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Characteristics of Extreme Rainfall Events over Uganda during September to November Rainfall Season

Journal of Geoscience and Environment Protection 2024年第3期12卷 131-152页

作者： Donnata Alupot Guirong Tan Kokou Romaric Posset Peter Natiko Key Laboratory of Meteorological Disaster Ministry of Education (KLME)/Joint International Research Laboratory of Climate and Environment Change (ILCEC)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters (CIC-FEMD) Nanjing University of Information Science and Technology Nanjing China Climate Change Department Pan African University Institute for Water and Energy Sciences (Including Climate Change) C/O Univer-sité Abou Bekr Belkaid Tlemcen Campus Chetouane Tlemcen Algeria Directorate of Weather Forecasting Uganda National Meteorological Authority Port Bell Road Kampala Uganda

Understanding the characteristics of extreme rainfall is crucial for effective flood management planning, as it enables the incorporation of insights from past extreme rainfall patterns and their spatiotemporal distribution. This work investigated the changes in the frequency and pattern of extreme rainfall over Uganda, using daily datasets sourced from Climate Hazard Group InfraRed Precipitation with Station (chirps-v2) for the period 1981 to 2022. The study utilized the extreme weather Indices provided by the Expert Team on Climate Change Detection and Indices (ETCCDI). Attention was directed towards September to November (SON) rainfall season with precise analysis of four indices (Rx1day, Rx5day, R95p, and R99p). The Sequential Mann-Kendall (SQMK) non-parametric test was applied to identify abrupt changes in SON extreme rainfall trends. Results showed that October consistently recorded the highest count of extreme rainfall days across all four indices. The long-term analysis revealed fluctuations in extreme rainfall events across years, with certain periods exhibiting heightened intensity. The analysis portrayed a shift in the decadal variations and region-specific distribution of extreme rainfall, with Eastern Uganda and areas around Lake Victoria standing out compared to other regions. The findings further revealed an increase in extreme rainfall for all indices in the recent decade (2011-2022) with 2019/2020 standing out as the extreme years of SON for the study period. While trendlines suggested a slight increase in intense daily rainfall events, the SQMK tests revealed statistical significance in the trend of prolonged periods of intense daily rainfall. This study contributes to the understanding of the spatiotemporal variability and trends of extreme rainfall events over Uganda during the SON season, which is crucial for the assessment of climate change impacts and adaptation strategies. It provides valuable information for seasonal extreme rainfall forecasting, development of early warning systems, floo

关键词： chirps Variability Region-Specific Early Warning Climate Change

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Analysis of the Drought Impact as an Extreme Climatic Event in Sudan

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Journal of Geoscience and Environment Protection 2024年第6期12卷 38-47页

作者： Awad Hussien School of Atmospheric Science Nanjing University of Information Science & Technology Nanjing China

This study aimed to investigate drought as an extreme climatic event in Sudan by utilizing the Anomaly and Standard Precipitation Index (SPI). This research employed high-resolution Climate Hazards Group Infrared Precipitation with Station (chirps) data to analyze the temporal and spatial distribution of rainfall in Sudan from 2001 to 2015. Notably, the analysis compared the annual average precipitation to specific drought events and calculated the Standardized Precipitation Index (SPI). The results indicate a striking frequency of drought occurrence in Sudan, with SPI values suggesting similarities between drought and wet years. It is recommended to compute the SPI for individual stations rather than rely solely on area averages. Despite the comparable SPI values between the drought and wet years, this study emphasizes the profound impact of drought as a recurring phenomenon in Sudan. These findings emphasize the urgent need for proactive drought management and mitigation strategies in Sudan to effectively address the consequences of this climatic challenge.

关键词： chirps SPI Anomaly Rainfall Aridity

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Evaluating the accuracy of two satellite-based Quantitative Precipitation Estimation products and their application for meteorological drought monitoring over the Lake Victoria Basin,East Africa

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Geo-Spatial Information Science 2022年第3期25卷 500-518页

作者： Priyanko Das Zhenke Zhang Hang Ren Center of African Studies Nanjing UniversityNanjingChina and School of Geographic and Oceanographic SciencesNanjing UniversityNanjingChina Center of African Studies Nanjing UniversityNanjingChina and School of Geographic and Oceanographic SciencesNanjing University Nanjing China Institute of Population Studies Nanjing University of Posts and TelecommunicationsNanjingJiangsu provinceChina

This study evaluates the high-resolution satellite estimated long-term precipitation data for monitor-ing the drought condition over the Lake Victoria Basin(LVB)from 1984 to 2020.Standardized Precipitation Indices(SPI)were used to capture the short,medium and long-term meteorological drought conditions at multiple time scales(i.e.3,6,and 12).For these,the following two primaries Quantitative Precipitation Estimation(QPEs)products were employed-1)Climate Hazards group Infra-Red Precipitation with Station(chirps),and 2)the Precipitation Estimation from Remotely Sensed Information using Artificial Neural Network-Climate Data Record(PERSIANN-CDR).This dataset was compared based on the observation data obtained from the Climate Research Unit(CRU)over the nine selected regions surrounding lake basins.The performance of these two QPEs products was evaluated using seven statistical metrics.The findings of this study indicate that the chirps and PERSIANN-CDR datasets could capture the behavior of drought magnitude based on the time scale of SPI-3,SPI-6,SPI-12.The results indicate that 2012 and 2017 are significant severe drought years in the recent decade over LVB.However,the chirps datasets provide good agreement(Correlation Coefficient(CC)=0.65)with observation,whereas PERSIANN-CDR present satisfactory results(CC=0.54).In addition,Hurst(H)exponent was used to predict the future drought trend and found that the chirps performed well to predict the degree of drought trend.Therefore,this study considers the chirps product for near-real-time drought monitoring and PERSIANN-CDR for historical drought assessment.Moreover,the outcome from the H values is greater than 0.5,which indicates the future drought trend would be decreased over LVB.These results are useful for developing the strategies for drought hazards and water resource management in LVB.

关键词： chirps CRU hurst exponent PERSIANN-CDR SPI

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Application assessment of GRACE and chirps data in the Google Earth Engine to investigate their relation with groundwater resource changes (Northwestern region of Iran)

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Journal of Groundwater Science and Engineering 2021年第2期9卷 102-113页

作者： Afraz Mehdi Eftekhari Mobin Akbari Mohammad Ali Haji Elyasi Noghani Zahra Forests Range and Watershed Management OrganizationTehranIran Young Researchers and Elite Club Mashhad BranchIslamic Azad UniversityMashhadIran Department of Civil Engineering University of BirjandBirjandIran K.N.Toosi University of Technology TehranIran Master Research Institute of Forest and Rangeland TehranIran

In recent years,drought has become a global issue,especially in arid and semi-arid areas.It is without doubt that the identification and monitoring of the drought phenomenon can help to reduce the damages that would occur.In addition,rain is one of the factors which directly affect the water levels of underground water reservoirs.This research applied a linear gradient regression method developed on the basis of GRACE,chirps,and data from monitoring wells to investigate the groundwater storage changes.These data have been analyzed on the Google Earth Engine platform.In order to conduct temporal and spatial analyses,the water levels of the aquifer were generated from the monitoring wells and zoned into five classes.Also,the amount of water storage and rain from the year 2003 to 2017 in the West Azerbaijan Province were investigated using the GRACE satellite and the chirps data,respectively.The results obtained from the GRACE satellite data show that the average water level in the underground reservoirs in Iran had started to decrease since 2008 and reached its peak in 2016 with an average decrease of 16 cm in that year.The average annual decline of groundwater level in the studied time period was 5 cm.A chart developed from the chirps annual rainfall data indicates that the biggest decline in rainfall occurred in 2008,and the declining trend has remained steady.Linear analyses were made on GRACE with chirps results and monitoring wells data separately,from which the correlation coefficients are between 86% and 97%,showing generally high correlations.Furthermore,the results obtained from the zoning of the aquifer showed that in the period of 2004 to 2016,due to the decrease in rainfall and the excessive withdrawal of groundwater,the water levels also decreased.

关键词： GRACE Groundwater storage chirps Middle East region

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chirps和GLEAM卫星产品在中国的干旱监测效用评估

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农业工程学报 2019年第15期35卷 146-154页

作者：任立良卫林勇江善虎史俊超袁飞张林齐刘若兰河海大学水文水资源与水利工程科学国家重点实验室南京210098 河海大学水文水资源学院南京210098 水利部水文水资源监测预报中心北京100053

为评估具有分辨率高、覆盖范围广、数据序列动态连续优点的卫星降水和潜在蒸散发产品在中国干旱监测中的应用能力,以CGDPA(China gauge-based precipitation daily analysis dataset)和PM-Ep(potential evapotranspiration calculated by penman-monteith)为基准数据,以标准化降水蒸散指数(standardized precipitation evapotranspiration index,SPEI)为干旱监测指标,利用6个精度统计指标和分类度量指标评估chirps(climate hazards group infrared precipitation with station data)、GLEAM-Ep(global land-surface evaporation:the Amsterdam methodology,potential evapotranspiration)在中国的干旱监测效用。结果表明:1)chirps和GLEAM-Ep在中国东部和西南地区表现良好。由于气象站格网的稀疏,它们在中国西部大部分地区的表现存在较大不确定性。2)SPEIs(基于chirps和GLAEM-Ep计算的SPEI)在中国东部和西南地区对干旱模拟效果较好,其与SPEIm(基于CGDPA和PM-Ep计算的SPEI)的相关系数(CC)在东南、西南、长江中下游地区、华北均大于0.6,尤其是相对湿润地区的CC值在0.70以上且均方根误差低于0.8。3)SPEIs3(3个月的SPEIs)在东南、西南、长江中下游地区、华北对干旱面积比的演变过程模拟效果较好,持续干旱模拟成功率分别为0.93、0.57、0.71、0.81及干旱空间分布模拟精度较高。总体而言,基于长序列chirps和GLEAM-Ep计算的SPEI可适用于中国东部和西南地区的干旱监测与评价,可为该地区的干旱事件监测与预警、水资源管理提供可靠的参考依据。

关键词：降水干旱遥感 chirps GLEAM-Ep 潜在蒸散发标准化降水蒸散指数(SPEI)

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Evaluation of chirps Satellite Gridded Dataset as an Alternative Rainfall Estimate for Localized Modelling over Uganda

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Atmospheric and Climate Sciences 2021年第4期11卷 797-811页

作者： Ivan Bamweyana Moses Musinguzi Lydia Mazzi Kayondo Department of Geomatics and Land Management Makerere University Kampala Uganda

The Ugandan economy is largely dependent on rural-based and rain-fed agriculture. This creates a critical need to understand the rainfall dynamics at the local scale. However, the country has a sternly sparse and unreliable rain gauge network. This research, therefore, sets out to evaluate the use of the CHIRPS satellite gridded dataset as an alternative rainfall estimate for local modelling of rainfall in Uganda. Complete, continuous and reliable in situ station observations for the period between 2012 and 2020 were used for the comparison with CHIRPS satellite data models in the same epoch. Rainfall values within the minimum 5 km and maximum 20 km radii from the in situ stations were extracted at a 5 km interval from the interpolated in situ station surface and the CHIRPS satellite data model for comparison. Results of the 5 km radius were adopted for the evaluation as it’s closer to the optimal rain gauge coverage of 25 km2. They show the R2 = 0.91, NSE = 0.88, PBias = -0.24 and RSR = 0.35. This attests that the chirps satellite gridded datasets provide a good approximation and simulation of in

关键词： Spatial Statistics chirps Satellite Gridded Dataset Rainfall Estimates

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Stability of Efficient Deterministic Compressed Sensing for Images with chirps and Reed-Muller Sequences

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Applied Mathematics 2013年第1期4卷 183-196页

作者： Somantika Datta Kangyu Ni Prasun Mahanti Svetlana Roudenko Department of Mathematics George Washington University Washington DC USA Department of Mathematics University of Idaho Moscow USA HRL Laboratories LLC Malibu USA School of Electrical Computer and Energy Engineering Arizona State University Tempe USA

We explore the stability of image reconstruction algorithms under deterministic compressed sensing. Recently, we have proposed [1-3] deterministic compressed sensing algorithms for 2D images. These algorithms are suitable when Daubechies wavelets are used as the sparsifying basis. In the initial work, we have shown that the algorithms perform well for images with sparse wavelets coefficients. In this work, we address the question of robustness and stability of the algorithms, specifically, if the image is not sparse and/or if noise is present. We show that our algorithms perform very well in the presence of a certain degree of noise. This is especially important for MRI and other real world applications where some level of noise is always present.

关键词： Compressed Sensing Reed-Muller Sequences chirps Image Reconstruction

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Radar ambiguity function in L_p frame

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Science China Mathematics 2000年第8期43卷 785-791页

作者： M.Y.CHI 齐民友 Institute of Mathematics Wuhan University Wuhan 430072 China

In modern radar techniques, pulse signal can be replaced by the chirps, which is taken to be signals in Lp space. Wigner’s function and ambiguity functions are constructed in an Lp frame and a partial generalization ... 详细信息

关键词： radar signals chirps principle of uncertainty coherent dual Wigner’s function ambiguity function.

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