Spatio-temporal analysis of formaldehyde and its association with atmospheric and environmental variables over the Southeast Asian region using satellite data.

This study investigates the spatio-temporal distribution of formaldehyde (HCHO) over the mainland Southeast Asian region (including Northeast India) from 2019 to 2022 using TROPOMI satellite data. HCHO is a key atmospheric trace gas which is influenced by both natural processes and anthropogenic activities. We analyze HCHO levels in relation to atmospheric species including carbon monoxide (CO), nitrogen dioxide (NO), and environmental factors such as land surface temperature (LST), precipitation (PPT), fire radiative power (FRP), and enhanced vegetation index (EVI). Peak levels of HCHO are particularly observed in March and April, which coincide with the dry and warm seasons and reflect seasonal variability arising from both fluctuating emission sources and regional climate patterns. Correlation analyses reveal significant associations between HCHO and CO (r = 0.727), followed by HCHO and NO (r = 0.577) and HCHO and LST (r = 0.539). Conversely, a negative correlation with PPT (r =  - 0.233) is observed as HCHO decreases with increased precipitation due to washout. The negative correlation with EVI (r =  - 0.319) is unexpected since biogenic emissions are significant contributors to HCHO. This outcome likely results from the confounding effect of precipitation. A robust multiple regression model incorporating these variables is developed which is able to explain 61.8% of the variance in HCHO. It enhances predictive capabilities facilitating the estimation of HCHO distribution and supporting air quality management efforts in the region. This research contributes to understanding the complex interactions of HCHO with atmospheric chemistry and climate variability in Southeast Asia. Insights gained from this study are crucial for informing environmental policies aimed at reducing air pollution and protecting public health in rapidly developing regions.