the United States, however, have concluded that the effects of acid rain - at least those on terrestrial ecosystems - were less serious than originally believed. More recently, interest in controlling acid rain precursors stems primarily from health concerns, particularly their effects in the form of fine particulate matter. The paper discusses the emergence of acid rain as an environmental concern, scientific evidence about the effects of acidic deposition on natural ecosystems, US and European acid rain control policies, studies of the costs and benefits of reducing acid rain, and different policy contexts in Europe and the United States.

  16. Rain Sensor with Stacked Light Waveguide Having Tilted Air Gap

    Directory of Open Access Journals (Sweden)

    Kyoo Nam Choi

    2014-01-01

    Full Text Available Vehicle sensor to detect rain drop on and above waveguide utilizing light deflection and scattering was realized, keeping wide sensing coverage and sensitivity to detect mist accumulation. Proposed sensor structure under stacked light wave guide consisted of light blocking fixture surrounding photodetector and adjacent light source. Tilted air gap between stacked light waveguide and light blocking fixture played major role to increase sensitivity and to enhance linearity. This sensor structure eliminated complex collimating optics, while keeping wide sensing coverage using simple geometry. Detection algorithm based on time-to-intensity transformation process was used to convert raining intensity into countable raining process. Experimental result inside simulated rain chamber showed distinct different response between light rain and normal rain. Application as automobile rain sensor is expected.

  17. Chemical properties of rain events during the AMMA campaign: an evidence of dust and biogenic influence in the convective systems

    Directory of Open Access Journals (Sweden)

    K. Desboeufs

    2010-06-01

    Full Text Available This paper documents the chemical composition of 7 rain events associated with mesoscale convective systems sampled at the supersite of Banizoumbou, Niger, during the first special observation periods (June–July 2006 of the African Monsoon Multidisciplinary Analyses (AMMA experiment. Time-resolved rain sampling was performed in order to discriminate the local dust scavenged at the beginning of rain event from the aerosol particles incorporated in the cloud at the end of the rain. The total elemental composition is dominated by Al, Si, Fe and Ca, indicating a high influence of dust and limited marine or anthropogenic contribution. After the aerosol wash-out, the elemental concentrations normalized to Al and the microscopic observations of diatoms, a tracer of the Bodélé depression, both indicate that the total elemental composition of rainwater is controlled by dust originating from North-Eastern Saharan sources and probably incorporated in the convective cloud from the Harmattan layer. The low variability of the rain composition over the measurement period indicates a regional and temporal homogeneity of dust composition in the Harmattan layer. In the dissolved phase, the dominant anions are nitrate (NO3, sulphate (SO42− and chloride (Cl. However, between June and July we observe an increasing contribution of the organic anions (formate, acetate, oxalate associated with biogenic emissions to the total ion composition. These results confirm the large influence of biogenic emissions on the rain composition over Sahel during the wet season. The paper concludes on the capacity of mesoscale convective systems to carry simultaneously dust and biogenic compounds originating from different locations and depose them jointly. It also discusses the potential biogeochemical impact of such a phenomenon.

  18. Formation of Jets and Equatorial Superrotation on Jupiter

    CERN Document Server

    Schneider, Tapio

    2008-01-01

    The zonal flow in Jupiter's upper troposphere is organized into alternating retrograde and prograde jets, with a prograde (superrotating) jet at the equator. Existing models posit as the driver of the flow either differential radiative heating of the atmosphere or intrinsic heat fluxes emanating from the deep interior; however, they do not reproduce all large-scale features of Jupiter's jets and thermal structure. Here it is shown that the difficulties in accounting for Jupiter's jets and thermal structure resolve if the effects of differential radiative heating and intrinsic heat fluxes are considered together, and if upper-tropospheric dynamics are linked to a magnetohydrodynamic (MHD) drag that acts deep in the atmosphere. Baroclinic eddies generated by differential radiative heating can account for the off-equatorial jets; meridionally propagating equatorial Rossby waves generated by intrinsic convective heat fluxes can account for the equatorial superrotation. The zonal flow extends deeply into the atmos...

  19. Occurrence of Equatorial Plasma Bubbles during Intense Magnetic Storms

    Directory of Open Access Journals (Sweden)

    Chao-Song Huang

    2011-01-01

    Full Text Available An important issue in low-latitude ionospheric space weather is how magnetic storms affect the generation of equatorial plasma bubbles. In this study, we present the measurements of the ion density and velocity in the evening equatorial ionosphere by the Defense Meteorological Satellite Program (DMSP satellites during 22 intense magnetic storms. The DMSP measurements show that deep ion density depletions (plasma bubbles are generated after the interplanetary magnetic field (IMF turns southward. The time delay between the IMF southward turning and the first DMSP detection of plasma depletions decreases with the minimum value of the IMF Bz, the maximum value of the interplanetary electric field (IEF Ey, and the magnitude of the Dst index. The results of this study provide strong evidence that penetration electric field associated with southward IMF during the main phase of magnetic storms increases the generation of equatorial plasma bubbles in the evening sector.

  20. Bistability between equatorial and axial dipoles during magnetic field reversals

    CERN Document Server

    Gissinger, Christophe; Schrinner, Martin; Dormy, Emmanuel

    2012-01-01

    Numerical simulations of the geodynamo in presence of an heterogeneous heating are presented. We study the dynamics and the structure of the magnetic field when the equatorial symmetry of the flow is broken. If the symmetry breaking is sufficiently strong, the m = 0 axial dipolar field is replaced by an hemispherical magnetic field, dominated by an oscillating m = 1 magnetic field. Moreover, for moderate symmetry breaking, a bistability between the axial and the equatorial dipole is observed. In this bistable regime, the axial magnetic field exhibits chaotic switches of its polarity, involving the equatorial dipole during the transition period. This new scenario for magnetic field reversals is discussed within the framework of the Earth's dynamo.

  1. Bistability between equatorial and axial dipoles during magnetic field reversals.

    Science.gov (United States)

    Gissinger, Christophe; Petitdemange, Ludovic; Schrinner, Martin; Dormy, Emmanuel

    2012-06-08

    Numerical simulations of the geodynamo in the presence of heterogeneous heating are presented. We study the dynamics and the structure of the magnetic field when the equatorial symmetry of the flow is broken. If the symmetry breaking is sufficiently strong, the m=0 axial dipolar field is replaced by a hemispherical magnetic field, dominated by an oscillating m=1 magnetic field. Moreover, for moderate symmetry breaking, a bistability between the axial and the equatorial dipole is observed. In this bistable regime, the axial magnetic field exhibits chaotic switches of its polarity, involving the equatorial dipole during the transition period. This new scenario for magnetic field reversals is discussed within the framework of Earth's dynamo.

  2. Meteorology of Jupiter's Equatorial Hot Spots and Plumes from Cassini

    CERN Document Server

    Choi, David S; Vasavada, Ashwin R; Simon-Miller, Amy A

    2013-01-01

    We present an updated analysis of Jupiter's equatorial meteorology from Cassini observations. For two months preceding the spacecraft's closest approach, the Imaging Science Subsystem (ISS) onboard regularly imaged the atmosphere. We created time-lapse movies from this period in order to analyze the dynamics of equatorial hot spots and their interactions with adjacent latitudes. Hot spots are quasi-stable, rectangular dark areas on visible-wavelength images, with defined eastern edges that sharply contrast with surrounding clouds, but diffuse western edges serving as nebulous boundaries with adjacent equatorial plumes. Hot spots exhibit significant variations in size and shape over timescales of days and weeks. Some of these changes correspond with passing vortex systems from adjacent latitudes interacting with hot spots. Strong anticyclonic gyres present to the south and southeast of the dark areas appear to circulate into hot spots. Impressive, bright white plumes occupy spaces in between hot spots. Compact...

  3. Tropospheric ozone over Equatorial Africa: regional aspects from the MOZAIC data

    Directory of Open Access Journals (Sweden)

    B. Sauvage

    2005-01-01

    Full Text Available We analyze ozone observations recorded over Equatorial Africa between April 1997 and March 2003 by the MOZAIC programme, providing the first ozone climatology deriving from continental in-situ data over this region. Three-dimensional streamlines strongly suggests connections between the characteristics of the ozone monthly mean vertical profiles, the most persistent circulation patterns in the troposphere over Equatorial Africa (on a monthly basis such as the Harmattan, the African Easterly Jet, the Trades and the regions of ozone precursors emissions by biomass burning. During the biomass burning season in each hemisphere, the lower troposphere exhibits layers of enhanced ozone (i.e. 70 ppbv over the coast of Gulf of Guinea in December-February and 85 ppbv over Congo in June-August. The characteristics of the ozone monthly mean vertical profiles are clearly connected to the regional flow regime determined by seasonal dynamic forcing. The mean ozone profile over the coast of Gulf of Guinea in the burning season is characterized by systematically high ozone below 650hPa ; these are due to the transport by the Harmattan and the AEJ of the pollutants originating from upwind fires. The confinement of high ozone to the lower troposphere is due to the high stability of the Harmattan and the blocking Saharan anticyclone which prevents efficient vertical mixing. In contrast, ozone enhancements observed over Central Africa during the local dry season (June-August are not only found in the lower troposphere but throughout the troposphere. Moreover, this study highlights a connection between the regions of the coast of Gulf of Guinea and regions of Congo to the south that appears on a semi annual basis. Vertical profiles in wet-season regions exhibit ozone enhancements in the lower troposphere due to biomass burning products transport from fires situated in the opposite dry-season hemisphere.

  4. Rain-Flow and Reverse Rain-Flow Counting Method for the Compilation of Fatigue Load Spectrum

    Institute of Scientific and Technical Information of China (English)

    宋玉普; 李朝阳; 王立成

    2001-01-01

    The rain-flow counting method is widely used to compile the fatigue load spectrum. The second stage counting of the rain-flow method is a troublesome process. In order to overcome this drawback, the rain-flow and reverse rain-flow counting method is proposed in this paper. In this counting method, the rule for counting of the rain-flow method is modified, so that the sequence of load-time need not be adjusted. This is a valid and useful method to count cycles and compile the load spectrum and it can be widely used in ocean engineering.

  5. Depression and African Americans

    Science.gov (United States)

    ... You are here Home » Depression And African Americans Depression And African Americans Not “Just the Blues” Clinical ... or spiritual communities. Commonly Asked Questions about Clinical Depression How do I get help for clinical depression? ...

  6. Longitudinal Variation and Waves in Jupiter's South Equatorial Wind Jet

    Science.gov (United States)

    Simon-Miller, A. A.; Rogers, John H.; Gierasch, Peter J.; Choi, David; Allison, Michael; Adamoli, Gianluigi; Mettig, Hans-Joerg

    2012-01-01

    We have conducted a detailed study of the cloud features in the strong southern equatorial wind jet near 7.5 S planetographic latitude. To understand the apparent variations in average zonal wind jet velocity at this latitude [e.g.. 1,2,3], we have searched for variations iIi both feature latitude and velocity with longitude and time. In particular, we focused on the repetitive chevron-shaped dark spots visible on most dates and the more transient large anticyclonic system known as the South Equatorial Disturbance (SED). These small dark spots are interpreted as cloud holes, and are often used as material tracers of the wind field.

  7. Vertical profiles of ozone between 0 and 400 meters in and above the African equatorial forest

    Science.gov (United States)

    Cros, B.; Fontan, J.; Minga, A.; Helas, G.; Nganga, D.; Delmas, R.; Chapuis, A.; Benech, B.; Druilhet, A.; Andreae, M. O.

    1992-08-01

    Results are presented of measurements of ozone concentrations in the northern Congo, near Impfondo, as part of the DECAFE experiment in February 1988, during the dry season. The measurements were carried out simultaneously at ground level in a large clearing, inside the forest between 0 and 30 m, and above the forest with a captive balloon flying up to 400 m. The results presented are compared with the data obtained in the Mayombe forest in southern Congo, near Dimonika, in June 1988, during the dry season. For both northern and southern forested areas the ozone concentrations measured at ground level in a large clearing exhibit daily variations with maxima in the afternoon ranging between 10 and 30 parts per billion by volume (ppbv) and minima at the end of the night between 4 and 15 ppbv. The characteristics of each surface ozone cycle are analyzed. Inside the forest, ozone concentrations are found very low near the ground, and rarely exceed 15 ppbv above the canopy. The relationships among the vertical profiles of ozone, temperature, and water vapor are discussed.

  8. The relationship between the Guinea Highlands and the West African offshore rainfall maximum

    Science.gov (United States)

    Hamilton, H. L.; Young, G. S.; Evans, J. L.; Fuentes, J. D.; Núñez Ocasio, K. M.

    2017-01-01

    Satellite rainfall estimates reveal a consistent rainfall maximum off the West African coast during the monsoon season. An analysis of 16 years of rainfall in the monsoon season is conducted to explore the drivers of such copious amounts of rainfall. Composites of daily rainfall and midlevel meridional winds centered on the days with maximum rainfall show that the day with the heaviest rainfall follows the strongest midlevel northerlies but coincides with peak low-level moisture convergence. Rain type composites show that convective rain dominates the study region. The dominant contribution to the offshore rainfall maximum is convective development driven by the enhancement of upslope winds near the Guinea Highlands. The enhancement in the upslope flow is closely related to African easterly waves propagating off the continent that generate low-level cyclonic vorticity and convergence. Numerical simulations reproduce the observed rainfall maximum and indicate that it weakens if the African topography is reduced.

  9. Linguistic Imperialism: African Perspectives.

    Science.gov (United States)

    Phillipson, Robert

    1996-01-01

    Responds to an article on aspects of African language policy and discusses the following issues: multilingualism and monolingualism, proposed changes in language policy from the Organization for African Unity and South African initiatives, the language of literature, bilingual education, and whose interests English-language teaching is serving.…

  10. Upper ocean circulation modulation by phytoplankton concentration in the Equatorial Pacific and the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Nakamoto, S.; PrasannaKumar, S.; Oberhuber, J.M.; Sammarco, P.; Muneyama, K.; Sato, T.; AjoyKumar, A.; Frouin, R.

    brings nutrient-rich subsurface waters to the euphotic zone, thus the ocean currents supports perinnial phytoplankton bloom. The phytoplankton inhibits downward solar radiation penetration in the equatorial Pacific, resulting in cross equatorial density...

  11. A biweekly mode in the equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Sengupta, D.; Senan, R.; Murty, V.S.N.; Fernando, V.

    propagating biweekly waves with zonal wavelength in the range 2100 to 6100 km. An ocean model forced by high-resolution scatterometer wind stress is used to show that the observed biweekly variability is due to equatorially trapped mixed Rossby-gravity waves...

  12. The equatorial electrojet current modelling from SWARM satellite data

    Science.gov (United States)

    Benaissa, Mahfoud

    2016-07-01

    Equatorial ElectroJet (EEJ) is an intense eastward electric current circulating in the ionospheric magnetic equator band between 100 and 130 km of altitude in E region. These currents vary by day, by season, by solar activity, and also with the main magnetic field of internal origin. The irregularity of the ionosphere has a major impact on the performance of communication systems and navigation (GPS), industry.... Then it becomes necessary study the characteristics of EEJ. In this paper, we present a study of the equatorial electrojet (EEJ) phenomenon along one year (2014) period. In addition, the satellite data used in this study are obtained with SWARM satellite scalar magnetometer data respecting magnetically quiet days with KP < 2. In this paper, we process to separate and extract the electrojet intensity signal from other recorded signal-sources interfering with the main signal and reduce considerably the signal to noise ratio during the SWARM measurements. This pre-processing step allows removing all external contributions in regard to EEJ intensity value. Key words: Ionosphere (Equatorial ionosphere; Electric fields and currents; Equatorial electrojet (EEJ)); SWARM.

  13. Equatorial ionospheric electrodynamic perturbations during Southern Hemisphere stratospheric warming events

    DEFF Research Database (Denmark)

    Olson, M. E.; Fejer, B. G.; Stolle, Claudia;

    2013-01-01

    We use ground-based and satellite measurements to examine, for the first time, the characteristics of equatorial electrodynamic perturbations measured during the 2002 major and 2010 minor Southern Hemisphere sudden stratospheric warming (SSW) events. Our data suggest the occurrence of enhanced qu...

  14. Clean advice for oily money : Consulting for Equatorial Guinea

    NARCIS (Netherlands)

    Lachotzki, F.W.I.; Karssing, E.D.

    2011-01-01

    Equatorial Guinea is one of the most extraordinary countries in the world, if also one of the most obscure. Its tremendous yearly revenue from the oil concessions it grants in its Gulf of Guinea territorial waters is little known, but so too is its abysmal record on human rights. The deep-rooted cor

  15. Climate regulation of fire emissions and deforestation in equatorial Asia

    NARCIS (Netherlands)

    van der Werf, G. R.; Dempewolf, J.; Trigg, S. N.; Randerson, J. T.; Kasibhatla, P. S.; Giglio, L.; Murdiyarso, D.; Peters, W.; Morton, D. C.; Collatz, G. J.; Dolman, A. J.; Defries, R. S.

    2008-01-01

    Drainage of peatlands and deforestation have led to large-scale fires in equatorial Asia, affecting regional air quality and global concentrations of greenhouse gases. Here we used several sources of satellite data with biogeochemical and atmospheric modeling to better understand and constrain fire

  16. Exact Nonlinear Internal Equatorial Waves in the f-plane

    Science.gov (United States)

    Hsu, Hung-Chu

    2016-07-01

    We present an explicit exact solution of the nonlinear governing equations for internal geophysical water waves propagating westward above the thermocline in the f-plane approximation near the equator. Moreover, the mass transport velocity induced by this internal equatorial wave is eastward and a westward current occurs in the transition zone between the great depth where the water is still and the thermocline.

  17. Understanding the equatorial ocean : theoretical and observational studies

    NARCIS (Netherlands)

    Rabitti, A.

    2016-01-01

    By means of a variety of approaches, the present study points out the challenges in understanding equatorial ocean dynamics (±2.5º). Standard theory, in fact, fails in accurately describing such a big portion of our ocean. This is mainly because at the equator rotation and density stratification com

  18. Relation Between Equatorial Oceanic Activities and LOD Changes

    Institute of Scientific and Technical Information of China (English)

    郑大伟; 陈刚

    1994-01-01

    The time series of the length of day (LOD) and the observational Pacific sea level during l962.0-1990.0 are used to study the relation between Earth rotation and equatorial oceanic activities.The results show that (i) the sea level is apparently rising at an average rate of about 1.75±.01mm/a during the past 30 years,(ii) there are large-scale eastward and westward water motions in the upper equatorial Pacific zone,which,according to the dynamical analysis of the angular momentum of the large-scale sea water motion in Pacific Ocean related to the Earth rotation axis accounts for about 30% of the change in ititerannual Eatlh rotation rate; (iii) the interannual changes in Earth rotation also cause changes in the distribution of the water mass in equatorial Pacific,and affect the formation of ENSO events.Based on these results,we give a new model for the interaction between equatorial ocean and Earth rotation.

  19. How mosquitoes fly in the rain

    Science.gov (United States)

    Dickerson, Andrew; Shankles, Peter; Madhavan, Nihar; Hu, David

    2011-11-01

    Mosquitoes thrive during rainfall and high humidity. If raindrops are 50 times heavier than mosquitoes, how do mosquitoes fly in the rain? In this combined experimental and theoretical study, we measure the impact force between a falling drop and a free-flying mosquito. High-speed videography of mosquitoes and custom-built mimics reveals a mosquito's low inertia renders it impervious to falling drops. Drops do not splash on mosquitoes, but simply push past them allowing a mosquito to continue on its flight path undeterred. We rationalize the force imparted using scaling relations based on the time of rebound between a falling drop and a free body of significantly less mass.

  20. TESTING NONLINEAR INFLATION CONVERGENCE FOR THE CENTRAL AFRICAN ECONOMIC AND MONETARY COMMUNITY

    Directory of Open Access Journals (Sweden)

    Emmanuel Anoruo

    2014-01-01

    Full Text Available This paper uses nonlinear unit root testing procedures to examine the issue of inflation convergence for the Central African Economic and Monetary Community (CEMAC member states including Cameron, Central African Republic, Chad, Equatorial Guinea, Gabon and the Republic of Congo. The results from nonlinear STAR unit root tests suggest that inflation differentials for the sample countries are nonlinear and mean reverting processes. These results provide evidence of inflation convergence among countries within CEMAC. The finding of inflation convergence indicates the feasibility of a common monetary policy and/or inflation targeting regime within CEMAC.

  1. EFFECTS OF RAIN ATTENUATION ON SATELLITE COMMUNICATION LINK

    Directory of Open Access Journals (Sweden)

    G. N. Ezeh

    2014-06-01

    Full Text Available Rain attenuation is a major challenge to microwave satellite communication especially at frequencies above 10 GHz, causing unavailability of signals most of the time. Rain attenuation predictions have become one of the vital considerations while setting up a satellite communication link. In this study, rain attenuation models, cumulative distribution curves and other analytical tools for successful prediction of rain attenuation are presented. A three year Rain rate data was obtained from the Nigeria Meteorological Agency (NIMET database in addition to experimental data. Of the three prediction models used in the study, Ajayi model gave the range of values closest to the experimental data. A correctional factor was determined as 1.0988 and used to modify the Ajayi model. This modification to Ajayi’s model enabled its rain attenuation values conform more closely to the experimental result.

  2. Post-midnight occurrence of equatorial plasma bubbles

    Science.gov (United States)

    Ajith, K. K.; Otsuka, Yuichi; Yamamoto, Mamoru; Yokoyama, Tatsuhiro; Tulasiram, S.

    2016-07-01

    The equatorial plasma bubbles (EPBs)/equatorial spread F (ESF) irregularities are an important topic of space weather interest because of their impact on transionospheric radio communications, satellite-based navigation and augmentation systems. This local plasma depleted structures develop at the bottom side F layer through Rayleigh-Taylor instability and rapidly grow to topside ionosphere via polarization electric fields within them. The steep vertical gradients due to quick loss of bottom side ionization and rapid uplift of equatorial F layer via prereversal enhancement (PRE) of zonal electric field makes the post-sunset hours as the most preferred local time for the formation of EPBs. However, there is a different class of irregularities that occurs during the post-midnight hours of June solstice reported by the previous studies. The occurrence of these post-midnight EPBs maximize during the low solar activity periods. The growth characteristics and the responsible mechanism for the formation of these post-midnight EPBs are not yet understood. Using the rapid beam steering ability of 47 MHz Equatorial Atmosphere Radar (EAR) at Kototabang (0.2°S geographic latitude, 100.3°E geographic longitude, and 10.4°S geomagnetic latitude), Indonesia, the spatial and temporal evolution of equatorial plasma bubbles (EPBs) were examined to classify the evolutionary-type EPBs from those which formed elsewhere and drifted into the field of view of radar. The responsible mechanism for the genesis of summer time post-midnight EPBs were discussed in light of growth rate of Rayleigh-Taylor instability using SAMI2 model.

  3. Spatial and temporal characteristics of rain intensity in the peninsular Malaysia using TRMM rain rate

    Science.gov (United States)

    Varikoden, Hamza; Samah, A. A.; Babu, C. A.

    2010-06-01

    SummaryThe present study is focused on the intensity distribution of rainfall in different classes and their contribution to the total seasonal rainfall. In addition, we studied the spatial and diurnal variation of the rainfall in the study areas. For the present study, we retrieved data from TRMM (Tropical Rain Measuring Mission) rain rate available in every 3 h temporal and 25 km spatial resolutions. Moreover, station rainfall data is used to validate the TRMM rain rate and found significant correlation between them (linear correlation coefficients are 0.96, 0.85, 0.75 and 0.63 for the stations Kota Bharu, Senai, Cameron highlands and KLIA, respectively). We selected four areas in the Peninsular Malaysia and they are south coastal, east coastal, west coastal and highland regions. Diurnal variation of frequency of rain occurrence is different for different locations. We noticed bimodal variation in the coastal areas in most of the seasons and unimodal variation in the highland/inland area. During the southwest monsoon period in the west coastal stations, there is no distinct diurnal variation. The distribution of different intensity classes during different seasons are explained in detail in the results.

  4. Vegetation and pollen rain relationship from the tropical Atlantic rain forest in Southern Brazil

    Directory of Open Access Journals (Sweden)

    Hermann Behling

    2006-07-01

    Full Text Available The relationship between the southern Brazilian tropical Atlantic lowland rain forest and modern pollen rain was studied by pollen traps. The study was carried out on a one hectare plot undisturbed rain forest of the reserve Volta Velha and two secondary forests, ± 50 and 7 years old. About 248 identified tree, shrub and herb species (excluding epiphytes of 50 families were represented by 126 different pollen and spore types (including non-local taxa. The calculated average influx of pollen rain from the native Atlantic rain forest was 12465 pollen grains per cm² and year. The influx from the ± 50 years old and from the 7 years old secondary forest was relatively low (4112 and 3667 grains per cm² and year, respectively compared to the undisturbed rain forest. The occurrence of pollen grains of herbs and fern spores were significantly higher in the secondary forests than in the undisturbed rain forest.Estudou-se a relação entre a Floresta Tropical Atlântica sul brasileira e a chuva polínica atual através de coletores de pólen. O estudo foi realizado em uma parcela de um hectare de floresta não perturbada localizada na Reserva Volta Velha (26º 04' S, 48º 38' W, 9 m s.n.m. e duas outras parcelas de floresta secundária (± 50 e 7 anos de idade. Cerca de 248 espécies arbóreas, arbustivas e herbáceas (excluindo epifitas, englobadas em 50 familias estavam representadas por 126 diferentes tipos de pólen e esporos (incluindo taxa não locais. Na área não perturbada, a média do fluxo de entrada da chuva polínica foi de 12465 grãos de pólen por cm²/ano. Nas áreas de ± 50 anos e 7 anos correspondentes a estádios florestais secundários o fluxo de entrada foi relativamente baixo (4112 e 3667 grãos por cm²/ano, respectivamente comparativamente à área não perturbada. A ocorrência de grãos de pólen de herbáceas e esporos de pteridófitas foi significativamente maior nas áreas secundárias do que na área não perturbada.

  5. Rainfall and Drought In Equatorial East Africa During The Past 1,100 Years

    Science.gov (United States)

    Verschuren, D.; Laird, K. R.; Cumming, B. F.

    Knowledge of natural long-term rainfall variability is essential for water-resource and land-use management in all dry-land regions of the world. In tropical Africa, data rel- evant to determining this variability are scarce because of the lack of long instrumen- tal climate records and the limited potential of some high-resolution proxy climate archives such as tree rings and ice cores. An 1,100-year reconstruction of decadel- scale variability in African rainfall and drought based on lake-level and salinity fluc- tuations of Lake Naivasha (Eastern Rift Valley, Kenya) now indicates that eastern equatorial Africa within the last millennia has alternated between strongly contrast- ing climatic conditions, including significantly reduced effective moisture during the 'Medieval Warm Period' (~AD 900-1270), and a generally higher effective moisture than today during the 'Little Ice Age' (~AD 1270-1850) interrupted by three episodes of prolonged aridity (~AD 1380-1420, 1560-1620, and 1760-1840) more severe than any historically recorded drought. Pattern and timing of the reconstructed Little Ice Age climate fluctuations correlate with the residual record of atmospheric radiocar- bon production, suggesting that long-term variations in solar radiation may have con- tributed to African rainfall variability at these time scales. In agreement with other recently documented instances of a solar influence on long-term variations in hydro- logical balance, solar minima correlated with increases in effective moisture and solar maxima with increased aridity. It remains unclear, however, whether variation in solar radiation generated fluctuations in effective moisture mainly by means of a direct or indirect influence on rainfall, or rather through the influence of temperature variations on evaporation rates.

  6. RAIN INTENSITY DISTRIBUTION IN THE SPLASH REGION OF ATOMIZED FLOW

    Institute of Scientific and Technical Information of China (English)

    DUAN Hong-dong; LIU Shi-he; LUO Qiu-shi; HUANG Wei

    2006-01-01

    Atomized flow is an unnatural two-phase flow produced while water discharges in water release structures. This flow might threaten the normal operation of hydraulic and hydroelectric installations owing to the unnatural and high-density rain as well as the unnatural and dirty mist. The splash region, the region with the highest rain intensity, hence should receive much attention during the design and operation of the hydraulic and hydroelectric installations. In this paper rain intensity distribution in the splash region of the atomized flow is investigated experimentally, and the method of random simulation is used to predict the rain intensity distribution in the splash region.

  7. Review and Discussion on the Plum Rain Research in China

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    [Objective] The research aimed to review the research progresses and the research achievements of plum rain in China.[Method] By using the precipitation,the sunshine data in the related observatories during 1961-2009 and the daily height field data of NCEP/DOE2 in 1996,which were provided by the National Meteorological Information Center,the prior researches about the plum rain in China were reviewed from the division of plum rain,the range of plum rain area and the space distribution.[Result] The formulati...

  8. Response of soybean seed germination to cadmium and acid rain.

    Science.gov (United States)

    Liu, Ting Ting; Wu, Peng; Wang, Li Hong; Zhou, Qing

    2011-12-01

    Cadmium (Cd) pollution and acid rain are the main environmental issues, and they often occur in the same agricultural region. Nevertheless, up to now, little information on the combined pollution of Cd(2+) and acid rain action on crops were presented. Here, we investigated the combined effect of Cd(2+) and acid rain on the seed germination of soybean. The results indicated that the single treatment with the low level of Cd(2+) (0.18, 1.0, 3.0 mg L(-1)) or acid rain (pH ≥3.0) could not affect the seed germination of soybean, which was resulted in the increased activities of peroxidase and catalase. The single treatment with the high concentration of Cd(2+) (>6 mg L(-1)) or acid rain at pH 2.5 decreased the activities of peroxidase and catalase, damaged the cell membrane and then decreased the seed germination of soybean. Meanwhile, the same toxic effect was observed in the combined treatment with Cd(2+) and acid rain, and the combined treatment had more toxic effect than the single treatment with Cd(2+) or acid rain. Thus, the combined pollution of Cd(2+) and acid rain had more potential threat to the seed germination of soybean than the single pollution of Cd(2+) or acid rain.

  9. Effects of simulated acid rain on vegetation

    Energy Technology Data Exchange (ETDEWEB)

    Ferenbaugh, R.W.

    1974-01-01

    Experiments were performed to determine the effects of simulated acid rain on Chenopodium quinoa, Hordeum vulgare and Phaseolus vulgaris. Because of differential species' susceptibility, detailed experiments were conducted only on Phaseolus vulgaris. Acid rain was simulated by spraying the plants with a hand-held atomizer. Sulfuric acid solutions covering a pH range of 1.5 to 3.5 in one half pH unit increments were used. Gross morphological effects noted at lower pH values included failure to attain normal height, necrosis and wrinkling of leaves, excessive and adventitious budding, and premature abscission of primary leaves. Histological effects included smaller cell size, a decreased amount of intercellular space, hypertrophied nuclei and nucleoli, and a reduction in the size of starch granules within the chloroplasts. Dry weight remained an approximately constant percentage of fresh weight, and chlorophyll analyses showed that both chlorophyll concentration and ratio of chlorophyll 'a' to chlorophyll 'b' also remained constant. Respirometer studies showed that, while respiration rate increased only slightly at low pH values, photosynthetic rate increased dramatically. Quantitative analyses indicated that carbohydrate content was reduced at low pH values, with starch content reduced much more than sugar content. Root biomass was also reduced at low pH values. Application of Congo red indicator solution to the acid treated tissue showed that it was being acidified to a pH of below 4. 114 references, 23 figures, 12 tables.

  10. Rain Rate-Radar Reflectivity Relationship for Drop Size Distribution and Rain Attenuation Calculation of Ku Band Signals

    Directory of Open Access Journals (Sweden)

    Govardhani.Immadi

    2014-05-01

    Full Text Available With the increased demand for long distance Tele communication day by day, satellite communication system was developed. Satellite communications utilize L, C, Ku and Ka bands of frequency to fulfil all the requirements. Utilization of higher frequencies causes severe attenuation due to rain. Rain attenuation is noticeable for frequencies above 10ghz. Amount of attenuation depends on whether the operating wave length is comparable with rain drop diameter or not. In this paper the main focus is on drop size distribution using empirical methods, especially Marshall and Palmer distributions. Empirical methods deal with power law relation between the rain rate(mm/h and radar reflectivity(dBz. Finally it is discussed about the rain rate variation, radar reflectivity, drop size distribution, that is made for two rain events at K L University, Vijayawada on 4th September 2013 and on 18 th August 2013.

  11. A ANTROPOFAGIA NA ÁFRICA EQUATORIAL: ETNO-HISTÓRIA E A REALIDADE DO(S DISCURSO(S SOBRE O REAL

    Directory of Open Access Journals (Sweden)

    S\\u00EDlvio Marcus de Souza Correa

    2008-01-01

    Full Text Available In this article, travelogues and ethnographies of equatorial Africa form a point of departure for reflections on the construction of the "primitive," the "wild," and the "cannibal," in Gabon and neighboring areas. Travel narratives from various periods are discussed, from the first contacts between Europeans and Africans to the studies of German ethnologist Günter Tessmann (1884-1969. The paper also addresses discourse on anthropophagy by African ethnic groups, especially the Okanda and the Mpongwé, showing that they contributed to negative external definitions of their neighbors, the Pahouin and the Fang, especially the latter. Because the subject of anthropophagy is treated here as a topos, it implies reflecting over res ficta as well as res facta - travelogues as well as ethnographic history. This approach provides important insights into some major theoretical and methodological works of ethnohistory.

  12. Spatial and temporal variability of the Glossina palpalis palpalis population in the Mbini focus (Equatorial Guinea

    Directory of Open Access Journals (Sweden)

    Nzambo-Ondo Sisinio

    2007-08-01

    Full Text Available Abstract Background Human African Trypanosomiasis is a vector-borne parasitic disease. The geographical distribution of the disease is linked to the spatial distribution of the tsetse fly. As part of a control campaign using traps, the spatial and temporal variability is analysed of the glossina populations present in the Mbini sleeping sickness foci (Equatorial Guinea. Results A significant drop in the annual mean of the G. p. palpalis apparent density was noted from 2004 to 2005, although seasonal differences were not observed. The apparent density (AD of G. p. palpalis varies significantly from one biotope to another. The fish dryers turned out to be zones with the greatest vector density, although the AD of G. p. palpalis fell significantly in all locations from 2004 to 2005. Conclusion Despite the tsetse fly density being relatively low in fish dryers and jetties, the population working in those zones would be more exposed to infection. The mono-pyramidal traps in the Mbini focus have been proven to be a useful tool to control G. p. palpalis, even though the activity on the banks of the River Wele needs to be intensified. The application of spatial analysis techniques and geographical information systems are very useful tools to discriminate zones with high and low apparent density of G. p. palpalis, probably associated with different potential risk of sleeping sickness transmission.

  13. Atmospheric water vapor transport and recycling in Equatorial Central Africa through NCEP/NCAR reanalysis data

    Energy Technology Data Exchange (ETDEWEB)

    Pokam, Wilfried M.; Djiotang, Lucie A.T.; Mkankam, Francois K. [University of Yaounde 1, Laboratory for Environmental Modelling and Atmospheric Physics, Department of Physics, Faculty of Sciences, P.O. Box 812, Yaounde (Cameroon)

    2012-05-15

    The characteristics of the main components of the water cycle over Equatorial Central Africa (ECA) were analysed using the 32-year period, spanning from 1968 to 2000, of the National Centers for Environmental Prediction-National Censearch (NCEP-) reanalysis project database. A special emphasis was given to identifying the causes of annual and interannual variability of water vapor flux and precipitation recycling. The results suggest that the first maximum of moisture convergence, during the rainy season MAM, comes from upper level moisture flux, related to the north component of the African Easterly Jet (AEJ-N). The second, and greatest, maximum in SON is found to be a consequence of low level moisture advection from the Atlantic Ocean. AEJ-N also drive the seasonal spatial pattern of moisture flux. The interannual variability of moisture flux is contributed mainly by the low level moisture advected from the Atlantic Ocean, underlying its crucial role for the regional climate. Studying the recycling ratio in ECA as a whole shows a low annual cycle whereas subregional scale analysis reveals high amplitude of the seasonal variation. Seasonal variability of the spatial gradient of precipitation recycling is regulated by both moisture flux direction and strength. The annual cycles of recycling ratio in the North and the South of ECA are regulated by both moisture transport and evapotranspiration. (orig.)

  14. Rain attenuation statistics over millimeter wave bands in South Korea

    Science.gov (United States)

    Shrestha, Sujan; Choi, Dong-You

    2017-01-01

    Rain induced degradations are significant for terrestrial microwave links operating at frequencies higher than 10 GHz. Paper presents analyses done on rain attenuation and rainfall data for three years between 2013 till 2015, in 3.2 km experimental link of 38 GHz and 0.1 km link at 75 GHz. The less link distance is maintained for 75 GHz operating frequency in order to have better recording of propagation effect as such attenuation induced by rain. OTT Parsivel is used for collection of rain rate database which show rain rate of about 50 mm/h and attenuation values of 20.89 and 28.55 dB are obtained at 0.01% of the time for vertical polarization under 38 and 75 GHz respectively. Prediction models, namely, ITU-R P. 530-16, Da Silva Mello, Moupfouma, Abdulrahman, Lin and differential equation approach are analyzed. This studies help to identify most suitable rain attenuation model for higher microwave bands. While applying ITU-R P. 530-16, the relative error margin of about 3%, 38% and 42% along with 80, 70, 61% were obtained in 0.1%, 0.01% and 0.001% of the time for vertical polarization under 38 and 75 GHz respectively. Interestingly, ITU-R P. 530-16 shows relatively closer estimation to measured rain attenuation at 75 GHz with relatively less error probabilities and additionally, Abdulrahman and ITU-R P. 530-16 results in better estimation to the measured rain attenuation at 38 GHz link. The performance of prominent rain attenuation models are judged with different error matrices as recommended by ITU-R P. 311-15. Furthermore, the efficacy of frequency scaling technique of rain attenuation between links distribution are also discussed. This study shall be useful for making good considerations in rain attenuation predictions for terrestrial link operating at higher frequencies.

  15. East African highland bananas (Musa spp. AAA-EA) 'worry' more about potassium deficiency than drought stress

    NARCIS (Netherlands)

    Taulya, G.

    2013-01-01

    Drought stress, potassium (K) and nitrogen (N) deficiencies are major constraints to rain-fed East African highland banana (EAHB) production in Uganda. It was hypothesised that the reduction in fresh bunch mass and increase in dry matter (DM) allocation to corms with drought stress, K and N deficien

  16. The Utopian Quest in Bessie Head’s When Rain Clouds Gather and Maru

    Directory of Open Access Journals (Sweden)

    Adamu Pangmeshi

    2009-06-01

    Full Text Available Prior to Nelson Mandela’s ascension to power in South Africa, literature of the country had been essentially a protest against the dehumanizing treatment that was meted on the Blacks by the minority Whites who were at the helm of power through the policy of apartheid. This somehow created socio-political upheavals and a pervasive atmosphere. Consequently, some writers while unfolding this social enigma, did so with a vision of proposing an ideal society for humanity. One of them is Bessie Head. This paper seeks to examine Head’s When Rain Clouds Gather and Maru in a bid to demonstrate that her quest for a perfect society has been provoked by her experiences in life and the dystopian South African. Informed by new historicism, it is argued that an ideal or a perfect society is a figment of the imagination.

  17. Stellar mixing length theory with entropy rain

    CERN Document Server

    Brandenburg, Axel

    2015-01-01

    Stellar mixing length theory is modified to include the effects of a nongradient term that originates from the motion of convective elements with entropy perturbations of either sign. It is argued that such a term, first studied by Deardorff in the meteorological context, represents the effects of thin intense downdrafts caused by the rapid cooling in the granulation layer at the top of the convection zone. They transport heat nonlocally, as originally anticipated by Spruit in the 1990s, who describes the convection in the strongly stratified simulations of Stein & Nordlund as entropy rain. Although our model has ill-determined free parameters, it demonstrates that solutions can be found that look similar to the original ones, except that the deeper layers are now Schwarzschild stable, so no giant cells are produced and the typical convective scale is that of granules even at larger depth. Consequences for modeling solar differential, the global dynamo, and sunspots are briefly discussed.

  18. I-Ching of acid rain

    Energy Technology Data Exchange (ETDEWEB)

    Huber, P.

    The yin/yang of I Chin philosophy can describe the acid/alkali balance and the development of acid rain concerns. The author describes the science of sulfur; the chemistry, transport, and ecological impacts as it moves from coal mine to ocean. He then addresses the regulatory options for reducing sulfur emissions or mitigating their environmental impacts at various stages of the coal-sulfur cycle. He sees no fair conclusion because the scientific community is still unwilling to reach a consensus on the widespread ecological risks and because cost-benefit balancing is neither neutral nor objective. If we conclude that a new regulatory initiative is in order, we should recognize that there are better and worse ways of implementing it. Long-term solutions lie in the aggressive promotion of cleaner coal and noncoal technologies. 3 references, 4 figures.

  19. Industrial concessions, fires and air pollution in Equatorial Asia

    Science.gov (United States)

    Spracklen, D. V.; Reddington, C. L.; Gaveau, D. L. A.

    2015-09-01

    Forest and peatland fires in Indonesia emit large quantities of smoke leading to poor air quality across Equatorial Asia. Marlier et al (2015 Environ. Res. Lett. 10 085005) explore the contribution of fires occurring on oil palm, timber (wood pulp and paper) and natural forest logging concessions to smoke emissions and exposure of human populations to the resulting air pollution. They find that one third of the population exposure to smoke across Equatorial Asia is caused by fires in oil palm and timber concessions in Sumatra and Kalimantan. Logging concessions have substantially lower fire emissions, and contribute less to air quality degradation. This represents a compelling justification to prevent reclassification of logging concessions into oil palm or timber concessions after logging. This can be achieved by including logged forests in the Indonesian moratorium on new plantations in forested areas.

  20. Westward propagating twin gyres in the equatorial Indian Ocean

    Science.gov (United States)

    Reddy, P. Rahul Chand; Salvekar, P. S.; Deo, A. A.; Ganer, D. W.

    2004-01-01

    A reduced-gravity (1$\\frac{1}{2-layer) model forced by daily climatological winds simulates twin, anticyclonic gyres, which propagate westward on either side of the equator. The gyres form at the beginning of both the Southwest Monsoon and the Northeast monsoon in the equatorial eastern Indian Ocean, and subsequently propagate across the basin. Their existence is supported by velocity observations taken during WOCE in 1995 and by TOPEX/Poseidon sea-level observations during 1993. They are also present in the ECCO model/data product. They form at the front of a Rossby-wave packet generated by the reflection of the equatorial jet (EJ) from the eastern boundary of the basin. They are likely either Rossby solitons or result from the nonlinear interaction between the EJ and the Rossby-wave front.

  1. Ongoing Analysis of Jupiter's Equatorial Hotspots and Plumes from Cassini

    Science.gov (United States)

    Choi, D. S.; Showmwn, A. P.; Vasavada, A. R.; Simon-Miller, A. A.

    2012-01-01

    We present updated results from our ongoing analysis of Cassini observations of Jupiter's equatorial meteorology. For two months preceding the spacecraft's closest approach of the planet, the ISS instrument onboard Cassini regularly imaged the atmosphere of Jupiter. We created time-lapse movies from this period that show the complex activity and interactions of the equatorial atmosphere. During this period, hot spots exhibited significant variations in size and shape over timescales of days and weeks. Some of these changes appear to be a result of interactions with passing vortex systems in adjacent latitudes. Strong anticyclonic gyres to the southeast of the dark areas converge with flow from the west and appear to circulate into a hot spot at its southwestern corner.

  2. Altitude and latitude dependence of the equatorial electrojet

    Science.gov (United States)

    Singh, A.; Cole, K. D.

    1988-07-01

    A self-consistent and high-resolution dynamo model is used to investigate the effects of day-to-day or seasonal variation of altitude and latitude profiles of the E-plasma density in the equatorial ionosphere on equatorial electrojet (EEJ) structure. Variations in the E-layer peak altitude and amplitude are shown to significantly affect EEJ structure. The results indicate that, for any shape, the EEJ peak appears at or below the E-layer peak altitude. Distinct double peaks occur in the EEJ structure if the E-layer peak is above 105 km or if the gradient is large. The effect of the latitudinal variation of the integrated conductivities of ionospheric field lines upon the amplitude and altitude of the EEJ peak is discussed.

  3. The Effect of Rain on Air-Water Gas Exchange

    Science.gov (United States)

    Ho, David T.; Bliven, Larry F.; Wanninkhof, Rik; Schlosser, Peter

    1997-01-01

    The relationship between gas transfer velocity and rain rate was investigated at NASA's Rain-Sea Interaction Facility (RSIF) using several SF, evasion experiments. During each experiment, a water tank below the rain simulator was supersaturated with SF6, a synthetic gas, and the gas transfer velocities were calculated from the measured decrease in SF6 concentration with time. The results from experiments with IS different rain rates (7 to 10 mm/h) and 1 of 2 drop sizes (2.8 or 4.2 mm diameter) confirm a significant and systematic enhancement of air-water gas exchange by rainfall. The gas transfer velocities derived from our experiment were related to the kinetic energy flux calculated from the rain rate and drop size. The relationship obtained for mono-dropsize rain at the RSIF was extrapolated to natural rain using the kinetic energy flux of natural rain calculated from the Marshall-Palmer raindrop size distribution. Results of laboratory experiments at RSIF were compared to field observations made during a tropical rainstorm in Miami, Florida and show good agreement between laboratory and field data.

  4. A technique for collecting botanical specimens in rain forest

    NARCIS (Netherlands)

    Hyland, B.P.M.

    1972-01-01

    I. Introduction — The need for a simple method of collecting botanical material from rain-forest trees became evident during the construction of a field key to the rain-forest trees of North Queensland. Many collecting techniques have been developed, e.g. throwing sticks and stones, severing branche

  5. Mechanics of interrill erosion with wind-driven rain

    Science.gov (United States)

    The vector physics of wind-driven rain (WDR) differs from that of wind-free rain, and the interrill soil detachment equations in the Water Erosion Prediction Project (WEPP) model were not originally developed to deal with this phenomenon. This article provides an evaluation of the performance of the...

  6. A Rain Garden for Our School: Becoming Environmental Stewards

    Science.gov (United States)

    McFadyen, Joy

    2012-01-01

    In this article, the author talks about a rain garden project at Hampton Elementary School in Bay City, Michigan. The goal of the project was to slow and filter silt-laden runoff (from parking lots, sidewalks, and playground) on its path to Saginaw Bay in Lake Huron. In addition, doing so, the rain gardens would demonstrate to the township, city,…

  7. Sources of sulphur in rain collected below a wheat canopy

    Energy Technology Data Exchange (ETDEWEB)

    Raybould, C.C.; Unsworth, M.H.; Gregory, P.J.

    1977-05-12

    The quantity of sulfur in rain collected below a maturing wheat canopy was measured. The measurement and calculations show that leaching of plant sulfur by rain was the main source of additional sulfur in throughfall and that most sulfur dry-deposited on leaf surfaces remained fixed there.

  8. 14 CFR 33.78 - Rain and hail ingestion.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Rain and hail ingestion. 33.78 Section 33... hail ingestion. (a) All engines. (1) The ingestion of large hailstones (0.8 to 0.9 specific gravity) at... rain and hail, as defined in appendix B to this part. Acceptable engine operation precludes...

  9. Relativistically speaking: Let's walk or run through the rain?

    CERN Document Server

    Assis, Armando V D B

    2010-01-01

    We analyse under a simple approach the problem one must decide the best strategy to minimize the contact with rain when moving between two points through the rain. The available strategies: walk (low speed boost $<<$ $c$) or run (relativistic speed boost $\\approx$ $c$).

  10. Acid rain compliance: The need for regulatory guidance

    Energy Technology Data Exchange (ETDEWEB)

    Solomon, B.D. [Environmental Protection Agency, Washington, DC (United States)

    1993-07-01

    This article presents a broad view of the need for regulatory guidance when confronting the problem of acid rain. The two major topics addressed are (1) Why is guidance needed and (2) What kind of guidance is needed. Discussion of rate and accounting treatment of allowances, acid rain compliance planning, and allowance trading and energy efficiency are included.

  11. Elementary Acid Rain Kit, Interdisciplinary, Grades 4-8.

    Science.gov (United States)

    Stubbs, Harriett S.; And Others

    An interdisciplinary approach for teaching about acid rain is offered in this curriculum guide for teachers of grades 4-8. Skill and concept areas of science, math, social studies, art, and the language arts are developed in 12 activities which focus on the acid rain problems. A matrix of the activities and subject areas indicates the coverage…

  12. 40 CFR 75.3 - General Acid Rain Program provisions.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 16 2010-07-01 2010-07-01 false General Acid Rain Program provisions. 75.3 Section 75.3 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) CONTINUOUS EMISSION MONITORING General § 75.3 General Acid Rain Program provisions....

  13. A European Acid Rain Program based on the US experience

    DEFF Research Database (Denmark)

    Brandt, U. Steiner; Svendsen, Gert Tinggaard

    2000-01-01

    The paper shows that cost-effective involvement of the source location involves utmost difficulty in practice. Based on the RAINS model, it is recommended that source location should be ignored in a European market for SO2, as is the case in the US Acid Rain Program. Based on the political target...

  14. Hyperspectral Remote Sensing for Tropical Rain Forest

    Directory of Open Access Journals (Sweden)

    Kamaruzaman Jusoff

    2009-01-01

    Full Text Available Problem statement: Sensing, mapping and monitoring the rain forest in forested regions of the world, particularly the tropics, has attracted a great deal of attention in recent years as deforestation and forest degradation account for up to 30% of anthropogenic carbon emissions and are now included in climate change negotiations. Approach: We reviewed the potential for air and spaceborne hyperspectral sensing to identify and map individual tree species measure carbon stocks, specifically Aboveground Biomass (AGB and provide an overview of a range of approaches that have been developed and used to map tropical rain forest across a diverse set of conditions and geographic areas. We provided a summary of air and spaceborne hyperspectral remote sensing measurements relevant to mapping the tropical forest and assess the relative merits and limitations of each. We then provided an overview of modern techniques of mapping the tropical forest based on species discrimination, leaf chlorophyll content, estimating aboveground forest productivity and monitoring forest health. Results: The challenges in hyperspectral Imaging of tropical forests is thrown out to researchers in such field as to come with the latest techniques of image processing and improved mapping resolution leading towards higher precision mapping accuracy. Some research results from an airborne hyperspectral imaging over Bukit Nanas forest reserve was shared implicating high potential of such very high resolution imaging techniques for tropical mixed dipterocarp forest inventory and mapping for species discrimination, aboveground forest productivity, leaf chlorophyll content and carbon mapping. Conclusion/Recommendations: We concluded that while spaceborne hyperspectral remote sensing has often been discounted as inadequate for the task, attempts to map with airborne sensors are still insufficient in tropical developing countries like Malaysia. However, we demonstrated this with a case

  15. Reading the African context

    Directory of Open Access Journals (Sweden)

    Musonda Bwalya

    2012-12-01

    Full Text Available There is so much alienation, pain and suffering in our today�s world. In this vein, African Christianity, a voice amongst many voices, should seek to be a transformational religion for the whole of life, affecting all facets of human life towards a fuller life of all in Africa. This article sought to highlight and point to some of the major societal challenges in the African context which African Christianity, as a life-affirming religion, should continue to embrace, re-embrace and engage with, if it has to be relevant to the African context. In this vein, the article argued that a correct reading of the African context would lead to a more relevant theory and praxis of African Christianity for the benefit of all African peoples and their global neighbours. The contention of this article was that African Christianity has a significant role to play in the re-shaping of the African society and in the global community of humans, only that this role must be executed inclusively, responsibly and appropriately, together with all those who seek the holistic development of Africa towards one common destiny.

  16. Implications of global warming for the climate of African rainforests.

    Science.gov (United States)

    James, Rachel; Washington, Richard; Rowell, David P

    2013-01-01

    African rainforests are likely to be vulnerable to changes in temperature and precipitation, yet there has been relatively little research to suggest how the regional climate might respond to global warming. This study presents projections of temperature and precipitation indices of relevance to African rainforests, using global climate model experiments to identify local change as a function of global temperature increase. A multi-model ensemble and two perturbed physics ensembles are used, one with over 100 members. In the east of the Congo Basin, most models (92%) show a wet signal, whereas in west equatorial Africa, the majority (73%) project an increase in dry season water deficits. This drying is amplified as global temperature increases, and in over half of coupled models by greater than 3% per °C of global warming. Analysis of atmospheric dynamics in a subset of models suggests that this could be partly because of a rearrangement of zonal circulation, with enhanced convection in the Indian Ocean and anomalous subsidence over west equatorial Africa, the Atlantic Ocean and, in some seasons, the Amazon Basin. Further research to assess the plausibility of this and other mechanisms is important, given the potential implications of drying in these rainforest regions.

  17. Distribution and activity of diazotrophs in the Eastern Equatorial Atlantic

    OpenAIRE

    Foster, Rachel A.; Subramaniam, Ajit; Jonathan P Zehr

    2009-01-01

    The gene abundance and gene expression of six diazotroph populations from the Eastern Equatorial Atlantic in June 2007 were examined using nifH gene quantitative polymerase chain reaction (q PCR) methods. Of all the diazotrophs, Trichodesmium spp. was the most abundant with the highest number of gene copies in the Gulf of Guinea. Trichodesmium also had the highest nitrogenase gene transcript abundance overall with the maximum in samples collected at the equator and in waters influenced by the...

  18. Saturn's equatorial jet structure from Cassini/ISS

    Science.gov (United States)

    García-Melendo, Enrique; Legarreta, Jon; Sánchez-Lavega, Agustín.; Pérez-Hoyos, Santiago; Hueso, Ricardo

    2010-05-01

    Detailed wind observations of the equatorial regions of the gaseous giant planets, Jupiter and Saturn, are crucial for understanding the basic problem of the global circulation and obtaining new detailed information on atmospheric phenomena. In this work we present high resolution data of Saturn's equatorial region wind profile from Cassini/ISS images. To retrieve wind measurements we applied an automatic cross correlator to image pairs taken by Cassini/ISS with the MT1, MT2, MT3 filters centred at the respective three methane absorbing bands of 619nm, 727nm, and 889nm, and with the adjacent continuum CB1, CB2, and CB3 filters. We obtained a complete high resolution coverage of Saturn's wind profile in the equatorial region. The equatorial jet displays an overall symmetric structure similar to that shown the by same region in Jupiter. This result suggests that, in accordance to some of the latest compressible atmosphere computer models, probably global winds in gaseous giants are deeply rooted in the molecular hydrogen layer. Wind profiles in the methane absorbing bands show the effect of strong vertical shear, ~40m/s per scale height, confirming previous results and an important decay in the wind intensity since the Voyager era (~100 m/s in the continuum and ~200 m/s in the methane absorbing band). We also report the discovery of a new feature, a very strong and narrow jet on the equator, about only 5 degrees wide, that despite the vertical shear maintains its intensity (~420 m/s) in both, the continuum and methane absorbing band filters. Acknowledgements: Work supported by the Spanish MICIIN AYA2009-10701 with FEDER and Grupos Gobierno Vasco IT-464-07.

  19. Meteorology of Jupiter's Equatorial Hot Spots and Plumes from Cassini

    Science.gov (United States)

    Choi, David Sanghun; Showman, Adam P.; Vasavada, Ashwin R.; Simon-Miller, Amy A.

    2013-01-01

    We present an updated analysis of Jupiter's equatorial meteorology from Cassini observations. For two months preceding the spacecraft's closest approach, the Imaging Science Subsystem (ISS) onboard regularly imaged the atmosphere. We created time-lapse movies from this period in order to analyze the dynamics of equatorial hot spots and their interactions with adjacent latitudes. Hot spots are relatively cloud-free regions that emit strongly at 5 lm; improved knowledge of these features is crucial for fully understanding Galileo probe measurements taken during its descent through one. Hot spots are quasistable, rectangular dark areas on visible-wavelength images, with defined eastern edges that sharply contrast with surrounding clouds, but diffuse western edges serving as nebulous boundaries with adjacent equatorial plumes. Hot spots exhibit significant variations in size and shape over timescales of days and weeks. Some of these changes correspond with passing vortex systems from adjacent latitudes interacting with hot spots. Strong anticyclonic gyres present to the south and southeast of the dark areas appear to circulate into hot spots. Impressive, bright white plumes occupy spaces in between hot spots. Compact cirrus-like 'scooter' clouds flow rapidly through the plumes before disappearing within the dark areas. These clouds travel at 150-200 m/s, much faster than the 100 m/s hot spot and plume drift speed. This raises the possibility that the scooter clouds may be more illustrative of the actual jet stream speed at these latitudes. Most previously published zonal wind profiles represent the drift speed of the hot spots at their latitude from pattern matching of the entire longitudinal image strip. If a downward branch of an equatorially-trapped Rossby wave controls the overall appearance of hot spots, however, the westward phase velocity of the wave leads to underestimates of the true jet stream speed.

  20. Recurring Slope Lineae in Mid-Latitude and Equatorial Mars

    Science.gov (United States)

    McEwen, A. S.; Dundas, C. M.; Mattson, S.; Toigo, A. D.; Ojha, L.; Wray, J. J.; Chojnacki, M.; Byrne, S.; Murchie, S. L.; Thomas, N.

    2013-12-01

    A key to potential present-day habitability of Mars is the presence of liquid H2O (water). Recurring slope lineae (RSL) could be evidence for the seasonal flow of water on relatively warm slopes. RSL are narrow (250 K to >300 K. In the past year we have monitored active RSL in equatorial (0°-15°S) regions of Mars, especially in the deep canyons of Valles Marineris. They are especially active on north-facing slopes in northern summer and spring and on south-facing slopes in southern spring and summer, following the most normal solar incidence angles on these steep slopes. However, predicted peak temperatures for north-facing slopes are nearly constant throughout the Martian year because orbital periapse occurs near the southern summer solstice. Although warm temperatures and steep low-albedo slopes are required, some additional effect besides temperature may serve to trigger and stop RSL activity. Seasonal variation in the atmospheric column abundance of water does not match the RSL activity. Although seasonal melting of shallow ice could explain the mid-latitude RSL, the equatorial activity requires a different explanation, perhaps migration of briny groundwater. To explain RSL flow lengths, exceeding 1 km in Valles Marineris, the water is likely to be salty. Several RSL attributes are not yet understood: (1) the relation between apparent RSL activity and dustiness of the atmosphere; (2) salt composition and concentration; (3) variability in RSL activity from year to year; (4) seasonal activity on north-facing equatorial slopes in spite of little change in temperature; and (5) temporal changes in the color properties of fans where RSL terminate. Continued orbital monitoring, laboratory experiments, and future orbital and landed exploration with new measurement types are needed. Equatorial water activity, if confirmed, creates new exploration opportunities and challenges. RSL >1 km long near boundary between Eos and Capri Chasmata of Valles Marineris, Mars.

  1. Climate regulation of fire emissions and deforestation in equatorial Asia

    OpenAIRE

    van der Werf, G. R.; Dempewolf, J.; Trigg, S.N.; Randerson, J. T.; Kasibhatla, P. S.; De Giglio, L.; D. Murdiyarso; W. Peters; Morton, D. C.; COLLATZ, G.J.; DOLMAN, A.J.; DeFries, R. S.

    2008-01-01

    Drainage of peatlands and deforestation have led to large-scale fires in equatorial Asia, affecting regional air quality and global concentrations of greenhouse gases. Here we used several sources of satellite data with biogeochemical and atmospheric modeling to better understand and constrain fire emissions from Indonesia, Malaysia, and Papua New Guinea during 2000–2006. We found that average fire emissions from this region [128 ± 51 (1σ) Tg carbon (C) year−1, T = 1012] were comparable to fo...

  2. Millennial-scale dynamics of southern Amazonian rain forests.

    Science.gov (United States)

    Mayle, F E; Burbridge, R; Killeen, T J

    2000-12-22

    Amazonian rain forest-savanna boundaries are highly sensitive to climatic change and may also play an important role in rain forest speciation. However, their dynamics over millennial time scales are poorly understood. Here, we present late Quaternary pollen records from the southern margin of Amazonia, which show that the humid evergreen rain forests of eastern Bolivia have been expanding southward over the past 3000 years and that their present-day limit represents the southernmost extent of Amazonian rain forest over at least the past 50,000 years. This rain forest expansion is attributed to increased seasonal latitudinal migration of the Intertropical Convergence Zone, which can in turn be explained by Milankovitch astronomic forcing.

  3. Rain and deicing experiments in a wind tunnel

    Science.gov (United States)

    Fasso, G.

    1983-01-01

    Comments on films of tests simulating rain and ice conditions in a wind tunnel are presented, with the aim of studying efficient methods of overcoming the adverse effects of rain and ice on aircraft. In the experiments, lifesize models and models of the Mirave 4 aircraft were used. The equipment used to simulate rain and ice is described. Different configurations of landing and takeoff under conditions of moderate or heavy rain at variable angles of incidence and of skipping and at velocities varying from 30 to 130 m/sec are reproduced in the wind tunnel. The risks of erosion of supersonic aircraft by the rain during the loitering and approach phases are discussed.

  4. Tropical Cyclone - Equatorial Ionosphere Coupling: A Statistical Study

    Science.gov (United States)

    Bhagavathiammal, G. J.

    2016-07-01

    This paper describes the equatorial ionosphere response to tropical cyclone events which was observed over the Indian Ocean. This statistical study tries to reveal the possible Tropical Cyclone (TC) - Ionosphere coupling. Tropical cyclone track and data can be obtained from the India Meteorological Department, New Delhi. Digisonde/Ionosonde data for the equatorial latitudes can be obtained from Global Ionospheric Radio Observatory. It is believed that TC induced convection as the driving agent for the increased gravity wave activity in the lower atmosphere and these propagating gravity waves deposit their energy and momentum into the upper atmosphere as Travelling Ionospheric Disturbances (TIDs). The convective regions are identified with the help of Outgoing Long wave radiation (OLR) data from NOAA Climate Data Center/ Precipitation data from TRMM Statellite. The variability of ionospheric parameter like Total Electron Content (TEC), foF2, h'F2 and Drift velocity are examined during TC periods. This study will report the possibility of TC-Ionosphere Coupling in equatorial atmosphere.

  5. Relationship of the South Asian Monsoon and Regional Drought with Distinct Equatorial Pacific SST Patterns on Interannual and Decadal Timescales

    Science.gov (United States)

    Hernandez, M.; Ummenhofer, C.; Anchukaitis, K. J.

    2014-12-01

    The Asian monsoon system influences the lives of over 60% of the planet's population, with widespread socioeconomic effects resulting from weakening or failure of monsoon rains. Spatially broad and temporally extended drought episodes have been known to dramatically influence human history, including the Strange Parallels Drought in the mid-18th century. Here, we explore the dynamics of sustained monsoon failure using the Monsoon Asia Drought Atlas - a high-resolution network of hydro-climatically sensitive tree-ring records - and a 1300-year pre-industrial control run of the Community Earth System Model (CESM). Spatial drought patterns in the instrumental and model-based Palmer Drought Severity Index (PDSI) during years with extremely weakened South Asian monsoon are similar to those reconstructed during the Strange Parallels Drought in the MADA. We further explore how the large-scale Indo-Pacific climate during weakened South Asian monsoon differs between interannual and decadal timescales. The Strange Parallels Drought pattern is observed during March-April-May primarily over Southeast Asia, with decreased precipitation and reduced moisture fluxes, while anomalies in June-July-August are confined to the Indian subcontinent during both individual and decadal events. Individual years with anomalous drying exhibit canonical El Niño conditions over the eastern equatorial Pacific and associated shifts in the Walker circulation, while decadal events appear to be related to anomalous warming around the dateline in the equatorial Pacific, typical of El Niño Modoki events. The results suggest different dynamical processes influence drought at different time scales through distinct remote ocean influences.

  6. A plea to better feed African soils

    Science.gov (United States)

    Stroosnijder, Leo

    2014-05-01

    Most African cropping system are rainfed. Rain is distributed at the soil surface over infiltration and runoff. The infiltrated water is stored in the rootable soil layer and the excess drains below that layer into the groundwater. The stored water is partly lost as evaporation to the atmosphere and partly used as transpiration for plant growth. In African cropping system the green water use efficiency (GWUE: fraction transpiration over rainfall) is as low as 15%. This low value is due to the often poor soil quality (physical, chemical and biological) of African soils. The poor physical state causes a weak soil structure resulting in crust formation with low infiltration and high runoff as consequences. The water holding capacity of the rootable soil layer is also poor, causing quite some water lost into deeper layers. African soils are poor due to long time soil mining. Soil life depends on soil organic matter (SOM) which is decreasing everywhere at an average rate of 2% per year. It is common sense that an improved soil quality is essential for improved food security. The key that triggers a sustainable improvement in soil quality is a system's approach that focus on the management of organic resources. Soil is a living organism, and it feeds on SOM. This feed is continuously consumed but a living soil makes new SOM out of fresh organic matter. In order to keep our soils alive we need cropping systems that feed our soils with fresh organic matter in the form of crop residues in the right mix of quality and quantity. The tendency to breed crops with a high harvest index (hence low straw) and the many other uses of crop residues (competing claims) with it recent use for bio-ethanol fabrication is disastrous for our living soils. If we continue to allow SOM to decrease, soil crusting and hard setting will increase with less end less water available for the production of green biomass. Lower available water will trigger a negative spiral with lower food security and

  7. Mapping the East African Ionosphere Using Ground-based GPS TEC Measurements

    Science.gov (United States)

    Mengist, Chalachew Kindie; Kim, Yong Ha; Yeshita, Baylie Damtie; Workayehu, Abyiot Bires

    2016-03-01

    The East African ionosphere (3°S-18°N, 32°E-50°E) was mapped using Total Electron Content (TEC) measurements from ground-based GPS receivers situated at Asmara, Mekelle, Bahir Dar, Robe, Arbaminch, and Nairobi. Assuming a thin shell ionosphere at 350 km altitude, we project the Ionospheric Pierce Point (IPP) of a slant TEC measurement with an elevation angle of >10° to its corresponding location on the map. We then infer the estimated values at any point of interest from the vertical TEC values at the projected locations by means of interpolation. The total number of projected IPPs is in the range of 24-66 at any one time. Since the distribution of the projected IPPs is irregularly spaced, we have used an inverse distance weighted interpolation method to obtain a spatial grid resolution of 1°×1° latitude and longitude, respectively. The TEC maps were generated for the year 2008, with a 2 hr temporal resolution. We note that TEC varies diurnally, with a peak in the late afternoon (at 1700 LT), due to the equatorial ionospheric anomaly. We have observed higher TEC values at low latitudes in both hemispheres compared to the magnetic equatorial region, capturing the ionospheric distribution of the equatorial anomaly. We have also confirmed the equatorial seasonal variation in the ionosphere, characterized by minimum TEC values during the solstices and maximum values during the equinoxes. We evaluate the reliability of the map, demonstrating a mean error (difference between the measured and interpolated values) range of 0.04-0.2 TECU (Total Electron Content Unit). As more measured TEC values become available in this region, the TEC map will be more reliable, thereby allowing us to study in detail the equatorial ionosphere of the African sector, where ionospheric measurements are currently very few.

  8. Atlantic forcing of Western Mediterranean winter rain minima during the last 12,000 years

    Science.gov (United States)

    Zielhofer, Christoph; Fletcher, William J.; Mischke, Steffen; De Batist, Marc; Campbell, Jennifer F. E.; Joannin, Sebastien; Tjallingii, Rik; El Hamouti, Najib; Junginger, Annett; Stele, Andreas; Bussmann, Jens; Schneider, Birgit; Lauer, Tobias; Spitzer, Katrin; Strupler, Michael; Brachert, Thomas; Mikdad, Abdeslam

    2017-02-01

    The limited availability of high-resolution continuous archives, insufficient chronological control, and complex hydro-climatic forcing mechanisms lead to many uncertainties in palaeo-hydrological reconstructions for the Western Mediterranean. In this study we present a newly recovered 19.63 m long core from Lake Sidi Ali in the North African Middle Atlas, a transition zone of Atlantic, Western Mediterranean and Saharan air mass trajectories. With a multi-proxy approach based on magnetic susceptibility, carbonate and total organic C content, core-scanning and quantitative XRF, stable isotopes of ostracod shells, charcoal counts, Cedrus pollen abundance, and a first set of diatom data, we reconstruct Western Mediterranean hydro-climatic variability, seasonality and forcing mechanisms during the last 12,000 yr. A robust chronological model based on AMS 14C dated pollen concentrates supports our high-resolution multi-proxy study. Long-term trends reveal low lake levels at the end of the Younger Dryas, during the mid-Holocene interval 6.6 to 5.4 cal ka BP, and during the last 3000 years. In contrast, lake levels are mostly high during the Early and Mid-Holocene. The record also shows sub-millennial- to centennial-scale decreases in Western Mediterranean winter rain at 11.4, 10.3, 9.2, 8.2, 7.2, 6.6, 6.0, 5.4, 5.0, 4.4, 3.5, 2.9, 2.2, 1.9, 1.7, 1.5, 1.0, 0.7, and 0.2 cal ka BP. Early Holocene winter rain minima are in phase with cooling events and millennial-scale meltwater discharges in the sub-polar North Atlantic. Our proxy parameters do not show so far a clear impact of Saharan air masses on Mediterranean hydro-climate in North Africa. However, a significant hydro-climatic shift at the end of the African Humid Period (∼5 ka) indicates a change in climate forcing mechanisms. The Late Holocene climate variability in the Middle Atlas features a multi-centennial-scale NAO-type pattern, with Atlantic cooling and Western Mediterranean winter rain maxima generally

  9. Empowering African States

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    China helps bring lasting peace and stability to Africa African think tanks expressed a high opinion of China’s role in helping build African peace and security at the first meeting of the China-Africa Think Tanks Forum. The

  10. African Literature as Celebration.

    Science.gov (United States)

    Achebe, Chinua

    1989-01-01

    Describes the Igbo tradition of "Mbari," a communal creative enterprise that celebrates the world and the life lived in it through art. Contrasts the cooperative, social dimension of pre-colonial African culture with the exclusion and denial of European colonialism, and sees new African literature again celebrating human presence and…

  11. African American Suicide

    Science.gov (United States)

    African American Suicide Fact Sheet Based on 2012 Data (2014) Overview • In 2012, 2,357 African Americans completed suicide in the U.S. Of these, 1,908 (80. ... rate of 9.23 per 100,000). The suicide rate for females was 1.99 per 100, ...

  12. African Peacekeepers in Africa

    DEFF Research Database (Denmark)

    Emmanuel, Nikolas G.

    2015-01-01

    behind African participation in United Nations (UN) peacekeeping operations in Africa. In doing so, this research focuses on US military aid and foreign troop training from 2002 to 2012, and its impact on African deployments into UN peacekeeping missions in Africa. As can be expected, such third...

  13. African agricultural trade

    DEFF Research Database (Denmark)

    Jensen, Hans Grinsted; Sandrey, Ron

    2015-01-01

    This article starts with a profile of African agricultural trade. Using the pre-release version 9.2 of the GTAP database, we then show that the results for tariff elimination on intra-African trade are promising, but these tariff barriers are not as significant as the various trade-related barriers...

  14. Mesopelagic fishes across the tropical and equatorial Atlantic: Biogeographical and vertical patterns

    Science.gov (United States)

    Olivar, M. Pilar; Hulley, P. Alexander; Castellón, Arturo; Emelianov, Mikhail; López, Cristina; Tuset, Víctor M.; Contreras, Tabit; Molí, Balbina

    2017-02-01

    In this investigation we analysed the changes in fish species occurrences and relative abundances across the tropical and equatorial Atlantic, and their vertical distribution patterns in relation to the different environmental scenarios. The study covers a wide region encompassing different water masses, and marked differences in productivity, from an oligotrophic zone close to the Brazilian coast, to a very productive upwelling region close to the Northwest African upwelling. Fishes were collected with a medium-sized midwater trawl (Mesopelagos), complemented by hauls made with a macrozooplankton net (MOCNESS). Species richness in the region was higher than in subtropical, temperate and cold regions. The total number of species and their overall abundance was lower in the stations closer to the Brazilian coast. Abundant species across the entire region were the gonostomatids Cyclothone alba, Cyclothone acclinidens, Cyclothone pallida and Cyclothone pseudopallida, the myctophid Lampanyctus alatus, the sternoptychid Sternoptyx diaphana, and the phosichthyid Vinciguerria nimbaria. The occurrences and abundances of C. parapallida, Lampanyctus nobilis and Lepidophanes guentheri were related to zones where AAIW waters occupied the mesopelagic layers, while other species such as Cyclothone livida and Polyipnus polli increased their abundance when AAIW disappears from their living depths. The presence of Eastern North Atlantic Central Water (ENACW) was associated with the occurrence of several myctophids (Benthosema glaciale, Ceratoscopelus maderensis, Diaphus holti, Diaphus rafinesquii, Hygophum hygomii, Lampanyctus crocodilus, Myctophum punctatum, Symbolophorus veranyi), and the gonostomatid Cyclothone braueri. In spite of the important differences in hydrographic features across the tropical and equatorial Atlantic, all stations showed either the general night migration into the epipelagic layers carried out by myctophids, phosicthyids, and some stomiids, or the

  15. Frequent Rain Observation From Geostationary Satellite

    Science.gov (United States)

    Bizzarri, B.; Gomas Science Team

    The target 3-h observing cycle of GPM will meet requirements from Global NWP and, to a large extent, Regional NWP; and be supportive of VIS/IR-derived rain estimates from geostationary satellites for the purpose of Nowcasting. MW rain observation from geostationary orbit at, say, 15 min intervals, would fully meet Regional NWP requirements and have greatest impact on Nowcasting: but this implies either unprac- tically large antennas or unacceptably coarse resolution. Concepts to overcome this problem have been developed in the US within the study called GEM (Geostationary Microwave Observatory), and now there is in Europe a proposal for a demonstration satellite submitted to ESA as GOMAS (Geostationary Observatory for Microwave Atmospheric Sounding). To overcome the problem of resolution, use of Sub-mm fre- quencies is envisaged: e.g., at 425 GHz, a 10-km resolution at nadir would require a 3-m antenna. The observing principle is based on the use of absorption bands of oxygen (54, 118 and 425 GHz) and of water vapour (183 and 380 GHz). Narrow- bandwidths channels are implemented (for a total of about 40 in the five bands) so as to observe the full profile of temperature and water vapour. Profiles from different bands are differently affected by liquid and ice water of different drop size, and fi- nally by precipitation. Simultaneous retrieval of temperature/humidity profiles, cloud liquid/ice water (total-columns and gross profile) and precipitation rate is in principle possible, and partially demonstrated by several airborne MW/Sub-mm instruments. To transfer this demonstrations in the geostationary orbit, the problem of radiometric sensitivity (additional to that one of the antenna size) has to be solved. With current technology, it is feasible to get sufficient accuracy if scan is limited to about 1/12 of the Earth disk, which is sufficient to abundantly cover Europe, the Mediterranean and Eastern Atlantic. The imaged area can be moved everywhere within the disk

  16. Use of Machine Learning Techniques for Identification of Robust Teleconnections to East African Rainfall Variability

    Science.gov (United States)

    Roberts, J. Brent; Robertson, F. R.; Funk, C.

    2014-01-01

    Hidden Markov models can be used to investigate structure of subseasonal variability. East African short rain variability has connections to large-scale tropical variability. MJO - Intraseasonal variations connected with appearance of "wet" and "dry" states. ENSO/IOZM SST and circulation anomalies are apparent during years of anomalous residence time in the subseasonal "wet" state. Similar results found in previous studies, but we can interpret this with respect to variations of subseasonal wet and dry modes. Reveal underlying connections between MJO/IOZM/ENSO with respect to East African rainfall.

  17. Effect of simulated acid rain on vegetation

    Energy Technology Data Exchange (ETDEWEB)

    Ferenbaugh, R.W.

    1974-01-01

    Experiments were performed to determine the effects of simulated acid rain on Chenopodium quinoa, Hordeum vulgare and Phaseolus vulgaris. Detailed experiments were conducted only on Phaseolus vulgaris. Sulfuric acid solutions covering a pH range of 1.5 to 3.5 were used. Gross morphological effects noted at lower pH values included failure to attain normal height, necrosis and wrinkling of leaves, excessive and adventitious budding, and premature abscission of primary leaves. Histological effects included smaller cell size, a decreased amount of intercellular space, hypertrophied nuclei and nucleoli, and a reduction in the size of starch granules within the chloroplasts. Dry weight remained an approximately constant percentage of fresh weight, and chlorophyll analyses showed that both chlorophyll concentration and ratio of chlorophyll to chlorophyll also remained constant. Respirometer studies showed that respiration rate increased slightly and photosynthetic rate increased dramatically. Quantitative analyses indicated that carbohydrate content was reduced at low pH values. Root biomass was also reduced. Application of Congo red indicator solution to the acid treated tissue showed that it was being acidified to a pH of below 4. Experiments involving aspiration of control tissue in acid solutions suggest that the increase in photosynthetic rate and the decreases in carbohydrate content and root biomass were caused by an uncoupling of photophosphorylation of adenosine diphosphate. Uncoupling was probably caused by hydrogen ion interference with proton pumps associated with the electron transport chain in the light reactions of photosynthesis. 128 references. (MDF)

  18. Tempered by Winds and Rains of Nature

    Institute of Scientific and Technical Information of China (English)

    1996-01-01

    A few years ago, a popular TV program Animal World produced by China Central Television (CCTV), was well received by men and women, old and young, and people from all circles. Sun Qiuping, a reporter from CCTV, led her colleagues to film the section about wild animals in China.For six years, Sun and her colleagues sought those nearly extinct wild animals in the virgin forests and barren hills. They experienced many hardships, and even the trial of death.In 1992, Sun won first prize in the First National TV Program Contest for her first TV program Oasis in the Mist about the tropical rain forest and its wild life. She also won awards for photography and music. Sun edited the TV program Mongoose and won a first prize for programs on special topics. Because of her accomplishments, she has been awarded the prize of the CCTV director’s special fund, and was named a national "March 8 Pacesetter’ by the All-China Women’s Federation.

  19. Structures of Equatorial Envelope Rossby Wave Under a Generalized External Forcing

    Institute of Scientific and Technical Information of China (English)

    FUZun-Tao; LIUShi-Da; LIUShi-Kuo

    2004-01-01

    The cubic nonlinear Schroedinger (NLS for short) equation with a generalized external heating source is derived for large amplitude equatorial envelope Rossby wave in a shear flow. And then various periodic structures for these equatorial cnvelope Rossby waves are obtained with the help of a new transformation, Jacobi elliptic functions,and elliptic equation. It is shown that different types of resonant phase-locked diabatic heating play different roles in structures of equatorial envelope Rossby wave.

  20. Structures of Equatorial Envelope Rossby Wave Under a Generalized External Forcing

    Institute of Scientific and Technical Information of China (English)

    FU Zun-Tao; LIU Shi-Da; LIU Shi-Kuo

    2004-01-01

    The cubic nonlinear Schrodinger (NLS for short) equation with a generalized external heating source is derived for large amplitude equatorial envelope Rossby wave in a shear flow. And then various periodic structures for these equatorial envelope Rossby waves are obtained with the help of a new transformation, Jacobi elliptic functions,and elliptic equation. It is shown that different types of resonant phase-locked diabatic heating play different roles in structures of equatorial envelope Rossby wave.

  1. New Measurements Of Jupiter's Equatorial Region In Visible Wavelengths

    Science.gov (United States)

    Rojas, Jose; Arregi, J.; García-Melendo, E.; Barrado-Izagirre, N.; Hueso, R.; Gómez-Forrellad, J. M.; Pérez-Hoyos, S.; Sanz-Requena, J. F.; Sánchez-Lavega, A.

    2010-10-01

    We have studied the equatorial region of Jupiter, between 15ºS and 15ºN, on Cassini ISS images obtained during the Jupiter flyby at the end of 2000 and on HST images acquired in May and July 2008. We have found significant longitudinal variations in the intensity of the 6ºN eastward jet, up to 60 m s-1 in Cassini and HST observations. In the HST case we found that these longitudinal variations are associated to different cloud morphology. Photometric and radiative transfer analysis of the cloud features used as tracers in HST images shows that there is only a small height difference, no larger than 0.5 - 1 scale heights at most, between the slow ( 100 m s-1) and fast ( 150 m s-1) moving features. This suggests that speed variability at 6ºN is not dominated by vertical wind shears and we propose that Rossby wave activity is the responsible for the zonal variability. After removing this variability we found that Jupiter's equatorial jet is actually symmetric relative to the equator with two peaks of 140 - 150 m s-1 located at latitudes 6ºN and 6ºS and at a similar pressure level. We also studied a large, long-lived feature called the White Spot (WS) located at 6ºS that turns to form and desapear. The internal flow field in the White Spot indicates that it is a weakly rotating quasi-equatorial anticyclone relative to the ambient meridionally sheared flow. Acknowledgements: This work was supported by the Spanish MICIIN AYA2009-10701 with FEDER and Grupos Gobierno Vasco IT-464-07.

  2. Jovian Equatorial H Lyman-alpha and the Ionosphere

    Science.gov (United States)

    Ballester, Gilda E.

    An excess of H Ly alpha emission has been a persistent feature in Jupiter's equatorial upper atmosphere since its discovery in 1978. This Ly alpha 'bulge' was found by high-resolution IUE observations to be due to broadening of the Jovian line increasing the resonant scattering of the solar Ly alpha, rather than from a local enhancement in the H density. The line broadening implies that the H column at the bulge is disturbed by a localized, non-thermal process, and two mechanisms have been proposed to explain this: one by the generation of turbulence from strong thermospheric winds or jets meeting at the bulge region and originating in the active Jovian auroral zones, the other involving a superthermal population of H atoms produced by a process analogous to the equatorial anomaly and tropical arcs on the Earth. Some line broadening was also observed in the off-bulge region while modelling of the usual bulge profile does not predict this behavior, but these observations may have been performed at a time of an unusually large extension of the bulge. We propose to make a series of high-dispersion observations (of improved S/N) for a detailed longitudinal study of the line profile which would be of benefit independently of the particular bulge conditions (to be determined with low-dispersion exposures). In addition, new insight will be gained with simultaneous ground-based observations of the newly discovered global ionospheric H3+ emissions. These emissions are diagnostic of the ionospheric temperature and ion density, and have already shown very particular characteristics in the H Ly alpha bulge region. Coordinated observations of the whole longitudinal range should therefore set new constraints on the mechanisms operating in the Jovian equatorial upper atmosphere.

  3. Discovery Of A Rossby Wave In Jupiter's South Equatorial Region

    Science.gov (United States)

    Simon-Miller, Amy A.; Choi, D. S.; Rogers, J. H.; Gierasch, P. J.

    2012-01-01

    A detailed study of the chevron-shaped dark spots on the strong southern equatorial wind jet near 7.5 deg S planetographic latitude shows variations in velocity with longitude and time. The chevrons move with velocities near the maximum wind jet velocity of approx.140 m/s, as deduced by the history of velocities at this latitude and the magnitude of the symmetric wind jet near 7 deg N latitude. Their repetitive nature is consistent with an inertia-gravity wave (n = 75-100) with phase speed up to 25 m/s, relative to the local flow, but the identity of this wave mode is not well constrained. However, high spatial resolution movies from Cassini images show that the chevrons oscillate in latitude with a approx.7-day period. This oscillating motion has a wavelength of approx.20 deg and a speed of approx.100 m/s, following a pattern similar to that seen in the Rossby wave plumes of the North Equatorial Zone, and possibly reinforced by it, though they are not perfectly in phase. The transient anticyclonic South Equatorial Disturbance (SED) may be a similar wave feature, but moves at slower velocity. All data show chevron latitude variability, but it is unclear if this Rossby wave is present during other epochs, without time series movies that fully delineate it. In the presence of multiple wave modes, the difference in dominant cloud appearance between 7 deg N and 7.5 deg S may be due to the presence of the Great Red Spot, either through changes in stratification and stability or by acting as a wave boundary.

  4. Ocean atmosphere thermal decoupling in the eastern equatorial Indian ocean

    Science.gov (United States)

    Joseph, Sudheer; Ravichandran, M.; Kumar, B. Praveen; Jampana, Raju V.; Han, Weiqing

    2016-09-01

    Eastern equatorial Indian ocean (EEIO) is one of the most climatically sensitive regions in the global ocean, which plays a vital role in modulating Indian ocean dipole (IOD) and El Niño southern oscillation (ENSO). Here we present evidences for a paradoxical and perpetual lower co-variability between sea-surface temperature (SST) and air-temperature (Tair) indicating instantaneous thermal decoupling in the same region, where signals of the strongly coupled variability of SST anomalies and zonal winds associated with IOD originate at inter-annual time scale. The correlation minimum between anomalies of Tair and SST occurs in the eastern equatorial Indian ocean warm pool region (≈70°E-100°E, 5°S-5°N), associated with lower wind speeds and lower sensible heat fluxes. At sub-monthly and Madden-Julian oscillation time scales, correlation of both variables becomes very low. In above frequencies, precipitation positively contributes to the low correlation by dropping Tair considerably while leaving SST without any substantial instant impact. Precipitation is led by positive build up of SST and post-facto drop in it. The strong semi-annual response of SST to mixed layer variability and equatorial waves, with the absence of the same in the Tair, contributes further to the weak correlation at the sub-annual scale. The limited correlation found in the EEIO is mainly related to the annual warming of the region and ENSO which is hard to segregate from the impacts of IOD.

  5. African American Diaspora

    Directory of Open Access Journals (Sweden)

    Angela Brown

    2013-07-01

    Full Text Available The migration of blacks in North America through slavery became united.  The population of blacks past downs a tradition of artist through art to native born citizens. The art tradition involved telling stories to each generation in black families. The black culture elevated by tradition created hope to determine their personal freedom to escape from poverty of enslavement and to establish a way of life through tradition. A way of personal freedoms was through getting a good education that lead to a better foundation and a better way of life. With regard to all historic migrations (forced and voluntary, the African Union defined the African diaspora as "[consisting] of people of African origin living outside the continent, irrespective of their citizenship and nationality and who are willing to contribute to the development of the continent and the building of the African Union." Its constitutive act declares that it shall "invite and encourage the full participation of the African diaspora as an important part of our continent, in the building of the African Union." Keywords: literature concepts, African American abstracts

  6. A Tropical Ocean Recharge Mechanism for Climate Variability. Part I: Equatorial Heat Content Changes Induced by the Off-Equatorial Wind.

    Science.gov (United States)

    Wang, Xiaochun; Jin, Fei-Fei; Wang, Yuqing

    2003-11-01

    A reduced-gravity shallow-water model, an oceanic general circulation model for the Pacific region, and the analytical model of the equatorial β plane bounded in the zonal direction are used to investigate the equatorial thermocline response to tropical and subtropical wind stress forcing. The results show that the wind stress forcing in the tropical and subtropical region can generate a nearly zonal uniform thermocline depth change in the equatorial region. The response timescale is longer when the wind stress is placed farther away from the equator. There exist latitude bands around 10° 15°N and 10° 15°S where the forcing can cause a relatively large equatorial response. When the forcing is located in the eastern basin, the response timescale is longer and its magnitude is larger than the case when the forcing is located in the western basin. Thus the eastern tropical to subtropical region is a relatively effective area for off-equatorial wind stress to generate an equatorial thermocline response. When the wind stress forcing has a longer period, the response of the equatorial thermocline has a larger magnitude. The results from this study's numerical experiments and the analytical solution are consistent. The present study has implications for the broad-scale ocean atmosphere interaction in the tropical region.

  7. Provisional hourly values of equatorial Dst for 1971

    Science.gov (United States)

    Sugiura, M.; Poros, D. J.

    1972-01-01

    Tables and plots of provisional hourly values of the equatorial Dst index for 1971 are given, a table of daily mean Dst values for 1971 is also provided. The base line values for the four observatories, Hermanus, Kakioka, Honolulu, and San Juan, were obtained from extrapolations using the coefficients for the secular variations determined for the previous years. Examining the Dst values for quiet days, the base lines so determined appear to be slightly low, so that the Dst index for quiet periods tends to be high.

  8. Seasonal variability of the bifurcation of the North Equatorial Current

    Institute of Scientific and Technical Information of China (English)

    JU Qiang-chang; JIANG Song; TIAN Ji-wei; KONG Ling-hai; NI Guo-xi

    2013-01-01

    Seasonal variability of the bifurcation of the North Equatorial Current (NEC) is studied by constructing the analytic solution for the time-dependent horizontal linear shallow water quasi-geostrophic equations.Using the Florida State University wind data from 1961 through 1992,we find that the bifurcation latitude of the NEC changes with seasons.Furthermore,it is shown that the NEC bifurcation is at its southernmost latitude (12.7°N) in June and the northernmost latitude (14.4° N) in November.

  9. Quality control of rain data used for urban runoff systems

    DEFF Research Database (Denmark)

    Jørgensen, H. K.; Rosenørn, S.; Madsen, Henrik

    1998-01-01

    for collection and quality control of rain data from a network of tipping bucket rain gauges in Denmark carried out by the Danish Meteorological Institute. During rain, the RIMCO gauge counts the number of tips teach of 0.2 mm of precipitation) every minute, The quality control of the rain data includes...... an automatic and a manual bit marking, where the automatic control basically is pointing out minutes with extreme intensities. In the manual control, the maximum intensities as well as the daily totals of precipitation are inspected, using weather charts, intensity plots and precipitation sums of nearby...... Hellmann gauges. Shortcomings and improvements of the quality control are discussed. Although, it is possible to improve the efficiency of the quality control, long term corrections will always be necessary. (C) 1998 Published by Elsevier Science Ltd. All rights reserved....

  10. Memoirs of a Survivor: Masuji Ibuse's Black Rain

    Institute of Scientific and Technical Information of China (English)

    Peter Messent

    2005-01-01

    This paper examines the motif of survival in Masuji Ibuse's Hiroshima novel Black Rain (1969). It explores narrative technique, figurative language, voice and tone, and the gap between thought and feeling, to show how the novel achieves its artistic effects.

  11. NOS CO-OPS Meteorological Data, Rain Fall, 6-Minute

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset has Rain Fall data from NOAA NOS Center for Operational Oceanographic Products and Services (CO-OPS). WARNING: These preliminary data have not been...

  12. Rain Lõhmus toob mängu kupeldaja / Priit Pullerits

    Index Scriptorium Estoniae

    Pullerits, Priit, 1965-

    2005-01-01

    Investeerimispanga Lõhmus, Haavel & Viisemann (LHV) nõukogu esimees on seotud teleäriga ja püüab käivitada uut telekanalit. Vt. samas: Rain Lõhmus vastab küsimustele, mis puudutavad LHVga seotud skandaali mõju panga tegevusele ja käimasolevatele äriasjadele. Lisa: Rain Lõhmus. Vt. samas: Mida Lõhmus teleärist teab?

  13. Rain waves-wind waves interaction application to scatterometry

    Science.gov (United States)

    Kharif, C.; Giovanangeli, J. P.; Bliven, L.

    1989-01-01

    Modulation of a rain wave pattern by longer waves has been studied. An analytical model taking into account capillarity effects and obliquity of short waves has been developed. Modulation rates in wave number and amplitude have been computed. Experiments were carried out in a wave tank. First results agree with theoretical models, but higher values of modulation rates are measured. These results could be taken into account for understanding the radar response from the sea surface during rain.

  14. Sampling errors in satellite estimates of tropical rain

    Science.gov (United States)

    Mcconnell, Alan; North, Gerald R.

    1987-01-01

    The GATE rainfall data set is used in a statistical study to estimate the sampling errors that might be expected for the type of snapshot sampling that a low earth-orbiting satellite makes. For averages over the entire 400-km square and for the duration of several weeks, strong evidence is found that sampling errors less than 10 percent can be expected in contributions from each of four rain rate categories which individually account for about one quarter of the total rain.

  15. The Extension of the RAINS Model to Greenhouse Gases

    OpenAIRE

    Klaassen, G.; AMANN, M; Berglund, C; J. Cofala; Hoeglund-Isaksson, L.; Heyes, C.; MECHLER R.; Tohka, A.; W. Schoepp; Winiwarter, W.

    2004-01-01

    Many of the traditional air pollutants and greenhouse gases have common sources, offering a cost-effective potential for simultaneous improvements for both traditional air pollution problems as well as climate change. A methodology has been developed to extend the RAINS integrated assessment model to explore synergies and trade-offs between the control of greenhouse gases and air pollution. With this extension, the RAINS model allows now the assessment of emission control costs for the six gr...

  16. Acid rain project biosurveys of streams in the Wastwater catchment

    OpenAIRE

    Prigg, R.F.

    1985-01-01

    This is the Acid rain project biosurveys of streams in the Wastwater catchment produced by the North West Water Authority in 1985. This report forms part of a series on component biological investigations, identified by location or topic, within the acid rain project. Reporting of the Wastwater catchment data would not have been given priority ordinarily, but it has been brought forward to coincide with J. Robinson's reporting of his investigations of land use and liming in the catchment. Thi...

  17. Rain, Rain, Go Away, Come Again Another Day. Weather Preferences of Summer Tourists in Mountain Environments

    Directory of Open Access Journals (Sweden)

    Robert Steiger

    2016-04-01

    Full Text Available Weather and climate are important factors for travel decision-making and overall tourist satisfaction. As central motivators for destination choice, they directly and indirectly influence demand patterns and can be a resource and limitation for tourism at the same time. In this paper, results of an in-situ survey of mountain summer tourists (n = 733 in the Alps in Southern Germany are presented. Respondents rated ‘rain’ as the most important aspect of weather during their holiday. During a 7-day holiday, 2.1 days of continuous rain are accepted, and 3.1 days of days with thunderstorms. The ideal temperature range is between 21 and 25 °C, thus lying 4–7 degrees lower than for beach tourism. Temperatures below 15 °C and above 30 °C are perceived as unacceptable. Statistically significant differences were found for several tourist types: Older tourists are more sensitive to heat, tourists with sports activities are more tolerant to cool temperatures, first-time visitors are more sensitive to rain and families with children prefer higher temperatures. From the results, some implications for mountain destinations arise: mountain destinations could be promoted as a heat refuge, and attracting sports tourists might be a promising way to reduce weather sensitivity; however, some variety of well-promoted weather independent attractions seems to be mandatory.

  18. Suppression of warm rain by aerosols in rain-shadow areas of India

    Directory of Open Access Journals (Sweden)

    M. Konwar

    2010-07-01

    Full Text Available Aircraft observations of clouds and aerosols were conducted during the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX executed by the Indian Institute of Tropical Meteorology over the Indian subcontinent during the period of May–September 2009. Existence of aerosol layer with large concentrations of cloud drop condensation nuclei extended up to heights of 4 to 5 km was observed over the rain shadow areas to the east of the Western Ghats over central India. The thick aerosol layers were observed to suppress the formation of warm rain in convective clouds up to heights of about 7 km, where mixed phase precipitation formed. This prevented clouds that did not exceed this height from precipitating significantly. This might invigorate the very deep clouds on expense of the smaller clouds. The aerosol radiative effects are suspected to decrease the surface heating and hence the available energy for propelling the convection. The net effect of the aerosols on the rainfall amounts is unknown due to the complexity of the effect, but it is suspected to be detrimental in an area where the rainfall is critical to the livelihood of the inhabitants. This requires continuation of this research.

  19. Improved Gradation for Rain Garden of Low Impact Development

    Science.gov (United States)

    Lee, Sandra; Chang, Fu-Ming

    2016-04-01

    With rapid urban and economic development, living standard improves in urban areas but urban ecological environments deteriorate rapidly. Urban waterlogging and flooding have become a serious problem for urban water security. As urbanization continues, sustainability is the key to balance between urban development and healthy environment. Rain garden is recommended to be one of the best ways to reduce urban pollutants. It not only diminishes runoff flooding but also purify water in the urban area. The studies on rain gardens are mainly about how to incorporate rain garden to purify water quality, but lack of researches on runoff control. This project focuses on rain garden under Low Impact Development using indoor laboratory to test and quantify the water holding capacities of two different Taiwan indigenous rain garden plants, Taiwan Cyclosorus and Sour Grass. The results show that the water holding capacity of Sour Grass (10%-37%) is better than that of Taiwan Cyclosorus (6.8%-17.3%). The results could be a helpful reference for Low Impact Development in urban flood prevention and urban planning. Keywords: Low Impact Development; rain garden; indoor laboratory experiments; water holding capacity; porosity

  20. Rain Attenuation Prediction for Terrestrial Microwave Link in Bangladesh

    Directory of Open Access Journals (Sweden)

    HOSSAIN Sakir

    2014-05-01

    Full Text Available Rain attenuation is a major shortcoming of microwave transmission. As a subtropical country, Bangladesh is one of the highest rainy areas of the world. Thus, designing a terrestrial microwave link is a serious challenge to the engineers. In this paper, the annual rain rate and monthly variation of rate are predicted for different percentage of time of the year from the measured rainfall data. Using ITU rain model for terrestrial microwave communication, the rain attenuation is predicted for five major cities of Bangladesh, namely Dhaka, Chittagong, Rajshahi, Sylhet, and Khulna. It is found that rain attenuation is the most severe in Sylhet and least in Rajshahi. The attenuation is estimated for different frequency and polarization. A horizontally polarized signal encounters 15% more rain attenuation than that of vertically polarized signal. It is also found that attenuation in Rajshahi is about 20% lesser than that in Sylhet. Thus, the horizontally polarized transmission in Rajshahi experiences about 5% less attenuation than the vertically polarized transmission in Sylhet.

  1. On validation of the rain climatic zone designations for Nigeria

    Science.gov (United States)

    Obiyemi, O. O.; Ibiyemi, T. S.; Ojo, J. S.

    2016-04-01

    In this paper, validation of rain climatic zone classifications for Nigeria is presented based on global radio-climatic models by the International Telecommunication Union-Radiocommunication (ITU-R) and Crane. Rain rate estimates deduced from several ground-based measurements and those earlier estimated from the precipitation index on the Tropical Rain Measurement Mission (TRMM) were employed for the validation exercise. Although earlier classifications indicated that Nigeria falls into zones P, Q, N, and K for the ITU-R designations, and zones E and H for Crane's climatic zone designations, the results however confirmed that the rain climatic zones across Nigeria can only be classified into four, namely P, Q, M, and N for the ITU-R designations, while the designations by Crane exhibited only three zones, namely E, G, and H. The ITU-R classification was found to be more suitable for planning microwave and millimeter wave links across Nigeria. The research outcomes are vital in boosting the confidence level of system designers in using the ITU-R designations as presented in the map developed for the rain zone designations for estimating the attenuation induced by rain along satellite and terrestrial microwave links over Nigeria.

  2. TEC variations and IRI-2012 performance at equatorial latitudes over Africa during low solar activity

    Science.gov (United States)

    Olawepo, A. O.; Adeniyi, J. O.; Oluwadare, E. J.

    2017-04-01

    GPS-TEC data obtained from Asmara (Geomag. Lat 11.42N, Long. 113.31E), Bahir Dar (Geomag. Lat. 8.04N, Long. 111.19E), and Eldoret (Geomag. Lat. 2.71S, Long. 107.30E), three stations in the equatorial region of the African sector, have been used to study the variations in the vertical total electron content (vTEC) and to investigate the performance of the three topside options in the IRI-2012 during the year 2010, a year of low solar activity (Rz = 16). The results revealed that TEC exhibits diurnal, seasonal and latitudinal characteristics. TEC values over the three stations are minimum during the sunrise hour of 0600LT and maximum around 1200LT-1500LT irrespective of the season. Daytime peak is followed by a steady decay in TEC which continues into the mid-night. TEC values during the equinoxes are observed to be greater than those of the solstices. TEC values during March equinox are higher than those of September equinox for the stations in the northern hemisphere. June solstices exhibit the lowest values for all the stations. For the station in the southern hemisphere, TEC values during December solstice values are slightly higher than those of September equinox. The three topside options in IRI-2012 reproduce the morphology of TEC at the three stations with correlation coefficient ranging between 0.97 and 0.99. The performance of NeQuick option at predicting TEC at these stations is observed to be the best compared to the other two options irrespective of the season.

  3. African Otter Workshop

    Directory of Open Access Journals (Sweden)

    Jan Reed-Smith

    2016-04-01

    Full Text Available All concerned thought this was an excellent workshop with important progress made towards creating a viable beginning of an African Otter Network. There is a long road ahead but the 2015 African Otter Workshop is a start on developing range country partners, activists and researchers as well as collaborating on issue identification and resolution which will assist in preserving at least some refugia for Africa’s otters. A list of actions was agreed on, including the creation of an African Otter Network website and social media network, apublic Otter Awareness facebook page, encouraging online reporting of otter sightings, conducting otter awareness surveys, and emphasising the need for communication with the public, other members of the network and other professionals. information not shared or documented is information LOST. A Second African Otter Workshop should be held in 2017 elsewhere in Africa to encourage attendance from a wider range of countries.

  4. African Americans and Glaucoma

    Science.gov (United States)

    ... Us Donate In This Section African Americans and Glaucoma email Send this article to a friend by ... and eventually, in developing more effective treatments. Does glaucoma treatment differ? Although treatment varies for all individuals, ...

  5. Artesunate/amodiaquine malaria treatment for Equatorial Guinea (Central Africa).

    Science.gov (United States)

    Charle, Pilar; Berzosa, Pedro; de Lucio, Aida; Raso, José; Nseng Nchama, Gloria; Benito, Agustín

    2013-06-01

    The objectives of this study were: 1) to evaluate the safety and efficacy of combination artesunate (AS)/amodiaquine (AQ) therapy, and 2) to determine the difference between recrudescence and resistance. An in vivo efficacy study was conducted in Equatorial Guinea. A total of 122 children 6-59 months of age from two regional hospitals were randomized and subjected to a 28-day clinical and parasitological follow-up. A blood sample on Whatman paper was taken on Days 0, 7, 14, 21, and 28 or on any day in cases of treatment failure, with the parasite DNA then being extracted for molecular analysis purposes. A total of 4 children were excluded, and 9 cases were lost to follow-up. There were 17 cases of late parasitological failure, 3 cases of late clinical failure, and 89 cases of adequate clinical and parasitological response. The parasitological failure rate was 18.3% (20 of 109) and the success rate 81.70% (95% confidence interval [72.5-87.9%]). After molecular correction, real treatment efficacy stood at 97.3%. Our study showed the good efficacy of combination AS/AQ therapy. This finding enabled this treatment to be recommended to Equatorial Guinea's National Malaria Control Program to change the official treatment policy as of March 2008.

  6. Check list of the Melastomataceae of Equatorial Guinea

    Directory of Open Access Journals (Sweden)

    Geerinck, Daniel

    2003-12-01

    Full Text Available A chec klist of the Melastomataceae of Equatorial Guinea is presented with 57 taxa. Three species were accepted based only on literature records, their distribution área strongly suggests their presence in Equatorial Guinea. Six species are known from Annobón, 23 from Bioko and 49 from Río Muni. Best-represented genera are Memecylon (10, Calvoa (10 and Tristemma (7. Twenty-six taxa are newly recorded for the country. Heterotis obamae Lejoly & Lisowski is set in synonymy with the previously described Heterotis arenaria Jacq.-Fél.Se presenta el catálogo florístico de la familia Melastomataceae en Guinea Ecuatorial. Se recogen un total de 57 táxones. Tres especies fueron aceptadas teniendo en cuenta solamente la literatura. Su distribución sugiere que su presencia en Guinea Ecuatorial es muy probable. En Annobón están presentes 6 especies, 23 en Bioko y 49 en Río Muni. Los géneros mejor representados son Memecylon (10 especies, Calvoa (10 y Tristemma (7.Veintiséis táxones son citados por primera vez en Guinea Ecuatorial. Se propone Heterotis obamae Lejoly & Lisowski como sinónimo de Heterotis arenaria Jacq.-Fél.

  7. Recurring slope lineae in equatorial regions of Mars

    Science.gov (United States)

    McEwen, Alfred S.; Dundas, Colin M.; Mattson, Sarah S.; Toigo, Anthony D.; Ojha, Lujendra; Wray, James J.; Chojnacki, Matthew; Byrne, Shane; Murchie, Scott L.; Thomas, Nicolas

    2014-01-01

    The presence of liquid water is a requirement of habitability on a planet. Possible indicators of liquid surface water on Mars include intermittent flow-like features observed on sloping terrains. These recurring slope lineae are narrow, dark markings on steep slopes that appear and incrementally lengthen during warm seasons on low-albedo surfaces. The lineae fade in cooler seasons and recur over multiple Mars years. Recurring slope lineae were initially reported to appear and lengthen at mid-latitudes in the late southern spring and summer and are more common on equator-facing slopes where and when the peak surface temperatures are higher. Here we report extensive activity of recurring slope lineae in equatorial regions of Mars, particularly in the deep canyons of Valles Marineris, from analysis of data acquired by the Mars Reconnaissance Orbiter. We observe the lineae to be most active in seasons when the slopes often face the sun. Expected peak temperatures suggest that activity may not depend solely on temperature. Although the origin of the recurring slope lineae remains an open question, our observations are consistent with intermittent flow of briny water. Such an origin suggests surprisingly abundant liquid water in some near-surface equatorial regions of Mars.

  8. Transition from inspiral to plunge for eccentric equatorial Kerr orbits

    CERN Document Server

    O'Shaughnessy, R

    2003-01-01

    Ori and Thorne have discussed the duration and observability (with LISA) of the transition from circular, equatorial inspiral to plunge for stellar-mass objects into supermassive ($10^{5}-10^{8}M_{\\odot}$) Kerr black holes. We extend their computation to eccentric Kerr equatorial orbits. Even with orbital parameters near-exactly determined, we find that there is no universal length for the transition; rather, the length of the transition depends sensitively -- essentially randomly -- on initial conditions. Still, Ori and Thorne's zero-eccentricity results are essentially an upper bound on the length of eccentric transitions involving similar bodies (e.g., $a$ fixed). Hence the implications for observations are no better: if the massive body is $M=10^{6}M_{\\odot}$, the captured body has mass $m$, and the process occurs at distance $d$ from LISA, then $S/N \\lesssim (m/10 M_{\\odot})(1\\text{Gpc}/d)\\times O(1)$, with the precise constant depending on the black hole spin. For low-mass bodies ($m \\lesssim 7 M_\\odot$...

  9. Fourier Series Approximations to J2-Bounded Equatorial Orbits

    Directory of Open Access Journals (Sweden)

    Wei Wang

    2014-01-01

    Full Text Available The current paper offers a comprehensive dynamical analysis and Fourier series approximations of J2-bounded equatorial orbits. The initial conditions of heterogeneous families of J2-perturbed equatorial orbits are determined first. Then the characteristics of two types of J2-bounded orbits, namely, pseudo-elliptic orbit and critical circular orbit, are studied. Due to the ambiguity of the closed-form solutions which comprise the elliptic integrals and Jacobian elliptic functions, showing little physical insight into the problem, a new scheme, termed Fourier series expansion, is adopted for approximation herein. Based on least-squares fitting to the coefficients, the solutions are expressed with arbitrary high-order Fourier series, since the radius and the flight time vary periodically as a function of the polar angle. As a consequence, the solutions can be written in terms of elementary functions such as cosines, rather than complex mathematical functions. Simulations enhance the proposed approximation method, showing bounded and negligible deviations. The approximation results show a promising prospect in preliminary orbits design, determination, and transfers for low-altitude spacecrafts.

  10. New observations of ionospheric instabilities in the equatorial electrojet

    Science.gov (United States)

    Alken, P.; Maus, S.

    2009-12-01

    The equatorial electrojet (EEJ) is an intense current system flowing along the magnetic equator in the ionospheric E-region on the day-side. Early attempts to model the EEJ found that ionospheric instabilities led to significant changes in the current which had to be accounted for. Early modelers used ad-hoc empirical correction factors in the relevant ionospheric parameters to attempt to account for instability effects. Modern EEJ models continue to use these correction factors, which are still not well understood theoretically. In the last decade, a wealth of new data has been recorded by both satellites and ground radars which allows us to revisit the issue of modeling these ionospheric instabilities. In this work, we use radar and magnetic field measurements at Jicamarca in addition to magnetometer measurements from the CHAMP satellite to study the effects of ionospheric instabilities on the EEJ. We find that the effects of ionospheric instabilities lead to non-linear behavior between the eastward electric field strength and the resulting electrojet current. As predicted, the ratio of current to electric field is highest for westward and weak eastward electric fields, and the ratio decreases with stronger eastward electric fields. Quantifying this non-linearity should help improve the accuracy of equatorial electrodynamic models.

  11. Steepened structures in equatorial spread F. 2: Theory

    Science.gov (United States)

    Hysell, D. L; Seyler, C. E.; Kelley, M. C.

    1994-01-01

    This paper investigates the properties of a one-dimensional fluid model of plasma convection in the equatorial F region ionosphere. The model equations are similar in form to Burgers equation except for additional higher-order spatial derivatives. Like Burgers equation, solution to the model have the form of propagating, shocklike structures. Numerical simulations of the model closely resemble the steepened structures observed by sounding rocket plasma density probes within equatorial spread F. Simulated denstiy power spectra, like the spectra computed from in situ data, seem to possess power law forms with a break at wavelengths of about 100 m. The precise wavenumber of the spectral break is determined by the ambipolar diffusion coefficient. The model predicts that electric field fluctuations perpendicular to the direction of plasma steepening should be proportional to the plasma density fluctuations. Electric field fluctuations parallel to the steepening will be due primarily to the ambipolar field and have a Boltzmann relationship with density (square of the absolute value of delta E) approximately equal to (K(exp 2))(square of the absolute value of (delta n/n)). At wavelengths less than about 300 m, the ambipolar field should be the dominant component of the total field intensity.

  12. Climatology characterization of equatorial plasma bubbles using GPS data

    Science.gov (United States)

    Magdaleno, Sergio; Herraiz, Miguel; Altadill, David; de la Morena, Benito A.

    2017-01-01

    The climatology of equatorial plasma bubbles (EPBs) for the period 1998-2008 was studied using slant total electron content (sTEC) derived from global positioning system (GPS) data. The sTEC values were calculated from data measured at 67 International GNSS Service (IGS) stations distributed worldwide around the geomagnetic equator and embracing the region of the ionospheric equatorial anomaly (IEA). EPBs and their characteristics were obtained using the Ionospheric Bubble Seeker (IBS) application, which detects and distinguishes sTEC depletions associated with EPBs. This technique bases its analysis on the time variation of the sTEC and on the population variance of this time variation. IBS finds an EPB by default when an sTEC depletion is greater than 5 TEC units (TECu). The analysis of the spatial behavior shows that the largest rate of EPB takes place at the equator and in the South America-Africa sector, while their occurrence decreases as the distance from the magnetic equator increases. The depth and duration of the sTEC depletions also maximize at the equator and in the South America-Africa sector and weaken departing from the equator. The results of the temporal analysis for the data of the IGS stations located in AREQ, NKLG, IISC, and GUAM indicate that the greatest rate of EPB occurrence is observed for high solar activity.

  13. SpIES: The Spitzer IRAC Equatorial Survey

    CERN Document Server

    Timlin, John D; Richards, Gordon T; Lacy, Mark; Ryan, Erin L; Stone, Robert B; Bauer, Franz E; Brandt, W N; Fan, Xiaohui; Glikman, Eilat; Haggard, Daryl; Jiang, Linhua; LaMassa, Stephanie M; Lin, Yen-Ting; Makler, Martin; McGehee, Peregrine; Myers, Adam D; Schneider, Donald P; Urry, C Megan; Wollack, Edward J; Zakamska, Nadia L

    2016-01-01

    We describe the first data release from the Spitzer-IRAC Equatorial Survey (SpIES); a large-area survey of 115 deg^2 in the Equatorial SDSS Stripe 82 field using Spitzer during its 'warm' mission phase. SpIES was designed to probe sufficient volume to perform measurements of quasar clustering and the luminosity function at z > 3 to test various models for "feedback" from active galactic nuclei (AGN). Additionally, the wide range of available multi-wavelength, multi-epoch ancillary data enables SpIES to identify both high-redshift (z > 5) quasars as well as obscured quasars missed by optical surveys. SpIES achieves 5{\\sigma} depths of 6.13 {\\mu}Jy (21.93 AB magnitude) and 5.75 {\\mu}Jy (22.0 AB magnitude) at 3.6 and 4.5 microns, respectively - depths significantly fainter than WISE. We show that the SpIES survey recovers a much larger fraction of spectroscopically-confirmed quasars (98%) in Stripe 82 than are recovered by WISE (55%). This depth is especially powerful at high-redshift (z > 3.5), where SpIES reco...

  14. Climatology characterization of equatorial plasma bubbles using GPS data

    Directory of Open Access Journals (Sweden)

    Magdaleno Sergio

    2017-01-01

    Full Text Available The climatology of equatorial plasma bubbles (EPBs for the period 1998–2008 was studied using slant total electron content (sTEC derived from global positioning system (GPS data. The sTEC values were calculated from data measured at 67 International GNSS Service (IGS stations distributed worldwide around the geomagnetic equator and embracing the region of the ionospheric equatorial anomaly (IEA. EPBs and their characteristics were obtained using the Ionospheric Bubble Seeker (IBS application, which detects and distinguishes sTEC depletions associated with EPBs. This technique bases its analysis on the time variation of the sTEC and on the population variance of this time variation. IBS finds an EPB by default when an sTEC depletion is greater than 5 TEC units (TECu. The analysis of the spatial behavior shows that the largest rate of EPB takes place at the equator and in the South America-Africa sector, while their occurrence decreases as the distance from the magnetic equator increases. The depth and duration of the sTEC depletions also maximize at the equator and in the South America-Africa sector and weaken departing from the equator. The results of the temporal analysis for the data of the IGS stations located in AREQ, NKLG, IISC, and GUAM indicate that the greatest rate of EPB occurrence is observed for high solar activity.

  15. Acid Rain. Activities for Grades 4 to 12. A Teacher's Guide.

    Science.gov (United States)

    Wood, David; Bryant, Jeannette

    This teacher's guide on acid rain is divided into three study areas to explain: (1) what causes acid rain; (2) what problems acid rain has created; and (3) what teachers and students can do to help combat acid rain. Instructions for activities within the study areas include suggested grade levels, objectives, materials needed, and directions for…

  16. 40 CFR 72.31 - Information requirements for Acid Rain permit applications.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 16 2010-07-01 2010-07-01 false Information requirements for Acid Rain... (CONTINUED) AIR PROGRAMS (CONTINUED) PERMITS REGULATION Acid Rain Permit Applications § 72.31 Information requirements for Acid Rain permit applications. A complete Acid Rain permit application shall include...

  17. Acid Rain: A Teacher's Guide. Activities for Grades 4 to 12.

    Science.gov (United States)

    National Wildlife Federation, Washington, DC.

    This guide on acid rain for elementary and secondary students is divided into three study areas: (1) What Causes Acid Rain; (2) What Problems Acid Rain Has Created; (3) How You and Your Students Can Help Combat Acid Rain. Each section presents background information and a series of lessons pertaining to the section topic. Activities include…

  18. Tropical Pacific Sea Surface Temperature Anomalies, El Niño, and Equatorial Westerly Wind Events*.

    Science.gov (United States)

    Vecchi, Gabriel A.; Harrison, D. E.

    2000-06-01

    The authors examine global statistical relationships between westerly wind events (WWEs) and sea surface temperature anomaly (SSTA) variability, using a compositing technique for the period 1986-98. The authors describe the extent to which equatorial WWEs are associated with central and eastern equatorial Pacific waveguide warming and with local SSTA changes under the WWE. Their goal is to quantify the extent to which equatorial WWEs are fundamental to the onset and maintenance of warm El Niño-Southern Oscillation conditions. In order to understand the effect of WWEs on SSTA evolution, they begin by examining how SSTA changes in the absence of equatorial WWEs. They find that SSTA tends toward mean climate values in the absence of equatorial WWEs, whether the eastern equatorial Pacific has close to normal SSTA or warmer than normal SSTA.The two equatorial WWE types whose main surface wind anomalies are west of the date line are associated with weak local surface cooling. The equatorial WWE type that has equatorial westerly wind anomalies east of the date line is associated with weak warming under those anomalies, when the eastern equatorial Pacific SSTA is close to normal.When the tropical Pacific has near-normal eastern equatorial Pacific SST, each of the equatorial WWE types is followed by substantial equatorial waveguide warming in the central and eastern Pacific (composite warming as large as 1.0°C); also more than 50% of the large-amplitude WWEs were followed by Niño-3 SSTA warming in excess of 0.5°C. These changes are of similar amplitude and spatial structure as those seen in the onset of El Niño and are consistent with the predicted oceanic response to WWE forcing. When the eastern equatorial Pacific is initially warmer than usual, the two westernmost equatorial WWE types are associated with the maintenance of warm El Niño eastern and central Pacific SSTA; these warm anomalies tend to disappear in the absence of those WWE types. WWEs, or some mechanism

  19. Geoconservation - a southern African and African perspective

    Science.gov (United States)

    Reimold, Wolf Uwe

    1999-10-01

    In contrast to Europe, where geoconservation is actively pursued in most countries and where two international symposia on this subject have been staged in 1991 and 1996, geoconservation in Africa has indeed a very poor record. Considering the wealth of outstanding geological sites and the importance African stratigraphy has within the global geological record, pro-active geoconservation on this continent has not featured very prominently to date. In the interest of science, education and tourism, unique and typical geosites need to be identified, catalogued, and prioritised with the aim being their protection. Most African countries do not have vibrant non-governmental organisations such as a strong geological society, which could drive projects like geoconservation, or strong support from the private sector for environmental work. Here, a case is made for the role that established National Geological Surveys, some of which are already involved with retroactive environmental geological work, could play in the forefront of pro-active geoconservation and site protection.

  20. Parallel plate capacitor analogy of equatorial plasma bubble and associated fringe fields with implications to equatorial valley region irregularities

    Science.gov (United States)

    Mukherjee, S.; Patra, A. K.

    2014-08-01

    VHF radar echoes from the valley region plasma irregularities, displaying ascending pattern, are often observed during the active phase of equatorial plasma bubble in the close vicinity of the geomagnetic equator and have been attributed to bubble-related fringe field effect. These irregularities however are not observed at a few degrees away from the equator. In this paper, we attempt to understand this contrasting observational result by comparing fringe field at the geomagnetic equator and low latitudes. We use parallel plate capacitor analogy of equatorial plasma bubble and choose a few capacitor configurations, consistent with commonly observed dimension and magnetic field-aligned property of plasma bubble, for computing fringe field. Results show that fringe field decreases significantly with decreasing altitude as expected. Further, fringe field decreases remarkably with latitude, which clearly indicates the role of magnetic field-aligned property of plasma bubble in reducing the magnitude of fringe field at low latitudes compared to that at the geomagnetic equator. The results are presented and discussed in the light of current understanding of plasma bubble-associated fringe field-induced plasma irregularities in the valley region.

  1. Scattering by Artificial Wind and Rain Roughened Water Surfaces at Oblique Incidences

    Science.gov (United States)

    Craeye, C.; Sobieski, P. W.; Bliven, L. F.

    1997-01-01

    Rain affects wind retrievals from scatterometric measurements of the sea surface. To depict the additional roughness caused by rain on a wind driven surface, we use a ring-wave spectral model. This enables us to analyse the rain effect on K(u) band scatterometric observations from two laboratory experiments. Calculations based on the small perturbation method provide good simulation of scattering measurements for the rain-only case, whereas for combined wind and rain cases, the boundary perturbation method is appropriate.

  2. Observation of fluorscent particles in rain water using Laser scanning microscope

    OpenAIRE

    古池, 聖生; 鈴木, 款

    1997-01-01

    Rain water contains various insoluble particles. Detection and observation of in-soluble organic particles in rain water with a fluorescence microscope has been studied. A laser scanning microscope was used for observation of fluorescent particles. Rain water was collected from July 1996 to December 1996 in Shizuoka, and 17 rain water samples were collected. Fluorescent particles in rain water were characterized as organic matter using a Fourier transform infrared (FTIR) microscope. It was fo...

  3. Field evaluation of an acid rain-drought stress interaction.

    Science.gov (United States)

    Banwart, W L

    1988-01-01

    Various methods have been proposed to simulate natural field conditions for growing agricultural crops while controlling conditions to study specific environmental effects. This report briefly describes the use of moveable rain exclusion shelters (10.4 x 40.9 m) to study the results of the interaction of acid rain and drought stress on corn and soybean yields. The rain exclusion shelters are constructed of galvanized pipe framing and covered with polyethylene film. Movement is automated by a rain switch to protect crops from ambient rainfall and to treat them with simulated acid rain The facility simulates a real environment with respect to variables such as solar exposure, wind movement, dew formation, and insect exposure, while allowing careful control of moisture regimes. Soybeans and corn were treated with average rainfall amounts, and with one-half and one-quarter of these rainfall amounts (drought stress) at two levels of rainfall acidity, pH 5.6 and 3.0. While drought stress resulted in considerable yield reduction for Amsoy and Williams soybeans, no additional reduction in yield was observed with rainfall of pH 3.0, as compared to rainfall of approximately pH 5.6. Similar results were observed for one corn cultivar, Pioneer 3377. For one year of the study however, yield of B73 x Mo17 (corn) was reduced 3139 kg ha(-1) by the most severe drought, and an additional 1883 kg ha(-1) by acid rain of pH 3.0, as compared to the control (pH 5.6). Yield reduction from acidic rain was considerably less at full water rates, resulting in a significant pH by drought stress interaction. However, during the second year of the experiment, no pH effect or drought by pH interaction was observed for this cultivar. The reason for the difference in the two years was not identified.

  4. African literature to-day

    Directory of Open Access Journals (Sweden)

    P. Sulzer

    1974-03-01

    Full Text Available Being interested in African literature one seems to swim from the very beginning in a terminological maelstrom. What is African literature? Is it literature written by any African author in any language? That would mean approaching the question from a purely racial basis. It would imply the art of demonstrating that any piece of such literature could infallibly be recognised as African, a thing which, as far as I know has never been done. Or is African literature strictly bound to traditional African culture?

  5. Odd gravitational harmonics of Jupiter: Effects of spherical versus nonspherical geometry and mathematical smoothing of the equatorially antisymmetric zonal winds across the equatorial plane

    Science.gov (United States)

    Kong, Dali; Zhang, Keke; Schubert, Gerald

    2016-10-01

    Unlike the even gravitational coefficients of Jupiter that are caused by both the rotational distortion and the equatorially symmetric zonal winds, the odd jovian gravitational coefficients are directly linked to the depth of the equatorially antisymmetric zonal winds. Accurate estimation of the wind-induced odd coefficients and comparison with measurements of those coefficients would be key to understanding the structure of the zonal winds in the deep interior of Jupiter. We consider two problems in connection with the jovian odd gravitational coefficients. In the first problem, we show, by solving the governing equations for the northern hemisphere of Jupiter subject to an appropriate condition at the equatorial plane, that the effect of non-spherical geometry makes an insignificant contribution to the lowermost-order odd gravitational coefficients. In the second problem, we investigate the effect of the equatorial smoothing used to avoid the discontinuity in the winds across the equatorial plane when the thermal wind equation is adopted to compute the odd gravitational coefficients. We reveal that, because of the dominant effect of the equatorial smoothing, the odd gravitational coefficients so obtained for deep zonal winds do not reflect physically realistic dynamics taking place in the deep interior of Jupiter.

  6. Seasonal-longitudinal variability of equatorial plasma bubbles

    Directory of Open Access Journals (Sweden)

    W. J. Burke

    2004-09-01

    Full Text Available We compare seasonal and longitudinal distributions of more than 8300 equatorial plasma bubbles (EPBs observed during a full solar cycle from 1989-2000 with predictions of two simple models. Both models are based on considerations of parameters that influence the linear growth rate, γRT, of the generalized Rayleigh-Taylor instability in the context of finite windows of opportunity available during the prereversal enhancement near sunset. These parameters are the strength of the equatorial magnetic field, Beq, and the angle, α, it makes with the dusk terminator line. The independence of α and Beq from the solar cycle phase justifies our comparisons.

    We have sorted data acquired during more than 75000 equatorial evening-sector passes of polar-orbiting Defense Meteorological Satellite Program (DMSP satellites into 24 longitude and 12 one-month bins, each containing ~250 samples. We show that: (1 in 44 out of 48 month-longitude bins EPB rates are largest within 30 days of when α=0°; (2 unpredicted phase shifts and asymmetries appear in occurrence rates at the two times per year when α≈0°; (3 While EPB occurrence rates vary inversely with Beq, the relationships are very different in regions where Beq is increasing and decreasing with longitude. Results (2 and (3 indicate that systematic forces not considered by the two models can become important. Damping by interhemispheric winds appears to be responsible for phase shifts in maximum rates of EPB occurrence from days when α=0°. Low EPB occurrence rates found at eastern Pacific longitudes suggest that radiation belt electrons in the drift loss cone reduce γRT by enhancing E-layer Pedersen conductances. Finally, we analyze an EPB event observed during a magnetic storm at a time and place where α≈-27°, to illustrate how electric-field penetration from

  7. Acid rain attack on outdoor sculpture in perspective

    Science.gov (United States)

    Livingston, Richard A.

    2016-12-01

    A major concern motivating research in acid rain materials effects has been the potential for damage to cultural heritage, particularly outdoor marble and bronze sculpture. However, a combination of field and laboratory studies has failed to show a correlation between rain pH and loss of materials. In order to understand this counterintuitive lack of acid rain effect, an aqueous geochemical modeling approach was used to analyze rain runoff chemistry for the relative importance of acid rain neutralization, dry deposition, and in the case of marble, natural carbonate dissolution. This approach involved the development of pH - SO42- phase diagrams for marble (calcium carbonate) and bronze (copper) under ambient environmental conditions. This then enabled reaction path modeling of the acid neutralization process using the pH range typically found in wet deposition (3.5-6). The results were for marble that the theoretical maximum amount of Ca2+ ion that could be lost due acid rain neutralization would be 0.158 mmol/l compared to 10.5 mmol/l by dry deposition, and for bronze, the Cu2+ ion losses would be 0.21 mmol/l and 47.3 mmol/l respectively. Consequently dry deposition effects on these materials have the potential to dominate over wet deposition effects. To test these predictions the geochemical models were applied to examples of data sets from mass balance (runoff vs rainfall) studies on a marble statue in New York City and some bronze memorial plaques at Gettysburg PA. Although these data sets were collected in the early 1980s they remain valid for demonstrating the mass balance method. For the marble statue, the mean Ca2+ losses by dry deposition was about 69% of the total compared 0.3% for acid rain neutralization, which was less than the natural carbonate dissolution losses of 0.8%. For the bronze, the mean Cu2+ losses were 70.6% by SO42- dry deposition and 23% by NO3- dry deposition compared to 6.4% by acid rain neutralization. Thus for both cases the wet

  8. Rain Fade Compensation for Ka-Band Communications Satellites

    Science.gov (United States)

    Mitchell, W. Carl; Nguyen, Lan; Dissanayake, Asoka; Markey, Brian; Le, Anh

    1997-01-01

    This report provides a review and evaluation of rain fade measurement and compensation techniques for Ka-band satellite systems. This report includes a description of and cost estimates for performing three rain fade measurement and compensation experiments. The first experiment deals with rain fade measurement techniques while the second one covers the rain fade compensation techniques. The third experiment addresses a feedback flow control technique for the ABR service (for ATM-based traffic). The following conclusions were observed in this report; a sufficient system signal margin should be allocated for all carriers in a network, that is a fixed clear-sky margin should be typically in the range of 4-5 dB and should be more like 15 dB in the up link for moderate and heavy rain zones; to obtain a higher system margin it is desirable to combine the uplink power control technique with the technique that implements the source information rate and FEC code rate changes resulting in a 4-5 dB increase in the dynamic part of the system margin. The experiments would assess the feasibility of the fade measurements and compensation techniques, and ABR feedback control technique.

  9. [Relationship between simulated acid rain stress and leaf reflectance].

    Science.gov (United States)

    Song, Xiao-dong; Jiang, Hong; Yu, Shu-quan; Zhou, Guo-mo; Jiang, Zi-shan

    2010-01-01

    Acid rain is a worldwide environmental problem. Serious acid rain pollution in subtropical China has constituted a potential threat to the health of the local forest. In the present paper, the changing properties of the chlorophyll concentration and spectral reflectance at the visible wavelengths for the six subtropical broad-leaved tree species leaves under simulated acid rain (SAR) treatment with different pH levels were studied. With the increasing strength of the SAR, the chlorophyll concentrations of the experimental species under pH 2.5 and pH 4.0 treatment were higher than that under pH 5.6; the spectral reflectance at the visible wavelengths for pH 2.5 and pH 4.0 were lower than that for pH 5.6 in general; while there weren't significant differences between pH 2.5 and pH 4.0. After the treatment with different levels of SAR, the differences in spectral reflectance at the visible wavelengths mainly focused around the green peak and red edge on the reflectance curve. The subtropical broad-leaved tree species studied were relatively not sensitive to acid rain stresses; some stronger acid rain may accelerate the growth of the tree species used here to some extent.

  10. Acid rain and its environmental effects: Recent scientific advances

    Science.gov (United States)

    Burns, Douglas A.; Aherne, Julian; Gay, David A.; Lehmann, Christopher M. B.

    2016-12-01

    The term 'acid rain' refers to atmospheric deposition of acidic constituents that impact the earth as rain, snow, particulates, gases, and vapor. Acid rain was first recognized by Ducros (1845) and subsequently described by the English chemist Robert Angus Smith (Smith, 1852) whose pioneering studies linked the sources to industrial emissions and included early observations of deleterious environmental effects (Smith, 1872). Smith's work was largely forgotten until the mid-20th century when observations began to link air pollution to the deposition of atmospheric sulfate (SO42-) and other chemical constituents, first near the metal smelter at Sudbury, Ontario, Canada, and later at locations in Europe, North America, and Australia (Gorham, 1961). Our modern understanding of acid rain as an environmental problem caused largely by regional emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx) stems from observations in the 1960s and early 1970s in Sweden by Svante Odén (Odén, 1976), and in North America by Gene Likens and colleagues (Likens and Bormann, 1974). These scientists and many who followed showed the link to emissions from coal-fired power plants and other industrial sources, and documented the environmental effects of acid rain such as the acidification of surface waters and toxic effects on vegetation, fish, and other biota.

  11. Effects of simulated acid rain on fertility of litchi

    Institute of Scientific and Technical Information of China (English)

    QIU Dong-liang; LIU Xing-hui; GUO Su-zhi

    2005-01-01

    The regulatory role of calcium in fertility of pollen and pistil under simulated acid rein was investigated. The germination percentage of pollen treated with acid rain of pH 4.5 was 9.42% lower than that of control, and that of pH 3.5, pH 2.5 and pH 1.5 were 22.47 %, 45.49% and 71.62%, respectively. Simultaneously, the injury character of pollen was obviously observed when flowers were treated with acid rain of pH 3.5. The difference in fruit setting rate between the female flower treated with acid rain of pH 4.0 and the control was significant at p < 0.05. Ca(NO3 )2 of 0.2-0.4 mmol/L could promote pollen germination under the stress of acid rain. The beneficial function was reduced when calcium concentration surpassed 0.8 mmol/L. Spraying 2 mmol/L Ca(NO3 )2 reduced the injury of acid rain to pistil and increased fruit-setting rate significantly. The physiological importance of calcium during pollen germination and pistil development was also discussed.

  12. Origin of HIV type 1 in colonial French Equatorial Africa?

    Science.gov (United States)

    Chitnis, A; Rawls, D; Moore, J

    2000-01-01

    Sociocultural factors during the postcolonial period have been implicated as paramount in generating conditions that promoted both the origin and subsequent epidemic spread of HIV-1 in Africa. We suggest, however, that the origin of the disease may lie in the interaction between colonial practices (e.g., labor camps, nonsterile vaccination campaigns) and traditional bushmeat hunting in French Equatorial Africa. Both the epidemiology of HIV-2 and the colonial history of West Africa appear more complex, but similar conditions existed there and may have contributed to the origin of HIV-2. Focusing the search for the origins of HIV-1 and HIV-2 on this earlier time period may contribute to understanding the evolution of the HIV viruses and the dynamics of emerging diseases.

  13. Numerical Study on the Bifurcation of the North Equatorial Current

    Institute of Scientific and Technical Information of China (English)

    LIU Yulong; WANG Qi; SONG Jun; ZHU Xiande; GONG Xiaoqing; WU Fang

    2011-01-01

    A 1.5-layer reduced-gravity model forced by wind stress is used to study the bifurcations of the North Equatorial Current (NEC).The authors found that after removing the Ekman drift,the modelled circulations can serve well as a proxy of the SODA circulations on the σθ=25.0kgm-3 potential density surface based on available long-term reanalysis wind stress data.The modelled results show that the location of the western boundary bifurcation of the NEC depends on both zonal averaged and local zero wind stress curl latitude.The effects of the anomalous wind stress curl added in different areas are also investigated and it is found that they can change the strength of the Mindanao Eddy (ME),and then influence the interior pathway.

  14. Unstable density distribution associated with equatorial plasma bubble

    Science.gov (United States)

    Kherani, E. A.; Bharuthram, R.; Singh, S.; Lakhina, G. S.; de Meneses, F. Carlos

    2016-04-01

    In this work, we present a simulation study of equatorial plasma bubble (EPB) in the evening time ionosphere. The fluid simulation is performed with a high grid resolution, enabling us to probe the steepened updrafting density structures inside EPB. Inside the density depletion that eventually evolves as EPB, both density and updraft are functions of space from which the density as implicit function of updraft velocity or the density distribution function is constructed. In the present study, this distribution function and the corresponding probability distribution function are found to evolve from Maxwellian to non-Maxwellian as the initial small depletion grows to EPB. This non-Maxwellian distribution is of a gentle-bump type, in confirmation with the recently reported distribution within EPB from space-borne measurements that offer favorable condition for small scale kinetic instabilities.

  15. Solar Wind Associated with Near Equatorial Coronal Hole

    Indian Academy of Sciences (India)

    M. Hegde; K. M. Hiremath; Vijayakumar H. Doddamani; Shashanka R. Gurumath

    2015-09-01

    Present study probes temporal changes in the area and radiative flux of near equatorial coronal hole associated with solar wind parameters such as wind speed, density, magnetic field and temperature. Using high temporal resolution data from SDO/AIA for the two wave-lengths 193 Å and 211 Å, area and radiative flux of coronal holes are extracted and are examined for the association with high speed solar wind parameters. We find a strong association between different parameters of coronal hole and solar wind. For both the wavelength bands, we also compute coronal hole radiative energy near the earth and it is found to be of similar order as that of solar wind energy. However, for the wavelength 193 Å, owing to almost similar magnitudes of energy emitted by coronal hole and energy due to solar wind, it is conjectured that solar wind might have originated around the same height where 193 Å line is formed in the corona.

  16. Equatorially trapped convection in a rapidly rotating spherical shell

    Science.gov (United States)

    Miquel, Benjamin; Julien, Keith; Knobloch, Edgar

    2016-11-01

    Convection plays a preponderant role in driving geophysical flows. Unfortunately, these flows are often characterized by rapid rotation (i.e. small Ekman number E) which renders the equations stiff and introduces a scale separation in the system: for example the wavelength of the marginal mode at the onset of convection in a rapidly rotating sphere scales like E 1 / 3 and is modulated by a E 1 / 6 envelope. These scalings keep the fully nonlinear dynamics of the internal convection in Earth's core (E 1015) out of reach from direct numerical simulations, analytical work and experiments on one hand, but advocate for the development of reduced models on the other hand. We present a reduced model derived in a shallow gap spherical shell geometry. As the Rayleigh number is increased, the flow is first destabilized in the equatorial region where the dynamics remains trapped. The linear stability is analyzed and the fully nonlinear dynamics is presented.

  17. The earth's equatorial principal axes and moments of inertia

    Science.gov (United States)

    Liu, H. S.; Chao, B. F.

    1991-01-01

    The earth's equatorial principal moments of inertia are given as A and B, where A is less than B, and the corresponding principal axes are given as a and b. Explicit formulas are derived for determining the orientation of a and b axes and the difference B - A using C(22) and S(22), the two gravitational harmonic coefficients of degree 2 and order 2. For the earth, the a axis lies along the (14.93 deg W, 165.07 deg E) diameter, and the b axis lies perpendicular to it along the (75.07 deg E, 104.93 deg W) diameter. The difference B - A is 7.260 x 10 to the -6th MR2. These quantities for other planets are contrasted, and geophysical implications are discussed.

  18. Combined radar observations of equatorial electrojet irregularities at Jicamarca

    Directory of Open Access Journals (Sweden)

    D. L. Hysell

    2007-03-01

    Full Text Available Daytime equatorial electrojet plasma irregularities were investigated using five distinct radar diagnostics at Jicamarca including range-time-intensity (RTI mapping, Faraday rotation, radar imaging, oblique scattering, and multiple-frequency scattering using the new AMISR prototype UHF radar. Data suggest the existence of plasma density striations separated by 3–5 km and propagating slowly downward. The striations may be caused by neutral atmospheric turbulence, and a possible scenario for their formation is discussed. The Doppler shifts of type 1 echoes observed at VHF and UHF frequencies are compared and interpreted in light of a model of Farley Buneman waves based on kinetic ions and fluid electrons with thermal effects included. Finally, the up-down and east-west asymmetries evident in the radar observations are described and quantified.

  19. Longitudinal and geomagnetic activity modulation of the equatorial thermosphere anomaly

    Science.gov (United States)

    Lei, Jiuhou; Thayer, Jeffrey P.; Forbes, Jeffrey M.

    2010-08-01

    In this paper we examine the detailed similarities and differences between the equatorial thermosphere anomaly (ETA) and the equatorial ionization anomaly (EIA) from 20 March to 6 April 2002, when both the ETA and the EIA are distinct in the Challenging Minisatellite Payload (CHAMP) observations. The characteristics of the ETA and the EIA are obtained from the CHAMP accelerometer, in situ electron density measurements, and total electron content (TEC) above the CHAMP satellite. Our results show that the trough locations of the ETA and the EIA in latitude show a good agreement, and both correspond well with the dip magnetic equator, while the ETA crests are usually located poleward of the EIA. Meanwhile, the latitudinal locations of the ETA crests exhibit strong hemispheric asymmetry and large variability during our study interval. The longitudinal variations between the EIA and the ETA show significant differences. The EIA crests from the CHAMP observations show strong wave 4 structures, but the primary component in the ETA is wave 1. Moreover, the ETA densities show strong variations in response to geomagnetic activity, whereas CHAMP in situ electron densities and TEC at the EIA do not reflect such large day-to-day variability. Therefore, a simple EIA-ETA relationship cannot explain the dependence of the longitudinal and geomagnetic activity modulation of the ETA and the EIA. The meridional ion drag, which is significantly modulated by enhanced equatorward winds during elevated geomagnetic activity, is probably responsible for some of the observed features in the ETA, although no unambiguous explanation for ETA formation yet exists.

  20. BeppoSAX equatorial uncontrolled re-entry

    Science.gov (United States)

    Portelli, C.

    The X-ray astronomy satellite BeppoSAX (Satellite per Astronomia X, "Beppo" in honor of Giuseppe Occhialini), is a project of the Italian Space Agency (ASI) with participation of the Netherlands Agency for Aerospace Programs (NIVR). BeppoSAX was launched by an Atlas G Centaur directly into a circular 600 km- orbit at 3.9 degrees inclination on April 30th, 1996. The satellite is a three axis stabilized spacecraft with a total mass of about 1400 kg. The current (May 1, 2002) flight altitude is about 470 km and its uncontrolled re-entry is predicted late in 2002, or in 2003, with a 26 kg of hydrazine on board that could not be vented or used for controlled re-entry due to gyro's package total failure. Due to the relatively high mass of BeppoSAX, it has to be expected that parts of the satellite will survive the re-entry into the earth atmosphere. The Italian Space Agency has committed a study to HTG for the analysis of the destructive phase of the uncontrolled atmospheric re-entry by means of a dedicated European software tool (SCARAB). The expected outputs will be used in order to determine how much of the spacecraft and how many fragments parts of it will reach the ground on the equatorial earth zone. This paper will address the peculiarities of the spacecraft initial status, its risks at end of life and the SCARAB modelling as well as its 6D flight dynamics re-entry analysis results also in terms of the destruction history tree. Consideration will be made on the ground dispersion and casualt y area due to the very restricted equatorial zone impacted. References B. Fritsche, H. Klinkrad, A. Kashkovsky, E.Grinberg; Spacecraft Disintegration during uncontrolled atmospheric entry ; IAA-99-IAA.6.7.02; 50t h IAC 4-8 Oct. 1999

  1. Ternary fission of {sup 260}No in equatorial configuration

    Energy Technology Data Exchange (ETDEWEB)

    Ismail, M.; Seif, W.M.; Hashem, A.S. [Faculty of Science, Department of Physics, Cairo University, Giza (Egypt)

    2016-10-15

    Spontaneous ternary fission is one of the observed decay modes of heavy nuclei. We systematically investigate the equatorial ternary fission of the {sup 260}No isotope. In the framework of the three-cluster model, the three-body interaction potential is calculated in terms of the folded M3Y-Reid nucleon-nucleon force and the Coulomb one. The relative orientations of the deformed heavy nuclei participating in the fragmentation process are taken into account. All possible emitted light particles with even mass numbers A = 4-52 are considered. The favored fragmentation channels are estimated as the ones characterized with peaks in the Q-value and local minima in the fragmentation potential. In the absence of nuclear deformations, the closed shell effects are found to play the key role in determining the channels of minimum fragmentation potential and the involved two heavier fragments tend to be of comparable sizes. Inclusion of nuclear deformations manifest the participation of highly deformed prolate nuclei, with large mass asymmetry, as heavy fragment partners in the estimated favored fragmentation channels. The results indicate that the equatorial ternary fission of {sup 260}No is most favored with the light emitted nuclei {sup 4,6,8}{sub 2}He and {sup 10}{sub 4}Be through the fragmentation channels {sup 155}{sub 60}Nd + {sup 4}{sub 2}He + {sup 101}{sub 40}Zr, {sup 153}{sub 60}Nd + {sup 6}{sub 2}He + {sup 101}{sub 40}Zr, {sup 152}{sub 60}Nd + {sup 8}{sub 2}He + {sup 100}{sub 40}Zr, and {sup 152}{sub 60}Nd + {sup 10}{sub 4}Be + {sup 98}{sub 38}Sr, respectively. (orig.)

  2. African-Americans and Alzheimer's

    Science.gov (United States)

    ... Share Plus on Google Plus African-Americans and Alzheimer's alz.org | IHaveAlz Introduction 10 Warning Signs Brain ... African-Americans are at a higher risk for Alzheimer's disease. Many Americans dismiss the warning signs of ...

  3. Mental Health and African Americans

    Science.gov (United States)

    ... Minority Population Profiles > Black/African American > Mental Health Mental Health and African Americans Poverty level affects mental health ... compared to 120% of non-Hispanic whites. 1 MENTAL HEALTH STATUS Serious psychological distress among adults 18 years ...

  4. New biology of red rain extremophiles prove cometary panspermia

    CERN Document Server

    Louis, G; Louis, Godfrey

    2003-01-01

    This paper reports the extraordinary biology of the microorganisms from the mysterious red rain of Kerala, India. These chemosynthetic organisms grow optimally at an extreme high temperature of 300 degrees C in hydrothermal conditions and can metabolize inorganic and organic compounds including hydrocarbons. Stages found in their life cycle show reproduction by a special multiple fission process and the red cells found in the red rain are identified as the resting spores of these microbes. While these extreme hyperthermophiles contain proteins, our study shows the absence of DNA in these organisms, indicating a new primitive domain of life with alternate thermostable genetics. This new biology proves our earlier hypothesis that these microbes are of extraterrestrial origin and also supports our earlier argument that the mysterious red rain of Kerala is due to the cometary delivery of the red spores into the stratosphere above Kerala.

  5. Statistical Prediction of Heavy Rain in South Korea

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    This study is aimed at the development of a statistical model for forecasting heavy rain in South Korea. For the 3-hour weather forecast system, the 10 km× 10 km area-mean amount of rainfall at 6 stations (Seoul, Daejeon, Gangreung, Gwangju, Busan, and Jeju) in South Korea are used. And the corresponding 45 synoptic factors generated by the numerical model are used as potential predictors. Four statistical forecast models (linear regression model, logistic regression model, neural network model and decision tree model) for the occurrence of heavy rain are based on the model output statistics (MOS) method. They are separately estimated by the same training data. The thresholds are considered to forecast the occurrence of heavy rain because the distribution of estimated values that are generated by each model is too skewed.The results of four models are compared via Heidke skill scores. As a result, the logistic regression model is recommended.

  6. African Cultural Astronomy

    CERN Document Server

    Holbrook, Jarita C; Medupe, R. Thebe; Current Archaeoastronomy and Ethnoastronomy research in Africa

    2008-01-01

    Astronomy is the science of studying the sky using telescopes and light collectors such as photographic plates or CCD detectors. However, people have always studied the sky and continue to study the sky without the aid of instruments this is the realm of cultural astronomy. This is the first scholarly collection of articles focused on the cultural astronomy of Africans. It weaves together astronomy, anthropology, and Africa. The volume includes African myths and legends about the sky, alignments to celestial bodies found at archaeological sites and at places of worship, rock art with celestial imagery, and scientific thinking revealed in local astronomy traditions including ethnomathematics and the creation of calendars. Authors include astronomers Kim Malville, Johnson Urama, and Thebe Medupe; archaeologist Felix Chami, and geographer Michael Bonine, and many new authors. As an emerging subfield of cultural astronomy, African cultural astronomy researchers are focused on training students specifically for do...

  7. Experimental wind-driven rain erosion study on agricultural soils

    Science.gov (United States)

    Marzen, Miriam; Iserloh, Thomas; Brings, Christine; Fister, Wolfgang; Seeger, Manuel; Ries, Johannes B.

    2014-05-01

    Wind is potentially capable to considerably increase soil erosion by rain drops. In contrast to laboratory experiments, in-situ experiments enable the measurement of soil erosion by wind and rain including the reactions of relatively intact soil surfaces and a complete body of soil. The Portable Wind and Rainfall Simulator of Trier University was applied on winter cereal fields to measure rain erosion on agricultural areas with and without the influence of wind. The test areas are situated near Pamplona, Navarre and recognized to be representative for large parts of northern Spain concerning soil, land use and climate. The soil surfaces on the fields were ploughed and sparsely covered by recently sowed winter cereals. The soil water content was close to saturation due to long lasting rainfall. Runoff was medium to high with runoff-coefficients ranging from 26 to 100%. The eroded material from rainfall simulations ranged from 14.5 to 42.5 g m² / 30min. The eroded material from wind-driven rain ranged from 28.1 to 47.3 g m² / 30 min. Compared to windless rainfall, the wind-driven rain increased erosion of soil material up to 82.2%. In one case, the eroded material decreased by 18.3%. The results indicate a strong influence of wind on rain erosion on recently seeded agricultural soils. Wind influence can be an important aspect for the general assessment of sheet erosion and supports the finding that a neglect of this factor might lead to severe underestimation of soil loss.

  8. English as an African Language.

    Science.gov (United States)

    Desai, Gaurav

    1993-01-01

    Discusses the role of the English language in postcolonial African literature, focusing on the politics of language, "Africanized" English, and the social languages used in Chinua Achebe's novels and concludes that English today is as much an African language as a British or American one. (Contains 37 references.) (MDM)

  9. African names for American plants

    NARCIS (Netherlands)

    Andel, van T.R.

    2015-01-01

    African slaves brought plant knowledge to the New World, sometimes applying it to related plants they found there and sometimes bringing Old World plants with them. By tracing the linguistic parallels between names for plants in African languages and in communities descended from African slaves, pie

  10. The Struggles over African Languages

    Science.gov (United States)

    Maseko, Pam; Vale, Peter

    2016-01-01

    In this interview, African Language expert Pam Maseko speaks of her own background and her first encounter with culture outside of her mother tongue, isiXhosa. A statistical breakdown of South African languages is provided as background. She discusses Western (originally missionary) codification of African languages and suggests that this approach…

  11. Day-to-day variability of Equatorial Ionization Anomaly over the Indian and Brazilian sectors - the role of Equatorial Electrojet

    Science.gov (United States)

    Kavutarapu, Venkatesh; Gende, Mauricio; Fagundes, Paulo Roberto; De Jesus, Rodolfo; Denardini, Clezio Marcos; De Abreu, Alessandro

    2016-07-01

    The equatorial electrojet (EEJ) is a narrow band of current flowing eastward at the ionospheric E-region altitudes along the dayside dip equator. Mutually perpendicular electric and magnetic fields over the equator results in the formation of Equatorial Ionization Anomaly (EIA) which in turn generates large electron density variabilities. Simultaneous study on the characteristics of EEJ and EIA is necessary to understand the role of EEJ on the EIA variabilities. Present study reports simultaneous variations of EEJ and GPS-TEC over Indian and Brazilian sectors to understand the role of EEJ on the day-to-day characteristics of the EIA. Magnetometer measurements during the low solar activity year 2004 are used to derive the EEJ values over the two different sectors. The characteristics of EIA are studied using two different chains of GPS receivers along the common meridian of 770E (India) and 450W (Brazil). The diurnal, seasonal and day-to-day variations of EEJ and TEC are described simultaneously. Variations of EIA during different seasons are presented along with the variations of the EEJ in the two hemispheres. The role of EEJ variations on the characteristic features of the EIA such as the strength and temporal extent of the EIA crest etc., have also been reported. Further, the time delay between the occurrences of the day maximum EEJ and the well-developed EIA are studied and corresponding results are presented in this paper. Further, the results from a study on the noon time bite-outs at the anomaly crest locations with their absence over the equator in the Indian and Brazilian sector are also discussed in this paper.

  12. African agricultural trade

    DEFF Research Database (Denmark)

    Jensen, Hans Grinsted; Sandrey, Ron

    2015-01-01

    This article starts with a profile of African agricultural trade. Using the pre-release version 9.2 of the GTAP database, we then show that the results for tariff elimination on intra-African trade are promising, but these tariff barriers are not as significant as the various trade-related barriers...... outside of tariffs. Impressive results were forecast by simulating both a 50% reduction in what can be considered traditional non-tariff barriers and a modest 20% reduction in the costs associated with transit time delays at customs, terminals and internal land transportation. Gains from tariff...

  13. Ostwald ripening and the kinetics of rain initiation

    CERN Document Server

    Wilkinson, Michael

    2011-01-01

    A central problem in cloud physics is understanding the kinetics of the growth of water droplets. It is believed that there exists a 'condensation-coalescence bottleneck' in the growth of intermediate size droplets. Here the Lifshitz-Slezov theory of Ostwald ripening is applied to the kinetics of the growth of rain drops. The analysis shows that kinetic barriers to rain initiation are not significant. It is also shown that Ostwald ripening can greatly enhance the apparent collision efficiency of droplets falling under gravity.

  14. Summer rains in northeast Bangladesh: Onset and triggering mechanisms

    OpenAIRE

    Ssemujju, Musa

    2016-01-01

    The aim of this study is to shed light on convective triggering mechanisms around the onset of the summer rains in Northeast Bangladesh. We want to understand this rainfall since it has a large impact on the local climate, and because 25.3% of the annual rainfall in Northeast Bangladesh falls in Bangladesh summer (March - May). To do this, we first identified the onset of the summer rains for each year using Sylhet station rainfall data with a 11 mm/day pentad rainfall mean threshold and a 6-...

  15. Ocean dynamics, not dust, have controlled equatorial Pacific productivity over the past 500,000 years

    Science.gov (United States)

    Winckler, Gisela; Anderson, Robert F.; Jaccard, Samuel L.; Marcantonio, Franco

    2016-05-01

    Biological productivity in the equatorial Pacific is relatively high compared with other low-latitude regimes, especially east of the dateline, where divergence driven by the trade winds brings nutrient-rich waters of the Equatorial Undercurrent to the surface. The equatorial Pacific is one of the three principal high-nutrient low-chlorophyll ocean regimes where biological utilization of nitrate and phosphate is limited, in part, by the availability of iron. Throughout most of the equatorial Pacific, upwelling of water from the Equatorial Undercurrent supplies far more dissolved iron than is delivered by dust, by as much as two orders of magnitude. Nevertheless, recent studies have inferred that the greater supply of dust during ice ages stimulated greater utilization of nutrients within the region of upwelling on the equator, thereby contributing to the sequestration of carbon in the ocean interior. Here we present proxy records for dust and for biological productivity over the past 500 ky at three sites spanning the breadth of the equatorial Pacific Ocean to test the dust fertilization hypothesis. Dust supply peaked under glacial conditions, consistent with previous studies, whereas proxies of export production exhibit maxima during ice age terminations. Temporal decoupling between dust supply and biological productivity indicates that other factors, likely involving ocean dynamics, played a greater role than dust in regulating equatorial Pacific productivity.

  16. The streaming-trapped ion interface in the equatorial inner magnetosphere

    Science.gov (United States)

    Lin, J.; Horwitz, J. L.; Gallagher, D.; Pollock, C. J.

    1994-01-01

    Spacecraft measurements of core ions on L=4-7 field-lines typically show trapped ion distributions near the magnetic equator, and frequently indicate field-aligned ion streams at higher latitudes. The nature of the transition between them may indicate both the microphysics of hot-cold plasma interactions and overall consequences for core plasma evolution. We have undertaken a statistical analysis and characterization of this interface and its relation to the equatorial region of the inner magnetosphere. In this analysis, we have characterized such features as the equatorial ion flux anisotropy, the penetration of field-aligned ionospheric streams into the equatorial region, the scale of the transition into trapped ion populations, and the transition latitude. We found that most transition latitudes occur within 13 deg of the equator. The typical values of equatorial ion anisotropies are consistent with bi-Maxwellian temperature ratios of T(sub perpendicular)/T(sub parallel) in the range of 3-5. The latitudinal scales for the edges of the trapped ion populations display a rather strong peak in the 2-3 deg range. We also found that there is a trend for the penetration ratio, the anisotropy half width, and the transition scale length to decrease with a higher equatorial ion anisotropy. We may interpret these features in terms of Liouville mapping of equatorially trapped ions and the reflection of the incoming ionospheric ion streams from the equatorial potential peaks associated with such trapped ions.

  17. Considerations of variations in ionospheric field effects in mapping equatorial lithospheric Magsat magnetic anomalies

    Science.gov (United States)

    Ravat, D.; Hinze, W. J.

    1993-01-01

    The longitudinal, seasonal, and altitude-dependent variability of the magnetic field in equatorial latitudes is investigated to determine the effect of these variabilities on the isolation of lithospheric Magsat magnetic anomalies. It was found that the amplitudes of the dawn dip-latitude averages were small compared to the dusk averages, and that they were of the opposite sign. The longitudinal variation in the equatorial amplitudes of the dawn dip-latitude averages was not entirely consistent with the present knowledge of the electrojet field. Based on the results, a procedure is implemented for reducing the equatorial ionospheric effects from the Magsat data on the lithospheric component.

  18. Variable influence on the equatorial troposphere associated with SSW using ERA-Interim

    Indian Academy of Sciences (India)

    Sourabh Bal; Semjon Schimanke; Thomas Spangehl; Ulrich Cubasch

    2017-03-01

    Sudden stratospheric warming (SSW) events are identified to investigate their influence on the equatorial tropospheric climate. Composite analysis of warming events from Era-Interim (1979–2013) record a cooling of the tropical lower stratosphere with corresponding changes in the mean meridional stratosphericcirculation. A cooling of the upper troposphere induces enhanced convective activity near the equatorial region of the Southern Hemisphere and suppressed convective activity in the off-equatorial Northern Hemisphere. After selecting vortex splits, the see-saw pattern of convective activity in the tropospheregrows prominent and robust.

  19. Periodic Structure of Equatorial Envelope Rossby Wave Under Influence of Diabatic Heating

    Institute of Scientific and Technical Information of China (English)

    FUZun-Tao; CHENZhe; LIUShi-Da; LIUShi-Kuo

    2004-01-01

    A simple shallow-water model with influence of diabatic heating on a β-plane is applied to investigate the nonlinear equatorial Rossby waves in a shear flow. By the asymptotic method of multiple scales, the cubic nonlinear Schroedinger (NLS for short) equation with an external heating source is derived for large amplitude equatorial envelope Rossby wave in a shear flow. And then various periodic structures for these equatorial envelope Rossby waves are obtained with the help of Jacob/elliptic functions and elliptic equation. It is shown that phase-locked diabatic heating plays an important role in periodic structures of rational form.

  20. Periodic Structure of Equatorial Envelope Rossby Wave Under Influence of Diabatic Heating

    Institute of Scientific and Technical Information of China (English)

    FU Zun-Tao; CHEN Zhe; LIU Shi-Da; LIU Shi-Kuo

    2004-01-01

    A simple shallow-water model with influence of diabatic heating on aβ-plane is applied to investigate the nonlinear equatorial Rossby waves in a shear flow. By the asymptotic method of multiple scales, the cubic nonlinear Schrodinger (NLS for short) equation with an external heating source is derived for large amplitude equatorial envelope Rossby wave in a shear flow. And then various periodic structures for these equatorial envelope Rossby waves are obtained with the help of Jacobi elliptic functions and elliptic equation. It is shown that phase-locked diabatic heating plays an important role in periodic structures of rational form.

  1. East African institutions

    DEFF Research Database (Denmark)

    Nordby, Johannes Riber; Jacobsen, Katja

    For the past decade security in East Africa has gained focus internationally. However there is a growing ambition among African states to handle such issues by themselves, sometimes through regional institutions. This has been supported by many Western states but potential risks are often forgotten....

  2. African Oral Tradition Literacy.

    Science.gov (United States)

    Green, Doris

    1985-01-01

    Presents the basic principles of two systems for notating African music and dance: Labanotation (created to record and analyze movements) and Greenotation (created to notate musical instruments of Africa and to parallel Labanotation whereby both music and dance are incorporated into one integrated score). (KH)

  3. African Women Writing Resistance

    Institute of Scientific and Technical Information of China (English)

    Jennifer Browdy de Hernandez; Pauline Dongala; Omotayo; Jolaosho; Anne Serafin

    2011-01-01

    AFRICAN Women Writing Resistance is the first transnational anthology to focus on women's strategies of resistance to the challenges they face in Africa today.The anthology brings together personal narratives,testimony,interviews,short stories,poetry,performance scripts,folktales and lyrics.

  4. African tick bite fever

    DEFF Research Database (Denmark)

    Johansen, Jakob Aaquist; Thybo, Søren

    2011-01-01

    The incident of spotted fever imported to Denmark is unknown. We present a classic case of African Tick Bite Fever (ATBF) to highlight a disease, which frequently infects wildlife enthusiasts and hunters on vacation in South Africa. ATBF has a good prognosis and is easily treated with doxycyclin...

  5. A meteorological potential forecast model for acid rain in Fujian Province, China.

    Science.gov (United States)

    Cai, Yi Yong; Lin, Chang Cheng; Liu, Jing Xiong; Wu, De Hui; Lian, Dong Ying; Chen, Bin Bin

    2010-05-01

    Based on the acid rain and concurrent meteorological observational data during the past 10 years in Fujian Province, China, the dependence of distribution characteristics of acid rain on season, rain rate, weather pattern and dominant airflow in four regions of Fujian Province is analyzed. On the annual average, the acid rain frequency is the highest (above 40%) in the southern and mid-eastern regions, and the lowest (16.2%) in the western region. The acid rain occurs most frequently in spring and winter, and least frequent in summer. The acid rain frequency in general increases with the increase of precipitation. It also depend on the direction of dominant airflows at 850 hPa. In the mid-eastern region, more than 40% acid rains appear when the dominant wind directions are NW, W, SW, S and SE. In the southern region, high acid rain occurrence happens when the dominant wind directions are NW, W, SW and S. In the northern region, 41.8% acid rains occur when the southwesterly is pronounced. In the western region, the southwesterly is associated with a 17% acid rain rate. The examination of meteorological sounding conditions over Fuzhou, Xiamen and Shaowu cities shows that the acid rain frequency increases with increased inversion thickness. Based on the results above, a meteorological potential forecast model for acid rain is established and tested in 2007. The result is encouraging. The model provides an objective basis for the development of acid rain forecasting operation in the province.

  6. Iapetus' Geophysics: Rotation Rate, Shape, and Equatorial Ridge

    Science.gov (United States)

    Castillo-Rogez, J. C.; Matson, D. L.; Sotin, C.; Johnson, T. V.; Lunine, J. I.; Thomas, P. C.

    2007-01-01

    Iapetus has preserved evidence that constrains the modeling of its geophysical history from the time of its accretion until now. The evidence is (a) its present 79.33-day rotation or spin rate, (b) its shape that corresponds to the equilibrium figure for a hydrostatic body rotating with a period of approximately 16 h, and (c) its high, equatorial ridge, which is unique in the Solar System. This paper reports the results of an investigation into the coupling between Iapetus' thermal and orbital evolution for a wide range of conditions including the spatial distributions with time of composition, porosity, short-lived radioactive isotopes (SLRI), and temperature. The thermal model uses conductive heat transfer with temperature-dependent conductivity. Only models with a thick lithosphere and an interior viscosity in the range of about the water ice melting point can explain the observed shape. Short-lived radioactive isotopes provide the heat needed to decrease porosity in Iapetus? early history. This increases thermal conductivity and allows the development of the strong lithosphere that is required to preserve the 16-h rotational shape and the high vertical relief of the topography. Long-lived radioactive isotopes and SLRI raise internal temperatures high enough that significant tidal dissipation can start, and despin Iapetus to synchronous rotation. This occurred several hundred million years after Iapetus formed. The models also constrain the time when Iapetus formed because the successful models are critically dependent upon having just the right amount of heat added by SLRI decay in this early period. The amount of heat available from short-lived radioactivity is not a free parameter but is fixed by the time when Iapetus accreted, by the canonical concentration of Al-26, and, to a lesser extent, by the concentration of Fe-60. The needed amount of heat is available only if Iapetus accreted between 2.5 and 5.0Myr after the formation of the calcium aluminum

  7. Investigation of plasma motion in the equatorial ionosphere

    Science.gov (United States)

    Oyekola, Oyedemi S.

    2016-07-01

    The structure of evening and nighttime F-region vertical drift component of is vital for understanding the physics of the development of the occurrence of equatorial irregularities. In addition, postsunset ionospheric height has also been attributed as one of the most important factors for the occurrence of equatorial irregularities. We report vertical plasma drift velocities derived from the base (h'F) and the peak height (hmF2) of F-layer using 1-year of data obtained at Ibadan (Geog Long 3.9oE) during International Geophysical Year (1957-58) period for geomagnetic quiet-time and high solar activity conditions. We compared our results with International Reference Ionosphere 2012 model (IRI-2012). The results of this investigation include: (a) overall local- time characteristics of vertical drift between 1800 LT and 0600 LT are in good agreement for equinoxes, December, and June; (b) annual vertical drift derived from time variation of h'F and hmF2 and the corresponding annual variation of h'F and hmF2 variation indicate low correlation (R = 0.30), while IRI-2012 model vertical drift and IRI-2012 model of hmF2 show fairly good correlation ( R = 0.67); (c) regression analysis between time variation of h'F and Scherliess / Fejer model demonstrate correlation coefficient of approximately 0.74 (equinox), 0.85 (December), 0.57 (June) and 0.74 (all-year), while that of time variation of hmF2 and IRI-2012 vertical velocities show 0.95 (equinox), 0.74 (December), 0.43 (June), and 0.74 (all-year); (d) plasma motion derived from the time rate of change of h'F and those of hmF2 are correlated at 0.94, 0.88, 0.63, and 0.90 for equinoxes, December, June, and all-year, respectively; (e) the evening prereversal vertical drifts enhancement rage between ~20 - 45 m/s, ~18 - 46 m/s, ~20 - 50 m/s for time variation of h'F, hmF2, and Scherliess / Fejer model, respectively; (f) the corresponding peak altitudes vary between 430 - 540 km (h'F), 560 - 740 km ( hmF2), and 570 - 620 km (IRI

  8. On the hierarchy of processes contributing to equatorial spread F

    Science.gov (United States)

    Hysell, David Lee

    Unstable plasma stratification in the twilight equatorial F region ionosphere is subject to plasma instabilities known collectively as equatorial spread F. Small-scale irregularities in electron density give rise to coherent VHF and UHF radio scatter during spread F while in situ spacecraft detect intermediate- and large-scale plasma structures. We present data from observations made over three years at the Jicamarca Radio Observatory and from the summer 1990 CRRES/EQUIS campaign which involved the Cornell 50 MHz radar interferometer (CUPRI) and the Altair UHF radar at Kwajalein, MI. Radar findings are correlated with spread F data from sounding rockets launched during the EQUIS project and from the Atmospheric Explorer E satellite. A review of fundamental fluid theory for the ionospheric interchange instability emphasizes dissipative and non-local effects that restrict linear instability to intermediate-scale wavelengths. A nonlinear fluid theory incorporating three wave interactions extends the range of instability to transitional and small scales, and renormalization group analysis offers a way to evaluate enhanced transport due to these nonlinearly excited modes. At large scales, circumstantial evidence suggests that internal gravity waves seed plasma upwellings and initiate topside spread F. Density and electric field spectra measured by the spread F sounding rockets exhibit inertial-convective and inertial-diffusive subranges. A model of quasi one-dimensional plasma turbulence reproduces the spectral indices and breaking scales observed by the rockets. Density power spectra from 30 AE-E orbits also possess convective and diffusive subranges, but their characteristic scale sizes are about 10 times larger than the rocket's. One-dimensional rocket and satellite power spectra combine to form a two-dimensional spectral model of F region irregularities which predicts VHF radar scattering cross-sections. Seeking predictions for bottomside spread F coherent scatter

  9. O the Hierarchy of Processes Contributing to Equatorial Spread F

    Science.gov (United States)

    Hysell, David Lee

    Unstable plasma stratification in the twilight equatorial F region ionosphere is subject to plasma instabilities known collectively as equatorial spread F. Small-scale irregularities in electron density give rise to coherent VHF and UHF radio scatter during spread F while in situ spacecraft detect intermediate- and large-scale plasma structures. We present data from observations made over three years at the Jicamarca Radio Observatory and from the summer 1990 CRRES/EQUIS campaign which involved the Cornell 50 Mhz radar interferometer (CUPRI) and the Altair UHF radar at Kwajalein, MI. Radar findings are correlated with spread F data from sounding rockets launched during the EQUIS project and from the Atmospheric Explorer E satellite. A review of fundamental fluid theory for the ionospheric interchange instability emphasizes dissipative and non -local effects that restrict linear instability to intermediate -scale wavelengths. A nonlinear fluid theory incorporating three wave interactions extends the range of instability to transitional and small scales, and renormalization group analysis offers a way to evaluate enhanced transport due to these nonlinearly excited modes. At large scales, circumstantial evidence suggests that internal gravity waves seed plasma upwellings and initiate topside spread F. Density and electric field spectra measured by the spread F sounding rockets exhibit inertial-convective and inertial-diffusive subranges. A model of quasi one -dimensional plasma turbulence reproduces the spectral indices and breaking scales observed by the rockets. Density power spectra from 30 AE-E orbits also possess convective and diffusive subranges, but their characteristic scale sizes are about 10 times larger than the rocket's. One-dimensional rocket and satellite power spectra combine to form a two -dimensional spectral model of F region irregularities which predicts VHF radar scattering cross-sections. Seeking predictions for bottomside spread F coherent

  10. Priority areas for large mammal conservation in Equatorial Guinea.

    Directory of Open Access Journals (Sweden)

    Mizuki Murai

    Full Text Available Hunting is one of the main driving forces behind large mammal density distribution in many regions of the world. In tropical Africa, urban demand for bushmeat has been shown to dominate over subsistence hunting and its impact often overrides spatial-ecological species characteristics. To effectively protect remaining mammal populations the main factors that influence their distribution need to be integrated into conservation area prioritisation and management plans. This information has been lacking for Río Muni, Equatorial Guinea, as prior studies have been outdated or have not systematically covered the continental region of the country. In this study we evaluated: 1 the relative importance of local vs. commercial hunting; 2 wildlife density of protected vs. non-protected areas; and 3 the importance of ecological factors vs. human influence in driving mammal density distribution in Río Muni. We adopted a systematic countrywide line transect approach with particular focus on apes and elephants, but also including other mammal species. For analysis of field data we used generalised linear models with a set of predictor variables representing ecological conditions, anthropogenic pressure and protected areas. We estimate that there are currently 884 (437-1,789 elephants and 11,097 (8,719-13,592 chimpanzees and gorillas remaining in Río Muni. The results indicate strong hunting pressures on both local and commercial levels, with roads demonstrating a negative impact on elephants and overall mammal body mass. Protected areas played no role in determining any of the mammal species distributions and significant human hunting signs were found inside these protected areas, illustrating the lack of environmental law enforcement throughout the country. Río Muni is currently under-represented in conservation efforts in Western Equatorial Africa, and we recommend a focus on cross-boundary conservation, in particular in the Monte Alén-Monts de Cristal

  11. Light Reflection from Water Surfaces Perturbed by Falling Rain Droplets

    Science.gov (United States)

    Molesini, Giuseppe; Vannoni, Maurizio

    2009-01-01

    An account of peculiar light patterns produced by reflection in a pool under falling rain droplets was recently reported by Molesini and Vannoni (2008 Eur. J. Phys. 29 403-11). The mathematical approach, however, only covered the case of a symmetrical location of a light source and the observer's eyes with respect to the vertical of the falling…

  12. Splash : the dispersal of fungal plant pathogens in rain events

    NARCIS (Netherlands)

    Pielaat, A.

    2000-01-01

    Models were developed to study splash dispersal of fungal plant pathogens in space and time. The models incorporate the main mechanisms involved in splash dispersal, that is 1. A raindrop hits the thin water film on the crop surface containing spores and spores are dispersed in the splashing rain dr

  13. Prosthesis, Surrogation, and Relation in Arturo Islas's "The Rain God"

    Science.gov (United States)

    Cutler, John Alba

    2008-01-01

    This essay seeks to intervene in critical discussions about Arturo Islas's 1984 novel "The Rain God", as well as to suggest the potential for synthesizing discourses heretofore deployed in disparate conversations about disability, sexuality, and ethnicity. I first demonstrate how the novel's queer characters, Miguel Chico and Felix, pose critical…

  14. Canopy dynamics of a tropical rain forest in French Guiana.

    NARCIS (Netherlands)

    Meer, van der P.J.

    1995-01-01

    The canopy dynamics (i.e. the formation and closure of canopy gaps) of a tropical rain forest in French Guiana are described. The formation of canopy gaps is investigated. The difficulties with gap size measurements are studied, and causes and consequences of treefalls and branchfalls are examined.

  15. Household response to environmental incentives for rain garden adoption

    Science.gov (United States)

    Newburn, David A.; Alberini, Anna

    2016-02-01

    A decentralized approach to encourage the voluntary adoption of household stormwater management practices is increasingly needed to mitigate urban runoff and to comply with more stringent water quality regulations. We analyze the household response to a hypothetical rebate program to incentivize rain garden adoption using household survey data from the Baltimore-Washington corridor. We asked respondents whether the household would adopt a rain garden without a rebate or when offered a randomly assigned rebate. An interval-data model is used to estimate household demand on the willingness to pay (WTP) for a rain garden as a function of demographic factors, gardening activities, environmental attitudes, and other household characteristics. Estimation results indicate that mean WTP for a rain garden in our sample population is approximately $6.72 per square foot, corresponding to almost three-fourths of the installation cost. The expected adoption rate more than tripled when comparing no rebate versus a government rebate set at one-third of the installation cost, indicating that economic incentives matter. There is substantial heterogeneity in the WTP among households. Higher levels of WTP are estimated for households with higher environmental concern for the Chesapeake Bay and local streams, garden experience, higher income, and non-senior citizen adults. We conclude that a cost-share rebate approach is likely to significantly affect household adoption decisions, and the partial contributions paid by households can assist with lowering the substantial compliance costs for local governments to meet water quality requirements.

  16. Factorial study of rain garden design for nitrogen removal

    Science.gov (United States)

    Abstract Nitrate (〖NO〗_3^--N ) removal studies in bioretention systems showed great variability in removal rates and in some cases 〖NO〗_3^--N was exported. A 3-way factorial design (2 x 2 x 4) was devised for eight outdoor un-vegetated rain gardens to evaluate the effects of ...

  17. Whether or Not to Run in the Rain

    Science.gov (United States)

    Bocci, Franco

    2012-01-01

    The problem of choosing an optimal strategy for moving in the rain has attracted considerable attention among physicists and other scientists. Taking a novel approach, this paper shows, by studying simple shaped bodies, that the answer depends on the shape and orientation of the moving body and on wind direction and intensity. For different body…

  18. Rain Fade Compensation Alternatives for Ka Band Communication Satellites

    Science.gov (United States)

    Acosta, Roberto J.

    1997-01-01

    Future satellite communications systems operating in Ka-band frequency band are subject to degradation produced by the troposphere which is much more severe than those found at lower frequency bands. These impairments include signal absorption by rain, clouds and gases, and amplitude scintillation's arising from refractive index irregularities. For example, rain attenuation at 20 GHz is almost three times that at 11 GHz. Although some of these impairments can be overcome by oversizing the ground station antennas and high power amplifiers, the current trend is using small (less than 20 inches apertures), low-cost ground stations (less than $1000) that can be easily deployed at user premises. As a consequence, most Ka-band systems are expected to employ different forms of fade mitigation that can be implemented relatively easily and at modest cost. The rain fade mitigation approaches are defined by three types of Ka-band communications systems - a low service rate (less than 1.5 Mb/s), a moderate service rate (1.5 to 6 Mb/s) system and a high service rate (greater than 43 Mb/s) system. The ACTS VSAT network, which includes an adaptive rain fade technique, is an example of a moderate service rate.

  19. Rain Forests(高一适用)

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    More than 50,000,000 people of the world live in rain forests andmost of them do not hurt the forests theylive in. They eat the fruits that grow onthe trees, but they do not cut them down.They kill animals for food, but they do notdestroy them.

  20. Speciation of 129I in sea, lake and rain waters

    DEFF Research Database (Denmark)

    Lehto, Jukka; Räty, Tero; Hou, Xiaolin;

    2012-01-01

    Concentrations of the very long-lived fission product 129I and stable iodine (127I) in the Baltic Sea and lake and rain waters from Finland, were measured as well as their occurrence as iodide (I−) and iodate (IO3−). The highest concentrations of both 127I and 129I occurred in sea water, on avera...

  1. Mechanics of Interrill Erosion with Wind-Driven Rain (WDR)

    Science.gov (United States)

    This article provides an evaluation analysis for the performance of the interrill component of the Water Erosion Prediction Project (WEPP) model for Wind-Driven Rain (WDR) events. The interrill delivery rates (Di) were collected in the wind tunnel rainfall simulator facility of the International Cen...

  2. Observing the formation of flare-driven coronal rain

    CERN Document Server

    Scullion, E; Antolin, P; Wedemeyer, S; Vissers, G; Kontar, E P; Gallagher, P

    2016-01-01

    Flare-driven coronal rain can manifest from rapidly cooled plasma condensations near coronal loop-tops in thermally unstable post-flare arcades. We detect 5 phases that characterise the post-flare decay: heating, evaporation, conductive cooling dominance for ~120 s, radiative / enthalpy cooling dominance for ~4700 s and finally catastrophic cooling occurring within 35-124 s leading to rain strands with s periodicity of 55-70 s. We find an excellent agreement between the observations and model predictions of the dominant cooling timescales and the onset of catastrophic cooling. At the rain formation site we detect co-moving, multi-thermal rain clumps that undergo catastrophic cooling from ~1 MK to ~22000 K. During catastrophic cooling the plasma cools at a maximum rate of 22700 K s-1 in multiple loop-top sources. We calculated the density of the EUV plasma from the DEM of the multi-thermal source employing regularised inversion. Assuming a pressure balance, we estimate the density of the chromospheric componen...

  3. Rain Erosion Behavior of Silicon Dioxide Films Prepared on Sapphire

    Institute of Scientific and Technical Information of China (English)

    Liping FENG; Zhengtang LIU; Wenting LIU

    2005-01-01

    Silicon dioxide (SiO2) films were prepared on sapphire (α-Al2O3) by radio frequency magnetron reactive sputtering in order to in crease both transmission and rain erosion resistant performance of infrared domes of sapphire. Composition and structure of SiO2 films were analyzed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD),respectively. The transmittance of uncoated and coated sapphire was measured using a Fourier transform infrared(FTIR) spectrometer. Rain erosion tests of the uncoated and coated sapphire were performed at 211 m/s impact velocity with an exposure time ranging from 1 to 8 min on a whirling arm rig. Results show that the deposited films can greatly increase the transmission of sapphire in mid-wave IR. After rain erosion test, decreases in normalized transmission were less than 1% for designed SiO2 films and the SiO2 coating was strongly bonded to the sapphire substrate. In addition, sapphires coated with SiO2 films had a higher transmittance than uncoated ones after rain erosion.

  4. Küberrünnete klassifitseerimine / Rain Ottis

    Index Scriptorium Estoniae

    Ottis, Rain

    2008-01-01

    NATO Kooperatiivse Küberkaitse Kompetentsikeskuse teadur leitnant Rain Ottis analüüsib kübermaailmas aset leidvate rünnete klassifitseerimise viise. Lisa: Ründaja motivaatorid; Ründe kontekst; Ründaja eesmärk. Diagramm: Kasutajate tegevus Internetis ja Eesti elanikkond 2007. aastal; Interneti kasutajate hulk Eestis 2007. aastal

  5. Lightning-based propagation of convective rain fields

    Directory of Open Access Journals (Sweden)

    S. Dietrich

    2011-05-01

    Full Text Available This paper describes a new multi-sensor approach for continuously monitoring convective rain cells. It exploits lightning data from surface networks to propagate rain fields estimated from multi-frequency brightness temperature measurements taken by the AMSU/MHS microwave radiometers onboard NOAA/EUMETSAT low Earth orbiting operational satellites. Specifically, the method allows inferring the development (movement, morphology and intensity of convective rain cells from the spatial and temporal distribution of lightning strokes following any observation by a satellite-borne microwave radiometer. Obviously, this is particularly attractive for real-time operational purposes, due to the sporadic nature of the low Earth orbiting satellite measurements and the continuous availability of ground-based lightning measurements – as is the case in most of the Mediterranean region. A preliminary assessment of the lightning-based rainfall propagation algorithm has been successfully made by using two pairs of consecutive AMSU observations, in conjunction with lightning measurements from the ZEUS network, for two convective events. Specifically, we show that the evolving rain fields, which are estimated by applying the algorithm to the satellite-based rainfall estimates for the first AMSU overpass, show an overall agreement with the satellite-based rainfall estimates for the second AMSU overpass.

  6. Accelerated rain erosion of wind turbine blade coatings

    DEFF Research Database (Denmark)

    Zhang, Shizhong

    During operation, the fast-moving blades of wind turbines are exposed to continuous impacts with rain droplets, hail, insects, or solid particles. This can lead to erosion of the blades, whereby the electrical efficiency is compromised and expensive repairs may be required. One possible solution...

  7. Plant diversity after rain-forest fires in Borneo

    NARCIS (Netherlands)

    Eichhorn, Karl August Otto

    2006-01-01

    In the last two decades El-Niño-induced fires have caused widespread destruction of forests in East Kalimantan. The 1997-98 fires were the most extensive yet. The post-fire situation was studied in detail by field assessments and high-resolution SAR-images. My results show that rain forests are bett

  8. Rain Tolk : "Jan Uuspõld on asendamatu" / Greta Kaupmees

    Index Scriptorium Estoniae

    Kaupmees, Greta

    2006-01-01

    Kanal 2 saate "TOP 10" naljameeste pingereas platseerus näitleja Jan Uuspõld 4. kohale. Teda iseloomustades pole üks komöödiafilmi "Jan Uuspõld läheb Tartusse" autoreid Rain Tolk kiitusega kitsi

  9. The US Acid Rain Program: design, performance, and assessment

    DEFF Research Database (Denmark)

    Svendsen, Gert Tinggaard

    1998-01-01

    The US Acid Rain Program (ARP) from 1990 allows 1,000 major electric utilities all over the US to trade SO2 permits. Historical emission rights have been grandfathered and the target level is 50% SO2 reduction. Market performance has been successfull with much trade activity and unexpectedly low...

  10. Equatorial Cross-Cutting Ripples on Titan - Regularly Warped Subsiding Methane Plains, not Eolian Dunes.

    Science.gov (United States)

    Kochemasov, G. G.

    2008-09-01

    Widely circulating opinion that titanian methane lowlands in a broad equatorial region are covered with eolian formations needs to be carefully checked. Of coarse, all three solid bodies with atmospheres in the inner solar system have dunes. Why do not have them on Titan? Most probably they do exist but discovered by radar up to now cross-cutting rippling features cannot be taken for them. For this there are several reasons. How it can be that prevailing "dune" strike coincides with prevailing wind direction? Normally (with some African exceptions) one sees real terrestrial dunes stretching across winds. And this is understandable from a point of view eolian dunes formation. This formation gives particular cross profile to dunes. Asymmetric profile - one slope is long and gentle and another one short and abrupt. But titanian "dunes" are mostly uniform and symmetric. And this characteristic is preserved for many hundreds of kilometers of very straight features. Then, the finest solid particles precipitation from the thick atmosphere of Titan should be distributed on the satellite surface more uniformly and cover dark lowlands and light icy highlands of the wide equatorial belt more or less evenly. But "dunes" are strictly associated with dark lowlands and tend to turn round light icy obstacles. Cindering smoggy particles to produce sands for making dunes is a pure imagination. Then, radar preferably sees one direction but nevertheless one or more crossing directions of rippling are distinguished (Fig.3, 4) They mean two wind directions at the same time or another wind direction at another time? If so, the earlier "dunes" should be more or less obliterated by the later ones. Nothing of the kind! Both crossing ripples directions are fresh. Then, eolian action is not seen at the higher latitudes (Fig. 5). There are no winds there? Probably it is not so. Only a liquid state of methane can help (but liquid should be disturbed by winds). Solid methane there is also

  11. Female genital mutilation in African and African American women's literature

    Directory of Open Access Journals (Sweden)

    Darja Marinšek

    2007-12-01

    Full Text Available The article builds on the existing dispute between African and African American women writers on the competence of writing about female genital mutilation (FGM, and tries to determine the existence and nature of the differences between the writings of these two groups. The author uses comparative analysis of two popular African and African American novels, comparing their ways of describing FGM, its causes and consequences, the level ob objectivity and the style of the narrations.This is followed by a discussion on the reasons for such differences, incorporating a larger circle of both African and African American women authors, at the same time analysing the deviance within the two groups. While the differences between African American writers are not that great, as they mostly fail to present the issue from different points of view, which is often the result of their lack of direct knowledge of the topic, African authors' writing is in itself discovered to be ambivalent and not at all invariable. The reasons for such ambivalence are then discussed in greater context, focusing on the effect of the authors' personal contact with circumcision as well as their knowledge and acceptance of Western values. The author concludes by establishing the African ambivalent attitude towards FGM, which includes different aspects of the issue, as the most significant difference between their and African American writers' description of this practice.

  12. The Role of the Halted Baroclinic Mode at the Central Equatorial Pacific in El Ni(n)o Event

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The role of halted "baroclinic modes" in the central equatorial Pacific is analyzed. It is found that dominant anomaly signals corresponding to "baroclinic modes" occur in the upper layer of the equatorial Pacific, in a two-and-a-half layer oceanic model, in assimilated results of a simple OGCM and in the ADCP observation of TAO. A second "baroclinic mode" is halted in the central equatorial Pacific corresponding to a positive SST anomaly while the first "baroclinic mode" propagates eastwards in the eastern equatorial Pacific. The role of the halted second "baroclinic mode" in the central equatorial Pacific is explained by a staged ocean-atmosphere interaction mechanism in the formation of El Ni(n)o: the westerly bursts in boreal winter over the western equatorial Pacific generate the halted second "baroclinic mode" in the central equatorial Pacific, leading to the increase of heat content and temperature in the upper layer of the central Pacific which induces the shift of convection from over the western equatorial Pacific to the central equatorial Pacific; another wider, westerly anomaly burst is induced over the western region of convection above the central equatorial Pacific and the westerly anomaly burst generates the first "baroclinic mode"propagating to the eastern equatorial Pacific, resulting in a warm event in the eastern equatorial Pacific.The mechanism presented in this paper reveals that the central equatorial Pacific is a key region in detecting the possibility of ENSO and, by analyzing TAO observation data of ocean currents and temperature in the central equatorial Pacific, in predicting the coming of an El Ni(n)o several months ahead.

  13. Rain-induced subsurface airflow and Lisse effect

    Science.gov (United States)

    Guo, H.; Jiao, J.J.; Weeks, E.P.

    2008-01-01

    Water-level increase after rainfall is usually indicative of rainfall recharge to groundwater. This, however, may not be true if the Lisse effect occurs. This effect represents the water-level increase in a well driven by airflow induced by an advancing wetting front during highly intensive rains. The rainwater, which may behave like a low-permeability lid, seals the ground surface so that the air pressure beneath the wetting front is increased because of air compression due to downward movement of the wetting front. A rapid and substantial rise of the water level in the well screened below water table, which bears no relationship to groundwater recharge, can be induced when various factors such as soil properties and the rain-runoff condition combine favorably. A transient, three-dimensional and variably saturated flow model was employed to study the air and groundwater flows in the soil under rain conditions. The objectives of this paper are two-fold: to evaluate the reliability of the theory of the Lisse effect presented by Weeks to predict its magnitude in modeled situations that mimic the physical complexity of real aquifers, and to conduct parametric studies on the sensitivity of the water-level rise in the well to soil properties and the rain event. The simulation results reveal that the magnitude of the Lisse effect increases with the ponding depth. Soil permeability plays a key role in generating the Lisse effect. The water-level rise in the well is delayed relative to the air-pressure rise in the unsaturated zone when the soil permeability is low, and the maximum water-level rise is less than the maximum air pressure induced by rain infiltration. The simulation also explores the sensitivity of the Lisse effect to the van Genuchten parameters and the water table depth. Copyright 2008 by the American Geophysical Union.

  14. Attenuation of surface waves due to monsoon rains: A model study for the north Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Vethamony, P.; Kumar, B.P.; Sarma, Y.V.B.

    The dynamic interaction of intense rain with waves based on momentum exchange is applied to a second generation wave model to predict wave attenuation during monsoon. The scheme takes into account the characteristics of rain and wave parameters...

  15. Learning About Acid Rain: A Teacher's Guide for Grades 6 through 8

    Science.gov (United States)

    Find on this page a link to the Acid Rain Teacher's Guide for Students Grades 6-8. This guide contains information, class discussions and experiments teachers can use to teach students about acid rain.

  16. Equatorial plasma bubbles with enhanced ion and electron temperatures

    Science.gov (United States)

    Park, Jaeheung; Min, Kyoung Wook; Kim, Vitaly P.; Kil, Hyosub; Su, Shin-Yi; Chao, Chi Kuang; Lee, Jae-Jin

    2008-09-01

    While the ion and electron temperatures inside equatorial plasma bubbles (EPBs) are normally lower than those in an ambient plasma, bubbles with enhanced temperatures (BETs) are found occasionally in the topside ionosphere. Here we report the characteristics of BETs identified from observations of the first Republic of China Satellite (ROCSAT-1), the first Korea Multi-purpose Satellite (KOMPSAT-1), and the Defense Meteorological Satellite Program (DMSP) F15 during the solar maximum period between 2000 and 2001. The oxygen ion fraction inside the BETs, which was no lower than that of the ambient ionosphere, was similar to the case of ordinary low-temperature EPBs. These observations indicate that the BETs and low-temperature EPBs detected on the topside were produced by the upward drift of low-density plasma from lower altitudes. The feature that distinguishes BETs from normal EPBs is the occurrence of an unusually fast poleward field-aligned plasma flow relative to the ambient plasma. The BETs occurred preferentially around geomagnetic latitudes of 10° in the summer hemisphere, where the ambient ion and electron temperatures are lower than those in the conjugate winter hemisphere. The occurrence of BETs did not show any notable dependence on geomagnetic activities. The characteristics of the BETs suggest that the BETs were produced by adiabatic plasma heating associated with a fast poleward oxygen ion transport along magnetic flux tubes.

  17. Bifurcation of Pacific North Equatorial Current at the surface

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The grid altimetry data between 1993 and 2006 near the Philippines were analyzed by the method of Empirical Orthogonal Function (EOF) to study the variation of bifurcation of the North Equatorial Current at the surface of the Pacific. The relatively short-term signals with periods of about 6 months, 4 months, 3 months and 2 months are found besides seasonal and interannual variations mentioned in previous studies. Local wind stress curl plays an important role in controlling variation of bifurcation latitude except in the interannual timescale. The bifurcation latitude is about 13.3°N in annual mean state and it lies at the northernmost position (14.0°N) in January, at the southernmost position (12.5°N) in July. The amplitude of variation of bifurcation latitude in a year is 1.5°, which can mainly be explained as the contributions of the signals with periods of about 1 year (1.2°) and 0.5 year (0.3°).

  18. Equatorial wave activity during 2007 over Gadanki, a tropical station

    Indian Academy of Sciences (India)

    Salauddin Mohammad; Gopa Dutta; B Venkateswara Rao; P Vinay Kumar

    2015-06-01

    ECMWF Re-Analysis (ERA-interim) data of winds for the year 2007 between the pressure levels 1 and 1000 hPa (0–49 km) have been analyzed for equatorial wave activity over a tropical station Gadanki (13.5°N, 79.2°E). Available wind observations made by MST radar located at the same site have also been used to investigate the wave activity in the troposphere and lower stratosphere. Waves in the period bands 7–10, 12–15 and 20–30 d are observed. Temporal variability of the wave activity has been investigated by constructing wavelet spectra. The longer period waves show strong seasonal variability with maximum and minimum activities during winter and summer months respectively. Short period activity is more prominent during June–July–August in the tropospheric region. The waves are found to be generated in the troposphere by wind shear and convection. Propagation of the waves to higher altitudes is found to depend strongly on background zonal wind and phase of the quasi-biennial oscillation (QBO). The waves are inhibited to propagate through the negative wind shear zone. Meridional waves might be generated by non-linear wave CISK.

  19. Stormtime dynamics of the global thermosphere and equatorial ionosphere

    Directory of Open Access Journals (Sweden)

    W. J. Burke

    2009-05-01

    Full Text Available During magnetic storms the development of equatorial plasma bubbles (EPBs and distributions of thermospheric densities are strongly influenced by the histories of imposed magnetospheric electric (εM fields. Periods of intense EPB activity driven by penetration εM fields in the main phase are followed by their worldwide absence during recovery. A new method is applied to estimate global thermospheric energy (Eth budgets from orbit-averaged densities measured by accelerometers on polar-orbiting satellites. During the main phase of storms Eth increases as long as the stormtime εM operates, then exponentially decays toward quiet-time values during early recovery. Some fraction of the energy deposited at high magnetic latitudes during the main phase propagates into the subauroral ionosphere-thermosphere where it affects chemical and azimuthal-wind dynamics well into recovery. We suggest a scenario wherein fossils of main phase activity inhibit full restoration of quiet-time dayside dynamos and pre-reversal enhancements of upward plasma drifts near dusk denying bottomside irregularities sufficient time to grow into EPBs.

  20. The field of the equatorial electrojet from CHAMP data

    Directory of Open Access Journals (Sweden)

    J.-L. Le Mouël

    2006-03-01

    Full Text Available We apply a simple linear transform, the along-track second derivative, to four years of scalar and vectorial data from the CHAMP satellite. This transform, reminiscent of techniques used in the interpretation of aeromagnetic surveys, is applied either to the geocentric spherical components of the field or to its intensity. After averaging in time and space, we first produce a map of the crustal field, then maps of the equatorial electrojet field at all local times and all universal times. The seasonal variation of the electrojet, its evolution with the solar cycle, and the effect of geomagnetic activity are discussed. The variation of the electrojet with longitude, an intriguing feature revealed by satellite data, is described in some detail, and it is shown that this longitude dependance is stable in time. The existence of a counterelectrojet in the morning, everywhere except over the Pacific Ocean, is established. The signatures of closure electric currents and of interhemispheric currents are also evidenced.

  1. Sensor-controlled heliostat with an equatorial mount

    Energy Technology Data Exchange (ETDEWEB)

    Aiuchi, Kosuke; Yoshida, Kazuo; Onozaki, Masaki; Katayama, Yukuo [The Institute of Applied Energy, Tokyo (Japan); Nakamura, Minoru; Nakamura, Katsushige [Mitaka Kohki Co. Ltd., Tokyo (Japan)

    2006-09-15

    A heliostat having a photo-sensor sun-tracking system was developed and evaluated. The sensor was composed of a set of two photo-cells placed side by side on the bottom of the small box. Sun-tracking can be achieved by rotating the heliostat equipped with the sensor, while maintaining the two photo-cells under illumination by the sun through a slit in the box. A preliminary tracking evaluation of the sensor was carried out with the aid of a mirror-telescope system, and the tracking error was estimated to be less than 0.6mrad in clear weather. The developed heliostat employed an equatorial mount system that permits the rotating speed of the right-ascension axis to be nearly constant for the diurnal motion of the sun. The use of two additional sensors, a cloud sensor and a primary sensor, permitted stable tracking with high accuracy even in a cloudy sky. Field tests of the heliostat revealed that an angular error within 2mrad was achieved in fine weather. In cloudy weather, the heliostat operated stably with the cloud sensor within an error of 10mrad. (author)

  2. Equatorial segment of the mid-atlantic ridge

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-12-31

    The Equatorial Segment of the Mid-Atlantic Ridge is a part of this mid-oceanic ridge limited by a cluster of fracture zones - Cape Verde, Marathon, Mercury, Vema, Doldrums, Vernadsky and Sierra Leone - in the North, and a similar cluster of fracture zones - St Paul, Romanche and Chain - in the South. During recent decades, following the publication of the 5. edition of the General Bathymetric Chart of the Oceans (GEBCO), there has been a great deal of geological-geophysical research and mapping of the World Ocean. The results have led to the development of a number of theories concerning the essential heterogeneity of the structure of the ocean floor and, in particular, the heterogeneity of the structure and segmentation of mid-oceanic ridges. Research on the nature of such segmentation is of great importance for an understanding of the processes of development of such ridges and oceanic basins as a whole. Chapter 20 is dedicated to the study of the atlantic ocean mantle by using (Th.U)Th, (Th/U)pb and K/Ti systematics 380 refs.

  3. Periodicity in the occurrence of equatorial plasma bubbles

    Science.gov (United States)

    Choi, J.; Kim, Y.; Kil, H.; Kwak, Y.; Lee, W.

    2013-12-01

    The observations of equatorial plasma bubbles by low-inclination orbit satellites show periodic occurrence of bubbles along satellite orbits. The periodicity in the bubble occurrence provides a useful tool for identifying the role of gravity waves in the creation of bubbles. In this study, we investigate the variability of the periodicity in the bubble occurrence by analyzing the observations of Communication/Navigation Outage Forecasting System (C/NOFS) and the first Republic of China satellite (ROCSAT-1). Here the periodicity indicates spatial periodicity and is derived by applying a Fourier analysis to the electron densities projected onto the magnetic apex height. Our preliminary results show an occurrence of significant amplitudes of periodicity peaks on the spatial scale range of 50-1000 km. The periodicity on small scales may be associated with the bifurcation of bubbles or to the creation of multiple bubbles for one wave seeding. The periodicity on larger scales is considered to be related with the scale size of a seeding mechanism. We present statistics of the periodicity and the coincident satellite observations of periodic bubbles with ground observations.

  4. Climate regulation of fire emissions and deforestation in equatorial Asia.

    Science.gov (United States)

    van der Werf, G R; Dempewolf, J; Trigg, S N; Randerson, J T; Kasibhatla, P S; Giglio, L; Murdiyarso, D; Peters, W; Morton, D C; Collatz, G J; Dolman, A J; DeFries, R S

    2008-12-23

    Drainage of peatlands and deforestation have led to large-scale fires in equatorial Asia, affecting regional air quality and global concentrations of greenhouse gases. Here we used several sources of satellite data with biogeochemical and atmospheric modeling to better understand and constrain fire emissions from Indonesia, Malaysia, and Papua New Guinea during 2000-2006. We found that average fire emissions from this region [128 +/- 51 (1sigma) Tg carbon (C) year(-1), T = 10(12)] were comparable to fossil fuel emissions. In Borneo, carbon emissions from fires were highly variable, fluxes during the moderate 2006 El Niño more than 30 times greater than those during the 2000 La Niña (and with a 2000-2006 mean of 74 +/- 33 Tg C yr(-1)). Higher rates of forest loss and larger areas of peatland becoming vulnerable to fire in drought years caused a strong nonlinear relation between drought and fire emissions in southern Borneo. Fire emissions from Sumatra showed a positive linear trend, increasing at a rate of 8 Tg C year(-2) (approximately doubling during 2000-2006). These results highlight the importance of including deforestation in future climate agreements. They also imply that land manager responses to expected shifts in tropical precipitation may critically determine the strength of climate-carbon cycle feedbacks during the 21st century.

  5. Equatorial ionospheric disturbance observed through a transequatorial HF propagation experiment

    Directory of Open Access Journals (Sweden)

    T. Maruyama

    2006-07-01

    Full Text Available A transequatorial radio-wave propagation experiment at shortwave frequencies (HF-TEP was done between Shepparton, Australia, and Oarai, Japan, using the radio broadcasting signals of Radio Australia. The receiving facility at Oarai was capable of direction finding based on the MUSIC (Multiple Signal Classification algorithm. The results were plotted in azimuth-time diagrams (AT plots. During the daytime, the propagation path was close to the great circle connecting Shepparton and Oarai, thus forming a single line in the AT plots. After sunset, off-great-circle paths, or satellite traces in the AT plot, often appeared abruptly to the west and gradually returned to the great circle direction. However, there were very few signals across the great circle to the east. The off-great-circle propagation was very similar to that previously reported and was attributed to reflection by an ionospheric structure near the equator. From the rate of change in the direction, we estimated the drift velocity of the structure to range mostly from 100 to 300 m/s eastward. Multiple instances of off-great-circle propagation with a quasi-periodicity were often observed and their spatial distance in the east-west direction was within the range of large-scale traveling ionospheric disturbances (LS-TIDs. Off-great-circle propagation events were frequently observed in the equinox seasons. Because there were many morphological similarities, the events were attributed to the onset of equatorial plasma bubbles.

  6. Electric field diagnostics of the dynamics of equatorial density depletions

    Science.gov (United States)

    Laakso, H.; Maynard, N. C.; Pfaff, R. F.; Aggson, T. L.; Coley, W. R.; Janhunen, P.; Herrero, F. A.

    1997-09-01

    During its life of 10 months, the San Marco D satellite crossed a large number of plasma density depletion channels in the nightside F-region equatorial ionosphere. In-situ measurements of vector electric fields from San Marco D reveal convection velocity variations inside such channels and thus can be used as diagnostics of the dynamics of these plasma depleted regions. Furthermore, in some cases, the temporal evolution of the channel can be inferred from the measurements. In this paper the electric field data are converted to plasma drift velocities in order to illustrate cases where the plasma flow is directed upward or downward in the channel, the channel itself is oriented vertically upward or tilted eastward/westward, or the channel is experiencing a bifurcation or pinching-off process. Although the E × B plasma drift velocities within the depleted channels are commonly a few hundred m s-1, on some occasions electric fields corresponding to speeds as large as 2-3 km s-1 have been observed. The implications for such highly supersonic convection are discussed, including the possible constriction of such high-speed depletion channels at higher altitudes.

  7. Provisional hourly values of equatorial Dst for January to June 1972

    Science.gov (United States)

    Sugiura, M.; Poros, D. J.

    1972-01-01

    Provisional hourly values of equatorial atmospheric radiation conditions for the period January to June 1972 were obtained. The data are presented in numerical tables with graphical presentation of the digital data included.

  8. Observational evidence of lower-frequency Yanai waves in the central equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    David, D.T.; PrasannaKumar, S.; Byju, P.; Sarma, M.S.S.; Suryanarayana, A.; Murty, V.S.N.

    created by the northward shifting and strengthening of the westward flowing south equatorial current associated with positive IOD and the eastward flowing southwest monsoon current provides energy for the generation of lower-frequency Yanai waves. Vertical...

  9. Weight Percentage of Calcium Carbonate for 17 Equatorial Pacific Cores from Brown University

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Weight percentages of calcium carbonate in this file were compiled by J. Farrell and W. L. Prell of Brown University for 17 equatorial Pacific Ocean sediment cores....

  10. A Summary of Scatterometer Returns from Water Surfaces Agitated by Rain

    Science.gov (United States)

    Bliven, Larry F.; Giovanangeli, Jean-Paul; Branger, Hubert; Sobieski, Piotr W.

    1997-01-01

    In this paper, we summarize our initial findings from K(a)- and K(u)-band scatterometers which include: a scaling law for backscattered power as a function of rain rate; a linear superposition model for light rains and low wind speeds; evidence of the importance of scattering from rain-generated ring-waves; and progress towards development of a scattering model for computing normalized radar cross sections from wind and rain roughened water surfaces.

  11. Spatio–temporal rain attenuation model for application to fade mitigation techniques

    OpenAIRE

    2004-01-01

    We present a new stochastic-dynamic model useful for the planning and design of gigahertz satellite communications using fade mitigation techniques. It is a generalization of the Maseng–Bakken and targets dual-site dual-frequency rain attenu- ated satellite links. The outcome is a consistent and comprehensive model capable of yielding theoretical descriptions of: 1) long-term power spectral density of rain attenuation; 2) rain fade slope; 3) rain frequency scaling factor; 4) site diversity; a...

  12. Data driven clustering of rain events: microphysics information derived from macro scale observations

    OpenAIRE

    Dilmi, Mohamed Djallel; Mallet, Cécile; Barthes, Laurent; Chazottes, Aymeric

    2016-01-01

    The study of rain time series records is mainly carried out using rainfall rate or rain accumulation parameters estimated on a fixed duration (typically 1 min, 1 hour or 1 day). In this paper we used the concept of rain event. Among the numerous existing variables dedicated to the characterisation of rain events, the first part of this paper aims to obtain a parsimonious characterisation of these events using a minimal set of variables. In this context an algorithm based on Genetic Algorithm ...

  13. ANALYSIS OF DEBRIS FLOW DISASTER DUE TO HEAVY RAIN BY X-BAND MP RADAR DATA

    OpenAIRE

    Nishio, M; Mori, M

    2016-01-01

    On August 20 of 2014, Hiroshima City (Japan) was struck by local heavy rain from an autumnal rain front. The resultant debris flow disaster claimed 75 victims and destroyed many buildings. From 1:30 am to 4:30 am on August 20, the accumulated rainfall in Hiroshima City exceeded 200 mm. Serious damage occurred in the Asakita and Asaminami wards of Hiroshima City. As a disaster prevention measure, local heavy rain (localized torrential rains) is usually observed by the Automated Meteor...

  14. CR@BaSO4: an acid rain-indicating material.

    Science.gov (United States)

    Gao, Hong-Wen; Xu, Xin-Hui

    2011-12-28

    The CR@BaSO(4) hybrid was synthesized, characterized and used as an acid rain-indicating (ARI) material. A painted ARI umbrella was discolored after exposure to simulated acid rain of pH 5 or less and returned to the initial color after the rain stopped. Such a functionalized material may make acid rain visual to remind people in real-time.

  15. A simple model for the estimation of rain-induced attenuation along earth-space paths at millimeter wavelengths

    Science.gov (United States)

    Stutzman, W. L.; Dishman, W. K.

    1982-12-01

    A simple attenuation model (SAM) is presented for estimating rain-induced attenuation along an earth-space path. The rain model uses an effective spatial rain distribution which is uniform for low rain rates and which has an exponentially shaped horizontal rain profile for high rain rates. When compared to other models, the SAM performed well in the important region of low percentages of time, and had the lowest percent standard deviation of all percent time values tested.

  16. Equatorial Scintillation Predictions from C/NOFS Planar Langmuir Probe Electron Density Fluctuation Data

    Science.gov (United States)

    2014-09-05

    Brasil Tel: 55 21 3527 1682; Fax: 55 21 3527 1154 E-mail: epoc @cetuc.puc-rio.br FINAL PERFORMANCE REPORT Equatorial scintillation...21 35271682 epoc @cetuc.puc-rio.br Affiliation: Centro de Estudos em Telecomunicações (CETUC) Pontifícia Universidade Católica do Rio de...1682; Fax: 55 21 3527 1154 E-mail: epoc @cetuc.puc-rio.br FINAL PERFORMANCE REPORT Equatorial scintillation predictions from C/NOFS Planar

  17. The Bifurcation of the Equatorial Periodic Orbit of the Planar Polynomial Vector Fields

    Institute of Scientific and Technical Information of China (English)

    Xin An ZHANG; Lan Sun CHEN; Zhao Jun LIANG

    2001-01-01

    In this paper, we have obtained the necessary and sufficient condition for the set of pointsat infinity on the plane R2 to be a periodic orbit which is called an equatorial periodic orbit of a planarvector field X(x), and the formulae about the multiplicity of the equatorial periodic orbit of X(x). Wehave also proved that the main result of [9] is erroneous with regard to the formulae.

  18. Yu Zhengsheng Attends Reception Marking 45th Anniversary Of China-Equatorial Guinea Diplomatic Relations

    Institute of Scientific and Technical Information of China (English)

    Xu; Liya

    2015-01-01

    On April 29,the CPAFFC held a reception in Beijing to celebrate the 45th anniversary of the establishment of diplomatic relations between China and Equatorial Guinea.Yu Zhengsheng,Chairman of the National Committee of the Chinese People’s Political Consultative Conference(CPPCC)and Teodoro Obiang Nguema Mbasogo,President of Equatorial Guinea,spoke on the occasion.Among the audience of some 150were Abdul’ahat Abdulrixit,former

  19. The effect of J{sub 2} on equatorial and halo orbits around a magnetic planet

    Energy Technology Data Exchange (ETDEWEB)

    Inarrea, Manuel [Universidad de la Rioja, Area de Fisica, 26006 Logrono (Spain); Lanchares, Victor [Dpto. de Matematicas y Computacion, CIEMUR: Centro de Investigacion en Informatica, Estadistica y Matematicas, Universidad de la Rioja, 26004 Logrono (Spain)], E-mail: vlancha@unirioja.es; Palacian, Jesus F. [Universidad Publica de Navarra, Departamento de Ingenieria Matematica e Informatica, 31006 Pamplona (Spain); Pascual, Ana I. [Dpto. de Matematicas y Computacion, CIEMUR: Centro de Investigacion en Informatica, Estadistica y Matematicas, Universidad de la Rioja, 26004 Logrono (Spain); Pablo Salas, J. [Universidad de la Rioja, Area de Fisica, 26006 Logrono (Spain); Yanguas, Patricia [Universidad Publica de Navarra, Departamento de Ingenieria Matematica e Informatica, 31006 Pamplona (Spain)

    2009-10-15

    We calculate equatorial and halo orbits around a non-spherical (both oblate and prolate) magnetic planet. It is known that circular equatorial and halo orbits exist for a dust grain orbiting a spherical magnetic planet. However, the frequency of the orbit is constrained by the charge-mass ratio of the particle. If the non-sphericity of the planet is taken into account this constraint is modified or, in some cases, it disappears.

  20. Preliminary Thermal Mechanical Analysis of the Equatorial Thermal Shield for ITER

    Institute of Scientific and Technical Information of China (English)

    雷明准; 宋云涛; 杜世俊; 叶民友; 奚维斌; 刘旭峰

    2012-01-01

    Thermal analysis of the equatorial thermal shield for ITER is conducted in order to confirm that the cooling tube design was reasonable under both the plasma operational and the baking operational conditions. The structural performance was analyzed by means of the finite element software ANSYS. A comparison of the results with design requirements shows that the results of the simulation are within allowable design requirements, which indicates the feasibility and reliability of the equatorial thermal shield structure.

  1. Introduction of prognostic rain in ECHAM5: design and Single Column Model simulations

    Directory of Open Access Journals (Sweden)

    R. Posselt

    2007-10-01

    Full Text Available Prognostic equations for the rain mass mixing ratio and the rain drop number concentration are introduced into the large-scale cloud microphysics parameterization of the ECHAM5 general circulation model (ECHAM5-RAIN. For this a rain flux from one level to the next with the appropriate fall speed is introduced. This maintains rain water in the atmosphere to be available for the next time step. Rain formation in ECHAM5-RAIN is, therefore, less dependent on the autoconversion rate than the standard ECHAM5 but shifts the emphasis towards the accretion rates in accordance with observations. ECHAM5-RAIN is tested and evaluated with two cases: the continental mid-latitude ARM Cloud IOP (shallow frontal cloud case – March 2000 and EPIC (a marine stratocumulus study – October 2001. The prognostic equations for rain hardly affect the amount and timing of precipitation at the surface in different Single Column Model (SCM simulations for heavy precipitating clouds because heavy rain depends mainly on the large-scale forcing. In case of thin, drizzling clouds (i.e., stratocumulus, an increase in surface precipitation is caused by more sub-time steps used in the prognostic rain scheme until convergence is reached. Cloud microphysical quantities, such as liquid and rain water, are more sensitive to the number of sub-time steps for light precipitation. This results from the decreasing autoconversion rate and increasing accretion rate.

  2. 40 CFR 72.71 - Acceptance of State Acid Rain programs-general.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 16 2010-07-01 2010-07-01 false Acceptance of State Acid Rain programs... PROGRAMS (CONTINUED) PERMITS REGULATION Acid Rain Phase II Implementation § 72.71 Acceptance of State Acid... State Acid Rain program meeting the requirements of §§ 72.72 and 72.73. (b) The Administrator...

  3. 40 CFR 72.69 - Issuance and effective date of acid rain permits.

    Science.gov (United States)

    2010-07-01

    ...) AIR PROGRAMS (CONTINUED) PERMITS REGULATION Federal Acid Rain Permit Issuance Procedures § 72.69 Issuance and effective date of acid rain permits. (a) After the close of the public comment period, the Administrator will issue or deny an Acid Rain permit. The Administrator will serve a copy of any Acid...

  4. Equatorial segment protein (ESP) is a human alloantigen involved in sperm-egg binding and fusion.

    Science.gov (United States)

    Wolkowicz, M J; Digilio, L; Klotz, K; Shetty, J; Flickinger, C J; Herr, J C

    2008-01-01

    The equatorial segment of the sperm head is known to play a role in fertilization; however, the specific sperm molecules contributing to the integrity of the equatorial segment and in binding and fusion at the oolemma remain incomplete. Moreover, identification of molecular mediators of fertilization that are also immunogenic in humans is predicted to advance both the diagnosis and treatment of immune infertility. We previously reported the cloning of Equatorial Segment Protein (ESP), a protein localized to the equatorial segment of ejaculated human sperm. ESP is a biomarker for a subcompartment of the acrosomal matrix that can be traced through all stages of acrosome biogenesis (Wolkowicz et al, 2003). In the present study, ESP immunoreacted on Western blots with 4 (27%) of 15 antisperm antibody (ASA)-positive serum samples from infertile male patients and 2 (40%) of 5 ASA-positive female sera. Immunofluorescent studies revealed ESP in the equatorial segment of 89% of acrosome-reacted sperm. ESP persisted as a defined equatorial segment band on 100% of sperm tightly bound to the oolemma of hamster eggs. Antisera to recombinant human ESP inhibited both oolemmal binding and fusion of human sperm in the hamster egg penetration assay. The results indicate that ESP is a human alloantigen involved in sperm-egg binding and fusion. Defined recombinant sperm immunogens, such as ESP, may offer opportunities for differential diagnosis of immune infertility.

  5. A synthesis of the first GARP Globa Experiment (FGGE) in the equatorial Atlantic Ocean

    Science.gov (United States)

    Molinari, R. L.; Garzoli, S. L.; Katz, E. J.; Harrison, D. E.; Richardson, P. L.; Reverdin, G.

    A synthesis of near-surface oceanographic and surface meteorological data collected during the First GARP Global Experiment, FGGE, is presented to portray the oceanic response to the seasonal wind forcing for the period December 1978 to November 1979, inclusive. Major wind events during FGGE are in phase with events given in climatology. In particular, the February-March-April relaxation and May enhancement of equatorial winds occurs within one month of the mean event. Accordingly, the oceanic responses, such as the May, June, July appearance of an equatorial cold water tongue, the acceleration of the South Equatorial Current (SEC) and the vertical displacement of the equatorial thermocline occur at the average time. Furthermore, the curl distribution in the vicinity of the North Equatorial Countercurrent (NECC) during 1979 is similar to the climatological distribution in terms of phase and amplitude, except for a westward displacement in the position of the maximum curl. As predicted from linear theory, the 1979 thermocline response across the NECC is in phase with the climatological response with a westward displacement of the maximum thermocline movement. Deeper than average equatorial thermoclines and a weaker SEC may, in part, be responsible for the anomalously warm sea-surface temperatures observed on the equator between 10°W and 30°W from June to November.

  6. Seasonal Variation of Diurnal Cycle of Rainfall in the Eastern Equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar, M.R.; Pednekar, S.; Katsumata, M.; Antony, M.K.; Kuroda, Y.; Unnikrishnan, A.S.

    it was seen that majority of the rain events (> 60%) were less than 3 hours duration throughout the study period. The longer duration rainfall events (i.e rain events greater than 6 hour duration) contributed significantly to Spring 2002 (20% of the total...

  7. The African Union

    DEFF Research Database (Denmark)

    Mandrup, Thomas; Mandrup, Bjørn

    2009-01-01

    . Moreover, the ‘African Security Architecture’, of which it is the central component, also includes sub-regional organisations to which responsibility is to be devolved for dealing with armed confl ict and other matters. These so-called Regional Economic Communities (RECs) are, likewise, constantly changing......The African Union (AU) is a young international organisation, founded in 2002, which is still in the process of setting up its various institutions, while constantly having to face up to new challenges, such as civil wars breaking out and military coups being undertaken in its member states......, just as they have very different strengths. Hence, any account of the AU and the RECs can only provide a ‘snapshot’ of the organisation at any given time, one which may soon become outdated. In contrast with regional and sub-regional organisations in the North, those in Africa are facing an additional...

  8. Steps to African Development

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The development of Africa is vital to the world’s sustainable development.However,African countries still face key challenges in achieving the meaningful expansion of their economies.At the High-Level Symposium on China-Africa Investment Cooperation in Xiamen,southeast China’s Fujian Province,held from September 8 to 10,Chen Deming,Minister of Commerce of China,elaborates on these challenges and sees

  9. A study of transient variations in the Earth's electromagnetic field at equatorial electrojet latitudes in western Africa (Mali and the Ivory Coast

    Directory of Open Access Journals (Sweden)

    J. Vassal

    Full Text Available In the framework of the French-Ivorian participation to the IEEY, a network of 10 electromagnetic stations were installed at African longitudes. The aim of this experiment was twofold: firstly, to study the magnetic signature of the equatorial electrojet on the one hand, and secondly, to characterize the induced electric field variations on the other hand. The first results of the magnetic field investigations were presented by Doumouya and coworkers. Those of the electric field experiment will be discussed in this study. The electromagnetic experiment will be described. The analysis of the electromagnetic transient variations was conducted in accordance with the classical distinction between quiet and disturbed magnetic situations. A morphological analysis of the recordings is given, taking into consideration successively quiet and disturbed magnetic situations, with the results interpreted in terms of the characterization of external and internal sources. Particular attention was paid to the effects of the source characteristics on the induced field of internal origin, and to the bias they may consequently cause to the results of electromagnetic probing of the Earth; the source effect in electromagnetic induction studies. During quiet magnetic situations, our results demonstrated the existence of two different sources. One of these, the SRE source, was responsible for most of the magnetic diurnal variation and corresponded to the well-known magnetic signature of the equatorial electrojet. The other source (the SR*E source was responsible for most of the electric diurnal variation, and was also likely to be an ionospheric source. Electric and magnetic diurnal variations are therefore related to different ionospheric sources, and interpreting the electric diurnal variation as induced by the magnetic field diurnal variation is not relevant. Furthermore, the magnetotelluric probing of the upper mantle at

  10. Human African trypanosomiasis.

    Science.gov (United States)

    Lejon, Veerle; Bentivoglio, Marina; Franco, José Ramon

    2013-01-01

    Human African trypanosomiasis or sleeping sickness is a neglected tropical disease that affects populations in sub-Saharan Africa. The disease is caused by infection with the gambiense and rhodesiense subspecies of the extracellular parasite Trypanosoma brucei, and is transmitted to humans by bites of infected tsetse flies. The disease evolves in two stages, the hemolymphatic and meningoencephalitic stages, the latter being defined by central nervous system infection after trypanosomal traversal of the blood-brain barrier. African trypanosomiasis, which leads to severe neuroinflammation, is fatal without treatment, but the available drugs are toxic and complicated to administer. The choice of medication is determined by the infecting parasite subspecies and disease stage. Clinical features include a constellation of nonspecific symptoms and signs with evolving neurological and psychiatric alterations and characteristic sleep-wake disturbances. Because of the clinical profile variability and insidiously progressive central nervous system involvement, disease staging is currently based on cerebrospinal fluid examination, which is usually performed after the finding of trypanosomes in blood or other body fluids. No vaccine being available, control of human African trypanosomiasis relies on diagnosis and treatment of infected patients, assisted by vector control. Better diagnostic tools and safer, easy to use drugs are needed to facilitate elimination of the disease.

  11. Ocean Color and the Equatorial Annual Cycle in the Pacific

    Science.gov (United States)

    Hammann, A. C.; Gnanadesikan, A.

    2012-12-01

    The presence of chlorophyll, colored dissolved organic matter (CDOM) and other scatterers in ocean surface waters affect the flux divergence of solar radiation and thus the vertical distribution of radiant heating of the ocean. While this may directly alter the local mixed-layer depth and temperature (Martin 1985; Strutton & Chavez 2004), non-local changes are propagated through advection (Manizza et al. 2005; Murtugudde et al. 2002; Nakamoto et al. 2001; Sweeny et al. 2005). In and coupled feedbacks (Lengaigne et al. 2007; Marzeion & Timmermann 2005). Anderson et al. (2007), Anderson et al. (2009) and Gnanadesikan & Anderson (2009) have performed a series of experiments with a fully coupled climate model which parameterizes the e-folding depth of solar irradiance in terms of surface chlorophyll-a concentration. The results have so far been discussed with respect to the climatic mean state and ENSO variability in the tropical Pacific. We extend the discussion here to the Pacific equatorial annual cycle. The focus of the coupled experiments has been the sensitivity of the coupled system to regional differences in chlorophyll concentration. While runs have been completed with realistic SeaWiFS-derived monthly composite chlorophyll ('green') and with a globally chlorophyll-free ocean ('blue'), the concentrations in two additional runs have been selectively set to zero in specific regions: the oligotrophic subtropical gyres ('gyre') in one case and the mesotrophic gyre margins ('margin') in the other. The annual cycle of ocean temperatures exhibits distinctly reduced amplitudes in the 'blue' and 'margin' experiments, and a slight reduction in 'gyre' (while ENSO variability almost vanishes in 'blue' and 'gyre', but amplifies in 'margin' - thus the frequently quoted inverse correlation between ENSO and annual amplitudes holds only for the 'green' / 'margin' comparison). It is well-known that on annual time scales, the anomalous divergence of surface currents and vertical

  12. Land - Ocean Climate Linkages and the Human Evolution - New ICDP and IODP Drilling Initiatives in the East African Rift Valley and SW Indian Ocean

    Science.gov (United States)

    Zahn, R.; Feibel, C.; Co-Pis, Icdp/Iodp

    2009-04-01

    , and Interocean Exchanges"; IODP ref. no. 702-full) aims at deciphering the late Neogene ocean history of the SW Indian Ocean. SAFARI specifically targets the Agulhas Current in the SW Indian Ocean that constitutes the strongest western boundary current in the southern hemisphere oceans. The Current transports warm and saline surface waters from the tropical Indian Ocean to the southern tip of Africa. Exchanges with the atmosphere influence eastern and southern African climates including individual weather systems such as extra-tropical cyclone formation in the region and rainfall patterns. Ocean models further suggest the "leakage" of Agulhas water around South Africa into the Atlantic potentially modulates the Atlantic meridional overturning circulation (MOC) with consequences for climate globally. The SAFARI drilling initiative aims to retrieve a suite of long drill cores along the southeast African margin and in the Indian-Atlantic ocean gateway. SAFARI will shed light on the history of Agulhas Current warm water transports along the southeast African margin during the late Neogene and its linking with ocean-climate developments. Specific objectives of SAFARI are to test (1) the sensitivity of the Agulhas Current to changing climates of the Plio/Pleistocene, including upstream forcing linked with equatorial Indian Ocean changes and Indonesian Throughflow; (2) the Current's influence on eastern and southern Africa climates, including rain fall patterns and vegetation changes; (3) buoyancy transfer to the Atlantic by Agulhas leakage around southern Africa, and (4) the contribution of variable Agulhas Leakage to shifts of the Atlantic MOC during episodes of major ocean and climate reorganizations of the past 5 Ma. These studies will provide insight into the Current's influence on eastern and southern African terrestrial climates, including its possible impact on the late Neogene evolution of large mammals including hominids. The ICDP and IODP drilling campaigns will

  13. Coral settlement on a highly disturbed equatorial reef system.

    Science.gov (United States)

    Bauman, Andrew G; Guest, James R; Dunshea, Glenn; Low, Jeffery; Todd, Peter A; Steinberg, Peter D

    2015-01-01

    Processes occurring early in the life stages of corals can greatly influence the demography of coral populations, and successful settlement of coral larvae that leads to recruitment is a critical life history stage for coral reef ecosystems. Although corals in Singapore persist in one the world's most anthropogenically impacted reef systems, our understanding of the role of coral settlement in the persistence of coral communities in Singapore remains limited. Spatial and temporal patterns of coral settlement were examined at 7 sites in the southern islands of Singapore, using settlement tiles deployed and collected every 3 months from 2011 to 2013. Settlement occurred year round, but varied significantly across time and space. Annual coral settlement was low (~54.72 spat m(-2) yr(-1)) relative to other equatorial regions, but there was evidence of temporal variation in settlement rates. Peak settlement occurred between March-May and September-November, coinciding with annual coral spawning periods (March-April and October), while the lowest settlement occurred from December-February during the northeast monsoon. A period of high settlement was also observed between June and August in the first year (2011/12), possibly due to some species spawning outside predicted spawning periods, larvae settling from other locations or extended larval settlement competency periods. Settlement rates varied significantly among sites, but spatial variation was relatively consistent between years, suggesting the strong effects of local coral assemblages or environmental conditions. Pocilloporidae were the most abundant coral spat (83.6%), while Poritidae comprised only 6% of the spat, and Acroporidae coral spat. These results indicate that current settlement patterns are reinforcing the local adult assemblage structure ('others'; i.e. sediment-tolerant coral taxa) in Singapore, but that the replenishment capacity of Singapore's reefs appears relatively constrained, which could lead

  14. Genetic population structure of Anopheles gambiae in Equatorial Guinea

    Directory of Open Access Journals (Sweden)

    Caccone Adalgisa

    2007-10-01

    Full Text Available Abstract Background Patterns of genetic structure among mosquito vector populations in islands have received particular attention as these are considered potentially suitable sites for experimental trials on transgenic-based malaria control strategies. In this study, levels of genetic differentiation have been estimated between populations of Anopheles gambiae s.s. from the islands of Bioko and Annobón, and from continental Equatorial Guinea (EG and Gabon. Methods Genotyping of 11 microsatellite loci located in chromosome 3 was performed in three island samples (two in Bioko and one in Annobón and three mainland samples (two in EG and one in Gabon. Four samples belonged to the M molecular form and two to the S-form. Microsatellite data was used to estimate genetic diversity parameters, perform demographic equilibrium tests and analyse population differentiation. Results High levels of genetic differentiation were found between the more geographically remote island of Annobón and the continent, contrasting with the shallow differentiation between Bioko island, closest to mainland, and continental localities. In Bioko, differentiation between M and S forms was higher than that observed between island and mainland samples of the same molecular form. Conclusion The observed patterns of population structure seem to be governed by the presence of both physical (the ocean and biological (the M-S form discontinuity barriers to gene flow. The significant degree of genetic isolation between M and S forms detected by microsatellite loci located outside the "genomic islands" of speciation identified in A. gambiae s.s. further supports the hypothesis of on-going incipient speciation within this species. The implications of these findings regarding vector control strategies are discussed.

  15. Pleistocene dynamics of the Pacific South Equatorial Countercurrent

    Science.gov (United States)

    Nuernberg, D.; Raddatz, J.; Rippert, N.; Tiedemann, R.

    2014-12-01

    The Western Pacific Warm Pool (WPWP) with extremely high sea-surface-temperatures (SST) is a key area for global climate. It also acts as a crossroad for mode and intermediate water masses such as the South Equatorial Countercurrent (SECC) transporting water masses originating from higher latitudes. The SECC flows above the main thermocline and strongly interacts with the Intertropical Convergence Zone (ITCZ) and South Pacific Convergence Zone (SPCZ). To constrain changes in sea-surface and subsurface water mass dynamics affecting thermocline depth, we reconstruct SST, subSST and salinity conditions using combined δ18O and Mg/Ca signals of surface (Globigerinoides ruber, Globigerinoides sacculifer) and subsurface dwelling (Globorotalia tumida) planktonic foraminifera. Our study is based on RV SONNE SO-225 piston cores retrieved from Manihiki plateau, which is located at the southeastern margin of the WPWP (between ~ 5°S-15°S and 170-160°W). The proxy records cover the last ~ 3 Myr SSTMg/Ca remained nearly constant throughout the entire Pleistocene varying between ~30 to 32 (°C), while the subSSTMg/Ca reconstructions reveal pronounced variations from ~10 to 16 (°C). Our results imply that the WPWP thermocline depth has undergone significant vertical movements throughout the Pleistocene. Notably, thermocline depth is continuously decreasing from the early to the late Pleistocene, and coincides with the change from the 41 kyr to a dominant 100 kyr climate periodicity between 1 and 1.7 Ma. We hypothesize that the repeated change in thermocline depth is due to either 1) changes in mode or intermediate water masses advection from Southern Ocean sources via "ocean tunneling", 2) changes in the tropical Pacific wind regime, and/or 3) changes in the Western Pacific Monsoon sytem.

  16. Institution Building for African Regionalism

    OpenAIRE

    Khadiagala, Gilbert M.

    2011-01-01

    Since the 1960s, African states have embraced regional integration as a vital mechanism for political cooperation and for pooling resources to overcome problems of small and fragmented economies. In building meaningful institutions for regionalism, however, Africans have faced the challenges of reconciling the diversities of culture, geography, and politics. As a result, African regional institutions are characterized by multiple and competing mandates and weak institutionalization. This stud...

  17. African Diaspora Associations in Denmark

    DEFF Research Database (Denmark)

    Vammen, Ida Marie; Trans, Lars Ove

    2011-01-01

    Since the early 1990s, an increasing number of African migrants have come to Denmark, where they have formed a large number of migrant associations. This chapter presents selected findings from a comprehensive survey of African diaspora associations in Denmark and focuses specifically on their tr......Since the early 1990s, an increasing number of African migrants have come to Denmark, where they have formed a large number of migrant associations. This chapter presents selected findings from a comprehensive survey of African diaspora associations in Denmark and focuses specifically...

  18. Small Scale Variability of Rain: Impact On Radar Measurement

    Science.gov (United States)

    Gosset, M.; Delrieu, G.

    Most retrieval algorithmes used to convert radar data assume (at least implicitely) that the field observed, rain for example, is uniform within the radar beam. In this presentation we use simple models and simulations tools to analyse some effects of nonuniform beamfilling (NUBF) This study focuses specially on NUBF effects at attenuating frequencies. We find that a combination of non uniform rain and accumulated attenuation can affect the param- eters measured with a radar operating at attenuating wavelength. We analyse how the apparant attenuation is affected and analyse the practical conse- quences on attenuation correction scheme. A second point of interest is polarimetric parameters. We focus in particular on differ- ential polarimetric propagation parameters such as propagation phase shift, which are potentially useful for attenuation correction. We found some interesting and surprising results.

  19. Cometary panspermia explains the red rain of Kerala

    CERN Document Server

    Louis, G; Louis, Godfrey

    2003-01-01

    Red coloured rain occurred in many places of Kerala in India during July to September 2001 due to the mixing of huge quantity of microscopic red cells in the rainwater. Considering its correlation with a meteor airbust event, this phenomenon raised an extraordinary question whether the cells are extraterrestrial. Here we show how the observed features of the red rain phenomenon can be explained by considering the fragmentation and atmospheric disintegration of a fragile cometary body that presumably contains a dense collection of red cells. Slow settling of cells in the stratosphere explains the continuation of the phenomenon for two months. The red cells under study appear to be the resting spores of an extremophilic microorganism. Possible presence of these cells in the interstellar clouds is speculated from its similarity in UV absorption with the 217.5 nm UV extinction feature of interstellar clouds.

  20. A General Systems Theory for Rain Formation in Warm Clouds

    CERN Document Server

    Selvam, A M

    2012-01-01

    A cumulus cloud model which can explain the observed characteristics of warm rain formation in monsoon clouds is presented. The model is based on classical statistical physical concepts and satisfies the principle of maximum entropy production. Atmospheric flows exhibit selfsimilar fractal fluctuations that are ubiquitous to all dynamical systems in nature, such as physical, chemical, social, etc and are characterized by inverse power law form for power (eddy energy) spectrum signifying long-range space-time correlations. A general systems theory model for atmospheric flows developed by the author is based on the concept that the large eddy energy is the integrated mean of enclosed turbulent (small scale) eddies. This model gives scale-free universal governing equations for cloud growth processes. The model predicted cloud parameters are in agreement with reported observations, in particular, the cloud dropsize distribution. Rain formation can occur in warm clouds within 30minutes lifetime under favourable co...

  1. The urban perspectives of acid rain. Workshop summary

    Energy Technology Data Exchange (ETDEWEB)

    Tonn, B.E.

    1993-06-04

    This report documents discussions held during a workshop an Urban Perspective of Acid Rain. The workshop was sponsored by the Office of the Director, National Acid Precipitation Assessment Program (NAPAP). NAPAP anticipates giving increased emphasis to the benefits in urban areas of emissions reductions. The goal of this informal, exploratory workshop was to serve as a first step towards identifying pollutant monitoring, and research and assessment needs to help answer, from an urban perspective, the two key questions posed to NAPAP by Congress: (1) what are the costs, benefits, and effectiveness of the acid rain control program, and (2) what reductions in deposition, rates are needed in order to prevent adverse effects? The workshop addressed research activities needed to respond to these questions. The discussions focused. sequentially, on data needs, data and model availability, and data and modeling gaps. The discussions concentrated on four areas of effects: human health, materials, urban forests, and visibility.

  2. Activity of earthworm in Latosol under simulated acid rain stress.

    Science.gov (United States)

    Zhang, Jia-En; Yu, Jiayu; Ouyang, Ying

    2015-01-01

    Acid rain is still an issue of environmental concerns. This study investigated the impacts of simulated acid rain (SAR) upon earthworm activity from the Latosol (acidic red soil). Laboratory experiment was performed by leaching the soil columns grown with earthworms (Eisenia fetida) at the SAR pH levels ranged from 2.0 to 6.5 over a 34-day period. Results showed that earthworms tended to escape from the soil and eventually died for the SAR at pH = 2.0 as a result of acid toxicity. The catalase activity in the earthworms decreased with the SAR pH levels, whereas the superoxide dismutases activity in the earthworms showed a fluctuate pattern: decreasing from pH 6.5 to 5.0 and increasing from pH 5.0 to 4.0. Results implied that the growth of earthworms was retarded at the SAR pH ≤ 3.0.

  3. Fluoride contamination in rain water of Sigrauli region

    Energy Technology Data Exchange (ETDEWEB)

    Chaurasia, S.; Mishra, S.K. [Mahatma Gandhi Chitrakoot Gramodaya, Chitrakoot (India)

    2007-07-01

    In this paper fluoride was monitored in rain water during rainy season at seven locations of Sigrauli region in 2004. The sampling location covered the impact of industrial complex of the area, and its impact on surface water sources monitored for the fluoride, pH, and electrical conductivity. The higher concentration of fluoride in rain water was observed 2.03 mg/L at Dudhar and in ponds water highest value was 3.14 mg/L. This suggested that serious fluoride pollution is occurring in Singrauli region posing a threat to the health and livelihood of the people of the region. Fluoride transported by the air route from coal burning emissions of large thermal power plants concentrate in small geographical area, and industries. Fluoride pollution in Singrauli area deserve intensive scientific studies and urgent attention. 2 figs., 2 tabs.

  4. Towards the Atlas of human African trypanosomiasis

    Directory of Open Access Journals (Sweden)

    Mattioli Raffaele C

    2009-03-01

    Full Text Available Abstract Background Updated, accurate and comprehensive information on the distribution of human African trypanosomiasis (HAT, also known as sleeping sickness, is critically important to plan and monitor control activities. We describe input data, methodology, preliminary results and future prospects of the HAT Atlas initiative, which will allow major improvements in the understanding of the spatial distribution of the disease. Methods Up-to-date as well as historical data collected by national sleeping sickness control programmes, non-governmental organizations and research institutes have been collated over many years by the HAT Control and Surveillance Programme of the World Health Organization. This body of information, unpublished for the most part, is now being screened, harmonized, and analysed by means of database management systems and geographical information systems (GIS. The number of new HAT cases and the number of people screened within a defined geographical entity were chosen as the key variables to map disease distribution in sub-Saharan Africa. Results At the time of writing, over 600 epidemiological reports and files from seventeen countries were collated and included in the data repository. The reports contain information on approximately 20,000 HAT cases, associated to over 7,000 different geographical entities. The oldest epidemiological records considered so far date back to 1985, the most recent having been gathered in 2008. Data from Cameroon, Central African Republic, Chad, Congo, Equatorial Guinea and Gabon from the year 2000 onwards were fully processed and the preliminary regional map of HAT distribution is presented. Conclusion The use of GIS tools and geo-referenced, village-level epidemiological data allow the production of maps that substantially improve on the spatial quality of previous cartographic products of similar scope. The significant differences between our preliminary outputs and earlier maps of HAT

  5. Northeast Asia acid rain problem and environmental cooperation

    Energy Technology Data Exchange (ETDEWEB)

    Shin, E.S. [Yonsei University, Seoul (Korea, Republic of)

    1997-09-01

    Total emission amounts of sulfur dioxide in the twenty-three (23) territories of Northeast Asia was 14.7 million tons in 1990. The Northeastern area of China accounted for 81%, Korea 12%, Japan 5%, and North Korea 2%. In the basic scenario, the emission amount of sulfur dioxide in Northeast Asia is estimated to reach 40.5 million tons by the year 2020. Long distance, cross-border air pollutants originating in China, move to the Korean Peninsula and Japan, and esp. acid rain is greatly influenced by the emission of sulfur dioxide in China. Acid rain severely damages not only the natural ecosystem and agricultural products, but also human health, too. Therefore, in order to reduce the future damage from acid rain, emission of sulfur dioxide and nitric oxide material should be lessened both domestically and in nearby countries. It would be difficult for those countries in Northeast Asia to sign the multilateral agreement for environmental cooperation within a short period of time because they are in different stages of economic development and set different priorities in their discussion of environmental cooperation. Therefore, it is desirable to make them observe improved environmental standards through existing regional cooperative organizations such as ESCAP, APEC or multilateral external financial institutions such as IBRD, ADB, ODA, and to carry out cooperative businesses for regional environmental improvements. At the same time, environmental cooperation in Northeast Asia related to acid rain should start step by step from obtaining objective and reliable information through scientific studies and should be carried out multi-dimensionally and comprehensively by not only the central government but the local government and NGO in various fields, such as Politics, Economics, Science, Diplomacy, etc. 30 refs., 1 fig., 5 tabs.

  6. Attenuation of 3CM Microwaves Due to Artificial Rain

    Directory of Open Access Journals (Sweden)

    J. K. Singh

    1966-04-01

    Full Text Available Observations to study the variation of attenuation of 3cm waves due to falling of water or artificial rain are confined to the high rates of precipitation and short distance between the transmitter and receiver, due to low power of the microwave generator. A comparison of these observations and those recorded by others shows that the attenuation increases nonlinearly with the intensity of artificial rainfall which is generally assumed to be linear for the observations at lower rates of precipitation.

  7. THE ENERGETIC AGGREGATION AND RELEASE IN THE HEAVY RAIN REGION

    Institute of Scientific and Technical Information of China (English)

    ZHOU Hai-guang; LIU Hai-tao; LIU Yan-ying

    2006-01-01

    Using the new formula of moist available energy (MAE), the value of the MAE's key terms of three heavy rainfall cases in Guangdong province in 1998 was calculated. The energetic aggregation and energetic discharge are analyzed. It shows that the value of the key terms in the formula appears different feature clearly in the different precipitation period, as well as the function of each term presents in the heavy rain region.

  8. Distance in spatial interpolation of daily rain gauge data

    OpenAIRE

    Ahrens, B.

    2006-01-01

    Spatial interpolation of rain gauge data is important in forcing of hydrological simulations or evaluation of weather predictions, for example. This paper investigates the application of statistical distance, like one minus common variance of observation time series, between data sites instead of geographical distance in interpolation. Here, as a typical representative of interpolation methods the inverse distance weighting interpolation is applied and the test data is daily precipitation obs...

  9. Interpretation of SoilData from the Rain Project

    OpenAIRE

    Reuss, J. O.

    1989-01-01

    Process-oriented models for prediction of soil and water acidification at the catchment scale require soil chemical and physical data as input parameters. Choice of soil properties characteristic for an entire catchment poses a major dilemma. This report deals with the interpretation of analyses from about 200 soils samples collected 1983-86 from the 7 catchments included in the RAIN project (Reversing Acidification In Norway). Various statistical techniques are used to derive characteristic ...

  10. The Waste Land in Henderson the Rain King

    Institute of Scientific and Technical Information of China (English)

    童燕芳

    2009-01-01

    As a quest for "out of the waste land",Henderson the Rain King presents a vivid picture of the modem spiritual waste land.The current paper concludes a general view of the waste land by studying Henderson's instinctive feeling and complaint about the world and his life,and also analyzes Henderson's individual case from the perspective of neurotic theory,for his mental crises is rather representative in his time.

  11. Observing the formation of flare-driven coronal rain

    OpenAIRE

    Scullion, E.; Rouppe van der Voort, L.; Antolin, P.; Wedemeyer, S.; Vissers, G.; E. P. Kontar; Gallagher, P

    2016-01-01

    PA. GV are funded by the European Research Council under the European Union Seventh Framework Programme (FP7/2007-2013) / ERC grant agreement nr. 291058 Flare-driven coronal rain can manifest from rapidly cooled plasma condensations near coronal loop-tops in thermally unstable post-flare arcades. We detect 5 phases that characterise the post-flare decay:heating, evaporation, conductive cooling dominance for ~120 s, radiative/ enthalpy cooling dominance for ~4700 s and finally catastrophic ...

  12. [Effects of simulated acid rain on water physiological characteristics of Myrica rubra seedlings].

    Science.gov (United States)

    Yaho, Zhao-bin; Jiang, Hong; Yu, Shu-quan; Lu, Mei-juan

    2011-08-01

    Taking the seedlings of typical subtropical economic tree species Myrica rubra in Zhejiang Province as test materials, a pot experiment was conducted to study their water physiological characteristics under effects of simulated acid rain (pH 2.5 and pH 4.0), with water (pH 5.6) as the control. Season, year, and acid rain all had significant effects on the photosynthetic rate (Pn). Among the treatments, the Pn had a greater difference in summer than in spring and autumn, and was higher in treatment acid rain (pH 4.0). Season, year, acid rain, and the interactions of season and year and of the three factors had significant effects on the stomata conductance (Gs), and also, the Gs had a greater difference among the treatments in summer than in spring and autumn. Acid rain had inhibitory effect on Gs. Season, year, acid rain, and the interactions of season and year and of season and acid rain affected the transpiration rate (Tr) significantly. Same as Pn and Gs, the Tr had a greater difference among the treatments in summer than in spring and autumn. Acid rain (pH 2.5) had the strongest inhibitory effect on Tr. Acid rain and the interactions of season and year and of season and acid rain had significant effects on the water use efficiency (WUE), and acid rain (pH 2.5) had definitely positive effect on the WUE.

  13. Phenomena associated with rain deposition of radon daughters

    Energy Technology Data Exchange (ETDEWEB)

    Fujitaka, Kazunobu [National Inst. of Radiological Sciences, Chiba (Japan)

    1997-02-01

    Since Rn daughter nuclides generated from Rn gas in the air are generally absorbed on aerosol, its radioactivities are apt to deposit onto the ground with raindrop. Here, the effects of raining on the radiation level were investigated. The amount of precipitation was determined using a highly sensitive rain gauge (the nominal sensitivity of 0.0043 mm) and air radioactive level was measured using a scintillation monitor of 2``{phi}x2``NaI(Tl) which was set at 1.5 m height above the ground. The rising of {gamma}-radiation level associated with rainfall was expressed as percentage of the base line activity. The radiation level increased depending on the intervals between the successive rainfalls and the increase of radioactivity from base line was greater when the rainfall interval was less than 12 hours. Therefore, the amount of radiation deposit was suggested to be small when the rainfall interval is short. Ordinarily, the increase of air radiation level caused by rain deposition was thought to be within a range of 20-50%. (M.N.)

  14. Distance in spatial interpolation of daily rain gauge data

    Directory of Open Access Journals (Sweden)

    B. Ahrens

    2006-01-01

    Full Text Available Spatial interpolation of rain gauge data is important in forcing of hydrological simulations or evaluation of weather predictions, for example. This paper investigates the application of statistical distance, like one minus common variance of observation time series, between data sites instead of geographical distance in interpolation. Here, as a typical representative of interpolation methods the inverse distance weighting interpolation is applied and the test data is daily precipitation observed in Austria. Choosing statistical distance instead of geographical distance in interpolation of available coarse network observations to sites of a denser network, which is not reporting for the interpolation date, yields more robust interpolation results. The most distinct performance enhancement is in or close to mountainous terrain. Therefore, application of statistical distance in the inverse distance weighting interpolation or in similar methods can parsimoniously densify the currently available observation network. Additionally, the success further motivates search for conceptual rain-orography interaction models as components of spatial rain interpolation algorithms in mountainous terrain.

  15. Introducing Pico Hydro From Daily Used Water And Rain Water

    Directory of Open Access Journals (Sweden)

    Rashed Al Amin

    2014-01-01

    Full Text Available Demand for energy is increasing day by day because of increasing the population and industrialization. But, the over usage of electrical energy may cause power crisis. So, there is a need to develop the methods of optimal utilization which decreases the over usage of energy and try to work as positive catalyst in stable environment. This paper shows the possibility of tapping the wasted energy from daily used water and rain water. The wasted energy of daily used water and rain water can be converted into the electrical energy by hydro electric mechanism through several energy conversion processes. There is also obtained the electrical energy is in KW range, which is sufficient to lighten a garage of multi storeyed building or small needs of home. The generated electricity is stored in a battery for any future uses. As the increasing of daily used water and rain water on roof, the designed system will be effective to decrease the power crisis of Bangladesh to some extent.

  16. Physical initialization using SSM/I rain rates

    Science.gov (United States)

    Krishnamurti, T. N.; Bedi, H. S.; Ingles, Kevin

    1993-01-01

    Following our recent study on physical initialization for tropical prediction using rain rates based on outgoing long-wave radiation, the present study demonstrates a major improvement from the use of microwave radiance-based rain rates. A rain rate algorithm is used on the data from a special sensor microwave instrument (SSM/I). The initialization, as before, uses a reverse surface similarity theory, a reverse cumulus parameterization algorithm, and a bisection method to minimize the difference between satellite-based and the model-based outgoing long-wave radiation. These are invoked within a preforecast Newtonian relaxation phase of the initialization. These tests are carried out with a high-resolution global spectral model. The impact of the initialization on forecast is tested for a complex triple typhoon scenario over the Western Pacific Ocean during September 1987. A major impact from the inclusion of the SSM/I is demonstrated. Also addressed are the spin-up issues related to the typhoon structure and the improved water budget from the physical initialization.

  17. Precipitation Type Specific Radar Reflectivity-Rain Rate Relationships for Warsaw, Poland

    Science.gov (United States)

    Licznar, Paweł; Krajewski, Witold F.

    2016-10-01

    Implementation of weather radar precipitation estimates into hydrology, especially urban hydrology practice in Poland, requires the introduction of more precise radar reflectivity versus rain rate (Z-R) relationships accounting for drop size distribution (DSD) specific for different precipitation phases. We explored the development of precipitation type dependent Z-R relationship on the basis of approximately two years of DSD recordings at high temporal resolution of ten seconds. We divided the recorded data into four separate precipitation-type groups: rain, snow, rain-with-snow, and hail. The Z-R relationships for rain and rainwith- snow showed a strong resemblance to the well-known Marshall- Palmer Z-R power-type relationship for rain. In the case of snowfall, we found that both the multiplication factor and the exponent coefficients in the Z-R formula have smaller values than for rain. In contrast, for hail precipitation these parameters are higher than for rain, especially the multiplication factor.

  18. CLIMATOLOGICAL VARIATION OF GLOBAL CROSS-EQUATORIAL FLOWS FOR THE PERIOD 1948-2004

    Institute of Scientific and Technical Information of China (English)

    SHI Neng; FENG Guo-lin; GU Jun-qiang; GU De-jun; YU Jin-Hua

    2007-01-01

    By using monthly NCEP/NCAR meridional gridpoint wind data at the levels of 1000, 850, 700,600, 500, 400, 300, 200, 150 and 100 hPa from 1948 to 2004, the intensity of global cross-equatorial flows is calculated. The spatial and temporal variation of global cross-equatorial flows at the 850-hPa level are shown and discussed. The results show that the strength of the 850-hPa global cross-equatorial flows represent obvious long-term variation and interdecadal change during the period. Evidence suggests that the cross-equatorial flow of the passages at 45 - 50 °E in June to August, 105 - 115 °E in May to September,130 - 140 °E in May to September and May to November and 20 - 25 °E in February to April intensified and that the cross-equatorial flow of the passages at 50 - 35 °W in June to August weaken in the past 57 years, with an increase of 0.25m/s/10a for summer Somali Jet and increase of 0.32 m/s/10a for crossequatorial flow at 130 - 140 °E in May to September The results of Singular Spectrum Analysis (SSA) for the time series indicate that for the cross-equatorial flow at 850 hPa, the interdecadal and long-term trend changes are 35% - 45%, and the interannual variation is no more than 30%, in variance contribution. The results also reveal that the interannual variation of intensity of the summer cross-equatorial flows in the Pacific is significantly correlated with Southern Oscillation. With weak Southern Oscillation, strong crossequatorial flows in Pacific will happen, though the summer Somali Jet is only a little positively correlated with North Atlantic Oscillation (NAD).

  19. Extra-tropical origin of equatorial Pacific cold bias in climate models

    Science.gov (United States)

    Burls, N.; Muir, L.; Vincent, E. M.; Fedorov, A. V.

    2015-12-01

    General circulation models frequently suffer from a substantial cold bias in equatorial Pacific sea surface temperatures (SSTs). For instance, the majority of the climate models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5) have this particular problem (17 out of the 26 models evaluated in this project). Our study investigates the extent to which these equatorial cold biases are related to mean climate biases generated in the extra-tropics and then communicated to the equator via the oceanic subtropical cells (STCs). With an evident relationship across the CMIP5 models between equatorial SSTs and upper ocean temperatures in the extra-tropical subduction regions, our analysis confirms that cold SST biases within the extra-tropical Pacific translate into a cold equatorial SST bias via the STCs. An assessment of the relationship between these extra-tropical SST biases and surface heat flux components indicates a link to biases in the simulated shortwave fluxes. Further sensitivity studies with a climate model (CESM) in which extra-tropical cloud albedo is systematically varied illustrate the influence of cloud albedo perturbations, not only directly above the oceanic subduction regions but across the extended extra-tropical Pacific, on the equatorial bias. The CESM experiments reveal a quadratic relationship between extra-tropical albedo and the root-mean-square-error in equatorial SSTs - a relationship with which the CMIP5 models generally agree. Thus, our study suggests that one way to improve the equatorial cold bias is to improve the representation of cloud albedo in mid-latitudes.

  20. Multiple embryos, multiple nepionts and multiple equatorial layers in Cycloclypeus carpenteri.

    Science.gov (United States)

    Briguglio, Antonino; Kinoshita, Shunichi; Wolfgring, Erik; Hohenegger, Johann

    2016-04-01

    In this study, 17 specimens of Cycloclypeus carpenteri have been analyzed by means of microCT scanning. We used CT scanning technique as it enables the visualization and the quantifications of internal structures of hollow specimens without their destruction. It has been observed that many specimens possessing the natural morphology of this taxon, actually contain multiple embryos (up to 16 in one single specimen) and, in some few cases, multiple nepionts each with its own heterosteginid chambers (up to three separated nepionts). The diameter of each proloculus has been measured, and as a result, they are very variable even within the same specimen, therefore questioning the long known theory that schizonts have smaller proloculi than gamonts and also questioning the fact that proloculi in the same species should all have comparable size. Furthermore, we have observed the presence of additional equatorial planes on several specimens. Such additional planes are always connected to what seems to be the main equatorial plane. Such connections are T-shaped and are located at the junction between two equatorial layers; these junctions are made by a chamberlet, which possesses an unusually higher number of apertures. The connections between equatorial planes are always perfectly synchronized with the relative growth step and the same chamber can be therefore followed along the multiple equatorial planes. Apparently there is a perfect geometric relationship between the creation of additional equatorial planes and the position of the nepionts. Whenever the nepionts are positioned on different planes, additional planes are created and the angle of the nepionts is related to the banding angle of the equatorial planes. The presence of additional planes do not hamper the life of the cell, on the contrary, it seems that the cell is still able to build nicely shaped chamberlets and, after volumetric calculations, it seems all specimens managed to keep their logistic growth

  1. Global distribution of equatorial plasma bubbles in the premidnight sector during solar maximum as observed by KOMPSAT-1 and Defense Meteorological Satellite Program F15

    Science.gov (United States)

    Park, Jaeheung; Min, Kyoung Wook; Kim, Vitaly P.; Kil, Hyosub; Lee, Jae-Jin; Kim, Hee-Jun; Lee, Ensang; Lee, Dae Young

    2005-07-01

    We investigated the global distribution of equatorial plasma bubbles (EPBs) using in situ plasma density measurements from Korea Multipurpose Satellite-1 (KOMPSAT-1) and Defense Meteorological Satellite Program (DMSP) F15 during the solar maximum period from June 2000 to August 2001. The results were generally consistent with those of previous studies. EPBs were observed at all longitudes around the magnetic dip equator in the equinoctial seasons with the peak occurrence in the American-Atlantic-African regions. During the June solstice, EPBs occurred predominantly in the African sector, with enhancements in the magnetic north in the Indian and west Pacific regions, but were totally suppressed in the American-Atlantic sector. During the December solstice, EPBs occurred frequently in the American-Atlantic sector but were suppressed in the other longitude sectors, especially in the Pacific sector. The EPB occurrence probability was seen to be correlated with the observed topside plasma density and the model prereversal upward drift speed of ambient plasmas (Fejer et al., 1999), with their respective dominance dependent on the seasons. However, the peak EPB occurrence in the American-Atlantic sector during the December solstice was displaced somewhat from the region of peak density and upward drift, probably due to a strong solar terminator influence on the flux tube-integrated E region Pedersen conductivity and due to anomaly morphology. The peak EPB occurrence in the African sector during the June solstice is consistent only with the high ambient density in that region, for there was no coincidence with the maximum vertical drift or the minimum E region Pedersen conductivity.

  2. Evolution in African tropical trees displaying ploidy-habitat association: The genus Afzelia (Leguminosae).

    Science.gov (United States)

    Donkpegan, Armel S L; Doucet, Jean-Louis; Migliore, Jérémy; Duminil, Jérôme; Dainou, Kasso; Piñeiro, Rosalía; Wieringa, Jan J; Champluvier, Dominique; Hardy, Olivier J

    2017-02-01

    Polyploidy has rarely been documented in rain forest trees but it has recently been found in African species of the genus Afzelia (Leguminosae), which is composed of four tetraploid rain forest species and two diploid dry forest species. The genus Afzelia thus provides an opportunity to examine how and when polyploidy and habitat shift occurred in Africa, and whether they are associated. In this study, we combined three plastid markers (psbA, trnL, ndhF), two nuclear markers (ribosomal ITS and the single-copy PEPC E7 gene), plastomes (obtained by High Throughput Sequencing) and morphological traits, with an extensive taxonomic and geographic sampling to explore the evolutionary history of Afzelia. Both nuclear DNA and morphological vegetative characters separated diploid from tetraploid lineages. Although the two African diploid species were well differentiated genetically and morphologically, the relationships among the tetraploid species were not resolved. In contrast to the nuclear markers, plastid markers revealed that one of the diploid species forms a well-supported clade with the tetraploids, suggesting historical hybridisation, possibly in relation with genome duplication (polyploidization) and habitat shift from dry to rain forests. Molecular dating based on fossil-anchored gene phylogenies indicates that extant Afzelia started diverging c. 14.5 or 20Ma while extant tetraploid species started diverging c. 7.0 or 9.4Ma according to plastid and nuclear DNA, respectively. Additional studies of tropical polyploid plants are needed to assess whether the ploidy-habitat association observed in African Afzelia would reflect a role of polyploidization in niche divergence in the tropics.

  3. The African Diaspora, Civil Society and African Integration

    DEFF Research Database (Denmark)

    Opoku-Mensah, Paul Yaw

    This paper, a work-in-progress, makes a contribution to the discussions on the appropriate modalities for incorporating the African diaspora in the African integration project.  It argues that the most appropriate entry points for incorporating the African diaspora into the integration project...... might not, necessarily, be in the formal political structures, although this is important. To the contrary, the most effective and sustainable might be within civil society---that is the links between the peoples and organizations of Africa and the diaspora. Using the case of the African academy......-- as an institution of civil society--- the paper outlines a conceptual framework for incorporating the diaspora into the African integration project....

  4. Rain Characteristics and Large-Scale Environments of Precipitation Objects with Extreme Rain Volumes from TRMM Observations

    Science.gov (United States)

    Zhou, Yaping; Lau, William K M.; Liu, Chuntao

    2013-01-01

    This study adopts a "precipitation object" approach by using 14 years of Tropical Rainfall Measuring Mission (TRMM) Precipitation Feature (PF) and National Centers for Environmental Prediction (NCEP) reanalysis data to study rainfall structure and environmental factors associated with extreme heavy rain events. Characteristics of instantaneous extreme volumetric PFs are examined and compared to those of intermediate and small systems. It is found that instantaneous PFs exhibit a much wider scale range compared to the daily gridded precipitation accumulation range. The top 1% of the rainiest PFs contribute over 55% of total rainfall and have 2 orders of rain volume magnitude greater than those of the median PFs. We find a threshold near the top 10% beyond which the PFs grow exponentially into larger, deeper, and colder rain systems. NCEP reanalyses show that midlevel relative humidity and total precipitable water increase steadily with increasingly larger PFs, along with a rapid increase of 500 hPa upward vertical velocity beyond the top 10%. This provides the necessary moisture convergence to amplify and sustain the extreme events. The rapid increase in vertical motion is associated with the release of convective available potential energy (CAPE) in mature systems, as is evident in the increase in CAPE of PFs up to 10% and the subsequent dropoff. The study illustrates distinct stages in the development of an extreme rainfall event including: (1) a systematic buildup in large-scale temperature and moisture, (2) a rapid change in rain structure, (3) explosive growth of the PF size, and (4) a release of CAPE before the demise of the event.

  5. A Campaign to Study Equatorial Ionospheric Phenomena over Guam

    Science.gov (United States)

    Habash Krause, L.; Balthazor, R.; Dearborn, M.; Enloe, L.; Lawrence, T.; McHarg, M.; Petrash, D.; Reinisch, B. W.; Stuart, T.

    2007-05-01

    With the development of a series of ground-based and space-based experiments, the United States Air Force Academy (USAFA) is in the process of planning a campaign to investigate the relationship between equatorial ionospheric plasma dynamics and a variety of space weather effects, including: 1) ionospheric plasma turbulence in the F region, and 2) scintillation of radio signals at low latitudes. A Digisonde Portable Sounder DPS-4 will operate from the island of Guam (with a magnetic latitude of 5.6° N) and will provide measurements of ionospheric total electron content (TEC), vertical drifts of the bulk ionospheric plasma, and electron density profiles. Additionally, a dual-frequency GPS TEC/scintillation monitor will be located along the Guam magnetic meridian at a magnetic latitude of approximately 15° N. In campaign mode, we will combine these ground-based observations with those collected from space during USAFA's FalconSAT-3 and FalconSAT-5 low-earth orbit satellite missions, the first of which is scheduled to be active over a period of several months beginning in the 2007 calendar year. The satellite experiments are designed to characterize in situ irregularities in plasma density, and include measurements of bulk ion density and temperature, minority-to- majority ion mixing ratios, small scale (10 cm to 1 m) plasma turbulence, and ion distribution spectra in energy with sufficient resolution for observations of non-thermalized distributions that may be associated with velocity- space instabilities. Specific targets of investigation include: a) a comparison of plasma turbulence observed on- orbit with spread F on ionograms as measured with the Digisonde, b) a correlation between the vertical lifting of the ionospheric layer over Guam and the onset of radio scintillation activity along the Guam meridian at 15° N magnetic latitude, and c) a correlation between on-orbit turbulence and ionospheric scintillation at 15° N magnetic latitude. These relationships

  6. Guest investigator program study: Physics of equatorial plasma bubbles

    Science.gov (United States)

    Tsunoda, Roland T.

    1994-01-01

    Plasma bubbles are large-scale (10 to 100 km) depletions in plasma density found in the night-time equatorial ionosphere. Their formation has been found to entail the upward transport of plasma over hundreds of kilometers in altitude, suggesting that bubbles play significant roles in the physics of many of the diverse and unique features found in the low-latitude ionosphere. In the simplest scenario, plasma bubbles appear first as perturbations in the bottomside F layer, which is linearly unstable to the gravitationally driven Rayleigh-Taylor instability. Once initiated, bubbles develop upward through the peak of the F layer into its topside (sometimes to altitudes in excess of 1000 km), a behavior predicted by the nonlinear form of the same instability. While good general agreement has been found between theory and observations, little is known about the detailed physics associated with plasma bubbles. Our research activity centered around two topics: the shape of plasma bubbles and associated electric fields, and the day-to-day variability in the occurrence of plasma bubbles. The first topic was pursued because of a divergence in view regarding the nonlinear physics associated with plasma bubble development. While the development of perturbations in isodensity contours in the bottomside F layer into plasma bubbles is well accepted, some believed bubbles to be cylinder-like closed regions of depleted plasma density that floated upward leaving a turbulent wake behind them (e.g., Woodman and LaHoz, 1976; Ott, 1978; Kelley and Ott, 1978). Our results, summarized in a paper submitted to the Journal of Geophysical Research, consisted of incoherent scatter radar measurements that showed unambiguously that the depleted region is wedgelike and not cylinderlike, and a case study and modeling of SM-D electric field instrument (EFI) measurements that showed that the absence of electric-field perturbations outside the plasma-depleted region is a distinct signature of wedge

  7. Characteristics of equatorial electrojet derived from Swarm satellites

    Science.gov (United States)

    Thomas, Neethal; Vichare, Geeta; Sinha, A. K.

    2017-03-01

    The vector magnetic field measurements from three satellite constellation, Swarm mission (Alpha 'Swarm-A', Bravo 'Swarm-B', and Charlie 'Swarm-C') during the quiet days (daily ∑Kp ⩽ 10) of the years 2014-2015 are used to study the characteristic features of equatorial electrojet (EEJ). A program is developed to identify the EEJ signature in the X (northward) component of the magnetic field recorded by the satellite. An empirical model is fitted into the observed EEJ signatures separately for both the hemispheres, to obtain the parameters of electrojet current such as peak current density, total eastward current, the width of EEJ, position of the electrojet axis, etc. The magnetic field signatures of EEJ at different altitudes are then estimated. Swarm B and C are orbiting at different heights (separation ∼50 km) and during the month of April 2014, both the satellites were moving almost simultaneously over nearby longitudes. Therefore, we used those satellite passes to validate the methodology used in the present study. The magnetic field estimates at the location of Swarm-C obtained using the observations of Swarm B are compared with the actual observations of Swarm-C. A good correlation between the actual and the computed values (correlation coefficient = 0.98) authenticates the method of analysis. The altitudinal variation of the amplitude and the width of the EEJ signatures are also depicted. The ratio of the total eastward flowing forward to westward return currents is found to vary between 0.1 and 1.0. The forward and return current values in the northern hemisphere are found to be ∼0.5 to 2 times of those in the southern hemisphere, thereby indicating the hemispheric asymmetry. The latitudinal extents of the forward and return currents are found to have longitudinal dependence similar to that of the amplitude and the width of EEJ showing four peak structures. Local time dependence of EEJ parameters has also been investigated. In general, the results

  8. Halocarbon emissions and sources in the equatorial Atlantic Cold Tongue

    Directory of Open Access Journals (Sweden)

    H. Hepach

    2015-04-01

    Full Text Available Halocarbons from oceanic sources contribute to halogens in the troposphere, and can be transported into the stratosphere where they take part in ozone depletion. This paper presents distribution and sources in the equatorial Atlantic from June and July 2011 of the four compounds bromoform (CHBr3, dibromomethane (CH2Br2, methyl iodide (CH3I and diiodomethane (CH2I2. Enhanced biological production during the Atlantic Cold Tongue (ACT season, indicated by phytoplankton pigment concentrations, led to elevated concentrations of CHBr3 of up to 44.7 pmol L−1 and up to 9.2 pmol L−1 for CH2Br2 in surface water, which is comparable to other tropical upwelling systems. While both compounds correlated very well with each other in the surface water,CH2Br2 was often more elevated in greater depth than CHBr3, which showed maxima in the vicinity of the deep chlorophyll maximum. The deeper maximum of CH2Br2 indicates an additional source in comparison to CHBr3 or a slower degradation of CH2Br2. Concentrations of CH3I of up to 12.8 pmol L−1 in the surface water were measured. In contrary to expectations of a predominantly photochemical source in the tropical ocean, its distribution was mostly in agreement with biological parameters, indicating a~biological source. CH2I2 was very low in the near surface water with maximum concentrations of only 3.7 pmol L−1, and the observed anticorrelation with global radiation was likely due to its strong photolysis. CH2I2 showed distinct maxima in deeper waters similar to CH2Br2. For the first time, diapycnal fluxes of the four halocarbons from the upper thermocline into and out of the mixed layer were determined. These fluxes were low in comparison to the halocarbon sea-to-air fluxes. This indicates that despite the observed maximum concentrations at depth, production in the surface mixed layer is the main oceanic source for all four compounds and has an influence on emissions into the atmosphere. The calculated

  9. No iron fertilization in the equatorial Pacific Ocean during the last ice age.

    Science.gov (United States)

    Costa, K M; McManus, J F; Anderson, R F; Ren, H; Sigman, D M; Winckler, G; Fleisher, M Q; Marcantonio, F; Ravelo, A C

    2016-01-28

    The equatorial Pacific Ocean is one of the major high-nutrient, low-chlorophyll regions in the global ocean. In such regions, the consumption of the available macro-nutrients such as nitrate and phosphate is thought to be limited in part by the low abundance of the critical micro-nutrient iron. Greater atmospheric dust deposition could have fertilized the equatorial Pacific with iron during the last ice age--the Last Glacial Period (LGP)--but the effect of increased ice-age dust fluxes on primary productivity in the equatorial Pacific remains uncertain. Here we present meridional transects of dust (derived from the (232)Th proxy), phytoplankton productivity (using opal, (231)Pa/(230)Th and excess Ba), and the degree of nitrate consumption (using foraminifera-bound δ(15)N) from six cores in the central equatorial Pacific for the Holocene (0-10,000 years ago) and the LGP (17,000-27,000 years ago). We find that, although dust deposition in the central equatorial Pacific was two to three times greater in the LGP than in the Holocene, productivity was the same or lower, and the degree of nitrate consumption was the same. These biogeochemical findings suggest that the relatively greater ice-age dust fluxes were not large enough to provide substantial iron fertilization to the central equatorial Pacific. This may have been because the absolute rate of dust deposition in the LGP (although greater than the Holocene rate) was very low. The lower productivity coupled with unchanged nitrate consumption suggests that the subsurface major nutrient concentrations were lower in the central equatorial Pacific during the LGP. As these nutrients are today dominantly sourced from the Subantarctic Zone of the Southern Ocean, we propose that the central equatorial Pacific data are consistent with more nutrient consumption in the Subantarctic Zone, possibly owing to iron fertilization as a result of higher absolute dust fluxes in this region. Thus, ice-age iron fertilization in the

  10. No iron fertilization in the equatorial Pacific Ocean during the last ice age

    Science.gov (United States)

    Costa, K. M.; McManus, J. F.; Anderson, R. F.; Ren, H.; Sigman, D. M.; Winckler, G.; Fleisher, M. Q.; Marcantonio, F.; Ravelo, A. C.

    2016-01-01

    The equatorial Pacific Ocean is one of the major high-nutrient, low-chlorophyll regions in the global ocean. In such regions, the consumption of the available macro-nutrients such as nitrate and phosphate is thought to be limited in part by the low abundance of the critical micro-nutrient iron. Greater atmospheric dust deposition could have fertilized the equatorial Pacific with iron during the last ice age—the Last Glacial Period (LGP)—but the effect of increased ice-age dust fluxes on primary productivity in the equatorial Pacific remains uncertain. Here we present meridional transects of dust (derived from the 232Th proxy), phytoplankton productivity (using opal, 231Pa/230Th and excess Ba), and the degree of nitrate consumption (using foraminifera-bound δ15N) from six cores in the central equatorial Pacific for the Holocene (0-10,000 years ago) and the LGP (17,000-27,000 years ago). We find that, although dust deposition in the central equatorial Pacific was two to three times greater in the LGP than in the Holocene, productivity was the same or lower, and the degree of nitrate consumption was the same. These biogeochemical findings suggest that the relatively greater ice-age dust fluxes were not large enough to provide substantial iron fertilization to the central equatorial Pacific. This may have been because the absolute rate of dust deposition in the LGP (although greater than the Holocene rate) was very low. The lower productivity coupled with unchanged nitrate consumption suggests that the subsurface major nutrient concentrations were lower in the central equatorial Pacific during the LGP. As these nutrients are today dominantly sourced from the Subantarctic Zone of the Southern Ocean, we propose that the central equatorial Pacific data are consistent with more nutrient consumption in the Subantarctic Zone, possibly owing to iron fertilization as a result of higher absolute dust fluxes in this region. Thus, ice-age iron fertilization in the

  11. A Call to African Unity

    DEFF Research Database (Denmark)

    Muchie, Mammo

    This month's paper, written by Professor Mammo Muchie, examines the necessity for a pan-African monetary union.  Professor Muchie argues for the "the creation of a unified African strategy and unified approach to dealing with the outside donor world by neutralising the poison of money as honey...

  12. African Conservation Tillage Network Website

    OpenAIRE

    African Conservation Tillage Network (ACT)

    2009-01-01

    Metadata only record Maintained by the African Conservation Tillage Network (ACT), this website provides information on Conservation Agriculture in an African context and gathered by stakeholders (NGOs) native to the continent. Resources on projects, practices, reports, and training courses are provided.

  13. Booster for African Economy

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    China’s investment is fueling African growth SINCE 2000,driven by the Forum on China-Africa Cooperation,China’s foreign direct investment(FDI) in Africa has been growing rapidly.In the face of the global financial crisis,which led to global FDI flows falling,China’s investment in Africa has been on a steady, upbeat rise without any interruption.In 2009,China’s direct investment in Africa reached $1.44 billion,of which nonfinancial direct investment soared by 55.4 percent from the previous year.Africa

  14. Impact of East Asian winter monsoon on MJO over the equatorial western Pacific

    Science.gov (United States)

    Chen, Xiong; Li, Chongyin; Ling, Jian; Tan, Yanke

    2017-02-01

    This paper investigates the processes and mechanisms by which the East Asian winter monsoon (EAWM) affects the Madden-Julian oscillation (MJO) over the equatorial western Pacific in boreal winter (November-April). The results show that both the EAWM and MJO over the equatorial western Pacific have prominent interannual and interdecadal variabilities, and they are closely related, especially on the interannual timescales. The EAWM influences MJO via the feedback effect of convective heating, because the strong northerlies of EAWM can enhance the ascending motion and lead the convection to be strengthened over the equatorial western Pacific by reinforcing the convergence in the lower troposphere. Daily composite analysis in the phase 4 of MJO (i.e., strong MJO convection over the Maritime Continent and equatorial western Pacific) shows that the kinetic energy, outgoing longwave radiation (OLR), moisture flux, vertical velocity, zonal wind, moist static energy, and atmospheric stability differ greatly between strong and weak EAWM processes over the western Pacific. The strong EAWM causes the intensity of MJO to increase, and the eastward propagation of MJO to become more persistent. MJO activities over the equatorial western Pacific have different modes. Furthermore, these modes have differing relationships with the EAWM, and other factors can also affect the activities of MJO; consequently, the relationship between the MJO and EAWM shows both interannual and interdecadal variabilities.

  15. Excitation of equatorial Kelvin and Yanai waves by tropical cyclones in an ocean general circulation model

    Directory of Open Access Journals (Sweden)

    R. L. Sriver

    2012-09-01

    Full Text Available Tropical cyclones (TCs actively contribute to the dynamics of Earth's coupled climate system. They influence oceanic mixing rates, upper-ocean heat content, and air-sea fluxes, with implications for atmosphere and ocean dynamics on multiple spatial and temporal scales. Using an ocean general circulation model with modified surface wind forcing, we explore how TC winds can excite equatorial ocean waves in the tropical Pacific. We highlight a situation where three successive TCs in the western North Pacific region, corresponding to events in 2003, excite a combination of Kelvin and Yanai waves in the equatorial Pacific. The resultant thermocline adjustment significantly modifies the thermal structure of the upper equatorial Pacific and leads to eastward zonal heat transport. Observations of upper-ocean temperature by the Tropical Atmosphere Ocean (TAO buoy array and sea-level height anomalies using altimetry reveal wave passage during the same time period with similar properties to the modeled wave, although our idealized model methodology disallows precise identification of the TC forcing with the observed waves. Results indicate that direct oceanographic forcing by TCs may be important for understanding the spectrum of equatorial ocean waves, thus remotely influencing tropical mixing and surface energy budgets. Because equatorial Kelvin waves are closely linked to interannual variability in the tropical Pacific, these findings also suggest TC wind forcing may influence the timing and amplitude of El Niño events.

  16. Excitation of equatorial Kelvin and Yanai waves by tropical cyclones in an ocean general circulation model

    Directory of Open Access Journals (Sweden)

    R. L. Sriver

    2013-01-01

    Full Text Available Tropical cyclones (TCs actively contribute to the dynamics of Earth's coupled climate system. They influence oceanic mixing rates, upper-ocean heat content, and air–sea fluxes, with implications for atmosphere and ocean dynamics on multiple spatial and temporal scales. Using an ocean general circulation model with modified surface wind forcing, we explore how TC winds can excite equatorial ocean waves in the tropical Pacific. We highlight a situation where three successive TCs in the western North Pacific region, corresponding to events in 2003, excite a combination of Kelvin and Yanai waves in the equatorial Pacific. The resultant thermocline adjustment significantly modifies the thermal structure of the upper equatorial Pacific and leads to eastward zonal heat transport. Observations of upper-ocean temperature by the Tropical Atmosphere Ocean (TAO buoy array and sea-level height anomalies using altimetry reveal wave passage during the same time period with similar properties to the modeled wave, although our idealized model methodology disallows precise identification of the TC forcing with the observed waves. Results indicate that direct oceanographic forcing by TCs may be important for understanding the spectrum of equatorial ocean waves, thus remotely influencing tropical mixing and surface energy budgets. Because equatorial Kelvin waves are closely linked to interannual variability in the tropical Pacific, these findings also suggest TC wind forcing may influence the timing and amplitude of El Niño events.

  17. Understanding the Rise of African Business

    DEFF Research Database (Denmark)

    Jorem, Kaja Tvedten; Jeppesen, Søren; Hansen, Michael W.

    In light of recent enthusiasm over the African private sector, this paper reviews the existing empirical literature on successful African enterprises and proposes an analytical framework for understanding African firm success. Overall, it is argued that we need to develop an understanding...... of African firm strategy and performance that takes into account the specificities of the African business environment and African firm capabilities. The paper starts by juxtaposing the widespread pessimistic view of African business with more recent, optimistic studies on African firms’ performance....... The latter suggests that profound improvements in African business performance are indeed under way: with the private sector playing a more important role as an engine of growth, with the rise of a capable African entrepreneurial class, and with the emergence of dynamic and competitive African enterprises...

  18. The history of African trypanosomiasis

    Directory of Open Access Journals (Sweden)

    Steverding Dietmar

    2008-02-01

    Full Text Available Abstract The prehistory of African trypanosomiasis indicates that the disease may have been an important selective factor in the evolution of hominids. Ancient history and medieval history reveal that African trypanosomiasis affected the lives of people living in sub-Saharan African at all times. Modern history of African trypanosomiasis revolves around the identification of the causative agents and the mode of transmission of the infection, and the development of drugs for treatment and methods for control of the disease. From the recent history of sleeping sickness we can learn that the disease can be controlled but probably not be eradicated. Current history of human African trypanosomiasis has shown that the production of anti-sleeping sickness drugs is not always guaranteed, and therefore, new, better and cheaper drugs are urgently required.

  19. I like riding my bike. If it doesn't rain of course'. Accounts of embodied practices of rain in the face of climate change

    DEFF Research Database (Denmark)

    Lindegaard, Laura Bang

    that whereas cycling is treated as a morally superior practice, rain is treated as a phenomenon that mitigates the normative call to carry it out. The paper argues that this underlines the importance of acknowledging the normative affordances of embodied practices of weather in studies focusing on behavioural......The paper reports on an ethnomethodologically informed study of the discursive accomplishment of everyday transportation practices in the face of climate change. Drawing upon focus group data, the paper shows and discusses the implications of how embodied everyday practices of rain...... are conceptualised. Firstly, the paper focuses on how different practices are conceptualised as related to the embodied practice of rain. Whereas rain is treated as a potential element of the practice of walking in the forest, it is treated as an obstacle to cycling. Thus, even though it is the same rain...

  20. Characterization of tropical precipitation using drop size distribution and rain rate-radar reflectivity relation

    Science.gov (United States)

    Das, Saurabh; Maitra, Animesh

    2017-03-01

    Characterization of precipitation is important for proper interpretation of rain information from remotely sensed data. Rain attenuation and radar reflectivity (Z) depend directly on the drop size distribution (DSD). The relation between radar reflectivity/rain attenuation and rain rate (R) varies widely depending upon the origin, topography, and drop evolution mechanism and needs further understanding of the precipitation characteristics. The present work utilizes 2 years of concurrent measurements of DSD using a ground-based disdrometer at five diverse climatic conditions in Indian subcontinent and explores the possibility of rain classification based on microphysical characteristics of precipitation. It is observed that both gamma and lognormal distributions are performing almost similar for Indian region with a marginally better performance by one model than other depending upon the locations. It has also been found that shape-slope relationship of gamma distribution can be a good indicator of rain type. The Z-R relation, Z = ARb, is found to vary widely for different precipitation systems, with convective rain that has higher values of A than the stratiform rain for two locations, whereas the reverse is observed for the rest of the three locations. Further, the results indicate that the majority of rainfall (>50%) in Indian region is due to the convective rain although the occurrence time of convective rain is low (<10%).

  1. [Characteristics and the impact factors of acid rain in Fuzhou and Xiamen 1992-2012].

    Science.gov (United States)

    Zheng, Qiu-Ping; Wang, Hong; Chen, Bin-Bin; Sui, Ping; Lin, Wen

    2014-10-01

    Based on the observed acid rain data, synoptic situations and mass concentrations of atmospheric pollutants data from 1992 to 2012, the temporal variation characteristics and the impact factors of acid rain were analyzed in Fuzhou and Xiamen. The results showed that acid rain and non-acid rain accounted for 38.1% and 61.9% respectively in Fuzhou, 40.6% and 59.4% respectively in Xiamen. The annual average pH was 4.1-5.5 in Fuzhou. Acid rain pollution alleviated after 2007 in Fuzhou, and alleviated after 2006 in Xiamen. Acid rain was more serious in winter and spring than in summer and autumn. Precipitation intensity could affect the acidity of rain. Acid rain was observed more serious in southeast, southwest, west and northwest wind in Fuzhou, and more serious in northeast, southwest, west and northwest wind in Xiamen. Acid rain was most severe under the condition of transformed surface cold high, while most light under the conditions of typhoon (intertropical convergence zone) and outside of typhoon (intertropical convergence zone). There was a negative correlation between the mass concentrations of atmospheric pollutants, such as SO2, NO2, PM10, and the pH of rain in Fuzhou.

  2. Rainfall timing and runoff: The influence of the criterion for rain event separation

    Directory of Open Access Journals (Sweden)

    Molina-Sanchis Isabel

    2016-09-01

    Full Text Available Rain is not uniform in time and space in semiarid areas and its distribution is very important for the runoff process. Hydrological studies usually divide rainfall into events. However, defining rain events is complicated, and rain characteristics vary depending on how the events are delimited. Choosing a minimum inter-event time (MIT is a commonly used criterion. Our hypothesis is that there will be an optimal MIT that explains the maximum part of the variance of the runoff, with time to runoff used as a surrogate. The objective is to establish a procedure in order to decide upon this optimal MIT. We developed regressions between time to runoff (T0 and three descriptive variables of rain. Our results show that the optimum MIT is 1 hour, which seems to be the minimum period of time required for water in larger macropores to drain and sufficiently modify the effect of antecedent soil moisture on the runoff generation process. Rain events are classified into three significantly different groups: (1 large and intense rains, (2 light rains on wet soil, and (3 light rains on dry soil. Intense rains produce most of the runoff, but there were significant differences between small events in the runoff generated. Of rain events, 63.75% are single-tip events, and many could be dew.

  3. French participation in the International Equatorial Electrojet Year

    Directory of Open Access Journals (Sweden)

    Y. Cohen

    Full Text Available Without abstract

    Acknowledgements. The IEEY studies in the African sector were made possible by the participation of a large number of institutes. Funding was provided by the Ministère Français de la Coopération (Département de la Recherche et des Formations, and Département Télécommunications; ORSTOM (Département Terre Océan Atmosphère; CNET (France-Telecom Centre Lannion; the Ministère Français de la Recherche et de la Technologie; Centre National de la Recherche Scientifique (Département Sciences de l'Univers; the Centre à l'Energie Atomique; the Université Paris-Sud; Abidjan University, Ivory Coast; Dakar University, Senegal. We would like to express our deep gratitude to the many colleagues who have participated in the success of this experiment through their enormous personal commitment, to the Editorial Board of Annales Geophysicae and particularly to Sylviane Perret for producing this special issue.

  4. A radiative transfer algorithm for identification and retrieval of rain from Megha-Tropiques MADRAS

    Science.gov (United States)

    Varma, Atul K.; Piyush, D. N.; Gohil, B. S.; Basu, Sujit; Pal, P. K.

    2015-03-01

    The present study explains a radiative transfer based method for rain retrieval over the global land and oceans. The study explores the possibility of applying an existing algorithm for SSM/I to Megha-Tropiques (MT) MADRAS radiometer which is carried out by developing a radiative transfer based transfer function between scattering index (SI) from SSM/I and MADRAS measurements. Prior to quantitative estimation of rain from MADRAS, rain affected observations are identified. The scheme for rain identification over oceans presented herein from MADRAS, is used for rain flagging in the operational algorithms for the retrieval of other geophysical parameters, like cloud liquid water, total precipitable water and wind speed. SSM/I equivalent SI from MADRAS measurements is used for rain rate retrieval and testing is done with the actual measurements of brightness temperatures from SSM/I. The rain rates retrieved from MADRAS are compared with the other complimentary satellites. A comparison of daily average rain from MADRAS with that from the TRMM 3B42 is found to have a correlation of 0.67 and rms difference of 0.40 mm h-1 and nearly 0 mm h-1 bias. Similar monthly scale comparisons over the oceans provide correlation of 0.83 and 0.79 with bias of -0.03 and 0 mm h-1 with respect to TRMM-3B42 and SSM/I, respectively. Usability of the rain retrieval algorithm for intense rain associated with a deep depression is also demonstrated by comparing the spatial distribution of intense rain with other satellite measurements. Finally, the probability distribution of daily rain from MADRAS with TRMM-3B42 is presented. The approach presented herein can be generalized over other rain retrieval schemes and to any other pair of satellite missions even when they were operational during different periods of time. The study is particularly useful for Global Precipitation Mission (GPM) constellations for using a common precipitation retrieval algorithm.

  5. Atmospheric salt deposition in a tropical mountain rain forest at the eastern Andean slopes of South Ecuador – Pacific or Atlantic origin?

    Directory of Open Access Journals (Sweden)

    S. Makowski Giannoni

    2015-10-01

    its importance for herbivory, litter decomposition and thus, carbon cycling. Salt deposition should generally decline with distance from its marine sources. For tropical South America, a negative east-west salt availability gradient is assumed in the Amazon as a consequence of the barrier effect of the Andes for Pacific air masses. However, this generalized pattern may not hold for the tropical mountain rain forest in the Andes of southern Ecuador. To analyze salt availability, we investigate the deposition of Na+ and Cl- which are good proxies of sea spray aerosol. Because of the complexity of the terrain and related cloud and rain formation processes, salt deposition was analyzed from both, rain and occult precipitation (OP water along an altitudinal gradient over a period from 2004 to 2009. To assess the influence of Atlantic and Pacific air masses on the locally observed deposition of sodium and chloride, sea-salt aerosol concentration data from the Monitoring Atmospheric Composition and Climate (MACC reanalysis dataset and back-trajectory statistical methods were combined. Our results based on deposition time series and 2192 generated trajectories show a clear difference in the temporal variation of sodium and chloride concentration due to height and exposure to winds. The sea-salt transport was highly seasonal where higher locations revealed a stronger seasonality. Although the influence of the easterlies were predominant regarding atmospheric circulation, the statistical analysis of trajectories and hybrid receptor models revealed a stronger impact of the Pacific sea-salt sources on the deposition at the study area. The highest concentration in rain and cloud water was found between September and February originating from both, the equatorial Pacific and Atlantic. However, the Pacific sources contributed with up to 25 % to the observed total concentration of Na+ and Cl- at the receptor site although the frequency of occurrence of the respective trajectories

  6. The emergence of modern type rain forests and mangroves and their traces in the palaeobotanical record during the Late Cretaceous and early Tertiary

    Science.gov (United States)

    Mohr, Barbara; Coiffard, Clément

    2014-05-01

    The origin of modern rain forests is still very poorly known. This ecosystem could have potentially fully evolved only after the development of relatively high numbers of flowering plant families adapted to rain forest conditions. During the early phase of angiosperm evolution in the early Cretaceous the palaeo-equatorial region was located in a seasonally dry climatic belt, so that during this phase, flowering plants often show adaptations to drought, rather than to continuously wet climate conditions. Therefore it is not surprising that except for the Nymphaeales, the most basal members of extant angiosperm families have members that do not necessarily occur in the continuously wet tropics today. However, during the late Early Cretaceous several clades emerged that later would give rise to families that are typically found today mostly in (shady) moist places in warmer regions. This is especially seen among the monocotyledons, a group of the mesangiosperms, that developed in many cases large leaves often with very specific venation patterns that make these leaves very unique and well recognizable. Especially members of three groups are here of interest: the arum family (Araceae), the palms (Arecaceae) and the Ginger and allies (Zingiberales). The earliest fossil of Araceae are restricted to low latitudes during the lower Cretaceous. Arecaceae and Zingiberales do not appear in the fossil record before the early late Cretaceous and occur at mid latitudes. During the Late Cretaceous, Araceae are represented at mid latitudes by non-tropical early diverging members and at low latitudes by derived rainforest members. Palms became widespread during the Late Cretataceous and also Nypa, a typical element of tropical to subtropical mangrove environments evolved during this time period. During the Paleocene Arecaceae appear to be restricted to lower latitudes as well as Zingiberales. All three groups are again widespread during the Eocene, reaching higher latitudes and

  7. East African ROAD

    Science.gov (United States)

    Tekle, Kelali

    2016-10-01

    In the developing world astronomy had been treated as the science of elites. As a result of this overwhelming perception, astronomy compared with other applied sciences has got less attention and its role in development has been insignificant. However, the IAU General Assembly decision in 2009 opened new opportunity for countries and professionals to deeply look into Astronomy and its role in development. Then, the subsequent establishment of regional offices in the developing world is helping countries to integrate astronomy with other earth and space based sciences so as to progressively promote its scientific and development importance. Gradually nations have come to know that space is the frontier of tomorrow and the urgency of preeminence on space frontier starts at primary school and ascends to tertiary education. For this to happen, member nations in east African region have placed STEM education at the center of their education system. For instance, Ethiopian has changed University enrollment strategy to be in favor of science and engineering subjects, i.e. every year seventy percent of new University entrants join science and engineering fields while thirty percent social science and humanities. Such bold actions truly promote astronomy to be conceived as gateway to science and technology. To promote the concept of astronomy for development the East African regional office has actually aligned it activities to be in line with the focus areas identified by the IAU strategy (2010 to 2020).

  8. Bioenergy and African transformation.

    Science.gov (United States)

    Lynd, Lee R; Sow, Mariam; Chimphango, Annie Fa; Cortez, Luis Ab; Brito Cruz, Carlos H; Elmissiry, Mosad; Laser, Mark; Mayaki, Ibrahim A; Moraes, Marcia Afd; Nogueira, Luiz Ah; Wolfaardt, Gideon M; Woods, Jeremy; van Zyl, Willem H

    2015-01-01

    Among the world's continents, Africa has the highest incidence of food insecurity and poverty and the highest rates of population growth. Yet Africa also has the most arable land, the lowest crop yields, and by far the most plentiful land resources relative to energy demand. It is thus of interest to examine the potential of expanded modern bioenergy production in Africa. Here we consider bioenergy as an enabler for development, and provide an overview of modern bioenergy technologies with a comment on application in an Africa context. Experience with bioenergy in Africa offers evidence of social benefits and also some important lessons. In Brazil, social development, agricultural development and food security, and bioenergy development have been synergistic rather than antagonistic. Realizing similar success in African countries will require clear vision, good governance, and adaptation of technologies, knowledge, and business models to myriad local circumstances. Strategies for integrated production of food crops, livestock, and bioenergy are potentially attractive and offer an alternative to an agricultural model featuring specialized land use. If done thoughtfully, there is considerable evidence that food security and economic development in Africa can be addressed more effectively with modern bioenergy than without it. Modern bioenergy can be an agent of African transformation, with potential social benefits accruing to multiple sectors and extending well beyond energy supply per se. Potential negative impacts also cut across sectors. Thus, institutionally inclusive multi-sector legislative structures will be more effective at maximizing the social benefits of bioenergy compared to institutionally exclusive, single-sector structures.

  9. Organic Acids Over Equatorial Africa: Results from DECAFE 88

    Science.gov (United States)

    Helas, Günter; Bingemer, Heinz; Andreae, Meinrat O.

    1992-04-01

    Gaseous short chain organic acids were measured during the dry season (February) in and above the rain forest of the northern Congo. Samples were taken at ground level and during several flights up to 4 km altitude. The organic acids were concentrated from the atmosphere by using "mist scrubbers," which expose a mist of deionized water to the air to be probed. The organic acids absorbed in the water were subsequently analyzed by ion chromatography. Formic, acetic, and pyruvic acids were identified in the samples. At ground level, average mixing ratios of gaseous formic and acetic acid of 0.5±0.6 and 0.6±0.7 parts per billion by volume (ppbv) (1 s), respectively, were found. Boundary layer mixing ratios, however, were significantly higher (3.7±1.0 and 2.7±0.9 ppbv). This indicates a downward net flux of these atmospheric trace components from the boundary layer to the surface. Free tropospheric samples taken above the cloud convection layer show lower mixing ratios again (0.9±0.3 and 0.7±0.1 ppbv). On the basis of this vertical distribution, direct emission by vegetation is not considered to be the dominant source. Biomass burning and photochemical oxidation of biogenic precursors are the major processes contributing to the enhancement of organic acids observed in the boundary layer. The organic acids parallel the profiles of ozone and CO, which suggests that their generation processes are closely related. Pyruvic acid is not correlated with formic acid, indicating that the oxidation of isoprene is not of major importance. In emissions from biomass fires, CO correlates well with formic and acetic acid, and thus some of the enhancement of organic acids in the boundary layer can be explained due to burning. However, an additional gas phase source for organic acids must exist to explain the observed ratio of formic to acetic acid. This is most likely the ozonolysis of olefins which were released as pyrolysis products from biomass burning.

  10. Study of Rain-Induced Landslides Prediction in Malaysia

    Science.gov (United States)

    Koay, S. P.; Lateh, H.; Fukuoka, H.; Sakai, N.; Murakami, S.; Koyama, T.; Jamaludin, S. B.

    2014-12-01

    In Malaysia, rain-induced landslides are occurring more often recently. Millions of Malaysian Ringgit are allocated for risky slope monitoring and slope failure measurement in the government budget every year. However, there are thousands of slopes which are classified as dangerous slopes, and implementing site monitoring system in all slopes, with physical devices, to monitor the movement of the soil in the slopes are too costly and almost impossible. In our study, we propose 2 methods to predict the slope failure, which are (1)Accumulated Rainfall vs. Rainfall Intensity and (2)Working Rainfall vs. Rainfall Intensity, with water table drawdown period consideration. The curve of jointed data will be reset to 0 if the rain stop period is longer than the period of water table drawdown to pre-rain level. The critical line, in these 2 methods, which determines if the slope is in a risk state, should be generated by collecting historical landslides data. However, unlike the other developed countries, a complete historical landslides data in Malaysia is difficult to be obtained. We propose that the critical line is drawn by referring to the simulation result of the factor of slope stability F, with the slope parameters and rainfall data, to cover the uncompleted historical landslides data. If the curves cross over the critical line, the probability of slope failure is considered high. In this study, the proposed methods managed to show that 2 occurrences of landslides, in Malaysia, could be predicted if it was applied earlier. In future, further study on fine tuning of these two methods and selecting the more accuracy method from these two methods may assist the government authorities to judge the movement of the slopes before disseminating data and information for early warning system.

  11. Experimental analysis of microscale rain cells and their dynamic evolution

    Science.gov (United States)

    Enjamio, C.; Vilar, E.; RedañO, A.; FontáN, F. P.; Ndzi, D.

    2005-06-01

    This paper presents a detailed space-time analysis of rainfall rate using two dense networks of rain gauges covering two microscale areas of some 100 km2 each and located in two distinct climatic areas in the United Kingdom and Spain. The study has been carried out with the main objective of addressing dynamic fade mitigation techniques and scatter interference problems in terrestrial and satellite communication systems. The two databases, using a total of 49 and 23 rain gauges, respectively, are described, and the continuous interpolated field used for the subsequent analyses is explained in detail. The suitability of the networks in terms of density, correlation distance, and fractal dimension are briefly addressed. A to-scale comparison grid of the networks is also given. It has been found that when the maximum intensity reached during a rain event surpasses a certain threshold, different for each of the two areas, rainfall rates exhibit a spatial structure in the form of closed contours of thresholds referred to as cells. In statistical terms, the most probable diameter found is about 3.5 km, and distributions are presented. They are similar for the two sites but not so for the maxima reached inside the cells. Using cross-correlation techniques, displacement and velocities are analyzed in detail. Cells "zigzag" around a dominant trend because of the global cloud movements (driven by winds at heights of about 700 hPa). Local topography strongly affects local behavior. Analytical approximations to the experimental statistical distributions and selected histograms of the results are presented.

  12. Rainfall estimation using moving cars as rain gauges - laboratory experiments

    Science.gov (United States)

    Rabiei, E.; Haberlandt, U.; Sester, M.; Fitzner, D.

    2013-11-01

    The spatial assessment of short time-step precipitation is a challenging task. Low density of observation networks, as well as the bias in radar rainfall estimation motivated the new idea of exploiting cars as moving rain gauges with windshield wipers or optical sensors as measurement devices. In a preliminary study, this idea has been tested with computer experiments (Haberlandt and Sester, 2010). The results have shown that a high number of possibly inaccurate measurement devices (moving cars) provide more reliable areal rainfall estimations than a lower number of precise measurement devices (stationary gauges). Instead of assuming a relationship between wiper frequency (W) and rainfall intensity (R) with an arbitrary error, the main objective of this study is to derive valid W-R relationships between sensor readings and rainfall intensity by laboratory experiments. Sensor readings involve the wiper speed, as well as optical sensors which can be placed on cars and are usually made for automating wiper activities. A rain simulator with the capability of producing a wide range of rainfall intensities is designed and constructed. The wiper speed and two optical sensors are used in the laboratory to measure rainfall intensities, and compare it with tipping bucket readings as reference. Furthermore, the effect of the car speed on the estimation of rainfall using a car speed simulator device is investigated. The results show that the sensor readings, which are observed from manual wiper speed adjustment according to the front visibility, can be considered as a strong indicator for rainfall intensity, while the automatic wiper adjustment show weaker performance. Also the sensor readings from optical sensors showed promising results toward measuring rainfall rate. It is observed that the car speed has a significant effect on the rainfall measurement. This effect is highly dependent on the rain type as well as the windshield angle.

  13. Hydrogen peroxide deposition and decomposition in rain and dew waters

    Science.gov (United States)

    Ortiz, Vicky; Angélica Rubio, M.; Lissi, Eduardo A.

    Peroxides and hydrogen peroxide were determined by a fluorometric method in dew and rain collected in the atmosphere of Santiago of Chile city. The measured peroxides comprise hydrogen peroxide (the main component) and peroxides not decomposed by catalase. The collected natural peroxides readily decompose in the natural matrix, rendering difficult an estimation of the values present in real-time. In order to establish the kinetics of the process and the factors that condition their decomposition, the kinetics of the decay at several pHs and/or the presence of metal chelators were followed. The kinetics of hydrogen peroxide decomposition in the water matrix was evaluated employing the natural peroxides or hydrogen peroxide externally added. First-order kinetics was followed, with half decay times ranging from 80 to 2300 min. The addition of Fe(II) in the micromolar range increases the decomposition rate, while lowering the pH (<3) notably reduces the rate of the process. The contribution of metals to the decomposition of the peroxides in the natural waters was confirmed by the reduction in decomposition rate elicited by its treatment with Chelex-100. Dew and rain waters were collected in pre-acidified collectors, rendering values considerably higher than those measured in non-treated collectors. This indicates that acidification can be proposed as an easy procedure to stabilize the samples, reducing its decomposition during collection time and the time elapsed between collection and analysis. The weighted average concentration for total peroxides measured in pre-treated collectors was 5.4 μM in rains and 2.2 μM in dews.

  14. 2002 Sino-African SHP Training Workshop

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The 2002 Sino-African SHP Training Workshop was held from 10 May to 18 June 2002 at Hangzhou Regional Center for Small Hydro Power(HRC). Attended altogether 9 participants from 5 African countries, i.e. Burundi, Nigeria, South African, Tanzania and Tunisia. This is the second training workshop on SHP that HRC conducted for African countries.

  15. Airborne fungi isolated from rain water collected in Mexico City

    OpenAIRE

    1986-01-01

    A rcsearch was carried out on the lungi present in tlir atmosphere of Mexico City, through the analysis of rain watcr collected from June to Septcmber of 1982. To obtain data ori a wide range oí fungi, isolations were made on Sabouraud dextrosc agar and potatc) dcxtrosc agar plates incubated at the rnom tcmperaturc of 20-26QC for 48- 72 hours. During tlic sampling period 600 to GOOO colonies per m1 were rccorded. The most frequent fungi were Cladosporium, Alternaria, Penicillium and yeasts. T...

  16. Analysis on Feminism in Cat in the Rain

    Institute of Scientific and Technical Information of China (English)

    周东妮

    2013-01-01

    Ernest Hemingway is always regarded as masculinity by the critics. His early stories won wide critical praise for their stoic, understanding“masculine”study and their graphic depiction of male pursuits and attitudes. However, in addition to his male depiction in his novels, Hemingway, in fact, is also a writer who cares and shows sympathy and concern towards women. Then Cat in the Rain is one of his typical work which focuses on the aspirations of women. With analysis on the characters, plot and description of settings etc. in the story, Hemingway’s real attitude toward female is explicated.

  17. Wood Properties of Poplar from Stand Affected by Acid Rain

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Wood properties from 28 trees (Populus euramericana) selected from healthy and acid rain damaged forest were measured to evaluate the possible impacts on wood quality and utilization. On the heavily damaged location, the pH value of precipitation ranged from 3.7-5.0, and sulfate loading ranged from 20-40 kg·ha-2.y-1. Quantitative and qualitative studies on ring width, physical properties and mechanical properties indicated that changes of wood properties between diseased and healthy poplar occurred. Aci...

  18. A Probabilistic Rain Diagnostic Model Based on Cyclone Statistical Analysis

    OpenAIRE

    Iordanidou, V.; A. G. Koutroulis; I. K. Tsanis

    2014-01-01

    Data from a dense network of 69 daily precipitation gauges over the island of Crete and cyclone climatological analysis over middle-eastern Mediterranean are combined in a statistical approach to develop a rain diagnostic model. Regarding the dataset, 0.5 × 0.5, 33-year (1979–2011) European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA-Interim) is used. The cyclone tracks and their characteristics are identified with the aid of Melbourne University algorithm (MS scheme). T...

  19. Concept development for the ITER equatorial port visible∕infrared wide angle viewing system.

    Science.gov (United States)

    Reichle, R; Beaumont, B; Boilson, D; Bouhamou, R; Direz, M-F; Encheva, A; Henderson, M; Huxford, R; Kazarian, F; Lamalle, Ph; Lisgo, S; Mitteau, R; Patel, K M; Pitcher, C S; Pitts, R A; Prakash, A; Raffray, R; Schunke, B; Snipes, J; Diaz, A Suarez; Udintsev, V S; Walker, C; Walsh, M

    2012-10-01

    The ITER equatorial port visible∕infrared wide angle viewing system concept is developed from the measurement requirements. The proposed solution situates 4 viewing systems in the equatorial ports 3, 9, 12, and 17 with 4 views each (looking at the upper target, the inner divertor, and tangentially left and right). This gives sufficient coverage. The spatial resolution of the divertor system is 2 times higher than the other views. For compensation of vacuum-vessel movements, an optical hinge concept is proposed. Compactness and low neutron streaming is achieved by orienting port plug doglegs horizontally. Calibration methods, risks, and R&D topics are outlined.

  20. Concept development for the ITER equatorial port visible/infrared wide angle viewing system

    Energy Technology Data Exchange (ETDEWEB)

    Reichle, R.; Beaumont, B.; Boilson, D.; Bouhamou, R.; Direz, M.-F.; Encheva, A.; Henderson, M.; Kazarian, F.; Lamalle, Ph.; Lisgo, S.; Mitteau, R.; Patel, K. M.; Pitcher, C. S.; Pitts, R. A.; Prakash, A.; Raffray, R.; Schunke, B.; Snipes, J.; Diaz, A. Suarez; Udintsev, V. S. [ITER Organization, Route de Vinon-sur-Verdon, 13115 St Paul-lez-Durance (France); and others

    2012-10-15

    The ITER equatorial port visible/infrared wide angle viewing system concept is developed from the measurement requirements. The proposed solution situates 4 viewing systems in the equatorial ports 3, 9, 12, and 17 with 4 views each (looking at the upper target, the inner divertor, and tangentially left and right). This gives sufficient coverage. The spatial resolution of the divertor system is 2 times higher than the other views. For compensation of vacuum-vessel movements, an optical hinge concept is proposed. Compactness and low neutron streaming is achieved by orienting port plug doglegs horizontally. Calibration methods, risks, and R and D topics are outlined.