基于ETM+与MODIS数据融合的伊洛河流域地表蒸散估算

MODIS数据时间分辨率较高,在对地能量和水分变化监测应用中具有不可比拟的优势。但其空间分辨率较低,混合象元效应显著,尤其在地表土地利用类型复杂和空间异质性较大时,会带来较大的误差。而ETM+数据具备较高的空间分辨率,但其单一的热红外波段导致反演的地表温度精度不高,且时间分辨率低,因而限制了在地表蒸散监测中的应用。本文探讨了将TM/ETM+与MODIS数据相融合估算区域地表蒸散的一种多尺度遥感方法,利用TM/ETM+计算得到的植被指数,基于空间增强方法将MODIS反演的地表温度尺度提高到30 m,并结合SEBS模型对伊洛河流域的地表蒸散进行了估算。验证与分析的结果表明,估算精度得到提高,研究区当日蒸散量在0～5.32 mm/d之间,空间分布具有明显的地域性差异,区域分布不均衡。

Land surface evapotranspiration estimation of Yiluo River Basin based on fusion of ETM+ and MODIS data

The Moderate Resolution Imaging Spectroradiometer(MODIS)data has a high time resolution,which,at present,is an ideal data source in simulative monitoring of regional-scale changes in surface energy and water.However,the spatial resolution of its thermal infrared band is relatively low(1 km).When there are large differences in the space and underlying surface geometry structure,MODIS has significant spatial scale effects (mixed-pixel),and cannot analyze the underlying surface changes within the pixel and the resulting estimation error.The TM/ETM+data have a high spatial resolution,but their single thermal infrared bands can lead to the fact that the inversion accuracy for the surface temperature is not high,and that the time resolution is low.This limits its application in the surface evapotranspiration(ET)monitoring.Combining TM/ETM+visible wave band with MODIS thermal infrared wave band,this paper discusses a multi-scale remote sensing method to estimate regional surface ET.On the basis of space enhancement method,the vegetation index estimated by TM/ETM+enhances the surface temperature scale with the inversion of MODIS to a 30 m resolution,which aims to improve the estimation accuracy of ET in the non-uniform surface mixed-pixel.Using multi-scale remote sensing method and SEBS model,this paper estimates the surface ET in the Yiluo River Basin in combination of ground measured data for validation and analysis.The results show that this method has a higher accuracy of ET estimation compared with the method of only using MODIS or ETM+ data.Moreover,it can obtain a more obvious effect on scale correction in the uneven land surface or various surface covering types,and the corrected ET is close to the observation result.The ET in the study area is 0-5.32 mm/d,and the spatial distribution of surface ET has significant uneven regional differences,which has a high degree in the south,a low degree in the north,and high in the mountain,low in the valley.