Topographic Factors in Precipitation Dynamics Affecting Water Resource Engineering in the Contiguous U.S.: Notes from Hydroclimatic Studies

摘要

A detailed temporal and spatial analysis of precipitation data has led to conclude that topographic forcing played an important role in regulating the frequency and distribution of high-intensity precipitations in the contiguous U.S. In this investigation, 129,000 station-year historical precipitation data obtained for 1207 climatic stations were analyzed using wavelet time-frequency techniques. The results show prominent precipitation variability spatially in association with major topographic features in six hydroclimatic provinces and their transitional zones: (1) Western Coast, (2) Ranges and Basins, (3) Great Plains and Midwest, (4) Lower Mississippi - Ohio River valley - New England region, (5) Florida and Southeast coast, and 6) Great Lakes. Each province has its own unique characteristics of precipitation variability.In this paper, the focus is to discuss the role of topographic forcing in precipitation variability and its implications to water resources engineering. Two types of major topographic effects are discussed. One is topographically enhanced precipitation variability in the U.S. southeast and the Gulf states. The second is the large-scale effect of surface water bodies, as shown by the long-term precipitation increase in the Great Lakes hydroclimatic province. These examples highlight the important role of topographic forcing in regional-local precipitation variability, and depict a superposition of the topographic forcing over the synoptic climate dynamics.