About Cesar Observatory

Introduction

The Cesar Observatory is located in the western part of the Netherlands (51.971° N, 4.927° E) in a polder 0.7 m below average sealevel. At the site a large set of instruments is operated to study the atmosphere and its interaction with the land surface. The Cesar site is used for:

• Monitoring of long term tendencies in atmospheric changes,
• Studies of atmospheric and land surface processes for climate modeling
• Validation of space-borne observations
• The development and implementation of new measurement techniques
• Training of young scientists at post-doc, PhD and master level.

Three universities and five major research institutes collaborate in Cesar. It is the focal point of experimental atmospheric research in The Netherlands.

Site Description

A 213 m high mast was specifically built at the Cabauw site for meteorological research to establish relations between the state of the atmospheric boundary layer (ABL), land surface conditions and the general weather situation for all seasons. This site was chosen, because it is rather representative for this part of the Netherlands and because only minor landscape developments were planned in this region. Indeed the present surroundings of Cabauw do not differ significantly from those in 1972. The North Sea is more than 50 km away to the WNW. The nearby region is agricultural, and surface elevation changes are at most a few metres over 20 km. Within 40 km radius there are four major synoptic weather stations, among which is the regular radiosonde station at De Bilt (06260), ensuring a permanent supporting mesoscale network. Near the mast, the terrain is open pasture for at least 400 m in all directions, and in the WSW direction for at least 2 km. Farther away, the landscape is generally very open in the West sector, while the distant East sector is more rough (windbreaks, orchards, low houses). The distant North and South sectors are mixed landscapes, much pasture and some windbreaks. Therefore the highest mast levels have in all directions a long fetch of landscape roughness which is usefully similar to the roughness observed in the lower surface layer. The soil consists of 0.6 m of river-clay, overlying a thick layer of peat. The water table is about 1 m below the surface, but can be higher during wet periods.

On the mast itself no undisturbed measurements can be made below 20 m. Auxiliary 20 m masts are installed to the SE and the NW at sufficient distance from the mast foot building. On site are also well-kept observation fields for micrometeorological observations, including soil heat flux, soil temperatures and various radiation measurements (including a BSRN station). Remote sensing observations are mostly performed at the Remote Sensing Site located 300 m SSE of the main tower. A scanning X-band radar operated by Delft University of Delft is located on top of the tower.