The present condition of the atmosphere is called weather and can be described by the following weather variables: Temperature Air Pressure Humidity

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

• Humidity

• Wind

• Clouds

• Precipitation

TemperatureTemperature 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?

TemperatureThere are three temperature scales:

• Celsius

• Fahrenheit

• Kelvin

There is a temperature conversion chart on page 13 of your ESRT. Turn there now and convert these temperatures.20 °F = ? °C

50 °C = ? K

273 K = ? °C and °F

20 °F = -7 °C

50 °C = 323 K

273 K = 0°C and 32°F

TemperatureMeteorologists 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)

• 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.

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


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.


• 40 • 40 • 35 • 33 • 31

• 45 • 43 • 40 • 40 • 40

• 50 • 50 • 45 • 47 • 45

• 54 • 55 • 50 • 50 • 49




• 40 • 40 • 35 • 33 • 31

• 45 • 43 • 40 • 40 • 40

• 50 • 50 • 45 • 47 • 45

• 54 • 55 • 50 • 50 • 49




85• 80 • 70 • 60 • 45•

90• 82 • 70 • 57 • 50 •

86 • 80 • 60 •

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• 80 • 70 • 60 • 45•

90• 82 • 70 • 57 • 50 •

86 • 80 • 60 •

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.

• 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

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

Air pushing down on a dish of mercury forces the liquid metal up into the hollow glass tube.k

Barometers measure air pressure. This is a mercury barometer.

Barometer

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.

1000 990 1010 1000 990 980 1020 980 980

1010 990 1020

1000 980 1020 1010 990 1010 1000 990 990

In your notes, draw five isobars at 10mb intervals.

1000 990 1010 1000 990 980 1020 980 980

1010 990 1020

1000 980 1020 1010 990 1010 1000 990 990

Start by marking one value like 980.

1000 990 1010 1000 990 980 1020 980 980

1010 990 1020

1000 980 1020 1010 990 1010 1000 990 990

Then, connect the points with a smooth line.

1000 990 1010 1000 990 980 1020 980 980

1010 990 1020

1000 980 1020 1010 990 1010 1000 990 990

Repeat this process for the next value (990).

1000 990 1010 1000 990 980 1020 980 980

1010 990 1020

1000 980 1020 1010 990 1010 1000 990 990

Repeat this process for the next value (990).

1000 990 1010 1000 990 980 1020 980 980

1010 990 1020

1000 980 1020 1010 990 1010 1000 990 990

Finally, it should look like this.

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??•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.

CondensatioCondensation!n!

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 itsDew point temp., condensation will occur (the Water vapor will turn to liquid).

A CLOUD IS BORN!

Cloud FormationWindward side of Mtn. Leeward side of Mtn

Mass of Air

Prevailing

Wind

direction


Mass of Air

Prevailing

Wind

direction Air rises


Mass of Air

Prevailing

Wind

directionAir expands due to less pressure aloft


Mass of Air

Prevailing

Wind

direction

Expands due to less pressure aloft.


Mass of Air

Prevailing

Wind

direction

Expansion causes air to cool.


Mass of Air

Prevailing

Wind

direction

When temp. reaches its dew pt. Temp., Condensation occurs.


Prevailing

Wind

direction

A cloud is

Born!

Cloud FormationWindward side of Mtns. are

Cool and Moist climates.

Leeward side of Mtn

Prevailing

Wind

direction

A cloud is

Born!


Prevailing

Wind

direction


Prevailing

Wind

direction

Air mass will sink.


Prevailing

Wind

direction

Air will be compressed by increasing air pressure and air temp. will increase


Prevailing

Wind

direction

The difference between air temp. and dew pt. temp. will become greater and cause relative humidity to decrease.

Cloud FormationWindward side of Mtn. Leeward side of Mtns. are

warm and dry climates.

Prevailing

Wind

direction

Documents

The present condition of the atmosphere is called weather and can be described by the following weather variables: Temperature Air Pressure Humidity