APPENDIX I GLOSSARY A ACCRETION—Growth or increase in size by gradual addition. AGL—Above ground level. Measurements suffixed by the abbreviation AGL refer to height. AMBIENT—A representative reading or measurement  for  a  substance  under  surrounding conditions. AMDAR—Aircraft   meteorological   data   relay. ANALOG—Proportional and continuous. An analogue   recorder   draws   continuous   lines proportional  to  the  electronic  signal  input.  In  an analogue   signal,   the   sound   pitch   varies proportionately  with  the  intensity  of  the  signal,  and the signal is continuous. ANEMOMETER—A  device  used  to  measure  wind speed and/or wind direction. From the Greek word anemo,  meaning  wind,  and  modern  word  meter, meaning measurement device. ANEROID—Without   fluid   or   without   water.   An aneroid barometer uses no fluid (mercury). ANOMALOUS—Irregular or abnormal. APPARENT—The   way   something   appears   or   is perceived, although it may not be true. ASCENSION —Rising   or   increasing   in   elevation. ASOS—Automated  surface  observing  system. AUTODIN —Automatic     digital     network. AWN—Automated    weather    network-the    complex worldwide  collection  and  distribution  network  of meteorological data and NOTAMs operated by the Air Force for the DoD. AZIMUTH—The    horizontal    angular    measurement from a fixed reference to a point. The Navy uses angular  measurements  in  clockwise  degrees  from  0 to 360. When 0 is referenced to true north, the result is a true azimuth bearing. When referenced to an arbitrary direction. such as the bow of a ship. the result is a relative azimuth bearing. B BACKING—A  change  in  wind  direction  in  a  counter- clockwise  manner  in  the  Northern  Hemisphere,  or  a clockwise direction in the Souther Hemisphere. BATHYMETRY—The features and depths underwater. BATHYTHERMOGRAPH—Any    device    used    to measure  and  record  temperatures  through  a  column of water. C CAD —Collective address designator. CDD—Chemical  downwind  direction. CDS—Chemical  downwind  speed. CENTIGRAYS —(cGy)  A  measurement  of  absorbed radiation equal to 1 rad. CIC—Combat information center aboard ship. CLIMATIC—Any    element    associated    with    the climate of an area. CLIMATOLOGY —The    study    of    the    statistical means,   frequencies,   deviations,   and   trends   of weather elements for an area over a period of time. CODAR—Coded aircraft report. D DDN—Defense   data   network. DHD—Downwind    hazard    distance    (radiation    or chemical). DIURNAL—Any change that follows a daily pattern. completing one cycle on a daily basis. DME—Distance  measuring  equipment,  a  radio  aircraft navigation  aid  that  provides  only  a  distance  to  a DME   transmitter   site.   Normally   used   in conjunction with VOR, ILS, or LOC equipment. DMS—Position given in degrees. minutes, and seconds of latitude and longitude. AI-1