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Atmosphere 2
1. The document discusses various methods for measuring weather conditions such as air pressure, wind speed, and direction including mercury barometers, aneroid barometers, electric barometers, and anemometers. 2. It describes global wind patterns including the Hadley cell, Ferrel cell, and polar cell circulation caused by uneven heating of the Earth and the Coriolis effect. 3. Various types of storms are outlined like thunderstorms, tornadoes, and hurricanes explaining how they form from different air mass interactions and safety procedures during severe weather.
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Atmosphere 2
- 1. 1 ATMOSPHERE 2: Weather ppt. byRobin D. Seamon
- 2. 2 How do wemeasure Weather?
- 3. 3 MEASURING AIR PRESSURE Airpressure: weight of air; exerted in all directions • Mercury Barometer- • Inverted tube in a bath of Mercury; • Air pressure pushes down on the Mercury bath, causing the Mercury to go up the tube
- 4. 4 • Aneroid Barometer-portable • Metal chamber partially emptied of air (vacuum) with elastic top • As air pressure changes, the chamber compresses or expands • Pointer indicates level of change
- 5. 5 • Electric Barometer-portable 1. Calibrate device: set barometer to local air pressure setting (altitude) since factory settings are at sea level 2. Place barometer- (Avoid AC rooms, sunlight, drafty rooms) 3. Reference device: Set manual hand to current reading 4. Check device for change in pressure Daily changes: 0.02 – 0.10 inch
- 6. 6 5. Forecasting Weather •Pressure falls: indicates storms & rain • Pressure rises: fair weather • Pressure steady: more of the same
- 7. 7 WIND Wind: horizontal differencesin air pressure; air moves from areas of high pressure to areas of low pressure • pressure gradient- spacing of isobars show amount of pressure change over a distance • Isobars- closer spaced isobars = steep pressure gradient/high winds
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- 9. 9 WIND : 1. Pressuredifference: Solar radiation unevenly heating atmosphere 2. Coriolis effect: Earth’s rotation affects movement of objects; deflects objects to the right in N Hemisphere 3. Friction: slows air masses near the surface
- 10. 10 Pressure difference: Solarradiation unevenly heating atmosphere
- 11. 11 Coriolis effect: Earth’srotation affects movement of objects; deflects objects to the right in N Hemisphere Actual Movement Direction of Movement
- 12. 12 Friction: • Friction Layer:landforms slow air masses near the surface • Jet stream: high, fast moving air above the friction layer; West to East direction
- 13. 13 HIGHS and LOWS Highs-Anticyclones • Areas of high pressure • Pressure increases from outer isobars towards center
- 14. 14 •Big Blue H •EXAMPLE:warm air mass stays low to the ground, pushing on the ground.) •At ground: swirling cool, dry air •Fair weather •Clockwise swirl in N Hemisphere “Hi! How are you?” arms HIGH PRESSURE SYSTEMS H
- 15. 15 HIGHS and LOWS Lows-Cyclones • Areas of low pressure • Pressure decreases from outer isobars toward center
- 16. 16 •Big Red L •EXAMPLE:warm air mass lifts and moves vertically, causing less pressure on the ground.) •At ground: warm, moist air, strong winds •Severe weather/ thunderstorms •Counter clockwise swirl in N Hemisphere Feeling “low” running away arms LOW PRESSURE SYSTEMS L L
- 17. 17 GLOBAL WINDS Because ofuneven heating of Earth, the atmosphere acts as a giant heat-transfer system to maintain balance Non-rotating Earth Model Rotating Earth Model 2 cell-convection Multi-cell convection
- 18. 18 LOW pressure LOW pressure LOWpressure HIGH pressure HIGH pressure
- 19. 19 LOW pressure LOW pressure LOWpressure HIGH pressure HIGH pressure Polar Air Circulation Ferrel Air Circulation Hadley Air Circulation
- 20. 20 LOW pressure LOW pressure LOWpressure HIGH pressure HIGH pressure Polar Air Circulation Ferrel Air Circulation Hadley Air Circulation Polar Easterlies Westerlies NE Trade winds SE Trade winds
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- 23. 23 MEASURING WIND Wind speed: anemometer-measures wind speed
- 24. 24 Wind Direction Prevailing windsin the US: • from West to East
- 25. El Nino- partof GLOBAL WEATHER • Cold Peruvian current flows toward equator, allowing upwelling & good fishing • In December, warm waters replace the current, lasting for a few weeks, upsetting weather patterns; blocking upwelling; inland areas get more rain than usual 25
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- 28. 28 Air Masses m Maritime: originsover the ocean c Continental: origins over continents P Polar: low humidity T Tropical: high humidity
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- 31. 31 cool, rainy weather LAKES: make Snowy weather warm,wet weather warm, dry weatherwarm, wet weather cool, snowy weather cool, dry weather mP cP mP cT mT mT
- 32. 32 Front: boundary between twoair masses
- 33. 33 WARM FRONT • Warmair moves into an area formerly covered by cooler air • Hard to move the cooler & denser air, so it slowly rides on top of it… Creates HEAVY (High) pressure • Associated with stable, fair weather, possible light rain if front remains for a few days
- 34. 34 Half circles… SMOOTH& SLOW Half circles on the side the front is moving
- 35. 35 COLD FRONT • Cold,dense air moves into a region occupied by warmer air • Forceful lifting of warm, wet air causes instability; thunderstorms & strong wind • Faster front because it’s denser
- 36. 36 Faster b/c denser Triangleson the side the front is moving Triangles… SHARP CUT & FAST
- 37. 37 STATIONARY FRONT • Whenair flow on either side is neither toward cold mass or warm mass • Stable • Sometimes, gentle precipitation
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- 39. 39 OCCLUDED FRONT • Whenan active cold front moves fast & overtakes a warm front • Wedges the warm air upwards causing heavy rain • Front moves slowly, so rains for several days
- 40. 40 OCCLUDED FRONT When acold front overtakes a warm front that was moving ahead of it.
- 41. 41 Middle Latitude Cyclones Largecenters of low pressure, moving West to East, causing stormy weather • between 30° and 60° latitude US WEATHER REMEMBER:
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- 44. 44 STORMS Thunderstorm- storm generatinglightening &b thunder • 2,000 thunderstorms happening at any given time; highest number in the tropics (warm, humid) • Southeast US • Warm, humid air rises in an unstable environment
- 45. 45 TORNADO Tornado- violent windstorms,rotating column of air called a vortex • US: 770 tornadoes each year • Form in updraft of a thunderstorms
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- 49. 49 Tri-State Tornado: March 18,1925 • killed 695, injured 2,027 • 300 miles • Missouri • Illinois • Indiana
- 50. 50 Tornado Warning System •Issued by National Weather Service Watch: conditions are favorable for a tornado Warning: a tornado has been spotted; seek shelter immediately
- 51. 51 TORNADO SAFETY • Goto low ground: basement, ditch • Avoid windows • Leave mobile home • At school: follow the drill- interior hallway, cover head • Leave vehicle, find a low ditch, cover head AFTER: • Do NOT touch downed power lines or sharp objects • Stay out of heavily damaged buildings
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- 53. 53 HURRICANE Hurricane- whirling tropicalcyclones producing winds of at least 74 mph • Name is regional: • Hurricane • Typhoon • Cyclone • Tropical cyclone • Associated with storm surges and flooding • Occurrences seem to be increasing with global warming
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- 59. 59 Hurricane Katrina August 2005 •Extremely destructive and deadly Category 5 hurricane • 1,800 deaths • Struck Gulf of Mexico • Damage from central Florida to Eastern Texas • New Orleans: sits below sea level & was catastrophically flooded VIDEO Katrina (5 min)
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- 61. 61 HURRICANE SAFETY • Easilypredicted, so pay attention to weather forecasts • Prepare: food, water, flashlight, first aid kit • Stay indoors during hurricanes • Heed local warnings; if an evacuation is called, LEAVE before the hurricane • Know evacuation routes
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