Description
Understanding the temporal and spatial variability of planetary boundary layer height (PBLH) across heterogeneous surface types is essential for quantifying the dispersion and chemical processing of surface emissions. Because emissions are entrained within the boundary layer, characterizing the PBL’s evolving structure—both in time and across land–water transitions—is critical for assessing how natural and anthropogenic sources influence air quality and human exposure.
We pursue two objectives: (1) quantify how PBLH evolves during the sunrise and sunset transition periods, when the boundary layer develops from stable to convective and decays back to stable, and (2) quantify how PBLH varies across land–sea interfaces at sites with varying coastal distance and water source at the coast. Completing these will allow for future evaluation of how these dynamical changes modulate boundary-layer chemistry, with emphasis on interactions involving surface-emitted organic material and multipollutant mixtures.
Our analysis leverages aerosol backscatter profiles from the Unified Ceilometer Network (UCN) sites across the United States. Profiles have ~10-min temporal and ~15-m vertical resolution and extend to ~15 km; we derive PBLH primarily below 4 km AGL. PBLH retrievals follow the automated common algorithm introduced by Caicedo et al. (2020)—a Haar wavelet covariance transform approach with quality control, precipitation/cloud screening, time-continuity constraints, and per-retrieval uncertainties—used as the basis for UCN operations. From these retrievals we will (a) build a searchable database to analyze PBLH variability on diurnal to interannual timescales and (b) implement automated, near-real-time PBLH production at UCN sites to support local and national applications.
To address coastal processes, we have begun this work focusing on UCN sites near shorelines. This region enables investigation of PBL structure and chemistry under complex source influences—including marine cargo activities, roadway traffic, and biogenic emissions—to disentangle their roles in shaping coastal urban air quality.
References:
Caicedo, Vanessa ; Delgado, Ruben ; Sakai, Ricardo ; Kneep, Travis ; Williams, David ; Cavender, Kevin ; Lefer, Barry ; Szykman, James. (2020). An Automated Common Algorithm for Planetary Boundary Layer Retrievals Using Aerosol Lidars in Support of the U.S. EPA Photochemical Assessment Monitoring Stations Program. Journal of Atmospheric and Oceanic Technology. https://doi.org/10.1175/JTECH-D-20-0050.1.
Delgado, Ruben ; Caicedo, Vanessa ; Taguba, Kent ; Niyas, Mohammed ; Roots, Maurice ; Demoz, Belay ; Sakai, Ricardo ; Moshary, Fred ; Lefer, Barry L. ; Krask, David ; Williams, David ; Szykman, James ; Cavender, Kevin ; Rivera, Kyle (2022) Unified Ceilometer Network: Aerosol Profiling for Air Quality and Meteorological Applications