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FM 34-81-1: Battlefield Weather Effects

APPENDIX J

WEATHER EFFECTS ON MECHANIZED INFANTRY

Mechanized infantry operations are also influenced by those weather elements that degrade trafficability and visibility. Indeed, the weather effects impacting mechanized infantry units will include most of the conditions that play a role in both armor and regular infantry. Although the effect may be more pronounced for mechanized infantry, armor, and cavalry operations, weather elements have generally similar impacts on other units. Listed below are weather effects for mechanized infantry that are not contained in the WTDA tables.

CLOUDS AND SKY COVER. Low overcast clouds will limit the effectiveness of aerial illumination devices. Overcast clouds tend to limit heating of inactive targets and, therefore, lower target detection range for thermal sights. NVD are limited by clouds blocking natural light from the moon and stars. CAS and aerial resupply missions are hindered by low clouds.

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

ILLUMINATION. NVD require about a quarter (23 degrees) 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 discussed in Appendix F.

PRECIPITATION. Rain and snow degrade trafficability, limit visibility, and degrade the effectiveness of certain target acquisition and NVD.

STATE-OF-THE-GROUND. Wet grounds play an important role in the effectiveness of chemical agents and smoke munitions. They can also affect trafficability and movement rates. Frozen ground improves mobility and significantly increases time available for preparing fighting positions. Deep snow slows movement of tracked vehicles. Frozen ground affects systems such as mines, sensors, and indirect fire.

SURFACE WIND. Trajectory data and first round hit capability are degraded by high crosswinds. Wind, or in some cases the lack of it, affects smoke and indirect fire illumination missions and increases the number of indirect fire rounds used.

TEMPERATURE. Too cold or too hot conditions dictate the type of lubricants to be used, engine warm-up periods, and sustained rate of fire for weapons. High temperatures decrease the time personnel can remain in vehicles. Extremely high temperatures increase water consumption. Low temperatures degrade the ballistics of main guns. Extreme 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. High temperatures cause gun tube "droop," shimmering, mirages, and vehicle exteriors to be too hot to touch.

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

WINDCHILL. See Appendix L.