WIND Flashcards
What is wind?
The movement of air in the atmosphere horizontally, (the most common). Caused by horizontal pressure differences.
Closely spaced isobars mean
Steep pressure gradient and strong wind
Widely spaced isobars mean
Shallow pressure gradient, and relatively light wind
Pressure gradient
This is the rate of change of pressure over a distance indicated by the actual spacing of the isobars
Advection =
Horizontal movement of air
Convection
Rising heated air
Illustrate the Coriolis force
Two Kids on a merry-go-round. Kid, A standing in the middle of the roundabout, throwing a ball to person B who is standing at the edge of the roundabout, if A throws the ball, straight at B by the time the ball has reached the edge of the roundabout be has gone further around and will not be able to receive the ball.
Isobars
These are imaginary lines which join points of equal MSL pressure
Standard ISA, sea level pressure is what in hecto pascals
1013 hPa
Pressure gradient
This is the rate of change of pressure over a distance indicated by spacing of isobars
If the isobars are close together, what is the result?
MUST KNOW
The pressure gradient is steep, producing strong winds
Subsidence
The downward movement of air
Cold air sinking
Resultant wind
Geostrophic wind is the resultant wind at Heights approximately 2000 and 3000 feet above the ground
Buys ballot
His law states that if you stand with your back to the wind in the northern hemisphere, the low pressure is always on the left, and the high pressure is always on the right.
What direction is the Coriolis force?
The opposite direction to the pressure gradient force
Tri-cellular model
2 dimensional model that give us a general understanding of how our atmosphere functions.
It is a global scale model that is based entirely upon the fact that there are recognisable insolation differences between the Equator and the Poles
What are the cells between the equator and the north pole?
Hadly cell
Farrell cell
Polar cell
Veering wind
Wind direction changing clockwise
Backing wind
Wind direction changing counter clockwise
General rule of thumb regarding veer, wind, and backing wind:
Winds veer and increase during a climb out. Winds back and decrease during an approach.
A calm oceans surface can you change winds by how many degrees?
10°
A city or extremely rough terrain can change a winds speed/direction by as much as…?
40°
Wind Gust
A brief, rapid change of wind direction, and or speed.
Wind squall
A prolonged change of wind direction, and or speed. It would last for a minute or more.
A seabreeze:
Rotates clockwise from land to over the sea
Land breeze:
Rotates counterclockwise from land over the Sea
Increased performance, shear
An increase in headwind, or decrease in tailwind
Decreased performance, shear:
Is a decrease in headwind or increase in tailwind.
Rossby waves
Upper winds organized into wave patterns
Technically, they are a result of the temperature variations and the rotation of the Earth
Jet streams:
Very strong high altitude winds of 60 kt or more. Thousands of miles long and hundreds of miles wide.
Rossby waves and jet streams:
These help in the rapid transfer of energy around the globe and can dispersed debris from eruption’s around the world within a week
Three main jet streams:
Polar front jetstream PFJS
Subtropical jetstream STJS
Easternly equatorial jetstream a EEJS
Polar front jet stream:
Found between 40° and 60° in both hemispheres. Division between the polar and ferrel cells.
When it moves south, it brings cold air which gives us dry in stable condition with high pressure. When the stream is warmed, it returns northward.
Subtropical jetstream STJS
This is found 25° to 30° of latitude and is the boundary between the feral and the Hadley cells.
Easterly equatorial jet stream, EEJS
This stream is more seasonal, and it is associated with the summer monsoons in India. It is a gentle jet stream.
