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Weather Patterns

Weather Patterns. The atmosphere’s air pressure changes Weather : condition of Earth’s atmosphere at a particular time and place. Wind is an important part of weather Wind : air that moves horizontally or parallel to the ground, moves from a higher pressure toward lower pressure

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Weather Patterns

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  1. Weather Patterns

  2. The atmosphere’s air pressure changes Weather: condition of Earth’s atmosphere at a particular time and place. Wind is an important part of weather Wind: air that moves horizontally or parallel to the ground, moves from a higher pressure toward lower pressure Warmer air rises Cooler air sinks Low Pressure High Pressure Barometer – instrument used to measure atmospheric pressure

  3. The atmosphere has wind patterns Caused by the uneven heating between the equator and the North and South poles Forms because Earth’s surface is heated unevenly Travel thousands of Km in steady patterns Global Winds The sinking dense air produces high pressure that sets global winds in motion Last for weeks

  4. Influenced by Earth’s rotation Noticeable only for winds that travel long distances Southern Hemisphere winds curve to the left Coriolis Effect Northern Hemisphere winds curve to the right

  5. Winds are light and often change direction Air stays calm in HP and LP zones Calm Regions DOLDRUMS HORSE LATITUDES LP zones near the equator HP zones located about 300 N and 300 S of the equator Warm air rises to top of troposphere Warm air traveling away from the equator cools and sinks Rising, moist air produces clouds and heavy rain Weather tends to be clear & dry

  6. WIND BELTS TRADE WINDS EASTERLIES WESTERLIES Blow from the East Blow from the west Blow from the east Strong & steady winds Stormy weather Bring storms across the U.S. Die out as they come near the equator

  7. Loop N and S Air moves at speeds > 200 km/hr Forms because Earth’s surface is heated unevenly JET STREAMS West to East Helps make accurate weather predictions Flow in the upper troposphere

  8. Mountain Breezes Sea Breezes Valley Breezes LOCAL WINDS Land Breezes

  9. LAND BREEZE

  10. SEA BREEZE

  11. Winds that change direction with the season During summer land becomes much warmer than the sea Caused by different heating and cooling rates of land and sea Monsoons During winter land becomes much cooler than the sea Affects large areas Flow longer distances

  12. Most clouds form as air rises and cools Takes the form of water droplets (liquid), water vapor (gas), snow (solid) Condensation: gas changes to a liquid Water always in the atmosphere CLOUDS Evaporation: liquid changes into a gas (* need of extra energy)

  13. Lakes Plants Water Stored Rivers Underground Ice sheets or glaciers

  14. Frost: cold temperatures changes water vapor into a covering of ice Dew: water that condenses on cool surfaces at night Precipitation: any type of liquid or solid water that falls to Earth’s surface Water in the air

  15. Humidity: the amount of water vapor in the air Saturation: rate of evaporation and condensation are equal Varies from place to place Humidity Temperature effects saturation

  16. Amount of water vapor in air Relative Humidity 50% R. humidity ½ of the water before air is saturated

  17. The amount of water to saturate the air Dew Point How do clouds form Dew point of air the more water vapor it contains Warm air rises Cools Reaches dew point Location affects the composition of clouds Water vapor condenses Forms droplets or crystals

  18. 3 MAIN TYPES OF CLOUDS • Cumulus – heap or piles, produces brief showers, puffy white, dark bases, cumulonimbus produce thunder storms, can grow very tall • Stratus – flat layers, dark, produce steady showers, produce circles of light around the sun or moon • Cirrus – feathery wisps, sign of storms, made of ice crystals, forms in cold air at high altitude, has strong winds Fog – clouds that rest on the ground or a body of water usually forms when a surface is cooler than the air above it

  19. Water falls to Earth’s surface as precipitation. • Precipitation Forms • Crystals become heavy then fall • Growing of ice crystals • Combining of cloud droplets Measure Precipitation • Rain Gauge • Measure snow with a ruler • Doppler radar shows images of storm systems

  20. Types of Precipitation Snow – ice crystals grow and merge in clouds form snowflakes, flakes come in many different shapes, when they fall through moist air near freezing form clumps, dry colder air don’t clump and snow is powdery Hail – forms when ice pellets move up and down in clouds growing larger as they gain layers of ice, comes during warmer weather, fall from cumulonimbus clouds during thunderstorms, can vary in size to dime size to softball size Sleet – freezes before it hits the ground, small pellets of ice, rain passes through cold air

  21. Types of Precipitation (cont.) Rain & Drizzle – comes from Stratus clouds, most common type of precipitation, forms from cloud droplets, light rain = drizzle Freezing rain – can bring down trees & power lines, covers surfaces with ice

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