Abstract:

The planetary boundary layer (PBL) regulates the exchange of momentum, heat, moisture, and pollutants between the Earth’s surface and the free atmosphere, making accurate identification of the PBL height critical for weather forecasting, air quality assessment, and climate studies. This project was motivated by the need to better understand both the physical basis and practical limitations of PBLH retrievals derived from Doppler wind lidar. Using airborne observations from the2023 Coastal Urban Plume Dynamics Study (CUPiDS) over the New York City region and ground-based measurements from the Pick-Up based Mobile Atmospheric Sounder(PUMAS) collected during the 2024 Airborne Methane Mass Balance Emissions in Colorado (AMMBEC) campaign along the Colorado Front Range, this study examined boundary-layer structure across urban, coastal, and continental environments. The analysis applied the Haar wavelet covariance method to range-corrected lidar intensity as a gradient-based approach for identifying the PBL top, alongside variance-based diagnostics, including vertical velocity variance and velocity azimuth display fit variance to characterize turbulence and flow heterogeneity. Results show that while Haar-based methods can reliably identify PBL transitions under ideal conditions, their performance degrades in the presence of clouds and multi-layered aerosol structure. Variance-based products provide valuable complementary context, with fit variance being a promising ,but underexplored diagnostic that qualitatively echoes established vertical velocity variance behavior. These findings contribute to improved understanding of foundational PBL height retrieval techniques and support the development of more robust approaches relevant to NOAA OAR’s role in developing and validating new measurement strategies and improving interpretation of complex observations for purposes of weather, air quality, and climate. The results presented are from the NOAA EPP/MSI CSC NERTO graduate internship project conducted under the mentorship of Brian Carroll and Steven Brown, Office of Oceanic and Atmospheric Research, Chemical Sciences Laboratory.