Vietnam War: Forest Fire as a Military Weapon - Paperless Archives
Vietnam War: Forest Fire as a Military Weapon - Paperless Archives
Vietnam War: Forest Fire as a Military Weapon - Paperless Archives
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U<br />
SECRET<br />
The yearly sums of (+) values and (-) values describe the yearly precipitation regime at a location, <strong>as</strong> illustrated for<br />
Missoula in Table 4. The sum of (+) values does not include any month when mean temperature is less than 400 F-the<br />
approximate lower limit for plant growth activity. At lower temperatures the level of soil moisture content is not considered<br />
<strong>as</strong> a major factor limiting plant growth. Also, in calculating the yearly sum of(+) values the maximum value used<br />
for any month is +40. This value represents a rather humid month-equal to an average monthly precipitation of 4.51<br />
inches occurring on 10 rain days for a month having an average daily mean temperature of 600 F. The highest possible<br />
humidity value for a location is 12 times 40, or +480. The (-) values for all bum months-designated <strong>as</strong> "B" months-are<br />
totaled, regardless of monthly mean temperature, in calculating their yearly sum.<br />
N Table 4<br />
Missoula, Montana<br />
Month Av. Av. Av, PD Humidity values<br />
* mean monthly rain days, value from Figure 26 f]<br />
temp. prec. > 0.1 in. (+) value () value<br />
(OF.) (Ins.) (No.)<br />
I Jan. 22 1.3 5.9 7.7 (7.4)<br />
Feb. 27 0.9 4.4 4.0 (3-5)<br />
Mar. 36 1.0 5.2 5.2 (4.0)<br />
Apr. 45 1.0 5.2 5.2 +3.0<br />
May 54 2.0 5.9 11.8 +7.9<br />
June 60 2.1 6.7 14.1 +9.0<br />
July 68 1.0 3.7 3.7 -4.0<br />
Aug. 66 0.9 3.7 3.3 -3.9<br />
Sept. 56 1.3 4.4 5.7 +1.4<br />
Oct. 46 1.2 4.4 5.3 +2.9<br />
Nov. 33 1.2 5.9 7.1 (6.2)<br />
Dec. 25 1.3 5.9 7.7 (7.3)<br />
Yearly sum2/ +24.2 -7.9<br />
I No. of"B" mos. 3/ 2<br />
j/ A (+) or (-) value for any month is its PD value less the value of the 50/50 line for the mean temperature of that month.<br />
For example, in this table the PD value for January is 7.7, the 50/50 line value from Figure 26 for 220 mean temperature<br />
is 0.3, and the (+) value for January is 7.4.<br />
;1 Yearly sum of (+) values does not include months with mean temperature less than 40%F.<br />
N/ A "B" month is any one having a (-) value.<br />
I<br />
I<br />
iSECRET 31