Multi-objective calibration of the land surface scheme TERRA/LM using LITFASS-2003 data

Abstract

The turbulent sensible and latent heat fluxes as simulated in the operational weather forecast model LM are verified with data from the field experiment LITFASS 2003 (LITFASS=’Lindenberg Inhomogeneous Terrain – Fluxes between Atmosphere and Surface: a Long-term Study’) both with the single site measurements and the grid box aggregated fluxes. The SCE-UA (single objective) and the MOSCEM-UA (multi objective) approaches are applied to calibrate the land-surface scheme TERRA/LM for 11 single sites and for the aggregated fluxes. A large variation is seen among the parameter sets found by calibration and no typical classification according to vegetation type is obvious. This is due to the fact that the calibrated parameter sets correct for model deficiencies and data errors rather than describe the physical characteristics of the measurement site. The measured fluxes are combined to a time series of aggregated fluxes by the tile method. Calibration of TERRA/LM with respect to the averaged fluxes results in a range of parameter sets which all allow the simulation of the area averaged fluxes with much better agreement to the observed fluxes than the standard parameter set of the operational model. A modified Nash-Sutcliffe measure as a coincidence criterion is reduced from 0.3 to the range between 0.15 and 0.28 for the latent heat flux and from 0.43 to between 0.26 and 0.36 for the sensible heat flux when using the calibrated parameter sets instead of the standard parameters.