lecture note 7

52 views2 pages
19 Jul 2010
School
Course
LECTURE 7:
- Two key factors determine the distribution of ecosystems on Earth more than any other:
(1) precipitation, and (2) temperature
- Tropospheric air masses are circulated by solar energy (~1% of the total average energy
input into Earth creates the global wind movements); this creates the main patterns of
precipitation
- Air circulation occurs via a set of three distinct cells in the two hemispheres: the
Hadley, Ferrell, and Polar cells
- The Hadley cell (active between 0o to 30o N. and S. latitude; here we describe it for the
Northern hemisphere): the sun heats air at the equator, causing it to expand and rise; it
takes with it large quantities of moisture; as air masses rise, they cool adiabatically (the
adiabatic lapse rate: 100C/km for dry air, 60C/km for moist air) and release their
moisture content in the form of precipitation (thisfeeds the tropical rainforests); the
high-altitude air masses move away from the equator to the North, lose energy, and
descend at ~300 N. latitude (they carry almost no moisture at this point; most of the
world’s deserts are located here, in the semi-permanent high-pressure/low-precipitation
zone that results); upon descending, the air masses split to move as surface winds, with
onearm moving North (these are the Westerlies; the jet stream is a part of this) and the
other moving South, back to the equator (as the Northeast trade winds; these are the
winds that brought Columbus to America); the zone where the Hadley cells of the two
hemispheres meet is called the Intertropical Convergence Zone (ITCZ; there is a dead
zone of very little wind at the surface, known as the doldrums, right where the cells meet;
the similarly windstill zones at the 300 latitudes are known as the horse latitudes)
www.notesolution.com
Unlock document

This preview shows half of the first page of the document.
Unlock all 2 pages and 3 million more documents.

Already have an account? Log in

Get OneClass Notes+

Unlimited access to class notes and textbook notes.

YearlyBest Value
75% OFF
$8 USD/m
Monthly
$30 USD/m
You will be charged $96 USD upfront and auto renewed at the end of each cycle. You may cancel anytime under Payment Settings. For more information, see our Terms and Privacy.
Payments are encrypted using 256-bit SSL. Powered by Stripe.