Download NSTA Meteorology Reading 5 • Weather and the Redistribution of

NSTA Meteorology Reading 5
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Weather and the Redistribution of Thermal Energy
‣ Weather = a response to the unequal heating of Earth’s atmosphere
‣ Temperature gradients created by imbalances in rates of heating and cooling from once
place to another within the atmosphere
‣ Many different kinds of energy
‣ Energy can be transformed from one type to another
‣ The total amount of energy remains the same (energy s conserved)
‣ 4 types of energy relevant for the atmosphere:
* Air molecules higher in elevation have a greater gravitational or potential energy
than air molecules lower in elevation
* Air moving together (wind) has kinetic energy
* Molecules and atoms that make up the air move and vibrate independently for
thermal energy
* Radiant energy associated with the radiation and light received from the Sun or
emitted form Earth
- Heat Versus Temperature
‣ Temperature - average kinetic energy, or energy of motion, per atom or molecule of a
particular substance
‣ Heat (aka thermal energy) = total kinetic energy of all of the atoms or molecules
composing a given amount of a substance; the energy transferred from one object to
another as a result of a difference in temperature between the objects
- Heating Earth
‣ Earth’s atmosphere heated by solar radiation and terrestrial radiation
‣ Radiant energy from sun is not uniformly distributed throughout the planet because of
Earth’s 23.5 degree tilt and the curvature of Earth’s surface
‣ Large portion of the total solar radiation reaching Earth passes through the atmosphere
and reaches the ground where it is reflected or absorbed
- Heat Transfer within the Atmosphere
‣ Earth’s atmosphere transmits, scatters, and reflects more radiant energy from the Sun
than it absorbs
‣ Earth’s surface absorbs more radiation energy than it reflects
‣ Earth emits more infrared radiation than the atmosphere, and this imbalance results in
some energy transfer from the surface to the atmosphere
‣ Sensible heart = thermal energy we can feel, “sense”, and measure with a thermometer;
transfer of sensible heat from Earth to the atmosphere involves process of conduction
and convection
‣ Latent heat = transfer of hear as a consequence of changes in phase of water; energy
released or absorbed when a substance changes phase: solid to liquid, liquid to gas, gas
to liquid, etc.
‣ Conduction = transfer of energy from a warmer object to a cooler one through direct
contact
‣ Convection = process of heat distribution within a fluid (such as air), achieved through
movement of the fluid itself; important process in atmospheric heating because of
density difference between parcels of air with differing temperatures
‣ Latent heat of fusion = amount of energy required for transformation from solid to
liquid
NSTA Meteorology Reading 5
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Latent heat of vaporization = amount of heat energy required for transformation from
liquid to vapor
‣ Latent heating builds on the process of sensible hearing and allows considerable energy
to be transferred from Earth’s surface into its atmosphere
Local Effects of Heat Transfer
‣ Variations in atmospheric heating result in the development of temperature gradients
‣ Air moves and circulates to even out hear distribution (wind); temperature gradients are
responsible for wind
Air Masses and Fronts
‣ Air mass = region or body of air that has consistent of temperature and moisture
content throughout
‣ Frontal Zone or Front = boundary where the two air masses interact
‣ Types of Fronts:
* Cold front = cold air mass advances against warm air mass forcing warm air up
* Warm front = warm air mass advances against cooler air mass, riding up over the
cooler air in front of it
* Stationary front = neither cold air mass nor warm air mass can advance against the
other
* Occluded front = cold air mass advances agains an equally cold or similar
temperature air mass
‣ Frontal zones responsible for formation of much of cloudiness, rain, and snow that
occurs over the United States, especially in the winter