Measuring the Surface Energy Balance at the Cabauw Observational Site

The surface energy balance (SEB) provides a physically consistent framework for interpreting land–atmosphere interactions based on the fundamental idea that energy exchange at the surface must be conserved. Accurately resolving the SEB and its constituent components is essential to better understand our climate and for developing and evaluating predictive models. However, it is well established that in many locations and conditions around the globe, the SEB does not close. The Royal Netherlands Meteorological Institute's (KNMI) Cabauw observational site forms a unique dataset to monitor and better understand the interactions between the surface and the atmosphere. Since 1972, this mid-latitude grassland has hosted various instruments performing a variety of relevant observations and is particularly distinguished by its 213 m tall mast. The long-term, near real-time profiles of standard measurements such as temperature, relative humidity, wind direction/speed, and visibility, provide an excellent foundation for scientific exploration. For instance, the neighbouring energy balance field (EB-field) is occupied by various instruments which measure each component of the SEB.

This poster provides an overview of these instruments and observational methods. Incoming and outgoing longwave and shortwave radiation at the EB-field are measured and combined to determine the net radiation. The net radiation is verified by comparing to the Cabauw Baseline Surface Radiation Network. The soil heat flux is determined via two methods using detailed profiles of soil temperature and soil heat flux plates. These observations have been particularly affected by sinking and are more difficult to verify. The sensible heat flux and latent heat flux can be derived from the turbulence measurements (3D sonic anemometer and open pathway sensor) and in addition, a psychrometer mast which measures air temperature and dewpoint temperature at 1, 2, and 4 m. In recent years, latent energy has also been measured directly at the surface using a lysimeter. These long-term and detailed measurements provide a unique opportunity to investigate both the SEB closure, and the processes that determine the exchange between the surface and atmosphere in great detail.