Midterm II (Q-Vectors to PV Thinking) Flashcards
What are the advantages to the Q-Vector form of the Omega equation? (List two.)
- Single forcing term
2. Can be evaluated on a single level.
What are the disadvantages of the Q-Vector form of the Omega equation? (List three.)
- Additional simplifying assumption (f-plane)
- Without explicitly plotting q-vectors, it is nearly impossible to diagnose on traditional synoptic maps
- Not physically intuitive for beginning students
For sinusoidal patterns, what can the 3D Laplacian be approximated as?
A minus sign
What vertical motion is associated with convergence of Q-Vectors?
Rising motion
What vertical motion is associated with divergence of Q-Vectors?
Sinking motion
How many levels do you need to diagnose Q-Vectors on to assume the vertical motion?
One. The level we are interested in.
WTH is the Q-Vector physically?
What are the two ways in which it can change?
The Q-vector is the rate of change of the horizontal temperature gradient, ∇θ, following the geostrophic flow. This includes both changes in the magnitude of ∇θ (i.e., the strength of a front) and the orientation of ∇θ (i.e., the orientation of a front).
How would you determine the orientation of a Q-Vector?
- Find the vector change of the geostrophic wind along an isotherm
- Turn 90 degrees clockwise
How do you diagnose vertical motion using the kinematic method?
Infer or calculate vertical motion using horizontal wind fields and the continuity equation
What method of diagnosing vertical motion is used in hydrostatic models?
Kinematic
What are some disadvantages of the kinematic method?
- Falls apart in data sparse regions
2. Need to be cautious about divergence vs. diffluence/convergence vs. confluence.
What two methods of vertical motion diagnosis are based on the QG approximation?
Omega and Q-Vectors
What is the main advantage of the Omega equation?
Can help infer large-scale vertical motion from traditional synoptic analyses
What are the challenges that arise from using the Omega equation? (List 5.)
- Simplifying assumptions (such as the LaPlacian)
- Term cancellation
- Need to evaluate multiple levels for differential vorticity advection
- Doesn’t account for circulations generated by mesoscale systems
- Smoothing needed with higher resolution model data.
What is the main advantage of the Q-Vector method?
Eliminates term cancellation and multi-level problems posed by traditional omega equation
What are the challenges that arise from using the Q-Vector method? (List 3.)
- Extremely difficult to apply visually
- Doesn’t account for circulations generated by mesoscale systems
- Smoothing needed with higher resolution model data
What is raw model vertical velocity based on? (both hydrostatic and non-hydrostatic models)
- Hydrostatic – kinematic method
2. Non-hydrostatic – vertical momentum equation
What does the greek letter chi mean physically?
Geopotential Tendency
What term is on the left hand side of the height tendency equation?
The 3D Laplacian acting on chi. Approximated as a minus sign
What is the first term on the right hand side of the height tendency equation?
Vorticity advection term
What does (cyclonic/anticyclonic) vorticity advection mean in the height tendency equation as far as diagnosis of geopotential height?
Falling heights/rising heights
Where do we typically evaluate the vorticity advection term of the height tendency equation?
500 mb
What is the second term on the right hand side of the height tendency equation?
Temperature advection term
What does (positive/negative) temperature advection result in as far as diagnosis of geopotential height?
Height falls/height rises
