Detection of surface emission hot spots, trends, and seasonal cycle from satellite-retrieved NO₂ over India

Abstract

Tropospheric NO₂ concentrations derived from spaceborne measurements of Global Ozone Monitoring Experiment (GOME) on board ERS 2 and Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) on board Envisat, respectively, for the time period of 1996-2006 have been used to identify major NO₂ emission hot spots, trends, and seasonal cycle over different regions of India. Emission hot spots are observed over the locations of thermal power plants and over major urban and industrial regions. A multifunctional regression model has been used to analyze the trends and seasonal cycle over these emission hot spots. Increasing trends of ~1.65 ± 0.52% a^-1 have been observed for NO₂ over India. The fast growing industrial regions of Mumbai and Delhi show increasing trends of ~2.1 ± 1.1 and ~2.4 ± 1.2% a^-1, respectively. Seasonal variations of tropospheric NO₂ concentrations show a maximum during winter-summer (December-May) and a minimum during the monsoon seasons (June-September). The observed seasonal cycle in satellite-derived NO₂ agrees well with the surface-level observations of NO_x.