An Improved Mellor Yamada Level-3 Model with Condensation Physics: Its Design and Verification
Abstract
A computational scheme for an improved Mellor-Yamada(M-Y) Level-3 model with condensation physics is proposedand its performance is examined against large-eddy-simulationdata on radiation fog. The improved M-Y model greatlycorrects several shortcomings of the original M-Y model:the underestimations of the mixed-layer depth and themagnitude of turbulent kinetic energy, and the discrepanciesin the formation and dissipation times of the fog. Inaddition the improved M-Y model can reproduce theoccurrence of Kelvin-Helmholtz instability and periodicoscillations due to its energy cycle. It is shown that theoptimization of both the closure constants and the masterlength scale is required for this improvement.The improved M-Y model has an improvement also in theLevel-2.5 version. Although the performance of theLevel-2.5 version is not so good as that of the Level-3version, the former has the advantage of relatively lowcomputational cost and is popularly used in operationalweather forecasts. Our computational scheme for theimproved M-Y model allows us to switch its hierarchylevels easily according to the purpose.
- Publication:
-
Boundary-Layer Meteorology
- Pub Date:
- 2004
- DOI:
- 10.1023/B:BOUN.0000020164.04146.98
- Bibcode:
- 2004BoLMe.112....1N