Vorticity

Question 1

Vertical positive vorticity

Answer 1

• contributes to upper-level divergence in the PVA region and thus rising air while horizontal vorticity is important to severe weather

Question 2

Three elements that produce vorticity

Answer 2

• shear
• curvature
• Coriolis force

Question 3

Shear

Answer 3

• change in wind speed over some horizontal distance

Question 4

Curvature

Answer 4

• a change in wind direction over some horizontal distance, this change will result in either a counter- clockwise or clockwise curvature

Question 5

Coriolis force

Answer 5

• it is the spinning motion created by earths rotation

Question 6

Absolute vorticity

Answer 6

• absolute vorticity = shear and curvature + Coriolis force
• the magnitude and sign of each of these 3 terms determines the amount of absolute vorticity

Question 7

Positive increasing vorticity

Answer 7

• wind speed increases when moving away from centre point of trough (positive shear vorticity)
• a counter clockwise curvature in the wind flow occurs in troughs and shortwaves = positive curvature vorticity.
• a south or north movement or air = Coriolis increases ( becomes more positive) when moving from the equator towards the poles (increasing positive earth vorticity)
• positive earth vorticity increasing over time

Question 8

Negative decreasing vorticity

Answer 8

• wind speed decreases when moving away from the centre point of the trough (negative shear vorticity)
• a clockwise curvature in the wind flow occurs in ridges = negative curvature vorticity
• a north to south movement of air = Coriolis decreases (becomes less positive) when moving from the pole to the equator (decreasing positive earth vorticity)
• positive earth decreasing over time

Question 9

Vorticity

Answer 9

• A clockwise or counter clockwise spin in the troposphere
• caused by troughs and ridges and other embedded waves or height centres (speed + directional wind changes in relation to the vertical axis)
• a wind flow through vorticity gradient will produce regions of positive vorticity advection (PVA) and negative vorticity advection (NVA)
• PVA contributes to rising air.
• a clockwise spin produces positive vorticity while counter clockwise spin produces negative vorticity (only in SH)

Question 10

Horizontal vorticity

Answer 10

• vorticity caused by a change in wind direction or wind speed with height.
• the spin in relation to horizontal axis
• horizontal vorticity is most important in the PBL (low-levels of the atmos)
• large values of horizontal vorticity lead to large values of helicity which increases the likelihood of tornados in association with supercell thunderstorms

Question 11

Stream wise vorticity and helicity

Answer 11

• the amount of horizontal vorticity that is parallel to storm inflow
• the vorticity of the low level wind moving towards thunderstorms
• helicity = the amount if streamwise velocity that is available to be ingested by a thunderstorm

Question 12

Why is the relationship between change in vorticity and divergence important?

Answer 12

Because in the moving air, parcels are deformed continuously underground (horizontal divergence or convergence)

Question 13

What is vorticity and its changes used to calculate?

Answer 13

Divergence through continuity, the vertical motions which are most important to weather