Global assessment of vegetation photosynthesis and carbon assimilation through space measurements of chlorophyll fluorescence

陆地植被光合作用的总碳吸收率是气候变化研究中的一个重要参数。生态系统初级生产总值的全球观测特征只能通过卫星测量来实现。然而，传统的空间植被描述是基于所谓的光谱植被指数，无法提供可靠的光合效率驱动植被碳同化的指示。这导致现有卫星产品在提供生态系统功能的准确描述方面存在固有的局限性。相比之下，仪器设计和建模方法的持续发展最近使从空间测量中检索植被叶绿素荧光成为可能。大量的实验室和实地实验表明，荧光是植被光利用效率的直接代表，因此可以更准确地描述初级生产总值。本项目建议设立一个研究小组，重点研究现有和即将开展的地球观测任务对叶绿素荧光的全球监测和解释。这项任务将意味着开发各种大气-地表辐射转移建模方法、数据处理、检索技术和生态系统建模工具，最终目标是开发一种从空间观测植被碳同化的新方法。

The gross carbon uptake of terrestrial vegetation through photosynthesis is a crucial parameter in climate change research. A global, observation-based characterisation of ecosystem gross primary production can only be performed with satellite measurements. However, the traditional description of vegetation from space is based on the so-called spectral vegetation indices, which are not able to provide a reliable indication of photosynthetic efficiency driving carbon assimilation by vegetation. This results in an inherent limitation of existing satellite products to provide an accurate description of ecosystem functioning. By contrast, ongoing developments in instrument design and modelling approaches have very recently made possible the retrieval of vegetation chlorophyll fluorescence from space measurements. A vast number of laboratory and field experiments have demonstrated that fluorescence is a direct proxy to vegetation light use efficiency which can therefore enable a much more accurate description of gross primary production. This project proposes the implementation of a research group with focus on the global monitoring and interpretation of chlorophyll fluorescence from existing and upcoming Earth Observation missions. This task will imply the development of a variety of atmospheric-surface radiative transfer modelling approaches, data processing, retrieval techniques and ecosystem modelling tools, with the ultimate objective of developing a new approach to the observation of carbon assimilation by vegetation from space.