Analysis of Spatiotemporal Variation in Precipitation on the Loess Plateau from 1961 to 2016

This study utilized annual precipitation data collected from 76 meteorological stations located on the Loess Plateau and its adjacent regions. It employed empirical orthogonal function (EOF) analysis, the Mann–Kendall trend test (M-K), and continuous wavelet transform (CWT) to investigate the spatial distribution patterns, temporal trends, and periodicity of annual precipitation from 1961 to 2016. The results showed the following: (1) The long-term averages of annual rainfall on the Loess Plateau exhibited a general decline from the southeast to the northwest, with certain areas demonstrating a trend of reduction radiating outward from the central region. This precipitation regime was fundamentally governed by the interplay between geographic coordinates and topo-graphical characteristics. Nevertheless, this spatial distribution pattern is expected to undergo changes in the future. (2) Annual precipitation in the southern and eastern parts decreased significantly, while the western part reported the greatest increase, and thus the spatial variability of precipitation will decrease in the future. (3) Annual precipitation on the Loess Plateau generally has a period of about 4 years. The wavelet coherence analysis reveals that El Niño events, occurring over a brief 4-year interval, correlate with diminished precipitation patterns across the eastern and southern sectors of the Loess Plateau, consequently attenuating the precipitation’s spatial variability throughout the entire geographical domain. Therefore, in the future, when El Niño occurs, it is necessary to prevent droughts in the eastern and southern regions of the Loess Plateau.