PNNL

Abstract

The Planetary Boundary Layer (PBL) height (PBLH) is essential for studying PBL and ocean-atmosphere interactions. Marine PBL is usually defined to include a mixed layer (ML) and a capping inversion layer. The PBLH is usually similar to ML height (MLH) but it can be much greater than MLH for decoupled PBL. The MLH can be estimated from the measurements of aerosol backscatter by the airborne High-Spectral-Resolution Lidar – Generation 2 (HSRL-2) using a wavelet-based algorithm. Here we evaluate the retrieved MLH from HSRL-2 by utilizing 506 co-located dropsondes during the Aerosol Cloud meTeorology Interactions oVer the Western Atlantic Experiment (ACTIVATE) field campaign from 2020 to 2022. First, we define and determine the MLH and PBLH from the temperature and humidity profiles of each dropsonde, and find that the MLH values from HSRL-2 and dropsondes agree well with each other, with a correlation of 0.66 and median difference of 18 m. In contrast, the HSRL-2 MLH data do not correspond to dropsonde-derived PBLH, with a median difference of -47 m. Therefore, we modify the current operational and automated HSRL-2 wavelet-based algorithm for PBLH retrieval. This decreases the median difference significantly to -8 m, demonstrating the potential of using HSRL-2 aerosol backscatter data to estimate both marine MLH and PBLH. Further data analysis indicates that these conclusions remain the same for cases with higher or lower cloud fractions, and for decoupled PBLs.