Articles | Volume 11, issue 2
Geosci. Model Dev., 11, 771–791, 2018
Geosci. Model Dev., 11, 771–791, 2018

Model description paper 02 Mar 2018

Model description paper | 02 Mar 2018

Simulating damage for wind storms in the land surface model ORCHIDEE-CAN (revision 4262)

Yi-Ying Chen1,a,*, Barry Gardiner2, Ferenc Pasztor1,b, Kristina Blennow3, James Ryder1, Aude Valade4, Kim Naudts1,c, Juliane Otto1,d, Matthew J. McGrath1, Carole Planque5, and Sebastiaan Luyssaert1,e,* Yi-Ying Chen et al.
  • 1Laboratoire des Sciences du Climat et de l'Environnement (LSCE/IPSL), CEA-CNRS-UVSQ, Université Paris-Saclay, Gif-sur-Yvette, France
  • 2Institute National de la Recherche Agronomique (INRA), Villenave d'Ornon, France
  • 3Swedish University of Agricultural Sciences (SLU), Alnarp, Sweden
  • 4Institut Pierre Simon Laplace (IPSL), CNRS-UPMC, Paris, France
  • 5CNRM/GMME/VEGEO Météo France, Toulouse, France
  • anow at: Research Center for Environmental Changes (RCEC), Academia Sinica, Taipei, Taiwan
  • bnow at: Maritime Strategies International Ltd (MSI), London, England
  • cnow at: Max Planck Institute for Meteorology, Hamburg, Germany
  • dnow at: Climate Service Center Germany (GERICS), Helmholtz-Zentrum Geesthacht, Hamburg, Germany
  • enow at: Department of Ecological Sciences, Vrij Universiteit Amsterdam, Amsterdam, the Netherlands
  • *These authors contributed equally to this work.

Abstract. Earth system models (ESMs) are currently the most advanced tools with which to study the interactions among humans, ecosystem productivity, and the climate. The inclusion of storm damage in ESMs has long been hampered by their big-leaf approach, which ignores the canopy structure information that is required for process-based wind-throw modelling. Recently the big-leaf assumptions in the large-scale land surface model ORCHIDEE-CAN were replaced by a three-dimensional description of the canopy structure. This opened the way to the integration of the processes from the small-scale wind damage risk model ForestGALES into ORCHIDEE-CAN. The integration of ForestGALES into ORCHIDEE-CAN required, however, developing numerically efficient solutions to deal with (1) landscape heterogeneity, i.e. account for newly established forest edges for the parameterization of gusts; (2) downscaling spatially and temporally aggregated wind fields to obtain more realistic wind speeds that would represents gusts; and (3) downscaling storm damage within the 2500 km2 pixels of ORCHIDEE-CAN. This new version of ORCHIDEE-CAN was parameterized over Sweden. Subsequently, the performance of the model was tested against data for historical storms in southern Sweden between 1951 and 2010 and south-western France in 2009. In years without big storms, here defined as a storm damaging less than 15  ×  106 m3 of wood in Sweden, the model error is 1.62  ×  106 m3, which is about 100 % of the observed damage. For years with big storms, such as Gudrun in 2005, the model error increased to 5.05  ×  106 m3, which is between 10 and 50 % of the observed damage. When the same model parameters were used over France, the model reproduced a decrease in leaf area index and an increase in albedo, in accordance with SPOT-VGT and MODIS records following the passing of Cyclone Klaus in 2009. The current version of ORCHIDEE-CAN (revision 4262) is therefore expected to have the capability to capture the dynamics of forest structure due to storm disturbance on both regional and global scales, although the empirical parameters calculating gustiness from the gridded wind fields and storm damage from critical wind speeds may benefit from regional fitting.

Short summary
The inclusion of process-based wind-throw damage simulation in Earth system models has been hampered by the big-leaf approach, which cannot provide the canopy structure information that is required. We adapted the physics from ForestGALES to calculate CWS on large scales. The new model included several numerically efficient solutions, such as handling the landscape heterogeneity, downscaling spatially and temporally aggregated wind fields, and downscaling storm damage within the 2500 km2 pixels.