科尔沁沙地典型区生长季蒸散发估算及其变化特征

为揭示科尔沁沙地典型区地表参数和蒸散发的时空分布以及变化特征,采用Landsat-7和气象数据,并结合METRIC(Mapping Evapotranspiration at high Resolution with Internalized Calibration)模型,分析了研究区净辐射(Rn)和蒸散发(ET)的时空变化、不同土地覆被类型ET特征及其影响因素。结果表明:(1)研究区典型土地覆被沙丘和草甸的Rn和ET估算值与涡度相关实测值拟合结果均良好,说明METRIC模型可以为研究区提供合理的ET估算;(2)研究区下垫面Rn和ET的时空分布情况为:各年Rn和ET在年内变化趋势相同,空间上不同土地覆被类型中水体的Rn和ET最大,农田和草甸次之,沙丘最小;(3)沙丘的CV值大于农田与草甸,表明年际间沙丘的ET波动较大,农田和草甸相对稳定,ET年际变化主要受气象因素的影响。

Estimation of growing season evapotranspiration and its variation in a typical area of Horqin Sandy Land

The spatial and temporal distribution of surface parameters and evapotranspiration (ET), and their variation, were determined in a typical area of Horqin Sandy Land. Landsat 7 remote sensing images and meteorological data were obtained and the Mapping Evapotranspiration at high Resolution with Internalized Calibration (METRIC) model was used to determine spatio-temporal variations of net radiation (R_n) and ET, ET properties under different land cover types, and the factors influencing ET. Three key results were obtained. ① Model estimates were strongly linearly correlated with observed values, which confirmed that METRIC provided reasonable ET estimates in the Horqin Sandy Land. ② The spatio-temporal variations of R_n and ET in the underlying surface of the study area showed that the inter-annual R_n and ET had the same trend in each year, with the maximum R_n and ET occurring from water bodies followed by farmland and meadows, while the minimum was from sandy dunes. ③ The coefficient of variation (C_V) of sandy dunes was larger than that of farmland and meadows. The most obvious inter-annual variation occurred in sandy dunes, whereas farmland and meadows were stable. In all three types of land, inter-annual changes in ET were mainly due to meteorological factors.