近54a蒙古高原降水变化趋势及区域分异特征

近半个世纪，有关全球气候的话题一直是科学界争论的焦点，拥有世界最大温带草原的蒙古高原降水变化是属于全球变化问题，又是其脆弱环境变化的最主要驱动因子之一。通过利用蒙古高原1961—2014年136个气象站点的月降水量数据，采用Sen’ s斜率法、Mann-Kendall趋势检验法和空间地统计方法，研究了该地区近54 a降水要素基本气候特征及其时空变化规律。结果表明：（1）近54 a蒙古高原年降水量呈减少趋势，趋势为-2.30 mm·（10 a）^-1（P＞0.05），整体上年降水量东南及西北显著减少，东北及中南明显增加（2）夏季和秋季降水量呈减少趋势，趋势分别为-5.75 mm·（10 a）^-1和-0.42 mm·（10 a）^-1（P＞0.05）；春季和冬季降水量呈显著增加趋势，趋势分别为1.95 mm·（10 a）^-1和0.50 mm·（10 a）^-1（P<0.05）；季节降水量出现正负距平的年份和周期有所不同。（3）春季和冬季降水量呈增加趋势的站点居多，占全部站点的89.0%和84.6%，主要分布于高原东北部和中南部地区；夏季和秋季降水量呈减少趋势的站点居多，占全部站点的80.1%和57.4%，主要分布于高原东南部和西北部地区。为准确评估蒙古高原气候变化以及合理提出生态环境决策提供科学参考。

Change trend and regional differentiation of precipitation over the Mongolian Plateau in recent 54 years

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.