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The Spatial and Temporal Characteristics of Rainfall over the Lake Victoria Basin of Kenya in 1987-2016 认领
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作者 Wabwire Odhiambo Evans S. N. Mukhovi I. A. Nyandega 《大气和气候科学(英文)》 2020年第2期240-257,共18页
Climate extremes have increased in the recent past and they are further being exacerbated by climate change and variability. In this paper, we sought to determine rainfall characteristics over the Lake Victoria Basin ... Climate extremes have increased in the recent past and they are further being exacerbated by climate change and variability. In this paper, we sought to determine rainfall characteristics over the Lake Victoria Basin of Kenya in 1987-2016, as a basis of understanding climate variability. The methodology used included;Standardized Precipitation Index to depict variability, coefficient of variation for spatial analysis and the Mann-Kendall test to test the presence of trends in data. We established that Lake Victoria basin is relatively wet through-out the year, with two distinct rainfall seasons March-April-May (MAM) and October-November-December (OND) that support human livelihood and ecology. The normal wetness conditions have declined over time, paving way for both dry and wet extremes conditions between 1997-1998 and 2002-2006, respectively. The rainfall extremes have become frequent in the last decade in 2007-2016. We also established a decline in the MAM rainfall seasons, and an increase during the October-December rainfall seasons in 1987-2016. Furthermore, the number of rainy days has declined with the onset and cessations of both long rains and short rains having shown a variability of at least 50% and 30% respectively, in a range of about 100 to 200 Julian days. The decline in wet condition is likely to affect economic activities especially the rainfed agriculture. The changing rainfall trends over the basin therefore, call for proper human livelihood planning and ecological monitoring in order to achieve ecological sustainability. 展开更多
关键词 Climate VARIABILITY SEASONAL RAINFALL Intra-Seasonal RAINFALL Characteritics and Lake VICTORIA BASIN
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Study of the Indicators of Climate Change in Mysore District, Karnataka, India 认领
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作者 Alaa Samy Hafez Megahed S. Srikantaswamy 《大气和气候科学(英文)》 2020年第2期159-167,共9页
The study aims to find out the changes of climate change parameters for Mysore district. To analyse the variations in climatic parameters like Rainfall and Temperature, data were used for a period of 1986-2016, and Hu... The study aims to find out the changes of climate change parameters for Mysore district. To analyse the variations in climatic parameters like Rainfall and Temperature, data were used for a period of 1986-2016, and Humidity data were used for a period of 2000-2016 to study the nature of climate change in the region. The findings of the study show that the climate variability and climate change for Mysore district, the monthly Rainfall is increased and monsoon Rainfall shows a decrease in trend. And the monthly, summer, monsoon minimum Temperature shows that decrease. Generally, the monthly maximum Temperature has decreased, but in case of summer and monsoon seasons increased respectively, and the monthly Relative Humidity has increased (positive). There is a decrease in Relative Humidity from January to April, and increase in the Relative Humidity during Monsoon season for Mysore District. The Annual average of Relative Humidity shows that it is increased for Mysore District. 展开更多
关键词 Climate Change RAINFALL Temperature Mysore DISTRICT
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Dust Source, Vertical Profile and Climate Impact by RegCM3 Regional Climate Model over West Africa during 2006 认领
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作者 Dialo Diop Demba Ndao Niang +1 位作者 Mamadou Simina Drame Abdoulaye Ba 《大气和气候科学(英文)》 2020年第2期206-219,共14页
This study aims to evaluate dust impact on climate parameters over the Sahel region by RegCM3 regional model during 2006. Indeed, aerosols are one of the main uncertainties in climate models. The aerosol optical depth... This study aims to evaluate dust impact on climate parameters over the Sahel region by RegCM3 regional model during 2006. Indeed, aerosols are one of the main uncertainties in climate models. The aerosol optical depth (AOD) derived from RegCM3 model has been validated with various observed datasets. The aerosol sources are identified over North Algeria and East of Sahel (Bodele depression). Discrepancies are noted when considering dust temporal and spatial distribution. Dust season extends between March and October, with two peaks of AOD recorded in March (spring) and June (summer). The dust vertical distribution showed that the mineral aerosol layer is located between 850 hPa and 300 hPa (1.5 km to 7 km). The RegCM3 model simulates fairly well the transport in the upper layers, especially in the Saharan Air Layer (SAL) during the summer. However, RegCM3 simulates poorly the transport and sedimentation of particles in the lower layers (below 2 km). The investigation of dust radiative impact shows a general cooling. The maximum of radiative forcing is located around 18&deg;N - 20&deg;N, with values of about -80 W/m2 in June - August (JJA) and -40 W/m2 at the surface during March - May (MAM). This study also showed the indirect effect of dust with a decrease in precipitation about -0.7 mm/day around 15 - 20&deg;N during the rainy season. 展开更多
关键词 Dust REGCM3 SAHEL Lidar AERONET Temperature RAINFALL WEST AFRICA
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Analysis of Precipitation and Temperature Variability over Central Africa (1901-2015) 认领
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作者 Yaw A. Twumasi Edmund C. Merem +7 位作者 John B. Namwamba Tomas Ayala-Silva Kamran Abdollahi Ronald Okwemba Onyumbe E. Ben Lukongo Caroline O. Akinrinwoye Joshua Tate Kellyn La Cour-Conant 《大气和气候科学(英文)》 2020年第2期220-239,共20页
Africa is already experiencing the impact of climate change. Some of the manifestations of climate change in Africa are, changing weather patterns resulting in, flooding and drought. Temperature change has impacted he... Africa is already experiencing the impact of climate change. Some of the manifestations of climate change in Africa are, changing weather patterns resulting in, flooding and drought. Temperature change has impacted health, livelihoods, productivity of food, availability of water, and state of security. This study examines the long-term climate variations in Central African Countries (Gabon, Cameroon, Republic of Congo, Central Africa Republic, Chad and Democratic Republic of Congo) for the period 1901 to 2015, and then investigates the possible influence of increases in greenhouse gas concentrations. To investigate climate patterns and trends in the Central African Countries, precipitation and temperature were analyzed on annual time scales using data collected from the World Bank Group Climate Change Knowledge Portal. Data was further aggregated using annual average blocks of 10 years. Linear and polynomial regression was performed. Also, linear time series slopes were analyzed to investigate the spatial and temporal trends of climate variability in Central African countries. Results of the analyses indicated that the mean annual temperature and precipitation records in some of the Central African Countries had both warming and cooling trends over the study period from 1901 to 2015. For example, differences between the maximum and the minimum rainfall data for Democratic Republic of Congo, Cameroon and Gabon were 13 mm, 13 mm and 11.1 mm, which corresponded to 11.04%, 10.03% and 10.44% respectively. The study also found the temperature of Chad to have significantly risen from 1901 to 2015 by almost 20%, while its rainfall’s variation was limited. Although the variation in rainfall in Chad was not dramatic, the temperature per 10 year rose by almost 20%. Chad’s temperature rose according to a cubic model from about 24.5°C to just below 27°C during the period 1901-1940. This was followed by a brief drop between 1940 and 1960. From 1960 to 2015 it rose according to the model to almost 28°C. By 2040 the tempe 展开更多
关键词 Temperature RAINFALL Climate VARIABILITY Linear and POLYNOMIAL Regression Central AFRICAN COUNTRIES
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Climatic Characteristics of Dust Storms in Jordan 认领
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作者 Ali Ahmad Ghanem 《美国气候变化期刊(英文)》 2020年第2期136-146,共11页
This study is devoted to examine the climate characteristics of the Dust Storms (DS) with visibility 0 - 1 km that occurred in Jordan for the period 1988 to 2018. It is found that the DS varies temporally and spatiall... This study is devoted to examine the climate characteristics of the Dust Storms (DS) with visibility 0 - 1 km that occurred in Jordan for the period 1988 to 2018. It is found that the DS varies temporally and spatially, as the largest number of DS occurred in 2003 (36 DS) and the lowest occurred in 1999 (one DS). The average was 17.22 DS with the coefficient of variation of 45%, the DS durations ranged from 1 - 4 days, most of them occurred in spring (54.1%) especially in April (22.2%). The DS increased southward and eastward directions, they increased from 13 DS in Irbid in the north to 182 DS in Al-Jafr in the south and to 102 DS in Safawi in the east. The results showed positive relationships between wind speeds. There were negative relationships with relative humidity, pressure and rainfall, and there was no relationship between DS and the maximum temperature. 展开更多
关键词 Dust Storms TEMPORAL RAINFALL Winds JORDAN
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Analysis of Daily Rainfall in São Carlos/SP, Brazil over 1979-2017 Using Laplace Trend Test 认领
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作者 Rafael Grecco Sanches Bruno César Dos Santos +3 位作者 Rodrigo Sanches Miani Gustavo Zen de Figueiredo Neves Mauricio Sanches Duarte Silva Adriano Rogério Bruno Tech 《地球科学和环境保护期刊(英文)》 2020年第7期104-125,共22页
Rainfall expresses one of the most complex climate factors in Southeastern Brazil. Understanding the dynamics and temporal trends of rainfall represents a significant challenge due to regional and even global mechanis... Rainfall expresses one of the most complex climate factors in Southeastern Brazil. Understanding the dynamics and temporal trends of rainfall represents a significant challenge due to regional and even global mechanisms, such as FS (Frontal Systems) and the SACZ (South Atlantic Convergence Zone), and the interaction with the Atlantic and Pacific Oceans. The present study aimed at analyzing the pluviometric tendencies in S<span style="color:#4F4F4F;font-family:"font-size:14px;white-space:normal;background-color:#F7F7F7;">&#227</span>o Carlos/SP, in the countryside of S<span style="color:#4F4F4F;font-family:"font-size:14px;white-space:normal;background-color:#F7F7F7;">&#227</span>o Paulo State. Laplace trend test was used to comprehend the temporal evolution of daily rainfall in the region in the historical series 1979-2017, in seven pluviometric stations (climatological or surface stations). Significant fluctuations in interannual trends and between seasons were observed. However, it was noted that the beginning of the 1980s showed positive trends, whereas, as of the year 2000, most of the stations demonstrated negative trends, indicating a reduction in daily rainfall volume due to the great tropical climatic variability of Brazil. Emphasis should also be given to the regional and local effects, such as elevation and urbanization, respectively, which corroborate such differences among the analyzed stations. This methodology is of considerable value for the observation of pluviometric trends, and future studies can validate such a tool in climatological studies. 展开更多
关键词 Tropical Climatology Climate Variability Rainfall Trends Statistical Tool Laplace Trend Test
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Response of Seasonal Vegetation Dynamics to Climatic Constraints in Northeastern Burundi 认领
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作者 Pacifique Batungwanayo Marnik Vanclooster Alan F. Koropitan 《地球科学和环境保护期刊(英文)》 2020年第9期151-181,共31页
The climate crises in East Africa (EA), particularly in Burundi, have affected vegetation which, in turn, plays a key role in the climate system by modifying the terrestrial water and energy balance. Consequently, it ... The climate crises in East Africa (EA), particularly in Burundi, have affected vegetation which, in turn, plays a key role in the climate system by modifying the terrestrial water and energy balance. Consequently, it is vital to understand vegetation dynamics and its response to current and projected climate conditions to support the design of climate resilient land management strategies. The objective of this study was to study the dynamics of vegetation cover over the Northeastern Burundi (NEB) in response to climatic constraints. The methodology used consisted of the interpretation of satellite images along with the analysis of data collected through rain-gauge stations. The data sets used include time series composite moderate resolution imaging spectroradiometer (MODIS) normalized difference vegetation index (NDVI) data collected between February 2000 and December 2017;long term (1986-2017) rainfall data acquired from two meteorological stations throughout the Northeastern provinces in Burundi and precipitation and mean temperature data (1986-2017) from Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS) and ERA5 Daily aggregates for the study area. The study provides an assessment of the vegetation trends in NEB using the NDVI time series. In addition, regression analysis is applied to assess the relations between NDVI and precipitation, air temperature, potential evapotranspiration, as well as with growing season characteristics (onset, cessation, and length). Results show that the rate in vegetation productivity is persistently gradual between 2000 and 2011 despite fluctuations from the mean position, followed by a lower growth rate over the period 2011-2017. There has been trend variation in precipitation, neither the temperature was constant. The temperature over the region has increased while the precipitation has decreased. The onset of the growing season and air temperature also show a significant influence on seasonal vegetation dynamics in the region. Drought-induced plant stres 展开更多
关键词 Rainfall Variability ONSET Dry Spell NDVI Remote Sensing Northeastern Burundi
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Rainfall Variability under Present and Future Climate Scenarios Using the Rossby Center Bias-Corrected Regional Climate Model 认领
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作者 Jane Wangui Mugo Franklin J. Opijah +2 位作者 Joshua Ngaina Faith Karanja Mary Mburu 《美国气候变化期刊(英文)》 2020年第3期243-265,共23页
<p align="justify"> <span style="font-family:Verdana;">This study sought to determine the spatial and temporal variability of rainfall under past and future climate scenarios. The data ... <p align="justify"> <span style="font-family:Verdana;">This study sought to determine the spatial and temporal variability of rainfall under past and future climate scenarios. The data used comprised station-based monthly gridded rainfall data sourced from the Climate Research </span><span style="font-family:Verdana;">Unit (CRU) and monthly model outputs from the Fourth Edition of the Rossby Centre (RCA4) Regional Climate Model (RCM), which has scaled-down </span><span style="font-family:Verdana;">nine GCMs for Africa. Although the 9 Global Climate Models (GCMs) downscaled by the RCA4 model was not very good at simulating rainfall in Kenya, the ensemble of the 9 models performed better and could be used for further studies. The ensemble of the models was thus bias-corrected using the scaling method to reduce the error;lower values of bias and Normalized Root Mean Square Error (NRMSE) w</span></span><span style="font-family:Verdana;">ere</span><span style="font-family:'Minion Pro Capt','serif';"><span style="font-family:Verdana;"> recorded when compared to the uncorrected models. The bias-corrected ensemble was used to study the spatial and temporal behaviour of rainfall under baseline (1971 to 2000) and future RCP 4.5 and 8.5 scenarios (2021 to 2050). An insignificant trend was noted under the </span><span style="font-family:Verdana;">baseline condition during the March-May (MAM) and October-December</span> <span style="font-family:Verdana;">(OND) rainfall seasons. A positive significant trend at 5% level was noted</span><span style="font-family:Verdana;"> under RCP 4.5 and 8.5 scenarios in some stations during both MAM and OND seasons. The increase in rainfall was attributed to global warming due to increased anthropogenic emissions of greenhouse gases. Results on the spatial variability of rainfall indicate the spatial extent of rainfall will increase under both RCP 4.5 and RCP 8.5 scenario when compared to the baseline;the increase is higher under the RCP 8.5 scenario. Overall rainfall was found to be highly v 展开更多
关键词 CORDEX Climate Change Bias Correction ENSEMBLE RAINFALL Kenya RCA4
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WRF Simulations of Extreme Rainfall over Uganda’s Lake Victoria Basin: Sensitivity to Parameterization, Model Resolution and Domain Size 认领
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作者 Ronald Opio Geoffrey Sabiiti +2 位作者 Alex Nimusiima Isaac Mugume Julianne Sansa-Otim 《地球科学和环境保护期刊(英文)》 2020年第4期18-31,共14页
Rainfall extremes have strong connotations to socio-economic activities and human well-being in Uganda’s Lake Victoria Basin (LVB). Reliable prediction and dissemination of extreme rainfall events are therefore of pa... Rainfall extremes have strong connotations to socio-economic activities and human well-being in Uganda’s Lake Victoria Basin (LVB). Reliable prediction and dissemination of extreme rainfall events are therefore of paramount importance to the region’s development agenda. The main objective of this study was to contribute to the prediction of rainfall extremes over this region using a numerical modelling approach. The Weather Research and Forecasting (WRF) model was used to simulate a 20-day period of extremely heavy rainfall that was observed in the March to May season of 2008. The underlying interest was to investigate the performance of different combinations of cumulus and microphysical parameterization along with the model grid resolution and domain size. The model output was validated against rainfall observations from the Tropical Rainfall Measuring Mission (TRMM) using 5 metrics;the rainfall distribution, root mean square error, mean error, probability of detection and false alarm ratio. The results showed that the model was able to simulate extreme rainfall and the most satisfactory skill was obtained with a model setup using the Grell 3D cumulus scheme combined with the SBU_YLin microphysical scheme. This study concludes that the WRF model can be used for simulating extreme rainfall over western LVB. In the other 2 regions, central and eastern LVB, its performance is limited by failure to simulate nocturnal rainfall. Furthermore, increasing the model grid resolution showed good potential for improving the model simulation especially when a large domain is used. 展开更多
关键词 EXTREME RAINFALL WRF PARAMETERIZATION Model RESOLUTION DOMAIN Size
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Rare Earth Elements in the Water Column of Sungai Balok, Pahang, Malaysia as Monsoon Event Proxies 认领
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作者 Zolhizir Daud Che Abd Rahim Mohamed 《环境保护(英文)》 2020年第5期421-440,共20页
Sampling of surface water at seven stations along the Sungai Balok, Pahang was conducted from 2013 to 2015 to investigate the distribution of dissolved rare earth elements (REE) in river systems. The whole concentrati... Sampling of surface water at seven stations along the Sungai Balok, Pahang was conducted from 2013 to 2015 to investigate the distribution of dissolved rare earth elements (REE) in river systems. The whole concentration of ΣREE in the dissolved phase recorded during this study ranged from 368 to 9121 pmol?L?1 with a mean of 2328 ± 1442 pmol?L?1 that was dominantly influenced by the concentration of Ce ranging from 84 to 3237 pmol?L?1. Similarly, the large ranged value of La/YbN (0.69 - 11.57) might be due to the fluctuating rainfall events during samplings as well as input from lithogenic sources that suggests the influence of monsoon events. The highly significant statistical correlation of Al and Fe (R2 = 0.65;p < 0.01) also suggests the resuspension and mixing of REEs in the water column. However, the lower ratio of Y/Ho < 55 might be due to the large volume of freshwater input especially during the Northeast monsoon (November to March). Therefore, the highest inventories of Ce were during 15th January 2014 and 1st November 2014 with 586.5 pmol?cm?2 and 643.4 pmol?cm?2, accordingly. Subsequently, results showed an increasing flux of Ce occurring in the dissolved phase from November 2013 to January 2014 and November 2014 to January 2015, with 39.14 nmol?cm?2?yr?1 and 59.78 nmol?cm?2?yr?1, respectively. 展开更多
关键词 RAINFALL Sediment Water COLUMN MONSOON Dissolved Phase
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Monitoring and Assessment of Oyster and Barnacle Larvae Settlement in an Oyster Farm in Western Taiwan 认领
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作者 Yih-Tsong Ueng Yi-Kuang Wang +3 位作者 Chun-Wen Tsao Yin Chang Shu-Chu Tung Jung-Ting Hsu 《自然资源(英文)》 2020年第3期112-126,共15页
The Portuguese oyster (Crassostrea angulata) is an important fishery resource in Taiwan. This study investigated oyster cultures at two locations along the coast of Taisi Township from March 2012 to July 2014. The ave... The Portuguese oyster (Crassostrea angulata) is an important fishery resource in Taiwan. This study investigated oyster cultures at two locations along the coast of Taisi Township from March 2012 to July 2014. The average recruitment density, measured once every two weeks, of the oyster larvae was 256.4 ± 236.6 individuals/shell (N = 62) at site A and 118.5 ± 140.2 individuals/shell (N = 39) at site B. The average adherence density of the barnacle larvae was 187.1 ± 251.2 individuals/shell (N = 60) at site A and 60.9 ± 112.5 individuals/shell (N = 37) at site B. In Taiwan, C. angulata?spawned all year. The primary spawning season was from March to September. The primary of adherence spawning season of barnacles was from March to October. Rainfall was the major factor that influenced oyster C. angulata?and barnacle settlement, the eigenvalue of PC1 was 1.83 and could explain 61.0%. There are two main culturing seasons that move oyster larvae from coast of Taisi to farms in other places: from March to May and from August to September. Although the oyster larvae are more abundant in spring, fishermen prefer harvesting the larvae in autumn to avoid the typhoon season (July-September). 展开更多
关键词 Correlation Influence Rainfall RECRUITMENT SPAT
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Soil Detachment with Organic Mulching Using Rainfall Simulator in Comparison with a Short Duration Natural Rainfall for Effective Soil Conservation 认领
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作者 Johnson Kayode Adewumi John Jiya Musa +3 位作者 Olayemi Johnson Adeosun Otuaro Ebierin Akpoebidimiyen Adebola Adekunle Babafemi Sunday Adewumi 《环境保护(英文)》 2020年第6期457-469,共13页
The impact of raindrop on sandy soil was studied using rainfall simulator and natural rainfall to determine average soil detached. Erosion by rainfall is one of the major hazards threatening the productivity of farmla... The impact of raindrop on sandy soil was studied using rainfall simulator and natural rainfall to determine average soil detached. Erosion by rainfall is one of the major hazards threatening the productivity of farmlands. This study determined the rate of soil detachment in comparison between natural rainfall and simulated rainfall for effective soil conservation measure. The height of the simulator was varied considering the diameter of the nozzles which were considered during the design stage of the rain simulator. Two plots of dimensions 2 m × 2 m each were cleared with one considered for bare and treated soils for both the natural rainfall and simulated rainfall. Splash cups were installed on each of the plots at half depth of the cup after the clearing of the area at 0.4 m × 0.4 m apart. Two sets of rain gauge were placed at the experimental site to note the volume of natural rainfall on the farm. The average soil detached was analysed using statistical analysis where t-test was also carried out to know the difference in mean. There was a significant difference in the degree of soil detachment between bare and treated soil under natural rainfall experiment;t(18) = 8.917, p < 0.01. The mean of the natural rainfall for the bare soil was 11.6910 compared to that of the treated soil of 7.75. Size of effect (Eta-square (<i><span style="white-space:nowrap;">&eta;</i></span><sup>2</sup>) = 0.8154) reveals that the nature of soil accounted for 81.5% variance in the average detachment rate. For simulated experiments with a mean value of 7.3360 have higher tendency of detachment than treated soil with a mean value of 4.2240. Size of effect (Eta-square (<span style="white-space:nowrap;"><span style="white-space:normal;"><i></span>&eta;</i><span style="white-space:normal;"></span></span><sup>2</sup>) = 0.630) reveals that the soil types accounted for 63% variance in the average detachment. It was concluded that 40.33% soil was found to be conserved using the cow dungs mixed with bare soil to compact the soil. The nozz 展开更多
关键词 BARE RAINFALL SIMULATOR SOIL TREATED
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Study on the Effects of Extreme Precipitation for Seven Growth Stages of Winter Wheat in Northern Weihe Loess Plateau, China 认领
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作者 Ouk Sereyrorth Baowen Yan +2 位作者 Khem Chunpanha Porn Lybun Pich Linvolak 《水资源与保护(英文)》 2020年第4期358-380,共23页
The research on the characteristic frequency of precipitation is a great significance for guiding regional agricultural planning, water conservancy project designs, and drought and flood control. Droughts and floods o... The research on the characteristic frequency of precipitation is a great significance for guiding regional agricultural planning, water conservancy project designs, and drought and flood control. Droughts and floods occurred in northern Weihe Loess Plateau, affecting growing and yield of winter wheat in the area. Based on the daily precipitation data of 29 meteorological stations from 1981 to 2012, this study is to address the analysis of three different frequencies of annual precipitation at 5%, 50%, and 95%, and to determine the amount of rainfall excess and water shortage during seven growth stages of winter wheat at 5%, 10%, and 20% frequencies, respectively. Pearson type III curve was selected for this study to analyze the distribution frequency of annual rainfall and rainfall amount following seven growth stages of winter wheat crop in 29 stations of Northern Weihe loess plateau. As a result of our study, annual precipitation is gradually increasing from southwest to northeast of Northern Weihe loess plateau. The highest amount of annual precipitation occurred in the Baoji area and the lowest precipitation covered by the northwest area of Northern Weihe loess plateau. Moreover, the amount of rainfall of seven growth stages indicates that excessive rainfall occurs not only in the first stage (sowing to tillering) and seventh stage (flowering to ripening) but also in second stage (tillering to wintering). In the seventh stage, a large amount of excessive rainfall occurred in Changwu, Bin, Qianyang, Fengxiang, Baojiqu, and Baojixian. Moreover, water shortage is distributed in the third stage (from wintering to greening), the fourth stage (from greening to jointing), the fifth stage (from jointing to heading), and the sixth stage (from heading to flowering). Furthermore, the worst water shortages occurred in Hancheng, Heyang, Chengcheng, Pucheng, Dali, Tongchuan, and Fuping in the fourth stage (greening to jointing stage). Even though we study the crop water requirement under extreme rainfall conditions, the am 展开更多
关键词 Extreme PRECIPITATION Annual PRECIPITATION SEVEN Growth Stages Winter Wheat Crop Rainfall Excess Water SHORTAGE NORTHERN Weihe Loess Plateau
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Analysis of Rainfall Dynamics in Conakry, Republic of Guinea 认领
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作者 Ibrahima Kalil Kante Sa?dou Moustapha Sall +4 位作者 Daouda Badiane Ibrahima Diouf Abdoul Lahat Dieng Idrissa Diaby Fran?oise Guichard 《大气和气候科学(英文)》 2020年第1期1-20,共20页
Observed rainfall data of the National Meteorological Service of Guinea (NMS) exhibit that synoptic station usually records the largest rainfall amount in Guinea. Only few studies have been done on this rainfall peak ... Observed rainfall data of the National Meteorological Service of Guinea (NMS) exhibit that synoptic station usually records the largest rainfall amount in Guinea. Only few studies have been done on this rainfall peak observed in Conakry. This work better analyses the atmospheric dynamics leading to rainfall particularity. Using NMS data from 1981 to 2010, the monthly contribution and mean seasonal cycle of each station has been done. These findings of the study show that between July and August (rainfall season peak), the coastline particularly Conakry records the largest amount of rainfall. Using Era Interim data for the common period (1981-2010), we also investigate the rainfall dynamics in the lower level (1000 hPa - 850 hPa) from precipitable water, divergence, and moisture flow transport. There is a west and southwest moisture flow transport explained by a strong moisture convergence in the coastal region (Lower-Guinea). Furthermore, values of precipitable water in the same region are found, in agreement with the high moisture flow transport gradient. These incoming flow (west and south-west) undergo a return by blocking’s Kakoulima range (foehn effect) and Fouta Djallon massif to initiate convection clouds on the Guinean coast. These processes enhance a convergence of moisture associated with orographic origin convection. This has an important effect by increasing the rainfall amount in Conakry. 展开更多
关键词 Conakry GUINEA MAXIMUM RAINFALL Precipitable Water DIVERGENCE MOISTURE Flow
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Evaluation of Onset and Cessation of Rainfall and Temperature on Maize Yield in Akure, Ondo State, Nigeria 认领
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作者 Idumu A. Mosunmola Ishaya K. Samaila +1 位作者 Bello Emmanuel Ifeka Adolphus 《大气和气候科学(英文)》 2020年第2期125-145,共21页
Temperature and rainfall are important variables that affect maize yield, and as such this study aimed at evaluating the impact of onset, cessation of rainfall and temperature on maize yield in Akure. To achieve this ... Temperature and rainfall are important variables that affect maize yield, and as such this study aimed at evaluating the impact of onset, cessation of rainfall and temperature on maize yield in Akure. To achieve this objective, climatic parameters comprising daily rainfall and temperature (maximum and minimum temperature) 1981-2016 for Akure, were obtained from the archives of the Nigerian Meteorological Agency, NiMet. Annual maize yield data for the same period 2000-2016 were obtained from Ondo State Agricultural Development Programme. Walter’s method, as modified by [1], was then used to determine the onset, cessation and length of growing season. The significance of the annual trend of these climatic parameters was also tested using an approach involving z-test and p-value analysis. Likewise, the significance of all the climatic parameters contributing to maize yield was also determined based on the p-value approach under a null hypothesis. The coefficients of determination (R2) and Pearson correlation coefficient (r) in relation to the SLR and MLR models were calculated. The result showed a slight decreasing trend of rainfall, increasing trend of maximum, minimum and maize yield. Their associated p-values are 0.6925, 0.5794, 0.5136 and 0.0630, which showed that the trend over the years was not statistically significant at the 1%, 5% and 10% levels;however maize yield was significant at 10% significant level. The mean onset, cessation and length of growing season for Akure were 8th March ± 9, 21st October ± 21 and 239 days ± 27 days. The relationship between maize yield and all climatic variables in association with SLR model showed that rainfall was the major contributing variable to maize yield in Akure, Ondo State at all significant levels (p-value (0.009539) r = 61%, R2 = 37%). The p-value in association with MLR model, also showed that rainfall was significant at 5% and 10%. P (0.019412) r = 72%, R2 = 51%. 展开更多
关键词 ONSET CESSATION RAINFALL Temperature MAIZE Yield
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Subtle Impacts of Temperature and Rainfall Patterns on Land Cover Change Overtime and Future Projections in the Mara River Basin, Kenya 认领
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作者 Fredrick M. Mngube Raphael Kapiyo +2 位作者 Paul Aboum Douglas Anyona Gabriel O. Dida 《土壤科学期刊(英文)》 2020年第9期327-358,共32页
The interactive and cumulative effect of temperature and rainfall on land cover change is a priority at global, regional and local scale. This study examined changes in six land cover categories (forestland, grassland... The interactive and cumulative effect of temperature and rainfall on land cover change is a priority at global, regional and local scale. This study examined changes in six land cover categories (forestland, grasslands, shrub land, bare land, built-up areas and agricultural lands) in four sub-catchments (Amala, Nyangores, Talek and Sand River), of the Mara River basin over a 30-year period (1987-2017) and made predictions of future land cover change patterns. Landsat Imageries of 90 m resolution were retrieved and analyzed using ArcGIS 10.0 software. Relationship between NDVI, temperature and precipitation was determined using Pearson’s correlation coefficient, while Markov chains analyses were performed on different land cover categories to project future trends. Results showed low to moderate (R<sup>2</sup> = 0.002 to 0.6) trends of change in NDVI of different land cover categories across all sub-catchments. The greatest change (R<sup>2 </sup>0.34 to 0.5) was recorded in bare land in three of the four sub-catchments studied. Precipitation showed a strong positive correlation with built-up areas, forestlands, croplands, bare land, grasslands and shrub lands, while temperature correlated strongly but negatively with the same land cover categories. The change detection matrix projected significant but varying changes in land cover categories across the four sub-catchments by 2027. This study underscores the impact of changing climatic factors on various land cover categories in the Mara River basin sub-catchments, with different land cover categories exhibiting strong positive sensitivity to high precipitation and low temperature and vice-versa. 展开更多
关键词 Land Cover Change Detection TEMPERATURE Rainfall Sub-Catchments Mara River Kenya
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Rainfall Estimation using Image Processing and Regression Model on DWR Rainfall Product for Delhi-NCR Region 认领
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作者 Kuldeep Srivastava Ashish Nigam 《大气科学研究(英文)》 2020年第1期9-15,共7页
Observed rainfall is a very essential parameter for the analysis of rainfall,day to day weather forecast and its validation.The observed rainfall data is only available from five observatories of IMD;while no rainfall... Observed rainfall is a very essential parameter for the analysis of rainfall,day to day weather forecast and its validation.The observed rainfall data is only available from five observatories of IMD;while no rainfall data is available at various important locations in and around Delhi-NCR.However,the 24-hour rainfall data observed by Doppler Weather Radar(DWR)for entire Delhi and surrounding region(up to 150 km)is readily available in a pictorial form.In this paper,efforts have been made to derive/estimate the rainfall at desired locations using DWR hydrological products.Firstly,the rainfall at desired locations has been estimated from the precipitation accumulation product(PAC)of the DWR using image processing in Python language.After this,a linear regression model using the least square method has been developed in R language.Estimated and observed rainfall data of year 2018(July,August and September)was used to train the model.After this,the model was tested on rainfall data of year 2019(July,August and September)and validated.With the use of linear regression model,the error in mean rainfall estimation reduced by 46.58% and the error in max rainfall estimation reduced by 84.53% for the year 2019.The error in mean rainfall estimation reduced by 81.36% and the error in max rainfall estimation reduced by 33.81%for the year 2018.Thus,the rainfall can be estimated with a fair degree of accuracy at desired locations within the range of the Doppler Weather Radar using the radar rainfall products and the developed linear regression model. 展开更多
关键词 Rainfall estimation Rainfall analysis Doppler Weather Radar Precipitation Accumulation Product Image processing Linear regression model
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Impact of Meteorological Drought on Streamflows in the Lobo River Catchment at Nibéhibé, Côte d’Ivoire 认领
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作者 Bérenger Koffi Zilé Alex Kouadio +3 位作者 Kouakou Hervé Kouassi Affoué Berthe Yao Martin Sanchez Kouakou Lazare Kouassi 《水资源与保护(英文)》 2020年第6期495-511,共17页
The management of water resources in watersheds has become increasingly difficult in recent years due to the frequency and intensity of drought sequences. The Lobo River catchment, like most tropical regions, has expe... The management of water resources in watersheds has become increasingly difficult in recent years due to the frequency and intensity of drought sequences. The Lobo River catchment, like most tropical regions, has experienced alternating wet and dry periods. These drought periods have a significant impact on the availability of water resources in the basin. The objective of this study is to analyse the impact of meteorological drought on flows in the Lobo River catchment. Therefore, using the Normalized Precipitation and Evapotranspiration Index (SPEI) and the Drought Flow Index (SDI), the characteristics of droughts were studied. The results of this study show that meteorological droughts were more frequent than hydrological droughts in the Lobo River watershed. However, the hydrological drought was longer and more intense than the meteorological drought. The greater relationship between meteorological and hydrological drought was observed at the Daloa and Vavoua station (0.43 < r < 0.50) compared to the Zuenoula station (r < 0.5). In addition, there was a resumption of precipitation and runoff between 2007 and 2013 in the basin. The study of these climatic trends would be very useful in the choice of management and adaptation policies for water resources management. 展开更多
关键词 RAINFALL Normalized Index Meteorological Drought Hydrological Drought Lobo River
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On the Study of the Spatio-Temporal Variations in Intensity of 30 - 60-Day Intraseasonal Rainfall Oscillations in Central Africa Using Wavelet-Based Indices 认领
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作者 Alain Tchakoutio Sandjon Armand Nzeukou 《地球科学和环境保护期刊(英文)》 2020年第2期15-32,共18页
The intraseasonal timescale is attractive in Central Africa (CA) where socio-economic activities are highly based on rainfall. The parameterization of intraseasonal oscillations (ISO) then remains a great challenge fo... The intraseasonal timescale is attractive in Central Africa (CA) where socio-economic activities are highly based on rainfall. The parameterization of intraseasonal oscillations (ISO) then remains a great challenge for the improvement of sub-seasonal to seasonal (S2S) prediction in this region. In this paper, we applied wavelet analysis on the 2.5° × 2.5° daily Outgoing Longwave Radiation (OLR, used here as rainfall proxy) to study the variations in the intensity of the 30 - 60-day intraseasonal rainfall oscillations over Central Africa within the last three decades (1980-2009). Results showed that the mean ISO intensity (ISOI) strongly fluctuates from day to another. The plots of monthly mean ISOIs revealed that the ISO activity is highly seasonal with above-normal ISO intensity during December-May and below-normal activity during June-November. The analysis of yearly mean ISOI showed that the ISOI exhibits strong interannual variations with the years of very low ISOIs such as 1982, 1994, 2001, 2007, 2009, 2015 and the years of very high ISOIs such as 1981, 1985, 1986, 989/1990, 1997, 2003, 2005. The regression analysis between ISOI and El Ni&#241o Southern Oscillation (ENSO) indices showed that even though the relationship between ISO and ENSO is nonlinear, warm ENSO (El Ni&#241o) events tend to reduce the ISOIs while cold ENSO (La Ni&#241a) events tend to increase it. 展开更多
关键词 RAINFALL INTRASEASONAL OSCILLATIONS INTENSITY WAVELET Analysis
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黄土丘陵区雨强对水流含沙量的影响 认领
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作者 刘晓燕 党素珍 +1 位作者 刘昌明 董国涛 《地理学报:英文版》 SCIE CSCD 2020年第3期455-467,共13页
To study the effects of changes in the rainfall intensity on sediment concentrations in the Loess Plateau,the observed rainfall intensities and sediment concentrations from three typical small watersheds were used to ... To study the effects of changes in the rainfall intensity on sediment concentrations in the Loess Plateau,the observed rainfall intensities and sediment concentrations from three typical small watersheds were used to analyze the relationship between these parameters.The results showed that the sediment concentration generally increased with the increasing rainfall intensity on slope scale.However,at watershed scale,a significant threshold phenomenon was observed for the effects of the rainfall intensity on the sediment concentration.When the rainfall intensity exceeds the threshold,the flood sediment concentration will no longer increase with the increase in the rainfall intensity.The rainfall intensity threshold increased with increasing vegetation coverage.The rainfall intensity threshold was 10–15 mm/h during 1956–1969,reached 20 mm/h from 1990 to 1997 and is approximately 40 mm/h at present.Due to a rainfall intensity of 10–15 mm/h almost happened every year,the vegetation did not change much from the 1950s to 1980s.Sediment yield mainly depends on soil erosion caused by surface flow,but the surface flow speed does not increase indefinitely with the increase in the flow discharge.Thus,the annual maximum sediment concentration of the tributaries in the loess area has been basically stable before the 1990s. 展开更多
关键词 Loess Plateau loess hilly region rainfall intensity sediment concentration INFLUENCE
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