Download Weather Review 2 Definitions

Mr. Fetch’s Earth Science Classroom
Temperature – a measurement of heat
Temperature is a factor of particle motion.
Temperature is measured with a thermometer
Faster moving particles create more heat
Mr. Fetch’s Earth Science Classroom
Wind
Wind is moving air
It is caused by differences in air pressure within
the atmosphere.
Air under high pressure moves toward areas of low
pressure
Mr. Fetch’s Earth Science Classroom
Barometric Pressure
Barometric pressure is the force exerted on objects
by the weight of the atmosphere above them.
Atmospheric/air pressure is measured with a
barometer in units of inches of mercury or millibars
Mr. Fetch’s Earth Science Classroom
Precipitation:
-Precipitation is rain, sleet or
snow, precipitation is any
product of the condensation of
atmospheric water vapour that
falls under gravity
Mr. Fetch’s Earth Science Classroom
Relative Humidity
 Relative humidity is a
measure of the amount of
water vapor in the air
compared to the maximum
amount of water vapor the
air can hold at that
temperature.
 A psychrometer is one
instrument that measures
relative humidity.
Dew Point and Humidex
 The dew point is the temperature which water vapor in
air will condense into liquid water. Condensed water is
called dew when it forms on a solid surface (like grass)
or a cloud when it forms in the sky.
 The humidex (short for "humidity index") is a
number used to describe how hot the weather feels to
the average person. The humidex is a unit-less number
based on the dew point, and is equivalent to the dry
temperature in degrees Celsius.
The Coriolis Effect
• Caused by the Earth’s
rotation
• Results in the curving of
moving objects, including
air
• It is one thing that causes
wind and the direction of
prevailing winds that exist
in each major latitude belt
•
Weather Fronts
• The boundary
between 2 air
masses with
different
temperatures
• Brings about a
change in
weather
Prevailing Wind
• The direction the wind blows most of the
time in a certain location
Is - the branch of science dealing with weather
forecasting.
Atmospheric conditions that are typically measured to
provide information for weather forecasts and to study
the weather and climate include:
temperature
barometric pressure
humidity
wind speed & direction
precipitation
Barometer
Device used for measuring Atmospheric/air pressure
in units of inches of mercury or millibars
Mr. Fetch’s Earth Science Classroom
Mr. Fetch’s Earth Science Classroom
1. Air Pressure is always
changing and depends on factors
such as:
• Temperature/Time of day - hotter air has
higher pressure
• Altitude – higher up = lower pressure
• Humidity – higher = lower pressure
• Migrating weather systems – Highs and
Lows
2.Represented on a weather map by
• isobars with an “H” (High Pressure) in the
central most isobar
• isobars with an “L” (Low Pressure) in the
central most isobar
Highs and Lows on Weather Maps
3.Jet Streams
• Narrow currents of fast moving air flowing
in the upper levels of the atmosphere
• Flow between cold and warm air masses
• Usually move weather systems from place
to place – always WEST to EAST
4. Humidex
 The humidex (short for "humidity index") is a
number used to describe how hot the weather feels to
the average person. The humidex is a unit-less number
based on the dew point, and is equivalent to the dry
temperature in degrees Celsius.
5. Warm Front
• Along a front the warm air mass will always be
forced up as opposed to the cold air mass.
Warm air is less dense and therefore will lift
more easily than cold air which is more dense.
Cold Front
Passes quickly through an area…sometimes as fast as 100 km/hr
Occluded Front
The Coriolis Effect
• Caused by the Earth’s
rotation
• Results in the curving of
moving objects, including
air
• It is one thing that causes
wind and the direction of
prevailing winds that exist
in each major latitude belt
•
Mr. Fetch’s Earth Science Classroom
Wind, clouds, and precipitation are all the result of
the atmosphere responding to uneven heating of the
Earth by the Sun.
The uneven heating causes temperature differences,
which in turn causes wind, which then moves the
heat to a new place.
What causes weather?
• Caused by the transfer of energy between these 3 things:
- The Sun, Earth’s surface, and the Atmosphere.
1
The sun warms
earth’s surface increasing its
temperature.
3
4
Hot air rises
and cools
Water vapor
condenses to form
clouds &
precipitation
2
The sun’s
energy is used
to evaporate
water and put
moisture into
the air.
5
m
Unequal heating and differences in air pressure cause wind.
2. Cold Fronts
C
O
N
T
R
A
S
T
•Created when a cooler air mass
overtakes a warmer air mass.
•Warm air rises b/c it is pushed up
by the cool air and b/c it is less
dense.
•Steeply sloping curved line front.
•Heavy rain and wind.
•Passes through quickly.
•Cool, dry, and clear skies after
•Mainly cumulus type clouds
Warm Fronts
•Created when warmer air mass
overtakes a cooler air mass.
•Warm air rises just b/c it is less
dense.
•Gentle sloping straight lined front.
•Light rain and wind.
•Passes through slowly.
•Warm, humid, and cloudy after.
•Mainly stratus type clouds.
3. Weather from
Cold Front
As
•Heavy rain and wind. Passes through Quickly
Approaching
/Front line
After
Cool, dry, and clear skies after front passes through.
Warm Front
• Created when a warmer air mass slowly
overtakes a cooler air mass (Both Traveling in
same Direction)
• When the faster moving air meets up with the
slower moving cooler air, the warmer (less dense)
air rises slowly and gently above the cooler air
mass.
• Weather changes slowly.
• Creates a gently sloping, straight lined “Front”.
• As the warm air rises , it cools, and causes water
vapour to condense.
Warm Front
Add
Passes slowly through an area – a couple of days
Cold Front
• Created when a fast moving cool air mass rapidly
overtakes slower warmer air mass.
• When the faster moving cooler air meets up with
the slower moving warm air, the cooler air forces
the warm air to rise more quickly than it
otherwise would rise.
• Weather changes rapidly.
• Creates a steeply sloping, curved “Front”. Almost
verticle.
• As the warm air rises , it cools, and causes water
vapour to condense.
Cold Front
Passes quickly through an area…sometimes as fast as 100 km/hr
Stationary Front
• Weather is similar to a warm front but transition is
slower and gentler yet.
• When the two masses of air meet, neither has enough
force to move the other.
• The two air masses face each other in a “stand off”they both stop moving.
• Temperature and wind direction are opposite on either
side of the front line.
• At the junction of the cold and warm air masses, clouds
will form and precipitation will occur.
• Can remain stalled over an area for days.
Stationary Front
Can remain
stalled over
an area for
days
Occluded Front
• A faster moving cold air mass overtakes a
slower moving warm air mass.
• A warm air mass gets caught in between two
cold air masses.
• The warm air forced up, causing clouds to
form. The clouds may result in rain or snow.
Occluded Front
What Causes Wind (Short
Answer)
 Wind is caused by air flowing from high pressure to
low pressure. The Earth's rotation prevents that flow
from being direct, but deflects it side to side(right in
the Northern Hemisphere and left in the Southern), so
wind flows around the high and low pressure areas.
Why do High Pressure Systems cause
weather to stay longer? (Short Answer
Question)
 Because High Pressure systems are large, usually the
size of an entire air mass, therefore they take a longer
time to move out of an area.
Mr. Fetch’s Earth Science Classroom
Precipitation: Change of State
Sublimation
+ Add energy
Uses Heat
EVAPORATION
MELTING
Uses Heat
Uses Heat
CONDENSATION
FREEZING
Gives off Heat
Gives off Heat
Deposition
Freezing/Melting point
of water/ice is 00C
Gives off Heat
- Subtract energy
Mr. Fetch’s Earth Science Classroom
Temperature Profile of a Frontal System