Transcript Atmospheric Variables

The Atmosphere
The atmosphere is the layer of gases that
surrounds earth.
The present condition of the atmosphere is
called weather and can be described by the
following weather variables:
• Temperature
• Air Pressure
• Wind
• Clouds
• Humidity
• Precipitation
Temperature
Temperature is the
average kinetic energy
of a substance.
Kinetic energy is the
energy of motion , so
in the atmosphere:
The more the gas molecules move (or
VIBRATE), the more kinetic energy
they have and the higher the air
temperature.
Where does the atmosphere get its energy?
Temperature
There are three temperature scales:
• Celsius
• Kelvin
• Fahrenheit
There is a temperature conversion chart on page
13 of your ESRT. Turn there now and convert
these temperatures.
20 °F = -7 °C
20 °F = ? °C
50 °C = 323 K
50 °C = ? K
273 K = ? °C and °F 273 K = 0°C and 32°F
Temperature
Meteorologists find it useful to map
temperatures so they can see trends and
make better forecasts. They draw lines on
maps to connect equal temperatures called:
Isotherms
(type of Isolines)
How to make Isotherms
or any type of isoline.
1. Realize exactly what temperature you looking
to draw an isotherm for and make a “mark”on
that number.
Draw two isotherms at 10° intervals starting with 40 °F.
• 40
• 40
• 35
• 33
• 31
• 45
• 43
• 40
• 40
• 40
• 50
• 50
• 45
• 47
• 45
• 54
• 55
• 50
• 50
• 49
How to make Isotherms
or any type of isoline.
1. Realize exactly what temperature you looking
to draw an isotherm for and make a “mark”on
that number.
2. Connect equal temperatures at the requested
interval.
Draw two isotherms at 10° intervals starting with 40 °F.
• 40
• 40
• 35
• 33
• 31
• 45
• 43
• 40
• 40
• 40
• 50
• 50
• 45
• 47
• 45
• 54
• 55
• 50
• 50
• 49
How to make Isotherms
or any type of isoline.
1. Realize exactly what temperature you looking
to draw an isotherm for and make a “mark”on
that number.
2. Connect equal temperatures at the requested
interval.
Draw two isotherms at 10° intervals starting with 40 °F.
• 40
• 40
• 35
• 33
• 31
• 45
• 43
• 40
• 40
• 40
• 50
• 50
• 45
• 47
• 45
• 54
• 55
• 50
• 50
• 49
How to make Isotherms
or any type of isoline.
1. Realize exactly what temperature you looking
to draw an isotherm for and make a “mark”on
that number.
2. Connect equal temperatures at the requested
interval.
Draw two isotherms at 10° intervals starting with 40 °F.
• 40
• 40
• 35
• 33
• 31
• 45
• 43
• 40
• 40
• 40
• 50
• 50
• 45
• 47
• 45
• 54
• 55
• 50
• 50
• 49
Do the Isotherm example
in your notes.
1. Realize exactly what temperature you looking
to draw an isotherm for and make a “mark”on
that number.
2. Connect equal temperatures at the requested
interval.
Draw isotherms at 10° intervals.
85•
90•
80 •
70 •
82 •
86 •
80 •
60 •
45•
70 •
57 •
60 •
50 •
Do the Isotherm example
in your notes.
1. Realize exactly what temperature you looking
to draw an isotherm for and make a “mark”on
that number.
2. Connect equal temperatures at the requested
interval.
Draw isotherms at 10° intervals.
85•
90•
80 •
70 •
82 •
86 •
80 •
60 •
45•
70 •
57 •
60 •
50 •
Air Pressure
• Air pressure is the weight of the atmosphere
pushing down on the earth’s surface.
• This weight or pressure is affected by factors
such as temperature and humidity.
• Cold temperatures lead to low kinetic energy and
closely packed molecules (more dense = high
pressure)
• Warm temperatures lead to high kinetic energy
and widely spaced molecules (less dense = low
pressure)
Air pressure (continued…)
• Since water vapor is a
very light weight gas,
air that has a lot of
water vapor in it (high
humidity) is less dense
and lighter than dry
air.
• Dry air = higher
pressure
• Wet air = lower
pressure
Barometer
Barometers measure air
pressure. This is a
mercury barometer.
Air pushing
down on a
dish of
mercury
forces the
liquid metal
up into the
hollow glass
tube.k
Isobars
Isobars connect equal air pressures on a map. They work the
same way as isotherms and you should use the same
techniques when drawing them. The white lines below are
isobars. The “L” indicates low pressure and the “H” indicates
high pressure.
In your notes, draw five isobars at 10mb intervals.
1000 
990 
1010 
1000 
990 
1020 
980 
1010 
1020 
1020 
1010 
980 
1010 
980
990 
1000 
1000 
990 
980 
990 
990 
Start by marking one value like 980.
1000 
990 
1010 
1000 
990 
1020 
980 
1010 
1020 
1020 
1010 
980 
1010 
980
990 
1000 
1000 
990 
980 
990 
990 
Then, connect the points with a smooth line.
1000 
990 
1010 
1000 
990 
1020 
980 
1010 
1020 
1020 
1010 
980 
1010 
980
990 
1000 
1000 
990 
980 
990 
990 
Repeat this process for the next value (990).
1000 
990 
1010 
1000 
990 
1020 
980 
1010 
1020 
1020 
1010 
980 
1010 
980
990 
1000 
1000 
990 
980 
990 
990 
Repeat this process for the next value (990).
1000 
990 
1010 
1000 
990 
1020 
980 
1010 
1020 
1020 
1010 
980 
1010 
980
990 
1000 
1000 
990 
980 
990 
990 
Finally, it should look like this.
1000 
990 
1010 
1000 
990 
1020 
980 
1010 
1020 
1020 
1010 
980 
1010 
980
990 
1000 
1000 
990 
980 
990 
990 
Humidity (aka water vapor)
• Air is saturated, when it is holding all
the water vapor it can.
•When air temperature falls below it’s dew
point temp., water vapor will turn into liquid.
What is this process called?? Condensation!
•Answer this in your notes, which
has more water vapor? A parcel of
air at 25°C and RH=70% or a parcel
of air at 45°C and RH=70%. Please
attempt to support your answer.
The higher the air temp. the
more water vapor it can hold.
Measuring Humidity
• When it comes to forecasting precipitation,
dew point temp. and relative humidity are
critical.
• A sling psychrometer and page 12 of your ESRT
allow us to determine dew point temp. and
relative humidity.
Attempt to explain why the wet-bulb
temperature is always lower than the dry-bulb
temperature?
When evaporation occurs, it cools the surface
of whatever the liquid is on.
Calculating Dew Point Temp. and
Relative Humidity
-
Cloud Formation
What is a cloud?
A cloud is a mass of air that has suspended
water droplets and or ice crystals within it.
What is fog?
Fog is a low lying cloud.
Cloud Formation
How do clouds form?
1st Air must rise.
2nd As air rises, the mass of air will experience
Less air pressure aloft. This will allow the mass
Of air to expand and when gases expand, they
Cool (decrease in temperature).
3rd If the decreasing temperature reaches its
Dew point temp., condensation will occur (the
Water vapor will turn to liquid).
A CLOUD IS BORN!
Cloud Formation
Windward side of Mtn.
Prevailing
Wind
direction
Mass
of Air
Leeward side of Mtn
Cloud Formation
Windward side of Mtn.
Prevailing
Wind
direction
Air rises
Mass
of Air
Leeward side of Mtn
Cloud Formation
Windward side of Mtn.
Prevailing
Wind
Air expands
direction due to less
pressure aloft
Mass
of Air
Leeward side of Mtn
Cloud Formation
Windward side of Mtn.
Prevailing
Wind
direction
Expands
due to less
pressure
aloft.
Mass
of Air
Leeward side of Mtn
Cloud Formation
Windward side of Mtn.
Prevailing
Wind
direction
Expansion
causes air
to cool.
Mass
of Air
Leeward side of Mtn
Cloud Formation
Windward side of Mtn.
Prevailing When temp.
reaches its dew
Wind
pt. Temp.,
direction
Condensation
occurs.
Mass
of Air
Leeward side of Mtn
Cloud Formation
Windward side of Mtn.
Prevailing
Wind
direction
A cloud
is
Born!
Leeward side of Mtn
Cloud Formation
Windward side of Mtns. are
Cool and Moist climates.
Prevailing
Wind
direction
A cloud
is
Born!
Leeward side of Mtn
Cloud Formation
Windward side of Mtn.
Prevailing
Wind
direction
Leeward side of Mtn
Cloud Formation
Windward side of Mtn.
Prevailing
Wind
direction
Leeward side of Mtn
Air mass
will sink.
Cloud Formation
Windward side of Mtn.
Prevailing
Wind
direction
Leeward side of Mtn
Air will be compressed by
increasing air pressure and
air temp. will increase
Cloud Formation
Windward side of Mtn.
Prevailing
Wind
direction
Leeward side of Mtn
The difference between air
temp. and dew pt. temp.
will become greater and
cause relative humidity to
decrease.
Cloud Formation
Windward side of Mtn.
Prevailing
Wind
direction
Leeward side of Mtns. are
warm and dry climates.