Temporal and spatial variability of tropospheric NO2 columns retrieved from OMI satellite data and comparison with ground based information in Thailand

Abstract

Eight-year’s of satellite data were retrieved from the OMI satellite to investigate temporal and spatial variability of tropospheric NO2 columns during 2008-2015 over 6 regions of Thailand. The highest level of NO2 columns was observed in the central region followed by the eastern, northern, northeastern, and southern regions. Moderately increasing trends of NO2 columns were detected ranging from 16.62% to 39.48% over 7 years (ref. year 2008). In the north and northeast, the maximum levels of NO2 columns were revealed during the biomass burning period of January-April. In the central and eastern regions, the maximum levels were observed during wintertime, i.e., November-February. For the southern region, the west coast showed higher levels during November-April while the east coast showed elevated levels during May-October. Comparative analysis of seasonal patterns of OMI observations versus ground based information of NO2 concentrations and emissions revealed that they were generally in good agreement, particularly in the northern, eastern, and central regions. The results show that relative humidity has an effect on the correlations between OMI data and emissions. Overall, the OMI observations were shown to be useful in tracking atmospheric levels and emission sources of NO2, especially when ground based data are not available.