Global Analysis of the Growth of Large Cities, 1999-2009, as Seen With the Seawinds Scatterometer and DMSP/OLS Nighttime Lights
Over half of the world’s population now live in cities, and dynamics in urban areas are increasingly recognized as a poorly understood element of global change science. Remote sensing is widely used to monitor urban extent and dynamics, but characterizing the properties and changes to urban areas at global scales remains a significant challenge. Buildings and other metropolitan/industrial structures are efficient microwave backscattering surfaces, and so urban/industrial construction causes microwave backscatter to increase. We evaluate the 1999-2009 changes in microwave backscatter and in stable nighttime lights from 100 large cities on all six inhabited continents. The SeaWinds Quikscat Ku-band active microwave scatterometer collected data from June 1999 - Nov 2009, and processed and distributed by the NASA Scatterometer Climate Record Pathfinder project (www.scp.byu.edu/). Stable nighttime lights data were collected with the Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS), and distributed by the NOAA National Geophysical Data Center (www.ngdc.noaa.gov/dmsp/download.html). A series of DMSP/OLS sensors have flown since 1992; the instruments acquired 6-bit data (data range 0-63). We compare the 10-year change in nighttime lights to the 10-year change in microwave backscatter for c.50-km x 50-km regions centered on the 100 cities (~100 non-water, 0.05° grid cells per city). Figure shows black arrows for 1999 -> 2009 change in each grid cell for San Francisco and Shanghai; red arrows are mean change. At our analysis resolution of ~5 km, in 1999 about 19% of these grid cells were at or near saturation in nighttime lights (value ≥ 62); by 2009 this increased to about 24%. In 1999, about 19% of grid cells had a backscatter > -9 dB; by 2009, this increased to about 40%. These two complementary data records of urban growth are neither fully correlated nor completely orthogonal. We also compare these data to China provincial data on annual residential building floor area.
Earth Sciences, Earth Systems Research Center
Fall Meeting, American Geophysical Union (AGU)
American Geophysical Union Publications
Frolking, S., Milliman, T., Friedl, M., Hagen, S. and Braswell, B., Global Analysis of the Growth of Large Cities, 1999-2009, as Seen With the Seawinds Scatterometer and DMSP/OLS Nighttime Lights, Abstract GC21E-1008 presented at 2012 Fall Meeting, AGU, San Francisco, Calif., 3-7 Dec.