Global Wind Patterns. The circulations of the atmosphere (winds) and oceans (currents) are driven by sunlight hitting the earth’s surface more directly near the equator a LOT of this sunlight energy hits the tropics, between 23.5 0 North and South of the equator. Caused by uneven heating.
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The circulations of the atmosphere (winds) and oceans (currents) are driven by sunlight hitting the earth’s surface more directly near the equatora LOT of this sunlight energy hits the tropics, between 23.50 North and South of the equator.
Caused by uneven heating
What Makes the Wind Blow?
Three real forces (gravity, pressure gradient, and friction) push the air around
Two apparent forces due to rotation (Coriolis and centrifugal)
Large-scale flow is dominated by gravity/pressure and Coriolis … friction and centrifugal important locally
If Earth did not rotate, wind patterns would be simply N to South along the surface
But the earth rotates, so there is a tendency for objects moving over long distance (like air masses) to curve due to “coriolis effect”
Heat Exchange in air masses
Warm, humid air rises, dry clear air sinksCreates 3 huge convection/circulation cells in each hemisphere
Add these prevailing winds to your globe from north to south:
- TROPICS: low pressure air rises near equator - MUCH RAIN
-DESERT ZONE: condensed, high pressure air descends near 30 degrees - clear skies!
- Polar air rises near 60 degrees and descends near 30 degrees
- explains surface westerlies from 30-60
1.Unequal solar heating between the equator and poles. Atmospheric general circulation moves heat toward the north and south poles..
2.In a Hadley cell, warmer air rises and moves poleward. Equator-to-pole Hadley cell is impossible. The Earth rotates!
3. In the Northern Hemisphere, air is pushed to the right as it moves; in the Southern Hemisphere, air is deflected toward the left. The Coriolis effect.
- rotation produces trade winds; surface westerlies in NH; upper tropospheric jet streams.
4. Ferrel cell runs backwards! Transports heat the wrong way, towards the equator!
5. The Ferrel cell is weak, so does not move as much energy as the other cells.
Global Wind and Pressure Patterns
Deserts: belts of persistent high atmospheric pressure centered at about lat. 30º N and S
Polar Front: front lying between cold polar air masses and warm tropical air masses
Intertropical Convergence Zone (ITCZ): Where convergence of air masses along the equatorial trough
Hadley Cell: low-latitude atmospheric circulation cell with rising air over the equatorial trough and sinking air over the subtropical high-pressure belts