Scintillometer Measurements at the Hohenheim Land-Atmosphere Feedback Observatory

The turbulent fluxes of heat and water vapor are key land surface – atmosphere interaction process variables in local, regional, and global energy and water cycles. Scintillometry can be considered as the only experimental technique presently available for the operational determination of these fluxes at a horizontal scale of a few kilometers – measurements necessary to validate fluxes simulated by regional atmospheric models or derived from satellite images.

Scintillometers measure the fluctuations of electromagnetic radiation propagating horizontally over a path of typically a few hundred meters up to several kilometers in length. These signal intensity fluctuations can be attributed to fluctuations of the refractive index of the air, i.e., of temperature and humidity, caused by turbulent processes in the near-surface atmospheric boundary layer (ABL). Using similarity theory relationships, the turbulent heat fluxes can be derived. Combining an optical and a microwave scintillometer (OMS), the fluxes of both sensible and latent heat can be obtained.

An OMS system has been operated at the Land-Atmosphere Feedback Observatory site at the University of Hohenheim during the General Observations Period of the Land-Atmosphere Feedback Initiative cluster project over a period of eight months from mid-March to mid-November, 2025. The 1093 m long path covered different types of crops, including rape, maize, wheat, oat and soybean. These measurements were intended to provide flux values representing a heterogeneous agricultural landscape.

We will describe the data handling and processing of the scintillometer data for this quasi-operational setup. Derived fluxes are compared with local eddy-covariance measurements above two distinct fields below the scintillometer path. Moreover, an attempt will be made to relate the OMS-based fluxes with flux estimates from inside the ABL based on synergetic lidar measurements.