Abstract: The topic of global climate has been the focus of scientific debate for nearly half a century. Precipitation change of Mongolian Plateau, where distributes the largest temperate grassland in the world, is not only a global change issue, but also one of the main driving factors of its fragile environment change. Climatic characteristics of precipitation and its spatial and temporal variations were analyzed with Sen’s slope, Mann-Kendall trend test and geostatistical method based on the monthly precipitation data of 136 weather stations across the Mongolian Plateau during 1961—2014.The results show as follows: (1) Plateau averaged multiyear mean annual precipitation was 305.6 mm with spatial distribution gradually decreasing from the northern, eastern and southeastern parts of the Plateau to the central regions. Annual precipitation showed a decreasing trend at the rate of -2.30 mm·(10 a)^-1 (P>0.05) over the Mongolian Plateau in recent 54 years with the obvious positive anomalies in the 1990s and negative ones in the 2000s of 21^st century. On the whole, significant decreasing trends of annual precipitation were observed in the southeastern and northwestern region, while significant increasing trends were found in the northeastern and central and southern regions. (2) Seasonal mean precipitation is 40.6 mm,207.9 mm,50.4 mm and 6.8 mm in spring, summer, autumn and winter, accounting for 13.3%, 68.0%, 16.5% and 2.2% of the annual precipitation, respectively. In interannual variability, precipitation in summer and autumn showed a decreasing trend at the rate of -5.75 mm·(10 a)^-1 and -0.42 mm·(10 a)^-1 (P>0.05) respectively over the period of 1961—2014,while precipitation in spring and winter showed a significant increasing trend at the rate of 1.95 mm·(10 a)^-1 and 0.50 mm·(10 a)^-1 (P <0.05) respectively. The years with positive or negative anomaly and periodic changes are quite different for the seasonal precipitation. (3) A majority of stations showed increasing trend for spring and winter precipitation, which accounting for 89.0% and 84.6% of all stations respectively, and mainly distributed in the northeast and central southern part of the Mongolian Plateau. While a large number of stations displayed decreasing trend for summer and autumn precipitation, which accounting for 80.1% and 57.4% of all stations respectively, and mainly located in the southeast and northwest parts of this Plateau. This paper found opposite trends in the fraction of summer precipitation, with significant declines, while the contribution of non-summer (spring, autumn and winter) precipitation increased, which implied a seasonal reallocation of precipitation in the study area. A decline of summer precipitation together with a strong temperature increase will increase evaporation rates, which will likely cause water resource shortages, drought, and declines in vegetation productivity. This paper could provide scientific reference for accurate assessment of climate change and reasonable decision-making of ecological environment across the Mongolian Plateau.

Key words: font-size:10.5pt, 蒙古高原')">">蒙古高原, 降水量, 变化趋势, 季节变化, 区域分异