ThursdayApril 21, 2011

(World Distribution of Temperature;

Atmospheric Pressure)

The Launch PadThursday, 4/21/11

Define the term “air mass.”

A very large body of air, covering thousands of square miles, that

contains similar temperature and humidity conditions throughout.

Announcements

Please check your yearly average in this class.

If you are below 70 for the year, please come and see

me ASAP!There are only two more

grades remaining!

Assignments For This Six-Weeks Date Issued Date Due

Lab – Air Masses, the Mid-Latitude Cyclones, and Weather Maps 4/20 4/25

World Distribution of Temperature Temperature maps help analyze temperature distribution over given

areas. Temperatures are adjusted to sea level to eliminate the variable of

altitude.January and July are used for analysis because they represent the

temperature extremes.

World Distribution of Temperature

On these maps, an

isotherm is a line

connecting places of

equal temperature.

World Distribution of Temperature

On a global scale, temperature

patterns emerge. The temperature

decreases poleward from the tropics.

Isotherms exhibit a latitudinal shift

with the seasons.The warmest and

coldest temperatures occur

over land.

World Distribution of Temperature

In the Southern Hemisphere, isotherms are straighter and

more stable. Isotherms show the annual temperature range of ocean

currents. Ranges are small near the

equator, and increase with an increase in latitude

Ranges are greatest over continental locations.

World Mean Sea-Level Temperatures in January

World Mean Sea-Level Temperatures in July

Atmospheric Pressure Atmospheric pressure is the

force exerted by the weight of the air above.

The weight of the air above at sea level is 14.7 pounds per

square inch.

This pressure decreases with increasing altitude.

A common measurement unit of atmospheric pressure is the

millibar (mb).

Standard sea level pressure is 1013.2 mb.

Atmospheric Pressure Another unit used in

atmospheric pressure measurement is inches of

mercury.

Standard sea level pressure is 29.92 inches of mercury.

The instrument used for measuring atmospheric

pressure is the barometer.

The mercury barometer was invented by Torricelli in 1643.

It uses a glass tube filled with mercury.

Atmospheric Pressure Another type of barometer is the aneroid barometer, meaning “without liquid.”

This type of barometer uses an expanding

chamber. Another pressure instrument is the barograph, which

continuously records the air pressure.

Continue LabAir Masses, the Middle-Latitude

Cyclone, and Weather Maps