新疆阿克苏河上游高寒草甸蒸散发观测与估算

蒸散发是水循环的关键环节, 是水量平衡的重要组成部分. 由于在高寒山区进行长期野外观测的难度较大, 导致对区域实际蒸散发的认识不清, 从而无法明确区域水资源分配与不同植被的生态水文功能. 在天山山区, 高寒草甸占其总面积近15%, 其对降水的调节作用巨大, 但目前高寒草甸的实际蒸散发量多用潜在蒸散发进行推算, 缺少实际观测数据. 2012年10月-2013年9月, 利用3个小型蒸渗仪观测了阿克苏河上游科其喀尔冰川综合考察站附近山区的高寒草甸的实际蒸散量, 并尝试利用最小二乘支持向量机(LS-SVM)估算实际蒸散发. 结果表明:研究区高寒草甸全年内实测蒸散量511.3 mm, 日均蒸散量为1.4 mm·d^-1; 在不同时期, 蒸散量变化剧烈, 冻结期、生长前期、生长期和生长后期的蒸散量分别为53.9、41.0、363.8和52.6 mm, 分别占全年蒸散量的10.5%、8.0%、71.2%和10.3%. 最小二乘支持向量机对实际蒸散发的估算精度较高, 对观测资料相对缺乏的高寒山区来说, 不失为一种较好的估算蒸散发方法.

Observation and estimation of the evapotranspiration of alpine meadow in the upper reaches of the Aksu River,Xinjiang

Evapotranspiration (ET) plays an important role in water balance. However, there is a great difficulty to get long-term records of ET by field observations in high-cold mountainous regions, resulting in lack of understanding the ET of alpine meadow, in spite of the meadow covering a large of area in high-cold mountains. Weighing microlysimeter method had been used to gain the ET of alpine meadow in the upper reaches of the Aksu River. Measurement revealed that the total ET of the alpine meadow was 511.3 mm, and the daily average was 1.4 mm·d^-1. The value of ET varies significantly with season. The values of ET in freezing stage, early growing stage, growing stage, last growing stage were 53.9, 41.0, 363.8 and 52.6 mm, respectively, and their proportions occupy 10.5%, 8.0%, 71.2% and 10.3% of the annual ET values respectively. In this paper, it is also discussed that the applicability of the least squares support vector machine (LS-SVM) in estimation of the actual ET in alpine meadow. The results showed that LS-SVM can better estimate actual ET with high accuracy, which will be a good and useful method for estimating actual ET in the high-cold mountainous regions.