基于AVHRR NDVI、IGBP土地覆盖分类和气象站观测数据，利用Shuttleworth-Wallace（S-W）模型估算韩江流域2000－2006年的潜在蒸散发（PET），结果显示PET不仅受气候条件影响，而且随植被类型及其生长过程而变化。分析PET对气候和植被的敏感性，结果表明：1）PET对植被的类型很敏感，相同气候条件下，不同植被的 PET 计算结果相差很大，常绿针叶林、农作物和多树草地的多年平均 PET 分别为1136.6，965.1，563.2 mm/a，最大值和最小值相差1倍。2）不同植被覆盖的PET对气候的敏感性不同。常绿针叶林的PET对水汽压最为敏感，明显高于气温和太阳辐射的敏感性，而风速的敏感性可以忽略；农作物的PET除对风速的敏感性较低外，气温、太阳辐射和水汽压的敏感性都较高，最为敏感的是气温；多树草地的PET同样对气温最为敏感，水汽压、风速和太阳辐射的敏感性也都比较高，而且很接近。3）各种植被覆盖的PET对叶面积指数（LAI）都有一定的敏感性，但都小于气象因子（风速除外）的敏感性；不同植被覆盖的PET对LAI的敏感性也不同，多树草地的PET对LAI最敏感，其次是常绿针叶林，再次是农作物。%Potential evapotranspiration (PET) as an estimate of crop water demand and a key input to hydrological modeling, not only affected by the changes in climate, but also affected by changes in vegetation covers. Sensitivity of PET to climate and vegetation is helpful in understanding the impact of climate changes and vegetation covers changes on water resources, and also is important to the optimal allocation of agricultural water resources. In this study, PET was calculated by Shuttleworth-Wallace (S-W) model. Threshold values of vegetation parameters in S-W model were drawn from the literature based on the International Geosphere-Biosphere Programme (IGBP) land cover classification. The spatial and temporal variation of vegetation leaf area index (LAI) was derived from the composite AVHRR NDVI using the SiB2 method. The long-term meteorological dataset at 752 meteorological stations in China was used to provide the required meteorological data. Using the meteorological data from meteorological stations and the monthly composite AVHRR NDVI data from NASA GIMMS during the period of 2000-2006, PET over Hanjiang River basin was estimated by S-W model. It showed that the PET was not only affected by climate, but also changed with vegetation types and the growth of vegetation. PET was very sensitive to vegetation types. The calculated PET of different vegetation in the similar climate condition is quite different. The annual mean PET of evergreen needle leaf forests, croplands and woods savannas was 1136.6, 965.1 and 563.2 mm/a, respectively. The maximum value was twice as the minimum value. The sensitivity of the PET to meteorological factors was analyzed. It showed that the sensitivity of the PET to climate was quite different for different vegetation covers. PET of evergreen needle leaf forests is the most sensitive to vapour pressure. Its sensitivity coefficient was much larger than that of air temperature and solar radiation. The sensitivity of wind speed can be ignored. PET of croplands was sensitive to air temperature, solar radiation and vapour pressure while it was not so sensitivity to wind speed. Among all the meteorological factors, the PET of croplands was the most sensitive to air temperature. PET of woods savannas was also the most sensitive to air temperature, and was also sensitive to vapour pressure, wind speed and solar radiation. Their sensitivity coefficients were very close to each other. The sensitivity of the PET to vegetation LAI was then analyzed. It showed that PET of all vegetation covers was sensitive to LAI, but the sensitivity coefficients were smaller than that of the meteorological factors (except for wind speed). The sensitivity of the PET to LAI was different for different vegetation covers. PET of woods savannas was the most sensitive to LAI, followed by evergreen needle leaf forests and croplands.
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