1 Urban Signatures: Sensible Heat Flux Big cities influence the environment around them. For example, urban areas are typically warmer than their surroundings. Cities are strikingly visible in computer models that simulate the Earth's land surface. This visualization shows sensible heat flux predicted by the Land Information System (LIS) for a day in June 2001. (Sensible heat flux refers to transfer of heat from the earth's surface to the air above; for further explanation see http://www.uwsp.edu/geo/faculty/ritter/geog101/textbook/energy/energy_balance.html). Sensible heat flux is higher in the cities--that is, they transfer more heat to the atmosphere--because the surface there is warmer than in the surroundings. Only part of the global computation is shown, focusing on the highly urbanized northeast corridor in the United States, including the cities of Boston, New York, Philadelphia, Baltimore, and Washington. Still Image (1000x1000) This image shows sensible heat flux (watts per square meter) predicted by LIS for 2001/06/11. The warm urban areas have higher positive flux (heat flowing towards the atmosphere) and stand out very distinctly against their surroundings. 1 1 http://svs.gsfc.nasa.gov/vis/a000000/a003100/a003157/cityQh.png 34.5 44.5 -79.7 -69.7 Legend 1 3 http://svs.gsfc.nasa.gov/vis/a000000/a003100/a003157/qh_bar.png