RSM/HYSPLIT Emergency Response Modeling System

Overview

A joint project between ARL and the National Centers for Environmental Prediction (NCEP) resulted in an operational system that can be used to support atmospheric emergencies. The Relocatable Spectral Model (RSM) is used to produce high resolution (40km) meteorological forecast fields on demand anywhere in the world. The model output fields are then used as input to Hysplit4 to produce pollutant transport and dispersion forecasts as required to support emergency operations. The linked models run quickly because the higher resolution RSM fields are only required for the first 24 hours of transport before the pollutant mixes over a larger spatial domain. The dispersion calculation is automatically carried over on to the routinely available AVN model fields.

Research

An illustration of the differences is shown in the illustrations below, where trajectories were calculated using the RSM and AVN data fields. A ridge of high pressure was centered over the release point (Melbourne, Australia) and the spatial resolution was critical in determining the initial trajectory directions. Wind fields computed by the RSM clearly showed the release to occur prior to the passage of the ridge, i.e. the flow at all levels was to the north. However calculations using the more coarse AVN fields showed that the ridge has passed the release point at the lowest levels (flow to the south). The issue of spatial resolution can be a critical element in the early stages of an accidental pollutant release

RSM Calculation

AVN Calculation

References

Draxler, R.R. and G.D. Hess, 1997: An overview of the Hysplit_4 modeling system for trajectories, dispersion, and deposition, to be submitted Australian Meteorological Magazine

McQueen, J.T., R.R. Draxler, G.D. Rolph and H.M. Juang, 1996: Evaluation of the NCEP Regional Spectral Model to support NOAA's Environmental Emergency Response Program. 11th Conf. Numerical Wea. Pred., Amer. Meteor. Soc., Norfolk, VA, 171-173.