water Article Entropy-Based Research on Precipitation Variability in the Source Region of China’s Yellow River Henan Gu 1,2,* , Zhongbo Yu 1,2,*, Guofang Li 2, Jian Luo 2, Qin Ju 1,2, Yan Huang 3 and Xiaolei Fu 4 1 State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing 210098, China;
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[email protected] (Z.Y.); Tel.: +86-135-8520-9927 (H.G.); +025-8378-6721 (Z.Y.) Received: 15 August 2020; Accepted: 3 September 2020; Published: 5 September 2020 Abstract: The headwater regions in the Tibetan Plateau play an essential role in the hydrological cycle, however the variation characteristics in the long-term precipitation and throughout-the-year apportionment remain ambiguous. To investigate the spatio-temporal variability of precipitation in the source region of the Yellow River (SRYR), different time scale data during 1979–2015 were studied based on Shannon entropy theory. Long-term marginal disorder index (LMDI) was defined to evaluate the inter-annual hydrologic budget for annual (AP) and monthly precipitation (MP), and annual marginal disorder index (AMDI) to measure intra-annual moisture supply disorderliness for daily precipitation (DP). Results reveal that the AP over the SRYR exhibits remarkable variation, with an inclination rate of 2.7 mm/year, and a significant increasing trend.