Linking air quality to Air-Sea interaction based on Space Observations and a global Chemistry-Transport Model

Linking air quality to Air-Sea interaction based on Space Observations and a global Chemistry-Transport Model

This study presents a hypothesized link between air quality over the most populated regions of south Asia and ENSO induced changes in the Walker circulation through impacts on NOx induced tropospheric O3. Changes linked to regional dynamics and photochemistry are analyzed using long-term proxy satellite observations from TOMS (1979-2000, NASA) and GOME (1996-2000, ESA) as well as global chemistry-meteorology model simulations. This study has noted an enhanced tropospheric O3 over the Indo-Gangetic plain during summer which exhibits interannual variations related to contrasting ENSO years. ENSO impacts are broadly related to local emissions such as biomass burning, lightning, stratospheric intrusion as well as ENSO-induced enhancement in transport and model sensitivity to external emissions. Decadal variability of tropospheric O3 anomalies from TOMS-climatology over this region shows high spatial correlation with the anomalies in the velocity potential, which indicates the influence of ENSO dynamics on regional air quality.

Enhanced O3 abundance over this region during summer is the manifestation of the combined effect of enhanced local emissions during this period which is of varying strength depending up on the initial phase of Indian summer monsoon rainfall (ISMR) and also the ENSO induced external impact by transport of pollutants from biomass burning emissions mainly from SE Asia by convective updraft which are subsequently trapped over India within the upper tropospheric anticyclonic circulation.