Lets try again Cold air Humid air Rainy

Let’s try again! • • Cold air Humid air Rainy day “Nice”weather High Low High (not necessarily warm!) • • Snowstorm July afternoon North Pole Equator Low High Low

So, what makes the pressures different anyway? Adding water vapor to atmosphere & Heating atmosphere up Let’s talk about HEAT

Pressure differences are caused by unequal heating of the Earth’s surface by the sun.

Why do some things get hot faster? • Dark colors absorb more sunlight than light colors. Which gets hot faster: snow or dirt? • Rough surfaces absorb more than smooth. Which gets hot faster: ocean water or beach sand?

Equal volumes of the four samples shown below were placed outside and heated by energy from the Sun’s rays for 30 minutes. The surface temperature of which sample increased at the slowest rate? (1) Snow Light (3) Dark Sand color ed & (2) Copper Pennies (4) Mud Smoo th

Which type of land surface will most likely absorb the greatest amount of incoming solar radiation? (1) rough, dark-colored surface (2) rough, light-colored surface (3) smooth, dark-colored surface (4) smooth, light-colored surface

Remember that pressure differences are caused by unequal heating of the Earth’s surface by the sun. Dark absorbs more… Rough absorbs more…

Should remain cool and higher density ? Maybe a light smooth surface? Should become hot and lower density Maybe a dark rough surface?

Air not only rises or sinks, it also moves naturally from where there is more (H) to where there is less (L). R ts? r a f r e ememb

• Ground is heated sun is… Thebyeffect • Atmosphere above ground warms up • Warmer air becomes less dense and rises (air current) • Rising air “gives off” heat energy and cools • Cooler air becomes more dense and sinks (air current) And of course air moves across ground from High (more air)to Low (less air). (wind!) The effect can be local or planetary, so let’s examine Earth’s wind…

The cross section shows a sea breeze blowing from the ocean toward the land. The air pressure at the land surface is 1013 mb. The air pressure at the ocean surface a few miles from the shore is most likely (1) 994 mb (3) 1013 mb (2) 1005 mb (4) 1017 mb

current H COOL Convection cell WIND current L WARM

• Wind is the result of air pressure differences. • Pressure difference is better called gradient. • The larger the pressure gradient, the stronger the wind. • Which pressure gradient creates a stronger wind: 1. 8 mb/Km or 7 mb/Km ?

If the distance between these two points is 500 Km, what is the pressure gradient?

The pressure gradient –wind effect —is not only a localized effect. It is also a global effect. Let’s examine the winds of the Earth. . .

Does entire planet get equally heated? Less heat High More heat Less heat Low High

Which graph best represents the change in air pressure as air temperature increases at Earth’s surface? Hot , Less Dense Air Rises!

H L

According to the ESRT the prevailing winds in White Plains, NY tend to come from the 1) Northeast 3) Southeast 2) Northwest 4) Southwest

http: //www. weather. gov/data/obhistory/KHPN. html

OUC H!

After sunrise, a surface wind often develops between the water and land at the shore. This wind is due to the heat of the Sun. Which map below best represents the direction of this wind?