Objectively determined fair-weather NBL features in ARW-WRF and their comparison to CASES-97 observations

Heights of nocturnal boundary layer (NBL) features are determined using vertical profiles from the Advanced Research Weather Research and Forecasting Model (ARW-WRF), and then compared to data for three moderately windy fair-weather nights during the April–May 1997 Kansas-based Cooperative Atmosphere–Surface Exchange Study (CASES-97) to evaluate the success of four PBL schemes in replicating observations. The schemes are Bougeault–LaCarrere (BouLac), Mellor–Yamada–Janjić (MYJ), quasi-normal scale elimination (QNSE), and Yonsei University (YSU) versions 3.2 and 3.4.1.

This study's chosen objectively determined model NBL height h estimate uses a turbulence kinetic energy (TKE) threshold equal to 5% , where TKE′ is relative to its background (free atmosphere) value. The YSU- and MYJ-determined h could not be improved upon. Observed heights of the virtual temperature maximum hTvmax and wind speed maximum hSmax, and the heights h1wsonde and h2wsonde, between which the radiosonde slows from ~5 to ~3 m s⁻¹ as it rises from turbulent to nonturbulent air, and thus brackets h, were used for comparison to model results.