Transcript File
Air Earth’s Atmosphere Atmospheric Pressure * The weight of the air above you. The more air that is above you the more pressure you will feel. * Sinking air pushes down more- cold air is usually high pressure. * Rising air pushes down lesshot air is usually low pressure. Where is pressure greater, at top of a mountain or at sea level? Sea level So …. Atmospheric pressure is greatest near Earth’s surface Decreases as you move out to space Can vary from locations at the same level due to the density of the air Cold Air vs. Warm Air Cold air is denser than warm air so has a higher pressure Warm is less dense so has a low pressure These masses of warm/cold air used to predict weather Barometer Measures air pressure Measured in millibars Movement of Air Wind The movement of air molecules from an area of high pressure to an area of low pressure Temperature differences on Earth’s surface create areas of different pressure and the winds that circulate our planet Causes of temperature difference Earth is curved rather than flat so more solar radiation is received at the equator Air above equator is heated more than any place on Earth … heated air rises (low pressure) Air above poles receives less radiation so air is cooler … colder air sinks (high pressure) The Coriolis Effect Due to Earth’s rotation Causes air masses moving south in Northern Hemisphere to be turned westward from their original paths These wind patterns determine the weather and also when ships/planes can travel Review ….. What 2 things determine our wind patterns on Earth ? Differences in heating Coriolis effect Global Wind Systems Trade winds Westerlies Easterlies Doldrums Jet Streams Located near top of troposphere Flow west to east 2 jet streams in each hemisphere Resemble fast moving rivers Average speed between 97-185 km/h Their positions in altitude and latitude from day to day / season to season Jet Stream Local Wind Systems Land Breezes Movement of air towards water Sea Breezes Movement of air towards land Mountain vs. Valley Breezes During DAY, heated air along mountain slopes rises = Valley Breeze At NIGHT, cooled air along mountain slopes moves downward = Mountain Breeze