File:Cloud Bank Along the Himalayan Mountains (MODIS 2019-12-24).jpg

English: On December 23, 2019, the India Meteorological Department warned that severe cold and very dense morning fog would be likely over several northern states for the next two to three days. Punjab, Haryana, Chandigarh and Delhi are areas under the advisory although fog and cold may affect other locations for shorter times.

The Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA’s Terra satellite acquired a true-color image of a broad bank of morning fog and haze hanging over the Indo-Gangetic Plain and butting up against the foothills of the Himalayan Mountains on December 23. Most overnight fog burns off fairly quickly in the mornings, but cool temperatures can slow the dissipation.

The haze, largely created by smoke from heating fires, industrial aerosols, and vehicle emissions, appear grayer in color than the bright white fog. Fog and aerosol hazes likely amplify each other. On one hand, aerosol particles serve as “seeds” that make it easier for fog and clouds to form. On the other, fog droplets accelerate the conversion of gaseous pollutants into haze-causing aerosols. Damp conditions also amplify haze because high humidity increases the size of many aerosols, making them more likely to block light.