Lidar Uncertainty Measurement Experiment (LUMEX) – Profiling lidar Intercomparisons

Coherent Doppler lidar can provide profiles of wind speed, wind direction, vertical velocity, and fluctuations in horizontal wind speed representative of atmospheric turbulence, among other quantities critical for boundary-layer meteorology, wind energy, and air pollution studies. Toward characterizing the uncertainty associated with these measurements, the Lidar Uncertainty Measurement Experiment (LUMEX) was conducted at Erie, Colorado from 23 June to 13 July 2014. Choukulkar et al. (2015), another submission to this session, will present an overview of this experiment.

One aspect of LUMEX was an assessment of the uncertainties associated with profiling Doppler lidars such as the WINDCUBE lidar, a commercial product widely used in wind energy. For several days during LUMEX, two WINDCUBE version 1 lidars were collocated with the NOAA High Resolution Doppler Lidar (HRDL). As will be presented, the agreement between the two WINDCUBE instruments strongly depends on the strength of the lidar backscatter, as is the agreement between either WINDCUBE and the HRDL.

To further characterize WINDCUBE uncertainty, subsequently, one of the WINDCUBEs was moved close to the Boulder Atmospheric Observatory (BAO), a 300-meter high meteorological tower instrumented with sonic anemometers every 50 meters from 50 meters above the surface to 300 meters above the surface. This presentation will compare wind speeds and directions from the sonic anemometers and the WINDCUBE as well as metrics of turbulence, including turbulence intensity and turbulence kinetic energy. Previous studies have found that vertical velocity fluctuations are subject to large error, particularly during stable conditions; this hypothesis will be tested.

Finally, the two WINDCUBE lidars were separated by distances of 500 m to 4 km, whilst still near the BAO, to quantify the heterogeneity of the flow in a region with relatively small topographic variations. This presentation will also present the observed variability toward quantifying uncertainty.