Easterlies
- any winds with components from
the east
Eccentricity
- a dimensionless quantity describing the elliptical shape
of a planet's orbit
Echo
Tops - the height above ground of the center of the radar
beam using the tilt, or scan, that contains the highest elevation where
reflectivities greater than 18 dBZ can
be detected
ECMWF
- European Center for Medium-Range Weather
Forecasting
Effective
Terrestrial Radiation - the difference between upwelling
infrared or terrestrial
radiation emitted from the earth and the downwelling
infrared radiation from the atmosphere
El
Niño - a warming of the ocean current along the coasts
of Peru and Ecuador that is generally associated with dramatic changes
in the weather patterns of the region; a major El Niño event generally
occurs every 3 to 7 years and is associated with changes in the weather
patterns worldwide
Electromagnetic
Radiation - see radiation
Electromagnetic
Spectrum - the ordered series of all known types of electromagnetic
radiation, arranged by wavelength ranging from the short cosmic rays through
gamma rays, X-rays,
ultraviolet radiation, visible
radiation, infrared radiation,
microwaves, to the long wavelengths of
radio energy
Energy
- the capacity for doing work and
overcoming resistance
Entropy
- the amount of Energy that is not available
for work during a certain process
Equation
of State - the state of an ideal gas can be shown to be pa=RT,
where p is the pressure; a is the specific
volume; R is the specific gas constant;
and T is the absolute temperature
Equilibrium
- a state of balance in a system where opposing forces or fluxes
balance
Equilibrium
Level (or EL) - on a sounding,
the level above the level of free convection (LFC) at which the temperature
of a rising air parcel again equals the
temperature of the environment. The height of the EL is the height at
which thunderstorm updrafts no longer accelerate
upward. Thus, to a close approximation, it represents the height of expected
(or ongoing) thunderstorm tops.
Equilibrium
Vapor Pressure - the vapor pressure
of a system in which vapor and liquid
(or vapor, liquid and solid) coexist in equilibrium (i.e., at saturation)
Equivalent
Potential Temperature (or Theta-e) - the temperature
a parcel of air would have if a) it was
lifted until it became saturated, b) all
water vapor was condensed
out, and c) it was returned adiabatically (i.e., without transfer of heat
or mass) to a pressure of 1000 millibars.
Theta-e, which typically is expressed in degrees Kelvin,
is directly related to the amount of heat and
moisture present in an air
parcel. Thus, it is useful in diagnosing atmospheric instability.
Equinox
- the time when the sun crosses the equator and day and night
are everywhere of equal length
Eta
Model - one of the operational numerical forecast models run
at NCEP. The Eta is run twice daily, with forecast
output out to 48 hours.
Evaporation
- the process by which a liquid
is transformed into a gas
Evapotranspiration
- loss of water from the soil both by evaporation
and by transpiration from the plants
growing thereon
Exosphere
- the upper most layer of the earth's atmosphere; the only
layer where atmospheric gases can escape into outer space
Extratropical
Cyclone - a cyclone in the middle
and high latitudes often being 2000 kilometers in diameter and usually
containing a cold front that extends toward
the equator for hundreds of kilometers
Eye
- the roughly circular area of a tropical
cyclone marked by only light winds or completely
calm with no precipitation
Eye
Wall- the collection of thunderstorms
which generally surround the eye of a hurricane
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