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Topic VI “Meteorology”
Weather Studies
I. Moisture in the Atmosphere: the primary source of
energy for the water cycle is the Sun. It unevenly
heats Earth’s surface.
A. Phases of the Water
Cycle:
1. Evaporation: liquid to
gas. Requires energy
making it a cooling
process.
2. Condensation: gas
(water vapor) to a
liquid. Releases
energy into the air.
3. Transpiration: the releasing of water in the air by
plants.
4. Precipitation: the
falling of liquid or
solid water from
clouds.
Ex. Rain, sleet, snow and
hail.
B. Factors Affecting Evaporation Rate:
1. Temp.: as temp. inc.
evap. rate inc.
2. Humidity: as humidity
inc. evap. rate
decreases.
3. Wind: as wind inc.
evap. rate inc.
4. Surface Area: as
surface area inc. evap.
rate increases.
C. Relative Humidity: a comparison between the
amount of moisture in the air with the amount that
the air can hold at that temp.
1. Dewpoint Temp.: the
temp. at which
condensation occurs.
* dew: drops of water
forming on a cool
surface.
* frost: water vapor
freezes (sublimates)
on a frozen surface.
2. Sling Psychrometer: instrument used to determine
the dewpoint temp. and relative humidity.
3. Steps to determine
Dewpoint:
a. Find dry bulb temp.
b. Find the diff. Between
the wet and dry bulb
temps.
c. Use the chart on page
12 of the ref. Table.
D. Clouds: collection of tiny water droplets or ice
crystals suspended in the atmosphere.
1. Cloud Formation:
a. Warm moist air rises.
b. Air cools below
dewpoint temp. and
droplets form around
condensation nuclei
(dust/salts).
2. Cloud Types:
a. Cumulus: big puffy
white clouds.
b. Cirrus: whispy ice
crystals high in the
atmosphere.
c. Stratus: low clouds
that blanket the sky.
II. Air Pressure: the force/weight of air pushing on a
surface. Air pressure pushes in all directions equally.
Pg. 13 ref. Table.
A. Barometer:
instrument used to
measure air pressure.
* As air pressure
increases, the
barometer rises.
B. Factors Affecting Air Pressure:
1. Temperature: as temp.
increases, air pressure
decreases.
2. Altitude: as altitude
increases, air pressure
decreases.
3. Humidity: as humidity
increases, air pressure
decreases.
C. Winds: caused by differences in air pressure. The
greater the difference (gradient) the stronger the
winds.
1. Isobars: connect
points of equal air
pressure.
*the closer the isobars
the stronger the winds.
D. Local Breezes: smaller horizontal movement of
air .
1. Sea breeze: air flows
from the sea to the
land.
*cooler air (high
pressure) over the sea,
flows towards warmer
air (low pressure) over
the land.
2. Land breeze: air flows from the land to the sea.
* Air over the land cools
at night and flows
towards the warmer
air over the water.
E. Wind Direction: flow from regions of high to low
pressure and named for the direction they come
from.
1. Cyclone: (low
pressure) winds blow
counterclockwise
towards the middle.
2. Anticyclone: (high
pressure) winds blow
clockwise and out.
F. Global Winds: caused by the unequal heating of
earth’s surface. Page 14 ref. Table.
1. Diverging zones: cool,
dry high pressure air
sinks at the poles and
300 lat.
2. Converging zones:
warm, moist low
pressure air rises at the
equator and 600 lat.
III. Air Masses: large masses of air that have a
characteristic temp. and moisture of their source
region. Page 13 ref. table.
A. Source Regions:
1. Maritime: formed over
water. (moist)
2. Continental: formed over
land. (dry)
3. Polar: cool air from high
latitudes
4. Tropical: warm air from
low latitudes.
IV. Front: the boundary that separates two different
air masses. Pg. 13 ref.
A. Types of Fronts:
1. Cold Front: dense
cold air forces warm
moist air upward
creating heavy
precipitation for short
periods of time at the
frontal boundary.
2. Warm Front: warm air slowly rises over cold air
producing long periods of light precipitation ahead
of the frontal boundary.
3. Occluded Front: a fast moving cold front over
takes a slower warm front causing clouds and
precipitation.
4. Stationary Front: cold and warm air masses near
each other with neither advancing causing long
periods of light precipitation.
B. Synoptic Weather Maps: show weather conditions
on a national or global basis.
1. Storm Tracks: most
storm systems move
from west to east
across the U.S.
V. Severe Weather:
A. Hurricanes: a
large rotating
storm of tropical
origin.
*they get their
energy from
warm water.
Once they hit
land they lose
energy.
Hurricane Eye
B Tornadoes: caused by the collision of warm, moist
air with cold, dry air. Winds can exceed 370 mph.
C. Storm Safety:
1. Stay indoors
2. Store food/water
3. Have
batteries/flashlights
4. Have a radio