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Part I Climate Concepts WEATHER: Temporary state of atmosphere CLIMATE: Average weather conditions in an area over a long period of time PRECIPITATION: Moisture received as rain, snow, sleet and hail What Makes Some Areas So Hot? And Others So Cold? Why Are Some Areas So Dry? While Others Extremely Wet? What Creates Our Climate? What Creates Earth’s Climates? • • • • • • Latitude Ocean Currents Wind Patterns Mountain Barriers Altitude (elevation) Proximity to Oceans Part II Earth’s Relationship with the Sun The angle of the sun's rays and the surface of the earth varies with latitude Sunlight that strikes a surface at an angle is spread over a larger area than sunlight that strikes the surface directly Sun’s Angle Varies by Season TROPIC OF CANCER (23½oN) TROPIC OF CAPRICORN (23½oS) The northern most and southern most points on which the direct rays of the sun fall on the earth Tropics Regions that lie between the Tropics of Cancer and Capricorn that are generally warm and wet ARCTIC CIRCLE (66½oN) ANTARCTIC CIRCLE (66½oS) North of the Arctic Circle and south of the Antarctic Circle where there is 24-hour sunshine in summer and 24-hour darkness in winter Solstice • Twice a year when Earth’s poles point at their greatest angle towards or away from the Sun (around June 21 and December 21) Equinox • Twice a year when Earth’s poles are equal distance from the Sun (around March 21 and September 23). A time of equal light and darkness on Earth. Part III Climate Factors L ATITUDE O W M A P Climate Factors L ATITUDE O W M A P Sun's rays strike earth most directly over the tropics, so temps are warmer near the equator and cooler towards the poles Part III Ocean Currents Climate Factors L ATITUDE O CURRENTS W CEAN M A P Sun's rays strike earth most directly over the tropics, so temps are warmer near the equator and cooler towards the poles Prevailing Ocean Currents Bring warmer or cooler temperatures than normally expected Ocean Currents Effect Climate Winds blow off them warming or cooling nearby areas as well as bringing precipitation Warm Ocean Currents Southern Alaska experiences long, mild summer days because of latitude and warm ocean currents Infrared aerial satellite photo shows variation in ocean temperatures Climate Factors L ATITUDE O CURRENTS W CEAN M A P Sun's rays strike earth most directly over the tropics, so temps are warmer near the equator and cooler towards the poles Climate Factors L ATITUDE O CURRENTS W CEAN M A P Sun's rays strike earth most directly over the tropics, so temps are warmer near the equator and cooler towards the poles Winds blowing off ocean currents affect temperatures by making places warmer or cooler than normally expected Part IV Wind Patterns Climate Factors L ATITUDE O CURRENTS IND W PATTERNS CEAN M A P Sun's rays strike earth most directly over the tropics, so temps are warmer near the equator and cooler towards the poles Winds blowing off ocean currents affect temperatures by making places warmer or cooler than normally expected Why Does Wind Blow? What Direction Does Wind Blow? • Unequal heating on Earth’s surface creates “high” and “low” pressure • Cold air is heavy and sinks creating high pressure • Heated air rises creating less downward force (low pressure) • Winds from high pressure blow in to take the place of rising air (like a vacuum) • So wind blows from high to low pressure High Pressure • Air pressure is “high” when cool, heavy air is descending (often too slowly to feel) • High pressure is usually associated with pleasant, dry weather • Earth’s polar areas consistently have high pressure because of the sun’s indirect rays Low Pressure • When air is heated it rises creating “low” pressure • Low pressure is often associated with bad weather • Because it gets more direct sunlight, Earth’s tropical regions are often associated with low pressure • Hurricanes are low-pressure storms that move towards high pressure Wind Patterns • Water changes temperatures slower than air • As a result, wind brings cool breezes from oceans during the day • At night winds usually blows off the land towards the cooler ocean Wind Belts Wind Direction • Air does not always flow directly from high to low • Since the Earth rotates the winds are deflected to the right in the Northern Hemisphere (and to the left in the Southern Hemisphere) Coriolis Effect Prevailing Wind Patterns Global Prevailing Winds Polar Easterlies 60oN Westerlies o 30 N Northeast Trade Winds 0 o Southeast Trade Winds 30oS Westerlies Polar Easterlies 60oS Infrared satellite photo showing moisture being delivered by prevailing winds Climate Factors L ATITUDE O CURRENTS W IND PATTERNS CEAN M A P Sun's rays strike earth most directly over the tropics, so temps are warmer near the equator and cooler towards the poles Winds blowing off ocean currents affect temperatures by making places warmer or cooler than normally expected Unequal heating of the earth creates prevailing winds which bring precipitation and warm or cool air Part V Climate Factors L ATITUDE O CURRENTS W IND PATTERNS CEAN M A LTITUDE P Sun's rays strike earth most directly over the tropics, so temps are warmer near the equator and cooler towards the poles Winds blowing off ocean currents affect temperatures by making places warmer or cooler than normally expected Unequal heating of the earth creates prevailing winds which brings precipitation and warm or cool air Altitude Altitude • Altitude (or elevation) is the height of the land above sea level • Highest: Mt. Everest (29,029’) • Lowest: Dead Sea (-1369’) Altitude = Temps • Gravity creates a downward pull on Earth’s atmosphere • Fewer gases in the air holds less heat o • Temperatures decline 1 F for every 300’ increase in altitude (or elevation) • So high elevations often cold Climate Change Based on Altitude La Paz, Bolivia Climate Factors L ATITUDE O CURRENTS W IND PATTERNS CEAN M A LTITUDE P Sun's rays strike earth most directly over the tropics, so temps are warmer near the equator and cooler towards the poles Winds blowing off ocean currents affect temperatures by making places warmer or cooler than normally expected Unequal heating of the earth creates prevailing winds which brings precipitation and warm or cool air Temperatures decrease 1oF for every 300' increase in altitude (elevation). Thinner air has less ability to hold heat Part VI Climate Factors L ATITUDE O CURRENTS W IND PATTERNS CEAN M BARRIERS A LTITUDE Sun's rays strike earth most directly over the tropics, so temps are warmer near the equator and cooler towards the poles Winds blowing off ocean currents affect temperatures by making places warmer or cooler than normally expected Unequal heating of the earth creates prevailing winds which brings precipitation and warm or cool air OUNTAIN P Temperatures decrease 1oF for every 300' increase in altitude (elevation). Thinner air has less ability to hold heat Mountain Barriers Orographic Effect Sierra Nevada Mountains Western Side: Eastern Side: WINDWARD LEEWARD Sierra Nevada Mountains Blocks Moisture Coming Off Pacific Ocean Death Valley Climate Factors L ATITUDE CEAN O CURRENTS W IND PATTERNS Sun's rays strike earth most directly over the tropics, so temps are warmer near the equator and cooler towards the poles Winds blowing off ocean currents affect temperatures by making places warmer or cooler than normally expected Unequal heating of the earth creates prevailing winds which brings precipitation and warm or cool air M OUNTAIN BARRIERS The orographic effect of mountains causes precipitation to fall on one side (windward) leaving the other side dry (leeward) A LTITUDE P Temperatures decrease 1oF for every 300' increase in altitude (elevation). Thinner air has less ability to hold heat Part VII Climate Factors L ATITUDE O CURRENTS W IND PATTERNS CEAN M BARRIERS A LTITUDE OUNTAIN P ROXIMITY TO OCEANS Sun's rays strike earth most directly over the tropics, so temps are warmer near the equator and cooler towards the poles Winds blowing off ocean currents affect temperatures by making places warmer or cooler than normally expected Unequal heating of the earth creates prevailing winds which brings precipitation and warm or cool air The orographic effect of mountains causes precipitation to fall on one side (windward) leaving the other side dry (leeward) Temperatures decrease 1oF for every 300' increase in altitude (elevation). Thinner air has less ability to hold heat Proximity to Oceans • Ocean temperatures change little during the year • Winds blowing off oceans are rarely extremely hot or cold • Places near oceans often experience moderate temperatures (whether there’s ocean currents or not) Proximity to Oceans Geographic Center of No. America Continentality Continentality Continentality = 4 Seasons Continentality in Minnesota Climate Factors L ATITUDE O CURRENTS W IND PATTERNS CEAN M BARRIERS A LTITUDE OUNTAIN P ROXIMITY TO OCEANS Sun's rays strike earth most directly over the tropics, so temps are warmer near the equator and cooler towards the poles Winds blowing off ocean currents affect temperatures by making places warmer or cooler than normally expected Unequal heating of the earth creates prevailing winds which brings precipitation and warm or cool air The orographic effect of mountains causes precipitation to fall on one side (windward) leaving the other side dry (leeward) Temperatures decrease 1oF for every 300' increase in altitude (elevation). Thinner air has less ability to hold heat Distance from oceans causes greater seasonal range in temperatures known as continentality. Nearness moderates temps Wind Belts