BATAL: The balloon measurement campaigns of the Asian tropopause aerosol layer

Abstract

A series of NASA-ISRO-sponsored balloon campaigns in India and Saudi Arabia, called the Asian tropopause aerosol layer (ATAL) was conducted between 2014 and 2017 to study the nature, formation, and transport of polluted aerosols in the upper troposphere and lower stratosphere during the Asian summer monsoon (ASM). The ATAL was confirmed through solar occultation observations by Stratospheric Aerosol and Gas Experiment (SAGE) II after improving the cloud-aerosol separation approach using the ratio between aerosol extinction coefficients retrieved at two wavelengths. Analysis of long-term satellite measurements of upper troposphere and lower stratosphere (UTLS) aero­sols suggested that ATAL's aerosol optical depth had increased by 2-3 times since the late 1990s, pointing out its possible connection with Asian pollution growth.