Not only did the amount of urban land cover upwind of Norcross increase substantially from the earlier to the later epochs, but regionwide dewpoint temperatures also increased significantly. The most striking increases occurred at Norcross, Georgia, which is ∼30 km northeast of downtown Atlanta Norcross had the third smallest number of heavy-precipitation days during 1953–77, but, during 1978–2002, it had the most heavy-precipitation days. The southern stations experienced significant decreases in precipitation, whereas significant precipitation increases occurred at central/west-central stations. The time period is divided into consecutive epochs (e.g., 1953––2002), and interepochal differences in precipitation totals, heavy-precipitation days, cumulative heavy precipitation, and atmospheric conditions are explored. Using daily summer-season precipitation data at 30 stations from 1953 to 2002, this study explores the possibility of urban effects as causes of spatial anomalies in precipitation in a zone within 180 km of Atlanta, Georgia. Through modification of the planetary boundary layer, urbanization has the potential to have a significant impact on precipitation totals locally. Year is on the x axis, and precipitation (mm) is on the y axis. The dashed vertical lines indicate station relocations. Time series of summer precipitation totals at Norcross. Urban land cover was determined from 19 land cover classifications. Southwesterly flow is defined as 850-hPa winds having wind directions between 135° and 315°. 2 but showing changes in z scores between 1962––93.įrequencies of heavy-precipitation days during predominantly southwesterly flow at stations within and near the Atlanta metropolitan area. The z scores were calculated separately for each epoch using the mean and std dev of the 30 stations.Īs in Fig. Numbers denote the precipitation stations station names and associated information are available in Table 1.Ĭhanges in z scores between 1953––2002 for all precipitation (AP), heavy-precipitation days (HPD), and cumulative heavy precipitation (CHP). Map of the study region showing locations of the 30 precipitation stations and the boundary of the Atlanta metropolitan area.
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