Long-term analysis of post-monsoon pollution events in the Indo-Gangetic Plain using IASI CO satellite measurements (2007-2024)
Résumé
The Indo-Gangetic Plain (IGP) is a vast region located along the Himalayas and extending over eastern Pakistan, Northern India and Bangladesh. This area ranks among the most polluted regions globally due to its high population density supported by the thriving industrial and agricultural sectors. In recent years, the IGP has frequently experienced severe air pollution episodes during the post-monsoon season (October to November), affecting adversely the health of millions of inhabitants. These pollution events coincide with and are caused by the intensive burning of crop residues by local farmers, emitting high levels of carbon monoxide (CO). Additionally, the stable meteorological conditions of the post-monsoon season favor air mass stagnation, facilitating the build-up of CO, from anthropogenic and biomass burning sources, in the region. Using 18 years of IASI (Infrared Atmospheric Sounding Interferometer) measurements from the Metop satellites, we investigate post-monsoon CO pollution events in the IGP over the 2007-2024 period. Fire Radiative Power data from the MODIS instruments aboard the Aqua and Terra satellites, as well as ERA5 reanalysis data, are also used to determine whether CO pollution events are more influenced by the intensity of fire activity or by meteorological conditions. By analyzing several post-monsoon seasons with varying CO levels, we show that extreme CO pollution events in the IGP are primarily driven by abnormally meteorological conditions, such as very weak near surface tropospheric winds.