Evaluation of NWS Operational Weather Model Planetary Boundary Layer Heightsusing the Unified Ceilometer Network

The Planetary Boundary Layer Height (PBLH) is a useful measure of the amount of mixing in the lower atmosphere near the ground surface. Boundary layer mixing contributes to the distribution of atmospheric pollutants and air quality that impacts human health. The extent of mixing is also controlled by surface heating driven by incoming radiation. The summer of 2023 saw some of the most extreme Canadian wildfires and resultant smoke affecting the U.S. This study aims to evaluate the National Weather Service’s (NWS) National Centers for Environmental Protection (NCEP) Numerical Weather Prediction (NWP) model PBLH during these events using the Unified Ceilometer Network (UCN) and other available instruments. PBLH can be derived from ceilometers and other lidars from its measurements of aerosol backscatter.

The National Air Quality Forecast Capability (NAQFC) is comprised of chemistry from the EPA Community Model for Air Quality (CMAQ) driven by the NWS Global Forecast System physics either coupled in an offline fashion as done in operational Air Quality Model (AQM)v6 or Online as in the experimental Online-CMAQ AQMv7. In addition, NCEP runs the Rapid refresh Atmospheric Prediction (RAP) and High Resolution Rapid Refresh (RRFS) which includes wildfire and agricultural fire smoke. AQMv6 and AQMv7 do not include smoke radiation impacts on weather and resultant boundary layer mixing, however RAP and HRRR do. This study also aims to understand the impact of including smoke feedbacks to radiation on the PBLH.

Finally, NWS/NCEP also runs the operational Global Ensemble Forecast System (GEFS) Aerosols system that includes aerosols in an online fashion as well as the experimental Unified Forecast System (UFS) Aerosols both run at similar 25 km horizontal resolution. The latter includes aerosol radiation feedback with other improvements. Therefore, it may be useful to evaluate any improvements in PBLH provided from the UFS-Aerosols.