Multi-year satellite observations of tropospheric NO 2 concentrations over the Indian region

Abstract

An assessment of satellite-derived long-term tropospheric nitrogen dioxide (NO 2) data is performed over the Indian region and their implications on the regional air quality are discussed. The Indo-Gangetic plain (IGP) shows an increasing trend in NO 2 of the order of 3×1013mol/cm2/yr. The pixel-wise (0.25 km) trend for the period 2005–2014 reveals various regions having increased rates of pollution over the study period. Further, the mean seasonal concentrations of NO 2 are segregated for different parts of the country including oceanic regions and the trends are brought out. The highest rate of increase of tropospheric NO2(2×1014mol/cm2/yr) is seen around coal mining areas and certain industrial areas such as ports and thermal power stations. Using the data spanning 10 years, the wavelet analysis is carried out to study the influence of semi-annual oscillations (SAO) on trace gas concentrations in different parts of the country. The study reveals that the SAO are stronger in the northern parts of India, including IGP and western India, whereas South India and oceanic regions are having very low SAO component and strong annual oscillation component.