Winds

=__WTBW 02/01/08__=

=__//Wind//__=

Horizontal Movement of Air
=**__ Pressure differences give wind its push __** = == §  Winds begin with differences in air pressures. Pressure that is higher at one place than another sets up a //__force__// pushing from the high toward the low pressure. == == §  The greater the difference in pressures, the stronger the force. The distance between the area of high pressure and the area of low pressure also determines how fast the moving air is accelerated. == == §  Meteorologists refer to the force that starts the wind flowing as the "//__pressure gradient force__//." ==

 §  There is no set number that divides high and low pressure.
=**__ What's happening inside highs and lows __** = == §   High and low, pressures are important because they affect the weather. The weather maps, such as those on television, show what is happening at the Earth's surface, and that is what we are talking about. == == §   As the name says, a "high" is an area where the air's pressure is higher than the pressure of the surrounding air. A "low” is where it's lower. == == §  Meteorologists do not have any particular number that divides high from low pressure; it is the relative differences that count. ==

=WTBW 2-5-08=

=__ So What Happens to the Weather? __=

== §  The pressure is high at the surface where air is slowly descending - much too slowly to feel and, this is going on over a large area, maybe a few hundred square miles. == == §  As air descends, it warms, which inhibits the formation of clouds. This is why high pressure is generally - but not quite always - associated with good weather. == == §   As air rises, it cools. As the air cools, the //__humidity__// in it begins to condense into tiny drops of water, or if it is cold enough, into tiny ice crystals. == == §  If there is enough water, rain, ice, or snow begins to fall, this is why low pressure is associated with bad weather. ==

=__Pause and Reflect__=

 § Read pages 543-548
== §  __ Square I __ : Explain the formation of land breezes and sea breezes in coastal areas. == == §  __ Square II __ : Draw a chart that compares and contrasts the four (4) types of winds. (Name, Direction, Time, Causes) You may have to use the back of the sheet. ==