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Earth System Dynamics An interactive open-access journal of the European Geosciences Union
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Discussion papers
https://doi.org/10.5194/esd-2019-20
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/esd-2019-20
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 24 May 2019

Submitted as: research article | 24 May 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Earth System Dynamics (ESD).

Impact of precipitation and increasing temperatures on drought in eastern Africa

Sarah F. Kew1, Sjoukje Y. Philip1, Mathias Hauser2, Mike Hobbins3,4, Niko Wanders5, Geert Jan van Oldenborgh6, Karin van der Wiel6, Ted I.E. Veldkamp1, Joyce Kimutai7, Chris Funk8,9, and Friederike E. L. Otto10 Sarah F. Kew et al.
  • 1Institute for Environmental Studies, Vrije Universiteit, Amsterdam, the Netherlands
  • 2Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
  • 3Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, Colorado
  • 4Physical Sciences Division, NOAA/Earth System Research Laboratory, Boulder, Colorado
  • 5Department of Physical Geography, Utrecht University, Utrecht, the Netherlands
  • 6Royal Netherlands Meteorological Institute (KNMI), De Bilt, the Netherlands
  • 7Kenya Meteorological Department, Nairobi, Kenya
  • 8U.S. Geological Survey Center for Earth Resources Observation and Science, Sioux Falls, South Dakota
  • 9University of California, Santa Barbara, Santa Barbara, California
  • 10School of Geography and the Environment, University of Oxford, Oxford, UK

Abstract. In eastern Africa droughts can cause crop failure and lead to food insecurity. With increasing temperatures, there is an a priori assumption that droughts are becoming more severe, however, the link between droughts and climate change is not sufficiently understood. In the current study we focus on agricultural drought and the influence of high temperatures and precipitation deficits on this.

Using a combination of models and observational datasets, we studied trends in six regions in eastern Africa in four drought-related annually averaged variables – soil moisture, precipitation, temperature and, as a measure of evaporative demand, potential evapotranspiration (PET). In standardized soil moisture data, we find no discernible trends. Precipitation was found to have a stronger influence on soil moisture variability than temperature or PET, especially in the drier, or water-limited, study regions. The error margins on precipitation-trend estimates are however large and no clear trend is evident. We find significant positive trends in local temperatures. However, the influence of these on soil moisture annual trends appears limited as evaporation is water limited. The trends in PET are predominantly positive, but we do not find strong relations between PET and soil moisture trends. Nevertheless, the PET-trend results can still be of interest for irrigation purposes as it is PET that determines the maximum evaporation rate.

We conclude that, until now, the impact of increasing local temperatures on agricultural drought in eastern Africa is limited and recommend that any soil moisture analysis be supplemented by analysis of precipitation deficit.

Sarah F. Kew et al.
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Short summary
Motivated by the possible influence of rising temperatures, this study synthesises results from observations and climate models to explore trends (1900–now) in eastern African (EA) drought measures. However, no discernible trends are found in annual soil moisture or precipitation. Positive trends in potential evaporation indicate that, for irrigated regions, more water is now required to counteract increased evaporation. Precipitation deficit is, however, the most useful indicator of EA drought.
Motivated by the possible influence of rising temperatures, this study synthesises results from...
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