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FM 34-81-1: Battlefield Weather Effects

APPENDIX C

WEATHER EFFECTS ON ARMOR

Armor operations are influenced primarily by those weather elements that degrade trafficability and visibility. Although the effect may be more pronounced for armor operations, weather elements have generally similar types of impacts on other units. Listed below are weather effects for armor that are not contained in the WTDA tables.

BAROMETRIC PRESSURE. The weight of the air affects gunnery computations and ballistic performance.

CLOUDS AND SKY COVER. Low overcast clouds limit the effectiveness of aerial illumination devices. Overcast clouds tend to limit heating of inactive targets and lower target detection ranges for thermal sights. NVD are limited by clouds blocking natural light from the moon and stars. Close air support (CAS) and aerial resupply missions are degraded by low clouds.

HUMIDITY. Coupled with high temperatures, high humidity decreases crew effectiveness in closed vehicles.

ILLUMINATION. Best use of most NVD 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. Detailed products dealing with the use of E-O devices are available from the SWO.

PRECIPITATION. Rain and snow degrade trafficability and limit visibility. They also degrade target acquisition and NVD.

SURFACE WIND. Trajectory projections and first round hit capability affected by high crosswinds.

STATE-OF-THE-GROUND. Frozen ground improves mobility and significantly increases the time available to prepare fighting positions. Deep snow slows movement of tracked vehicles. Frozen ground and mud affects munitions, sensors, and indirect fire.

TEMPERATURE. Temperatures influence the type of lubricants to be used, engine warm-up periods, and sustained rates of fire for weapons. High temperatures decrease the time personnel can remain in vehicles. High temperatures cause gun tube droop, shimmering, mirages, and vehicle exteriors to be too hot to touch. Extremely high temperatures increase water consumption. Low temperatures degrade the ballistics of main guns and require frequent starting of engines and may increase maintenance problems and possible detection by the enemy. Extremely low temperatures reduce personnel effectiveness and decrease the availability of water because of freezing. Temperatures changing from above to below freezing can freeze stationary tracks into the mud.

VISIBILITY. Visibility affects visual acquisition, degrades laser range finding and target acquisition systems.

WINDCHILL. Winds affect the apparent temperature in which soldiers must operate. The windchill table must be consulted to determine the actual effective temperature.