Recent research on meteorological observations and instrumentation at KNMI

Being the National Meteorological Service of The Netherlands, KNMI operates the national meteorological observing network. This network consists of about 30 land-based Automatic Weather Stations and 10 marine-based AWS's (on North Sea oil production platforms). Also, the observations at the Dutch airports (including Amsterdam Airport Schiphol and the Air Force) are the responsibility of KNMI. Furthermore, KNMI cooperates with the ministry of Transport, Public Works and Water Management regarding the meteorological observations along the coast and the major motorways. In order to continually improve the quality of these observations and to keep them up-to-date and efficient, research into new observation techniques and improvement of existing ones is an ongoing topic.

Some recent research topics are:

• Improvement of cloud (cover) observations. A scanning pyrometer has been evaluated, in order to improve on the automated cloud cover reports obtained by using cloud base data from ceilometers.

• Visibility standard. A visibility standard has been developed to calibrate the forward-scatter sensors used in the network. Field calibration of a reference forward-scatter sensor against a transmissometer has been implemented, according to ICAO regulations.

• Improvement of precipitation type detection. Precipitation type determined by the forward scatter sensors shows some weaknesses, e.g. around 0 °C and in detecting hail events. The performance of several other sensors, most notably two types of optical disdrometers, is evaluated.

The results of these (ongoing) studies will be shown.