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Meteorology: Wind and the Coriolis Effect (2012)
Transcript of Meteorology: Wind and the Coriolis Effect (2012)
"The winds blow from High to Low"
The higher the gradient (closeness of the isobars), the stronger the winds.
Pressure differences are caused by unequal heating (remember we said weather is caused by unequal heating of Earth?) What makes wind blow? How Do We Measure Wind? 1. Wind vane – Arrow with broad tail, arrow points into the wind. Therefore, winds are named for the direction they come from.
The winds are named from where they came.
2. Anemometer – used by meteorologists to measure wind speed, direction, etc. http://www.smg.gov.mo/dm/equip/ws.jpg Coriolis Effect Generally on the Earth:
Cold air sinks down at the poles,
travels along the surface,
picks up heat,
and collides at the equator where it rises.
But meanwhile, what is the earth doing? Rotating!!! From the perspective of the north pole, Earth is rotating counterclockwise.
From the perspective of the south pole, Earth is rotating clockwise.
Must plan for this when launching planes, rockets, etc. The Coriolis Effect is... The curving of wind and water due to the rotation of the earth.
Curve to the right in the N. Hemisphere.
Curve to the Left in the S. Hemisphere. Summary: 1. In N. Hemisphere – winds blow clockwise out of high pressure areas, and counterclockwise into area of low pressure http://www.windows.ucar.edu/earth/Atmosphere/images/high_pressure_sm.gif 2. The closer to the equator, the less the effect. The Jet Stream The Jet Stream marks the boundary between cold arctic air to the north and warm tropical air to the south.
Found at a high altitude – near the top of the Troposphere. (remember this word?)
Bands of swiftly moving air traveling from west to east.
Supplies energy to storms and directs their paths. Polar front jet stream brings cold air from north.
In summer, it tends to stay north.
In winter, can dip down as far south as Florida. http://www.centennialofflight.gov/essay/Dictionary/Jet_Stream/DI68G1_hi.jpg Global Winds on a Non-Rotating Earth Note: This model is for Spring/Fall only. Earth is tilted, so in summer and winter energy is concentrated north or south of the equator. This causes the pattern of global winds to shift ITCZ (Intertropical Convergence Zone) i.e. "the Doldrums". Remember, sun's radiation is always fairly strong at the equator. Here, surface winds converge – hot, humid, rising air, rainy almost all the time. This is why there is a lot of rain and humidity at the equator.
"Horse Latitudes" ( 25 – 30°) – Sinking air, forming a High pressure area. Therefore, little to no cloud formation and precipitation. This is why many of the Earth's deserts are located here! FYI, the name comes from there being no wind here. People had to row and horses were expendable.
Trade Winds - Between the Doldrums and Horse Latitudes. Winds predictably move a certain direction (generally H to L). Name comes from trade ships using these winds to aid in getting to their destinations quicker.
Polar Highs - Cold air sinks at the poles.
FYI - Prevailing Winds (always moving in generally the same direction). We live among the Prevailing Southwesterlies. Mr. Smolinski Current Jet Stream:
http://squall.sfsu.edu/scripts/nhemjetstream_model.html Jet stream winds are not affected by friction against land surface, so the Coriolis Effect is quite strong, and winds travel parallel to isobars rather than across. http://santasusana.org/pakelly/ES9CP/hadley3.gif Pretty simple... Warm air rises, Cool air sinks. But since Earth is rotating, the air is deflected by the Coriolis Effect! From Equator to North Pole (Northern Hemisphere), deflected to the right.
From Equator to South Pole (Southern Hemisphere), deflected to the left. Global Winds on a Rotating Earth! Notice that direction alternated between 0 and 30, 30 and 60, 60 and 90. H L L H H H L Where are the Highs and Lows? Description of Wind and Pressure Belts Effects of Seasons and Climates Coriolis Review:
http://www.classzone.com/books/earth_science/terc/content/visualizations/es1904/es1904page01.cfm?chapter_no=19 Review of Global Winds Winds are named from where?
The direction they are going.
The direction they came from.
In the US, winds generally blow from:
East to West
West to East
Winds in the Northern Hemisphere deflect to the right or left? How about Southern Hemisphere?
How can we explain that most of the world's tropical rainforests are along the equator and most of the deserts are along 30 degrees N and S? Winds spiral:
INTO a Low Counter-Clockwise.
OUT of a High Clockwise. Land and Sea Breezes Land heats faster than water. http://www.aboutflight.com/wp-content/uploads/2011/09/11-13.png Land cools faster than water (which means the water stays warmer) Seasonal Changes Consider the US:
Cold and Dry in winter, so predominantly... H or L?
Hot and Humid in summer, so predominantly... H or L?
So since Wind always blows High to Low, the local wind direction can change throughout the year. Monsoons In some locations, Highs and Lows can switch drastically with the seasons.
Winds that change directions seasonally are called Monsoons.
This is most dramatic in southern Asia due to size of the continent absorbing and losing heat. http://web.gccaz.edu/~lnewman/gph111/topic_units/Pressure_winds/pressure/monsoon.jpg Why do winds change? We already know that:
Earth is heated (evenly or unevenly?)
Land and Water absorb heat at different rates (Which absorbs and loses heat quicker than the other?)
And Land is not evenly distributed around the globe (which has more land, northern or southern hemisphere?)
We also already know that:
Wind always moves in a certain way
(Low to High or High to Low?)
And finally, we also already know that:
Earth is tilted (how many degrees?)
Therefore Earth has seasons because of Earth’s revolution around the Sun.
Therefore the Sun's radiation is sometimes directed most strongly at the Equator, sometimes at the Tropic of Cancer, and sometimes at the Tropic of Capricorn (when, when, and when?)
T. of Cancer:
T. of Capricorn: Therefore … Winds change from night to day and throughout the year! We can classify winds in two ways:
Local Winds: Winds that affect a local area.
Global Winds: General widespread wind patterns in certain parts of the world. Warm air rises and Cold air sinks in 2 scenarios: As seen from the ground: As seen on the whole Earth: