Lingering haze continued over south central Asia in late January, 2011, shrouding the lowlands south of the Himalayas with a gray veil. The Moderate Imaging Spectroradiometer (MODIS) aboard the Terra satellite acquired this true-color image of the region on January 25, 2011.
Northeast India and Bangladesh are often plagued by pollution in the winter time, when cold, heavy air slides down the southern face of the Himalayas into the lower lands, holding pollution close to the ground. Often the cold air ends up trapped underneath a layer of warmer air, resulting in a temperature inversion, locking pollutants in place. When the inversion lifts, or when spring arrives with increasing temperatures, warm air rises out of the valleys allowing the pollution to disperse more freely.
While winter pollution is a common phenomenon, the Centre for Science and the Environment has noted that not only are this winterís particulate levels extremely high, but so are levels of several toxic chemicals, including nitrogen dioxide and carbon monoxide. Earlier this winter, in December 2010, the Department of Environment (DOE) reported that airborne particulates in the city of Dhaka, Bangladesh, reached nearly five times the acceptable level set by the National Air Quality Standard of Bangladesh.
Dhaka is the capital of Bangladesh, located on the Buriganga River. The city and its metropolitan area have a population of over 12 million, making it one of the major cities in South Asia. It can be seen as a faint gray smudge near the bend of the river, very near the center of the country, but it is difficult to separate it from the overlying gray haze. Bangladesh is the country in the center of the image.
Between October and March each year, when rains are scarce and temperatures drop, the use of sulfur-rich coal, firewood and even used automobile and rickshaw tires are used to warm residents of the region. In addition, there are 5,000 registered brick kilns in Bangladesh alone, almost all of which burn coal and firewood. Vehicle emissions and other human activities also contribute to the air pollution.