Atmospheric Boundary Layer Observations at Cabauw in the Netherlands

The KNMI site Cabauw in the Netherlands with its 213 m meteorological tower has been a focus of experimental boundary layer research already since the 1970's. Since 2003 six national institutes, organized in the consortium CESAR (Cabauw Experimental Site for Atmospheric Research), joins their experimental atmospheric research on the Cabauw site. Here we focus on atmospheric boundary layer research in CESAR.

Recent developments in Climate Change issues have stimulated new research at Cabauw. Improved climate scenarios may rely, among others, on a better representation of stable boundary layers in climate weather models The GABLS working group is specially designed to address this issue and Cabauw observations play a role in the development and evaluation of such models. In the context of the Kyoto protocol and possible future extensions a comprehensive Dutch project is started to demonstrate the feasibility of a system to monitor greenhouse gas emissions and uptake on the national scale. The system consists of a combination of dedicated observations and inverse modelling techniques. In such a system the characterisation of the actual boundary layer structure and its representation in models plays an important role. Cabauw is one of the corner stones in this project. The improved quality and resolution of current atmospheric models together with detailed observation of the atmospheric column over Cabauw makes it feasible to interpret observation in terms of the boundary layer budgets of heat, water and possibly CO2 of the atmospheric boundary layer over Cabauw.

The boundary layer observations consists of radio soundings of the nearby station De Bilt, a windprofiler/RASS system, an aerosol lidar, a cloud radar system which among other products gives profiles of the structure parameter of temperature. A scintillometer is employed over a path of 10 km to obtain regional scale fluxes. Tower observations of wind, temperature, humidity and CO2 at various levels are performed. Three levels with turbulence equipment up to 180 operational. A surface energy budget station including all radiation components, soil heat flux and turbulent fluxes is stationed at the grassland site. A soil hydrological program is run in the polder surrounding Cabauw.