Download Global atmospheric circulation

yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Document related concepts

Automated airport weather station wikipedia, lookup

Pressure wikipedia, lookup

Ionospheric dynamo region wikipedia, lookup

Wind wikipedia, lookup

Atmosphere of Earth wikipedia, lookup

El Niño–Southern Oscillation wikipedia, lookup

Wind shear wikipedia, lookup

Tectonic–climatic interaction wikipedia, lookup

Barometer wikipedia, lookup

Anemometer wikipedia, lookup

Storm wikipedia, lookup

Severe weather wikipedia, lookup

Satellite temperature measurements wikipedia, lookup

Weather wikipedia, lookup

Cyclone wikipedia, lookup

Cold-air damming wikipedia, lookup

Jet stream wikipedia, lookup

Atmospheric convection wikipedia, lookup

Weather lore wikipedia, lookup

Pangean megamonsoon wikipedia, lookup

Surface weather analysis wikipedia, lookup

Atmospheric circulation wikipedia, lookup

How Does Air Move Around the Globe?
Review of last lecture
• Thickness of the atmosphere: less than 2% of Earth’s
• Definition of temperature. 3 units.
• Four layers of the atmosphere, what separate them?
• Definition of pressure and its unit.
• Definition of pressure gradient. Pressure gradient sets
the air in motion.
• Equation of state (Relationship between P, ρ, and T)
• Vertical Pressure Distribution. How does pressure
change with height? What is the hydrostatic
Review of last lecture (cont.)
• Know 3 Forces that affect wind speed /direction
• Especially work on Coriolis force, as this is the
hardest to understand. Which direction is air
deflected to by Coriolis force?
• What is the geostrophic balance? At which level is it
valid? Difference between upper level and surface
• Does cyclones correspond to high or low surface
pressure? Is the air moving clockwise or counterclockwise around them? How about anticyclones?
• What are the troughs and ridges?
The most common atmospheric
circulation structure
or No
Imbalance of heating  Imbalance of temperature
 Imbalance of pressure  Wind
• Well-defined heating, temperature and pressure patterns exist
across the globe
• These define the general circulation of the planet
• In describing wind motions:
– Zonal winds (east-west): flow parallel to lines of latitude
• Flowing eastward: Westerly wind
• Flowing westward: Easterly wind
– Meridional winds (north-south): flow parallel to lines of
• Flowing northward: Southerly wind
• Flowing southward: Northerly wind
Annual mean precipitation (heating)
Extratropical stormtrack
Tropical rainfall
Extratropical stormtrack
Primary Highs and Lows
Equatorial low
Subtropical high
Subpolar low
Polar high
Three-cell model
Zonal mean circulation
Each hemisphere is
divided into 3 distinct
Hadley Cell
Ferrel Cell
Polar Cell
Vertical structure and mechanisms
Polar Cell (thermal):
Driven by heating at
50 degree latitude
and cooling at the
Ferrel Cell (dynamical):
Dynamical response to
Hadley and polar cells
Hadley Cell (thermal):
Heating in tropics  forms
surface low and upper
level high  air converges
equatorward at surface,
rises, and diverges
poleward aloft 
descends in the subtropics
Zonal mean structure of temperature
Two characteristics:
Horizontally uniform
in the tropics
Steep gradient in
the extratropics
Vertical structure of zonal wind
Two characteristics:
Westerly winds in the
extratropical troposphere
(caused by the Coriolis
force). Explains why storms
move eastward, flight times
Jet streams: local
maximum of winds
(caused by sharp
pressure gradient across
the boundary between
warm tropical air and
cold polar air)
The Jet Streams
• Caused by steep temperature
gradients between cold and
warm air masses
• Polar front - marks area of
contact, steep pressure
gradient  polar jet stream
• Low latitudes  subtropical
jet stream
• Stronger in winter, affect daily
weather patterns
Semipermanent Pressure Cells: NH winter
South Pacific
South Atlantic
South Indian
Low pressure centers: weather and precipitation
High pressure centers: warm, drought and desert
Semipermanent Pressure Cells: NH summer
South Pacific
South Atlantic
South Indian
General circulation of the oceans
• Ocean surface currents – horizontal water motions
• Transfer energy and influence overlying atmosphere
• Surface currents result from frictional drag caused by
wind - Ekman Spiral
• Water moves at a 45o angle (right)
in N.H. to prevailing wind direction
• Due to influence of Coriolis effect
• Greater angle at depth
Global surface currents
• Surface currents mainly driven by surface winds
• North/ South Equatorial Currents pile water westward, create the Equatorial
• western ocean basins –warm poleward moving currents (example: Gulf Stream)
• eastern basins –cold currents, directed equatorward
• Three precipitation (heating) belts. Primary high and
• Three-cell model. Mechanism for each cell
• Two characteristics of zonal mean temperature structure
• Two characteristics of zonal mean wind structure. Why
does westerly winds prevail in the extratropical
troposphere? What cause the jet streams?
• Semipermanent pressure cells. Low pressure is
associated with clouds and precipitation. High pressure
is associated with warm surface temperature, drought,
and desert.
• What drives the ocean surface currents? In the case of
Ekman spiral, what is the direction of surface current
relative to surface wind?
Works cited