Intriguing aspects of Asian Summer Monsoon Anticyclone Ozone variability from Microwave Limb Sounder measurements

Abstract

Using the long-term (2005–2019) observations from the Microwave Limb Sounder (MLS) onboard Aqua satellite, the present study delineates the variability of the lower stratospheric ozone (LSO) in the Asian Summer Monsoon Anticyclone (ASMA) region. The climatological features of LSO indicate a peak minimum in the southern flank of ASMA noticed by the geopotential measurements from MLS. Further, the temporal variability of LSO indicates significant interannual variability during the 15 years of MLS observations. Our analysis found that two prominent source regions control the LSO variability at interannual time scales in the ASMA region, associated with the Pacific and Indian Ocean sea surface temperatures. More importantly, the extreme (positive/negative) values in ozone anomalies coincide with the El Niño–Southern Oscillation(El Niño/La Niña) events. Further, the composite analysis reveals a significant change in the mean magnitude of LSO of about 10 ppb between El Niño and La Niña phases. The results indicate that reduced water vapor transport due to subsidence and suppressed convection during the El Niño phase leads to less mixing across the upper troposphere and lower stratosphere, therefore, causing higher concentrations of ozone and vice-versa during the La Niña phase. Hence, this study indicates a strong implication for the climatic perturbations over the ASMA region.