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Volume 22, issue 6 | Copyright
Hydrol. Earth Syst. Sci., 22, 3275-3294, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 13 Jun 2018

Research article | 13 Jun 2018

Regional co-variability of spatial and temporal soil moisture–precipitation coupling in North Africa: an observational perspective

Irina Y. Petrova1,2, Chiel C. van Heerwaarden3, Cathy Hohenegger1, and Françoise Guichard4 Irina Y. Petrova et al.
  • 1Department of the Land in the Earth System, Max Planck Institute for Meteorology, Hamburg, Germany
  • 2Laboratory of Hydrology and Water Management, Ghent University, Ghent, Belgium
  • 3Meteorology and Air Quality Group, Wageningen University, Wageningen, the Netherlands
  • 4CNRM (UMR 3589 CNRS and Météo-France), Toulouse, France

Abstract. The magnitude and sign of soil moisture–precipitation coupling (SMPC) is investigated using a probability-based approach and 10 years of daily microwave satellite data across North Africa at a 1° horizontal scale. Specifically, the co-existence and co-variability of spatial (i.e. using soil moisture gradients) and temporal (i.e. using soil moisture anomaly) soil moisture effects on afternoon rainfall is explored. The analysis shows that in the semi-arid environment of the Sahel, the negative spatial and the negative temporal coupling relationships do not only co-exist, but are also dependent on one another. Hence, if afternoon rain falls over temporally drier soils, it is likely to be surrounded by a wetter environment. Two regions are identified as SMPC hot spots. These are the south-western part of the domain (7–15°N, 10°W–7°E), with the most robust negative SMPC signal, and the South Sudanese region (5–13°N, 24–34°E). The sign and significance of the coupling in the latter region is found to be largely modulated by the presence of wetlands and is susceptible to the number of long-lived propagating convective systems. The presence of wetlands and an irrigated land area is found to account for about 30% of strong and significant spatial SMPC in the North African domain. This study provides the first insight into regional variability of SMPC in North Africa, and supports the potential relevance of mechanisms associated with enhanced sensible heat flux and mesoscale variability in surface soil moisture for deep convection development.

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Short summary
In North Africa rain storms can be as vital as they are devastating. The present study uses multi-year satellite data to better understand how and where soil moisture conditions affect development of rainfall in the area. Our results reveal two major regions in the southwest and southeast, where drier soils show higher potential to cause rainfall development. This knowledge is essential for the hydrological sector, and can be further used by models to improve prediction of rainfall and droughts.
In North Africa rain storms can be as vital as they are devastating. The present study uses...