Cloud altimeter
The cloud altimeter or ceilometer measures the height of clouds (or multiple cloud layers) and the vertical visibility. This is done using short (laser) light pulses that are sent into the atmosphere. The cloud altimeter then measures the amount of reflected light.
The cloud altimeter uses the LiDAR principle.
The time difference determines the altitude and the intensity determines the concentration of particles (number of particles per volume) in the air. The cloud altimeter measures the 'cloud base'. This is the lowest zone above the Earth's surface where there is a change from clear, transparent air to air that is filled with water droplets or ice crystals and that is more or less opaque. The cloud altimeter can report a cloudless situation, cloud layers and an obstruction (that does not meet the criteria for cloud cover).
Data
The data collected with the cloud altimeter can be found in various places:
- Rijkswaterstaat Waterinfo and Rijkswaterstaat Waterberichtgeving provide access to the meteorological data of Landelijk Meetnet Water (LMW) (the National Water Monitoring Network).
- The LMW also sends the data directly to the KNMI data portal.
- The Digital North Sea Alliance website provides access to meteorological data for a number of wind farms in the North Sea.
Customers and applications
Customers include wind farm operators, energy traders, Rijkswaterstaat, the KNMI, skippers of Crew Transfer Vessels (CTVs), major seaports, (commercial) shipping, the Coast Guard, incident organizations and recreationists.
The data is used for climatological research, maritime research and the development, calibration and validation of models.