Exploring Mesoscale Variability of Water Vapor, Aerosol, Clouds, and Dynamics over West Coast Mountains Using Airborne Lidar Observations

The new HALO four-wavelength water vapor DIAL was deployed on the NASA DC-8 over the US west coast out of NASA Armstrong within the field phase of ADM Cal/Val Experiment during April 2019. HALO collected high-resolution measurements of water vapor profiles for more than 45 flight hours under varying atmospheric conditions. The key objectives were to demonstrate the capability to tune transmitter to adapt to varying atmospheric water vapor column amounts and feasibility of state-of-the-art laser transceivers on small, high-altitude NASA airborne platforms. A number of research flights were conducted over marine boundary layer, coastal regions of California and over the complex terrains of the Sierra Nevada Mountains and west slopes of the Rockies. These data sets provided us a unique opportunity to explore a myriad of atmospheric processes triggering mesoscale variability of water vapor, aerosol and cloud structures over the region. The HALO transceiver is capable of rapid reconfiguration to support H2O/HSRL or CH4/HSRL or H2O/CH4 missions. Within this contribution, we emphasize on the combined H2O and HSRL measurements obtained during the aforementioned ADM cal/val field experiment. In particular, this mission served as the maiden test flights for the HALO water vapor DIAL/HSRL configuration.

Several applications are discussed: Study of the moisture advection over complex terrains along the US west coast mountains, modulation of spatial variability of moisture field within and above the remarkably deep (2800 m AGL) moist convective boundary layer, moisture modifications inside the boundary layer via orographic lifting, mountain waves, and intrusion of very dry (mixing ratio of 0.3-0.4 gkg^-1) tongues into the boundary layer, and moisture advection during the internal boundary layer development and associated meso and local scale variability in humidity field. Finally, the potential of combined measurements of (1) DIAL derived water vapor mixing ratio, (2) HSRL derived optical properties of aerosol particles (backscatter and extinction coefficient, depolarization and lidar ratio), mixing layer heights, residual layer heights, and other potential aerosol layers in the free troposphere, and (3) Doppler wind lidar (onboard the same platform) retrieved wind vectors will be used to study boundary layer moisture regimes and associated vertical and horizontal transport processes over land-water interface across the Pacific Coast and over complex terrain during the April 2019 flight campaign.