KOLKATA, India, Jan. 6 (UPI) -- A new image from NASA's Earth Observatory mission shows what happens when widespread pollution meets a temperature inversion.
Currently, a massive blanket of haze hangs over the Indo-Gangetic Plain. The smog is a the result of industrial pollution and urban exhaust, as well as agricultural, cooking and trash fires. Skies in northern India and Bangladesh are darker than usual as the haze shields the sun.
NASA's Terra satellite and its Moderate Resolution Imaging Spectroradiometer, or MODIS camera, imaged the phenomenon as it orbited over the subcontinent on Sunday.
Normally, pollution is allowed to disperse and dissipate as warm air rises and weather systems stir up the lower atmosphere. In the winter, however, temperature inversions sometimes trap cold air close to the surface -- pinning pollution in place.
"Air pollution has emerged as a significant issue in India," NASA wrote in a news release. "Satellite observations show that levels of both sulfur dioxide and nitrogen dioxide are rising."
The Air Quality Index score -- which quantifies the concentration of particulates in the air -- in Kolkata is currently 514 and rated as "hazardous."
To the east, in India's capital, New Delhi, regulators have decided to keep cars off the roads for two days each week in January to help curb the annual haze and associated health problems.
India's pollution isn't an isolated problem. Cities across Asia are struggling with a rise in suffocating smog. And research shows that pollution can have global implications, fueling storms in the Pacific.