Spatial and Temporal Variations in Tropospheric Carbon Monoxide, Methane, Nitrogen Oxides and Ozone over India
Ozone, Nitrogen Dioxide, Carbon Monoxide and Methane mixing rations have been analysed during the period 2016-2017 over India using data from NASA’s Earth Observing Satellites. Analysis shows large seasonal and spatial variations in these trace gases. The maximum average mixing ratio of ozone, occurring in the month of April, is around 38 ppbv compared to a minimum of around 25 ppbv in August. Mixing ratios of other gases also vary considerably with season, with nitrogen dioxide peaking around December-January, carbon monoxide peaking around March-April and methane peaking around October-November. The southwest monsoons reduce the mixing ratio of every trace gas due to washout. Mixing ratios also are found to vary considerably spatially. Ozone shows much higher mixing ratios at higher latitudes due to photochemical production (in the northern region and ppbv in the southern region). Other trace gases show correlation with presence of densely industrialized and populated regions such as the Gangetic plain. The correlation between carbon monoxide and ozone mixing ratios in the southern region was found to be strong and that in the northern region was found to be weak). The slope of the regression line was found to be 0.233averaged over the whole of India in 2016-2017, and this result is in close agreement to other similar studies carried out over Asia.
Keywords: Atmospheric chemistry, troposphere, ozone, pollution, trace gases