Spatial, Trend, and Wavelet Analysis of AOD Over Bangladesh

Abstract With the rapid increase in urbanization and industrialization environmental degradation is one of the major issues of developing countries. During the last couple of years, Bangladesh has faced the poorest air quality due to this urbanization. Therefore, in this study, we used Moderate Resolution Imaging Spectroradiometer (MODIS) and Multi-angle Imaging Spectro Radiometer (MISR) retrieved Aerosol optical depth (AOD) data to investigate the spatial–temporal distribution, trend analysis, and the periodic nature of AOD over Bangladesh during the monsoon season from 2003 to 2016. Moreover, we used the Mann–Kendall test and Sen’s slope to analyze the trend analysis of aerosol during monsoon season. We also used wavelet coherence analysis (CWT) and Continuous wavelet transform (CWT) function to observe the periodic correlation of AOD with different meteorological parameters i.e., evapotranspiration, latent heat flux, precipitation, relative humidity, wind speed, and surface air temperature. The average MODIS and MISR retrieved AOD showed an increasing trend in the western regions of Bangladesh with an average value ranging from 0.27 to 0.92 and 0.13 to 0.59 respectively. AOD showed minimum values in Chittagong divisions and tends to increase towards the western region of Bangladesh. Furthermore, we observe the insignificant AOD trend during monsoon season due to high precipitation levels during June and July that washout the aerosol. Moreover, the annual variability of average AOD showed the maximum concentration of aerosols in 2008 and while minimum during 2015. Furthermore, CWT of MODIS retrieved AOD and MISR retrieved AOD shows a strong periodicity (> 0.9) during the 2nd to 4th period. MODIS AOD and MISR AOD also show a series of leading, lagging, in-phase, and anti-phase situations for all years 2003–2016, having a strong cross-wavelet transform (XWT) power ranging from 0.0 to 1. Different techniques, such as afforestation, efficient fuel usage, the development of public transport networks, etc., would be employed in light of the study’s findings to lower the concentration of particle pollution.