Midterm II Flashcards
The barotropic vorticity equation can be used to illustrate the important role that __________ rotation and the advection of ________ _________ play in the behavior of upper-level waves.
- planetary
- planetary vorticity
What does it mean when we assume a barotropic atmosphere?
Density depends only on pressure.
What two assumptions are made to simplify the vorticity equation to what is known as the barotropic vorticity equation?
- the atmosphere is barotropic
2. the motion is purely horizontal
What is the physical interpretation of the barotropic vorticity equation?
Absolute vorticity is conserved following the parcel motion, which is purely horizontal.
What are the 2 biggest advantages to using the barotropic voriticity equation?
- It is the simplest model of large-scale fluid motion
2. It allows us to diagnose the role of relative and planetary vorticity on the large-scale weather systems.
If a parcel is in southerly flow in the NH with no initial relative vorticity, what type (anticyclonic vs. cyclonic) of relative vorticity must the parcel acquire in order to conserve absolute vorticity?
anticyclonic
Strong northerly outflow from the ITCZ or other area of tropical convection typically turns _________ and can form a _________ _____.
- anticyclonically
- subtropical jet
At a point, the figure vorticity field is determined by the __________ of relative and planetary vorticity.
advection
For strong northerly flow with no initial relative vorticity, the relative vorticity at a point must _________ due to the advection of planetary vorticity.
increase
The “carving out” of an upper-level trough by strong northerly flow can be viewed as the result of ________ _________ advection. (2 words)
planetary vorticity
What is the term “Rossby wave” used to describe?
Basically a definition here. Memorize it.
A planetary-scale wave whose motion characteristics are influenced by the Beta effect.
The barotropic vorticity equation can be used to derive what equation?
Rossby wave phase speed equation
Rossby waves always propagate _______ relative to the mean flow. This is typically _______ in the midlatitudes.
- upstream
- westward
True or False.
Wind moves through a Rossby wave.
True. Relative to an air parcel, Rossby waves move upstream.
Upper-level waves move (slower/faster) than the flow.
slower
The phase speed of a long wave is (slower/faster) than a short wave.
Explain this mathematically using the Rossby wave phase speed equation.
- slower
- as L increases, [ßL^2)/(4π^2)] increases, and
c = U - [(ßL^2)/(4π^2)] decreases.
Short waves progress downstream (more/less) rapidly than long waves. (Short waves/long waves) appear to be steered by (short waves/long waves).
- more
- short waves
- long waves
Rossby wave movement is the result of a battle between two types of advection. What are these?
relative vorticity advection and planetary vorticity advection
In the Rossby wave phase speed equation, if “f” was constant, the wave speed would simply be controlled by the advection of _______ _______ and the waves would move with the ______ _______.
- relative vorticity
- mean flow
In a Rossby wave, the _______ _______ advection acts to cause the wave to move upstream, and the wave moves _______ than the mean flow.
- planetary vorticity
- slower
Rossby waves move upstream because of the influence of ______ _______ advection.
-planetary voriticity
Long waves move more slowly than short waves because the planetary vorticity advection becomes (more/less) dominant as wavelength increases.
- more
Describe the sign of “c” for the following scenarios and whether the wave is stationary, progresses, or retrogrades:
1) n > n_s
2) n = n_s
3) n < n_s
1) c > 0, wave progresses
2) c = 0, wave is stationary
3) c < 0, wave retrogrades
Since n_s is proportional to √(1/U), as U increases, what happens to n_s?
This means that as the mean zonal flow increases, there are (fewer/more) stationary or retrogressive waves, and the overall patter becomes more (stationary/retrogressive/progressive).
- n_s gets smaller
- fewer
- progressive
Since n_s is proportional to [cos(phi)]^(3/2), as latitude (phi) increases, what happens to [cos(phi)]^(3/2) and n_s?
Thus, a wave of a given wave number is (more/less) likely to be progressive at high latitudes than low latitudes.
There is an important caveat here. What is it?
- [cos(phi)]^(3/2) decreases and n_s gets smaller
- more
- the caveat is that some of the most important blocks occur in the mid-to-high latitudes
Potential vorticity is conserved under what two conditions?
1) adiabatic flow
2) frictionless flow
What are the two components of potential vorticity?
1) Absolute vorticity in isentropic coordinates
2) Static Stability
For potential vorticity, isentropic coordinates use ________ ________ for horizontal surfaces.
potential temperature
For potential vorticity, potential temperature decreases with height unless the stability of the atmosphere is __________.
superadiabatic
For potential vorticity, the absolute vorticity in isentropic coordinates is the component of ________ ________ normal to the ___________ __________ surfaces.
- absolute vorticity
- potential temperature
For potential vorticity, we can (usually) assume that the absolute value of absolute vorticity in isentropic coordinates is equal to the absolute vorticity in
_______ __________.
height coordinates
For potential vorticity, given that potential temperature increases with height, a large potential temperature gradient (with height) represents what type of static stability?
What does a small gradient with height represent in terms of stability?
- strong static stability
- weak static stability
If potential vorticity is conserved, then an increase in the absolute vorticity (in isentropic coordinates) must be accompanied by a(n) (increase/decrease) in the vertical potential temperature gradient in pressure coordinates.
decrease
If potential vorticity is conserved, then a decrease in the absolute vorticity (in isentropic coordinates) must be accompanied by a(n) (increase/decrease) in the vertical potential temperature gradient in pressure coordinates.
increase
If potential vortcity is conserved, and a fluid column is stretched, then the absolute vorticity in isentropic coordinates must (increase/decrease).
increase
If potential vorticity is conserved, and a fluid column is compressed, then the absolute vorticity in isentropic coordinates must (increase/decrease).
decrease
If potential vorticity is conserved, stretching (increases/decreases) static stability.
decreases
If potential vorticity is conserved, compression (increases/decreases) static stability.
increases
For potential vorticity, vertical motion assumes the bottom of the column remains where?
at the ground
For synoptic application in potential vorticity, in the absence of other forcings, northerly flow tends to be associated with __________.
subsidence
For synoptic application in potential vorticity, in the absence of other forcings, northerly flow with (cyclonic/anticyclonic) curvature tends to be associated with strong subsidence.
anticyclonic
For synoptic application in potential vorticity, in the absence of other forcings, northerly flow with (cyclonic/anticyclonic) curvature tneds to be associated with little vertical motion or weak ascent.
cyclonic
In the NH winter, a circumpolar vortex exists. This causes (lower/higher) heights over the pole.
lower
What is a typical wave number (major troughs and ridges) in the NH winter?
3
In the NH winter, where are the weaker heights located?
over Eurasia
In the NH winter, there is an enhanced height gradient over the (east/west) Pacific and (east/west) Atlantic
west
west
In the NH Winter, enhanced gradients over the west Pacific and west Atlantic lead to Pacific and Atlantic _____/_______ _________.
jets
storm tracks
In the NH winter, there are 2 major jet cores. Where are these located and what are they called?
- West Pacific; Pacific jet
- West Atlantic; Atlantic jet
In the NH winter, there is (weaker/stronger) flow over western NA and western Europe. This means that split flow occurs here.
weaker
The SH winter has a more (maritime/continental) environment compared to the NH.
What are the two primary reasons for this?
- maritime
1) High-elevation continent at the pole
2) Less extensive mid-latitude topography
In the SH, the winter is dominated by a (strong/weak) and (symmetrical/asymmetrical) circumpolar vortex.
- strong
- symmetrical
In the SH winter, over what region are the lowest heights found?
Ross Sea
In the SH winter, what is the typical wave number pattern?
Is it weak or strong?
- 3
- weak
In the SH winter, there is a more zonally continuous _____ than in the NH winter.
jet