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FM 34-81-1: Battlefield Weather Effects

APPENDIX H

WEATHER EFFECTS ON LIGHT INFANTRY

Infantry operations are influenced primarily by those weather elements that degrade trafficability and visibility. The effect may be significant for infantry operations, but weather elements have similar impacts on other units. The following contains other weather effects that are not contained in the WTDA tables.

CLOUDS AND SKY COVER. Low overcast clouds limit the effectiveness of aerial illumination devices. Overcast clouds limit heating of inactive targets and lower target detection range for thermal sights. NVD are limited by clouds blocking natural moonlight or starlight. CAS and aerial resupply missions are hampered by low clouds.

HUMIDITY. When coupled with high temperatures, humidity decreases the effectiveness of crews in closed vehicles.

ILLUMINATION. The use of most NVDs requires about a quarter (23 percent) of the moon, 30 degrees above the horizon, scattered clouds, and the sun more than 5 degrees below the horizon. See Appendix F for weather products dealing with E-O devices.

PRECIPITATION. Rain and snow degrade trafficability, limit visibility, and affect certain target acquisition and NVD.

STATE-OF-THE-GROUND. Ground state affects trafficability and movement rates. Frozen ground improves mobility and will increase the time available for preparing fighting positions.

SURFACE WIND. Trajectory data and first round hit capability are degraded by high crosswinds.

TEMPERATURE. High and low temperatures influence the type of lubricants used, engine warm-up periods, and sustained rates of fire for weapons. High temperatures decrease the time soldiers can remain in vehicles and increase water consumption. Low temperatures degrade the ballistics of main guns, require frequent starting of engines, increase maintenance problems, and increase possible detection by the enemy. Extreme low temperatures reduce personnel effectiveness, and decrease availability of water due to freezing.

VISIBILITY. Poor visibility affects visual sighting, laser range finding, and E-O target acquisition systems. Poor visibility increases the survivability of infantry units.

WINDCHILL. See Appendix L for a discussion on windchill.