An investigation of warm season spatial rainfall variability in Oklahoma City: Possible linkages to urbanization and prevailing wind
Lauren Hand, Univ. of Georgia, Athens, GA ; and M. Shepherd
This study used nine years (1998-2006) of warm-season (June-September) mean daily cumulative rainfall data from both the TRMM multi-satellite precipitation analysis (TMPA) and rain gauge stations to examine spatial variability in warm season rainfall events around Oklahoma City (OKC). It was hypothesized that warm season rainfall variability, under weakly forced conditions, was a function of prevailing wind and urbanization. Results from both satellite and gauge-based analyses revealed that the north-northeastern regions of the metropolitan OKC area were statistically (p-value=0.09) wetter compared to other regions. Climatological sounding and reanalysis data revealed that the N-NE area of OKC was the climatologically downwind region, confirming that precipitation modification by the urban environment may be more dominant than agricultural-topographic influences on weakly forced days. The study also established that satellite precipitation estimates capture spatial rainfall variability as well as traditional ground-based resources. TRMM products slightly underestimate the precipitation recorded by gauges but the correlation improves dramatically when the analysis is restricted to mean daily rainfall estimates from OKC urban grid cells containing multiple gauge stations (R2=0.878). We also quantitatively confirmed, using a relatively new concentration factor analysis, that prevailing wind flow relative to preferred regions of an urban area significantly describe rainfall variability. Overall, the study establishes a prototype methodology for utilizing satellite-based rainfall estimates to examine rainfall modification by urbanization on global scales and in parts of the world not well-instrumented with rain gauge or radar networks.
Joint Session 10, Urban Precipitation Patterns
Monday, 12 January 2009, 1:30 PM-2:30 PM, Room 124B
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