1. Air Pressure and Wind 5 th Grade Science

2. Changes in Air Pressure Volume Elevation Humidity –Water vapor molecules weigh less than oxygen –Moist air has less pressure than dry air Temperature –Hot air molecules speed up and spread out –Hot air weighs less and has less pressure than cold air –WARM AIR RISES

3. High Pressure, Low Pressure, Isobars, oh my! Isobars: areas of equal air pressure on a weather map (white lines) High Pressure (H) center of the storm has a higher pressure, winds blow outward from the center in a clockwise pattern Low Pressure (L) the center of the storm has a lower pressure, winds blow toward the center in a counterclockwise pattern

4. Weather Station Model Temperature Wind speed Wind direction Air pressure changes Air pressure

5. What causes wind? Wind is named for where it comes from Air that moves horizontally is wind Air that rises is an updraft Air that sinks is a downdraft Convection cell –WARM AIR RISES –Unequal heating and cooling DowndraftUpdraft

6. Land and Sea Breezes Land heats and cools faster than water Wind that blows from the sea towards land is called a sea breeze (Day) Wind that blows from the land towards the sea is called a land breeze (Night) Valleys and Mountains: Valley breeze during the day and mountain breeze at night

7. Coriolis Effect Earth’s rotation causes the wind to curve Northern hemisphere curves to the right Southern hemisphere curves to the left

8. Global Wind Patterns Coriolis Effect + convection cells = global wind patterns We live in the prevailing westerlies This means our weather moves from WEST to EAST across the U.S.