利用NOAA数据估算黄河三角洲区域蒸散量

Estimated Evapotranspiration Based on NOAA Data in the Yellow River Delta

蒸散(发)量是水资源相互转化过程中非常重要但又难以定量确定的要素之一。SEBS(SurfaceEnergyBalanceSystem)模型是20世纪末期发展起来的利用遥感数据计算区域蒸散(发)量的重要模型,利用该模型可以在较少地面信息的情况下获得蒸散(发)量的区域分布信息。本文采用SEBS模型,利用NOAA数据对我国重要的粮食和石油生产基地黄河—三角洲区域蒸散发量进行了研究。结果表明,黄河三角洲黄河两岸、黄河故道和滨海等地蒸散发量较大,年平均蒸散发量570mm～860mm,蒸散发量的峰值出现在6、7、8几个月份,每年的元月份是蒸散发量的低值期。计算结果与实际情况相符,说明遥感手段研究黄河三角洲的区域蒸散发量是可行的,与传统方法相比,遥感方法具有无可比拟的优越性。

Evapotranspiration (ET) is the second most significant component of the hydrologic cycle next to precipitation. Among the several ET estimation methods, the remote sensing method is regarded as the only technology that can efficiently and economically provide regional and global coverage of actual consumption. The Surface Energy Balance System (SEBS) has been designed to calculate the energy portioning at the regional scale with minimum ground data and has been verified at many places in the world including China. SEBS is a satellite image-processing model for computing ET maps for large areas. This paper first used the SEBS method to estimate ET according to NOAA data in the Yellow River Delta (YRD) in Shandong province of China. Net radiation, Soil heat flux and Sensible heat computations are made specific to each pixel in the image. Iterative predictions of sensible heat are improved using atmospheric stability corrections based on Monin-Obukhov in SEBS model. Seen from the result of calculated ET, the higher ET usually occurs in the yellow river side banks, the old river course and the contiguity to the sea belts etc. The annual average evaporation varied between 570mm and 860mm, and the peak value always appears in June, July and August; the lower ET in January. The estimated average daily ET is a little lower than the crop reference daily ET in the YRD. Analyzed from the long-term water balance and groundwater table, the ET is little higher than the precipitation and the groundwater table is gradually falling down from 1990 to 1997. The bare land is bigger and groundwater table is higher, so the water consumption is mostly invalidation evaporation in the YRD and violence evaporation results in land salinization. All these results are consistent with the reality. This indicates that the SEBS method is feasible to estimate ET in the YRD and it has the incomparable superiority comparing to the traditional method, which is based on the spots information and then getting the region-scale ET through the interpolation method.