Meteorology Unit II:
Meteorology Unit II: Air Pressure & Winds Lows & Highs TB Ch. 19 BFRB Pressure & Winds P. 172-182 Lows & Highs P. 180 - 182
Regents Earth Science Mrs. O’Gorman
Name: __________________
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Pressure is determined by using a barometer measured in millibars (mb) or inches of Hg (in)
Relative Humidity is determined by using a hygrometer or a sling psychrometer measured as a %
Wind direction is determined by using a wind vane or a wind sock (like you see at the airport) measured as a compass direction N, S, NE, SW, etc.
Temperature is determined by using a thermometer measured in °C,°F, or K
Amount of precip is measured by using a rain gauge measured in inches or cm
wind vane
Wind speed is measured using an anemometer (units are knots; 1 knot = 1.15 mph)
Meteorology Instruments
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What is Air Pressure? How do we measure air pressure? Page 4 of 63
Air Pressure • the weight of the air in a certain area • Air pressure is measured using an instrument called a barometer (aneroid or mercury) • It is measured in inches (height of the mercury column in the barometer), or with the metric units called millibars • Use your reference tables for “converting” inches to millibars • (ESRT’s Page 13 Right Top)
• FYI – the increments are not the same on both sides. Figure out each sides’ increments and write them in right now…
• Right here tells you which side is millibars and which side is inches Millibars: Increment = __________
Inches: Increment = __________
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Name: ________________________________
Per #: ___________
Directions: Use the ESRT’s to help you complete the following conversions. BE SURE TO FIRST DETERMINE THE INCREMENT OF THE SCALE, THEN READ OFF THE PRECISE MEASUREMENT!!!!!!
Pressure Conversions
Convert the following from millibars to inches. 1. 2. 3. 4. 5.
Inches ______________ ______________ ______________ ______________ ______________
Millibars 1040.0 973.0 1013.2 1000.0 1013.0
Convert the following from inches to millibars. Inches 6. 30.50 7. 30.00 8. 29.40 9. 28.70 10. 29.30
Millibars ______________ ______________ ______________ ______________ ______________
What is one atmosphere of pressure in millibars? _______ What is one atmosphere of pressure in inches? _______
Temperature Conversions
Convert the following from Fahrenheit to Celsius. Fahrenheit 11. 32F 12. 98F 13. 212F 14. 140F 15. -20F
Celsius ______________ ______________ ______________ ______________ ______________
Convert the following from Celsius to Fahrenheit. Celsius 16. 80C 17. 20C 18. 12C 19. -39C 20. 32C
Fahrenheit ______________ ______________ ______________ ______________ ______________
Convert the following from Celsius to Kelvin. Celsius 21. 0C 22. 100C 23. 50C 24. -50C 25. 75C
Kelvin ______________ ______________ ______________ ______________ ______________ Page 6 of 63
What factors affect air pressure?
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Changes in Air Pressure • Air pressure decreases with increasing altitude (less air above you means less pressure pushing down on you) • This is an inverse (indirect) relationship • Weather maps show sea level air pressure. It ranges from 960mb – 1050mb • Isobars are lines on the weather maps which connect areas of equal air pressure • VIF!!!! - The same rules apply for isobars as isotherms and contour lines. If the isobars are spaced close together, the pressure gradient is steep and winds are fast.
Changes in Air Pressure • How does temperature affect air pressure? • Warm air’s molecules are further apart than cold air’s molecules! • It is less dense and not as many molecules are on top of an area to add pressure. • Therefore, as temperature increases , air pressure _________________. • This is a(n) ______________ relationship.
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Changes in Air Pressure • How does humidity (the amount of water vapor held in a parcel of air) affect air pressure? • Humid (moist) air contains more water vapor molecules (H2O) • These H2O molecules have less atomic mass than N2 and O2 molecules that they take the place of!!! • Let’s PROVE it!!!!!
Changes in Air Pressure • How does humidity (the amount of water vapor held in a parcel of air) affect air pressure? • OK so we just proved that humid air actually weighs less than dry air. • So, as humidity increases, air pressure ____________________. • This is a(n)_________________ relationship.
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How do winds circulate on a small, daily scale?
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Winds and Air Pressure • Winds are caused by the unequal heating of the atmosphere (remember that temperature causes changes in air pressure) • Warm air is lighter (lower pressure) and colder air is heavier (higher pressure) • Remember…warm stuff rises and cold stuff sinks… – Ex: Sea breezes and land breezes
Sea Breeze – the surface wind is blowing in FROM the sea.
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Land Breeze – the surface wind is blowing out FROM the land.
Another view of sea breezes and land breezes…
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Name: _____________________________________________________ Pd.: ________ Date: ______________________
Homework – Sea and Land Breezes Below is a question from a released SOL or similar test. Answer the questions on the right about the SOL question. 1. Circle the correct term in the parentheses that correctly completes the sentence. Warm air ( rises / sinks ) and cool air ( rises / sinks ). 2. On the Sea Breeze part of the diagram put a large ‘L’ where the pressure would be the lowest. 3. On the Sea Breeze part of the diagram put a large ‘H’ where the pressure would be the highest. 4. On the Sea Breeze part of the diagram write the word ‘cooler’ on which ever is cooler, the land or the water. 5. On the Sea Breeze part of the diagram write the word ‘warmer’ on which ever is warmer, the land or the water. 6. On the Land Breeze part of the diagram put a large ‘L’ where the pressure would be the lowest. 7. On the Land Breeze part of the diagram put a large ‘H’ where the pressure would be the highest. 8. On the Land Breeze part of the diagram write the word ‘cooler’ on which ever is cooler, the land or the water. 9. On the Land Breeze part of the diagram write the word ‘warmer’ on which ever is warmer, the land or the water. 10. Consider answer choice ‘F’. Is the water always cooler than land? 11. Consider answer choice ‘G’. Using your textbook as a reference, what holds heat the longest, the land or the ocean? 12. Look at answer choice ‘H’. Using your answer to question #1 above, is ‘H’ possible or impossible? 13. Look at answer choice ‘J’. Using your textbook or common sense, does the sun heat air differently depending on whether that air is over land or water? 14. Answer the SOL question. Page 22 of 63
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What is meant by High Pressure and Low Pressure? How are Lows and Highs shown on a weather map? Page 24 of 63
Winds on a Larger Scale
• Winds blow out of high pressure and into low pressure (from higher density to lower density) • The change in pressure (∆field value) divided by the distance between the measured pressures is called the pressure gradient. • The greater the change in pressure between two locations, the faster the wind speed (this is called a steep pressure gradient) • A steep pressure gradient is shown on a weather map by closely spaced isobars (think of closely space contour lines on a topographic map – steeper slope)
Weather Map with Highs, Lows and a Hurricane!
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Isobars are ___________ spaced resulting in a ___________ pressure gradient and ___________ winds.
Isobars are ___________ spaced resulting in a ___________ pressure gradient and ___________ winds.
What parts of the US and Canada have the fastest winds? the slowest?
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ISOTHERMS • Temperatures are shown on maps by using Isotherms • These are lines which connect areas of equal temperature • These are very similar to contour lines, and the same rules apply!! • Example – closely spaced isotherms mean a fast change in temperature (steep temp gradient) the same way closely spaced contour lines mean a fast change in elevation (steep land gradient).
Where in the US is the steepest temperature gradient? Where is the gentlest temperature gradient?
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Coriolis Revisited! • The Coriolis Effect (caused by the spin of the Earth) causes winds to deflect to their right in the northern hemisphere • Winds blow out of the High Pressure center (from High to Low pressure) and deflect to their right as they travel, causing a High Pressure System to spin clockwise (anti-cyclonic flow) • Winds blow into the Low Pressure Center (from High to Low Pressure) and deflect to their right as they travel, causing the Low Pressure System to spin counter-clockwise (cyclonic flow) • FYI – Hurricanes and tornadoes are areas of extreme low pressure and always circulate counter-clockwise in the Northern Hemisphere
Source: http://www.goes-r.gov/users/comet/tropical/textbook_2nd_edition/media/graphics/low_cd.gif http://www.goes-r.gov/users/comet/tropical/textbook_2nd_edition/media/graphics/high_cd.gif http://www.goes-r.gov/users/comet/tropical/textbook_2nd_edition/
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H I C A
L I CC C
In a High, the air wants to move directly out from High to Low Pressure but is deflected to its right by the Coriolis Effect, creating a Clockwise flow out from the High.
VIF!!!!!!
In a Low, the air wants to move directly in from High to Low Pressure but is deflected to its right by the Coriolis Effect creating a Counterclockwise flow into the Low.
VIF!!!!!!
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How do winds circulate on a GLOBAL scale?
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Winds on a Global Scale ESRT’s Page 14 Bottom
These planetary winds shift with the seasons due to the changing insolation because of Earth’s tilt! Astronomy connection!!!
3-D Version of the ESRT’s Please note the deflection of the wind to ITS right in the N.H. due to Coriolis Effect
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This is what the air circulation would look like if the Earth DID NOT ROTATE – NO Coriolis Effect!!!!!!
Global View…
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Global Wind Circulation Pressure Belts and Winds
• The jet stream is a narrow zone of high speed air found in the upper troposphere (about 30,000 feet) – Wind speeds here may be over 300 knots! • Large convection currents of air occur on the Earth’s surface due to the unequal heating of the atmosphere
ESRT’s Page 14 Bottom
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Test what you know about air pressure and winds! Page 53 of 63
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Regents Earth Science Mrs. O’Gorman
Name: __________________
Page 1 of 63
Pressure is determined by using a barometer measured in millibars (mb) or inches of Hg (in)
Relative Humidity is determined by using a hygrometer or a sling psychrometer measured as a %
Wind direction is determined by using a wind vane or a wind sock (like you see at the airport) measured as a compass direction N, S, NE, SW, etc.
Temperature is determined by using a thermometer measured in °C,°F, or K
Amount of precip is measured by using a rain gauge measured in inches or cm
wind vane
Wind speed is measured using an anemometer (units are knots; 1 knot = 1.15 mph)
Meteorology Instruments
Page 2 of 63
Page 3 of 63
What is Air Pressure? How do we measure air pressure? Page 4 of 63
Air Pressure • the weight of the air in a certain area • Air pressure is measured using an instrument called a barometer (aneroid or mercury) • It is measured in inches (height of the mercury column in the barometer), or with the metric units called millibars • Use your reference tables for “converting” inches to millibars • (ESRT’s Page 13 Right Top)
• FYI – the increments are not the same on both sides. Figure out each sides’ increments and write them in right now…
• Right here tells you which side is millibars and which side is inches Millibars: Increment = __________
Inches: Increment = __________
Page 5 of 63
Name: ________________________________
Per #: ___________
Directions: Use the ESRT’s to help you complete the following conversions. BE SURE TO FIRST DETERMINE THE INCREMENT OF THE SCALE, THEN READ OFF THE PRECISE MEASUREMENT!!!!!!
Pressure Conversions
Convert the following from millibars to inches. 1. 2. 3. 4. 5.
Inches ______________ ______________ ______________ ______________ ______________
Millibars 1040.0 973.0 1013.2 1000.0 1013.0
Convert the following from inches to millibars. Inches 6. 30.50 7. 30.00 8. 29.40 9. 28.70 10. 29.30
Millibars ______________ ______________ ______________ ______________ ______________
What is one atmosphere of pressure in millibars? _______ What is one atmosphere of pressure in inches? _______
Temperature Conversions
Convert the following from Fahrenheit to Celsius. Fahrenheit 11. 32F 12. 98F 13. 212F 14. 140F 15. -20F
Celsius ______________ ______________ ______________ ______________ ______________
Convert the following from Celsius to Fahrenheit. Celsius 16. 80C 17. 20C 18. 12C 19. -39C 20. 32C
Fahrenheit ______________ ______________ ______________ ______________ ______________
Convert the following from Celsius to Kelvin. Celsius 21. 0C 22. 100C 23. 50C 24. -50C 25. 75C
Kelvin ______________ ______________ ______________ ______________ ______________ Page 6 of 63
What factors affect air pressure?
Page 7 of 63
Changes in Air Pressure • Air pressure decreases with increasing altitude (less air above you means less pressure pushing down on you) • This is an inverse (indirect) relationship • Weather maps show sea level air pressure. It ranges from 960mb – 1050mb • Isobars are lines on the weather maps which connect areas of equal air pressure • VIF!!!! - The same rules apply for isobars as isotherms and contour lines. If the isobars are spaced close together, the pressure gradient is steep and winds are fast.
Changes in Air Pressure • How does temperature affect air pressure? • Warm air’s molecules are further apart than cold air’s molecules! • It is less dense and not as many molecules are on top of an area to add pressure. • Therefore, as temperature increases , air pressure _________________. • This is a(n) ______________ relationship.
Page 8 of 63
Changes in Air Pressure • How does humidity (the amount of water vapor held in a parcel of air) affect air pressure? • Humid (moist) air contains more water vapor molecules (H2O) • These H2O molecules have less atomic mass than N2 and O2 molecules that they take the place of!!! • Let’s PROVE it!!!!!
Changes in Air Pressure • How does humidity (the amount of water vapor held in a parcel of air) affect air pressure? • OK so we just proved that humid air actually weighs less than dry air. • So, as humidity increases, air pressure ____________________. • This is a(n)_________________ relationship.
Page 9 of 63
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How do winds circulate on a small, daily scale?
Page 11 of 63
Winds and Air Pressure • Winds are caused by the unequal heating of the atmosphere (remember that temperature causes changes in air pressure) • Warm air is lighter (lower pressure) and colder air is heavier (higher pressure) • Remember…warm stuff rises and cold stuff sinks… – Ex: Sea breezes and land breezes
Sea Breeze – the surface wind is blowing in FROM the sea.
Page 12 of 63
Land Breeze – the surface wind is blowing out FROM the land.
Another view of sea breezes and land breezes…
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Name: _____________________________________________________ Pd.: ________ Date: ______________________
Homework – Sea and Land Breezes Below is a question from a released SOL or similar test. Answer the questions on the right about the SOL question. 1. Circle the correct term in the parentheses that correctly completes the sentence. Warm air ( rises / sinks ) and cool air ( rises / sinks ). 2. On the Sea Breeze part of the diagram put a large ‘L’ where the pressure would be the lowest. 3. On the Sea Breeze part of the diagram put a large ‘H’ where the pressure would be the highest. 4. On the Sea Breeze part of the diagram write the word ‘cooler’ on which ever is cooler, the land or the water. 5. On the Sea Breeze part of the diagram write the word ‘warmer’ on which ever is warmer, the land or the water. 6. On the Land Breeze part of the diagram put a large ‘L’ where the pressure would be the lowest. 7. On the Land Breeze part of the diagram put a large ‘H’ where the pressure would be the highest. 8. On the Land Breeze part of the diagram write the word ‘cooler’ on which ever is cooler, the land or the water. 9. On the Land Breeze part of the diagram write the word ‘warmer’ on which ever is warmer, the land or the water. 10. Consider answer choice ‘F’. Is the water always cooler than land? 11. Consider answer choice ‘G’. Using your textbook as a reference, what holds heat the longest, the land or the ocean? 12. Look at answer choice ‘H’. Using your answer to question #1 above, is ‘H’ possible or impossible? 13. Look at answer choice ‘J’. Using your textbook or common sense, does the sun heat air differently depending on whether that air is over land or water? 14. Answer the SOL question. Page 22 of 63
Page 23 of 63
What is meant by High Pressure and Low Pressure? How are Lows and Highs shown on a weather map? Page 24 of 63
Winds on a Larger Scale
• Winds blow out of high pressure and into low pressure (from higher density to lower density) • The change in pressure (∆field value) divided by the distance between the measured pressures is called the pressure gradient. • The greater the change in pressure between two locations, the faster the wind speed (this is called a steep pressure gradient) • A steep pressure gradient is shown on a weather map by closely spaced isobars (think of closely space contour lines on a topographic map – steeper slope)
Weather Map with Highs, Lows and a Hurricane!
Page 25 of 63
Isobars are ___________ spaced resulting in a ___________ pressure gradient and ___________ winds.
Isobars are ___________ spaced resulting in a ___________ pressure gradient and ___________ winds.
What parts of the US and Canada have the fastest winds? the slowest?
Page 26 of 63
ISOTHERMS • Temperatures are shown on maps by using Isotherms • These are lines which connect areas of equal temperature • These are very similar to contour lines, and the same rules apply!! • Example – closely spaced isotherms mean a fast change in temperature (steep temp gradient) the same way closely spaced contour lines mean a fast change in elevation (steep land gradient).
Where in the US is the steepest temperature gradient? Where is the gentlest temperature gradient?
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Coriolis Revisited! • The Coriolis Effect (caused by the spin of the Earth) causes winds to deflect to their right in the northern hemisphere • Winds blow out of the High Pressure center (from High to Low pressure) and deflect to their right as they travel, causing a High Pressure System to spin clockwise (anti-cyclonic flow) • Winds blow into the Low Pressure Center (from High to Low Pressure) and deflect to their right as they travel, causing the Low Pressure System to spin counter-clockwise (cyclonic flow) • FYI – Hurricanes and tornadoes are areas of extreme low pressure and always circulate counter-clockwise in the Northern Hemisphere
Source: http://www.goes-r.gov/users/comet/tropical/textbook_2nd_edition/media/graphics/low_cd.gif http://www.goes-r.gov/users/comet/tropical/textbook_2nd_edition/media/graphics/high_cd.gif http://www.goes-r.gov/users/comet/tropical/textbook_2nd_edition/
Page 31 of 63
H I C A
L I CC C
In a High, the air wants to move directly out from High to Low Pressure but is deflected to its right by the Coriolis Effect, creating a Clockwise flow out from the High.
VIF!!!!!!
In a Low, the air wants to move directly in from High to Low Pressure but is deflected to its right by the Coriolis Effect creating a Counterclockwise flow into the Low.
VIF!!!!!!
Page 32 of 63
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Page 34 of 63
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How do winds circulate on a GLOBAL scale?
Page 41 of 63
Winds on a Global Scale ESRT’s Page 14 Bottom
These planetary winds shift with the seasons due to the changing insolation because of Earth’s tilt! Astronomy connection!!!
3-D Version of the ESRT’s Please note the deflection of the wind to ITS right in the N.H. due to Coriolis Effect
Page 42 of 63
This is what the air circulation would look like if the Earth DID NOT ROTATE – NO Coriolis Effect!!!!!!
Global View…
Page 43 of 63
Page 44 of 63
Global Wind Circulation Pressure Belts and Winds
• The jet stream is a narrow zone of high speed air found in the upper troposphere (about 30,000 feet) – Wind speeds here may be over 300 knots! • Large convection currents of air occur on the Earth’s surface due to the unequal heating of the atmosphere
ESRT’s Page 14 Bottom
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Test what you know about air pressure and winds! Page 53 of 63
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