On Variability in Satellite Terrestrial Chlorophyll Fluorescence Measurements: Relationships with Phenology and Ecosystem-Atmosphere Carbon Exchange, Vegetation Structure, Clouds, and Sun-Satellite Geometry

Thursday, 18 December 2014: 11:20 AM
Joanna Joiner1,2, Yasuko Yoshida3, Luis Guanter4, Yongguang Zhang5, Alexander P Vasilkov3, Kevin M Schaefer6, Karl F Huemmrich1, Elizabeth Middleton1, Philipp Koehler5, Martin Jung7, Compton J Tucker1, Alexei Lyapustin1, Yujie Wang8, Christian Frankenberg9, Joseph A Berry10, Randal D Koster2, Rolf H Reichle11, Jung-Eun Lee12, Stephan R Kawa2, George James Collatz2, Gregory K Walker3 and Christiaan Van der Tol13, (1)NASA Goddard Space Flight Cen., Greenbelt, MD, United States, (2)NASA Goddard SFC, Greenbelt, MD, United States, (3)SSAI, Greenbelt, MD, United States, (4)Free University of Berlin, Berlin, Germany, (5)Freie Univ Berlin, Berlin, Germany, (6)University of Colorado, National Snow and Ice Data Center, Boulder, CO, United States, (7)Max Planck Institute for Biogeochemistry, Jena, Germany, (8)University of Maryland Baltimore County, Baltimore, MD, United States, (9)NASA Jet Propulsion Laboratory, Pasadena, CA, United States, (10)Carnegie Inst Washington, Washington, DC, United States, (11)NASA GSFC, Greenbelt, MD, United States, (12)Brown University, Providence, RI, United States, (13)ITC, Enschede, Netherlands
Over the past several years, there have been several breakthroughs in our ability to detect the very small fluorescence emitted by chlorophyll in vegetation globally from space. There are now multiple instruments in space capable of measuring this signal at varying temporal and spatial resolutions. We will review the state-of-the-art with respect to these relatively new satellite measurements and ongoing studies that examine the relationships with photosynthesis. Now that we have a data record spanning more than seven years, we can examine variations due to seasonal carbon uptake, interannual variability, land-use changes, and water and temperature stress. In addition, we examine how clouds and satellite viewing geometry impact the signal. We compare and contrast these variations with those from popular vegetation indices, such as the Normalized Difference Vegetation Index (NDVI), related to the potential photosynthesis as well as with measurements from flux tower gas exchange measurements and other model-based estimates of Global Primary Productivity (GPP). Vegetation fluorescence can be simulated in global vegetation models as well as with 1D canopy radiative transport models. We will describe how the satellite fluorescence data are being used to evaluate and potentially improve these models.