An Assessment of Anthropogenic Effects on Precipitation in and near the Phoenix, Arizona Metropolitan Area

It has long been hypothesized that urban areas exert a direct influence on precipitation patterns in their immediate surroundings (Horton, 1921). Early studies focused on this influence through the use of point-observation comparisons of urban and rural areas to quantify the anthropogenic effects on precipitation (AEP) (Changnon Jr., 1968, Huff and Changnon Jr., 1973, Huff and Schickedanz, 1974). Most, if not all, early studies suffered from inherent spatial and temporal errors due to the sampling methods used as they were unable to adequately measure convective precipitation (Lowry, 1998). Studies during the 1990s began to utilize higher resolution sampling techniques, which included lightning data (Westcott, 1995), satellite-based radar data (Shepherd et al., 2007), and, ground-based radar data (Mote et al., 2007). Ground-based radar provides the most appropriate data for the study of AEP due to the superior spatial (1° x 1 km) and temporal (approximately five minutes) resolution.