Articles | Volume 14, issue 7
Biogeosciences, 14, 1969–1987, 2017
Biogeosciences, 14, 1969–1987, 2017

Research article 11 Apr 2017

Research article | 11 Apr 2017

Modelling sun-induced fluorescence and photosynthesis with a land surface model at local and regional scales in northern Europe

Tea Thum1, Sönke Zaehle2, Philipp Köhler3, Tuula Aalto1, Mika Aurela4, Luis Guanter3, Pasi Kolari5, Tuomas Laurila4, Annalea Lohila4, Federico Magnani6, Christiaan Van Der Tol7, and Tiina Markkanen1 Tea Thum et al.
  • 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 Helsinki, Finland
  • 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

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.

Short summary
Modelling seasonal cycle at the coniferous forests poses a challenge. We implemented a model for sun-induced chlorophyll fluorescence (SIF) to a land surface model JSBACH. It was used to study the seasonality of the carbon cycle in the Fenno-Scandinavian region. Comparison was made to direct CO2 flux measurements and satellite observations of SIF. SIF proved to be a better proxy for photosynthesis than the fraction of absorbed photosynthetically active radiation.
Final-revised paper