Journal cover Journal topic
Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/gmd-2018-17
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Model evaluation paper
27 Feb 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Geoscientific Model Development (GMD).
Closing the Energy Balance using a Canopy Heat Capacity – A physically based Approach for the Land Component JSBACHv3.11
Marvin Heidkamp1,2, Andreas Chlond1, and Felix Ament1,3 1Max Planck Institute for Meteorology, Hamburg, Germany
2International Max Planck Research School on Earth System Modeling, Hamburg, Germany
3Meteorological Institute, CEN, University of Hamburg, Germany
Abstract. Land surface-atmosphere interaction is one of the most important characteristic for understanding the terrestrial climate system, as it determines the exchange fluxes of energy and water between the land and the overlying air mass. In several current climate models, it is common practice to use an unphysical approach to close the surface energy balance within the uppermost soil layer with finite thickness and heat capacity. In this study, a different approach is investigated by means of a physical based estimation of the canopy heat capacity SkIn+.

Therefore, in a first step, results of an offline simulation of the land component JSBACH of the MPI-ESM – constrained with atmospheric observations – are compared to energy- and water fluxes derived from eddy covariance measurements observed at the CASES-99 field experiment in Kansas where only shallow vegetation prevails. This comparison of energy and evapotranspiration fluxes with observations at the site-level provides an assessment of the model's capacity to correctly reproduce the coupling between the land and the atmosphere throughout the diurnal cycle. In a further step, a global coupled land-atmosphere experiment is performed using an AMIP type simulation over thirty years to evaluate the regional impact of the SkIn+ scheme on longer time scale, in particular, in respect to the effect of the canopy heat capacity.

The results of the offline experiment show that SkIn+ leads to a warming during the day and to a cooling in the night relative to the old reference scheme, thereby improving the performance in the representation of the modeled surface fluxes on diurnal time scales. In particular: nocturnal heat releases unrealistically destroying the stable boundary layer disappear and phase errors are removed. On the global scale, for regions with no or low vegetation and a pronounced diurnal cycle, the nocturnal cooling prevails due to the fact that stable conditions at night maintain the delayed response in temperature, whereas the daytime turbulent exchange amplifies it. For the tropics and boreal forests as well as high latitudes, the scheme tends to warm the system.

Citation: Heidkamp, M., Chlond, A., and Ament, F.: Closing the Energy Balance using a Canopy Heat Capacity – A physically based Approach for the Land Component JSBACHv3.11, Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2018-17, in review, 2018.
Marvin Heidkamp et al.
Marvin Heidkamp et al.
Marvin Heidkamp et al.

Viewed

Total article views: 278 (including HTML, PDF, and XML)

HTML PDF XML Total Supplement BibTeX EndNote
207 62 9 278 14 9 13

Views and downloads (calculated since 27 Feb 2018)

Cumulative views and downloads (calculated since 27 Feb 2018)

Viewed (geographical distribution)

Total article views: 278 (including HTML, PDF, and XML)

Thereof 277 with geography defined and 1 with unknown origin.

Country # Views %
  • 1

Saved

Discussed

Latest update: 19 Jun 2018
Publications Copernicus
Download
Short summary
The heart and core of every climate model is the solution of the surface energy balance. Numerical (mathematical) approaches are mandatory to calculate the land's response to solar input. However, different numerical approaches should not affect the physical results. Thus, our aim is to develop a physical approach how the energy of the sun is divided into radiative and heat fluxes or stored in the soil. This approach leads to improvements especially for regions with no or low vegetation.
The heart and core of every climate model is the solution of the surface energy balance....
Share