AOD trends over megacities based on space monitoring using MODIS and MISR(11 page pdf, Pinhas Alpert, Olga Shvainshtein, and Pavel Kishcha, American Journal of Climate Change, Nov. 2012)
Also discussed here: Tracking Pollution from Outer Space: Team Uses NASA Satellites to Measure Pollution Hovering Over World's Megacities(ScienceDaily, Nov. 27, 2012)
Today we review research that used three different satellite sensors to estimate atmospheric optical depth for 189 large cities world-wide over an eight year period. One big advantage of this method is that it gets away from the sometimes non standard or inconsistent pollution monitors on the earth’s surface. Another is that trends in air quality in various cities can be measured and compared using the saem equipment. While cities in Southeast Asia and Northeast USA show an improvement, the Indian subcontinent, the Middle East and Northern China show deteriorating air quality. This approach looks very promising for future monitoring on a global basis.
“Using eight years' worth of data collected by the satellites [MODIS-Terra, MODIS-Aqua, and MISR], the researchers tracked pollution trends for 189 megacities -- metropolitan hotspots where the population exceeds 2 million”
“Unlike ground-based measurements, satellite remote sensing of aerosols has the advantage of providing global coverage on a regular basis . This provides us with an opportunity to compare aerosol tendencies in different megacities using satellite data of the same sensors”
"By merging the data from three imperfect sensors, their flaws are mostly counterbalanced. In cases where the three sensors show differing signs of pollution levels, more research is required."
“The increasing AOD trends over the largest cities in the Indian subcontinent, the Middle East, and North China can be clearly seen. By contrast, megacities in Europe, the north-east of US, and South-East Asia show mainly declining AOD trends”
“Space monitoring of aerosol optical depth trends over megacities can serve as a potential space indicator of global anthropogenic air-pollution changes”