Derived Wind Profile Data from Doppler Lidar Ready for Review

Published: 26 February 2014
Height-time display of wind speed (colors) and direction (arrows) from the Doppler lidar at the Southern Great Plains site for October 4, 2012.

Vertically resolved wind measurements are crucial for numerical weather prediction and for modeling pollutant and aerosol transport. The scanning, coherent Doppler lidars operated by the ARM Facility have the capability of providing accurate, high-resolution wind measurements within the atmospheric boundary layer. A new Doppler lidar wind profile value-added product (VAP) is available as an evaluation product. This VAP ingests radial velocity data from plan-position-indicator (PPI) scans acquired by the ARM Doppler lidar systems and computes vertical profiles of horizontal wind speed and direction using a modified version of the traditional velocity-azimuth-display (VAD) algorithm.

The VAD algorithm produces estimates of horizontal wind vector from PPI scans by assuming the flow to be locally homogeneous. At any given height, the conical PPI scan traces out a circle centered above the lidar position. The components of the horizontal wind vector are estimated by fitting a sinusoid, or sine wave (mathematical curve), to the radial velocity data; the amplitude, phase, and offset of the sinusoid determine the wind speed, wind direction, and vertical velocity, respectively. Derived winds are representative of averages taken over the circumference of the circle and over the time it takes to complete a full PPI scan, which is typically 1 to 2 minutes. Wind profiles are computed within the lowest 3 km of the atmosphere with nominal height and time resolutions of 26 meters and 15 minutes, respectively.

As always, feedback and use of the data are welcomed and encouraged. For questions, or to report data problems, please contact principal investigators Rob Newsom or Laura Riihimaki.

To access the Derived Wind Profiles from Doppler Lidar VAP, log into the ARM Data Archive. Go here to request an account.