EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Model and Observation for Surface Atmosphere Interactions (MOSAI) project

Fabienne Lohou1, Marie Lothon1, Sophie Bastin2, Aurore Brut3, Guylaine Canut4, Frédérique Cheruy5, Fleur Couvreux4, Jean-Martial Cohard6, José Darrozes7, Jean-Charles Dupont5, Sébastien Lafont8, Romain Roehrig4, Carlos Román-Cascón9, and the MOSAI Team*
Fabienne Lohou et al.
  • 1Laboratoire d’Aérologie, CNRS, Université de Toulouse, Toulouse, France (
  • 2Laboratoire Atmosphère, Milieux, observations spatiales, CNRS, CNES, Versailles Saint-Quentin-en-Yvelines University, Paris, France.
  • 3Centre d'Etudes Spatiales de la Biosphère, CNRS, Université de Toulouse, CNES, Toulouse, France.
  • 4Centre National de Recherches Météorologiques, Université de Toulouse, Météo-France, CNRS, Toulouse, France.
  • 5Laboratoire de Météorologie Dynamique, CNRS, IPSL, Paris, France.
  • 6Institut des Géosciences de l’Environnement, CNRS, Université de Grenoble, Grenoble, France.
  • 7Géosciences Environnement Toulouse, CNRS, Université de Toulouse, CNES, IRD, Toulouse, France.
  • 8Interactions Sol Plantes Atmosphère, INRAE, Bordeaux, France.
  • 9Departamento de Física de la Tierra y Astrofísica. Universidad Complutense de Madrid, 28040 Madrid, Spain
  • *A full list of authors appears at the end of the abstract

The Global Energy and Water cycle Exchanges and World Climate Research Program have pointed out the importance of the land-atmosphere (L-A) coupling for weather and climate models. The Working Group on Numerical Experimentation survey on systematic errors established that the outstanding errors in the modelling of surface fluxes of momentum and sensible and latent heat is the second most important issue. Earth System Models (ESM) and Numerical Weather Prediction (NWP) systems often have large biases in their representation of surface-atmosphere fluxes when compared to observations. The detailed quantification and reduction of these biases are still on-going efforts in many modelling centres. The Models and Observations for Surface-Atmosphere Interactions (MOSAI) project aims at contributing to this effort.

The first step to achieve this objective is to conduct a fair and correct evaluation of the L-A interactions simulated by ESM and NWP models. This is based on (1) reliable references against which the simulated L-A exchanges can be evaluated, and (2) relevant comparison methods able to point out the ESM and NWP system weaknesses. These points define the two first scientific objectives of MOSAI project. The first scientific objective is to investigate and determine the uncertainty and representativeness of L-A exchanges measured over heterogeneous landscapes. Three one-year campaigns are planned to document this heterogeneity on three of the ACTRIS instrumented sites in France. The objective is to make these permanent fluxes measurements well documented in terms of uncertainty, surface energy imbalance and surface heterogeneity representativeness at the scale of the model grid-mesh. The second scientific objective is to propose and test two methods to evaluate the L-A exchanges in ESM using long-term measurements. The first approach is based on sensitivity studies performed with 3D models or with their corresponding single-column version, either forced by data from the MOSAI one-year campaigns or coupled with their LSM, and for which an atmospheric forcing will be derived from operational analyses. The second approach relies on Artificial Intelligence methods (Neural Network or Random Forest) to test the dependency of the surface fluxes to several meteorological variables, at the same time for observation and models. These two methods will allow identifying specific weaknesses of each model at different spatial and time scales.

The second step of the project concerns the improvement of the L-A exchanges simulated by ESM and NWP systems. The coupling between land surface models (LSM) and atmospheric models is based on several simplifications which are different when considering Large-Eddy Simulation (LES), weather or climate models. The third scientific objective of MOSAI project addresses some of these underlying simplifications in the coupling between LSM and atmospheric models, and their impacts on the simulated L-A exchanges. After determining the importance of a realistic heterogeneous landscape versus percentages of unified landscape to correctly simulate the surface flux in ESM and NWP, differential treatment of the boundary-layer parameterizations will be developed, so that the atmosphere model can describe as many sub-columns as the number of land-surface patches to explicitly represent the L-A coupling.


BAZILE Eric (4), BIRON Romain (6), BOONE Aaron (4), CHIRIACO Marjolaine (2), COULAUD Catherine (6), COULON Maelle (5), DARE-IDOWU Oluwakemi (3), DECHARME Bertrand (4), DERRIEN Solène (1), DUBOS Thomas (5), FERNANDES Royston (4), GARROUSTE Olivier (4), HOURDIN Frédéric (5), IRVINE Mark (8), JARLAN Lionel (3), JOME Mathilde (1), LE MOIGNE Patrick (4), MAUREL William (4), MEDINA Patrice (1), MENJOT Ludovic (7), MERCIER Bernard (6), MERLIN Olivier (3), MOREAUX Virginie (8), PRISCIA Oliva (7), RAMILLIEN Guillaume (7), SEITY Yann (4), SIMA Adriana (5), VIAL Antoine (1), ZOUZOUA Maurin (2)

How to cite: Lohou, F., Lothon, M., Bastin, S., Brut, A., Canut, G., Cheruy, F., Couvreux, F., Cohard, J.-M., Darrozes, J., Dupont, J.-C., Lafont, S., Roehrig, R., and Román-Cascón, C. and the MOSAI Team: Model and Observation for Surface Atmosphere Interactions (MOSAI) project, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8797,, 2022.