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为构建有效的干旱监测与评估指标,利用中分辨率成像光谱仪(MODIS)数据以及NCEP/NCAR再分析资料并基于遥感过程耦合模型BEPS模拟了地表蒸散(evapotranspiration,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性,在此基础上,构建BMI指数,分析了2007-2009年研究区域干湿状况的时空分布特征,并与其他干旱指数进行对比分析。结果表明:12个站点通量实测值与模型模拟的ET的相关系数为0.8568(p<0.01),表明BEPS模型能够较好的模拟美国陆地生态系统的ET。BMI值的空间分布特征较为明显,与降水量与ET经纬向变化较为一致。而BMI值的时间分布特征表明,其具有较为显著的季节变化。这与地形、气候特征以及植被的分布关系密切。从检验效果来看,受降水量的影响,BMI在月尺度以上干旱监测效果相对较好。BMI与USDM的相关系数表明,本文在BEPS模型模拟ET的基础上构建的指标在干旱监测中是可行的。
In order to establish an effective indicator for drought monitoring and assessment, surface evapotranspiration (ET) was simulated using mid-resolution imaging spectroscopy (MODIS) data and NCEP / NCAR reanalysis data and based on the remote sensing coupled process model BEPS. At the same time, the reliability and adaptability of this model in ET simulation research were verified by using the observation data of AmeriFlux in the flux observation network. On this basis, the BMI index was constructed and the spatial and temporal distribution of dry and wet conditions in the study area from 2007 to 2009 Characteristics and comparative analysis with other drought index. The results showed that the correlation coefficient between the measured values of 12 stations and the ET simulated by the model was 0.8568 (p <0.01), indicating that the BEPS model can better simulate the ET of terrestrial ecosystems in the United States. The spatial distribution of BMI value is more obvious, and the change of precipitation and ET latitude and longitude are more consistent. The BMI value of the time distribution characteristics show that it has a more significant seasonal changes. This is closely related to the topography, climatic characteristics and the distribution of vegetation. From the test results, by the impact of precipitation, BMI in the monthly scale above the drought monitoring results are relatively good. The correlation coefficient between BMI and USDM shows that the index constructed on the basis of BEPS model ET is feasible in drought monitoring.