Sagar P Parajuli 

Water is an essential element of life and rainfall. The amount of rainfall directly affects the spatial and temporal distribution of water resources on the Earth. Rainfall has direct impact on agricultural production, daily life activities, and human health. Atmospheric aerosols are essential for rainfall formation; therefore, understanding how dust compositions and distributions affect the regional rainfall pattern is of utmost importance, particularly in the region with high atmospheric dust loading, such as the Middle East and North Africa (MENA). Although aerosol-rainfall research has gained increased attention in the last few decades, many details of aerosol-cloud-rainfall interactions pathways remain unknown. In this work, dust-rainfall connection is examined using a large sample of Aerosol Optical Depth (AOD) and rainfall data from Moderate Resolution Imaging Spectroradiometer (MODIS) and Tropical Rainfall Measuring Mission (TRMM), respectively, obtained on daily basis for the years 2015 and 2016 over the MENA region. Observational analysis reveal that rainfall is oppositely related to AOD in low and high rainfall conditions. Exponentially decreasing (increasing) relationship with AOD under low (high) rainfall conditions, at a similar range of AOD in both cases, was observed. Further analysis using angstrom exponent data suggest that the positive (negative) relationship between AOD and rainfall could represent dust indirect effects during the mature (initial) stage of convection. This observational analysis provide a basis to predict rainfall under different dust loading conditions (AOD) using satellite data and provide a benchmark for improving the representation of dust effect on cloud and rainfall processes in the models, which currently have significant uncertainty. While dust and dust storms are considered nuances from air quality perspective, these results highlight their fundamental positive impact on Earth’s climate.