Post on 27-Dec-2015
Winds Atmospheric Circulation Ch22.3
p561
Wind is horizontal air movement
Three causes of motion
1. Convection2. Pressure
Differences
3. Coriolis Effect
Convection Currents
Warm air rises and cool air sinks because of densityThis is called a
convection current
Winds are caused by the uneven heating of Earth’s surface.
Land heats up and cools off quicker than water
So the large amount of water on Earth moderates our temperatures
2. Pressure Differences
pressure differencesin the atmosphere that are a result of temperature differences
WIND ALWAYS FLOWS FROM HIGH TO LOW PRESSURE
3. Coriolis Effect
The deflection of objects to the right in the northern hemisphere—called the Coriolis Effect Due to rotation of
the earth
effect greatest at poles, decrease to zero at equator
Coriolis Effect
Global Circulation PatternsGlobal winds are
the result of several cell-like circulation patterns brought about by uneven heating of
Earth’s surface and compounded
by effects of the Earth’s rotation.
Doldrums or ITCZ At the equator hot
air rises and forms an area known as the doldrums
At the boundary between the troposphere and stratosphere it spreads out to the N or S
ITCZ—Intercontinental convergence zone
Horse latitudes As it reaches about 30 N and S of the equator it cools and descends
Sinking air causes an area of dry weather
The sinking air also causes an area with weak winds
This caused problems for ships
Trade Winds Winds flowing south
from the horse latitudes is deflected to the west in the northern hemisphere
These aided trading by ship
Jet Stream Jet streams are fast flowing, relatively
narrow air currents found in the atmosphere at around 11 kilometers (36,000 ft) above the surface of the Earth, just under the tropopause.
They form at the boundaries of adjacent air masses with significant differences in temperature, such as of the polar region and the warmer air to the south.
Current jet stream data
Highs and Lows? Winds circle
Clockwise and out around a high
Highs generally mean cold dry air that is sinking
High pressure usually = fair weather
Low Pressure Systems Winds circle
counterclockwise
and into a low Warmer air rises and
cools and forms clouds and precipitation
Low pressure usually = rainy weather
Explore Draw an H in the middle of your paper Draw a
1 inch circle lightly around the H. Place all five fingers inside the circle using
your left-hand if right handed and your right if left-handed.
Standing up if necessary, turn your hand slowly clockwise and gradually spread your fingers and thumb our as your hand turns. Don’t move the map. You hand will end up flat on the paper.
Bring your fingers back inside the circle. Number the starting position of each finger and
thumb with your thumb as number 1, index finger 2, and so on.
Slowly rotate your hand clockwise and gradually spread out your fingers and thumb, stopping after about one inch of motion. Number the position of each finger again.
Continue spreading and numbering every inch or so, until your hand is completely flat on the paper.
Connect each number in a smooth arch, Place arrows at the end of each arch. The result should be a spiral pattern, typical of a high pressure system.
Explore Low Draw an L in the middle of your paper Draw a
1 inch circle lightly around the L. Place your non-writing hand, palm down on
the circle. Rotate your hand counterclockwise, bring your thumb and fingers up into the circle. Practice this twisting motion without moving the paper.
Place your palm down again, and number the position of each finger and thumb, with the thumb as one.
Slowly rotate counterclockwise and gradually bring in your fingers and thumb, numbering the position of the position of each finger after about one inch of motion
Connect each number in a smooth arch, ending with an arrow pointed toward the L. This pattern is typical of a low pressure system.
Wind always blows from high to low
Local Wind PatternsMonsoonsLand breeze/Sea breezeChinook
MonsoonIn winter, air flow is
from cooler (H pressure) to warmer (L pressure) ocean
Air from the land is dry Dry season
In summer, air flow is reversed
Air flows from the cooler ocean to the hotter (L pressure) land
Wet season
Sea Breeze
During the day land heats faster than the water. The hot less dense air rises and cooler air from the sea rushes in to take its place.
Land breeze
Since the air over land cools more rapidly than the air over water, a temperature difference is established, with cooler air present over land and relatively warmer air located over water.
Chinook A wind on the
eastern side of the Rockies formed when air descends and is compressed and warms
Effects: Rapid. Large
Temperature Changes Can Occur
Snow may melt or evaporate through sublimation
Loss of moisture due to significant drops in humidity
Beaufort scale Used to estimate
wind speeds Originally used by
sailors
Beaufort Scale on Water
Beaufort Scale on Land
Wind Energy
Wind and Pressure Relationship Lab
Remember Topographic Maps?
Contours are imaginary lines that join points of equal elevation on the surface of the land
Now we will use these with equal temperature and pressure
Same Concept—Different Use
Isotherm=equal temperature
Isobar=equal barometric pressure
contour interval (CI)1. The contour intervals
vary
2. Isobars often have an interval of 4
3. Read the directions or look at examples to see the contour level
Tips for understanding contour lines. There are a few rules that topographic
contours must obey, however, and once you understand these rules the map becomes an extremely useful and easy to use tool.
As a result of this every contour line must eventually close on itself to form an irregular circle
Contour lines on the edge of a map do not appear to close on themselves because they run into the edge of the map, but if you got the adjacent map you would find that, eventually, the contour will close on itself.
1) Every point on a contour line represents the exact same temperature or pressure
2) Contour lines can never cross one another.
Each line represents a separate temperature or pressure and you can’t have two different temps or pressures at the same point.
3)Points shown are reporting stations
There may be areas that do not report or have no station
4) The closer contour lines are to one another, the higher the wind speed.
Where is the wind speed high? Where is it low?
5) Inside a series of closed contours (the contours
make a circle) is a High or Low pressure