Evaluation of RAMS in the Eastern Range Dispersion Assessment System

This paper describes the Applied Meteorology Unit’s (AMU) evaluation of the Regional Atmospheric Modeling System (RAMS) contained within the Eastern Range Dispersion Assessment System (ERDAS). ERDAS is designed to provide emergency response guidance for operations at the Cape Canaveral Air Station (CCAS) and Kennedy Space Center (KSC) in the event of an accidental hazardous material release or an aborted vehicle launch. In ERDAS, RAMS is run with four nested grids at resolutions of 60, 15, 5, and 1.25 km and full microphysics on all grids. The model is initialized twice-daily at 0000 and 1200 UTC using operationally available observational data and run for a 24-h forecast period on local workstations with multiple processors. The prognostic gridded data from RAMS is available to ERDAS for display and input to the Hybrid Particle and Concentration Transport (HYPACT) model. The HYPACT model provides three-dimensional dispersion predictions using RAMS forecast grids. Therefore the accuracy of the HYPACT model is highly dependent upon the accuracy of RAMS forecasts.

The primary goal of the evaluation is to determine the accuracy of RAMS forecasts during all seasons and under specific weather regimes. The evaluation protocol is based on the needs of Eastern Range safety and weather personnel and is designed to provide specific information about the capabilities, limitations, and daily use of RAMS in ERDAS for operations at CCAS/KSC. The evaluation consists of an objective and a subjective component. The objective evaluation focuses on gridded and point error statistics and the sensitivity of the model forecasts to soil moisture, resolution, and other factors. The subjective evaluation involves a real-time assessment of RAMS forecasts to verify the onset and movement of the Florida east coast sea breeze, low-level temperature inversions, and precipitation. Both components of the ERDAS RAMS evaluation concentrate primarily on wind and temperature (stability) forecasts which are required for dispersion predictions using the HYPACT model. When the evaluation is completed in the first part of 2000, operational users will have on-line tools and information in the form of evaluation results to help them interpret and apply forecast data from ERDAS RAMS. The presentation at the conference in January 2000 will summarize results from the evaluation and highlight recommendations for model improvements and enhancements.