近40年玛曲地区牧草生长期蒸降差的变化特征

利用甘肃省玛曲县气象站1971-2010年的地面气象观测资料,根据Penman-Monteith模型计算了玛曲地区草地潜在蒸散量,并对近40年玛曲地区牧草生长期蒸降差的变化趋势进行了分析,发现近40年玛曲地区牧草生长期蒸降差以12.1mm·10a-1的趋势上升,其中牧草生长初期和末期蒸降差以3.5和11.2mm·10a-1的速度上升,牧草生长中期蒸降差呈略下降的趋势,下降速度为-2.6 mm·10a-1。20世纪90年代,由于潜在蒸散量增大和降水量减少,造成蒸降差增大,牧草生长期出现了水分亏缺现象。水分亏缺是导致玛曲草地退化和生态环境恶化的主要原因之一。

Variation characteristics of the difference between evaporation and precipitation during grass growing season in Maqu County from 1971-2010

In order to study the variation characteristics of the difference between evaporation and precipitation during the grass growing season in Maqu County, the Penman Monteith model was employed to compute the potential evapotranspiration based on the meteorological data from 1971 to 2010 in Maqu weather observation station. The results indicated that the difference between evaporation and precipitation in Maqu increased with the ratio of 12.1 mm·10 a-1 during the grass growing season. The difference between evaporation and precipitation in the start and end period of growing season increased with the ratio of 3.5 and 11.2 mm·10 a-1, respectively, whereas the difference decreased in the middle period of growing season with the ratio of -2.6 mm·10 a-1. The water deficit occurred in the 1990s due to the increase of potential evapotranspiration and the decrease of precipitation. Water deficit was one of the most important impact factors for the grassland degradation and environmental deterioration in Maqu County.