Weather — page 2 of 38

Weather terms

101. AFTR after
102. AFWA Air Force Weather Agency
103. AGC automatic generation control.
104. AGDISP A particular atmospheric disperison model used for treating the transport and diffusion of aerially sprayed pest control agents in agricultural…
105. AGFS Aviation Gridded Forecast System
106. Agglomerate An ice cover of floe formed by the freezing together of various forms of ice.
107. AGL Above Ground Level
108. AGN Again
109. AHD Ahead
110. AHOS Automatic Hydrologic Observing System
111. AHOS-S Automatic Hydrologic Observing System - Satellite
112. AHOS-T Automatic Hydrologic Observing System - Telephone
113. Air The mixture of gases that surrounds the earth and forms its atmosphere, composed of, by volume, 21 percent oxygen, 78 percent nitrogen.
114. Air carrier An operator (e.g., airline) in the commercial system of air transportation consisting of aircraft that hold certificates of, Public Convenience and…
115. air density The mass per unit volume of air; about 1.275 kilometer per cubic meter at 0° C and 1000 millibars.
116. Air Mass A body of air covering a relatively wide area and exhibiting horizontally uniform properties.
117. Air Mass Thunderstorm Generally, a thunderstorm not associated with a front or other type of synoptic-scale forcing mechanism.
118. Air pollutant Any substance in the air which could, if in high enough concentration, harm humans, other animals, vegetation, or material.
119. Air Pollution The presence of contaminants in the air in concentrations that prevent the normal dispersive ability of the air, and that interfere with biological…
120. Air Pollution Potential The meteorological potential for air pollution problems, considered without regard to the presence or absence of actual pollution sources.
121. Air Pressure Specifically the air pressure of the tires. Changing the air pressure in the tires is a way to alter the setup and handling of a NASCAR race car.
122. Air Quality Model Mathematical or conceptual model used to estimate present or future air quality.
123. Air Stagnation A meteorological situation in which there is a major buildup of air pollution in the atmosphere.
124. Air Stagnation Advisory This National Weather Service product is issued when major buildups of air pollution, smoke, dust, or industrial gases are expected near the ground for a…
125. Air temperature Air temperature (Also termed surface temperature in meteorology). The ambient temperature indicated by a thermometer exposed to the air but sheltered from…
126. Air Toxin Toxic air pollutant.
127. Air Transportable Mobile Unit A modularized transportable unit containing communications and observational equipment necessary to support a meteorologist preparing on-site forecasts at…
128. Airborne Snow Survey Program Center (NOHRSC) program that makes airborne snow water equivalent and soil moisture measurements over large areas of the country that are subject to…
129. AIRMET Airman's Meteorological advisory (WA)
130. AIV Aviation Impact Variables
131. Alaska Current A North Pacific Ocean current flowing counterclockwise in the Gulf of Alaska. It is the northward flowing (warm) division of the Aleutian Current
132. Albedo The ratio of light reflected by a surface to the light falling on it.
133. Alberta Clipper A fast moving low pressure system that moves southeast out of Canadian Province of Alberta (southwest Canada) through the Plains, Midwest, and Great Lakes…
134. Alberta Low Alberta Low A low centered on the eastern slope of the Canadian Rockies in the province of Alberta, Canada.
135. ALERT Automated Local Event Reporting in Real Time. Network of automatic raingauges that transmit via VHF radio link when precipitation occurs.
136. Alert Stage The elevation, or stage, of a stream at which need-to-know officials (e.g., county sheriff, civil defense officials, bypass gate operators) are notified…
137. Aleutian Current An eastward flowing North Pacific Ocean current which lies north of the North Pacific Current.
138. Aleutian Low A semi-permanent, subpolar area of low pressure located in the Gulf of Alaska near the Aleutian Islands.
139. ALF Aloft
140. ALG Along
141. Algorithm A detailed formula or set of steps for solving a particular problem. To be an algorithm, a set of rules must be unambiguous and have a clear stopping…
142. ALIASING When computer graphics output has jagged edges or a stair-stepped, rather than a smooth, appearance when magnified.
143. Alkalinity The total concentration of bases in water.
144. Alliance of Small Island States (AOSIS) The group of Pacific and Caribbean nations who call for relatively fast action by developed nations to reduce greenhouse gas emissions.
145. Alluvium Deposits of clay, silt, sand, gravel, or other particulate materials that have been deposited by a stream or other body of running water in a streambed…
146. Along-slope Wind System A closed, thermally driven diurnal mountain wind circulation whose lower branch blows up or down the sloping sidewalls of a valley or mountain.
147. ALQDS All Quadrants
148. Alternative Energy Energy derived from nontraditional sources (e.g., compressed natural gas, solar, hydroelectric, wind).
149. ALTHO although
150. Altimeter An instrument that indicates the altitude of an object above a fixed level. Pressure altimeters use an aneroid barometer with a scale graduated in…
151. Altimeter Setting A correction of the station pressure to sea level used by aviation. This correction takes into account the standard variation of pressure with height and…
152. Altocumulus A cloud of a class characterized by globular masses or rolls in layers or patches, the individual elements being larger and darker than those of…
153. Altostratus A cloud of a class characterized by a generally uniform gray sheet or layer, lighter in color than nimbostratus and darker than cirrostratus.
154. Ambient Surrounding natural conditions or environment at a given place and time. Environmental or surrounding conditions.
155. Ambient Air The air external to a building or device.
156. AMD Amend
157. AMOS Automatic Meteorological Observing System
158. Amplifier A device used to increase the strength of an analog signal
159. Amplitude The maximum magnitude of a quantity. Often used to refer to the maximum height of a wave.
160. AMS 1. Air Mass - a body of air covering a relatively wide area and exhibiting horizontally uniform properties. 2. American Meteorological Society
161. AMT Amount
162. AMVER Automated Mutual Assistance Vessel Rescue System. A system operated by the U.S.
163. AMVER/SEAS A software program created by the National Weather Service intended to efficiently generate AMVER and VOS reports as part of a cooperative effort.
164. Anabranch A diverging branch of a river which re-enters the main stream.
165. Anaerobic An environment or condition in which molecular oxygen is not available for chemical, physical or biological processes.
166. Anaerobic decomposition The breakdown of molecules into simpler molecules or atoms by microorganisms that can survive in the partial or complete absence of oxygen.
167. Anaerobic Lagoon A holding pond for livestock manure that is designed to anaerobically stabilize manure, and may be designed to capture biogas, with the use of an…
168. Anaerobic organism An organism that does not need oxygen to stay alive. See anaerobic.
169. analog In chemistry, a substance that is similar, but not identical, to another.
170. analog signal A signal, such as voice, that varies in a continuous manner.
171. Analysis A process in which anything complex is separated into simple or less complex parts.
172. ANBURS Alphanumeric Backup Replacement System
173. Anchor Ice Submerged Frazil ice attached or anchored to the river bottom, irrespective of its formation.
174. Anchor Ice Dam An accumulation of anchor ice which acts as a dam and raises the water level.
175. Anemometer An instrument for measuring the force or velocity of wind; a wind gauge.
176. Anemorumbograph Anemorumbograph Russian anemograph (recording anemometer) which is equipped with a device to record the wind direction in addition to wind speed.
177. Anemorumbometer Anemorumbometer Russian anemometer combined with a vane to determine the wind direction.
178. Aneroid Barometer An instrument for measuring atmospheric pressure in which a needle, attached to the top of an evacuated box, is deflected as changes in atmospheric…
179. Angels Radar echoes caused by birds, insects, and localized refractive index discontinuities.
180. Angle of Reflection The angle at which a reflected ray of energy leaves a reflecting surface. It is measured between the outgoing ray and a perpendicular to the surface at…
181. Angstrom A unit of length equal to 10-8 cm.
182. Annex I Countries/Parties Group of countries included in Annex I (as amended in 1998) to the United Nations Framework Convention on Climate Change, including all the developed…
183. Annex I Parties Industrialized countries that, as parties to the Framework Convention on Climate Change, have pledged to reduce their greenhouse gas emissions by the year…
184. Annual Flood The maximum discharge peak during a given water year (October 1 - September 30).
185. anomalies The departures of temperature, precipitation, or other weather elements from long-term averages.
186. ANOMALOUS PROPAGATION (AP) Non-standard atmospheric temperature or moisture gradients will cause all or part of the radar beam to propagate along a non-normal path.
187. Anomaly Something that is out of the ordinary. For example if in a set of 1000 two winged, two legged, one headed, (essentially normal) chickens, one of them had…
188. Antarctic "Ozone Hole" Refers to the seasonal depletion of stratospheric ozone in a large area over Antarctica. See ozone, ozone layer.
189. Antedecent Precipitation Index (Abbrev. API) - an index of moisture stored within a drainage basin before a storm.
190. ANTENNA GAIN The measure of effectiveness of a directional antenna as compared to an isotropic radiator, maximum value is called antenna gain by convention.
191. Anthelion A luminous white spot that appears on the parhelic circle at the same altitude as the sun and 180 degrees from it in azimuth.
192. Anthracite A hard, black, lustrous coal containing a high percentage of fixed carbon and a low percentage of volatile matter. Often referred to as hard coal.
193. Anthropogenic Referring to alterations in the environment due to the presence or activities of humans.
194. Anthropogenic Source A pollutant source caused or produced by humans.
195. Anti-wind The upper or return branch of an along-valley wind system, as confined within a valley, and blowing in a direction opposite to the winds in the lower…
196. Anticyclogenesis The formation or intensification of an anticyclone or high pressure center.
197. Anticyclone A large-scale circulation of winds around a central region of high atmospheric pressure, clockwise in the Northern Hemisphere, counterclockwise in the…
198. Anticyclonic circulation Anticyclonic circulation System of air movements (atmospheric circulation) associated with an anticyclone, which is clockwise in the Northern Hemisphere…
199. Anticyclonic Rotation Rotation in the opposite sense as the Earth's rotation, i.e., clockwise in the Northern Hemisphere as would be seen from above.
200. Antilles Current A current which originates in the vicinity of the Leeward Islands as part of the Atlantic North Equatorial Current.