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

Wednesday, 1 August 2001
Evaluation of RAMS surface wind forecasts for the Chesapeake Bay during the Coastal Marine Demonstration Project
Jeffery T. McQueen, NOAA/NWS, Silver Spring, MD; and F. Aikman III and J. G. W. Kelley
Poster PDF (90.9 kB)
During June and July 1999 and again in February and March 2000, the NOAA Air Resources Laboratory (ARL) and the National Ocean Service's Coastal Survey Development Laboratory (NOS/CSDL) participated in the Coastal Marine Demonstration Project (CMDP). The CMDP, sponsored by the National Oceanographic Partnership Program (NOPP), was begun to develop, improve and deliver forecast products of coastal environmental phenomena of the Chesapeake Bay and surrounding coastal regions. ARL contributed by employing its previous experiences in predicting local-scale atmospheric flows which affect air quality. Previously, ARL applied a modified version of the Regional Atmospheric Modeling System (RAMS) for air quality applications. This paper describes and evaluates a demonstration operational coastal marine prediction system using a non-hydrostatic RAMS (4 km grid-spacings) for the Chesapeake Bay (CBRAMS) and Mid-Atlantic coastal waters to predict atmospheric variables such as winds, temperature, moisture, convergence zones, visibility and precipitation. The CBRAMS predictions also were interfaced with NOS oceanographic models to predict the Bay region water level and waves. These predictions represent an early and experimental attempt at non-hydrostatic atmospheric model forecasting of a coastal region. CBRAMS forecasts are also evaluated quantitatively for the summer, 1999 against the NWS operational Eta model wind predictions to assess the conditions when value is added by running a customized local-scale model.

The use of RAMS for the CMDP has demonstrated that one to two day prediction of local-scale atmospheric phenomena (e.g.: bay breezes, channeling, increased over water wind speeds) is now possible with recent advances in computer architecture and parallel programming. Insights learned from this experiment will be valuable for future modeling over coastal environments.

Preliminary results revealed that CBRAMS at 4 km grid spacings showed promise in predicting the onset and strength of bay and river breezes and frictional channeling. Quantitative analysis showed that 4 km CBRAMS predicted the summertime up bay channeling winds at Thomas Point Light and the CBOS buoy well with up to 54 % wind direction error reduction over Eta predictions. Also, Eta predictions yielded little differences in median error and error variablity between all winds and southerly wind categories for the northern bay over-water sites. Therefore, CBRAMS indicated a significant improvement in predicting the onset of the afternoon up bay breeze channeling which typically occurs in the summer afternoon. Also, Local forecast offices have found the 4 km forecasts valuable for marine forecasts and locations of pre-convective convergence zones.

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