The influence of the growth of the Dallas/Fort Worth (DFW) Metroplex on regional precipitation patterns
Nordfelt, Anna Marie
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Due to the effects urbanization has on land-use and land cover change (LULC), urban areas have a major influence on the environment. The strong coupling between the land and atmosphere can alter the microclimatology of cities and their surrounding regions. Previous research has shown that cities can influence regional precipitation patterns. This is a result of many factors such as: increased heating and lifting caused by the urban heat island effect (UHI), increased pollution and aerosols, alteration of land use/land cover (which includes surface albedo, presence or lack of vegetation, and surface roughness changes), and urban design (which leads to increased friction and convergence). This study analyzes temporal and regional changes in the precipitation patterns of the Dallas/Fort Worth Metroplex as it has grown over the past century, and provides a methodology for testing urban influences on precipitation in other metropolitan areas. Precipitation from 1930 ? 2007 was analyzed for the following three study regions: DFW (urban area), CRA (upwind control region), and CRB (downwind control region). By comparing early (1930 ? 1950) and late period (1987 ? 2007) precipitation within each region, it was found that there were no statistically significant differences between the two periods. Entire period precipitation (1930 ? 2007) at CRB was statistically significantly different from both DFW and CRA although early and late period precipitation was not. While precipitation was similar between the two periods in all regions, comparing precipitation between the regions using the entire period shows potential anthropogenic influences. Land cover change between 1976 and 2001 was analyzed and it was found that water in the DFW Metroplex study region increased by 54.75%, vegetation decreased by 20.34%, and urban land cover increased by 176.14%. This may increase atmospheric moisture, surface temperature, friction and lifting over the urban center, and decrease the amount of heat released from the ground. While natural climate variability is the most important factor influencing precipitation in this region, it is possible that urbanization is also changing local and regional precipitation patterns, it may not be the only factor influencing change.