FM 34-81-1: Battlefield Weather Effects

GLOSSARY

PART 1 - ACRONYM LIST

AA antiaircraft gun
AAA antiaircraft artillery
AAM antiaircraft missile
AC Active Component
A/C air conditioning
ACR armored cavalry regiment
ADA air defense artillery
adapt adapter
AF See USAF
AFM air force manual
AFO aerial forward observer
AFR air force regulation
AGL above ground level
AG/LT assault gun/light tank
AI area of interest
alt altitude
ammo ammunition
AMSS automated meteorological sensor system
AO area of operations
APC armored personnel carrier
app appendix
AR Army Regulation
ARNG Army National Guard
arty artillery
ARTYMET artillery meteorological team
ATACMS Army tactical missile systems
ASAS All-Source Analysis System
ATCCS Army Tactical Command and Control System
ATGM antitank guided missile system
ATW antitank weapon
AVLB armored vehicle launched bridge
avn aviation
AWS Air Weather Service (USAF)

bde bridage
BDU battle dress uniform
BFA battlefield functional area
BIC battlefield-induces contaminants
BMCT beginning of morning civil twilight
BMNT beginning of morning nautical twilight
bn battalion
BWK belt weather kit

C Celsius (Centigrade)
C²command and control
C³command, control, and communications
CAB combat aviation brigade
cal caliber
cap capacity
CAS close air support
CB chemical biological
CFV cavalry fighting vehicle
CG Commanding General
comm communications
consump consumption
COSCOM corps support command
CP command post
CS combat support
CSS combat service support

D desired
DF direction finding
dir direction
div division
DOD Department of Defense
DTSS Digital Topographic Support System
DZ drop zone

E essential
EAC echelons above corps
ECB echelons corps and below
EECT end of evening civil twilight
EENT end of evening nautical twilight
effect effective
EMP electromagnetic pulse
encl enclosure
env environmental
E-O electro-optical
EW electronic warfare

F Fahrenheit
FALIIP forward area limited observation program
fc footcandle
FDC fire direction center
FLIR forward looking infrared
FLOT forward line of own troops
FO forward observer
FOB forward operating base
frz freezing
FSU fire support unit
ft feet

gHz gigahertz
GSM ground station module
GSR ground surveillance radar
GT greater than

HAHO high altitude, high opening
HALO high altitude, low opening
HC hexachloroethane
HE high explosive
HF high frequency
Hg inches of mercury
HIC high-intensity conflict
how howitzer
hq headquarters
hr hour
hvy heavy

IEW intelligence and electronic warfare
IFV infantry fighting vehicle
IMETS Integrated Meteorogical System
in inch
in/hour inches per hour
inf Infantry
inter interference
IPB intelligence preparation of the battlefield
IR Information requirement

Khz kilohertz
km kilometers
kn knot (speed measurement)

LAV light armored vehicle
lgt light
LIC low-intensity conflict
LLL low-light-level
LOC lines of communication
LOS line of sight
LRSU long-range surveillance unit
LT less than
LZ landing zone

m meter
MACOM major Army command
max maximum
Mb millibars
MDT moderate
MECH mechanized
met meteorological
METT-T mission, enemy, terrain, troops, and time available
MFF military free fall
mg machine gun
MIC mid intensity conflict
min minimum
MLRS multi-launcher rocket system
mm millimeter
MOPP mission-oriented protective posture
MOT mobile observing team
mph miles per hour
MR moonrise
MS moonset
MSL mean sea level
MSR main supply route
MT medium tank

NATO North Atlantic Treaty Organization
NBC nuclear, biological, and chemical
nmi nautical mile (distance)
NOE nap-of-the-earth
NV night vision
NVD night division devices
NVG night vision goggles
NVS night vision sights

OB order of battle
obsn observation
Op operation

qty quantity

plt platoon
PZ pick-up zone

RAP ram air parachute
R&S reconnaissance and surveillance
RC Reserve Component
recce reconnaissance
REMBASS Remotely Monitored Battlefield Sensor System
rqmts requirements
rqr required

SAM surface-to-air missile
SF Special Forces
SFG special forces group
SIO senior intelligence officer
SLAR side looking airborne radar
SOF special operations forces
SOP standing operating procedure
SOWT special operations weather team
SP self-propelled
spt support
SR sunrise
SS sunset
SWO staff weather officer

tac tactical
TAS tactical air support
TBM tactical ballistic missile
TDA tactical decision aid
temp temperature
TF task force
TOW tube-launched, optically tracked, wire-guided
TRADOC US Army Training and Doctrine Command
TTP tactics, techniques, and procedures
TV television

UAV unmanned aerial vehicle
UGDF uniformed gridded data field

US United States
USAF United States Air Force
USAR United States Army Reserve

VFR visual flight rules
VHF very high frequency
VT variable time (fuse)

WA weather advisory
WET weather, enemy, and terrain
WETM weather team
WGT wet globe temperature
wo without
WP white phosphorus
WTDA weather tactical decision aid
WW weather warning

X an unknown quantity

Y an unknown amount of time

PART 2 - DEFINITIONS

absolute humidity: A ratio of the quantity of water vapor present per unit volume of air, usually expressed as grams per cubic meter or grains per cubic foot.
Air Weather Service: An Air Force field operating agency reporting directly to the Air Staff. AWS operates centralized weather support and provides technical advice and assistance to USAF weather units in support of USAF and Army missions worldwide.
altitude: The height measured from MSL.
altostratus: Clouds that are relatively uniform gray to blue sheets that cover the entire sky. When thin, the sun or moon may be visible as a "bright spot. " Cloud bases range from 6,500 to 20,000 feet AGL.
atmospheric pressure: The pressure exerted by the atmosphere as a consequence of gravitational attraction exerted upon the column of air laying directly above any point.
barometric pressure: The measure of atmospheric pressure by a mercurial or aneroid barometer. Changes in pressure are significant in weather forecasting. The normal pressure at sea level is 29.92 inches of mercury or 1013.3 millibars. Rising pressures usually indicated improving weather conditions; falling pressures may reflect impending inclement weather. Barometric pressure is used in aircraft altimeter settings to tell pilots how far above ground level the aircraft is. This is critical for landing during obscured conditions and NOE flying.
battlefield environment: A phrase used to describe the combination of weather, terrain, BIC, illumination, and background signatures that occur on a battlefield.
belt Weather kit: A small kit with simple equipment, used originally by the US Forest Service, and now employed by S2 personnel at maneuver brigades. The BWK equipment measures temperature, dewpoint, pressure, and wind speed and direction. It is slow and does not meet the accuracy standards necessary to support the Army's battlefield weapon systems. The BWK will be replaced by an automated meteorological sensor system (AMSS)
blizzard: A violent, intensely cold wind of 30 kn or greater with considerable falling or blowing snow causing visibility to drop to .5 miles or less.
ceiling (cloud): The height above the earth's surface of the lowest layer of clouds. This layer is reported as broken, overcast, or obscured and not classified as thin or partial. See cloud cover for details.
Celsius: A temperature scale (formerly called centigrade). The temperature interval between waters ice and steam points is divided into 100 parts (or degrees) with 0^o Celsius at the freezing or ice point and 100^o at the boiling or steam point. Used commonly worldwide.
cirrocumulus: Clouds that are high and thin which appear as small white flakes or patches of cotton. Cirrocumulus clouds are sometimes called a mackerel sky. The bases of cirrocumulus clouds are above 16,000 feet AGL.
cirrostratus: Clouds that are thin and whitish layers appearing like a sheet or veil. The ice crystals composing these clouds may produce a halo effect around the sun or moon. The bases of cirrostratus clouds are above 16,000 feet AGL.
cirrus: Clouds that are thin, feather-like ice crystal clouds in patches or narrow bands. Cirrus clouds are sometimes called mares tails. The bases of cirrus clouds are above 16,000 feet AGL,
climatology: The historical records of weather conditions measured or observed at a specific location is knows as climatology. Some data go back over 100 but generally a 10- to 25-year history is more common. Climatology is useful in planning operations beyond 5 to 7 days. It usually describes the average (or mean) conditions such as high and low temperatures and extremes.
clouds: A visible aggregate of minute water and ice or just ice particles in the atmosphere above the surface of the earth. Clouds differ from fog only by definition--fog is in contact with the surface of the earth.
cloudburst: A sudden and extremely heavy downpour of rain.
cloud cover: The amount of clouds over, or at, a given location. Cloud conditions are expressed as cloud bases or ceiling, the amount of cover stated in eighths--1/8 to 4/8 described as scattered; 5/8 to 7/8, broken; and 8/8, overcast), and cloud tops. Several layers of scattered clouds added together may result in a broken or overcast condition Low clouds impact many battlefield operations, especially the use of smart weapons.
cumulonimbus: Clouds that are large, dense, and towering with cauliflower-like tops. The top portion of the cloud is often flattened into an anvil shape. Cumulonimbus clouds are also known as thunderstorms.
cumulus: Billowy, individual cloud masses that often have flat bases. Bases range from near the surface to 6,500 feet AGL.
density altitude: The height above MSL at which the existing density of the atmosphere would be duplicated in the standard atmosphere; atmospheric density expressed as height according to a standard scale. Extremely important in flight operations.
dew: Water condensed onto grass and other objects near the ground. Occurs when the temperature has fallen below the dewpoint of the surface air (due to radiational cooling during the night) but is still above freezing. If the temperature falls below freezing after dew has formed, the frozen dew is known as white dew.
dewpoint: The temperature to which a given weight of air must be cooled at constant pressure and constant water-vapor content in order for saturation to occur. When this temperature is below 0^o C, (32^o F) it is sometimes called the frost point.
diurnally: Having a daily cycle.
drizzle: Fairly uniform precipitation composed exclusively of fine drops of water falling very close to one another.
dry-bulb temperature: The temperature measured by the dry bulb of a psychrometer; ambient air temperature.
effective illumination: The level of light available for night operations.
effective wind speed: The combined effect of actual (meteorological) wind and other motion caused by the moving of an object or a person through air. Also caused by moving equipment such as aircraft propellers or rotors.
elevation; station elevation: The measure of height with respect to another point on the earth's surface; usually MSL.
Fahrenheit: A thermometer scale on which the boiling point of water is at 212^o and the freezing point is at 32^o above zero point. Used primarily in the US.
FALOP: A program implemented in the 1970's to supplement battlefield observations taken by USAF AWS WETMS. FALOP is employed by S2 personnel at maneuver brigades and battalions. The BWK is used by the S2 to make limited measurements of weather conditions. Additionally, the S2 provides estimates of other weather and environmental conditions he observes. His report is encoded and forwarded to the closest WETM.
fallout: The precipitation to earth of particulate matter from a nuclear cloud; also applied to the matter itself, which may or may not be radioactive.
fog: A cloud with its base at or very near the earth's surface.
footcandle (fc): A unit of illumination equal to 1 lumen ft-2. Full sunlight with zenith sun produces an illuminance of the order of 10,000 fc on a horizontal surface. Full moonlight provides an illuminance of about 0.02 fc. Adequate illumination for steady reading is about 10 fc. Close machine work is required about 30 to 40 fc.
forecast units: USAF WETMs and centers at higher Army echelons that produce support forecasts for planning and operations.
frost: A feathery deposit of minute ice crystals or grains upon a surface or object, formed directly from vapor in the air; the process by which such ice crystals are formed; any temperature at which frost forms. Frost often forms when the close-lying air is above 0^oC (32^oF), especially in calm, clear air when radiation or evaporation reduces a surface temperature to or below the freezing point.
frostbite: The freezing or partial freezing of some part of the human body.
frost heaves: Also frost thrusting; frost lifting. The upward or sideways movement of surface-soils, rocks, and vegetation through expansion caused by freezing subsurface moisture, soil, and gravel.
gust: Rapid fluctuations in wind speed with a variation of 10 knots or more between peaks and lulls.
hail: Hail is observed precipitation in the form of small balls or pieces of ice (hialstones), falling either separately or agglomerated into irregular lumps. Hail falls during heavy thunderstorms.
high: In meteorology it is synonymous with "area of high pressure" and refers to a maximum of atmospheric pressure in two dimensions--closed isobars in the synoptic surface chart; or a maximum of height (closed contours) in the constant-pressure chart. Since a high is, on the synoptic chart, always associated with anticyclonic circulation, the term is used interchangeably with anticyclone.
humidity: A measure of the water vapor content of air.
hypothermia: Excessive lowering of body temperature generally caused by prolonged exposure to cold or when the body has become wet. Hypothermia can occur at temperatures well above freezing as easily as at temperatures below freezing.
icing: In general, any deposit or coating of ice on an object; a mass or sheet of ice formed on the ground surface during the winter by successive freezing of sheets of water that may seep from the ground, a river, or a spring.
instrument flight rules: An aircraft operational term indicating that the weather conditions have deteriorated to the point that navigational instruments on board the plane must be used in flying from one place to another.
inversion (stable) condition: An increase in air temperature with an increase in height. The condition is called stable because there is usually little vertical movement of air.
knot: The unit of speed or distance in the nautical system. One nautical mile per hour. See conversion factors in Appendix P.
lapse (unstable) condition: A decrease in air temperature with an increase in height. The condition is called unstable because it is accompanied by vertical air movement.
light and illumination data: Battle planning requires accurate timing based on available light. Light tables have been computed for any location that tell sunrise, sunset, moonrise, moonset, and moon phase. Illumination is a measure of sunlight, moonlight, starlight, and air glow. Illumination is a critical factor in the considered of NVD, cloud cover, and terrain masking.
low: An area of low pressure referring to a minimum of atmospheric pressure in two dimensions. Since a IOW is, on a weather chart, always associated with cyclonic circulation, the term is used interchangeably with cyclone.
mesoscale: Smaller scale weather features that exist for minutes or hours. Examples of mesoscale atmospheric phenomena are thunderstorms, tornadoes, and land-sea breezes.
meteorological products: Processed information derived from basic meteorological data which is collectively referred to as meteorological products. Such information can be in the form of forecasts, specific data, or WTDAs. WTDAs may correlate one or more data elements impacting a system with critical values, timing, system limitations, and other modifying factors.
moderate weather impact: A subjective measure of weather conditions impacting a system or operations that require alternative actions to be considered. Moderate impacts limit the effectiveness of the system or operations from 25 to 75 percent.
nimbostratus: A gray or dark massive cloud layer accompanied by continuous rain or snow.
precipitation rates: The measured, or estimated, rate of rainfall or snowfall during a given period. Precipitation rates are essential to predict ground moisture, flooding, river crossings, and other trafficabiiity factors. Precipitation rates also affect visibility.
refractive index: A measure of the amount of "refraction," or bending, of an energy wave (visual light, infrared, radio and others) passing from one density to another in a medium such as air or water. The apparent bending of a stick when placed in a pool of water is an example.
relative humidity: Ratio, usually expressed as a percentage of air's water vapor content, to its water vapor capacity at a given temperature and pressure.
sea state: Also state-of-the-sea. Describes wind-generated waves on the surface of the sea.
seeability: Distance at which a sensor is able to see, to recognize, or to lock onto a target. Seeability is dependent on the condition of the atmosphere, the contrast between the target and the background, the direction and type of illumination, and the characteristics of the sensor.
semidiurnally: A cycle occurring approximately every half day.
sky conditions: The amount of sky covered by clouds or the amount obscured by surface-based phenomena. This information is derived from standard charts.
slant-range visibility: The distance a pilot can distinguish objects that are both forward and beneath his aircraft. For example, looking down at an angle as he approaches a target or a runway.
sleet: A term sometimes used for ice pellets, a mixture of precipitating rain and snow, or glaze.
snow: Precipitation composed of white or translucent ice crystals, chiefly in complex branched hexagonal form and often agglomerated into snowflakes.
soil trafficability: The capacity of a soil to withstand traffic, especially the traffic of military vehicles.
specific humidity: The ratio of the mass of water vapor to the total mass of air (including water vapor).
state-of-the-ground: A standardized surface observation that describes the condition of the ground surface. Basically, state-of-the-ground is characterized as dry, moist, wet, frozen, and ice or snow covered.
Staff weather officer: A USAF AWS officer, qualified in forecasting, that usually commands a WETM. tie may be a lieutenant or a colonel depending on the Army unit he is attached to. Some SWOs, assigned to Army commands, serve without a WETM. The SWO, a member of the Army commanders special staff, works under the direction of the G2 or S2.
steering wind: Winds that are winds measured at 50 feet (16 m), although they may extend as high as 2,500 feet. They are used in smoke operations where the moving air is measured far enough above the ground to be free of disturbances caused by local terrain variations. They establish the speed and direction of a smoke cloud. Steering winds also play a role in the direction that weather systems move.
stratocumulus: Clouds having large globular masses or rolls which look like balls of dirty cotton. Stratocumulus form from the breaking up of a stratus layer or from the spreading out of cumulus clouds. Bases range from near the surface to 6,500 feet AGL.
surface observations: Weather and environmental observations measured or estimated on the land or water surface, and usually reflecting surface conditions. Cloud cover is an exception.
surface winds: Wind speed, direction, and gust speeds measured over the land or water. Technically measured at 10 meters above the surface.
synoptic scale: Large-scale atmospheric features that exist for days or weeks. An example of synoptic scale is the analysis of weather fronts, highs, and lows over the continental us.
temperature: A measure of the hotness or coldness of the air near the surface (surface ambient temperature), the ground (surface or ground temperature), or the upper atmosphere (air temperature). Measured by a thermometer or other instrument.
temperature gradient: The change in temperature per unit of distance between one point and another.
temperature-humidity index: An indicator of the effect of temperature and humidity upon individuals. Sometimes called the misery index by television weatherpersons. An example is the WBGT index.
temperature inversion: See inversion condition.
thaws: A weather condition occurring when the temperature rises above the freezing point and ice and snow melt.
tidal current: The alternating horizontal movement of water associated with the rise and fall of the tide. In relatively open locations, the direction of tidal currents rotates continuously through 360 degrees diurnally or semidiurnally. In coastal regions, the nature of tidal currents is determined by local topography as well.
tide: The periodic rising and falling of the oceans, large lakes, and the atmosphere. [t results from the tide-producing forces of the moon and sun acting upon the rotating earth. This disturbance actually propagates as a wave through the atmosphere and through the surface layer of the oceans.
turbulence: A condition of The atmosphere in which air currents vary greatly over short distances. Turbulence may occur at any altitude, and the intensity may vary rapidly over short distances. See wind shear.
twilight: The periods of incomplete darkness following sunset (evening twilight) or preceding sunrise (morning twilight). Twilight is designated as civil, nautical, or astronomical, as the center of the sun travels 6, 12, or 18 degrees below the celestial horizon, respectively. In general, civil twilight precedes nautical twilight by 2 hours.
visual flight rules: In aviation a set of regulations that must be adhered to when piloting in calm, clear weather where the pilot can move from one point to another using ground features for navigational aids.
USAF tactical weather support: As directed by AR 115-10/AFR 105-3, the USAF AWS provides part of the Army's tactical weather support. This includes the collection of surface weather data up to the division command elements and the production of forecasts and climatic data, The Army has the greater role in its own weather support. The Army collects surface weather forward of the division command elements, and all upper air weather data needed to support its tactical operations. Additionally, the Army provides the USAF WETM the communications paths and equipment to pass weather information to the Army users.
visibility: The greatest distance that prominent objects can be seen and identified by the unaided, normal eye. When NVG or other infrared devices are used to increase visual distance, "seeability" is used instead of visibility.
weather advisory (WA): A special WETM notice when an established weather condition that could affect operations is occurring or is expected to occur.
weather briefing: Information concerning the current and forecast weather conditions impacting an AO. The SWO, or a member of the WETM or the G2 or S2 may provide weather briefings. Suggested formats are included in Chapter 4.
weather effects: The impacts, favorable or unfavorable, weather conditions have on tactical systems, operations, personnel, and logistics. Weather effects become highly significant information when they can be cross-checked with specific critical values, reaction leadtimes, and other operational considerations. There are always weather effects that will have an impact on systems or operations. There is no such thing as an all-weather system.
weather elements: Weather elements (such as wind speed and temperature) are generally benign. Only when they fall below or exceed certain pre-established thresholds do they have an adverse impact on operations, systems, and personnel. These pre-established thresholds are known as critical values. Critical values change by type of operations, sensitive (or complexity) of systems, and the amount of exposure of personnel to the elements. S2s must know the critical weather values for their unit's operations, systems and personnel and advise the commander and staff when these values are (or will be) reached or exceeded.
weather forecast: A prediction made by USAF WETMS for periods as short as 3 hours to as long as 96 hours for specific Aos and Ais. Forecasts are correlated with WTDAS to provide tailored products for the supported command's planning, The accuracy of a weather forecasts depends on the timeliness, accuracy, and resolution of the data it is taken from. The longer the period of time a forecast covers the less accurate it becomes. Forty-eight to 96-hour forecasts are considered "outlooks"--or very general forecasts. Beyond 96 hours, climatology is used.
weather forecaster: A USAF AWS officer or NCO trained in meteorology and forecasting. He uses general area forecasts produced by USAF AWS weather centers, and fine tunes them for his own AO. The forecaster need timely, accurate data from the supported unit's AO and AI to do this fine tuning.
weather observer: A USAF AWS officer or NCO trained in meteorology and weather observing. Many AWS NCOS are dual qualified as observers and forecasters and are called weather technicians. The training of an AWS weather observer is technical, S2s are instructed by AWS observers on how to take weather observations. But the observations may fall short of the AWS standard and are, therefore, characterized as "limited."
weather tactical decision aids: These refer to the manual lookup tables and matrices in this manual, or are computer-driven algorithms by which such a product is generated. These tables provide the critical thresholds that effect operations, systems, and personnel adversely. The tables, together with a current forecast, are used to brief the commander and staff.
weather warning (WW): A special notice from the supporting WETM when an established weather condition of such intensity as to pose a hazard to property or life is occurring or is expected to occur. Protective action must be taken.
weather watch: A special WETM notice alerting the command of the potential for tornadoes, severe thunderstorms, or a winter snow with heavy snow, freezing precipitation, or blizzard conditions.
wet bulb globe temperature index: A measure of heat stress potential. It is calculated by using a formula which considers relative humidity, radiant heat, air temperature, and air movement.
whiteout: Also known as milky weather. A condition in the polar regions in which no object casts a shadow, the horizon becomes indistinguishable, and light-colored objects are very difficult to see. A whiteout occurs when there is complete snow cover, and the clouds are so thick and uniform that light reflected by the snow is about the same intensity as that from the sky.
windchill factors: These factors are revised temperature values based on the effect of wind and temperature combined on exposed skin. This windchill temperature is the effective temperature for troops. The effect of windchill differs individually because of body chemistry, but is an acceptable operating standard.
winds aloft: The flow of air, measured in speed and direction above the surface. There is no distinct demarcation between winds aloft and surface winds, although winds above 100 meters are usually referred to as winds aloft.
wind shear: The rate of change of wind velocity (speed or direction)with distance. Eddies and gusts form in areas of wind shear, thus producing turbulent flying conditions. Wind shear may occur in either the vertical or horizontal plane.
wind speed: The rate of movement of air flow. Wind speed is normally reported in nautical miles per hour, or knots. Wind speed is affected by terrain and obstacles such as buildings and trees.

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Intelligence

FM 34-81-1: Battlefield Weather Effects

GLOSSARY

PART 1 - ACRONYM LIST

PART 2 - DEFINITIONS