Application of a coupled meteorological forecast and sound propagation model to forecast blast noise at the Aberdeen Test Center

Communities around the Chesapeake Bay have expressed concern at noise resulting from explosions and detonations at the Aberdeen Proving Ground (APG). To help schedule loud noise-producing programs, the Army Test and Evaluation Command (ATEC) is employing the modeling capabilities of the Four Dimensional Weather (4DWX) prototype system developed for ATEC by NCAR. The 4DWX system includes MM5 forecasts continually updated with the latest available observations. This is used with a ray-tracing sound propagation model (NAPS) to forecast sound levels in areas surrounding the range. The APG land area protrudes into the upper Chesapeake Bay, so that it is surrounded by water on three sides, and drives complex mesoscale flow patterns. This makes reliable sound level forecasting there a particularly challenging problem. In this paper the coupled MM5-NAPS model is described and some validation results presented (based on coupled model forecast comparisons to microphone data), along with component error estimates from the MM5 and the NAPS separately. The use of ensembles to provide probabilities of sound level exceedence is also described.