1Climate Research, Finnish Meteorological Institute, P.O. Box 503,
00101 Helsinki, Finland
2Biochemical Integration Department, Max Planck Institute for
Biogeochemistry, Hans-Knöll-Str. 10, 07745 Jena, Germany
3Helmholtz-Centre Potsdam, GFZ German Research Centre for Geosciences,
Section 1.4 Remote Sensing, Telegrafenberg, 14473 Potsdam, Germany
4Atmospheric Composition Research, Finnish Meteorological Institute,
P.O. Box 503, 00101 Helsinki, Finland
5Department of Physics, University of Helsinki, 00014 University of
6University of Bologna, Via Zamboni, 33, 40126 Bologna, Italy
7Deparment of Water Resources, Faculty ITC, University of Twente, P.O. Box 217, 7500 AE Enschede, the Netherlands
Received: 25 Nov 2016 – Discussion started: 28 Nov 2016
Abstract. Recent satellite observations of sun-induced chlorophyll fluorescence (SIF) are thought to provide a large-scale proxy for gross primary production (GPP), thus providing a new way to assess the performance of land surface models (LSMs). In this study, we assessed how well SIF is able to predict GPP in the Fenno-Scandinavian region and what potential limitations for its application exist. We implemented a SIF model into the JSBACH LSM and used active leaf-level chlorophyll fluorescence measurements (Chl F) to evaluate the performance of the SIF module at a coniferous forest at Hyytiälä, Finland. We also compared simulated GPP and SIF at four Finnish micrometeorological flux measurement sites to observed GPP as well as to satellite-observed SIF. Finally, we conducted a regional model simulation for the Fenno-Scandinavian region with JSBACH and compared the results to SIF retrievals from the GOME-2 (Global Ozone Monitoring Experiment-2) space-borne spectrometer and to observation-based regional GPP estimates. Both observations and simulations revealed that SIF can be used to estimate GPP at both site and regional scales. At regional scale the model was able to simulate observed SIF averaged over 5 years with r2 of 0.86. The GOME-2-based SIF was a better proxy for GPP than the remotely sensed fAPAR (fraction of absorbed photosynthetic active radiation by vegetation). The observed SIF captured the seasonality of the photosynthesis at site scale and showed feasibility for use in improving of model seasonality at site and regional scale.
Revised: 02 Mar 2017 – Accepted: 09 Mar 2017 – Published: 11 Apr 2017
Thum, T., Zaehle, S., Köhler, P., Aalto, T., Aurela, M., Guanter, L., Kolari, P., Laurila, T., Lohila, A., Magnani, F., Van Der Tol, C., and Markkanen, T.: Modelling sun-induced fluorescence and photosynthesis with a land surface model at local and regional scales in northern Europe, Biogeosciences, 14, 1969-1987, doi:10.5194/bg-14-1969-2017, 2017.