"The Indo-Gangetic Plains covering northern India, Pakistan, Nepal and Bangladesh is subjected to dense haze/fog during winter months severely impacting on air, rail and vehicular traffic," Ritesh Gautam, assistant professor at the IIT's Centres for Resources Engineering and Climate Studies, told IANS in an email.
"We have developed this system for monitoring and dissemination of fog information to government agencies and also to the general public."
Formerly a research scientist at the Climate and Radiation Laboratory of NASA's Goddard Space Flight Centre in the US, Gautam said the fog monitoring system was developed with the help of his students Reema Chourey, Dinesh Patil, Sarwar Rizvi and Manoj Singh.
According to Gautam, the system uses in-house developed software to automatically process data from the NASA satellites (Terra and Aqua MODIS) and produces daily maps of fog and low cloud regions for the Indo-Gangetic Plains at a moderately high resolution.
He said his team was presently testing retrievals and processing of fog-related parameters from geostationary satellites, such as India's own INSAT satellites, "for near-real time continuous monitoring of fog, water vapor and aerosols over south Asia".
"This satellite monitoring system is quite complex but I am glad that we have developed the capability and are moving forward," Gautam said. "It can also be used to monitor dust storms, biomass burning events, cyclones and monsoon clouds."
In addition to datasets obtained from both polar orbiting and geostationary satellites, the IIT team is also working on integrating surface-based meteorological and pollution related measurements, he said.
According to Gautam, his team has also analyzed spatial and temporal variation and trends of fog occurrence frequency over the entire Indo-Gangetic Plains along with trends in pollution for the winter season (December-January).
"We have found a highly interesting trend where the long-term satellite data analysis suggests a statistically-significant increasing fog frequency trend over the eastern parts of the Gangetic Plains (parts of Bihar and West Bengal)," Gautam said.
"This is in sharp contrast over the western regions of the Gangetic Plains (such as Delhi), where a decreasing trend in fog frequency is found."
The upward trend in fogginess over eastern Indo-Gangetic Plains is found to be strongly coincident with upward trend in pollution, suggesting that increasing winter-time pollution over this region could be linked to increasing fogginess.
While the focus of media is mostly centered over Delhi, Gautam said the increasing fog over eastern Indo-Gangetic Plains was not usually reported.
However, long term analysis of satellite data by the IIT team has found that "most of northern India is subjected to severe and persistent fog and pollution haze events during the winter months".
(K.S. Jayaraman can be contacted at killugudi@hotmail.com)
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