Overview

Our motivation for this work is twofold. First, emergency managers must develop plans of action for responding to releases of hazardous material into the atmosphere, especially for high–profile events where many people gather into a small area (e.g., the Olympic Games). Second, when military commanders prepare their strategic battle plans, they must distill a vast array of information about the area where operations will take place, to identify hazards that airborne and ground forces will face on the battlefield. In both cases, a key piece of information is the typical "weather" one might encounter, and how this may help or hinder operations. This kind of planning takes place weeks or months in advance of the actual operations, well beyond the range where we can explicitly forecast individual weather features (or events) with any credibility. One alternative is to use climatographical data to help define the "typical" atmospheric conditions for a given day. Climatographic information derived from the global re–analysis such as the NCEP/NCAR Reanalysis and the European Center for Medium Range Weather Forecasting 40–year Reanalysis have limited utility because they are done on a very coarse grid (∼100–250 km) which does not define local–scale circulations in and around complex topography and coastal margins. These circulations strongly influence both the sensible weather and the climate, as well as the transport and dispersion (T&D) processes within the boundary layer.

NCAR's RAL is engaged in an array of National and international projects to create high–resolution downscaled reanalyses for T&D applications using NCAR's state–of–the–art Climate Four Dimensional Data Assimilation (ClimoFDDA) system that is based upon the Weather Research and Forecasting (WRF) model. The common goal for all these projects is to produce highly refined estimates of the "typical" atmospheric conditions for any given hour, day, month or season, significantly enhancing the risk assessment and strategic planning capabilities.

Probability that the surface dosage will exceed a user–defined threshold, for a simulated agent released over Gaza City 6 h prior to the time shown here. To obtain this estimate, ClimoFDDA produced the "typical" atmospheric conditions and uncertainties during the nighttime in September from a 20–year downscaled re–analysis.