In hazmat response situations, on-site collection and dissemination of real-time weather information can be critical to understanding and assessing the extent of contamination by airborne agents. Local data are more representative of the actual conditions at the incident site than data from an airport or other fixed monitoring location, and they will yield a more accurate prediction of where the hazardous material has traveled and where it will go.

The need for real-time, on-site data collection and dissemination was recognized over 25 years ago by the Environmental Protection Agency and National Oceanic and Atmospheric Administration and led to the development the CAMEO/ALOHA/MARPLOT computer program package. The ALOHA portion of the program allowed on-site weather data to be estimated and input manually, or for actual data obtained from on-site weather-monitoring equipment to be automatically uploaded.

Since the creation of the CAMEO/ALOHA/MARPLOT suite, additional programs have been developed and have evolved to give responders a better evaluation of the transport and diffusion of toxic agents. Programs now can couple sophisticated map displays with improved atmospheric models driven by real-time on-site weather data to predict where these agents will travel.

Examples of some of these most recently developed programs are the SAFER programs from Safer Systems, the Hazard Prediction and Assessment Capability used by the U.S. government and government contractors, the Meteorological Information and Dispersion Assessment System Anti-Terrorism from ABS Consulting, and the ADASHI program from Optimetrics.

ADASHI, for example, provides first responders a street map view of any hazardous, terrorist, or weapons of mass destruction incident overlaid with critical warnings and guidance. The program includes intelligent WMD and hazmat agent discovery, replaces CAMEO/ALOHA for hazard prediction, accommodates real-time weather acquisition, and provides easy-to-follow guidance in the form of suggested action checklists.

Other response programs have been customized for specific sites and users, all of which accept on-site data from weather-monitoring systems in real time to yield the most accurate estimate of the path of the hazardous agents.

System components

On-site weather-monitoring systems consist of a set of sensors, a data processor, and a method to communicate the data to the computer running the transport and diffusion model. The most basic of these is a system that mounts on a command post vehicle near the site. The data are output from the data processor to the computer via a cable. A disadvantage of these systems is that they most likely won't be as close to the incident site as might be desirable, and it's possible that the local weather data measured at the command post may be significantly different that the conditions at the incident location. This could result in inaccurate estimates of the location and concentration of the toxic agents as they travel downwind.

Remote weather-monitoring systems are available that can relay their weather data via low-power radio to the dispersion-modeling computer. These systems have advanced over the past decade to become compact, one-piece units that require no assembly of the components on site and integrate technologies such as solid-state wind sensors, which have no moving parts.

Once delivered to the site, an internal electronic compass inside the weather station can automatically orient wind data to north, so that in the heat of an emergency the responder doesn't have to program the unit with manually input compass settings. These compact one-piece designs also can save critical time at the incident scene, allowing responders to track a plume as soon as possible.

On-site weather-monitoring systems also are available that have been designed to require very little electrical power for operation. These low-power systems can operate throughout an incident, without the need for battery recharging or replacement. If a weather-monitoring system is in a hot zone, the prospect of retrieving it to replace or recharge the batteries may range from impractical to impossible.

Compact, handheld on-site weather-monitoring systems also have the advantage of being able to be moved very quickly. Such portability can prove valuable should the need arise for weather data inputs from several locations, or if a site has highly variable terrain. The monitoring system can be carried from one location to another, with the data being reported either manually or via radio telemetry to the command post and computer system.

Possible uses

The basic set of measurements that are needed by software using transport and dispersion models are wind speed, wind direction and air temperature. Even when these data are automatically fed to a computer running an ALOHA program, however, the relative humidity, inversion height, cloud cover, ground roughness and the station elevation will have to be input manually. Other programs can accept a broader range of local meteorological data fed automatically.

On-site weather-monitoring stations also can be used for routine monitoring of areas where a spill has an increased likelihood of occurring, such as at a chemical manufacturing or storage facility. In such cases, the site-specific weather data can be fed to plume-dispersion models running around the clock so that the computer can map out where a plume will go from the moment of its release in the event of an emergency.

These systems also can be used for planning accident scenarios, with the output from preplanned scenarios provided to all local responders. In the event of an incident, once the responders know the current weather conditions, they'll be able to match those conditions with in-hand scenario outputs and be able to respond to the incident without the need for immediate access to the model output.

David Katz is vice president of government sales for Climatronics Corp. He has been involved with meteorological sensors for nearly 20 years, specializing in work with highly portable systems designed for rapid response in hazmat, emergency response and homeland security applications. He has a bachelor's degree in earth and planetary sciences and a master's degree in atmospheric sciences.