Figure 1-15. Wind directions
(b) Precipitation. Precipitation reduces visibility; therefore, less smoke is needed for
concealment. Heavy rain or snow reduces visibility to such a large degree that smoke is rarely
necessary.
(c) Cloud cover. Cloud cover affects air temperature as related to ground temperature
and, therefore, affects the temperature gradient. Lapse and inversion usually occur under less than 30-
percent cloud cover; neutral conditions, under more than 70-percent cloud cover.
(4) Terrain. Smoke follows the contours of the earth as it is carried by the wind. On flat,
unbroken terrain and over water smoke streamers will take longer to spread and mix. Trees and
buildings will mix the smoke streamers and increase the smoke
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CM3305
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