Potential Dust Induced Changes on the Seasonal Variability of Temperature Extremes Over the Sahel: A Regional Climate Modeling Study

Ibrahima Diba,Hamady Ngansou Sabaly,Jules Basse,Moctar Camara,Mamadou Ndiaye,Arona Diedhiou

doi:10.3389/feart.2020.591150

Ibrahima Diba, Hamady Ngansou Sabaly + Show 4 more

Open Access

https://doi.org/10.3389/feart.2020.591150

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Abstract

The aim of this study is to simulate the impact of mineral dust emissions from the Sahel–Saharan zone on temperature extremes over the Sahel. To achieve this goal, we performed two numerical simulations: one with the standard version of the regional climate model RegCM4 (no dust run) and another one with the same version of this model incorporating a dust module (dust run). The difference between both versions of the model allowed to isolate the impacts of mineral dust emissions on temperature extremes. The results show that the accumulation of mineral dust into the atmosphere leads to a decrease of the frequency of warm days, very warm days, and warm nights over the Sahel. This decrease is higher during the MAM (March-April-May) and JJA (June-July-August) periods especially in the northern and western parts of the Sahel. The impact of the mineral dust emissions is also manifested by a decrease of the frequency of tropical nights especially during MAM in the northern Sahel. When considering the warm spells, mineral particles tend to weaken them especially in MAM and JJA in the northern Sahel. To estimate the potential impacts of the mineral dust accumulation on heat stress, the heat index and the humidex are used. The analysis of the heat index shows that the dust impact is to reduce the health risks particularly in the northern Sahel during the MAM period, in the western Sahel during JJA, and in the southern and the northeastern parts of the Sahel during the SON (September-October-November) period. As for the humidex, it is characterized by a decrease especially in the northern Sahel for all seasons. This reduction of the occurrence of thermal extremes may have a positive effect on the energy demand for cooling and on global health. However, the accumulation of dust particles in the atmosphere may also increase the meningitis incidence and prevalence.

Highlights

The third of the earth’s surface is a potential source of dust
The results showed that the RegCM4 model has low biases of rainfall and surface temperature, reflecting its good ability to simulate the West African climate and in particular that of the Sahel
The AERONET data exhibit the maxima of the aerosol optical depth from May to July over the Cape Verde and Dakar stations and the minima from November to April (Figures 2A,C). These results are in agreement with the findings of Fouquart et al (1987), Dubovik et al (2001), and Jones et al (2003), who showed that during the wet season (June-July-August), intense convective systems and African easterly waves are responsible for important emissions of mineral dust over the southern Sahara and the Sahel

Summary

Introduction

The third of the earth’s surface is a potential source of dust. Marticorena et al (2011) showed that the Sahara desert is the largest source of mineral dust in the world. Li et al (1996) showed that desert dust is the dominant element in the diffusion of solar radiation in the North Atlantic. Because of their absorption (direct effects) and diffusion (indirect effects) properties, these natural aerosols (mineral dust) have a nonnegligible impact on the solar radiation and on the earth’s radiation balance (Liao and Seinfeld 1998; Gao et al 2000; Tanré et al 2003; Dahutia et al 2018). N’Datchoh et al (2018) showed that the mineral dust particles emitted from the Sahara and the Sahel and the biomass burning aerosols are frequently loaded in the atmosphere and represent an important part of the aerosols which interact directly with the West African monsoon system

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