3.
Determine the Dissipation Effect of Wind on a Chemical Agent Cloud
High winds increase the rate of evaporation of liquid chemical agents and
dissipate chemical clouds more rapidly than low winds. The effects of
wind speed on persistent chemical attacks are variable.
Large area nonpersistent chemical attacks are most effective in winds not
exceeding 15 knots.
Small area nonpersistent chemical attacks with
rockets or shells are most effective in winds not exceeding 5 knots.
However, if the concentration of chemical agent can be established
quickly, the effects of high wind speed can be partially offset.
In
general, high wind speed increases the effectiveness of a nonpersistent
surprise attack when munitions containing massive agent loads are used.
Air moving over an irregular surface sets up eddies, or mechanical
turbulence, that act to dissipate a chemical cloud.
Once agents are detected, units can be warned to take appropriate
protective measures to minimize the effects of chemical agents.
Detection allows individuals to survive and units to accomplish the
mission. Chemical agents can be delivered directly, on-target, on unit
positions or upwind, off-target, to drift over the unit position.
Table 3-1 shows the arrival time of chemical agents for various wind
speeds. A distance of 150 meters was chosen because that is the optimum
distance that a chemical agent detector can be placed upwind and a
chemical agent cloud cannot slip behind the alarm and hit the unit. When
using the chart, commanders must realize that if the concentration of
chemical agents is low, the alarm may not respond for several seconds.
The average time to mask is 15 seconds.
Warning times for different
distances and wind speeds can be determined using the following formula:
CM7114
3-6
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