Collaborative Research: Estimating Regional Forest Evapotranspiration and Photosynthesis with a Satellite Derived Vegetation Index and Surface Temperatue

合作研究：利用卫星推导的植被指数和地表温度估算区域森林蒸散量和光合作用

• 批准号: 8905278
• 负责人: Samuel Goward
• 金额: $ 26.27万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1989
• 资助国家: 美国
• 起止时间: 1989-01-15 至 1992-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8905278&HistoricalAwards=false
• 关键词: Collaborative; Research; Estimating; Regional; Forest

Current maps of global vegetation have been produced by the Normalized Difference Vegetation Index (NDVI) from the AVHRR satellite sensor. These maps have been related to absorbed solar radiation or surface leaf area index, but the NDVI has only been related theoretically to evapotranspiration and photosynthesis processes for vegetation and then only under optimal conditions of water and temperature, constraints that severely limit real world applications. The project will utilize a simple evapotranspiration and photosynthesis model for forests driven entirely by AVHRR data that is sensitive to sub-optimal water and temperature conditions. The investigators will (1) relate the seasonal trend of weekly composite NDVI to vegetation phenology and temperature limits, (2) test a satellite-derived surface resistance factor which is related to canopy diffusion resistance and (3) define physiologically based energy to mass conversion factors for carbon and water. These NDVI driven models will then be evaluated against a more complex ecosystem process model. The resulting simple, satellite-driven forest canopy models should allow a vastly improve computation of surface water and carbon exchange rates by global forests and improve accuracy of global carbon and hydrologic budgets. Output from the project should be useful in understanding the regional-to-global dynamics of water, CO2 and climate with regard to the "greenhouse effect" as well as possibly providing better, more rapid means of estimating forest production on large scales. The investigators are quite well qualified. Institutional accommodations and support for both collaborators is excellent. The Ecosystem Studies Program recommends support for this three- year collaborative effort.

目前全球植被地图是由AVHRR卫星传感器的归一化植被指数（NDVI）生成的。这些地图与吸收的太阳辐射或表面叶面积指数有关，但NDVI仅在理论上与植被的蒸散发和光合作用过程有关，并且仅在最佳水和温度条件下相关，这些限制严重限制了现实世界的应用。该项目将利用完全由AVHRR数据驱动的简单的森林蒸散发和光合作用模型，该模型对次优水和温度条件很敏感。研究人员将(1)将每周复合NDVI的季节趋势与植被物候和温度限制联系起来，(2)测试卫星衍生的与冠层扩散阻力相关的地表阻力因子，(3)定义基于生理的碳和水的能量到质量的转换因子。然后，这些NDVI驱动的模型将根据更复杂的生态系统过程模型进行评估。由此产生的简单的、卫星驱动的森林冠层模型应该能够大大改进全球森林对地表水和碳交换率的计算，并提高全球碳和水文预算的准确性。该项目的产出应有助于了解水、二氧化碳和气候在“温室效应”方面从区域到全球的动态，并可能提供更好、更迅速的大规模估算森林产量的手段。调查人员是相当合格的。机构的安排和对双方合作者的支持是非常好的。生态系统研究计划建议支持这项为期三年的合作努力。