Air Pressure – the force that air exerts on the surface of Earth per unit of area

Average Air Pressure at Sea Level 1 bar 1013 millibars 14. 7 psi 29 Average Air Pressure at Sea Level 1 bar 1013 millibars 14.7 psi 29.92 in Hg 760 mm Hg The normal range of the Earth's air pressure is from 980 millibars (mb) to 1050 mb.

MERCURY BAROMETER

ANEROID BAROMETER

ANEROID BAROMETER

Air pressure varies due to: altitude temperature water vapor

Air Pressure  Temperature / Humidity / Elevation 

N2 O2 N2 N2 N2 O2 H2O N2 N2 N2

Atomic Masses (Rounded off) H = 1 amu N = 14 amu O = 16 amu

N2 28 amu O2 N2 N2 N2 O2 32 amu H2O N2 28 amu N2 N2

H2O 18 amu O2 N2 N2 N2 H2O 18 amu H2O H2O 18 amu N2 N2

WIND

Winds are created by differences in air pressure due to unequal heating of air

Wind is air moving from HIGH PRESSURE areas to low pressure areas

H ------ L

Why does air move from high pressure to low pressure? 11

N2 O2 N2 N2 N2 O2 H2O N2 N2 N2

●990 mb ●988 mb ●988 mb ●989 mb ●990 mb ●997 mb ●994 mb ●992 mb ●996 mb ●1000 mb ●994 mb ●1000 mb ●999 mb ●996 mb ●996 mb ●998 mb ●994 mb ●992 mb ●991 mb ●990 mb

●989 mb ●995 mb ●988 mb ●996 mb ●994 mb ●992 mb ●991 mb ●998 mb ●996 mb ●996 mb ●1000 mb ●997 mb ●999 mb ●996 mb ●1001 mb ●999 mb ●1001 mb ●1001 mb ●1003 mb ●1000 mb

●999 mb ●995 mb ●1002 mb ●996 mb ●994 mb ●997 mb ●1000 mb ●994 mb ●991 mb ●993 mb ●995 mb ●994 mb ●990 mb ●999 mb ●995 mb ●996 mb ●996 mb ●998 mb ●1001 mb ●1000 mb

●1015 mb ●1005 mb ●1020 mb ●1000 mb ●1007 mb ●1014 mb ●1020 mb ●1001 mb ●1006 mb ●1011 mb ●1000 mb ●1013 mb ●1007 mb ●1019 mb ●1003 mb ●1015 mb ●1006 mb ●1010 mb ●1002 mb ●1018 mb

What direction is the wind blowing? Where are the winds strongest? Where are the winds weakest? What is the weather like in Stoneham? What will the weather be like in the near future?

What direction is the wind blowing? Where are the winds strongest? Where are the winds weakest? What is the weather like in Stoneham? What will the weather be like in the near future?

What direction is the wind blowing? Where are the winds strongest? Where are the winds weakest? What is the weather like in Stoneham? What will the weather be like in the near future?

What direction is the wind blowing? Where are the winds strongest? Where are the winds weakest? What is the weather like in Stoneham? What will the weather be like in the near future?

Great Lakes Oregon Mass Colorado Texas Baja Cali Florida

Local Winds

Global Winds

The Coriolis Effect

9

L 1000 1015

H 1015 1000

Doldrums?

Why does it rain a lot at the equator?

Why is weather generally considered nice at 30 degrees?