基于遥感-过程耦合模型的地表蒸散量应用研究

摘要

As an important processes of the land and atmosphere interaction in land surface process, evapotranspiration (ET) plays an key role in the biosphere, atmosphere and hydrosphere. In this paper, the remote sensing process coupling model BEPS was used. The main inputs were the Moderate Resolution Imaging Spectroradiometer (MODIS) data and the NCEP/NCAR reanalysis datas. We simulated and analyzed land surface evapotranspiration of the United States from 2007 to 2009. Meanwhile, the flux observation data of AmeriFlux was used to verify the reliability and applicability of the model in evapotranspiration simulation The results show that:the correlation coefficient of the land surface evapotranspiration between the BEPS model and the measured data was 0.729 7 (P<0.05), which mean that BEPS model could be well used in simulating the evapotranspiration in America. ET showed a single peak trend obviously within a year, which value was high from May to Septembe and more than 60 mm·mon-1. The minimum value was 8.39 mm·mon-1 in January, while maximum value was 18.04 mm·mon-1 in July. And the annual evapotranspiration was 505 mm·a-1. Influenced by topography, climate and evapotranspiration, the southern region mainly covered by grassland and farmland had the highest value, where annual evapotranspiration was generally above 600 mm·a-1 and the highest value was 1 667 mm·a-1. Annual evapotranspiration was 400-600 mm·a-1 in north-central area and Eastern area. The value of evapotranspiration in the western area where vegetation types were woodland and mixed forest., presented to be lowest among all area in America, which annual evapotranspiration was less than 400 mm·a-1. What's more, the value of precipitation minus ET showed a decreasing trend from eastern area to western area, which minimum value was mainly distributed in the western desert. The ratio of ET and precipitation was 0.72 increased from east to west, and reached the maximum value in western and north-central area.%　　作为陆面过程中地气相互作用的重要过程之一，蒸散发(Evapotranspiration，ET)在地球的大气圈-水圈-生物圈中发挥着重要作用。利用遥感-过程耦合模型BEPS，以中分辨率成像光谱仪(MODIS)数据和NCEP/NCAR再分析资料为主要输入，模拟分析了2007-2009年美国区域的地表ET，同时利用通量观测网AmeriFlux的站点观测数据验证该模型在ET模拟研究中的可靠性与适应。结果表明：12个站点通量实测值与BEPS模型模拟的ET值的相关系数为0.7297(P<0.05)，表明BEPS模型能够较好的模拟研究区的地表ET。ET在1年内呈现明显的单峰趋势，5-9月ET值较高，可达60 mm·mon-1以上，最小值在1月份，值为8.39 mm·mon-1，最大值在7月份，值为118.04 mm·mon-1。该区域ET的平均年总量为505 mm·a-1。受地形、气候的影响，ET最高值对应于南部区域，这些地区ET的年总量普遍在600 mm·a-1以上，最高值为1667 mm·a-1，对应的主要覆被类型为草地和农田；中北部和东部的大部分区域ET年总量为400~600 mm·a-1；ET最小值在西部区域，年总量小于400 mm·a-1，对应覆被类型为疏林地和混交林。降水量与ET差值呈现从东向西逐渐递减的趋势，最小值主要分布在西部沙漠。整个研究区域ET与降水量之比的平均值为0.72，由东向西基本呈现增加趋势，在西部以及中北部的部分地区比值达到最大。