First Evaluation of HRRR Forecasts of Boundary Layer Thermodynamics across Contrasting

The dynamical and physiochemical processes taking place in the atmospheric boundary layer (ABL) significantly impact all major atmospheric phenomenon and mechanisms occurring on the timescales of weather, climate, and the bridging timescale of both. The ABL is a critical interface exchanging mass, energy, and momentum between surface and free troposphere via turbulence. The ABL, being the link between surface and large-scale atmosphere acts as a short-term “memory” of land-atmosphere interactions on diurnal timescales, governs the distributions of water vapor, aerosols, pollutants, greenhouse gases, and potential passive tracers, and plays an important role for the formation of clouds and convection initiation. Several efforts were made in the past to evaluate the potential of numerical weather prediction models and parameterization schemes to accurately simulate and predict ABL kinematics and thermodynamics over different land surfaces. Additionally, previous work has typically treated surface forcing and entrainment processes to be the key mechanisms governing ABL kinematics and thermodynamics, neglecting the horizontal advection of an airmass being “imported” on diverse spatial scales. Using high-resolution ground-based and airborne observations, for the first time, we will show some results on the impact of horizontal advection on regional-scale ABL features and evaluate the potential of HRRR forecasts across airmass boundaries during the passage of mid-latitude cyclones. This work aims to address the following research questions:

(1) What are the key advantages of weather-specific model evaluation approaches over traditional model data mismatch (MDM) experiments based on bulk statistics?

(2) How well a state-of-the-art NWP system (i.e., HRRR) can capture weather-scale modification of ABL features?

(3) What are the key factors that govern ABL thermodynamics across airmass boundaries?

To this end, we conducted ABL regime-specific MDM experiments for evaluating the performance of HRRR to examine the systematic errors in simulating of both kinematics and thermodynamics across airmass boundaries. Finally, this work will help identify needed improvements in simulating distinct impact of advection on ABL processes with an emphasis on determining where improvements in ABL parameterizations within mesoscale models are needed and create a conceptual framework for investigating role of advection on ABL features over land. New results are encouraging and suggest that weather-specific model evaluation approach will enable a detailed understanding of the impact of horizontal advection on meteorological processes occurring during synoptic-scale weather events.