Seminari: "Assessing a dry soil layer parameterization for bare soil evaporation during the LIAISE campaign with the land surface model SURFEX-ISBA", per Belen Martí

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El proper dia 20 de març na Belen Martí presenta el seminari titulat "Assessing a dry soil layer parameterization for bare soil evaporation during the LIAISE campaign with the land surface model SURFEX-ISBA".


Land Surface Models (LSM) utilize standard meteorological measures in order to derive the turbulent fluxes that then may drive the weather prediction model and hydrological models. The latent heat flux or evapotranspiration indicates the exchange of energy through water phase change and is critical for the knowledge of water loss in semiarid regions that are characteristic for a deficit of water during a part of the year. These regions use irrigation as a means for crop management, as water becomes more scarce the proper estimation of evapotranspiration becomes critical.

Bare soil evaporation is mostly overestimated in LSM, this being one of the most relevant influencing factors for transpiration being underestimated globally (Chang et al. 2018). In this study we try to characterize the processes that drive bare soil evaporation by simulating evapotranspiration (ET) at two heavily instrumented sites from the Land surface Interactions with the Atmosphere over the Iberian Semi-arid Environment (LIAISE) campaign of summer 2021 by the means of ISBA-MEB land surface model within the SURFEX platform (Boone et al. 2017).

The first site was irrigated by flooding and contained alfalfa. The ground was nearly bare at the onset of a two-week period and covered by a 70 cm crop at the end of it, which allowed us to deduce the relative contributions of the ET components. The continuous change of LAI and vegetation height was considered, improving RMSE of ET against observation in over 25W/m² for the overall series. Still, bare soil evaporation was overestimated after irrigation when vegetation did not cover the ground and the soil was saturated and drying down. This process was better captured by the implementation of a soil resistance. Empirical resistances proved insufficient whereas the parameterization of soil resistance based on a dry surface layer (DSL) proved the better choice. Its implementation resulted on a 30% improvement in ET. The second site was dry natural grass, vegetation was continuous but not dense and mostly senescent. The predominant flux was the sensible heat flux with maximums of near 300W/m² and the ET average daily maximum was close to 50W/m². Bare soil evaporation was also overestimated and the implementation of a DSL reduced the overall ET error 20%. Finally, a DSL parameterization seems to improve bare soil evaporation in semiarid conditions where it is known to be overestimated systematically

El seminari serà a les 11h a l'Aula MOA12.


Fecha del evento: 20/03/2024

Fecha de publicación: 06/03/2024

Contenido en el idioma por defecto