Transcript Wind Belts

Aim: What are some of Earth’s wind patterns?
I. Winds and Pressure Belts
A. Convection cell – when air circulates by rising in
one place and sinking at another.
1. Convection cells occur because cooler, more dense
air sinks toward the earth’s surface, pulled by earth’s
gravity, causing the warmer, less dense air to rise.
B. Pressure belts are produced due to convection.
1. Low pressure belts are found at the equator and 60oN
and S latitudes.
a. Air rises and converges. Thus, called zones
of convergence.
2. High Pressure Belts are found at the poles and 30o N and
S latitudes.
a. Air descends and diverges. Known as zones
of divergence.
C. Coriolis Effect – rotation of earth causes winds to
deflect.
1. In the northern hemisphere, winds are deflected
to the right.
2. In the southern hemisphere, winds are deflected
to the left.
GAME
3. Winds are a result of air moving from regions
of divergence (high pressure) to areas of
convergence (low pressure).
D. Trade Winds – winds flowing toward the equator
between 30o and 0o in both hemispheres. (NE and SE
trades)
1. Doldrums – where trade winds of N & S
hemispheres meet at the equator. Very weak winds
in this area.
E. Westerlies – winds located between 30-60o in
North and Southern hemispheres.
F. Jet Streams – occur high in the troposphere and low
in the stratosphere.
1. Due to great difference in air temperature.
Why do great differences in air temperature
cause high speed winds?
2. These winds are found at an altitude of 10-15
km, are about 100 km wide, and are 2-3 km thick.
These winds may reach a speed of 500 km per
hour!!!!
G. Local winds – not part of the global wind belts.
1. Breeze – gentle wind that extends over distance
of less than 100 km.
a. Sea breeze – occurs during the day. when air over
the water blows towards the land due to temperature
and pressure differences.
b. Land breeze - occurs at night. When air over the
land moves towards the water due to temperature
and pressure differences.