The COBEL model as part of a terminal-area ceiling & visibility (C&V) nowcast system: a progress report
July 18, 1996
Project Report
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MIT Lincoln Laboratory Report ATC-241
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Summary
The Federal Aviation Administration (FAA) Integrated Terminal Weather System (ITWS) is supporting the development of products aimed at providing automated guidance to the air traffic managers for the anticipation of changes in ceiling and visibility (C&V) conditions and wake vortex behavior in the terminal area. Fine-resolution, one-dimensional (column) numerical models are being considered to provide information on the evolution of the local fine-scale structure of the lower atmosphere over the terminal area. The Code Brouillard Eau Liquids (COBEL) column model is being investigated for potential use within the ITWS. This one-dimensional numerical model has been developed for the short-term prediction of fog events in the north of France. This report describes initial progress in adapting the COBEL model to a wider range of meteorological conditions. A parameterization of surface frost deposition was implemented and a slight error in the computation of stability in a saturated atmosphere was corrected. Tests suggest that these modifications represent important features of the newest version of the COBEL model. Other significant modifications to the COBEL model were performed. Pressure tendencies and vertical motion (vertical advection) were implemented as additional external forcings to the column model. Sensitivity tests show that these forcings play important roles in determining the onset, evolution and dissipation of low stratiform clouds. Some further applications of the model are briefly discussed and future development efforts are suggested.