资源环境科技发展态势分析平台

Using daily precipitation records from 151 stations, the Mann-Kendall nonparametric test, and the rotated empirical orthogonal function, this study examined trends in precipitation and precipitation extremes and underlying mechanisms in the U.S. Great Basin during 1951-2013. The results indicate that annual total precipitation, 1 day and 5 day maximum precipitation, extreme precipitation days over the 95th and 99th percentiles trended upward during 1951-2013. Spatially, stations experienced significant positive trends in six indices are mostly distributed in the eastern basin, while those experienced significant negative trends are a few and situated in the western basin. Four distinct modes characterized by different patterns of annual precipitation variations were identified. They are the northeastern, southern, midwestern, and midnorthern modes. In addition, we found that the effects of El Nino-Southern Oscillation and Pacific Decadal Oscillation on precipitation was low in the basin. The intensifying high-pressure system over the western North Pacific in winter and the increasing water vapor and air temperature of the atmosphere over the basin in winter and spring were mainly responsible for the upward trends in six indices during 1951-2013. Nevertheless, the topography regulates the effects of synoptic conditions on precipitation, contributing to the "east-west" contrast in station distribution between those experienced negative and positive trends. Overall, precipitation and precipitation extremes increased significantly in the eastern and northern basin while increases were not significant in the western and southern basin. This information has important implications for not only predicting future precipitation changes but also mitigating precipitation-change-associated risks on ecosystems and human society in the Great Basin.