18th Conference on Weather and Forecasting, 14th Conference on Numerical Weather Prediction, and Ninth Conference on Mesoscale Processes

Monday, 30 July 2001
Boundary Layer Turbulence and Surface Flux Parameterizations in a Mesoscale Model—verification with Aircraft Measurements
Qing Wang, NPS, Monterey, CA; and K. Rados, J. Kalogiros, H. Zuo, S. Wang, C. Friehe, D. Khelif, and H. Jonsson
There is a general lack of systematic evaluation of the surface flux and boundary layer parameterizations in mesoscale models largely due to inadequate observations for appropriate evaluations. During the Japan/East Sea Experiment (JES), intensive aircraft measurements were made using the Twin Otter research aircraft operated by the Center for Interdisciplinary Remote-Piloted Aircraft Studies (CIRPAS) of the Naval Postgraduate School (NPS). The Twin Otter measurements were made over the Japan/East Sea from late January and through February and obtained high-rate sampling of temperature, moisture, and the three-dimensional wind and turbulence over a wide range of meteorological conditions. In particular, multiple slant-path soundings were made along a vertical cross-section that can be used to characterize the vertical and horizontal variations of the marine boundary layer and the lower troposphere. This study will utilize the JES aircraft data for mesoscale model evaluation.

Numerical simulations using the Coupled Ocean and Atmosphere Prediction System (COAMPS) are made for several selected cases during the JES period when adequate measurements were available. The objective of this study is to understand the model behavior by direct inter-comparisons with observations for several cases and understand the model sensitivity to various parameters in the surface flux and boundary layer parameterization. One of the major findings of our study is the close interaction between the two components of the mesoscale model: the surface flux parameterization and the boundary layer parameterization. The surface sensible and latent heat fluxes are very sensitive to variables in boundary layer parameterization such as the formulation for boundary layer length scale. This strong sensitivity can be traced to modifications to boundary layer mean properties that are directly used in the surface flux calculations. Results on these sensitivity tests will be shown together with direct comparisons between the measured and simulated boundary layer height, mean vertical structure, and its variation along the flight track under different large-scale and boundary layer conditions.

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