It's now commonly admitted that our appetite for fossil fuels is having a strong influence on the Earth's climate -- and our future. But what about the concentration of humans in urban areas? Today, 50% of the world's population is living on about one percent of Earth's surface. Can this extreme concentration lead to other effects on our climate and weather? In 'Satellites and the city,' NASA says that it can help to provide an answer. "Our research suggests that, using satellite data and enhanced models, we will be able to answer several critical questions about how urbanization may impact climate change 10, 25 or even 100 years from now," says for example a NASA scientist from the Goddard Space Flight Center. But read more...
"More and more people live in cities. This means that cities will grow rapidly over the next several decades. Evidence continues to mount that cities affect the climate," said J. Marshall Shepherd, Deputy Project Scientist of the Global Precipitation Measurement Mission at NASA's Goddard Space Flight Center, Greenbelt, Md.
Shepherd and co-author Menglin Jin, a research scientist at the University of Maryland-College Park, suggest that satellite-observed urban information is extremely useful for advancing our ability to simulate urban effects in climate models. They go on further to propose that satellite data is the only feasible way to represent the expanse of global urban surfaces and related changes to the Earth's surface, vegetation and aerosols.
Below are some images taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite (Credit for images and legends: NASA).
This shows the MODIS land cover classification in southeastern US (near Atlanta). Red color is for Urban Land Build-up (Copied from Jin and Shepherd 2005 with original image source from Michael King).
[And here you can see] the global distribution of fine aerosol optical thickness derived from MODIS measurements on the Terra platform for September 2000. The large values over Southeast Asia, India, Europe, and the United States reflect urban pollution. The large values in the Southern Hemisphere are due to biomass burning.
The two scientists think that urban landscapes are changing the physical processes of land surfaces, such as thermal conductivity, and also adding new characteristics to our land and our atmosphere.
Structures like the Empire State Building in New York City can change the basic wind flow in and around cities that can alter air quality, temperature, cloud distribution and precipitation patterns. It is increasingly evident that such atmospheric changes near cities can be captured by NASA satellites such as Aqua, Landsat, Terra, and the Tropical Rainfall Measurement Mission (TRMM).
This research work has been published by the Bulletin of the American Meteorological Society in May 2005 (Vol. 86, No. 5, pp. 681–689). Strangely, no abstract is available, but here is a link to the full paper named "Inclusion of Urban Landscape in a Climate Model: How Can Satellite Data Help?" (PDF format, 9 pages, 701 KB).
For more recent references about this subject, you also should read "Urban Climate Modeling," published by NASA on April 27, 2005.
Finally, I want to add one more paper to your reading list. Its title is "Urban aerosols and their variations with clouds and rainfall: A case study for New York and Houston" and here is a link to the full paper (PDF format, 12 pages, 701 KB).
I've worked with many meteorologists during my life, but I'm not sure if they're ready to include these minuscule urban lands into their climate models. Any thoughts?
Sources: NASA/Goddard Space Flight Center news release, via EurekAlert!, July 21, 2005; and various web sites
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