File:Fires and Smoke in India (MODIS 2021-12-26).jpg

English: A river of thick gray haze hung over the Indo-Gangetic Plain along the southern edge of the Himalaya Mountains in late December 2021. The Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA’s Aqua satellite acquired this true-color image on December 23. The band of gray stretches across northern India and bends southward both in the west and east to hang over the Bay of Bengal (east) and the Arabian Sea (west). Haze is a common occurrence over India, especially when farmers use fire to clear fields of stubble at the end of the growing season. While the majority of agricultural fires burn through the end of November, some fires continue into December and are probably part of the source of this gray haze. Urban and industrial pollution also contribute to haze through much of the year, and this tends to increase in winter as fuels are increasingly used for heating. Winter also is the time when temperature inversions frequently occur, creating conditions for heavy haze formation. This happens when cool air near the ground becomes capped by a layer of warm air above. The warm air acts like a lid, preventing cool air from rising. Any particulate matter that sits within the cooler layer stays trapped near the ground, allowing for increasing haze the longer the inversion is present.