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Weather and Climate
Definitions
• Meteorology- is the study of the
atmosphere- including weather.
Weather-the daily conditions of the
atmosphere. It can change from time to
time and place to place.
Climate- the type of weather an area
has over a long period of time.
Layers of the atmosphere
• Layers of the
atmosphere:
separated by
difference of
temperature
patterns.
Troposphere
Gases present
In
Troposphere
We live in the
troposphere.
• 0-12 km
• Temperature
decreases
• All weather occurs
here
• All water vapor in the
atmosphere is here
• Contains people,
clouds, airplanes
Other layers
Stratosphere
• Temperatures
increase
• Home of the
Ozone layer.
• 12-50km
• Mesosphere
• Upper layers- temperatures get
colder (coldest layer)
• The air is very thin here.
• Where meteors will burn up
Thermosphere
• 82-600km
• Gets very hot as you go up
• Contains aurora borealis
• Sub layers: ionosphere, and
exosphere
Northern Lights
• Aurora borealis happens in
ionosphere. Aurora Borealis is
also called the Northern Lights.
They happen when sun rays
enter ionosphere and hit the
moving molecules. This is
sometimes called magnetic
storm. What we see is a glow in
many colors.
Things that change in atmosphere
• Temperature
• Water content and
humidity
• Air pressure
• Cloud Cover
• Wind Speed
• Precipitation
Temperature
• Measures the
average kinetic
energy (energy of
motion) of
molecules.
• Heat enters
atmosphere from
the sun as
incoming solar
radiationinsolation
3 ways to measure Temp.
• Fahrenheit
– Water freezes at 32°
– Water boils at 212 °
• Celsius
– Water freezes at 0 °
– Water boils at 100 °
• Kelvin
– Water freezes at 273K
– Water boils at 373K
Temperature Conversions
Isotherm- line connecting
locations of equal temperature
Air Pressure
• Caused by weight of
the air
• Weight of the air
above earth’s surface
pushes down on the
surface so there is
pressure exerted on
the surface
Air pressure
• Air pressure is greatest • Why are we not
closer to the surface of
crushed by air
the earth
pressure?
• Average pressure is 14
pounds (lbs.) per
square inch
• Ans: air pressure is
pushing out at the
same time it is pushing
in
Factors affecting air pressure:
• 1. Elevation(altitude)- the higher the
elevation the lower the air pressure (air is
thinner- less weight is pushing down)
• 2. Temperature- warmer the air, lower the
pressure
• 3. Moisture/Humidity- more water vapor
that goes into the air, the lower the air
pressure
Measuring air pressure
• Barometer- an
instrument used to
measure changes in air
pressure
1. Mercury barometer
Measuring air pressure
• 2. Aneroid barometer
• Measured in
millibars= average
1013mb
• Range- 970- 1040mb
Moves clockwise
and outward
Moves counterclockwise
And inward
Pressure Conversions
HIGH
1013.2
LOW
Isobars- lines connecting
patterns of equal air pressure
Example:
Isotherms v. Isobars
• Isotherms (Temp)
– Generally DOES
NOT end in
circles.
– ALWAYS goes
from one side of
the U.S. to the
other
• Isobars (Pressure)
– Can be lines or
circles-can end in
the middle of the
map
– Intervals of 4
– Would have a H or
L inside the center
IN BOTH, YOU CANNOT CROSS LINES!!!!
Winds move from high to low
pressure
Wind- the movement of air
parallel to the ground
• Caused by
differences in air
pressure and
temperature
• Closer the isobar
lines, faster the wind
speed
Draw the lines around a High and a Low
H
L
Wind direction
• Winds are named
for the direction that
they come from
• On a map direction
is shown with a line
showing where it
came from.
Sea Breeze- Day
• Water has a high
Air sinks over water and moves to land
specific heat= takes
longer to warm up and
cool down
• Air over water is
cooler, so it sinks and
a breeze moves from
water to land
Land Breeze- Night
• At night , the
land will cool
down faster than
the water- the
breeze then
moves from land
to sea
Relative Humidity
• The amount of water
in the air is called
humidity.
• The ability of air to
hold water changes
depending on the
temperature.
• Relative humidity
tells "how full" the
air is with water.
• It is expressed in %.
• 100% is full and
can't hold any
more.
• Water gets into the
air by evaporation(liquid to gas)
Dew Point
• To get the water out of the air it
either condenses or sublimes.
• condense-changing from gas
to liquid.- dew
• Dew Point- the temperature at
which condensation begins
• Frost – dew that freezes due to the
temperature dropping below the
dew point.
At this point- condensation
can begin and clouds will
start forming
Measuring Relative Humidity &
Dew Point
• The “Dry Bulb”
- It is just a
thermometer.
– It measures the air
temperature.
• The “Wet Bulb”
– Has a little wet
booty tied to the
bottom.
– Gets cool when
water evaporates.
Wind speed- measured in knots
Converting air pressure
• Converting from millibars to station model
code
– use only the last three digits and throw out the
decimal point
– Example: 1020.5 = 205
• Converting from station model to millibars
– if the code is 500 or higher put a 9 in front,
otherwise put a 10
– Example: 281= 1028.1
Try these:
(>500 put 9 in front) (<500 put 10 in front)
• 1008.4= 084
• 987= 998.7
• 976.6= 766
• 888= 988.8
• 1022.2= 222
• 168= 1016.8
• 992.2= 922
• 080= 1008.0
Clouds- how they form
• Form by process
called condensation
– This happens
when the air is so
moist that it can
no longer hold any
water.
– = air is saturated
• In order for
anything to
happen:
– the sun must
heat the earth
which heats the
air above it and
rises into the
atmosphere.
• As air rises, it cools because of expansion and moving
away from heat source
• Air will then cool enough to reach dewpoint
• Water vapor then condenses into condensation nuclei
• When enough droplets condense- we see them as clouds
Why clouds look different
• Clouds are usually a mixture of both water vapor
droplets and ice crystals. The water and ice scatter
all light, making clouds appear white. If the clouds
get thick enough or high enough all the light above
does not make it through, hence the gray or dark
look. Also, if there are lots of other clouds around,
their shadow can add to the gray or multicolored
gray appearance.
When air is forced to rise because it hits mountains,
it will cool and condense
- Windward side of the mountains will have a cool,
moist climate.
- Leeward side- there will be a warm, dry climate
Windward
Leeward
When air is forced to rise because it hits mountains, it will cool and
condense
On the Leeward side, there will be a dry climate that is usually
warmer than the windward
On the Windward side of the mountains it will have a moist climate.