Analysis of Tropospheric Nitrogen Dioxide Using Satellite and Ground Based Data over Northern Thailand
Tropospheric NO2 columns over northern Thailand were analyzed using satellite products of the SCIMACHY, OMI, GOME-2A, and GOME-2B sensors for the 14-year period 2003–2016. The comparative results of the four pairs of different satellite datasets within overlapped years showed that they were well correlated with correlation coefficients (r) ranging from 0.82 to 0.88. The r-values improved to 0.85–0.90 when the analysis was considered only during the dry period (October to April). Ground in situ measurements of NO2 concentrations were also obtained for comparative analysis with the satellite NO2 columns. The results revealed relatively good agreement between these two parameters for a seasonal pattern. High levels of NO2 were detected by both satellite and ground monitoring during January–April with the maximum levels in March. Moreover, during this period, most satellite and ground datasets recorded greater levels of NO2 in the afternoon corresponding with the number of fire hotspots collected from the MODIS-Terra and -Aqua satellites. Satellite and ground measurements show slightly increasing annual trends of NO2 levels for 2010–2016 with values of 8.40 and 1.18 %, respectively, over the 6-year period.
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