The climate system is complex. Although it is understood in qualitative terms, there are still many physical processes of which the impact on climate change is far from quantifiable. A well-known example of such a process is the interaction between cloud and rainfall formation, aerosols, radiation and the land-atmosphere energy exchange. It is one of the sources of large uncertainty in climate models. The uncertainty is largely due to a lack of reliable observations of the processes. In this project we aimed at the development of the required observation methodologies to study these processes. We explored and enhanced the capacity of CESAR Observatory, in the heart of the Netherlands, in order to make it one of the leading atmospheric observatories in the world. In particular, we defined:

• New technologies: advanced radar and lidar systems were developed and installed at the observatory
• Quality improving enhancements of the observatory
• New retrieval techniques to derive the relevant atmospheric parameters
• The data base infrastructure of CESAR Observatory
• Evaluation studies to assess the quality and consistency of the observations
• Studies to assess the potential impact of new observations on model output

The major outcome of the project is the observatory itself. We now have a world class observatory for atmospheric studies. It is one of the few stations worldwide with which one can study climaterelevant processes in the context of atmospheric chemistry, physics, hydrology and meteorology. The CESAR database is easily accessible to the scientifi c community. CESAR Observatory is one of the major research facilities in The Netherlands. It serves the atmospheric community at seven research institutes and agencies: the universities of Delft, Wageningen and Utrecht, ECN Energy Research Centre of The Netherlands, TNO Applied Scientifi c Research, RIVM National Institute for Public Health and the Environment, and KNMI Royal Netherlands Meteorological Institute. Furthermore, the observatory is also supported by European Space Agency. The observatory is hosted and operated by the KNMI. CESAR data are used for a wide range of applications, e.g.:

• Monitoring of long term tendencies of climate variables in the atmosphere
• Validation of space-borne observations and retrieval products
• Studies of atmospheric and land surface processes for climate and air quality modelling
• Evaluation of weather, climate and air quality models
• The development, implementation and assessment of new measurement techniques
• Training of young scientists at post-doc, PhD and master level

An important advantage of the site is its location: both close to the sea and to some of the major European industrial and populated areas. This location leads to a large variety of air mass types at the site. Other advantages are its long term dataset of advanced parameters, the coinciding location of the different instruments, and the area around the site, which is flat and has suffered only minor landscape developments since 1972. 

Read more: synthesis report
Contact: project CS02