1 7.5 LINKING AIR QUALITY TO AIR-SEA INTERACTION BASED ON SPACE OBSERVATIONS AND A GLOBAL CHEMISTRY-METEOROLOGY MODEL T. Kunhikrishnan 1 , James H Crawford 1 , Jack Fishman 1 , Mark G Lawrence 2 , Andreas Richter 3 , John P Burrows 3 1 Atmospheric Science Directorate, NASA Langley Research Center, Hampton, USA 2 Department of Atmospheric chemistry, Max Planck Institute, Mainz, Germany 3 Institute of Environmental Physics and Remote Sensing, University of Bremen, Germany 1. INTRODUCTION Urbanization and increasing demand of energy needs have resulted in a deterioration of air quality over Asia. North India covering the Indo-Gangatic plain (Figure 1) is the most populated region in south Asia. Observations from satellites have shown that extensive pollution exist in this region because of local anthropogenic emissions where combustion of both bio-fuels and fossil fuels are widespread, also natural emissions such as lightning and biomass burning in summer. During the last decade, the Indian Ocean Experiment (INDOEX) has made both meteorological and atmospheric chemistry measurements with the results indicating that there may be considerable impacts on regional climate (Ramanathan et al., 2005). The analyses of Fishman et al (2003, 2005) have likewise confirmed that regional enhancements of tropospheric O 3 over northern India are readily identified from long term observations using total ozone mapping spectrometer (TOMS)-climatology. The present study is aimed at further extending these conclusions by focusing on the regional dynamics controlling NO x induced tropospheric O 3 over north India based on long term proxy satellite observations and a global model simulations. The chemical composition of the atmosphere over south Asia is driven by the monsoon meteorology. As the Asian monsoon is driven by the differential heating of Ocean and adjacent land masses, its ―――――――――――――――――――――――― Corresponding author: T. Kunhikrishnan, Atmospheric Sciences, NASA Langley Research Center, Mail stop 483, Hampton, VA, 23681-2199. Email: k.thengumthara@larc.nasa.gov Figure 1 Schematic sketch of north India covering Indo-Gangatic plain of south Asia (enclosed by dashed line, including oceanic region) variability is mainly linked to land-ocean thermal contrast and changes in the position of convective zones. ENSO phenomenon is the prominent climate variability related to air-sea interaction. The regional chemistry is mostly influenced by synoptic meteorological features such as large scale transport and convective mixing depending on the chemical lifetime of species and the emission strength. There is no distinct dynamic link established between the interannual variation of tropospheric O 3 and ENSO related drought conditions over south Asia. ENSO influences on air pollution are associated with shifts in the convective patterns and precipitation regimes, resulting severe drought over western pacific and reduced summer monsoon rainfall over India. ENSO conditions possibly delays the onset of monsoon as well as increase in the length of non-rainy days in India (Gosawmi and Xavier, 2005). This condition leads to widespread biomass burning and enhanced emissions of hydrocarbons and NO x. Studies based on Fishman et al (2005), Thompson et al (2001), Ziemke and Chandra (2001), have related the