part 3. distribution and movement of air chapter 8 atmospheric circulation and pressure...
TRANSCRIPT
![Page 1: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/1.jpg)
Part 3. Distribution and Movement of Air
Chapter 8
Atmospheric Circulation and Pressure Distributions
![Page 2: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/2.jpg)
Planetary WindsWell-defined pressure patterns exist across the Earth that induce the global wind patterns on the planet
![Page 3: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/3.jpg)
Idealized Single-Cell Convection Model for a Planet
![Page 4: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/4.jpg)
The ITCZ is a band of clouds across the tropics
![Page 5: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/5.jpg)
The Three-Cell Model
Intertropical convergence zone (ITCZ) -- surface low pressure with clouds and rain
Subtropical high -- Air subsides (dry climate)
Hadley cell -- tropical convection cell
Ferrel cell -- southwesterly winds at surface
Polar cell -- northeasterly winds at surface
![Page 6: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/6.jpg)
The three-celled model vs. reality:
• Hadley cells are close approximations of real world equatorial winds
• Ferrel and polar cells do not approximate the real world winds very well at all
• Model is unrepresentative of westerly flow aloft
• Continents and topographic irregularities cause significant variations in real world wind patterns compared to the model
![Page 7: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/7.jpg)
Semi-Permanent Pressure Cells are large areas of higher or lower atmospheric pressure than the surface average
They may be thermally induced (rising warm air or subsiding cold air) or they may be caused dynamically by converging or diverging wind patterns)
They fluctuate seasonally
Northern hemisphere semi-permanent cellsThe Aleutian, Icelandic, and Tibetan lows
Siberian, Hawaiian, and Bermuda-Azores highs
ITCZ (low)
![Page 8: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/8.jpg)
Average atmospheric air pressure and wind patterns in January
![Page 9: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/9.jpg)
Average atmospheric air pressure and wind patterns in July
![Page 10: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/10.jpg)
The Sahelreflects seasonal migrationof the ITCZ
The Sahel is rainy during northern hemisphere summer and dry during northern hemisphere winter as the ITCZ shifts north and south through the year. It is the reason for annual flooding of the Nile River.
![Page 11: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/11.jpg)
Shifts in the ITCZ affect the Sahel
![Page 12: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/12.jpg)
Mid-latitude winds in the middle and upper troposphere are controlled b the pressure gradient force and the Coriolis force, giving the westerly winds
Stronger pressure gradients in winter give stronger westerlies
![Page 13: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/13.jpg)
Westerly winds in the upper atmosphere• Air motions directed towards poles • Redirected by Coriolis deflection
– Westerly winds aloft result
The polar front and jet streams• Fast stream of air in upper troposphere
– Above polar front– Stronger in winter
![Page 14: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/14.jpg)
Polar jet profile
The fastest middle and upper troposphere mid-latitude winds (the jet stream) are at polar front. There is a sharp temperature contrast and horizontal pgf to the south and north of the polar front.
300 mb
500 mb
800 mb
Strongest pgf here
![Page 15: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/15.jpg)
The subtropical jet transports low latitude moisture and energy
Subtropical front and jet
![Page 16: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/16.jpg)
Ridges and trough profileRidge Ridge
Trough
![Page 17: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/17.jpg)
A trough over the mid-continent in (b)
![Page 18: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/18.jpg)
Rossby waves are the wave-like pattern of ridges and troughs in the upper troposphere winds. Ridges and troughs (Rossby waves) will migrate either east or west with time
![Page 19: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/19.jpg)
Sequence of Rossby wave migration -- the dashed line shows the migration and evolution of a trough with time across the country
![Page 20: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/20.jpg)
Ocean currents are driven by wind stresses and are deflected by the Coriolis force. Thus, the water moves at about a 45° angle to the winds. The diection of movement of the ocean changes with depth following a pattern called the Ekman
spiral.
• Western basins usually experience warm ocean currents
• Eastern basins usually experience cold ocean currents
![Page 21: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/21.jpg)
![Page 22: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/22.jpg)
Upwelling in along-shore winds• Cold waters rise due to Ekman transport
![Page 23: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/23.jpg)
Global Ocean Circulation
![Page 24: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/24.jpg)
Infrared Satellite Image of the Gulf Stream
![Page 25: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/25.jpg)
Major Wind Systems of the EarthMonsoons• Thermal induced seasonal wind patterns
associated with shifts of the ITCZ
• Monsoons are characterized by dry offshore winter flow and wet onshore summer flow
• The monsoon in East Asia experiences orographic enhancement
![Page 26: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/26.jpg)
Winter monsoon
![Page 27: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/27.jpg)
Summermonsoon
![Page 28: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/28.jpg)
Topography enhances monsoonal effects
![Page 29: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/29.jpg)
Foehn winds are strong, downslope winds that adiabiatically compress, raising the air temperature. Foehn winds are associated with hot, dry, clear weather
Chinook winds are foehn winds along the east slope of the Rockies (“snow eaters”)
Santa Ana winds are foehn winds that blow from the deserts and over the mountains into the valleys of southern and central California
Katabatic winds are cold, dense winds that flow down mountain slope. They warm as they descend, but they are still colder than the surrounding air.
• Boras and mistral winds are forms of katabatic winds in Europe
![Page 30: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/30.jpg)
Southern California Santa Ana induced fires
![Page 31: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/31.jpg)
Sea and land breezes form due to temperature differences over land and sea. Sea breezes form during the day, and land breezes form at night.
Valley and mountain breezes form due to heating and cooling on mountain sides. Valley breezes form during the day, and mountain breezes form at night (similar to katabatic winds)
![Page 32: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/32.jpg)
Sea breezedevelopment
![Page 33: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/33.jpg)
Sea breeze-initiated clouds over Hawaii
![Page 34: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/34.jpg)
Valley and mountain breeze development
![Page 35: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/35.jpg)
Air-Sea Interactions in the Equatorial PacificEl Niño, La Niña, and the Walker circulation• El Niño events
– Unusually warm water in the eastern equatorial Pacific Ocean
– Linked to global weather anomalies – 2 to 5 year recurrence
• La Niña events -- wind and temperature patterns reversed of El Niño patterns
• Walker circulation – Vertical and horizontal tropospheric flow in
the equatorial Pacific that controls areas of heavy rainfall
![Page 36: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/36.jpg)
The “Normal” Walker Circulation (no El Niño conditions)
![Page 37: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/37.jpg)
ENSO (El Niño/Southern Oscillation) events -- oscillations between El Niño and La Niña conditions• ENSO results in global teleconnection
patterns (weather effects far from the equatorial Pacific)
![Page 38: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/38.jpg)
El Niño SST Anomalies
![Page 39: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/39.jpg)
![Page 40: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/40.jpg)
La Niña SST Anomalies
![Page 41: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/41.jpg)
The Southern Oscillation Index
![Page 42: Part 3. Distribution and Movement of Air Chapter 8 Atmospheric Circulation and Pressure Distributions](https://reader035.vdocuments.us/reader035/viewer/2022062318/551696dc550346f6208b48e9/html5/thumbnails/42.jpg)
The PDO Index
Warmer waters in western tropical Pacific
Cooler waters in western tropical Pacific