Boundary Layer Structures Over the Northwest Atlantic Derived From Airborne High Spectral Resolution Lidar and Dropsonde Measurements During the ACTIVATE Campaign

Abstract

The Planetary Boundary Layer Height (PBLH) is essential for studying the lower atmosphere and its interaction with the surface. Usually, it contains a mixed layer (ML) with vertically well-mixed (i.e., nearly constant) specific humidity and potential temperature. Over the ocean, the PBL is usually coupled (vertically well-mixed) and the ML height (MLH) is usually close to PBLH, hence the MLH estimated from the measurements of aerosol backscatter by a lidar is traditionally compared with PBLH determined from radiosondes/dropsondes. However, when the PBL is decoupled (not vertically well mixed), the MLH differs from the PBLH. Here we used dropsondes' thermodynamic profile to evaluate the airborne High-Spectral-Resolution Lidar—Generation 2 (HSRL-2) estimation of MLH and PBLH in airborne field campaign over the northwestern Atlantic (ACTIVATE) from 2020 to 2022. We show that the HSRL-2 has excellent MLH estimation compared to the dropsondes. We also improved the HSRL-2 estimation of PBLH. Further data analysis indicates that these conclusions remain the same for cases with different cloud fractions, and for decoupled PBLs. These results demonstrate the potential of using HSRL-2 aerosol backscatter data to estimate both marine MLH and PBLH and suggest that lidar-derived MLH should be compared with radiosonde/dropsonde-determined MLH (not PBLH) in general.