Ground-based lidar operational and research activities at KNMI

Over the past decade, the Royal Netherlands Meteorological Institute (KNMI) has undertaken significant effort to integrate emerging surface-based remote sensing technology in its services for operations and research. KNMI deploys several types of ground-based lidar instruments to detect clouds and volcanic ash, and measure vertical profiles of aerosols, wind and water vapor. Real-time information on the vertical structure of the atmosphere is becoming increasingly important input for nowcasting purposes and models supporting KNMI’s forecasting, climate, early warning, maritime, and energy tasks.

Since the late 1990’s KNMI deploys automatic lidar ceilometers (ALC) for continuous (24/7), fully automated observations of cloud base height and cloud cover. These ALCs are integrated in our nationwide automatic weather station network and currently consists of 45 stations, including civil and defense airports and North Sea platforms. ALC backscatter profile data provides aerosol layer information, including the boundary layer and elevated aerosol layers, allowing to monitor Sahara dust, wildfire smoke and volcanic ash. Those different types of aerosols can be differentiated with the Raman lidars at the Cabauw atmospheric research station, part of the Ruisdael Observatory and ACTRIS National Facility. One Raman lidar also measures vertical profiles of the water vapor mixing ratio. The KNMI ALCs are part of the European ALC network within E-PROFILE. Current research focuses on the real-time retrieval of boundary layer height from ALC backscatter data and its transition from research to operations (R2O). The ground-based lidars at Cabauw play a significant role in validation of space-born lidars, such as EarthCARE.

Since end 2010’s KNMI uses Doppler lidars that measure wind. The development of wind farms on the Dutch North Sea provided the opportunity to deploy short-range wind lidars offshore. The current network consists of 7 stations, within 4 wind farms. The measured wind profiles are made available to key users, including the wind farm operators and KNMI forecasters, in near-real time. At Cabauw, a long-range scanning Doppler lidar provides vertical profiles of horizontal wind and vertical velocity in the boundary layer, from which for instance low-level jets, mixing height and gravity waves are detected. It is part of the European DWL network within E-PROFILE. More recently, KNMI deployed a long-range scanning Doppler lidar for research and operational deployment at Amsterdam Schiphol Airport, supporting KNMI’s aviation services. Research includes the development of aircraft wake vortex persistence monitoring or alerting systems for dangerous wind phenomena such as wind shear or gust fronts.

Here we will present an overview of KNMI’s ground-based lidar activities, along with an outlook on future developments and opportunities.