Final Exam Flashcards
Define Cyclogenesis. (Don’t worry, it’s a short definition.)
The formation of a cyclone.
Define Cyclolysis. (Again, a short definition.)
The decay of a cyclone.
Conceptual frameworks for cyclogenesis are often based on (vorticity/pressure) rather than (vorticity/pressure).
vorticity
pressure
Pressure tendencies, height tendencies, and geostrophic vorticity tendencies are coupled through the ______________ __________ relationship.
geostrophic wind
Pressure, height, and geostrophic vorticity tendencies are intrinsically linked.
An increase in surface vorticity is associated with height and pressure (falls/rises).
A decrease in surface vorticity is associated with height and pressure (falls/rises).
falls
rises
We can diagnose cyclogenesis using the vorticity equation, but we ignore which 3 terms?
friction
tilting
solenoidal
Lower tropospheric (stretching/compression) is a mechanism for voriticty generation and cyclogenesis. This is the same as (ascent/descent).
stretching
descent
Answer the following questions in regards to an example of cylogenesis.
An upper-level trough and associated area of (CVA/AVA) and (ascent/descent) overtake a low-level frontal zone. The low-level frontal zone is characterized by (high/low) initial (relative/absolute) vorticity. (Stretching/Compression) associated with the upper-level trough most effectively generates vorticity along the front. This is due to the (absolute/relative) vorticity multiplier in the vorticity equation.
CVA ascent absolute stretching absolute
Assuming hydrostatic balance, define pressure. (easy)
The weight of the overlying atmosphere.
Surface pressure changes are due to integrated ________ _____________.
mass divergence
Cyclogenesis occures when (divergence/convergence) aloft exceeds (divergence/convergence) at low levels, resulting in net mass (divergence/convergence) and surface pressure (falls/rises).
divergence
convergence
divergence
falls
QG ascent results in (stretching/compression) and pressure (falls/rises).
stretching
falls
Ignoring friction, and in regards to the QG omega equation, what 3 things can contribute to ascent, pressure falls, and cyclogenesis?
These effects are most pronouned when static stability is (high/low).
1) Vorticity advection becoming more cyclonic (or less anticyclonic) with height.
2) A local maximum in temperature advetion.
3) A local maximum in diabatic heating.
- low
In regards to vorticity advection becoming more cyclonic with height as a contributor to cyclogenesis, we typically look for (CVA/AVA) at ______ mb.
CVA
500
In regards to cyclogenesis and the contributions of a local maximum in temperature advection, we typically look for (warm/cold) advection, such as along a (warm/cold) front or occluded front.
warm
warm
In regards to cyclogenesis and static stability, this is exemplified by an upper-level trough inducing cyclogenesis more easily if the static stability is (low/high).
low
Synoptic experience in cyclogenesis:
(CVA/AVA) downstream of an upper-level trough contributes to pressure (falls/rises) and cyclogenesis.
CVA
falls
Synoptic experience in cyclogenesis:
(Warm/cold) advection along a (warm/cold) front contributes to pressure (falls/rises) and cyclogenesis.
warm
warm
falls
Synoptic experience in cyclogenesis:
Diabatic heating contributes to pressure (falls/rises) and cyclogenesis.
falls
Synoptic experience in cyclogenesis:
In frontal cyclone development, CVA, warm advection, and diabatic heating all contribute to a mutual ______________ of the surface cyclone and upper level wave.
amplification.
Synoptic experience in cyclogenesis:
Stretching (downstream/upstream) of topography can contribute to cyclogenesis.
downstream
In an idealized example of cyclogenesis, consider a 3-part conceptual model, and answer the following about PART 1:
- 500-mb (CVA/AVA) contributes to surface cyclogenesis
- (Low/Upper)-level warm advection ahead of cyclone amplifies (downstream/upstream) ridge
- (Low/Upper)-level cold advection ahead of cyclone amplified (low/upper)-level trough.
CVA Low downstream Low Upper
In an idealized example of cyclogenesis, consider a 3-part conceptual model, and answer the following about PART 2:
- Wavelength of upper-level wave (shortens/lengthens)
- (CVA/AVA) intensifies
- Surface development (continues/diminishes)
- (Low/Upper)-level warm and cold advection intensify
- Surface cyclone and upper-level (trough/ridge) mutually amplify
- Diabatic (heating/cooling) along warm/occluded front further enhances surface development and (low/upper)-level wave amplification.
shortens CVA low trough heating upper
In an idealized example of cyclogenesis, consider a 3-part conceptual model, and answer the following about PART 3:
- Cyclone becomes veritically (stacked/removed)
- QG forcing for (ascent/descent) weakens
- Development (ceases/revitalizes)
stacked
ascent
ceases
Synoptic experience in anticyclogenesis:
AVA (upstream/downstream) of an upper-level ridge contributes to pressure (rises/falls) and anticyclogenesis
downstream
rises
Synoptic experience in anticyclogenesis: A local (maximum/minimum) in cold advection contributes to pressure rises and anticyclogenesis.
minimum
Synoptic experience in anticyclogenesis:
Diabatic (radiational) (heating/cooling) contributes to pressure rises and anticyclogenesis.
cooling
Synoptic experience in anticyclogenesis:
(Stretching/Compression) upstream of topography can contribute to anticyclogenesis.
Compression
From a PV perspective, cyclogenesis results from the coupling and mutual amplification of surface (cyclonic/temperature) and upper-level (cyclonic/temperature) PV anomalies, with contributions from diabatically generated PV (cyclonic/anticyclonic) anomalies.
temperature
cyclonic
cyclonic
From a PV perspective, a surface (warm/cold) anomaly acts like a cyclonic PV anomaly ad a surface (warm/cold) anomaly acts like an anticyclonic PV anomaly.
warm
cold
Cyclogensis from a PV perspective:
Answer the questions to the first 2/5 steps of cyclongenesis.
1) Upper-level (cyclonic/anticyclonic) PV anomaly overtakes a (low/upper)-level frontal zone.
2) (Cyclonic/anticyclonic) circulation associated with upper-level PV anomaly induces a (warm/cold) tongue along the frontal zone.
cyclonic
low
cyclonic
warm
Cyclogensis from a PV perspective:
Answer the questions to the last 3/5 steps of cyclongenesis.
3) Warm tongue acts like a(n) (cyclonic/anticyclonic) PV anomaly, inducing a(n) (cyclonic/anticyclonic) circulation that extends upward and further amplifies the upper-level (cyclonic/anticyclonic) PV anomaly
4) The upper-level and surface thermal anomalies become phase locked and mutually (amplify/dampen), resulting in cyclogenesis.
5) (Adiabatically/Diabatically) generated PV can be a third building block in the process.
cyclonic cyclonic cyclonic amplify diabatically
What is the Norwegian Cyclone Model?
1) Conceptual model describing the ________ ______ and ________ of extratropical cyclones.
2) Developed after World War I by the _______ School of ____________.
3) Defined modern meteorological ___________.
4) It’s still widely used today.
life cycle and dynamics
Bergen school of meteorology
analysis
Part 1 of the initial description of an ideal cyclone explains that
“two airmasses (warm and cold) separated by a fairly distinct (surface/upper-level) boundary that runs through the center of the system.”
surface
In regards to Part 2 of the initial description of an ideal cyclone, is the following statement TRUE or FALSE?
“the surface boundary is imagined to continue through a greater part of the troposphere at a small angle to the horizon.”
True
Part 3 of the initial description of an ideal cyclone explains that
“(warm/cold) air in the (warm/cold) sector is conveyed by a SW or W current and (ascends/descends) the wedge of (warm/cold) air ahead of the (warm/cold) front, producing (warm/cold)-frontal precipitation.”
warm warm ascends cold warm warm
Part 4 of the initial description of an ideal cyclone explains that
“the intrusion of (warm/cold) air from behind the system into the (warm/cold) sector lifts the (warm/cold) airmass, producing (warm/cold)-frontal precipitation.
cold
warm
warm
cold
What are the 4 phases of the Norwegian Cyclone Model?
Initial Phase
Open Wave Phase
Secluded/Occluded Phase
Maturity/Death
In the initial phase of the Norwegian Cyclone Model, two oppositely directed currents of different ___________ are separated by a nearly straight boundary.
This boundary begins to bulge toward the (cold/warm) air at the place where the cyclone will form.
temperatures
cold
In the open wave phase of the Norwegian Cyclone Model,
- the amplitude of the warm wave (increases/decreases)
- (warm/cold) air moves cyclonically around the low center
- (Warm/Cold) sector narrows
increases
Cold
Warm
In the secluded phase of the Norwegian Cyclone Model, the (cold/warm) front overtakes the (cold/warm) front south of the low center. A piece of the (warm/cold) sector is cut off.
cold
warm
warm
In the occluded phase of the Norwegian Cyclone Model, the remaining part of the (warm/cold) sector is removed from the surface.
warm
In the maturity/death phase of the Norwegian Cyclone Model, the occluded front dissipates and the cyclone becomes (symmetric/asymmetric) vortex of (cold/warm) air.
symmetric
cold
In regards to the vertical evolution of the open wave phase,
- two wedges of (cold/warm) air approach each other.
- intermediate (cold/warm) sector air is lifted
- Transforms (potential/kinetic) energy to (potential/kinetic) energy.
cold
warm
potential
kinetic
In regards to the vertical evolution of the occluded phase,
- once two wedges have met on the ground, the upper (warm/cold) sector is lifted until the (warm/cold) sector has (warmed/cooled) adiabatically to the temperature of its surroundings.
- throughout this phase, the cyclone gains (potential/kinetic) energy
warm
warm
cooled
kinetic
An essential condition for cyclone formation is coexistence of warm and cold air (adjacent/separate) to each other.
adjacent.
All cyclones which are not yet occluded have (increasing/decreasing) kinetic energy.
increasing
Soon after occlusion, the cyclone begins to (fill/empty).
fill
In later stages of cyclone formation, the cyclone becomes a (homogenous/heterogenous) vortex of (cold/warm) air that consumes the previously generated kinetic energy.
homogenous
cold
What are the two types of occlusion?
Which type is most common?
warm and cold
cold
A cold type occlusion forms if air behind the cold front is (colder/warmer) than air ahead of the warm front.
This has characteristics of (cold/warm) front with (narrow/broad) precipitation zone.
colder
cold
narrow
A warm type occlusion forms if air behind the cold front is (warmer/colder) than air ahead of the warm front.
This has characteristics of (cold/warm) front with (narrow/broad) precipitation zone.
warmer
warm
broad
In a secondary cold front, the cold air may contain a series of secondary cold fronts accompanied by only small contrasts in ___________ and ________.
temperature and wind
The appearance of a strong secondary cold front that is stronger than the primary cold front indicates a ______________ of the cylclone
reinforcement
In refining the Norwegian Cyclone Model, what three new features were identified?
1) upper-level cold front
2) bent-back occlusion
3) false warm sector
An upper-level cold front accompanies (warm/cold)-type occlusions.
warm
A bent-back occlusion extends into (polar/subtropical) airstream (in front of/behind) the low.
polar
behind
The false warm sector occurs between what two features?
between the bent-back occlusion and primary cold front.
What two life cycle refinements were made to the Norwegian Cyclone Model in regards to the stages?
1) antecedent stage
2) nascent stage
The refined antecedent stage to the Norwegian Cyclone Model is similar to what famous paper’s description?
Bjerknes and Solberg (1922)
In the refined Nascent stage of the Norwegian Cyclone Model, there is a newly formed wave with velocity nearly equal to that of the (warm/cold)-sector air near the (ground/mid-troposphere)
warm
ground
Refinements to the wave cyclone phase of the NCM include
1) further (development/reduction) of cyclone and frontal wave
2) frontolysis occurs along (warm/cold) front (near/away from) low center
3) phase (lag/syncing) of upper-level wave relative to surface wave
development
cold
near
lag
Refinements to the occluded stage of the NCM include
- (cold/warm) front climbs (cold/warm) front and forms upper-level (cold/warm) front
- Pressure (ridge/trough) forms to rear of cyclone and rotates (cyclonically/anticyclonically) around the low center.
- (True or False) Near low-center, a bent-back occlusion may coincide with trough
cold warm cold trough anticyclonically True
Refinements to the occluded stage of the NCM include
- (More/less) removed from low center; it may become a non-frontal (trough/ridge)
- Cyclone regeneration can occur if bent-back front is (longer/shorter) and (stronger/weaker) than normal and separates polar airmasses of differing temperature.
More
trough
longer
stronger
In regards to modifications and extensions of the NCM and frontal structure/dynamics…
depiction of the polar front as a discontinuity separating tropical and polar airmasses is an (underidealizaiton/overidealization).
overidealization
In regards to modifications and extensions of the NCM and frontal structure/dynamics…
Upper-level and surface-based fronts may be (continuous/discontinuous) and have (differing/similar) dynamics.
discontinuous
differing
In regards to modifications and extensions of the NCM and frontal structure/dynamics…
surface-based fronts may have (extreme/calm) intensity at the ground, but (weaken/strengthen) with height.
extreme
weaken
In regards to modifications and extensions of the NCM and frontal structure/dynamics…
Frontal zones are better regarded as regions of (active/inactive) frontogenesis rather than (impermanent/semi-permanent/permanent) phenomenon.
active
semi-permanent
In regards to modifications and extensions of the NCM and frontal structure/dynamics…
Fronts are often a (cause/consequence) of cyclogenesis rather than the (cause/consequence)
consequence
cause
In regards to modifications and extensions of the NCM and cyclone dynamics…
Cyclone development may be viewed as a consequence of (baroclinic/frontal) instability rather than (barclinic/frontal) instabilities.
baroclinic
frontal
In regards to modifications and extensions of the NCM and cyclone dynamics…
There are 3 major building blocks for observed cyclogenesis (thanks to the discovery of jet stream and development of PV thinking). Name these 3 major building blocks.
1) Upper-level trough/cyclonic PV anomaly
2) Surface front (surrogate cyclonic PV anomaly)
3) Diabatic Heating
In regards to modifications and extensions of the NCM and cyclone dynamics…
There are patterns of cyclone development not envisioned by the Bergen School.
Name an example.
Cyclogenesis in polar airstreams.
What is the definition of Lake Effect Snow, according to the Glossary of Meteorology?
Precipitation occurring near or downwind from the shore of a lake resulting from the warming (destabilization) and moistening of relatively cold air during passage over a warm body of water.
What are 5 additional factors to lake effect snow?
1) lake-lake interactions and aggregate effects (Great Lakes)
2) Boundary layer and thermally driven circulations
3) Orography
4) surface roughness contrasts
5) Ice cover
What are 5 morphological types of Lake Effect Snow?
1) Broad Coverage
2) Long-Lake-Axis-Parallel (LLAP) band
3) Hybrid
4) Shoreline Band
5) Mesoscale Vortices
What feature is responsible for the broad coverage type of Lake Effect Snow?
Horizontal Roll or Benard Convection
How are LLAP bands, which produce the heaviest snowfall, organized?
By land-breeze-induced convergence
Hybrid types of Lake Effect Snow have characteristics of what 2 morphological types?
Hybrid types typically feature a connection to (upstream/downstream) lake(s).
broad coverage and LLAP
upstream
Shoreline bands of lake effect snow form along (land/lake) breeze during (weak/strong) flow. The exhibit (little/much) movement.
land
weak
little
Mesoscale vortices type of Lake Effect Snow typically form where the shore is “_______-______.” This phenomenon is relatively rare.
bowl-shaped
The Tug Hill Plateau experiences what morphological type of lake effect snow?
Some of the most intense snowstorms on Earth happen here,.
LLAP bands
In regards to the diurnal variability in the Tug Hill Plateau…
- in fall and spring, lake-effect is (more/less common) overnight/early int he morning hours, and (more/less) common afternoon/evening.
- (No/Strong) signal in winter
- (Stronger/weaker) signal than over GSL
more
less
no
weaker
For Lake Effect Snow on the GSL, match the percentages with how often the specific type of lake effect snow occurs.
1) Non-banded
2) Mixed Mode
3) Banded
a) 25%
b) 20%
c) 55%
Non-banded - 55%
Mixed Mode - 25%
Banded - 20%
IN GSL Lake Effect Snow, do 1) rare and intense or 2) common and mild events dominate?
rare and intense
93% of GSL lake effect snow events occurs at lake-700-mb temperature gradients greater than or equal to what temperature (in dec C)?
16 deg C
For predicting Lake Effect Snow in the GSL, is it more appropriate to use a seasonally varying thresholed for lake-700-mb temperature gradients, or a fixed threshold?
varying threshold
Under marginal instabilities, environment conditions (moisture, wind direction) in the GSL are more frequently favored for lake-effect in (winter/fall and spring) than in (winter/fall and spring).
winter
fall and spring
True or False.
GSLE is not sensitive to moisture flux.
False.
What are 3 potential orographic effects to LES?
1) Precip enhancement
2) modificaition of the lake-effect system (initiation, intensity, morphology)
3) lake-effect systems can be altered by upstream and downstream topography
What is the hypothesis of LES in Japan in regards to the capping inversion?
Height of the CAP relative to mountain crest affects orographic ratio in lake-effect storms
Name 4 processes that influence lake-effect systems.
1) Upstream instability and moisture
2) Lake conditions (sfc temp, sub-sfc temp, salinity, ice cover)
3) Land breezes and PBL circulations
4) Orography
True or False.
Orographic influences only include precipitation enhancement.
If true, why doesn’t it affect anything else?
If false, what else does orography influence?
False.
initiation, intensiyt, and morphology of lake-effect systems
This is too much to remember, and I”m lazy, but be familiar with the following 5 unresolved issues.
1) Morphological controls
2) Role of the CAP in modulating orographic enhancement
3) Possible role of boundary layer turbulence in precipitation enhancement
4) Understanding (and predicting) the spectrum of lake-driven and terrain-driven processes that influence lake-effect storms in areas of complex terrain.
5) Interdecadal variability & lake size
