Role of dust direct radiative effect on the tropical rain belt over middle east and North Africa: A high-resolution AGCM study

Abstract

To investigate the influence of direct radiative effect of dust on the tropical summer rain belt across the Middle East and North Africa (MENA), the present study utilizes the high-resolution capability of an Atmospheric General Circulation Model, the High-Resolution Atmospheric Model. Ensembles of Atmospheric Model Intercomparison Project style simulations have been conducted with and without dust radiative impacts, to differentiate the influence of dust on the tropical rain belt. The analysis focuses on summer season. The results highlight the role of dust-induced responses in global- and regional-scale circulations in determining the strength and the latitudinal extent of the tropical rain belt. A significant response in the strength and position of the local Hadley circulation is predicted in response to meridionally asymmetric distribution of dust and the corresponding radiative effects. Significant responses are also found in regional circulation features such as African Easterly Jet and West African Monsoon circulation. Consistent with these dynamic responses at various scales, the tropical rain belt across MENA strengthens and shifts northward. Importantly, the summer precipitation over the semiarid strip south of Sahara, including Sahel, increases up to 20%. As this region is characterized by the “Sahel drought,” the predicted precipitation sensitivity to the dust loading over this region has a wide range of socioeconomic implications. Overall, the study demonstrates the extreme importance of incorporating dust radiative effects and the corresponding circulation responses at various scales, in the simulations and future projections of this region’s climate.