The Indian subcontinent is among the most populated and highly polluted regions in the world and emissions are increasing over this region due to rapid economic growth here. These increasing emissions have strong implications not only for the large population residing in this region but it can also reach other parts of the world via long range transport. This region is among the least studied parts of the world and limited observations hampers the better understanding of the changing atmospheric chemistry over the region. This thesis describes results from two field campaigns viz., SusKat and GVAX over the Himalayan region; satellite based study of biomass burning over the Indian subcontinent, and balloon borne measurements of ozone and meteorological parameters over ARIES, Manora Peak. The seasonal and interannual distribution of biomass burning activity (2003-2013) indicated distinct seasonal cycle over this region and show that the fire activity has increased during last five years (2008-2013). Large differences were observed in the budgets of trace species emitted during these fires. The emissions show biannual peaks in spring (Mar-May) and autumn (Sep-Nov) season with higher emissions in the later season. For the first time, a field campaign for the measurement of trace species was conducted in Kathmandu Valley, Nepal during Jan-Jun 2013. The ozone and CO levels at Bode, Nepal in the valley were found to be higher than Pantnagar, India. The regional scale pollution from IGP is suggested to contribute to the higher levels during an event in spring season. For the first time high resolution WRF-Chem model setup was done over the Himalayan region and model is able to capture variations in temperature, RH and winds. Model also showed good agreement in daytime levels of CO however, ozone and NOx were over and underestimated. The long term change in the vertical distribution of ozone was studied using balloon borne measurements at ARIES, Manora Peak. The contribution of spring time biomass burning to the ozone levels in lower troposphere is also estimated. Results obtained using the high frequency balloon-borne measurements of meteorological parameters during Ganga Valley Aerosols experiment (GVAX) at ARIES, Nainital indicated high wind speed (~85 m/s) near the subtropical jet. The observations also showed better agreement of wind speeds at 250 hPa (altitude of subtropical jet) than other levels with reanalysis datasets The Satellite based retrievals indicated negative bias in temperature profiles in the lower altitude region, and positive bias near the tropopause. WRF simulated results are able to capture variations in temperature, humidity and wind speed profile reasonable well. The detailed results will be discussed during the talk.