03 Dec 2021
03 Dec 2021
Status: this preprint is currently under review for the journal BG.

Improving the stomatal resistance, photosynthesis and two big leaf algorithms for grass in the regional climate model COSMO-CLM

Evgenii Churiulin1, Vladimir Kopeikin2, Markus Übel3, Jürgen Helmert3, Jean-Maria Bettems4, and Merja Helena Tölle1 Evgenii Churiulin et al.
  • 1Center for Environmental Systems Research, University of Kassel, 34117 Kassel, Germany
  • 2Hydrometcenter of Russia, 123242 Moscow, Russia
  • 3Deutscher Wetterdienst, 63067 Offenbach am Main, Germany
  • 4Federal Office of Meteorology and Climatology, Zurich, CH-8058, Switzerland

Abstract. Climatic changes towards warmer temperatures require the need to improve the simplified vegetation scheme of the regional climate model COSMO-CLM, which is not capable of modelling complex processes which depend on temperature, water availability, and day length. Thus, we have implemented the physically based Ball-Berry approach coupled with photosynthesis processes based on Farquhar and Collatz models for C3 and C4 plants in the regional climate model COSMO-CLM (CCLM v 5.16). The implementation of the new algorithms includes the replacement of the “one-big leaf” approach by a “two-big leaf” one. We performed single column simulations with COSMO-CLM over three observational sites with C3 grass plants in Germany for the period from 2010 to 2015 (Parc, Linden and Lindenberg domain). Hereby, we tested three alternative formulations of the new algorithms against a reference simulation (CCLMref) with no changes. The first formulation (CCLM3.5) adapts the algorithms for stomatal resistance from the Community Land Model (CLM v3.5), which depend on leaf photosynthesis, CO2 partial and vapor pressure and maximum stomatal resistance. The second one (CCLM4.5) includes a soil water stress function as in CLM v4.5. The third one (CCLM4.5e) is similar to CCLM4.5, but with adapted equations for dry leaf calculations. The results revealed major differences in the annual cycle of stomatal resistance compared to the original algorithm (CCLMref) of the reference simulation. The largest changes in stomatal resistance are observed from October to April when stomata are closed while summer values are generally less than control values that come closer to measured values. The results indicate that changes in stomatal resistance and photosynthesis algorithms can improve the accuracy of other parameters of the COSMO-CLM model (e.g.: transpiration rate or total evapotranspiration). These results were received by comparing COSMO-CLM parameters with FLUXNET data, meteorological observations at the sites, and GLEAM and HYRAS datasets.

Evgenii Churiulin et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on bg-2021-294', Sibyll Schaphoff, 04 Jan 2022
    • AC2: 'Reply on CC1', Evgenii Churiulin, 04 Feb 2022
  • CC2: 'Comment on bg-2021-294', Larisa Timofeeva, 28 Jan 2022
    • AC1: 'Reply on CC2', Evgenii Churiulin, 04 Feb 2022
  • RC1: 'Comment on bg-2021-294', Anonymous Referee #1, 31 Jan 2022
    • AC4: 'Reply on RC1', Evgenii Churiulin, 25 Mar 2022
  • EC1: 'Comment on bg-2021-294', Kirsten Thonicke, 09 Mar 2022
    • AC3: 'Reply on EC1', Evgenii Churiulin, 09 Mar 2022

Evgenii Churiulin et al.

Evgenii Churiulin et al.


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Latest update: 18 May 2022
Short summary
Our research is an important step towards a more realistic representation of vegetation in regional climate models. We have implemented in COSMO-CLM the new algorithms for stomatal resistance, leaf photosynthesis and two-big leaf. We applied the modern phenology algorithms of CLM model and fully adapted them for COSMO-CLM. The personal software was created for validation COSMO-CLM results. The research also brought out many tensions, which we are going to update in our next developments.