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Abstract
Vertical air speed plays an important role in several atmospheric processes like turbulent transport and cloud formation. During the IMPACT campaign in May 2008 at Cabauw, the Netherlands, several collocated systems were operated capable of sensing the vertical air speed with moderate to high temporal resolution. Amongst these systems were 1) sonic anemometers mounted in a 200 m high meteorological tower, 2) a 1.55 μm Doppler wind lidar, and 3) a 35 GHz cloudradar. The Doppler lidar was operated for a period of 7 days. The sonic anemometers measure the vertical speed with a temporal resolution of 0.1 s, the Doppler lidar tracks aerosols with diameter larger than 500 nm and with a vertical resolution of 50 or 200 m and time resolution of 10 or 20 s depending on the configuration. The cloudradar typical measures the speed of cloud droplets and particulate matter suspended in air with time resolution of 15 s and vertical resolution of 90 m .
We present three cases from this campaign and compare the observations of the different systems. A gravity wave event that occured in the night of 23 th of May proved to be very suitable to evaluate the performance of the systems. The vertical speed in this wave ranged from -0.2 m/s to +0.2 m/s, and the typical period of the wave is near 10 minutes. During the gravity wave event which exists for a about two hours, the air speed retrieved by the three systems compares very well. Also vertical winds observed in the convective boundary layer are compared. The scatter in the data between the systems is much larger in this case.