within one common boundary, that is, the
lower 48 states of the United States.
CONVECTIONMotions in a fluid, such as the
atmosphere or water, which are predominantly
vertical, resulting in a vertical transport of mass.
CONVECTIVE CELLCumiliform cloud, usually
with vertical updrafts in the center and sinking
downdrafts in the outer region.
CONVERGENCE Atmospheric flow approaching
the same point from different directions.
CORRELATIONA measure of similarity between
variables or functions.
depiction of the atmosphere produced by
compiling base data vertically, along a user
DDNDefense Data Network.
DECIBEL(dB) A logarithmic expression for the
ratio of two quantities. Mathematically, dB = 10
cations links that have no other purpose than to
transmit data between components of the WSR-
DERIVED DATAData created from the computer
processing of base data.
DESCENDING NODEThe period of time when a
polar-orbiting satellite is traveling from north
toward the south.
electromagnetic waves traveling in a straight path
to bend around a boundary or obstruction.
DISTORTIONAn apparent warping and twisting
of an image received from a satellite caused by the
characteristics of the satellite lens and the optical
DIVERGENCEAtmospheric flow leaving the
same point in different directions.
DMSPosition given in degrees, minutes, and
seconds of latitude and longitude.
DMSPDefense Meteorological Satellite Program.
DOPPLER EFFECTThe observed change in the
frequency of sound or electromagnetic waves due
to the relative motion of the source and the
DOWNBURSTA strong downdraft from a
thunderstorm cell that induces an outburst of
damaging winds on or near the ground.
DRYLINEA mesoscale feature with its own
associated vertical circulation. It is a narrow,
almost vertical zone, across which a sharp
moisture gradient, but little temperature gradient,
occurs at the earths surface.
DSNDefense switched network, an upgrade and
name change from the automatic voice network
EARTH SYNCHRONOUSSee geostationary.
ECCENTRICITY The ratio of apogee and perigee.
A true circular orbit has an eccentricity of 1.
ECHOEnergy backscattered from a target as seen
on the radar display.
propagated through space in the form of an
advancing disturbance in electric and magnetic
fields. Also referred to as radiation.
ELECTROMAGNETIC SPECTRUMThe total
range of the various radiation frequencies and
ENHANCEMENT The process of augmenting a
black and white satellite image by the addition of
either color or alternating gray shading.
EPHEMERIS DATATemporary data listing the
coordinates of a satellite at a number of specific
times within a specific period.
EPOCHAn instant in time, selected as a point of
EQUATORIAL ORBITSatellites that circle the
earth over the equator and have an inclination of
0°. (Geostationary satellites).
EXTERNAL USERAnyone other than a Principal
User who has access to WSR-88D products, for
example, information service companies,
broadcast meteorologists, aviation interests, and