Modulation of spatial distribution of aerosol species by the monsoon intraseasonal oscillation over South Asia

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This study investigated the spatial and temporal modulation of aerosol species by monsoon intraseasonal oscillation (MISO) using the Copernicus Atmosphere Monitoring Service (CAMS) reanalysis and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite observations from 2003 to 2019. The climatological spatial distribution of aerosol species showed long-range transport of sea-salt and dust to Indian landmass from the Arabian Sea and desert regions of the Arabian Peninsula, respectively. While organic matter, black carbon, and sulfate originated mainly in India. In the eight MISO phases, southwesterly/westerly strengthening/weakening was responsible for aerosol species transport and spatial distribution. During MISO break to active transition phases 2-5, strong southwest monsoon winds transported sea-salt aerosols from the Arabian Sea to the Indian region. In the active-to-break transition phases 5-7, dust transport strengthened from the Arabian Peninsula. The dust aerosols over the Indian subcontinent peaked in phases 6 and 7. In phases 2-5 (6-8, 1), direction of strong winds along the Indo-Gangetic Plain influenced increased levels of organic matter, sulfate, and black carbon aerosols in the western/northwestern (eastern/northeastern) regions of India. These dynamic spatial changes in aerosols caused by MISO over the Indian region influence the shortwave and longwave radiation balances that can influence monsoon circulation.