Tracking and Predicting the Atmospheric Dispersion of Hazardous Material Releases Implications for Homeland Security (2003) / Chapter Skim
Currently Skimming:
3. Observational Capabilities and Needs
3. Observational Capabilities and Needs
Pages 19-32
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 19... ...
The amount of C/B/N agent that will settle to the surface is determined by the turbulence level and the composition of the plume in the case of dry deposition, and by the composition of the plume and scavenging by clouds and precipitation in the case of wet deposition. If the source of a release remains unknown after the events, downwind observations in combination with trajectory models are needed to back-calculate the source location (and possibly even the source strength)
|
From page 20... ...
will have increased capability for possibly identifying some plume constituents. WIND LOCAL FLOWS Wind measurements are needed to track a near-surface C/B/N release in real time and to provide input for dispersion models, numerical weather prediction (NWP)
|
From page 21... ...
Some promising technological developments include: · fiber optic-based sensors that provide rapid response to a variety of chemicals at trace concentrations; · flow injection analysis on a microelectromechanical system platform that provides high sensitivity and selectivity within hundreds of seconds from a small sample volume; and · micromachined gas chromatography sensors that aid in real-time chemical sensing of toxic gases. Some key challenges in this field include improving detector sensitivity and specificity and reducing the power drain so that smaller-size batteries can be used.
|
From page 22... ...
Local terrain can cause strong spatial variations in wind speed and direction, creating local flows that are, in turn, disrupted by the presence of buildings. Local flows (e.g., mountain-valley winds, land and sea breezes, horizontal eddies caused by deflection of the wind by terrain)
|
From page 23... ...
circulations can develop independent of the local terrain. Those associated with convective storms are readily identified and closely watched, but we are only dimly aware of other less apparent circulations that persist after a storm has died or that develop in response to subtle differences in land cover or soil moisture.
|
From page 24... ...
, other government agencies, and the private sector to collect data from surface networks throughout the western United States for purposes of research, education, and operational support (see http://www.met.utah.edu/jhorel/html/mesonet/~. There are dozens of tightly packed surface-tower arrays or single towers around the country run for monitoring air pollution or highway conditions, storm forecasting, research, K-12 education, or television weather programs.
|
From page 25... ...
, which provides winds at heights from 500 m to about 16 km, but the lack of data at lower levels and the relatively coarse vertical resolution limit the usefulness of these profilers for near-surface applications. There are, however, several 900-MHz band boundary layer radar wind profiler networks being used for research in Oklahoma, Kansas, Texas, California, and elsewhere.
|
From page 26... ...
. The heights and depths of turbulent layers are shown clearly in reflectivity profiles from 900-MHz band radar wind profilers at altitude ranges from 150 meters to a few kilometers (Plate 3~.
|
From page 27... ...
However, when there is warm air moving over a cold surface or when cloudy skies prevent strong heating of the ground, there may be little mixing. The stable warm-over-cold air temperature layering that often occurs at night can isolate the surface from such releases, but breaking waves or surges of cold air can initiate mixing between the turbulent layer and the surface, or the wind change between the layers can increase enough to promote mixing (Box 3.3~.
|
From page 28... ...
Progress also is being made in running mesoscale models using assimilated radar data, providing another avenue for future improved estimates. Satellite views of the low clouds associated with horizontal deposition may be obscured by higher clouds, so forecasters and emergency managers will have to rely on models and wind field observations to project where the plume will intercept hills or mountains.
|
From page 29... ...
The committee supports this recommendation and further recommends that the design and data collection strategy of this radar network be optimized to include providing information for supporting response to a C/B/N release. Radar wind and radio acoustic sounding system profilers, which measure variations of the horizontal wind and temperature, respectively, with height and enable identification of turbulent layers, provide important information for response to C/B/N attacks and are relatively inexpensive and easy to maintain.
|
From page 30... ...
x at at at o o at o · At at at At v at o at At At To at At .
|
From page 31... ...
o o Cad o Cat o So Cat Cat VO o Ct
|
From page 32... ...
In addition, field programs conducted for other purposes, such as improvement of weather forecasting or understanding boundary layer turbulence, also can be useful. There should be continued field programs focused on C/11/N release issues, and datasets from field programs with a C/11/N or related focus should be made available for testing and development of dispersion and mesoscale transport models.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.