The Optical Autocovariance Wind Lidar. Part II: Green OAWL (GrOAWL) Airborne Performance and Validation Journal of Atmospheric and Oceanic Technology

A two-look airborne Doppler wind lidar operating at the 532-nm laser wavelength, the Green Optical Autocovariance Wind Lidar (GrOAWL), was built and flown aboard the NASA WB-57 research aircraft. Flight campaign goals were to validate the instrument wind measurements and to demonstrate the two-look measurement concept proposed for spaceborne mission concepts such as the Atmospheric Transport, Hurricanes, and Extratropical Numerical Weather Prediction with the Optical Autocovariance Wind Lidar (ATHENA-OAWL) mission. The GrOAWL-measured winds were compared with collocated dropsonde measurements. Line-of-sight velocity (LOSV) measurements for the individual GrOAWL looks showed excellent agreement with dropsondes (R-2 > 0.9). The LOSV biases were very small and not statistically different from 0 m s(-1) at the 95% confidence interval (-0.07 +/- 0.07 m s(-1) and 0.01 +/- 0.07 m s(-1) for look 1 and look 2, respectively). The wind speed and direction profiles retrieved by combining the two GrOAWL looks were also in very good agreement (R-2 > 0.85). An instrument performance model indicated the instrument wind measurement precision was likely lowered (uncertainty was increased) by a factor of similar to 3.3 during the flights relative to predicted as built instrument performance. The reduced performance was not observed during ground-based atmospheric testing and thus has been attributed to impacts of the harsh operating conditions of the WB-57 aircraft (high vibration, thermal gradients, and high humidity). The exercise of scaling the GrOAWL instrument performance and grid scale to space showed space-based OAWL wind measurements would yield products with precision at least as good as the GrOAWL instrument. 2018 OAR (Oceanic and Atmospheric Research) ESRL (Earth System Research Laboratory) CSL (Chemical Sciences Laboratory) CIRES (Cooperative Institute for Research in Environmental Sciences) Submitted http://dx.doi.org/10.1175/jtech-d-18-0025.1 CC BY 1955