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Data from the Tropical Rainfall Measuring Mission’s (TRMM) Precipitation Radar (PR) were employed to identify warm
season rainfall (1998-2000) patterns around Atlanta, Montgomery, Nashville, San Antonio, Waco, and Dallas. Results reveal
an average increase of -28\% in monthly rainfall rates within 30-60 kilometers downwind of the metropolis with a modest
increase of 5.6\% over the metropolis. Portions of the downwind area exhibit increases as high as 51\%. The percentage
changes are relative to an upwind control area. It was also found that maximum rainfall rates in the downwind impact area
exceeded the mean value in the upwind control area by 48\% - 116\%. The maximum value was generally found at an average
distance of 39 km from the edge of the urban center or 64 km from the center of the city. Results are consistent with
METROMEX studies of St. Louis almost two decades ago and with more recent studies near Atlanta. Future work is extending
the investigation to Phoenix, Arizona, an arid U.S. city, and several international cities like Mexico City, Johannesburg, and
Brasilia. The study establishes the possibility of utilizing satellite-based rainfall estimates for examining rainfall modification
by urban areas on global scales and over longer time periods. Such research has implications for weather forecasting, urban
planning, water resource management, and understanding human impact on the environment and climate.
Author
Rain; Resources Management; Water Resources; Wind Direction
20030032196 NASA Goddard Space Flight Center, Greenbelt, MD, USA
A Comparison of the Lower Stratospheric Age-Spectra Derived from a General Circulation Model and Two Data
Assimilation Systems
Schoeberl, Mark R.; Douglass, Anne R.; Zhu, Zhengxin; Pawson, Steven; [2002]; 2 pp.; In English; AGU 2002 Fall Meeting,
6-10 Dec. 2002, San Francisco, CA, USA; Copyright; Avail: Other Sources; Abstract Only
We use kinematic and diabatic back trajectory calculations, driven by winds from a general circulation model (GCM) and
two different data assimilation systems (DAS), to compute the age spectrum at three latitudes in the lower stratosphere. The
age-spectra are compared to chemical transport model (CTM) calculations, and the mean ages from all of these studies are
compared to observations. The age spectra computed using the GCM winds show a reasonably isolated tropics in good
agreement with observations; however, the age spectra determined from the DAS differ from the GCM spectra. For the DAS
diabatic trajectory calculations there is too much exchange between the tropics and mid-latitudes. The age spectrum is thus
too broad and the tropical mean age is too old as a result of mixing older mid latitude air with tropical air. Likewise the mid
latitude mean age is too young due to the in mixing of tropical air. The DAS kinematic trajectory calculations show excessive
vertical dispersion of parcels in addition to excessive exchange between the tropics and mid latitudes. Because air is moved
rapidly to the troposphere from the vertical dispersion, the age spectrum is shifted toward the young side. The excessive
vertical and meridional dispersion compensate in the kinematic case giving a reasonable tropical mean age. The CTM
calculation of the age spectrum using the DAS winds shows the same vertical and meridional dispersive characteristics of the
kinematic trajectory calculation. These results suggest that the current DAS products will not give realistic trace gas
distributions for long integrations; they also help explain why the extra tropical mean ages determined in a number of previous
DAS driven CTM s are too young compared with observations. Finally, we note trajectory-generated age spectra . show
significant age anomalies correlated with the seasonal cycles. These anomalies can be linked to year-to-year variations in the
tropical heating rate. The anomalies are suppressed in the CTM spectra suggesting that the CTM transport scheme is too
diffusive.
Author
Atmospheric General Circulation Models; Cycles; Computation; Latitude; Stratosphere; Spectra; Trace Contaminants
20030032234 NASA Goddard Space Flight Center, Greenbelt, MD, USA
Visions of our Planet’s Atmosphere, Land & Oceans
Hasler, Arthur F.; January 2002; 1 pp.; In English; The 107th STANYS Annual Convention, 3-5 Nov. 2002, Ellenville, NY,
USA; No Copyright; Avail: Other Sources; Abstract Only
The NASA/NOAA Electronic Theater presents Earth science observations and visualizations in a historical perspective.
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