Analysis of Tropospheric Nitrogen Dioxide Using Satellite and Ground Based Data over Northern Thailand

Abstract

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.