Evaluating Airborne High Spectral Resolution Lidar Retrievals Of Mixed Layer Heights Using Dropsonde Data From The Activate Campaign Over The Northwest Atlantic Ocean
Presenter: Yike Xu1
Co-Author(s): Brandon Mitchell, Rodrigo Delgado, Amir Ouyed, Richard Ferrare, Johnathan Hair, Chris Hostetler, Amy Jo Scarino, Armin Sorooshian, Kenneth Lee Thornhill
Advisor(s): Dr. Xubin Zeng
1Department of Hydrology and Atmospheric Sciences, University of Arizona
The Planetary Boundary Layer (PBL) acts as the bridge linking (land, ocean, and ice) surface processes to the free troposphere. Its height is essential for studying PBL and surface-atmosphere interactions. The PBL over land (during the day) and ocean usually includes a mixed layer (ML) and a capping inversion layer, and the ML height (MLH) is usually used to represent PBL height (PBLH). However, when PBL contains thick clouds or are decoupled , these two heights differ. The airborne High-Spectral-Resolution Lidar – Generation 2 (HSRL-2) retrieved the MLH using a wavelet-based algorithm, followed by human revision, over the Northwest Atlantic Ocean during NASA’s Aerosol Cloud meTeorology Interactions oVer the western ATlantic Experiment (ACTIVATE) in 2020 and 2021. The goal here is to evaluate the MLH data using over 400 dropsondes during the ACTIVATE and explore the possibility of also retrieving the PBLH using the HSRL-2 backscatter data. First, we determine the MLH and PBLH for each dropsonde using a traditional method based on the vertical profiles of thermodynamic variables (most of the time) and expert judgment (for special situations). Comparison of collocated MLH data from HSRL-2 and dropsondes indicates that they agree with each other well, with a correlation of 0.77 and a mean absolute error of 186 m. In contrast, the HSRL-2 MLH data differ much from the dropsonde PBLH data (e.g., with a mean absolute error of 246 m). Further analysis indicates that the HSRL-2 initial retrieval of MLH (without the human revision) would perform better in comparison with the dropsonde PBLH. Motivated by this finding, we have slightly revised the wavelet-based retrieval to further improve the HSRL-2 retrieval of PBLH (e.g., with a mean absolute error of 189 m).