Exam II Flashcards
(160 cards)
1
Q
Under which of the following circumstances do errors in model physics have the highest impact?
A) When dynamic forcing is strong
B) When physical processes are strong
C) When dynamic forcing is weak
D) When physical processes are weak
A
B & C
2
Q
Which of the following elements help forecasters add value over NWP?
A) Continuous MetWatch
B) Use of MOS for rare events
C) Regular use of verification
D) Forecaster experience
A
A, C, & D
3
Q
Which of the following elements help forecasters add value over NWP?
A) Continuous MetWatch
B) Use of MOS for rare events
C) Regular use of verification
D) Forecaster experience
A
A, C, & D
4
Q
Which of the following tools help forecasters perform the continuous meteorological watch (MetWatch)?
A) Radar reflectivity and velocity
B) Medium-range NWP forecasts
C) Satellite depictions
D) Surface analyses
A
A, C, & D
5
Q
True or False:
Model analysis and forecaster experience have a direct impact on the final forecast issued by meteorologists.
A
True
6
Q
Which of the following situations present opportunities to improve on the NWP forecast?
A) Forecasting severe weather in the short range when convection is initiating
B) Forecasting precipitation for a landfalling hurricane
C) Forecasting temperature in the medium range when your area is in a stable block
D) Forecasting temperature in areas of rugged terrain
A
A,B, & C
7
Q
Which of the following statements about MOS guidance are correct? (Choose True or False for each option)
A) Data sets are seasonally stratified.
B) Model guidance will lead to a good forecast if environmental conditions are typical for the event.
C) Model guidance is skillful in forecasting atypical events.
D) Regional parameterization affects MOS guidance.
E) MOS guidance corrects for systemic errors in the NWP models.
A
A) True B) True C) False D) False E) True
8
Q
Choose the best answer.
A major snowstorm is to occur on the 10th of October at a station in Nebraska. The GFS MOS report has the following October 9-15 GFS Extended MOS forecasts for maximum and minimum temperature:
KLBF GFSX MOS GUIDANCE 10/08/xxxx 1200 UTC
Forecast Hour:
24 36 48 60 72 84 96 108 120 132
Max/Min Temperature:
30 57 26 31 17 33 27 43 33 48
Snow is rarely observed in early October at this location, and the air mass accompanying and following the storm is unusually cold. Forecast 850-hPa temperatures are expected to be at least 3 standard deviations below normal, which statistically is expected only 1% of the time. Based on this information, how would you adjust the forecast temperatures for Monday 12 October (day 4)?
A) I would use them as presented because MOS removes systematic bias.
B) I would use them as presented because MOS predicts extreme events well.
C) I would lower them because of the unusual snow cover and cold air mass.
D) I would raise them because of the unusual snow cover and cold air mass.
A
C
9
Q
Choose all that apply.
You are a TV meteorologist on a network 10 p.m. newscast in the Philadelphia, PA area. Your main concern is the potential for snow during rush hour (7 a.m. to 9 a.m. EST, or 12 to 14 UTC) of the next morning.
At 5 p.m. EST (22 UTC) your time, you reviewed the previous hour’s radars, surface observations, and corresponding forecasts of simulated composite radar reflectivity and lowest level reflectivity from the 18 UTC NAM/WRF-NMM run that day.
Given the data in these afternoon graphics, how would you assess the NAM forecast from 18 UTC valid at 21 and 22 UTC?
A) The observations indicate that the NAM is correctly developing precipitation in south-central Virginia.
B) The composite radar reflectivity indicates that the NAM is too fast developing precipitation in south-central Virginia
C) The observations indicate that the NAM is too slow developing precipitation in south-central Virginia.
D) The composite radar reflectivity indicates that the NAM is too slow developing precipitation in eastern North Carolina
A
C & D
10
Q
Choose all that apply.
Now you want to develop your forecast for the late evening news. The following 10 p.m. EST (03 UTC) data for observations and level 1 NAM/WRF-NMM 18 UTC run of simulated reflectivity valid at the same time are available. After viewing these graphics, answer the question below.
How do the observations now compare to the NAM/WRF-NMM observations in the mid-Atlantic states?
A) The advance of precipitation into central Maryland is too slow in the NAM.
B) The advance of precipitation into central Maryland is accurately predicted in the NAM.
C) The advance of precipitation into central Maryland is too fast in the NAM.
D) The forecast precipitation in the NAM shows signs of becoming banded.
A
A & D
11
Q
Choose the best answer.
The graphics here show the forecast of precipitation from the 18 UTC run of the NAM/WRF-NMM for the hours covering rush hour the next morning. Assume that temperatures will support snow throughout the Philadelphia PA area. The Short-Range Ensemble Forecasts (not shown) support the precipitation forecast of the NAM/WRF-NMM.
Use this information and graphics above to answer the question.
Based on these 1-hour precipitation graphics and verification of the movement of the precipitation shield from the previous two questions, what would your 10 p.m. forecast be for the next morning rush hour (7-9 a.m. EST, 12-14 UTC) in the Philadelphia PA area?
A) Snow will start before the beginning of the rush hour in the entire Philadelphia area.
B) Snow will start after the end of rush hour in the entire Philadelphia area.
C) Snow will not reach the Philadelphia area before, during, or after the morning rush hour.
D) Snow will overspread the Philadelphia area from south to north during the rush hour.
A
D
12
Q
Choose the best answer.
When assessing the certainty of a forecast using EFS products, which EFS limitation needs to be taken into consideration?
A) The greater uncertainty of initial conditions due to EFS initialization and perturbation methods.
B) The high resolution of EFSs and their ability to offer detailed information for high impact weather events.
C) The availability of detail for onset time of convection.
D) The probability of exceeding a forecast threshold.
A
A
13
Q
Determine whether each of the following options would be considered an advantage of EFSs when compared to deterministic models. Choose True or False for each option.
A) Information on the probability of a weather event.
B) Details about the degree of certainty in a forecast.
C) Improved spatial resolution.
D) Meteorological details for forecasts from 0 to 72 hours.
A
A) True
B) True
C) False
D) False
14
Q
Are each of the following an advantage of deterministic models when compared to EFSs? (Choose True or False for each option)
A) Resolution of mesoscale features.
B) Details about the location and amount of rainfall.
C) Details about wind speeds.
D) Details about the certainty of a forecast.
A
A) True
B) True
C) True
D) False
15
Q
What are 3 primary errors in data and quality control?
A
- Instrument Errors
- Representativeness Errors
- Converting remotely-sensed data into high-quality observations to be integrated with other data
16
Q
What are 3 types of representativeness errors?
A
- Vertical
- Horizontal
- Temporal
17
Q
What are 2 primary model initialization problems?
A
- First guess can sometimes overwhelm actual data.
2. First guess may result in good observations being ignored.
18
Q
What will poor analysis typical lead to in models?
A
Huge forecast errors.
19
Q
What are some of the most common atmospheric variables that are not routinely measured?
A
- Longwave & Shortwave Radiation
- Cloud Water & Ice Content
- Surface roughness of the ocean
- Turbulence
20
Q
What is the model’s initial impression of the atmosphere’s current condition?
A
The first guess (an earlier forecast)
21
Q
Where is the model’s first guess most easily modified?
Where is it least easily modified?
A
data-rich areas (CONUS)
data-poor areas (oceans)
22
Q
What are some ways to check the model’s first guess influence on the analysis?
A
1) Compare different model analyses to each other.
2) Compare model analyses to satellite, radar, and other real-time information.
23
Q
What are some common sources of error in the model?
A
1) Equations of motion are incomplete
2) Errors in the numerical approximation
3) Boundary conditions
24
Q
What is the horizontal resolution of an NWP model related to for grid point models?
For spectral models?
A
- the spacing between grid points
- the number of waves that can be resolved
25
What does 'resolution' represent in a grid point model?
| In a spectral model?
- the average area depicted by each grid point
| - the number of waves used
26
Why is it important to know the amount of area between grid points?
Because atmospheric processes and events occurring over areas near to or smaller than this size will not be included in the model.
27
In spectral models, what is the horizontal resolution designated by?
What does this variable indicate?
- "T" number
| - It represents the number of waves used by a spectral model
28
What does the "T" stand for in "T-number?"
| What does it indicate?
- Triangular Truncation
| - The particular set of waves used by a spectral model
29
What equation is the wavelength of the smallest wave in a spectral model represented as?
minimum wavelength = 360 degrees/N, where N is the total number of waves (the "T" number)
30
What is the equation used to represent the approximate grid spacing with the same accuracy as a spectral model?
delta-X = 360 degrees/3N
31
Do the dynamics of spectral models or grid point models retain better wave representation?
Spectral models
32
# Fill in the blanks.
Spectral model physics is calculation on a ________ with about _____ times as many grid lengths as number of waves used to represent data.
- grid
| - three
33
# Fill in the blanks.
Spectral models do a fine job with ____ waves in the free atmosphere, but have coarser representation of the _________, including surface properties.
- dry
| - physics
34
True or False?
The more physics that is involved in the
evolution of the forecast, the less the advantage in
spectral model forecasts compared to comparable
resolution grid point forecasts.
True
35
What two factors limit model representation of orography?
- The horizontal resolution of the model
| - The horizontal resolution of the terrain dataset used
36
What will happen to the terrain details provided in a model's dataset if it cannot resolve terrain features?
The terrain details will be averaged out
37
What two factors affect the character of model terrain?
Model resolution and terrain smoothing
38
What are 4 common shortcomings of model terrain representation?
1) Elevations of the highest mountain peaks or ranges are
generally less than in reality
2) Valleys are often not represented or are filled
3) Mountain range elevation is spread over a too-broad
horizontal area
4) Elevation gradients are underestimated
39
What part of a model's representation is a major factor in its ability to predict meteorological features induced by terrain?
Its representation of surface topography
40
What are some possible effects of inadequate model terrain on weather elements? (Choose all that apply.)
a) Shifting vertical motion maxima/minima away from the mountains due to insufficient terrain slope
b) Inaccuracies in forecasting the strength and location of the upper-level jet
c) Misplacing precipitation maxima and minima in complex terrain
d) Underestimating and broadening precipitation maxima
e) Difficulty in analyzing and forecasting upper-tropospheric height and temperature fields
f) Inability to depict downslope winds, valley winds, drainage winds, and other small-scale processes
g) Inability to depict mountain lee wave development and propagation
h) Difficulty in resolving and representing valley inversions and cold air damming
a, c, d, f, g, h
41
True or False:
Models do not have difficulty resolving features influenced or caused by the interface between land and large bodies of water.
False
42
True or False:
To complete one forecast, equations need to be solved for many variables at millions of grid points up to several thousands of times, totaling close to a trillion updates for each forecast variable.
True
43
How do computing resources affect NWP models?
They limit the resolution
44
Fill in the blanks:
The additional computing resources required to run a model at half its current horizontal resolution increase by a factor of _____, assuming no change to the _______ resolution or ______ size.
- eight
- vertical
- domain
45
Why does increased resolution increase demand on computing resources?
Because the model must determine values for more grid points.
46
What does the CFL criterion state?
“The speed of fastest waves in the model must be less than or equal to grid spacing divided by the time step”
47
What scientists created the CFL criterion?
Courant, Friedrichs, & Lewy
48
What would violating the CFL criterion lead to?
the "blowing up" of a finite-difference weather prediction model.
49
What must the CFL be in order for there to be stability?
Less than or equal to 1.
50
In a numerical model, why must one must look at a moving parcel often enough to keep track of its actual path?
To maintain numerical stability
51
True or False:
| In reality, NWP models generally use much longer time steps than would be computed by the CFL equation.
False---generally use much shorter time steps....
52
Why do NWP models generally use much shorter time steps than would be computed by the CFL equation?
This is due to instabilities in numerical methods and use of physical parameterization
53
True or False:
| Gradient intensity is limited by model resolution.
True
54
Is the relationship between the size of weather features to be predicted and the grid spacing in a gridpoint model important? (Yes or No)
Yes
55
Which of the features listed below can be resolved well by a 35-km resolution gridpoint model or T360 spectral model that might be used for extended prediction? For each feature, decide if it can be resolved well (yes, no, or to a limited extent).
a) Arctic plunge east of Rocky Mountains
b) Downslope windstorm
c) Cold-air damming
d) Snow band within East Coast low
e) Terrain-induced precipitation maxima/minima
f) Upper-level front
g) Synoptic surface front
h) Coastal front
i) Sea breeze circulation
j) Outflow boundary
k) MCS
l) Hurricane
a) yes
b) no
c) yes
d) limited
e) limited
f) yes
g) yes
h) limited
i) limited
j) no
k) limited
l) limited
56
Which of the features listed below can a mesoscale 10-km resolution model adequately resolve? For each feature, decide if it can be resolved well (yes, no, or to a limited extent).
a) Arctic plunge east of Rocky Mountains
b) Downslope windstorm
c) Cold-air damming
d) Snow band within East Coast low
e) Terrain-induced precipitation maxima/minima
f) Upper-level front
g) Synoptic surface front
h) Coastal front
i) Sea breeze circulation
j) Outflow boundary
k) MCS
l) Hurricane
a) yes
b) limited
c) yes
d) limited
e) limited
f) yes
g) yes
h) yes
i) limited
j) limited
k) limited
l) limited
57
Does a 4-km mesoscale model have sufficient resolution to resolve an existing mesoscale convective system (MCS)?
Yes, with limitations
58
Does a 4-km mesoscale model have sufficient resolution to define outflow boundaries associated with the MCS?
Yes, but with detail sensitivities
59
Does a 4-km mesoscale model have sufficient resolution to resolve individual cells and predict their track?
Yes, large supercells can be grossly resolved by a 4-km model, although their substructures such as the mesocyclone and wall cloud cannot.
60
A model's ability to resolve features depends not
| only on its horizontal resolution, but also on what? (3 things)
1) vertical resolution
2) number of vertical layers
3) physics package used to define a variety of surface and atmospheric processes.
61
What are limited-area models strongly constrained by?
Their boundary conditions
62
How do spectral models and grid point models represent the atmospheric column?
In discrete layers
63
What are some key features that need adequate vertical resolution?
1) Near-surface sharp inversions and superadiabatic lapse rates
2) Top of the boundary layer
3) Sloping frontal zones
4) Tropopause(s)
64
True or False: The ratio of the horizontal and vertical resolutions of a model must be consistent with the slope of the weather phenomena of interest.
True
65
If consistency between a model's horizontal and vertical resolution is not maintained, what can happen to the model's forecasts with fine resolution in one dimension?
It can actually be worse than forecasts with lower resolution.
66
Are a model's vertical layers typically distributed evenly? (Yes or No)
No
67
Fill in the blanks: Limited computational resources often require modelers to concentrate ________ layers in targeted layers to best depict atmospheric features of interest to _______ and _________ forecast problems.
- vertical
- global-scale
- medium-range
68
If you were designing a global model, where would you concentrate the model's vertical layers to improve day-1 to day-2 forecasts? (Choose the best answer)
A) Boundary Layer
B) Middle Troposphere
C) Jet-Stream Level
C
69
If you were designing a mesoscale model specifically to forecast convection initiation or lake effect snow, where would you concentrate your model's vertical layers? (Choose the best answer)
A) Boundary Layer
B) Middle Troposphere
C) Jet-Stream Level
A
70
If you were designing a model to follow midlatitude short waves and to predict their associated frontal waves and cyclogenesis events, where would you concentrate your vertical layers? (Choose all that apply)
A) Boundary Layer
B) Middle Troposphere
C) Jet-Stream Level
B & C
71
Fill in the blank.
With the growing need to predict ozone concentrations, the lengthening of medium- to long-range forecasts, and the development of advanced satellite data assimilation techniques, resolution of the __________ has become increasingly important.
stratosphere
72
In variational data assimilation schemes, the atmospheric radiances used to determine vertical atmospheric structure are dependent upon what?
Accurate forecasts of concentrations of shortwave and longwave radiation absorbers, such as ozone.
73
Fill in the blanks.
The largest positive impacts from the use of satellite data in forecasts for the Northern Hemisphere have occurred as a result of including stratospheric _______ concentration information in the variational assimilation system. This is most important for ______ areas, such as the North Pacific.
- ozone
| - oceanic data-void
74
Fill in the blank.
As resolution and forecast length increase, the need for improved models of surface heating and surface moisture sources encourages resolution increases to be focused ________, both at the meso- and global scales.
near the ground
75
True or False:
Some locally run models give users the option of setting many parameters, including the number and placement of vertical levels.
True
76
```
When setting up a local configuration, it is important to consider which of the following for layer distribution: (Choose all that apply)
A) Phenomena of interest
B) Variations in layer thickness
C) Terrain
D) Computer resources
E) Horizontal resolution
F) Limitations to physical equations
G) Source of boundary conditions
H) Time Step
```
A, B, D, E, G, & H
77
Fill in the blank.
Unlike the horizontal structure of models where discrete or
continuous (gridpoint or spectral) configurations can be used,
virtually all operational models use _________vertical structures.
discrete
78
True or False.
Operational models produce forecasts on the surfaces themselves, not for the average over an atmospheric layer between the vertical-coordinate surfaces.
False. They produce forecasts over the average, not on the surfaces themselves.
79
Fill in the blank.
In choosing a vertical coordinate system for a numerical model, the coordinate must either continuously __________ or continuously ______ in the vertical. In other words, the coordinate must exhibit __________ behavior with height.
- decrease
- increase
- monotonic
80
What is an advantage of using sigma coordinates (rather than pressure or height) for the vertical coordinate system in a model?
Using sigma coordinates avoids complications that arise when the pressure or height surfaces intersect the ground, especially in mountainous areas.
81
What is an advantage of using the eta rather than the sigma coordinate for the vertical coordinate system?
The eta coordinate improves the calculation of winds and vertical motion in areas of steep terrain.
82
What is an advantage of using isentropic coordinates for the vertical coordinate system?
It improves forecasts of fine-scale processes near fronts and jet streams.
83
What is a disadvantage of using isentropic coordinates for the vertical coordinate system?
It introduces difficulties near the earth's surface.
84
Fill in the blank.
To address the problem of discontinous forecast surfaces, Phillips (1957) developed a terrain-following coordinate system called the ________ coordinate.
Sigma
85
In its simplest form, how is the sigma coordinate defined?
sigma = p/p(s), where p is the pressure on a forecast level within the model and p(s) is the pressure at the earth's surface, not the mean sea level pressure.
86
Fill in the blanks.
For sigma coordinates, the lowest coordinate surface, where sigma = __________, follows a smoothed version of the actual terrain. The top coordinate is usually labeled sigma = __________, between 25 and 1 hPa.
1, 0
87
Name 4 advantages of using sigma coordinates.
1) it produces relatively simple formulations for handling the lower boundary
2) It conforms to naturally sloping terrain.
3) The terrain-following nature of the sigma coordinate lends itself to increasing vertical resolution near the ground consistently over the full model domain.
4) surface doesn't intersect the ground
88
Name 4 disadvantages of using sigma coordinates.
1) PGF is affected by sloping surfaces in sigma coordinates.
2) Often misrepresent the true surface elevation of mountains because of smoothing techniques.
3) land points in the model can be forced to extend beyond the true coastline due to smoothing effects
4) Sigma models can have difficulty dealing with weather events in the lee of mountains
89
Fill in the blank.
The eta coordinate (η) was created in the early 1980s in
an effort to reduce the errors incurred in calculating the
_____________ using sigma coordinate models.
pressure gradient force
90
What is the eta coordinate sometimes referred to as?
the step-mountain coordinate
91
As opposed to the sigma coordinate system, what does the eta coordinate system allow the bottom atmospheric layer of the model to be represented as?
A flat "step" within each grid box
92
Since the eta coordinate's representation of terrain is a source of error in areas strongly affected by small-scale terrain features, is it still necessary to depict the average elevation within the entire grid box area? (Yes or No)
Yes
93
Name 3 advantages of the Eta coordinate system.
1) Eta models do not need to perform the vertical interpolations that are necessary to calculate the PGF in sigma models
2) the low-level convergence in areas of steep terrain are far more representative of real atmospheric conditions than in the simpler formulations in sigma models
3) Compared with sigma models, eta models can often improve forecasts of cold air outbreaks, damming events, and leeside cyclogenesis
94
Name 5 limitations of using the Eta coordinate system.
1) The step nature of the eta coordinate makes it difficult to retain detailed vertical structure in the boundary layer over the entire model domain
2) Eta models do not accurately depict gradually sloping terrain.
3) Eta models have difficulty predicting extreme downslope wind events.
4) Eta models must broaden valleys a few grid boxes across or fill them in.
5) Eta coordinates can create spurious waves at step edges.
95
For what reasons is the potential temperature alone not
currently used as a vertical coordinate in any operational
numerical model system?
Because non-adiabatic processes dominate in the
boundary layer and isentropic surfaces intersect the
earth's surface.
96
Name 4 advantages of using isentropic coordinates.
1) The theta coordinate allows for more vertical resolution in the vicinity of baroclinic regions, such as fronts, and near the tropopause.
2) For adiabatic motion, air flows along constant theta (isentropic) surfaces and implicitly includes both horizontal and vertical displacement.
3) Vertical motion through isentropic surfaces is caused almost exclusively by diabatic heating.
4) Isentropic coordinate models conserve important dynamical quantities, such as potential vorticity.
97
Where do the primary limitations of isentropic coordinates occur?
Why?
- in the boundary layer
| - because the flow is strongly non-adiabatic
98
Name 3 limitations of isentropic coordinates.
1) Isentropic surfaces intersect the ground.
2) Isentropic coordinates may not exhibit monotonic behavior with height, especially in the boundary layer.
3) Vertical resolution in nearly adiabatic layers is coarse.
99
What are 2 primary objectives for the vertical coordinate system.
1) Should preserve conservative atmospheric properties and treat important dynamical processes accurately, such as adiabatic and diabatic motion and flow over terrain
2) Should accurately represent the pressure gradient force (PGF, used for calculating the geostrophic wind) over both flat and sloping terrain
100
Assume that you've developed and implemented a local model using the eta vertical coordinate to replace a sigma coordinate model. Your area of forecast responsibility has two regimes - nearly flat plains to your west and a high mountain plateau to your east. You want to pass on two key points to your model output users.
Answer the following questions by choosing the best answer in parentheses.
1) Remember that the (horizontal pressure gradient/boundary-layer resolution/horizontal temperature gradient) will not be as detailed over the mountains as over the plains.
2) Remember that the (horizontal pressure gradient/boundary layer/vertical velocity field) will not be as detailed over the mountains as over the plains.
1) boundary-layer resolution
| 2) horizontal pressure gradient
101
The GFS and NAM use what type of hybrid coordinate system?
| This system has ________ surfaces near the ground transitioning to _______surfaces near the top.
σ-p hybrid coordinate system
- sigma
- pressure
102
Fill in the blanks.
Hybrid sigma-pressure coordinates takes advantage of the terrain-following sigma in the boundary layer while utilizing flatter coordinates which have better numerical properties aloft and improves the efficiency and accuracy of __________ ___________calculations used in assimilating _______ radiance observations.
- radiative transfer
| - satellite
103
List 4 advantages of hybrid sigma-pressure coordinates.
1) In the upper troposphere where pressure gradients are often strongest, this system avoids the numerical calculation difficulties of sigma coordinates over steep terrain.
2) This system allows better use of satellite radiance observations than only using sigma coordinates
3) This system represents surface heating and dynamical mixing in the boundary layer well.
4) he system allows good surface physics interactions, including surface evaporation and treatment of snow cover.
104
List 4 limitations of hybrid sigma-pressure coordinates.
1) In the lower troposphere, even extending into the middle troposphere in some instances, the pressure gradient force calculation errors which sigma coordinates create also exist in this hybrid system.
2) The smoothing of terrain required for sigma coordinates is still required, though perhaps not as much smoothing is needed
3) The excessive downsloping and too-rapid lee cyclogenesis of sigma coordinates carries over to this hybrid system
4) It can be difficult to blend coordinate types at their interfaces.
105
Fill in the blanks.
Hybrid isentropic-sigma coordinate models have a combination of _______ layers at the bottom that shift to _________layers above.
- sigma
| - isentropic
106
Fill in the blanks.
Uniting theta and sigma into one vertical coordinate system combines the terrain-following advantages of sigma and the increased vertical resolution in key _________ areas due to the adaptive nature of _________ surfaces.
- baroclinic
| - isentropic
107
List 4 advantages of hybrid isentropic-sigma coordinates.
1) This system retains the advantages of isentropic models in the free atmosphere, including better precipitation starting times for isentropic upglide (warm advection) than in sigma-coordinate models.
2) This system eliminates the problem of isentropic surfaces intersecting the ground.
3) This system represents surface heating and dynamical mixing in the boundary layer well.
4) The system allows good surface physics interactions, including surface evaporation and treatment of snow cover.
108
List 3 limitations to hybrid isentropic-sigma coordinates.
1) Hybrid isentropic-sigma models no longer preserve adiabatic flow in the boundary layer as easily as pure isentropic models.
2) The depth of the sigma layers does not match the true depth of the PBL, so processes near the PBL/free atmosphere interface may not be depicted with the best coordinate.
3) It can be difficult to blend coordinate types at their interfaces.
109
True or False.
The requirement that nonhydrostatic models solve a
prognostic vertical motion equation constrains the choice of
vertical coordinate and increases computation time
True
110
Choose the best answer.
Most nonhydrostatic models use a vertical coordinate based on
(pressure/height/sigma/eta/isentropic/sigma-isobaric/isentropic-sigma).
height
111
Choose the best answer.
Some nonhydrostatic forecast models and locally run models sacrifice (vertical/horizontal) resolution in order to run the models in real time at fine (vertical/horizontal) resolution.
- vertical
| - horizontal
112
True or False.
| The ratio of vertical to horizontal resolution is typically rather good.
False. It's typically poor.
113
Fill in the blanks.
The slope of features, such as baroclinic zones, cannot be well
represented in high-resolution non-hydrostatic models because the fine horizontal resolution anchors the ________ ______ while the vertical location is subject to large ______-_______
________.
- horizontal location
| - finite-difference error
114
Does the inconsistency between the horizontal/vertical resolution ratio introduce numerical noise into the forecast and reduce the advantages of nonhydrostatic models in predicting baroclinic systems? (Yes or No)
Yes
115
Match each vertical coordinate system to its primary advantage in NWP models for depicting weather.
a) sigma
b) sigma-pressure hybrid
c) isentropic
i) surfaces are terrain-following and thus resolve the boundary layer well
ii) helps assimilation of satellite radiance observations
iii) naturally increases vertical resolution near fronts and jet streaks
a) --> i)
b) --> ii)
c) --> iii)
116
Match each vertical coordinate system to its primary disadvantage in NWP models for depicting weather.
a) sigma
b) sigma-pressure hybrid
c) isentropic
i) May not correctly portray weather events in lee of mountains
ii) Not allowed to represent superadiabatic conditions in the BL
iii) May not represent boundary layer with sufficient resolution over elevated terrain
a) --> i)
b) --> i)
c) --> ii)
117
What must the vertical resolution of operational models be sufficient enough to do?
– Incorporate the effects of diurnal heating and cooling
– Incorporate local effects of spatially variable surface characteristics
– Depict flow and shear in the boundary layer
– Capture ageostrophic regimes associated with upper-tropospheric jetstreaks
– Detect interactions between the stratosphere and troposphere, including multiple high-level jets
– Monitor stratospheric regimes that affect medium-range forecasts and trace gas concentrations
118
Even with near error-free observations and a
“perfect” model, will forecast errors will grow with
time?
Yes, bitch.
119
True or False.
| The real and “modeled” atmosphere will always be different and will always diverge with time.
True, you stupid motherfucker.
120
How often does error growth in a model double?
Every 2-3 days.
121
True or False.
NWP models can resolve weather features and/or
processes that occur within a single model grid box.
False
122
The method of accounting for such effects without directly forecasting them is called what?
parameterization
123
Fill in the blank.
| ___________ refers to the link between the assumptions in the parameterization and the forecast variables.
Closure
124
List 3 types of assumptions that are used to "create" information for parameterization.
1) Empirical/Statistical
2) Dynamical/thermodynamical constraining assumption
3) Model within a model
125
From which two things can problems associated with using parameterizations result?
1) Interactions between parameterization schemes
| 2) The increasing complexity and interconnectedness of parameterizations
126
True or False.
More sophisticated schemes and finer resolution will lead to more realistic-looking forecast detail but also more complicated model error characteristics.
True
127
True or False.
The increasing complexity of model error characteristics will result in lesser reliance on model diagnostics to make adjustments to the model forecast fields.
False. ...will lead to greater reliance...
128
True or False.
Model changes will take longer to develop and test because changes in one parameterization affect the behavior of other parameterizations through a complex web of interactions.
True
129
True or False.
Operational model changes will continue to be released in bundles, rather than individually, because of the need to test complex interactions together.
True
130
True or False.
As model skill improves and model phenomena begins to appear more realistic, model output will not require human interpretation and adjustment.
False. ...will still require human interpretation...
131
True or False.
The improved simulation of natural detail important to atmospheric processes leads to lesser forecast sensitivity to physical parameters whose values are poorly or not at all known.
False. ...leads to greater forecast sensitivity..
132
Which of the following statements about hydrostatic and nonhydrostatic models are true?
A) Hydrostatic models only diagnose vertical motion fields and can only infer vertical motions.
B) Nonhydrostatic models are generally applied to forecast problems requiring very high horizontal resolution (from tens of meters to a few kilometers).
C) Hydrostatic models can explicitly forecast vertical motion and can be used effectively to forecast motions in deep convection.
D) Hydrostatic models use only gridpoint formulations.
E) Nonhydrostatic models can explicitly forecast vertical motion and can be used effectively to forecast motions in deep convection.
A, B, & E
133
For each of the phenomena listed below, indicate whether a hydrostatic model can make a good prediction or whether the feature requires a nonhydrostatic model for good prediction.
A) Cold front
B) Boundary-layer roll.
C) Mesoscale circulations associated with a convective complex.
D) Pattern of mountain waves in vertical cross section.
E) Sea breeze.
```
A) Hydrostatic
B) Non-hydrostatic
C) Hydrostatic
D) Non-hydrostatic
E)Hydrostatic
```
134
Choose the correct answer in parentheses.
For dynamic features (e.g., not driven by sharp topography or land-sea contrast, but by internal atmospheric processes), gridpoint models (omit/include but poorly represent) features too small to predict accurately while spectral models (omit/include but poorly represent) features too small to predict accurately.
- include but poorly represent
| - omit
135
Select the items which are advantages of using a sigma vertical coordinate or a hybrid coordinate which has sigma coordinates at the bottom of the model.
A) High vertical resolution near the surface
B) Avoids coordinate intersecting the ground
C) Downslope winds are well represented
D) Good resolution of sloping frontal zones
E) Cold-air damming is well represented
A, B, & C
136
What minimum number of grid points should the size of a meteorological feature span in order to be adequately forecast in a gridpoint model?
A) 2 to 3
B) 3 to 5
C) 5 to 7
D) 7 to 9
C
137
Choose all that apply.
Which of the following introduce error into a model forecast if the model were to magically start with perfect initial conditions and had perfect representation of all physical processes such as radiation, surface energy exchange, and microphysics?
A) Breaking up forecast variables into layer averages
B) Convective initiation
C) Lateral boundary conditions if the model is not global in coverage
D) Use of grid boxes or a limited number of wave functions
E) Approximations to the equations of motion
F) Bad observations
A, C, D, & E
138
Choose all that apply.
Which of the following describe how boundary conditions affect a limited-area model forecast?
A) The influence of the lateral boundary conditions depends strongly on the vertical resolution and vertical coordinate type in the limited-area model
B) The resolution and quality of the larger-domain forecast supplying lateral boundary conditions affects the forecast quality of the limited-area model
C) It depends on whether the limited-area model is gridpoint or spectral
D) The forecast of surface sensible weather (2-m temperature, 10-m wind, etc.) is strongly affected by parameterizations used to prescribe lower-boundary conditions
E) The influence of lateral boundary conditions depends on the time into the forecast and the distance from your local area of interest to the model domain edge
F) Lateral boundary conditions affect the entire forecast area from the initial time
B, D, & E
139
Choose all that apply.
A model forecast of diurnal boundary layer evolution over flat terrain near a water body can be strongly affected by
A) Model radiation and surface physics parameterizations
B) Vertical resolution in the middle and upper troposphere
C) Whether the model is hydrostatic or nonhydrostatic
D) Data used to specify the water temperature
E) Horizontal resolution
A, D, & E
140
Choose all that apply.
Which of the following are effects of inadequate model terrain on weather elements?
A) Inability to depict downslope winds, valley winds, drainage winds, and other small-scale processes
B) Difficulty in resolving and representing valley inversions and cold air damming
C) Shifting vertical motion maxima/minima away from the mountains due to insufficient terrain slope
D) Inaccuracies in forecasting the strength and location of the upper-level jet
A, B, & C
141
Choose all that apply.
Select the items which are disadvantages of using a sigma vertical coordinate or a hybrid coordinate which has sigma coordinates at the bottom of the model. Select all applicable choices.
A) Calculation of pressure gradient force over steeply sloping terrain
B) Calculation of pressure gradient force over flat terrain
C) Cold air damming is poorly represented
D) Downslope winds are poorly represented
E) Lee cyclogenesis is too strong or occurs too soon
A, C, & E
142
What are 4 major assumptions that affect data analysis?
1) Statistical assumptions
2) Assumed observation error
3) Assumed background error
4) Assumed balance constraint
143
What are 3 adaptive analysis methods?
1) Anisotropic Covariance
2) 4D-Var
3) Ensemble Kalman Filter
144
What are some data use limitations in data analysis?
- soundings
- aircraft cruising level
- surface observations
- satellite mass observations
- satellite wind observations
- cloud, precipitation data
- high resolution observations
145
Fill in the blanks.
The __________ ____________ procedure moves and merges the observation increments at observation times and locations to the grid fields of the model forecast initial conditions (on the model grid).
- objective analysis
146
True or False.
The basic meteorological assumptions underlying the statistics of data analysis profoundly shape the analysis and its handling of data and determine when the analysis will have problems.
True
147
The 3D-VAR tries to find a balancing point between what two things?
The analysis-observations differences and the analysis changes from the background
148
The balancing point used in 3D-VAR is found by assessing a penalty to the analysis for differing from each piece of observational and model data. Name 2 penalties that are assessed.
A penalty is charged for deviations from the observations and a penalty is charged for deviations from the background.
149
What is the primary limitation of standard 3D-VAR?
It spreads the influence of observations in the vertical and horizontal the same in every weather situation, regardless of the presence of fronts, stable layers, vortices, dry lines, or any other features.
150
What does anisotropic mean?
Not the same in all directions.
151
“Anisotropic background error covariances,” an expression commonly used by NCEP, refers to what?
a different set of assumptions that control the pattern of influence an observation increment can have on the analysis.
152
What does 4D-VAR do to 3D-VAR?
It extends it into the time dimension.
153
What are two (interrelated) limitations of 4D-VAR?
It requires an enormous amount of computer power and therefore it is often run at coarser resolution than the model.
154
In what adaptive analysis method are the covariance patterns statistically estimated using ensemble forecasts?
Ensemble Kalman Filter
155
True or False.
A Kalman filter cannot determine the covariances as part of the analysis itself based on the observations, even when the observations themselves have errors
False. It CAN determine the covariances...
156
Fill in the blanks.
A clever method for handling quality control is to not reject observations outright, but instead to ________ _________ after each iteration in the analysis.
reevaluate outliers
157
Tuning of the analysis is performed to do what?
Optimize forecast performance
158
Which of the following statements are true regarding tuning in data analysis?
1) It does not affect the different handling of different data sources for the same variable (such as aircraft temperatures, temperatures from satellite radiances, radiosonde temperatures, and surface temperatures);
2) It does affect the fundamental limitations of the analysis process, including the assumptions in the error statistics used;
3) involves setting parameters based on model performance statistics and major tuning changes only occur with major model implementations.
1) True
2) False ...It does NOT affect the fundamental limitations...
3) True
159
Tuning comes in the form of multipliers in the cost function so that which of the following may be changed?
A) the influence of all the observations compared to the background
B) the influence of all the model forecasts compared to the background
C) the degree to which the balance constraint is enforced;
D) the horizontal and vertical distance of influence spreading
E) the influence of statistical treatment of the observation
A, C, & D
160
What are some operational tips regarding data analysis?
1) be cautious when judging the quality of a model analysis
2) Be aware of a data void history
3) The analysis is based on the assumption that the first guess is good, even though there may be a bad first guess
4) Good data may get rejected
5) Analysis assumptions may be violated
6) The model may change (it may be updated)
