Changes in precipitation extremes over Shaanxi Province, northwestern China, during 1960–2011

Changes in indices of precipitation extremes were analyzed on the basis of daily precipitation observational data at 19 surface meteorological stations over Shaanxi Province during 1960–2011, originating from the China Meteorological Administration. Ten indices of extreme precipitation were studied. Maximum 1-day precipitation, very wet day precipitation, extremely wet day precipitation, simple daily intensity index, and consecutive dry days in the study area during 1960–2011 exhibit non-significant increasing trends. Decreasing trends are found for maximum 5-day precipitation, wet day precipitation, number of heavy precipitation days, number of very heavy precipitation days, and consecutive wet days, all statistically non-significant. For number of heavy precipitation days and consecutive wet days, stations in the study region have consistently negative trends. The variation trends for the other extreme precipitation indices have regional differences, and the change patterns of these indices are not spatially clustered. Very wet day precipitation experiences abrupt decreases in 1977 and 1985, while a significant abrupt increase change for extremely wet day precipitation is detected in 1983. There are multiple cycles in the changes for the very wet day precipitation and extremely wet day precipitation over Shaanxi Province during 1960–2011, showing variations of time and frequency. Except for consecutive dry days, the other extreme precipitation indices have high correlations with annual total precipitation. The elevation is positively correlated with consecutive dry days. There are negative correlations between the other extreme precipitation indices and elevation.