基于GRACE重力卫星数据的黄河源区实际蒸发量估算

Estimation of the Real Evaporation in the Source Regions of the Yellow River Using GRACE Satellite Data

利用GRACE卫星数据反演得到黄河源区唐乃亥流域2003—2008年流域水储量变化,结合同时间段黄河源区降雨及径流资料,根据水量平衡方程,估算流域逐月实际蒸发量.结果表明:估算的结果与20cm蒸发皿观测值和SiB2模型模拟的结果具有较好的一致性和相关性.黄河源区2003—2008年年平均实际蒸发量约为506.4mm,其中,春季(3—5月)为130.9mm,约占全年的25.8%;夏季(6—8月)为275.2mm,约占全年的54.3%;秋季(9—11月)为74.3mm,约占全年的14.7%;冬季(12月至翌年2月)为26.2mm,约占全年的5.2%.2003—2008年源区降水基本保持不变,蒸发呈减少趋势,径流略有增加,径流峰值期提前,黄河源区水储量增加速率为0.51mm.month-1,相当于82.6×104 m3.a-1,总增加水量约496.6×104 m3.降水平均增加速率为0.019mm.month-1,水储量增加速率为0.51mm.month-1,而蒸发的下降速率为0.52mm.month-1,径流的增加速率为0.034mm.month-1.因此,在降水量变化不大的情况下,蒸发的下降和冻土消融导致水储量的增加明显,这也是引起地表径流增加的原因.

The water storage change data from 2003 to 2008 in the source regions of the Yellow River is retrieved from GRACE satellite data.Furthermore,the monthly real evaporation in the source regions is estimated according to water balance equation by using runoff and precipitation data.It is found that they are consistent better and correlative with not only the observation with evaporation pan(20 cm),but also with the simulated result of SiB2 model.The annual average evaporation in Tangnag basin is nearly 506.4 mm,of which 130.9 mm in spring(Mar.,Apr.and May),275.2 mm in summer(June,July and Aug.),74.3 mm in autumn(Sep.,Oct.and Nov.) and 26.1mm in winter(Dec.,Jan.and Feb.).From 2003 to 2008,precipitation had increased slightly and real evaporation had decreased obviously;precipitation had increased with a rate of 0.019 mm·month-1,water storage had changed with a rate of 0.51 mm/month,while evaporation had decreased with a rate of 0.52 mm/month.During the study period,the water storage in the source regions of the Yellow River had increased about 496.6×104 m3,equivalent to 82.6×104 m3·a-1.Precipitation had changed not so much.However,decline of evaporation and degradation of permafrost had led storage capacity increasing significantly and then surface runoff increasing.