Long-term trends in rainfall and temperature using high-resolution climate datasets in East Africa

Christian Bernhofer,Stephan Hülsmann,Solomon H. Gebrechorkos

doi:10.1038/s41598-019-47933-8

Abstract

Detecting changes in climate is a prerequisite for a better understanding of the climate and developing adaptation and mitigation measures at a regional and local scale. In this study long-term trends in rainfall and maximum and minimum temperature (T-max and T-min) were analysed on seasonal and annual time scales for East Africa. High resolution gridded rainfall (1981–2016) and temperature (1979–2010) data from international databases like the Climate Hazards Group are used. Long-term seasonal trend analysis shows a non-significant (except for small areas), decreasing (increasing) trend in rainfall in eastern (western) parts of Ethiopia and Kenya and a decreasing trend in large parts of Tanzania during the long rainy season. On the other hand, a non-significant increasing trend in large parts of the region is observed during the short rain season. With regard to annual trends, results largely confirm seasonal analyses: only a few significant trends in rainfall, but significant increasing trends in T-max (up to 1.9 °C) and T-min (up to 1.2 °C) for virtually the whole region. Our results demonstrate the need and added value of analysing climate trends based on data with high spatial resolution allowing sustainable adaptation measures at local scales.

Highlights

Global climate has changed in recent decades and exposes a significant impact on the environment and on social and economic well-being[1,2]
Several studies highlighted that the variability in rainfall in this region is linked to large-scale climate variability, including the ElNĩno Southern Oscillation (ENSO), Indian Ocean Dipole (IOD)[9,10], and movement of the inter-tropical convergence zone (ITCZ)[11,12]
We evaluated multiple climate data products using observed data from 332 stations provided by the National Meteorological Agency of Ethiopia and the global summary of the day, for Kenya and Tanzania, available at the National Climate Data Centre (NCDC, https://www7.ncdc.noaa.gov/)

Summary

Introduction

Global climate has changed in recent decades and exposes a significant impact on the environment and on social and economic well-being[1,2]. IOD, on the other hand, represents the sea surface temperature variability in the tropical Indian Ocean and this change significantly affects the climate of East Africa, Indonesia, India, and some parts of Australia and Asia[14]. Variability in rainfall in East Africa, the inter-annual variability, is modulated by large scale climate forcings and changes in sea surface temperature, which affects the rainfall amount (e.g., decrease during the long-rain season; March-May) by changing wind patterns and moisture fluxes[15]. One of the main limitations to perform such a comprehensive study in this region is the availability of a sufficiently long-term and spatially representative climate data from the field-based meteorological stations. We evaluated multiple climate data products (satellite-based rainfall estimates, observational reanalysis hybrid, and regional climate models) using observed data from 332 stations provided by the National Meteorological Agency of Ethiopia and the global summary of the day, for Kenya and Tanzania, available at the National Climate Data Centre (NCDC, https://www7.ncdc.noaa.gov/)

Methods

Results

Conclusion