Test 1 Flashcards
What are water droplets found in temperatures below freezing referred to as?
supercooled
What are regions of a cloud transformed to ice crystals, where the cloud is saturated with respect to ice?
glaciated
True or False.
In mixed-phase clouds, the transition of supercooled liquid to ice generally takes places rapidly and tends to begin in the highest (coldest) part of the cloud, where ice is nucleated, and then work downward.
True.
Which of the following statements are true of homogeneous nucleation within clouds?
A. It takes place at relatively warm temperatures.
B. It takes place at very cold temperatures.
C. It does not requires ice forming nuclei.
D. It is vulnerable to thermal agitation, which can reduce the chances of it occurring.
E. It is the prevalent process in cloud ice nucleation.
B, C, and D
Which of the following statements are true of heterogeneous nucleation within clouds?
A. It does not require ice forming nuclei.
B. It requires ice forming nuclei.
C. It is the prevalent process in cloud ice nucleation.
D. It is the least prevalent process in cloud ice nucleation.
E. It takes place by deposition, contact, or freezing processes.
F. It takes place by freezing, sublimation, or condensation processes.
B, C, and E
True or False.
The concentration of active ice-forming nuclei in clouds increase as the cloud temperature drops.
True.
The number of active ice forming nuclei decreases with increasing relative humidity causing heterogeneous nucleation to occur more frequently in the coldest part of the cloud near the cloud top.
False.
Once an ice crystal has formed, it can grow through which of the following processes?
A. Aggregation B. Nucleation C. Sublimation D. Accretion E. Diffusion deposition F. Condensation
A, D, and E
This process occurs due to differences in the saturation vapor pressure between ice and liquid water. At a given temperature, the vapor pressure over a water surface is greater than that over an ice surface. As a result, a vapor pressure gradient develops between the droplets and crystals and water vapor moves from the higher pressure surrounding the droplets to the lower pressure surrounding the crystals, resulting in crystal growth at the droplets’ expense.
A. Aggregation B. Nucleation C. Sublimation D. Accretion E. Diffusion deposition F. Condensation
E
In the diffusion deposition ice growth process, the optimal ice crystal growth rates occur around ______ degrees C.
A. -5 B. -10 C. -15 D. -20 E. -40
C
In this ice formation process, ice crystals grow via collision with supercooled droplets. The supercooled droplet freezes on contact and sticks to the original ice crystal to form rime ice. This process is optimal in saturated layers with temperatures of 0 to -10 degrees C.
A. Aggregation B. Nucleation C. Sublimation D. Accretion E. Diffusion deposition F. Condensation
D
Graupel or snow pellets are primarily formed by which of the following processes?
A. Aggregation B. Nucleation C. Sublimation D. Accretion E. Diffusion deposition F. Condensation
D
In this process ice crystals grow through collision with each other. Liquid molecules on the outer surface of the crystals serve to increase bonding between two colliding crystals. This process is maximized at or near 0 degrees C.
A. Aggregation B. Nucleation C. Sublimation D. Accretion E. Diffusion deposition F. Condensation
A
Crystal habits that are dendritic are most favored at cloud temperatures between ___________ degrees C. If these temperatures are present in a cloud, the potential for subsequent ___________ is greatest.
-12 and -16
heavy snowfall
Observation and laboratory experiments indicate that the optimal conditions for ice crystal initiation and growth are in cloud layer that are saturated with respect to ___________ and thus supersaturated with respect to ____________, with temperatures in the __________ degrees C range.
liquid water
ice
-10 to -18
Aircraft icing potential is greatest within clouds with temperatures between ________ degrees C.
A. 0 and -15 B. -10 and -20 C. -20 and -30 D. -30 and -40 E. -40 and colder
A
In GOES 3.9 micrometer imagery, lower clouds (stratus or stratocumulus) containing water droplets appear _________, while the higher clouds (cirrus) containing ice particles appear __________.
white
dark
True or False.
In a cold layer of a sounding in a marine environment, the coldest temperature in the saturated upper cold layer is -9 degrees C. Ice crystals are not likely to exist in this layer.
False
In the surface-based cold layer in a typical wintertime precipitation scenario, the warmest portion is nearly saturated and contains T = ~+1.0 degrees C for a depth of about 200 meters. If frozen hydrometeors are entering this cold layer from above, which is the most likely phase of the precipitation?
A. Liquid
B. Freezing
C. Frozen
C
What are the 3 primary processes in the atmosphere that always directly involve latent cooling?
A. Turbulence B. Melting C. Convection D. Evaporation E. Sublimation
C, D, and E
For a cloud depth of about 800 meters, what would be the most likely precipitation type and/or rate?
A. Moderate snow
B. Drizzle or freezing drizzle
C. Moderate rain
D. Rain showers
B
What would be an appropriate rain/snow thickness (1000-500 mb) threshold for a location at 1500 m (4921 ft)?
A. A value somewhat greater than 2840 meters.
B. A value somewhat greater less than 5400 meters.
C. A value somewhat greater than 5400 meters.
D. A value somewhat less than 2840 meters.
C
What are some of the important parameters utilized by model precipitation type algorithm approaches such as Bourgouin, Baldwin, Czys, and Ramer?
A. Skin or surface temperature
B. Climatology of sounding and the associated precipitation types
C. Wet-bulb temperature profile
D. Residency time of hydrometeors in warm regions of a sounding
E. Positive (> 0 degrees C) and negative ( 0 degrees C) layers in the sounding
All
Which of the following are reasons that analyses based on surface observations alone should not be used to assess model initial conditions?
A. The spacing between the stations is irregular.
B. Similar instruments are used for different observational platforms.
C. Instruments give representative information for a model grid box.
D. Instruments have systematic observational bias.
A and D
You have a sounding from a radiosonde equipped with a Sippican sensor that indicates a moist layer with a base at about 15,000 feet above ground level and the temperature at that level is -31 deg C. A model sounding from an analysis valid at the same time shows the base of the moist layer several hundred feet higher that that of the radiosonde. Which of the following statements is lost likely to be true with respect to the base of the actual moist layer?
A. The base of the moist layer may be correctly placed in both.
B. The base of the moist layer is correct in the model analysis.
C. The base of the moist layer is too low int eh model analysis.
D. The base of the moist layer is too high in the model analysis.
D.
There was a cluster of thunderstorms affecting part of your immediate area at the time of the most recent model analysis available. The model has 12-km resolution, uses a convective parameterization, does not assimilate radar data, and has predicted cloud water for its grid-scale precipitation parameterization. How will the model analysis depict the thunderstorms?
A. The thunderstorms will be accurately placed in the model analysis.
B. The precipitation will be accurately placed in the model analysis.
C. The cold outflow boundary will be accurately placed in the model analysis.
D. None of the above.
D.
You are checking the analysis accuracy of a 40-km global model. Based on the model resolution, what would you expect to see depicted in it?
A. A synoptic scale short wave trough
B. Acoustic compression waves
C. A jet streak about 800-km long and 200-km wide
D. Temperature and moisture profiles form within a convective storm
A and C
You are an operational forecaster in the Midwest during the cold season. A low pressure system is approaching from the southwest and is expected to affect your area. Warmer, moist air is beginning to overrun your area in advance of a short-wave trough at the middle levels of the troposphere. What will be plausible problems of the day given this conceptual model of the atmosphere?
A. Precipitation timing
B. Surface temperature
C. Vertical temperature structure
D. Precipitation type
A, B, C, and D
You are an operational forecaster in the Midwest during the cold season. A low pressure system is approaching from the southwest and is expected to affect your area. Warmer, moist air is beginning to overrun your area in advance of a short-wave trough at the middle levels of the troposphere. What is the predominant scale of the problem of the day?
A. Microscale B. Synoptic scale C. Mesoscale D. Planetary scale E. Grayscale
B
You are an operational forecaster in the Midwest during the cold season. A low pressure system is approaching from the southwest and is expected to affect your area. Warmer, moist air is beginning to overrun your area in advance of a short-wave trough at the middle levels of the troposphere. Which would be the most appropriate tool(s) to use in analyzing the initial conditions of the current forecast?
A. Ground-based temperature profilers versus model sounding
B. Potential vorticity analysis compared to water vapor imagery
C. Radiosonde compared to model-analyzed 850-hPa temperature field
D. Mixed-layer lifted index compared to water vapor imagery
A, B, and C
Why should forecasters consider all elements in the first 24 hours of a forecast to have high impact for customers and partners?
A. Forecasters cannot fully assess all customer needs at any given time and must assume all elements are high impact.
B. All forecast elements have to potential to be high impact to a diverse set of customers and users of our products.
C. All elements should NOT be considered high impact. Only watches, warnings and advisories are high impact.
D. It is easy to assess our customer’s needs, and we can create a customized forecast for each one.
A and B
Why are analysis and diagnosis important components of evaluating NWP?
A. Forecasters can ensure the continuity between NWP and official forecasts.
B. Forecasters can focus on the impacts of severe weather events that are important to customers.
C. Forecasters can improve the accuracy of the forecast by eliminating implausible outcomes.
D. Forecasters can predict the weather without being distracted by the numerous concerns of customers.
C.
Which of the following statements describes a limitation of analysis and diagnosis?
A. The chaotic nature of the atmosphere prevents the application of systematic methodologies.
B. Human forecasters are prone to misinterpret NWP model guidance.
C. NWP models contain errors that grow with increasing lead time
D. The ability of human forecasters to improve NWP forecasts decreases with longer lead times.
D.
You run a construction company. One of your current projects is to pour a concrete foundation. You will need at least six hours without precipitation in order to get the job done. It is early in the morning, and you are looking at today’s forecast as you decide whether to pour the foundation today. Which of the following forecasts would be more helpful in making your decision?
A. Forecast 1:
TODAY…Skies will be partly cloudy with scattered showers and possibly thundershowers. Rain heavy at times. Chance of precipitation is 40%.
B. Forecast 2:
TODAY…Mostly clear this morning…then partly cloudy. Scattered showers likely after 3pm. Rain may be heavy at times when showers begin.
B
Below is a list of steps in the forecasting methodology. Match each with it’s definition.
i. Determine plausible outcomes
ii. Update the forecast
iii. Continuous MetWatch
iv. Diagnose cause and effect
a. Chance the forecast to reflect current thinking about the future state of the atmosphere.
b. Determine what changes to the forecast are appropriate for the situation.
c. Ongoing watch of the weather to gain insight into possible data trends.
d. Determine the reason that the actual weather departs from the forecast.
a. ii
b. i
c. iii
d. iv
When using analysis and diagnosis, how often should we update the forecast?
A. Upon a request by customers.
B. When current weather events require it.
C. Regular morning and afternoon updates.
D. Upon receiving new model information.
B.
What are some regional model examples?
RAP, NAM, WRF, HWRF
What are some global model examples?
GFS, GEN, UKMET, ECMWF
What equations are models based on?
Certain physical laws of motion and conservation of energy such as Newton’s Second Law of Motion and the First Law of Thermodynamics
What are the two general types of model architecture?
Grid point and spectral models
What is the fundamental difference between grid point and spectral models?
The two types formulate and solve the primitive equations differently, leading to different answers.
Grid point models represent data at discrete, fixed grid points, whereas spectral models use continuous wave functions.
True or False.
The characteristics of each model type alone with the physical and dynamic approximations in the equations influence the type and scale of features that a model may be able to resolve.
True
True or False.
Grid point and spectral models are based on different sets of equations.
False.
Does model type influence a model’s domain?
No.
What type of model have global models historically been? How and why is that changing?
Spectral
Changing to grid point as computing power increases
Which of the following are affected by model type?
A. How the model equations are solved
B. How the data are represented
C. The size of the model’s domain
D. The model’s horizontal and vertical resolution
E. The type and scale of weather features that can be represented
A, B, D, and E
How can we mathematically represent NWP in words in its simplest form?
The change in forecast variable A during the time period t is equal to the cumulative effects of all processes that force A to change.
How are future values of meteorological variables solved in NWP?
By finding their initial values and then adding the physical forcing that acts on teh variables over the time period of the forecast.
What are the “primitive equations”?
The specific forecast equations sued in NWP models
What do the primitive equations govern?
The motion and thermodynamic changes that occur in the atmosphere
How are the primitive equations solved to be interpreted by the models?
Algebraic approximations
True or False.
Numerical approximations introduce error even when the forecast equations completely describe the phenomenon of interest and even if the initial state were perfectly represented.
True.
In what framework are the governing equations of models written?
Eulerian
What coordinate system are the governing equations of models written?
Pressure
What terms have been left out of the governing equations?
What terms have been simplified to one term instead of many?
Curvature
Friction and diabatic heating
What are the seven equations used in NWP?
Wind Forecast Equations Continuity Equation Temp Forecast Equation Moisture Forecast Equation Hydrostatic Equation Prognostic/Diagnostic Equation Physical Processes
How are derivatives in the forecast equations in grid point models approximated?
Using finite differences
How do grid point models represent information?
In three-dimensional cubes
In a three-dimensional cube created by a grid point model, where is thermodynamic information stored? Where is wind and flux information stored?
The center
Winds are on the faces of the cube, and associated flux information into and out of the cube
How are derivatives in the forecast equations in spectral models approximated?
They aren’t. Derivatives of waves are waves.
How do spectral models transform dynamics calculations? Physical?
Spectrally
Grid point
How are spectral transformations felt in model output?
In the long-range
What does a hydrostatic model account for?
Buoyancy
What doesn’t a hydrostatic model account for?
Perturbation pressure acting against buoyancy
Previous vertical motion
Water loading
What does a nonhydrostatic model account for?
Buoyancy
Perturbation pressure acting against buoyancy
Previous vertical motion
Water loading
When is a hydrostatic model sufficient?
Phenomena that have a longer horizontal length than a vertical depth
What weather phenomena are accurately depicted by the hydrostatic model?
Sea breeze Broad, gentle mountain waves Hurricane mean radial circulation MCC non-convective elements Weak to moderate diabatic forcing Frontal circulation Microphysics independent of dynamics Gravity waves existence
What weather phenomena do you need a nonhydrostatic model to predict?
Boundary layer rolls Steep mountain waves Hurricane eyewall MCC convective elements Very strong, focused latent heating Rope cloud along front Microphysics feedback is important Gravity wave propogation and ducting
What grid spacing limit is required for a nonhydrostatic model?
A few km or fewer
What are changes in the vertical motion in a non-hydrostatic model caused by?
Orographic uplift and descent
Advection bringing in air with a different vertical velocity
Changes in horizontal convergence/divergence affecting hydrostatic balance
Phenomena with nonhydrostatic pressure perturbations such as thunderstorms
Warm temperature anomalies suggesting buoyancy
Higher moisture content suggesting buoyancy
Water loading
What characteristics of the model forecast equations limit the accuracy of the forecast?
A. They have approximations in the physics terms.
B. Approximations are used in deriving the forecast equations.
C. They cannot be solved accurately in either spectral or grid point models at any resolution.
D. The equations contain complex terms for which initial values cannot be determined accurately.
A and B
The use of either grid point or spectral models in NWP models make it possible to…
A. Solve the model equations without producing errors.
B. Produce mathematical representation of the full atmosphere.
C. Completely represent all details of the atmosphere.
D. Derive and solve the model equations using a mathematical framework.
B and D
Spectral models use (grid box/wavelength/continuous wave function/finite differencing) gradients to define meteorological fields.
Continuous wave function
Grid point models use (wave functions/discrete grid boxes/grid points/linear terms) to define meteorological fields.
Discrete grid boxes
(Spectral/grid point) models tend to have a better representation of global fields and gradients.
Spectral
(Spectral/grid point) models lend themselves better to limited-area applications and tend to have a better representation of the effect of physical processes on the evolution of the weather.
Grid point
(Hydrostatic/non-hydrostatic) models can explicitly forecast vertical motion, whereas (hydrostatic/non-hydrostatic) models only forecast vertical motion fields.
Non-hydrostatic
Hydrostatic
(Hydrostatic/non-hydrostatic) models are used especially for forecasting smaller-scale phenomena, such as convection.
Non-hydrostatic
(Hydrostatic/non-hydrostatic) models are used primarily over small domains, whereas (hydrostatic/non-hydrostatic) models are used in global or some regional models.
Non-hydrostatic
Hydrostatic
Which model is best for forecasting the following phenomena?
Precipitation patterns near complex terrain with topographic resolution coarser than 10 km.
(global spectral/regional grid point (hydrostatic)/high-resolution non-hydrostatic)
regional grid point (hydrostatic)
Which model is best for forecasting the following phenomena?
Planetary wave pattern for the next seven days.
(global spectral/regional gridpoint (hydrostatic)/high-resolution non-hydrostatic)
global spectral
Which model is best for forecasting the following phenomena?
Development and evolution of a mesoscale convective system.
(global spectral/regional gridpoint (hydrostatic)/high-resolution non-hydrostatic)
high-resolution non-hydrostatic
Which model is best for forecasting the following phenomena?
Outflow boundary propagation.
(global spectral/regional gridpoint (hydrostatic)/high-resolution non-hydrostatic)
high-resolution non-hydrostatic
Which model is best for forecasting the following phenomena?
24-hour boundary layer wind forecast.
(global spectral/regional gridpoint (hydrostatic)/high-resolution non-hydrostatic)
regional grid point (hydrostatic)
Which model is best for forecasting the following phenomena?
QPF for the next 5 days along the West Coast.
(global spectral/regional gridpoint (hydrostatic)/high-resolution non-hydrostatic)
global spectral
What must forecasters understand in order to accurately deviate from model forecasts?
Model construction and structure
Model interpretation
Model biases
Model limitations
What does NAM stand for?
North American Mesoscale
What does GFS stand for?
Global Forecast System
What does WW3 stand for?
Wave Watch III
What does SREF stand for?
Short Range Ensemble Forecast
What does RAP stand for?
Rapid Refresh Model
What does POLAR stand for?
Polar Ice Drift
What does GEFS stand for?
Global Ensemble Forecast System
What does NAEFS stand for?
North American Ensemble Forecast System
What does GFDL stand for?
Geophysical Fluid Dynamics Laboratory
What does HWRF stand for?
Hurricane Weather Research and Forecasting
What does HRW-NMM stand for?
High Resolution Window/Non-Hydrostatic, hybrid, vertical coordinate Mesoscale Model
What kind of model is the NAM?
Regional mesoscale data assimilation and forecast model based on the WRF
What kind of model is the WW3?
It solves the spectral actin density balance equation for wave number-direction spectra
What kind of model is the SREF?
A set of model runs
What kind of model is the GFS?
Global spectral data assimilation and forecast model
What kind of model is the RAP?
Uses a RAP configuration of the WRF model with an ARW core, and uses and hourly data assimilation core
What kind of model is POLAR?
Works on a sea ice analysis from satellite, sea ice modeling, and ice-atmosphere-ocean coupling.
Who runs the NAEFS?
Meteorological Service of Canada, National Meteorological Service of Mexico, and the U.S. National Weather Service
What are the sources of model error?
Errors in the initial conditions
Errors in Model
Intrinsic Predictability Limitations
Describe the three components involved in the data assimilation process.
Through which real world observations:
- Enter the model’s forecast cycles
- Provide a safeguard agains model error growth
- Contribute to the initial conditions for the next model run
What is the underlying assumption with data assimilation?
Observations are used to make SMALL corrections to a short-range forecast, which is assumed to be good.
What are three instances where a model would be a poor forecast tool?
When weather features are too small to be picked up by the model
When you are in a rapidly changing situation
When the data coverage is not uniform
What quality would you expect the temperature (aloft, not surface) analysis field to typically have?
A. Fair
B. Good
C. Poor
B
What quality would you expect the winds (aloft, not surface) analysis field to typically have?
A. Fair
B. Good
C. Poor
B
What quality would you expect the moisture (aloft, not surface) analysis field to typically have?
A. Fair
B. Good
C. Poor
A
After ingesting new high-quality data and generating a forecast, should a model’s analysis closely resemble a skilled hand analysis?
No.
What are some limitations of the observations put into a model?
The density of obs
How frequently obs are taken
Instrument errors
What does ECMWF stand for?
European Center for Medium Range Weather Forecasting
What does GEM stand for?
Global Environmental Multiscale Model
