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
In the SH winter, the strongest flow is over two locations. What are these?
Australia and western Pacific
In the SH winter, there is a secondary jet maximum. Where is this located?
between Africa and Antarctica.
In the NH summer, there are (weak/strong) circumpolar (easterlies/westerlies).
- weak
- westerlies
What is the reasoning for why there are weak circumpolar westerlies in the NH summer compared to the winter?
height gradients are further north than in the winter.
In the NH summer, what is the typical wave number pattern?
Where are the troughs located in accordance with this pattern?
4
- NE North America
- Bearing Sea
- Northern Russia
- Western Europe
In the NH summer, there is subtropical (ridging/troughing) with (easterly/westerly) monsoonal flow near the equator.
- ridging
- easterly
In the NH summer, there are (weaker/stronger) westerlies with a jet core poleward at what latitude?
- weaker
- 40 degrees
In the NH summer, the jet is (less/more) zonally continuous than in winter.
On which 2 continental coasts does this result in weaknesses?
- more
- Europe
- North America
True or False.
In the SH summer, a strong band of westerlies persist.
This leads to a slight retraction toward the (pole/equator) compared to winter, but it is (weaker/stronger) than in the NH.
- True
- pole
- weaker
Although weak, what is the typical wave number pattern for the SH summer?
3
In the SH summer, the jet is displaced slightly (poleward/equatorward) compared to the winter position.
poleward
True or False.
In the SH summer, the jet represents a strong zonal continuity.
This results in a (minimum/maximum) across southern Oceans.
- True
- maximum
What is the definition of blocking?
Jim loves his definitions. Like literally wants us to memorize them and spit them out on paper. Don’t be lazy, Kenna.
The large-scale obstruction of the normal west-to-east progression of cyclones, anticyclones, and upper-level waves at midlatitudes.
True or False.
Blocking patterns can persist in some instances of ten days.
True
What are the 3 primary types of blocking patterns?
1) High over low (Rex block)
2) Omega
3) High amplitude ridge
In what 2 regions is the rex block most common?
Over western North America and Europe
In regards to the rex block, the pattern is sometimes referred to as ____ _____.
split flow
What two influences likely play a role in the creation and persistence of rex blocks?
1) topography
2) land-sea contrasts
In an Omega block, there is typically a ______ pressure system sandwiched between two ______ pressure systems.
high
low
A high amplitude ridge, when beneath it, is mainly associated with (wet/dry) weather.
drt
A high amplitude ridge over the western U.S. in winter can be associated with what meteorological phenomenon?
persistent valley and basin fog
True or False.
Blocks are completely understood.
False
Blocking patterns can be the result of ________ interactions.
topographic
Blocks are frequently found over or upstream of major________ _________.
mountain ranges
Blocking patterns can form or be maintained in response to ________ ___________.
surface cycogenesis
In regards to blocking patterns, a high index pattern is typically characterized by what 3 properties?
1) zonal flow
2) progression
3) lack of blocking
In regards to blocking patterns, a low index patter is typically characterized by what 2 properties?
1) zonal flow
2) blocking
In regards to blocking patterns, what does vacillation mean?
alternating from high to low zonal index flows.
The motivation for QG theory arrives from the desire for a system of equations that are simplified but retain the key ________ processes necessary to describe, diagnose, and understand the behavior of ______-______ weather systems.
- dynamical
- large-scale
What is the overarching assumption of QG theory?
(This is probably pretty important.)
What does this enable us to neglect?
- The Rossby number is small
- It enables us to neglect the ageostrophic wind in some, (but not all) terms of the governing equations.
Because this could be something that Jim does.
By whom is the following quote?
In regards to QG theory….
“The equations and their derivation is admittedly difficult. It is important that one not merely memorize the equations by rote. It is much more important to understand what they mean physically.”
Howie Bluestein
On what 3 governing equations (and their simplified derivations) is QG Theory based?
1) Equations of motion
2) Continuity equation
3) Thermodynamic energy equation
The 1st step of the derivation of the horizontal momentum equation is to break down the momentum into what 2 components?
geostrophic and ageostrophic components
What 4 properties can we neglect (by scale analysis) in the derivation of the horizontal momentum equation? ( This is the 2nd step to the derivation.)
1) Friction
2) Advection of ageostrophic wind and vertical velocity
3) Advection of ageostrophic momentum
4) Local ageostrophic momentum tendency
What is the physical interpretation of the horizontal momentum equation and the ability to neglect certain terms?
(This one will take a while. But it’s in RED. So do it, bro.)
The rate of change of momentum following parcel motion is approximately equal to the rate of change of geostrophic momentum following geostrophic motion.
The 3rd step to the derivation for the horizontal momentum equation is to assume what type of plane in the midlatitude?
Beta-plane
Assuming a Beta-plane in the horizontal momentum equation allows us to assume what about the coriolis parameter in the geostrophic wind relationship?
It’s constant know what I’m saaaaaayin’ ma-fucka?
The 4th step of deriving the horizontal momentum equation is use the assumptions from the previous 3 steps to rewrite the horizontal momentum equation.
(This isn’t a question. It’s just in the notes. A CYA typa thing.)
I vant to taste you like yogurt.
The 5th step in deriving the horizontal momentum equation is using scale analysis to show that the (ageostrophic/geostrophic) part of the Coriolis term can be neglected?
Ageostrophic
The physical interpretation of the horizontal momentum equation shows that the first term on the RHS represents the Coriolis force acting on the ___________ wind, which in turn leads to an (acceleration/deceleration) of the geostrophic flow perpendicular to the ageostrophic wind.
- ageostrophic
- acceleration
Has Jim come up with a good interpretation of the 2nd term on the RHS of the horizontal momentum equation?
Hell nah
In QG theory, what assumption can we make about vertical structure on the atmosphere?
Do we typically prefer (or does Jim prefer?) the height or pressure coordinate form?
- Hydrostatic approximation
- pressure coordinate
What is the physical interpretation of the QG form of the continuity equation?
The geostrophic wind is nondivergent. Divergence and vertical velocity are associated with the ageostrophic flow.
Similar to the momentum equation, the thermodynamic energy equation neglects the advection of __________ by the _____________ wind.
However, the effects of _________ ________ are retained since this property has a major influence on temperature through adiabatic warming and cooling.
- temperature
- ageostrophic
- vertical velocity
In the QG form of the thermodynamic energy equation, to what is “sigma” proportional?
Static stability
In the QG form of the thermodynamic energy equation, we typically assume that the flow is _______, though it is possible to include the antonymous effects.
adiabatic
The QG momentum equation, geostrophic wind relationship, hydrostatic approximation, continuity equation, and thermodynamic energy equation form a closed set of equations for what 5 dependent variables?
1) geopotential (phi)
2) geostrophic wind (V_g)
3) ageostrophic wind (V_ag)
4) vertical velocity (omega)
5) temperature (T)
The geostrophic relative vorticity is derived by taking the ______ of the ________ wind.
- curl
- geostrophic
According to Jim, whenever we see the following:
(1/f)*Laplacian(phi), we should think of what atmospheric phenomenon?
Geostrophic relative vorticity
Cyclonic (positive in NH) geostrophic relative vorticity is associated with (minima/maxima) in Z.
minima
Anticyclonic (negative in NH) geostrophic relative vorticity is associated with (minima/maxima) in Z.
maxima
The QG Vorticity Equatiopn is derived by taking the ____ of the ___ ________ equation.
- curl
- QG momentum
What two processes change the geostrophic relative vorticity at a point?
1) Geostrophic absolute vorticity advection
2) Stretching or Compression (or convergence and divergence)
The rate of change of geostrophic absolute vorticity is positive if the advection is (cyclonic/anticyclonic). This is (positive/negative) in the NH.
- cyclonic
- positive
The rate of change of geostrophic absolute vorticity is negative if the advection is (cyclonic/anticyclonic). This is (positive/negative) in the NH.
- anticyclonic
- negative
The rate of change of geostrophic absolute vorticity is negative if (stretching/compression) is occurring (in the NH).
compression
The rate of change of geostrophic absolute vorticity is positive if (stretching/compression) is occurring (in the NH.)
stretching
The total form of the QG vorticity equation physically means that following the flow, only ________ and _______ cause the geostrophic absolute vorticity to increase, respectively.
- stretching
- compression
What is the Omega equation used to diagnose?
large-scale vertical motion
What 2 equations are used to derive the QG Omega equation?
1) QG thermodynamic equation
2) QG vorticity equations
What are the two terms of the Omega equation?
1) Differential vorticity advection term
2) Temperature advection term
Regarding the Omega equation, the LHS (Jim's Term A) is essentially the 3-D Laplacian acting on what variable? For sinusoidal (wave-like) patterns, the Laplacian can be approximated by what mathematical operator?
- omega
- a minus sign
The differential vorticity advection term of the Omega equation is proportional to what (simple) variable?
- w (vertical velocity)
_________ vorticity advection increasing with height indicates ascent.
- cyclonic
________ vorticity advection increasing with height indicates descent.
- anticyclonic
In regards to the Omega equation, we typically assume that the vorticity at low levels is ________ so that
1) Cyclonic vorticity advection (CVA) @ 500mb indicates_________.
2) Anticyclonic vorticity advection (AVA) @ 500mb indicates _________.
- weak
- ascent
- descent
In practice, we often use the the advection of absolute vorticity (as opposed to geostrophic absolute vorticity) by the geostrophic wind since most maps display the _____-mb height and ________ _________ (rather than geostrophic absolute vorticity).
- 500
- absolute vorticity
In regards to the Omega equation, the temperature advection term is proportional to what simple variable?
w - vertical velocity
Match the appropriate terms.
A maximum in (warm/cold) advection indicates (ascent/descent).
- warm, ascent
- cold, descent
In regards to the temperature advection term of the Omega equation, the Laplacian operator is such that any (maximum/minimum) in temperature advection indicates ascent and any (maximum/minimum) indicates descent.
- maximum
- minimum
Just read. No question.
In practice, we often diagnose the advection of temperature by the total wind rather than the advection of temperature by the geostrophic wind since many maps display the total wind in either vector or barb form.
Fried or fertilized?
For using the Omega Equation in practice, we are usually concerned with _______-to_______ tropospheric vertical motions since this is what affects the development of clouds, precipitation, and surface weather systems.
mid-to-upper
For using the Omega Equation in practice,, we typically evaluate 500-mb ________ advection and 850- or -700-mb ________ advection.
- vorticity
- temperature
For using the Omega Equation in practice, it is important to consider how intense the _______ for ________ is.
- forcing
- ascent (or descent if interested in subsidense - e.g., formation of wintertime cold pools in west)
For using the Omega Equation in practice, it is important to consider if the right-hand terms _________ or _______.
- reinforce
- cancel (which can lead to ambiguities)
Just know it. I’m high and I couldn’t come up with a question).
For using the Omega Equation in practice, it is important to consider if there is sufficient moisture available for cloud an precipitation forecasting.
Shfifty-five
For using the Omega Equation in practice, it is important to consider if there are ____-_____ mechanisms that might be important to reinforce or obscure the QG signal.
non-QG (e.g., mountain effects, sub-QG circulation systems such as fronts and gravity waves)
True or False.
In regards to Omega Equation, one application challenge with high-resolution model guidance is that QG information can be swamped by the detailed predictions produced by the high-resolution model guidance.
True
In regards to Omega Equation, one application challenge with high-resolution model guidance is that the use of filters that remove (small-scale/large-scale) features is often necessary to see the forest through the trees.
(Holy fuck Jim that analogy is blowing my mind right now.)
Alternatively, the omega equation could be solved using a “________-__________” method to obtain omega.
- small-scale
- successive overrelaxation.
In regards to the Omega Equation, the large-scale _______ _________ can be diagnosed from the differential vorticity advection and the horizontal temperature advection.
This is typically done using the ___-mb absolute vorticity advection and the ___- or ___-mb temperature advection.
- vertical motion
- 500
- 700, 850
In regards to the Omega Equation, the resulting vertical motion field represents a component of the ___________ ____________ __________ (3 words) that develops to maintain thermal wind balance.
ageostrophic secondary circulation
