* Humidity and Precipitation alter the effects of chemical agents.
increase the effectiveness of HD and smoke, but do not influence the
effectiveness of aerosol type nerve agents (GB). High humidity accompanied
by high temperatures increases the effectiveness of these agents.
rainfall occurring hours after liquid nerve (VX) contamination poses a
recurrence of contact hazard.
* Terrain Contour. Under stable conditions chemical agent clouds tend to flow
over rolling terrain and down valleys. Dangerous concentrations can be found
in hollows, low ground, depressions, and fighting positions.
allows an even, steady movement.
* Trees and Vegetation. Vegetated areas are more effectively contaminated with
* Soils. The type and condition of the soil affect chemical shell penetration,
bury in soft ground or snow before bursting.
Part of the chemical agent
filling remains in the crater and the evaporation rate is decreased.
soil decreases effectiveness of smoke munitions.
The weather and terrain and nuclear, biological, and chemical (NBC) teams work
closely in the IPB process. The weather team analyzes the effects of weather on
tactical operations and integrates weather data with terrain analysis. The NBC
element provides information on the use of chemical agents. It is for these
reasons weather and terrain analysis are inseparable factors of tactical
intelligence, but are independent and examined as two separate steps in the IPB
Weather analysis begins with building the weather data base. During static
conditions the data are based on historic weather records. The weather team
researches weather conditions for at least the last five years to determine weather
factors in the battlefield area, and isolates seasonal weather patterns.
After seasonal weather characteristics are determined, the team focuses on specific
periods within each season that may deviate from the seasonal norm. Through
detailed analysis, seasonal weather windows that favor certain types of operations
may be identified.
The weather data base, continuously updated, is the foundation for analyzing the
effects of weather on combat operations. This analysis begins with an evaluation
of the mission, threat, areas of operations and interest, and friendly
capabilities. While we must consider the effects of weather and NBC hazards on
personnel and equipment, we are primarily concerned with its effect on mobility and