Role of deep convection on the spatial asymmetry of the UTLS aerosols in the Asian summer monsoon anticyclone region

Abstract

In this study, we described the spatial asymmetry of the Asian Summer Monsoon Anticyclone (ASMA) circulation using Geopotential Height (GPH) values and divided ASMA into North-West (NW: 32.5°–37.5° N, 40°-70°E), North-East (NE: 32.5°–37.5° N, 70°-100°E), South-West (SW: 27.5°–32.5° N, 40°-70°E) and South-East (SE: 27.5°–32.5° N, 70°-100°E) regions. We provided the spatial asymmetry in the aerosol distribution using the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) (2006–2020) measurements. The vertical distribution of aerosols has been investigated over these regions dividing the atmosphere into (1) Boundary Layer-BL (0–1.5 km), (2) Mid-Troposphere-MT (∼1.5–8 km) and (3) Upper Troposphere and Lower Stratosphere -UTLS (∼8–18 km). Highest aerosol extinction values are noticed in the MT and their contribution to the total Aerosol Optical Depth (AOD) is highest (∼50–80%). The contribution of UTLS aerosols to the total AOD is ∼10% particularly in the eastern part (NE/SE) of the ASMA. The enhancement of aerosols throughout the upper troposphere over the eastern regions (SE/NE) of ASMA, indicates the possible transport of boundary layer pollutants to the UTLS. Using cloud fraction measurements from CloudSat and Pressure vertical velocity (ω), we identified that the intense convection over Bay of Bengal (BoB) is responsible for the UTLS aerosols over the SE region of ASMA. The descending limb of the monsoon-induced circulation over the western region of ASMA (Arabian Peninsula and other Middle Eastern countries) is the possible causative mechanism for the removal of aerosols in the upper troposphere. These findings on the spatial asymmetry in the aerosol distribution over the ASMA are expected to provide the importance of the regional radiative forcing and their climatic impacts.