Using an Airborne Doppler Wind Lidar to Evaluate Sampling and Data Processing Strategies Relevant to the PBL and a Future Space-based System

The lowest 200m of the Planetary Boundary Layer (PBL) is just one focus area of a more comprehensive series of multi-agency (NASA, ONR and NOAA) funded investigations of the PBL (mostly over water) using airborne Doppler Wind Lidars (ADWL), dropsondes and other remote sensing capabilities. For this paper, we concentrate on ADWL observations obtained by the NASA/LaRC’s Doppler Aerosol WiNd (DAWN) lidar flown on the NASA DC-8 during CPEX (2017).

We address the question of “What does an airborne or future space-based coherent Doppler Wind Lidar have to offer to investigations of the Marine Atmospheric Boundary layer (MABL)”? Starting with the airborne perspective, we have developed a PBL attribute toolbox that is designed to host algorithms for attributes listed in Table 1.

Table 1 SWA’s PBL Toolbox for deriving information from ADWL returns

Parameter	DWL derived attributes
Depth of PBL	Aerosols, wind shear, turbulence (multi-scale)
Sea state	Waves, foam, salt/water spray, surface current
Wind features	LLJs, OLEs
Cloud/PBL interactions	Cloud bases, inflows, outflows, precipitation estimates

Our focus in this paper is to use single shot processing of DAWN data to illustrate velocity and aerosol structures within the MABL. In addition, we will investigate the departure of the wind field a few meters above the ocean surface as compared to the log and power wind profiles frequently used to compute surface stress and fluxes. We will address the following questions:

• Does resolving MABL wind/aerosol structures with single shot DAWN processing below 200m suggest a means to parameterize PBL processes?
• How close to the ocean surface can we observe the winds with a 180nm lidar pulse (~ 30m Full Width Half Max (FWHM))?
• What is the “true” wind at the traditional 10 meter reference height over water in the presence of whitecaps?

Looking ahead to a space-based DWL designed for PBL observations, we use the DAWN data along with our Doppler Lidar Simulation Model to simulate the PBL coverage in both the horizontal and vertical directions and address related issues of representativeness and access to the PBL through cloud coverage.