To Detect Aerosols Optical Depth (AOD) Local Hotspot Region: Spatiotemporal Characteristics over Indian Regions

Abstract

India’s geographic and climatic characteristics make it a key region for the description of atmospheric aerosol optical properties around the globe. Spatiotemporal variations of Aerosol’s Optical Depth (AOD) are significant in understanding aerosols’ characteristics. The study’s primary focus is to show the variation of MODIS AOD along with the Dust Column mass density over the selected study regions. MODIS AOD at 550 nm of five major significant regions from India was selected using aerosol products from January 2001 to December 2020. To evaluate the optical properties of aerosols, satellite-based measurements offer greater geographical and temporal coverage due to the dearth of ground observations across the entirety of India, particularly over the Eastern region. The present study also compares dust column mass density obtained from the MERRA-2 database monthly averages for five major regions in India. Results show that the highest annual mean AOD is observed in the eastern Indian region (especially the IGB region), possibly due to air mass from the Thar desert. At the same time, values in other parts of the country are much lower. The eastern Indian region has indeed been identified as a local hot spot for aerosols, significantly affecting the local area’s air quality. Although, from April to August, the AOD levels are much more significant, when dust occurrences are more frequent throughout Southwest India, high AOD over the eastern Indian region is significantly associated with frequent dust outbursts throughout the year. Peak AOD (~ 0.6 to 0.7) values have been observed in other largely urbanized areas between mid-winter and mid-spring as a result of high aerosol emissions from fossil fuel burning coupled with thin atmospheric boundary-layer depths, which result in the development of a rigorous mass of aerosols near the surface. However, the AOD (~ 0.2) least observed from August to November shows a relatively higher value due to the MODIS algorithm not working correctly during the monsoon period. Average AOD over India shows increasing trends in 2016 (~ 1.2) for the eastern region and decreasing trends in 2003 (~ 0.2–0.4) throughout the study period.