Preprints
https://doi.org/10.5194/hess-2020-113
https://doi.org/10.5194/hess-2020-113

  08 May 2020

08 May 2020

Review status: a revised version of this preprint is currently under review for the journal HESS.

Influence of initial soil moisture in a Regional Climate Model study over West Africa. Part 2: Impact on the climate extremes

Brahima Koné1, Arona Diedhiou1,2, Adama Diawara1, Sandrine Anquetin2, N'datchoh Evelyne Touré1, Adama Bamba1, and Arsene Toka Kobea1 Brahima Koné et al.
  • 1LAPAMF, Université Félix Houphouët Boigny, Abidjan, Côte d'Ivoire
  • 2Univ. Grenoble Alpes, IRD, CNRS, Grenoble INP, IGE, F-38000 Grenoble, France

Abstract. The influence of the anomalies in initial soil moisture on the climate extreme over West Africa is investigated using the fourth generation of Regional Climate Model coupled to the version 4.5 of the Community Land Model (RegCM4-CLM4.5). We applied the initial soil moisture on June 1st for two summers June–July–August–September (JJAS) 2003 and JJAS 2004 (Resp. wet and dry year in the region of interest) with 25 km of spatial resolution. We initialized the control runs with the reanalysis soil moisture of the European Centre Meteorological Weather Forecast's reanalysis of the 20th century (ERA20C), while for the dry and wet experiments, we initialized the soil moisture respectively at the wilting points and field capacity. The impact on extreme precipitation indices of the initial soil moisture, especially over the central Sahel, is homogeneous, i.e. dry (wet) experiments tend to decrease (increase) precipitation extreme indices only for precipitation indices related to the number of precipitation events, not for those related to the intensity of precipitation events. Overall, the impact on temperature extremes of the anomalies in initial soil moisture is more significant compared to precipitation extremes. Initial soil moisture anomalies unequally affect daily minimum and maximum temperature. A stronger impact is found on maximum temperature than minimum temperature. Over the entire West African domain, wet (dry) experiments cause a decrease (increase) in maximum temperature. The strongest impacts on minimum temperature indices are found mainly in wet experiments, on the Sahara where we found the higher values of the maximum and minimum daily minimum temperature indices (resp. TNx and TNn). The performance of RegCM4-CLM4.5 in simulating the ten (10) extreme rainfall and temperature indices used in this study is also highlighted.

Brahima Koné et al.

 
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Brahima Koné et al.

Brahima Koné et al.

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Short summary
The impact of the anomalies in initial soil moisture is more significant on temperature extremes than on precipitation extremes. A stronger impact is found on maximum temperature than on minimum temperature. The impact on extreme precipitation indices is homogeneous, especially over the Central Sahel and dry (wet) experiments tend to decrease (increase) number of precipitation extreme events and not their intensity.