Boundary Layer Depth Variability Over Complex Terrain as Observed During the WFIP2

The Wind Forecast Improvement Project in Complex Terrain (WFIP2) took place in the Columbia River Basin of Oregon and Washington states from Fall 2015 to Spring 2017. This intensive field campaign deployed more than 100 instruments with the main goal of improving the forecast skill of Numerical Weather Prediction (NWP) models in complex terrain. The response of the planetary boundary layer (PBL) height to local and regional drivers in this complex terrain is one of the key variables in both observational studies and model simulations for the WFIP2 study.

To understand the PBL structure and its evolution in a complex terrain environment, we use Radar Wind Profiler (RWP) SNR measurements to derive the PBL depth at two WFIP2 sites. It is determined as the height of the maximum ratio of the SNR differences calculated above and below each range gate. The impact of higher temporal resolution PBL height estimates (5 min vs hourly) on understanding the coupling processes of the surface layer and the atmosphere is discussed. Observations made in the surface layer of energy and moisture fluxes, as well as 3-D wind velocities from sonic anemometers at various depths will be used for coupling physical phenomena at the surface in the complex terrain to observed and modeled PBL heights.