Sensor Synergy to Study Land-Atmosphere Interaction: A Field Experiment at the Hohenheim Land-Atmosphere Feedback Observatory (LAFO) Covering the 2025 Growing Season

The Land-Atmosphere Feedback Initiative (LAFI, https://www.lafi-dfg.de), funded by the German Research Foundation (DFG), is an interdisciplinary consortium of researchers from atmospheric, agricultural, soil, hydrological, and neuroinformatic sciences dedicated to an improved understanding and quantification of land-atmosphere feedback processes, employing an innovative combination of advanced research methods. These processes are being investigated via unique synergistic observations and model simulations from the micro-gamma (» 2 m) to the meso-gamma (» 2 km) spatial scales, and across diurnal to seasonal time scales.  

The four main objectives of LAFI are:

• To analyze the relationships between surface fluxes and their driving variables using Machine-Learning tools in order to identify possible ways to overcome the limitations of Monin-Obukhov Similarity Theory,
• To better understand the partitioning and variability of surface fluxes above heterogeneous land surfaces in view of improving the experimental energy balance closure,
• To partition evapotranspiration (ET) by quantifying E and T from within crop stands during the vegetation period using observational and modeling approaches
• To quantify entrainment by identifying and describing the key processes in the convective boundary layer with the aim to unravel relevant relationships for an improved parameterization of entrainment fluxes in models.

The backbone of the LAFI research are the operational measurements at the GEWEX Land-Atmosphere Feedback Observatory (GLAFO, https://lafo.uni-hohenheim.de/en) at the University of Hohenheim in Stuttgart, Germany. The site represents a mixed farmland area in the Southern part of Germany. Within LAFI, the observatory program at Hohenheim was augmented by a number of innovative measurement techniques, most of which were operated continuously over the full growing season from the end of March to the end of October, 2025. Additionally, specific measurements were carried out during five intensive observation periods, each covering 3-5 days between April and August, 2025. The micrometeorological measurements focused on two stands covered with winter wheat and maize.

The following key techniques were applied:

• scanning lidar systems for 3D water-vapor, temperature, and wind measurements,
• Fiber-Optic Distributed Sensors (FODS) for simultaneous high-resolution horizontal and vertical temperature measurements in the soil, vegetation, and atmosphere,

• Uncrewed Aerial Vehicles (UAVs) for multispectral and microwave high-spatial resolution observations of the land surface,
• in-situ sensors for observing (partitioning) ET, including lysimeter, and eddy-covariance in combination with isotope measurements of water-vapor in the soil, roots, canopy, and atmosphere,
• in-situ networks of sensors for the profiling of other soil, canopy air space and plant variables such as matric potential, sap flow, leaf gas exchange (CO₂, H₂O) and stomatal control,
• scintillometers to link the local EC-based fluxes with the entrainment fluxes derived from the lidar synergy,

• Cosmic-Ray Neutron Sensing (CRNS) to capture integrated field scale soil moisture dynamics.

With this contribution we will outline the LAFI measurement setup and strategy, characterize the data availability over the measurement period and show first examples of a synergetic analysis and interpretation of the measurements.