Abstract
This paper presents the results of measurements of the surface ozone (O3), oxides of nitrogen (NOx), methane (CH4) and total non-methane hydrocarbons (TNMHCs) in a rural coastal location at Kannur (11.9°N, 75.4°E, 5 m asl), India from November 2009 to December 2011. The diurnal cycle for surface O3 had a peak in the afternoon and declined during nighttime. The maximum and minimum mixing ratio of surface O3 was observed in winter and monsoon seasons respectively. NOx concentration was high during mid-night to early morning and low during noontime. The diurnal variations of mixing ratios for NOx and O3 were anti-correlated. Monthly average maximum (2.26 ± 0.44 ppmv) and minimum (0.43 ± 0.19 ppmv) CH4 concentrations were observed in December and August respectively. The diurnal variations of CH4 were similar to that of NOx. A CH4 buildup was observed during early morning hours throughout the observational period. On an annual basis, the maximum, minimum and average total NMHCs were (25.45 ± 6.58 ppbv), (13.84 ± 4.31 ppbv), and (19.23 ± 5.56 ppbv) respectively at the observational site. Analysis of O3, NO, NO2, CH4 and NMHC have been carried out and the correlation between O3 and its precursors is discussed detailed. Further, the diurnal variation of O3 over a free tropospheric region at Ooty, a hill station lying in the Western Ghats region of south India on clear sky days in February 2011 is also reported for a comparison.
Highlights
The concentrations of trace gases are low in the atmosphere, but they play a vital role in determining the ambient air quality over a location
This paper presents the results of measurements of the surface ozone (O3), oxides of nitrogen (NOx), methane (CH4) and total non-methane hydrocarbons (TNMHCs) in a rural coastal location at Kannur (11.9°N, 75.4°E, 5 m asl), India from November 2009 to December 2011
This study presents an account of the variability of surface O3 and its prominent precursor nitrogen oxides (NOx) in the wake of measured concentrations of methane and total non-methane hydrocarbons at this site
Summary
The concentrations of trace gases are low in the atmosphere, but they play a vital role in determining the ambient air quality over a location. Measurements of surface O3, NOx and meteorological parameters at Kannur, another coastal city in south India by Nishanth et al (2012b) reported that O3 and NOx showed distinct diurnal and seasonal variabilities. This study presents an account of the variability of surface O3 and its prominent precursor NOx in the wake of measured concentrations of methane and total non-methane hydrocarbons at this site. In Kannur, the four major seasons are winter (December–February), summer (March–May), monsoon (June–August) and post-monsoon (September–November) The meteorological parameters such as wind speed, relative humidity, temperature and total rainfall experienced in the observational site were retrieved from the local automatic weather station operated by the Meteorological and Oceanographic Satellite Data Archival Centre (MOSDAC), established by the Indian Space Research Organization (ISRO).
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