Subj : Wx Terms (I)(3)
To : All
From : Daryl Stout
Date : Sat Jun 10 2017 12:04 am
Iridescence
Brilliant spots or borders of colors in clouds, usually red and green,
caused by diffraction of light by small cloud particles. The phenomenon
is usually observed in thin cirrus clouds within about 30� of the sun
and is characterized by bands of color in the cloud that contour the
cloud edges.
Iridescent Clouds
Clouds that exhibit brilliant bright spots, bands, or borders of colors,
usually red and green, observed up to about 30 degrees from the sun. The
coloration is due to the diffraction with small cloud particles
producing the effect. It is usually seen in thin cirrostratus,
cirrocumulus, and altocumulus clouds.
Irrigation
In hydrologic terms, the controlled application of water to arable lands
to supply water requirements not satisfied by rainfall.
Irrigation Requirement
In hydrologic terms, the quantity of water, exclusive of precipitation,
that is required for crop production. It includes surface evaporation
and other economically unavoidable wastes.
Isallobar
A line of equal change in atmospheric pressure during a specified time
period.
Isentropic Analysis
A way in the forecaster can look at the atmosphere in 3-dimensions
instead of looking at constant pressure surfaces (such as the 850 mb,
700 mb, 500 mb, etc.) which are in 2-dimensions. In this analysis method,
the forecaster looks at constant potential temperature (the temperature
that it would take if we compressed or expanded it adiabatically to the
pressure of 1000 mb) surfaces. Air parcels move up and down these
surfaces; therefore, the forecaster can see where the moisture is located
and how much moisture is available.
Isentropic Lift
Lifting of air that is traveling along an upward-sloping isentropic
surface.
Isentropic lift often is referred to erroneously as overrunning, but
more accurately describes the physical process by which the lifting
occurs. Situations involving isentropic lift often are characterized by
widespread stratiform clouds and precipitation, but may include
elevated convection in the form of embedded thunderstorms.
Isentropic Surface
A two-dimensional surface containing points of equal potential
temperature.
Isobar
A line connecting points of equal pressure.
Isobaric Chart
A weather map representing conditions on a surface of equal atmospheric
pressure. For example, a 500 mb chart will display conditions at the
level of the atmosphere at which the atmospheric pressure is 500 mb.
The height above sea level at which the pressure is that particular
value may vary from one location to another at any given time, and
also varies with time at any one location, so it does not represent a
surface of constant altitude/height (i.e., the 500 mb level may be at
a different height above sea level over Dallas than over New York).
Isobaric Process
Any thermodynamic change of state of a system that takes a place at
constant pressure.
Isobath
In hydrologic terms, an imaginary line on the earth's surface or a
line on a map connecting all points which are the same vertical
distance above the upper or lower surface of a water-bearing formation
or aquifer.
Isochrone
A line on a chart connecting equal times of occurrence of an event. In
a weather analysis, a sequence plotted on a map of the frontal positions
at several different observation times would constitute a set of
isochrones.
Isodop
A contour of constant Doppler velocity values.
Isodrosotherm
A line connecting points of equal dew point temperature.
Isoheight
Same as a contour depicting vertical height of some surface above a
datum plane.
Isohel
A line on a weather map connecting points receiving equal sunlight.
Isohyet
A line connected points of equal precipitation amounts.
ISOL
Isolate(d)
Isolated
A National Weather Service convective precipitation descriptor for a
10 percent chance of measurable precipitation (0.01 inch). Isolated is
used interchangeably with few.
ISOLD
Isolated
Isopleth
A broad term for any line on a weather map connecting points with equal
values of a particular atmospheric variable (temperature, dew point,
etc.). Isotherms, isotachs, etc. are all examples of isopleths.
Isotach
A line connecting points of equal wind speed.
Isotherm
A line connecting points of equal temperature.
Isotropic
Having the same characteristics in all directions, as with isotropic
antennas. Directional or focused antennas are not isotropic.
Issuance Time
The time the product is transmitted.
ITCZ
Inter-tropical Convergence Zone. The region where the northeasterly and
southeasterly tradewinds converge, forming an often continuous band of
clouds or thunderstorms near the equator.
ITWAS
Integrated Terminal Weather System
---
� Synchronet � The Thunderbolt BBS - wx1der.dyndns.org
