ATMOSPHERIC FLOW Flashcards
What are the four horizontal components of airflow?
Translation
Divergence
Rotation
Deformation
Why is atmospheric flow important in meteorology?
Leads to the development of Highs & Lows. And the subsequent wx we therefore experience.
Terms used to describe vertical atmospheric motion?
Ascent (up)
Descent/subsidence (down)
Define translation
A body of air that is moved without rotating it or changing its shape or volume. Simple direct movement from one place to another. Nil upward motion
Define Divergence
Expansion horizontally.
I.e. the horizontal outflow exceeds the horizontal inflow
Define Convergence
(Negative divergence)
I.e. the horizontal inflow exceeds the horizontal outflow.
What causes divergence
Diffluence or acceleration dominating the flow
Describe why divergence/convergence causes ascent/descent?
Air is incompressible, therefore net inflow must equal net outflow & vice versa.
Therefore, where divergence/ convergence is occurring, there is a resultant vertical flows
What does convergence at the surface result in in terms of vertical motion?
Resulting surface pressure system?
Ascent & divergence at altitude.
Resulting low pressure system at surface.
What does divergence at the surface result in in terms of vertical motion?
Resulting surface pressure system?
Subsidence and convergence at altitude.
Resulting in high pressure system at surface.
Diffluence & confluence vs. divergence & convergence
Diffluence: going apart
Confluence: coming together.
Can enhance divergent & convergent flows. However you can have a diffluent/confluent flow without divergence/convergence occurring.
When does rotation/vorticity of an airflow exist?
Where the flow is curved or when there is shear.
Define Absolute Voriticty
The sum of relative vorticity (made up of shear & curvature vorticity) and the earths vorticity.
What is Earths vorticity created by?
Arises from the shear produced by the earths rotation. Increases with latitude.
Why is absolute vorticity important when it comes to flow?
Changes in AV will lead to upper level divergence & convergence & therefore upward & downward motion
Earths vorticity vs. relative vorticity?
What does this mean for SH?
EV always cyclonic (clockwise) in SH.
EV swamps RV, therefore, absolute vorticity will always by cyclonic in SH.
What is relative vorticity dependent on?
Shape & position of upper air pattern
What ultimately leads to changes in absolute vorticity?
Changes in Relative vorticity.
RoT: changes in absolute vorticity & resulting conv/div?
Increase in AV = CONV
Decrease in AV = DIV
Define deformation
Occurs when an airmass changes shape. Confluence and diffluence are both present.
What is deformation important for
In the production of fronts & shaping of cloud systems.
Where confluence brings isotherms together. (Temp gradient is increased & front is therefore produced).
