Utilizing Airborne Doppler Wind Lidar Data to Characterize the Surface Layer Over the Ocean: Winds, Foam, sea Spray and Surface Currents

Utilizing line of sight (LOS) and single shot wind and aerosol backscatter (SNR) data collected by Airborne Doppler Wind Lidars (ADWL) over the last 5 years, we continue to advance a set of algorithms that can process the ADWL data with high resolution in the surface layer of the Marine Atmospheric Boundary Layer (MABL). To do this, we are using data collected by several different ADWLs: the Twin Otter Doppler Wind Lidar (TODWL) off the coast of California during the NSF/NCAR funded 2022 Sundowner Wind Experiment (SWEX) and earlier efforts in the eastern Pacific (2007-2018) and in the western Pacific during the 2008 TPARC as well as by NASA’s Doppler Aerosol WiNd (DAWN) lidar during four CPEX (Convective Processes Experiment) field campaigns conducted by NASA over the Atlantic and Pacific Oceans during 2017-2021.

Through examining and characterizing the vertical gradients in SNR and wind velocity data and coupled to various attributes of the different lidar pulses, these algorithms are allowing us to provide important information on the shape of the wind profile in the bottom 20 m as well as critical information on turbulence, sea spray, and sea foam during both light and high wind conditions

We continue to make advances in exploring the variability of the surface wind stress on scales of 10 – 1000 meters over water during calm and whitecap conditions off the California coast. Here we will provide a review of the improvements to our processing algorithms for ADWL data near the surface and also present the results of our recent efforts in establishing foam and sea spray coverage statistics, particularly in the presence of atmospheric rolls or organized large eddies which carry turbulence and aerosols from the near surface layer to the top of the mixing layer. In addition, we will show how surface currents in the top millimeters of the water can be measured with the ADWL and discuss the challenge of finding sources of truth for this truly surface current.