Tropospheric ozone variability over the Indian coastline and adjacent land and sea

Abstract

A tropospheric ozone variability study is carried out to investigate the spatial and temporal distribution over the coastline of the Indian peninsula and adjacent land and sea using NASA Langley Tropospheric Ozone Residual data set for the period 1979–2005. A strong seasonal cycle has been observed with large variation (∼ 55%) over the upper eastern coast, followed by the upper and lower western coast, compared to the lower eastern coast (∼ 33%). A negative gradient in ozone concentration is observed along eastern and western coasts during summer (slope ∼ –0.78 and –0.65) and a positive gradient (slope ∼ 0.16 and 0.21) during winter. The same is observed over the adjacent land and sea along the coastline with slight variation. This change in gradient can be attributed to the anthropogenic emission of precursor gases that reinforce localized photochemical production of ozone. In addition, topography, transport, seasonality of emission of precursor gases and the solar insolation cycle play a vital role.

Acknowledgements

The authors are thankful to the Director, NPL and Director, IITM for their encouragement during the progress of the work. Thanks are also due to http://asd-www.larc.nasa.gov/TOR/data/ for receiving TOR data, http://www.cdc.noaa.gov/ for NCEP Reanalysis Derived data, http://www.meteo.infospace.ru/ for meteorological data and US Naval Observatory, Astronomical Application for daylight hour data, respectively. Thanks are also due for the financial support under CSIR emeritus scientist scheme (SLJ and PKD) and CSIR fellowship (PSK). One of the authors (PSK) is also thankful to Geophysics Centre of the University of Evora (CGE-UE) for the fellowship in the project ‘SPATRAM-MIGE Polar Project’, funded by the Portuguese Science Foundation (FCT).