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Heterogeneous Trends of Precipitation Extremes in Recent Two Decades over East Africa

Abstract

East Africa is so vulnerable to the impacts of precipitation extremes varying from frequent floods to prolonged droughts. However, systematic regional assessment of precipitation extremes across seasons has received little attention, and most previous studies of precipitation extremes have employed many indices and sparse gauge observations giving marginalized details. In this study, we use three precipitation extreme indices to examine the intensity of the highest single-day rainfall record (rx1day), prevalence of very heavy rainfalls (r30mm), and persistence of successive wet days (cwd) at both annual and seasonal scales over recent two decades (1998–2018) based on the Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis data. The results show that the most intensive and frequent precipitation extremes are noticeable from January to May across the areas extending from Madagascar to the Tanzanian coastal zone. These areas also exhibit patches of significant increasing trends in frequency, duration, and intensity of precipitation extremes annually and seasonally. However, significant declines in frequency and intensity of precipitation extremes are observed from western Ethiopia to Congo-Uganda, especially in June-September. The October–December season witnesses higher interannual variability amounting to overall weak and less significant trends. Further subregional assessment shows overall declining intensity and frequency of precipitation extremes in northern part of the study areas. Mean wetness duration increased, with persistence of moderate wet days and slight reduction of severe events. This study unveils higher susceptibility of the East African region to the widely observed hotspots of precipitation extremes posing threats to food security, water resource, and human well-being. The region should consider upscaling irrigation schemes in addition to planning resilient and supportive infrastructures to withstand the upsurging precipitation extremes, especially along the coastal zone.

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Acknowledgments

The TRMM Multisatellite Precipitation Analysis (TMPA 3B42) is freely available online at https://doi.org/10.5067/TRMM/TMPA/DAY/7. Topographical elevation of the study domain uses the quality-controlled global Digital Elevation Model (DEM) data from the Global Land One-km Base Elevation (GLOBE) Project acquired from NOAA NGDC GLOBE data library at https://iridl.ldeo.columbia.edu/SOURCES/.NOAA/.NGDC/.GLOBE/topo/datafiles.html. The R software package for ClimPACT2 is available on Git-Hub at https://github.com/ARCCSS-extremes/climpact2. Data analysis and graphics visualization throughout this study are mostly done by using NCAR Command Language (NCL) Version 6.6.2 (https://doi.org/10.5065/D6WD3XH5) software (Meier-fleischer et al., 2017).

Funding

Supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (CAS)—CAS Big Earth Data Science Engineering Program (XDA19030401) and National Key Research and Development Program of China (2016YFA0600303).

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Correspondence to Gensuo Jia.

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Mtewele, Z.F., Xu, X. & Jia, G. Heterogeneous Trends of Precipitation Extremes in Recent Two Decades over East Africa. J Meteorol Res 35, 1057–1073 (2021). https://doi.org/10.1007/s13351-021-1028-8

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  • DOI: https://doi.org/10.1007/s13351-021-1028-8

Key words

  • precipitation extremes
  • East Africa
  • extreme indices
  • Tropical Rainfall Measuring Mission (TRMM)
  • climate extremes