A Case for a Combined Mesoscale and Climate Model Boundary Layer Parameterization Improvement Project

Routine surface observations from mesoscale networks and data from a 125-m and several 60-m meteorological towers in south-central Washington State are used to validate a variety of boundary layer parameterizations in mesoscale forecast ensembles over the U.S. Pacific Northwest. The land-sea contrast, complex terrain, and land-surface inhomogeneity of this region present major challenges to predictions of surface variables and boundary layer structure throughout the diurnal cycle. State-of-the-art mesoscale models have overall difficulty maintaining shallow cold pools and handling nocturnal stable layers. Several boundary layer parameterizations poorly model the daytime mixed-layer depth. All of these deficiencies have serious ramifications for public weather, air quality, and wind energy forecasts.

Boundary layer prediction deficiencies should also be analyzed with a climate perspective, since many problems cannot be diagnosed from short-term, mesoscale forecast errors. The feedback of boundary layer prediction error into the free-stream flow can only be rigorously tested with climate model simulations. Therefore, complementary evaluations of boundary layer parameterizations with both mesoscale and climate models may be necessary. We present a case for a unified boundary layer parameterization improvement effort that uses both community mesoscale and climate models as testbeds.