1. Global Average Barometric Pressure: January
Figure 4.11

2. Global Average Barometric Pressure: July
Figure 4.11

3. Primary High Pressure & Low Pressure Areas
Equatorial low pressure zone: (aka Intertropical Convergence Zone) band of cloudiness & abundant precipitation. Thermally induced
Polar high pressure cells: subsiding air, stronger in winter. When strong, are associated with minimal precipitation. Thermally induced
Subtropical high pressure cells: areas of subsiding air, dry climates when on west side of continents. Dynamically induced
Subpolar low pressure cells: mean locations are Iceland & Aleutian Islands. Cause winter precip. (mid-latitude cyclones) Dynamically induced
All of above pressure cells move north and south in response to seasonal changes in the subsolar point. Same w/ wind systems.

4. OPTIONAL Comparing July & January Isobar Maps, Northern Hemisphere
Remember that maps are of average pressures, so they just show general tendencies
Aleutian Low not evident in July (but it is a weak feature)
High pressure cells are more developed (have more isobars) over oceans in July
High pressure cells are located farther north in July (both location and strength driven by land-sea temperature difference, with land warming in summer)
Note presence of continental high pressure over N Asia and North America in January (thermal highs)
Compare january and july for northern hemisphere:
1. Remember that maps are of average pressures, so they just show general tendencies
2. Aleutian Low not evident in July (but note that it is a weak feature)
High pressure cells are more developed (have more isobars) over oceans in July
High pressure cells are located farther north in July (both location and strength driven by land-sea temperature difference, with land warming in summer +

5. Other pressure cell terms
Doldrums
Horse Latitudes

6. Primary Wind Systems
Trade Winds: most constant of all wind systems. Zone also source region for tropical storms and hurricanes.
Westerlies: intensity positively related to Equator-Polar temperature differences. What season are they strongest? Which hemisphere the most persistent?
Polar Easterlies: velocity related to strength of polar high; stronger in winter
Polar Front: (not a wind) boundary where polar easterlies and the westerlies converge, bad weather zone
Actual global wind circulation is modified by the effects of continents and their different levels of heating and cooling as compared with the oceans

7. Sail Around the World Alone race, in the screaming sixties

9. General Atmospheric Circulation: This is similar to your model to know!
Figure 4.13

10. Upper Atmospheric Circulation
Jet Stream: the core of upper-level westerly geostrophic winds, generally of high velocity.
Rossby Waves are found in the upper-air westerly circulation of middle and high latitudes. See “Jet Streams” slide below.

11. Cross Section of General Atmospheric Circulation
Figure 4.13

12. Jet Streams
Figure 4.17

13. Local Winds
defined

14. Monsoonal Wind Systems
Seasonal wind changes that happen at a regional/continental scale due to seasonal reversals of onshore-offshore temperature differences.
Summer: onshore circulations, rain!
Winter: offshore circulations, dry
Where? S & SE Asia, Eq. Africa, a bit of S. America