Boundary Layer, Urban Meteorology and Land-Surface Processes

Urban effects on precipitation: a literature review and climatology study for Dallas-Fort Worth

Jinxin Wang
OU School of Meteorology

11 April 2014, 2:00 PM

National Weather Center, Room 5600
120 David L. Boren Blvd.
University of Oklahoma
Norman, OK

Precipitation is a key link in the global water cycle and a proxy for a changing climate. World-wide rapid growth of urban areas was shown to have significant impacts on precipitation. Five potential factors which can affect precipitation around/within urban areas: (1) enhanced convergence due to increased surface roughness in the urban environment; (2) enhanced sensible heat fluxes; (3) destabilization due to thermal perturbation of the boundary layer by urban heat islands (UHIs) and resulting downstream translation of the UHI circulation or UHI-generated convective clouds; (4) enhanced aerosols in the urban environment serving as cloud condensation nuclei; (5) bifurcation or diversion of precipitating systems by the urban canopy or related processes.
In our climatology study of precipitation around/within Dallas-Fort Worth based on 11yrs of stage-IV data, a maximum of daily-averaged rainfall is observed to the southeast of DFW. The positive precipitation anomaly is particular obvious in the warm-season of 2009. When the data are classified based on area-averaged surface wind directions into 4 sectors, the composite analysis of warm-season precipitation shows that a positive rainfall anomaly around/within Dallas exists for southeasterly, northeasterly, and southwesterly winds.

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