Speaker
Description
The combined effect of El Niño-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD)on the tropical Upper Troposphere Lower Stratosphere (UTLS) ozone is examined using the data from Microwave Limb Sounder (MLS) onboard Aura Satellite and ECMWF (European Centre for Medium-Range Weather Forecasts) ERA5 reanalysis. During the years of positive (negative) ENSO and IOD events, UTLS ozone mixing ratio shows a decrease (increase) in the absolute values. We also analyse the Quasi-Biennial Oscillation (QBO) which shows an in-phase variation with the ozone anomaly. The calculated eddy heat flux (used as a proxy for Brewer-Dobson Circulation, also known as BDC) corroborates the positive (negative) ozone anomaly by the high tropical downwelling (upwelling). To quantify the contributions of ENSO,IOD, and QBO –in the observed ozone anomaly, multivariate linear regression (MLR) analysis is performed using the least square method. It shows that one fourth of the observed ozone variation during the period of study (2005-2020) can be attributed to ENSO, IOD, and QBO altogether. This preliminary study suggests that large scale climate drivers from the Pacific and the Indian ocean should be considered while examining the UTLS ozone distribution.
