Meteorological observations are essential in meteorology and climatology and are one of the core tasks of KNMI. The R&D Information and Observation Technology Division (I-RD) aims to continually improve KNMI’s observation infrastructure in order to keep it up-to-date and cost-effective.

Continuity and high quality of the meteorological surface observations are of crucial importance to stakeholders in weather, climate and aeronautical areas. The research activities within I-RD Observation Technology are necessary to understand the meteorological measurements from sensor to end product, including its calibration, underlying algorithms, validation, uncertainty and traceability to international standards.

KNMI is responsible for the operation of the national meteorological observation network in the Netherlands, which consists of about 45 automatic weather stations on the mainland and on the North Sea as well as airports and air bases. This network has been fully automated in the last two decades and currently the meteorological observations are made centrally available at least every 10 minutes. Various in-situ and remote sensing techniques are deployed to deliver surface observations of temperature, atmospheric pressure, humidity, wind, precipitation, radiation, visibility, present weather and clouds. In addition to the national observation network, scientific measurements at the Cabauw Experimental Site for Atmospheric Research (CESAR) are an important part of KNMI’s observation programme.

The introduction of new instrumentation requires extensive laboratory and field tests to investigate the characteristics and performance of the sensor under all meteorological conditions. Close collaboration in these tests with end users from different disciplines is important, in order to ensure that the new techniques meets their requirements.

The activities concerning surface observations involve:

• Specification, selection, evaluation and implementation of sensor replacements for operational sensors that are at the end of their life cycle.
• Evaluation of new measurement techniques with economical or quality advantages.
• Investigation of sensor behaviour and data processing in order to solve known shortcomings.
• Exploration of new sensors or data products that are a potential source of additional information.
• Advise on sensor and data products.

I-RD also participates in international committees, like WMO-CIMO and EUMETNET working groups.

Below are some specific KNMI activities where the I-RD surface observations team has recently been involved in.

• Operational test of sonic wind sensors as a potential cost-effective replacement of the traditional cup anemometer and wind vane.
• Scientific measurement setup for soil and radiation parameters at the Cabauw Experimental Site for Atmospheric Research (CESAR).
• Evaluation of a new hemispheric observation technique for cloud cover (NubiScope).

• Investigation into the improvement of automated precipitation type observations by using laser disdrometers.
• Setup of a national visibility standard for the calibration of forward scatter sensors.
• Studies on the use of backscatter profiles from LIDAR ceilometers for several purposes, like nowcasting of fog and low clouds and monitoring of mixing layer height and volcanic ash plumes.