Changes in annual, seasonal and monthly precipitation events and their link with elevation in Sichuan province, China

This study performs the spatial and temporal trend analysis of the annual, seasonal and monthly time series of a set of uniformly distributed 36 stations precipitation data in Sichuan Province during 1960-2013. The result indicates that the annual precipitation amount and precipitation days across the region have decreasing trends, but the last is significant. The annual precipitation intensity and maximum 1-day precipitation have slightly increasing trends. Although annual precipitation amount and precipitation days decline, annual precipitation intensity and maximum 1-day precipitation rise. This reflects that droughts and floods increase in Sichuan Province in recent years. Seasonally, precipitation amount has decreased in all seasons, while autumn precipitation amount is statistically significant. Regionally average trends in precipitation days also show large differences in all seasons. The temporal variability in regional precipitation intensity increases except for autumn, but significant increases are found in spring and summer. Regional maximum 1-day precipitation has significantly increasing trends in spring and summer, but slightly decreasing trend in autumn and winter. On a monthly basis, trends of precipitation amount show tremendous differences. Spatial changes in annual, seasonal and monthly precipitation events are not the same, and they are not clustered, either. Additionally, the correlations between elevation and the magnitudes of the trends in annual precipitation amount and precipitation days are statistically significant whereas the correlations are not perfect in precipitation intensity and maximum 1-day precipitation. As can be seen from the seasonal and monthly precipitation amount, the correlations between elevation and the magnitudes of the trends in precipitation amount are higher in spring and autumn, but not perfect in summer and winter. April, October and December precipitation amount shows the strongest positive correlations with elevation. On the whole, the increasing trend of precipitation is relatively prominent at higher elevations, while the decrease trend is more significant at low elevation stations.