Spatial and temporal variability of precipitation in the context of climate change: A case study of the Upper Yellow River Basin, China

Trends, mutations and periodicity of precipitation variation in the Upper Yellow River Basin (UYRB) were studied using a fitted liner model, Mann-Kendall test, moving t-test and Morlet wavelet based on the measured daily data in 34 meteorological stations from 1957 to 2010, and the spatio-temporal variation characteristics of precipitation from 2011 to 2100 were predicted through building statistical downscaling model using BP network. The inter-annual precipitation variation in the basin showed a non-significant increase trend during the measurement period. However, in terms of monthly variation, the precipitation increased between January and June (except April) while decreased between July and November (except October), in addition, it has no obvious change in December. The spatial distribution of precipitation during the whole measurement period mainly showed decreased trend in rainy zone while increased trend in arid zone. The Moving-t test results showed that the annual precipitation in the basin has no significant mutation points between 1957-2010, the most possible one was in 1992. Due to the geographical location of the meteorological stations, the precipitation got some different mutation points. Furthermore, significant differences occurred in the results between M-K and Moving-t test in change-point analysis. There were two considerable time scale periodical variations in basin annual precipitation which were the four to seven years and the over 30 years. Projected precipitation in the future in three different forecast periods under the A1B, A2 and B1 emission scenarios were bigger than the ones measured, except in 2025s under A1B emission scenarios. However, the projected monthly precipitation variation showed different characteristics under these three emission scenarios compared to the measured ones. For the spatial distribution of precipitation variation in the future, it increases firstly and then decreases from southwest of the basin to northeast under A1B scenario compared to the measured periods, while increases firstly and then decreases from northwest of the basin to southeast under A2 scenario. However, the precipitation under B1 scenario gradually increases from southwest of the basin to northeast compared to the measured periods.