荒漠草原脉动性降水格局及其时空变化特征——以达尔罕茂明安联合旗为例

全球变化背景下,荒漠草原降水格局受到不同程度扰动,识别荒漠草原变化环境下脉动性降水格局及其时空变化特征具有重要生态学和水文学意义。利用达尔罕茂明安联合旗位于不同雨量带的3个气象站1960—2013年日降水数据,分析荒漠草原地区降水格局及其时空变化特征。研究表明,研究区0—5 mm、5—10 mm和大于10mm降水事件及降水量所占的比例分别为77%—80.9%、11.5%—12.2%、7.6%—10.9%和25.2%—32.2%、21.9%—25.4%、42.4%—52.9%。不同等级降水事件日均降水量分别为1.2—1.3 mm/d、7.0—7.1 mm/d、17.8—19.2 mm/d。研究区降水量较降水日数具有更强的时空变异性,全年和生长季降水日数和降水量主周期在2.84—4.5a左右。研究区不同雨量带不同降水等级降水日数和降水量普遍呈增加趋势,尤以0—5mm小降水事件的增加为主。

Precipitation pulse patterns and their spatiotemporal variation in desert steppes: a case study in the Darhan Muminggan Joint Banner

Against the backdrop of global climate change, precipitation patterns in desert steppes have undergone varying degrees of disturbance. There is a particular significance in recognizing these alterations for both the hydrology and ecology of the changing environments of desert steppes. In this study, daily data from three meteorological stations located in regions of different precipitation gradients in the Darhan Muminggan Joint Banner were used to analyze precipitation patterns in desert steppes and their variation characteristics. Unlike previous studies on this topic, this research utilized precipitation events from areas of different precipitation gradients for comparison at the same temporal scale. Precipitation events of different levels were analyzed to determine the precipitation composition of desert steppes and its spatiotemporal variation. The results indicated that, overall, as the annual precipitation decreased, the fluctuation in the number of precipitation days and the precipitation amount in the study area gradually increased. Also, the fluctuations in precipitation amount were significantly greater than the fluctuations in the number of precipitation days, which meant that precipitation amount had greater spatiotemporal variability than the number of precipitation days. The proportions of the number of precipitation days of 0-5 mm, 5-10 mm, and >10 mm precipitation events were 77%-80.9%, 11.5%-12.2%, and 7.6%-10.9%, respectively, while the precipitation amount proportions of 0-5 mm, 5-10 mm, and >10 mm precipitation events were 25.2%-32.2%, 21.9%-25.4%, and 42.4%-52.9%, respectively. The mean precipitation amounts on a rainy day with 0-5 mm, 5-10 mm, and >10 mm precipitation events were 1.2-1.3 mm/d, 7.0-7.1 mm/d, and 17.8-19.2 mm/d. From the annual distribution of precipitation events of different levels, which were affected by the combination of the southeast monsoon and the terrain, it could be seen that the 0-5 mm precipitation events were mainly concentrated from June to September in the growing season. The 5-10 mm precipitation events occurred mostly in July, and the >10 mm precipitation events predominantly occurred in August. Both the amount of precipitation and the number of precipitation days showed an increasing trend in the study area. A major feature of pulse precipitation from 1960 to 2013 in the desert steppe region of the study area was that 0-5 mm precipitation events showed an increasing trend in terms of both the precipitation amount and the number of precipitation days. In the Bailingmiao and Mandulla regions, where annual precipitation was relatively low, both the number of precipitation days and the precipitation amount showed an increasing trend for all precipitation levels. This was another significant feature of precipitation events in the study area. However, in the Xilamuren region, where the annual amount of precipitation is relatively high, there has been a shift in the internal precipitation structure from large and medium precipitation events to small precipitation events, although the annual precipitation continues to show an increasing trend. The annual precipitation and growing-season precipitation had 2.84-4.5 a main periods. The differences among the precipitation gradients are inconspicuous, and from the perspective of the precipitation events of different levels, the overall trend indicates that the higher the precipitation level, the shorter the cycle of precipitation events.