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File: 950925_0pgv0107_00p.txt
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weather critical thresholds

Filename:0pgv0107.00p
[   (b)(2)   ]


[   (b)(6)   ]


TO: ARCENT

Question: Request the weather critical thresholds (wind speed and 
direction, visibility, temperature, humidity, lunar illumination, 
and cloud cover) for Iraqi operations during both offensive and 
defensive: air, air assault, air defense artillery, 
communications, light infantry, logistics, mech inf/armor, NBC, 
and smoke.

AIR

[      (b)(1) sec 1.3(a)(4)    ]





NBC

For chemical weapons, in general, an increase in temperature 
increases the rate of evaporation, and thus reduces the exposure 
time. An ideal time to employ chemical agents is during a 
temperature inversion. This condition is characterized by an 
increase in air temperature with an increase in height. It usually 
exists on a clear or partially clear night when the middle and low 
clouds cover less than 30 percent of the sky and on early mornings 
until about 1 hour after sunrise when the wind speed is less than 
5 knots. During an inversion there are a minimum of convection 
currents producing a maximum of air stability.

Large-area nonpersistent chemical attacks are most effective when 
wind speeds are less than 15 knots. Small-area nonpersistent 
chemical attacks are most effective when wind speeds are less than 
5 knots.

High humidity and precipitation alter the effects of chemical 
agents differently. For example, high humidity increases the 
effectiveness of mustard agent but does not influence the 
effectiveness of sarin. Heavy rains may wash away chemical agent 
contamination, but some agents may collect in low areas presenting 
lingering hazard.

Biological agents also respond to various environmental stimulus 
differently. In general, high heat, low humidity, and bright 
sunshine have adverse affects on most B agents.

Prepared by [   (b)(2)   ]
 



 

 



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