Wind Flashcards
How is Pressure Gradient Wind calculated
PGF=dp÷(dn x p)
Where: dp=pressure diff between 2 points
dn=horizontal distance between 2 points
p=air density
What is Coriolis/Geostrophic Force
Deflection of air (to the right in NH and to the left in SH) of air moving towards the poles
How do you calculate the magnitude of CF
CF=2ΩPVsinθ
Where:Ω=angular rotation of earth
P=air density
V=wind speed
θ=latitude
What is Geostrophic Wind
When PGF and CF balance each other out, the resulting wind, blowing parallel to straight isobars, is Geostrophic
What is Centripetal Acceleration
CA creates a force directed at right angles to the flow of wind and inwards towards the centre of rotation, producing a circular pattern of flow around centres of HP and LP
For CF, CA and PGF to be in equilibrium, must the CF be greater than or less than the PGF
Greater than
What is Buys Ballot’s Law
Observer who stands with his back to the wind in the SH, the LP would be to his right
1-What is the difference between Veering and Backing
2-does wind veer/back with an increase in alt, and does the wind speed increase/decrease (SH)
1-Veer:wind changes in clockwise direction
Back:wind changes in anticlockwise direction
2-backs and increases due to surface friction
1-What is a sea breeze
2-What is a land breeze
1-Wind blowing from sea to land
2-Wind blowing from land to sea
What causes valley (anabatic) wind
Which side of the mountain is it most likely to occur (N, S, E, W)
Heating of mountain slope during the day
Westward side
What causes Mountain(katabatic) wind
What is likely to happen at the bottom of the valley
At night when air cools down, air becomes more dense and slides down slope of mountain
Fog/mist is likely to build due to collection of cold air
What is Föhn wind
Warm, dry air blowing on leeward(downward) side of mountain
What is a Berg wind
What season does it usually occur in
Hot, dry wind that blows from interior of SA to coast, usually blustery
Usually during winter
What are Mountain Waves
Air flowing accross mountain range, once over top it pours down the other side with considerable force, creating Eddie’s and turbulence
What causes Cap Clouds
Orographic uplift, causing cloud to form on top of ridge
What can be expected near Lenticular Clouds
Mountain Waves
How are Rotor clouds formed
Formed in Rolling Eddie’s
What happens to indicated Altitude with an increase in wind speed
Shows a increase in alt, due to a decrease in pressure
What are 4 common sources for Wind Shear
1-Thunderstorms
2-Fronts
3-Temp Inversions
4-Mechanical Turbulence
1-Where are Dust Devils most likely to occur
2-What type of pressure system are they
3-How are they formed
1-hot,dry plains
2-LP
3-with a Steep Lapse Rate, caused by cool air over a hot surface
What is the Subtropical HP zone produced by
Vertically descending air currents from the Hadley Cell
1-What direction do trade winds blow in the NH
2-What are they called
3-What direction do trade winds blow in the SH
4-What are they called
1-From NE to SW
2-NE Trades
3-From SE to NW
4-SE Trades
What is the Sirocco and where does it occur
Hot dry SE to SW wind, originating as hot air over North Africa, blowing N into Southern Mediterranean basin
What is the Kamsin and where does it occur
Hot, dry and dusty S/SE wind occurring in North Africa around the East Mediterranean
What is the Mistral and where does it occur
Valley wind blowing from S of France to French Mediterranean coast
Northerly cold during winter and early spring
What is the Bora and where does it occur
NE wind and of gale force, strongest and most frequent during winter
Blows down North Adriatic with HP over central Europe and LP over Adriatic Sea
What is the Simoon and where does it occur
Hot, dry, dusty wind that moves accross African deserts
What is the Shamal and where does it occur
N-NW wind blowing over Iraq and Persian Gulf States
What is the Haboob and where does it occur
Strong sand/dust storm occurring along Southern edges of Sahara
Dust storm followed by torrential rain
Wind direction N in winter, E-S in summer
What is the Harmattan and where does it occur
Dry, dusty West African trade wind, dependant on pos of ITCZ
Blows from Sahara into Gulf of Guinea
What is a Jet Stream
Ribbons of very strong winds which move the weather systems around the globe, transporting high and lows, mark boundaries between air masses, usually sit at tropopause
How are Jet Streams caused
Caused by temp difference between tropical and polar air masses
1-Which direction does the Polar Front Jet move
2-Where is it the strongest
3-Is the cyclonic side cold/warm, and does it have stronger/weaker wind shear than the anti-cyclonic side
4-where is it formed
5-does it move N/S during summer
1-W to E - Westerly
2-between Troughs and Ridges
3-cold, has stronger wind shear
4-formed on boundary between cold polar air and warm sub tropical air
5-moves N
In the NH with the PFJ:
1-is there a temp change when flying through the Polar Front Jet Core Height
2-above the zero layer, what happens to the temp gradient, the pressure gradient and the wind speed
3-when flying below the jet core height, what happens to the temp in a N/S direction
4-when flying in a S to N direction, with a Westerly crosswind from the left, and a decrease in temp at alt, must the A/C fly above/below the jet stream and why
5-when flying from N to S with a crosswind from the right and an increase in temp with alt, must the A/C fly above/below the jet stream and why
1-no.
2-temp gradient:reverses, pressure gradient:decreases, wind speed:decreases
3-there is an increase in temp, colder air to the left(N) and warmer air to the right(S)
4-Below the Jet Stream, because the wind speed will increase
5-below the Jet Stream, wind will increase with alt
1-how does the Sub-Tropical Jet form
2-in the NH does the Geostrophic force deflect left/right when moving W to E
1-Forms over sub-tropical anticyclones when air from the Hadley and Ferrel cells meet
2-right
1-Which direction does the Equatorial Jet Stream move
2-which side is there more turbulence
3-is it found in the NH or SH
1-E to W
2-on cyclonal(S) side
3-NH
1-how is thermal wind caused
2-how does the CF affect the flow of air in the NH and SH
3-which direction does the resultant air flow in regards to isotherms(areas of equal temp)
1-caused by pressure gradient trying to move air from HP, H temp to LP, LT at any alt
2-deflected right in NH and left in SH
3-flows parallel to isotherms
1-what is Clear Air Turbulence
2-how is it caused
3-do the mainly occur on cold/warm sides of jet streams in the NH
1-turbulence not associated with clouds, not able to be detected visually
2-caused by vertical and horizontal wind shears together with strong horizontal temp fluctuations
3-cold
