Observations and Simulations of Diurnal Coastal Low-Level Jets during the IMPOWR Field Experiment
This IMPOWR dataset can be used to verify these LLJs and low-level thermodynamic structures within a mesoscale model, and it provides a dataset to document the three-dimensional evolution of these LLJs. The Weather Research and Forecasting (WRF-ARW) model was used to simulate these LLJ cases down to 1.33-km grid spacing using the NCEP Rapid Refresh analyses for initial and boundary conditions. Both sets of simulations used Thompson microphysics, Dudhia shortwave radiation, and no cumulus parameterization, while several different PBL parameterizations were attempted. This study will focus on comparing the non-local first-order YSU and local TKE-order MYJ PBL parameterizations. The structure of the momentum, thermal, and turbulence fields were compared between model and observations for several flight legs and for vertical profiles from 20 – 30 m above the surface to about 1000 m. Preliminary results show that the WRF-simulated LLJ was both too weak (~3 m s-1) and too shallow (~50 m) for the 23 June 2013 case. Additional WRF simulations tested the effect of prescribed sea-surface temperatures to show that, while the depth of the marine atmospheric boundary layer (MABL) and strength of the inversion depends on SST, the LLJ magnitude is not as sensitive to uncertainties in the SST field as the atmospheric initial and lateral boundary conditions used in the simulations.