The Land-Atmosphere Feedback Initiative (LAFI): Field observations, modeling approaches, and first results

Land-atmosphere (L-A) feedback plays a key role in the evolution of Earth’s weather and climate system. However, the understanding and simulation of land-atmosphere interaction still suffers from severe limitations and errors. For instance, Abramowitz et al. (2024) demonstrated that the simulation of surface fluxes by land-atmosphere models, irrespective of their complexity, strongly deviates from observations. Similarly, Monin-Obukhov Similarity Theory (MOST) seems to be inadequate (Wulfmeyer et al. 2023) for the parameterization of evapotranspiration, but is nevertheless used in almost all coupled land-atmosphere system models.  

The overarching goal of LAFI is to understand and quantify L-A feedbacks via unique synergistic observations and model simulations from the micro-gamma (» 2 m) to the meso-gamma (» 2 km) scales across diurnal to seasonal time scales. In this presentation, we give an overview of the objectives and the current results of LAFI with respect to the understanding of surface-layer flow and fluxes, the energy balance closure (EBC), and entrainment over heterogenous agricultural terrain. More insight will be gained by the LAFI field campaign, which will be performed from Spring to Autumn 2025 at the Land-Atmosphere Feedback Observatory (LAFO) of the University of Hohenheim. The LAFI field campaign will enhance the current sensor synergy at LAFO, in order to capture key variables more fully within the soil, vegetation, and atmosphere compartments (Späth et al. 2023). Highlights of the new LAFI instrumentation include water-vapour isotope sensors, sap-flow sensors, fiber-optical distributed sensors (FODS, Thomas and Selker, 2021),unmanned aerial vehicles (UAVs), and scanning water-vapor, temperature, and wind lidar systems. We demonstrate how these measurements complement each other to gain new insights into flux-driver relationships, soil evaporation, crop transpiration, and entrainment, as well as the impact of land-surface heterogeneities and dispersive fluxes on the EBC. The very first results of this campaign will also be presented. 

 

References: 

Abramowitz et al. 2024: https://bg.copernicus.org/articles/21/5517/2024 

Späth et al. 2023: https://doi.org/10.5194/gi-12-25-2023 

Thomas, C.K., Selker, J.S., 2021. https://doi.org/10.1007/978-3-030-52171-4_20 

Wulfmeyer et al. 2023: https://link.springer.com/article/10.1007/s10546-022-00761-2