Pollution Blankets India's Bihar State, Satellite Shows

CHAMPAIGN, Illinois, January 31, 2005 (ENS) - An enormous pool of pollution hangs over the northern Indian state of Bihar in winter, according to American scientists studying NASA satellite data. Affecting around 100 million people, most in the Ganges Valley, the pollution levels are about five times greater than those found over Los Angeles.

The discovery was made by researchers analyzing four years of data collected by the Multi-angle Imaging Spectro-Radiometer (MISR) onboard the Terra satellite. Launched into orbit on December 18, 1999, Terra is the flagship of NASA's Earth Observing System Program.

"This study is the most comprehensive and detailed examination of industrial, smoke and other air pollution particles over the Indian subcontinent to date, and reveals how topography, meteorology and human activity help determine where these particles are concentrated," said Larry Di Girolamo, a professor of atmospheric sciences at the University of Illinois at Urbana-Champaign and a co-investigator on the MISR mission.


Ropeway to the Vishwa Shanti Stupa, a holy site located on a hill. Hazy air pollution can be seen in the distance. (Photo courtesy Bihar State Tourism Development Corporation (BSTDC) )
High pollution levels were found over much of India, and a concentrated pool of particles was discovered over Bihar, a rural area with a high population density.

The inefficient burning of a variety of biofuels during cooking and other domestic use emits particles in the smoke that remain close to the ground, trapped by valley walls, and unable to mix upward because of a high pressure system that dominates the region during winter.

"The result is a pollution episode that can affect both human health and local climate," Di Girolamo said. "The airborne particles can damage delicate lung tissue, and by altering the radiative heating profile of the atmosphere, the particles may change temperature and precipitation patterns."

Prior to the MISR study, atmospheric models had predicted a tongue of pollution extending across the middle of India. The MISR observations, however, show the pollution lies much farther north.

"MISR is the first instrument to make high resolution, multi-angle radiometric measurements of Earth from space," Di Girolamo said. "By measuring reflected sunlight at nine angles, we can accurately determine the amount of particulate matter, including that generated from man-made pollution, in the atmosphere."

"These models are very important to us, as they are used to forecast pollution episodes and climate change," he said. "The fact that model results don't match the MISR observations suggests there are problems in the models or the model inputs that need to be fixed."

The role of airborne particles remains one of the largest uncertainties in atmospheric modeling. In addition to modifying local climate, the particles can interact with clouds and change the cloud properties.


Temple at Bodhgaya, Bihar, the site of the Buddha's enlightenment. (Photo courtesy BSTDC)
This is important, since clouds have the greatest radiative forcing on the climate system. Radiative forcing is the change in the balance between radiation coming into the atmosphere and radiation going out.

The state of Bihar lies along the eastern plains in northern India. The River Ganges flows across the state, which borders Nepal in the north and is the location of some of the holiest shrines in the world.

Bihar has been a great religious center for Jains, Hindus and Buddhists. In the village of Bodhgaya, Prince Siddharth attained enlightenment and became The Buddha. Sacred caves and monasteries of many traditions dot the landscape.

On hill crests around Rajgir, far in the distances one can see about 26 Jain temples.

"The Bihar pollution pool must be having a tremendous impact on the local climate and the health of the approximately 100 million people that reside within this pool." Di Girolamo said. "Our long-term goal is to better predict the occurrence of these pollution episodes and their impact on public health and local climate."

The satellite data analysis, funded by NASA, involved collaborators from Illinois, the NASA Jet Propulsion Laboratory in Pasedena, California; the National Center for Atmospheric Research, and Scripps Institution of Oceanography. The researchers published their findings in the December issue of the journal "Geophysical Research Letters."