1.
Global Winds
(pg. 181)
·
General Circulation of
the Atmosphere – the global
scale wind pattern (Table 8.1, Fig. 7.15, 7.16).
·
Start with a
simple (but unrealistic)
model – the single cell model (Fig. 7.15 a).
·
Strongest
solar heating occurs at the
equator – this causes the air to rise and it then moves towards the
poles. As it does so it cools (radiates
heat out to
space) and then sinks to the surface and returns to the equator thus
completing
the cycle (cell).
·
Then get
more complex (but more realistic)
with the three cell model (Fig. 7.16 a).
·
Due to the
rotation of the earth, the
single cell breaks down into three cells (Hadley, Ferrel, Polar).
·
The winds
at the surface would normally
be purely meridional (N-S direction) but due to the Coriolis effect
they veer
to the right in the NH (left in the SH).
·
This gives
rise to: the NE trade winds,
the Westerlies, the Polar easterlies.
·
Where the
winds are mainly vertical
(little horizontal motion to move ships, for example) one finds the
Doldrums (ITCZ)
and Horse latitudes.
·
At 30
degrees latitude (Horse latitudes)
we get the subtropical high pressure system; and at 60 degrees we get
the
subpolar low pressure – both semi-permanent features.
·
Appearance of General
Circulation model on surface WX
maps (Fig. 7.17, 7.18).
·
Subtropical
High easily seen in S.
hemisphere; obscured in N. hemisphere by continents.
·
Remnants of
Polar low seen N. hemisphere
in Aleutian low and Icelandic low. In S.
hemisphere there is a continuous trough of low pressure at 60 degrees
S.
(closer to the theoretical ideal).
·
These
patterns follow the Sun (move north
in summer).
·
Siberian
High and thermal Lows are not
permanent features.
·
Pacific High
– elevated inversion along
west coast traps air pollution; minimizes convection and cuts summer
rainfall
(Fig. 7.19, 7.20).
·
Appearance of General
Circulation model on upper
level WX maps (Fig. 7.21, 7.22, 7.23).
·
Two jet
streams in tropopause (fast moving
air, easily 100 kt). They meander
around, sometimes link up, transport heat, volcanic dust around the
planet.
·
Subtropical
jet (30 degrees, 15km):
pineapple express.
·
Polar
(front) jet (60 degrees, 10km): heads
south in winter and directs our winter
WX.
2.
Global Ocean
Currents (pg. 189)
·
Global wind patterns
drive ocean surface waters and
set up global ocean surface currents (Fig. 7.24, Table 7.2).
·
Focus on
those most important to us:
·
1 Gulf
Stream; 2 North Atlantic Drift; 3 Labrador Current; 9 South Equatorial
Current; 16 California Current; 17 Peru (Humbolt) Current
·
Upwelling
·
El
Nino/Southern Oscillation (ENSO)