EGU General Assembly 2021
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Land-atmosphere coupling during compound extreme heat and drought events in the LUCAS experiment: a new coupling metric for climate extremes

Rita M. Cardoso1, Daniela D. C. A. Lima1, Pedro M. M. Soares1, Diana Rechid2, Marcus Breil3, Erika Coppola4, Edouard Davin5, Peter Hoffmann2, Lisa Jach6, Eleni Katragkou Katragkou7, Ronny Meier5, Priscilla A. Mooney8, Natalie de Noblet-Ducoudré9, Hans-Juergen Panitz3, Ioannis Sofiadis7, Susanna Strada4, Gustav Strandberg10, Merja Tölle11, and Kirsten Warrach-Sagi6
Rita M. Cardoso et al.
  • 1Instituto Dom Luiz, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal (
  • 2Climate Service Center Germany, Helmholtz-Zentrum Geesthacht, Hamburg, Germany
  • 3Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
  • 4International Centre for Theoretical Physics
  • 5ETH Zürich, Zürich, Switzerland
  • 6Institute of Physics and Meteorology, University of Hohenheim, Stuttgart, Germany
  • 7Department of Meteorology and Climatology, School of Geology, Aristotle University of Thessaloniki, Thessaloniki, Greece
  • 8NORCE & Bjerknes Centre for Climate Research
  • 9Laboratoire des Sciences du Climat et de l’Environnement, Gif-sur-Yvette, France
  • 10Rossby Centre, Swedish Meteorological and Hydrological Institute, Norrköping, Sweden
  • 11Center of Environmental Systems Research (CESR), University of Kassel, Germany

Land-atmosphere energy and water exchanges are fundamentally linked to soil-moisture. The distribution of the planets’ biomes hinges on the surface-atmosphere coupling since soil moisture and temperature feedbacks have a strong influence on plant transpiration and photosynthesis. Land use/land cover changes (LUC) modify locally land surface properties that control the land-atmosphere mass, energy, and momentum exchanges. The impact of these changes depends on the scale and nature of land cover modifications and is very difficult to quantify. However, large inconsistencies in the LUC impacts are observed between models, highlighting the need for common LUC across a large ensemble of models. The Flagship Pilot Study LUCAS (Land Use & Climate Across Scales) provides a coordinated effort to study LUC using an ensemble of regional climate models (RCMs). In the first phase of the project 3 experiments were performed for continental Europe: EVAL (current climate); GRASS (trees replaced by grassland) and FOREST (grasses and shrubs replaced by trees).  An analysis of the energy and moisture balance for the three experiments is performed, focusing on the relationship between the fluxes partitioning, heat waves and droughts. To better asses the link between extreme temperatures and soil moisture or evapotranspiration, a new coupling metric for short time scales is proposed, the Latent Heat Flux-Temperature Coupling Magnitude (LETCM). This new metric is computed for a specific period, considering the positive temperature extremes and the negative latent heat flux extremes. Areas with positive magnitude values imply higher temperature anomaly, due to a negative latent heat flux anomaly. This new metric only considers periods of strong coupling, with positive signals in areas of high temperatures and evaporative stress, allowing for the detection of events that are extreme for energy and water cycle. Concurrently, a new decile based normalised drought index is used to examine the concurrent heat extremes and droughts. The analysis focuses on the three experiments revealing that the number, amplitude and spatial distribution of compound extreme heat and drought is highly model dependant. The impact of afforestation or deforestation is not consistent across models.


 The authors wish to acknowledge project LEADING (PTDC/CTA-MET/28914/2017) and FCT - project UIDB/50019/2020 - Instituto Dom Luiz.

How to cite: Cardoso, R. M., Lima, D. D. C. A., Soares, P. M. M., Rechid, D., Breil, M., Coppola, E., Davin, E., Hoffmann, P., Jach, L., Katragkou, E. K., Meier, R., Mooney, P. A., de Noblet-Ducoudré, N., Panitz, H.-J., Sofiadis, I., Strada, S., Strandberg, G., Tölle, M., and Warrach-Sagi, K.: Land-atmosphere coupling during compound extreme heat and drought events in the LUCAS experiment: a new coupling metric for climate extremes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15797,, 2021.


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