Retrieval and global assessment of terrestrial chlorophyll fluorescence from GOSAT space measurements

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• 作者：Luis Guanter^a ; ^e ; ^{guanter@atm.ox.ac.uk} ; Christian Frankenberg^b ; Anu Dudhia^a ; Philip E. Lewis^c ; José ; G&oacute ; mez-Dans^c ; Akihiko Kuze^d ; Hiroshi Suto^d ; Roy G. Grainger^a
• 关键词：Fluorescence retrieval ; GOSAT-FTS ; Fraunhofer-line approach ; Singular vector decomposition ; Gross primary production ; Vegetation indices
• 刊名：Remote Sensing of Environment
• 出版年：2012
• 期刊代码：79_00344257
• 类别：ear
• 出版时间：June, 2012
• 卷：121
• 期：Complete
• 页码：236-251
• 文件大小：9171 K

摘要

The recent advent of very high spectral resolution measurements by the Fourier Transform Spectrometer (FTS) on board the Greenhouse gases Observing SATellite (GOSAT) platform has made possible the retrieval of sun-induced terrestrial chlorophyll fluorescence (F_s) on a global scale. The basis for this retrieval is the modeling of the in-filling of solar Fraunhofer lines by fluorescence. This contribution to the field of space-based carbon cycle science presents an alternative method for the retrieval of F_s from the Fraunhofer lines resolved by GOSAT-FTS measurements. The method is based on a linear forward model derived by a singular vector decomposition technique, which enables a fast and robust inversion of top-of-atmosphere radiance spectra. Retrievals are performed in two spectral micro-windows (鈭?#xA0;2-3 nm width) containing several strong Fraunhofer lines. The statistical nature of this approach allows to avoid potential retrieval errors associated with the modeling of the instrument line shape or with a given extraterrestrial solar irradiance data set. The method has been tested on 22 consecutive months of global GOSAT-FTS measurements. The fundamental basis of this F_s retrieval approach and the results from the analysis of the global F_s data set produced with it are described in this work. Among other findings, the data analysis has shown (i) a very good comparison of F_s intensity levels and spatial patterns with the state-of-the-art physically-based F_s retrieval approach described in Frankenberg et al. (2011a), (ii) the overall good agreement between F_s annual and seasonal patterns and other space-based vegetation parameters, (iii) the need for a biome-dependent scaling from F_s to gross primary production, and (iv) the apparent existence of strong directional effects in the F_s emission from forest canopies. These results reinforce the confidence in the feasibility of F_s retrievals with GOSAT-FTS and open several points for future research in this emerging field.