The EUMETSAT funded study validated satellite surface temperature products over Lake Constance and intercompared Fiducial Reference Measurements (FRM) from a Heitronics KT15.85 IIP radiometer and an Infrared Sea surface temperature Autonomous Radiometer (ISAR). The inter-comparison experiment was performed in September 2020 (COVID-19 pandemic) on the car ferry MS Friedrichshafen of the Bodensee-Schiffsbetriebe GmbH (BSB). The MS Friedrichshafen commutes all-year around between Friedrichshafen, Germany, and Romanshorn, Switzerland.

The inter-comparison enhanced our understanding of satellite derived Lake Water Surface Temperature (LWST) observations and measurements performed with shipborne infrared radiometers (Heitronics KT15.85 IIP and ISAR). Satellite-retrieved surface temperature products, in particular from Sentinel-3, were validated and the accuracy of KIT’s permanently obtained in-situ LWST verified.

Main activities were:

• Acquisition of an LWST dataset from two FRM radiometers operating in parallel
• Inter-comparison of in-situ LWST data and FRM radiometer uncertainties
• In-situ validation of TIR satellite surface temperature products and associated uncertainties