Synoptic

The CFL condition states that a time step greater than about blank is needed for a 40 km resolution model to be numerically stable

10 minutes

What minimum number of grid points should the size of a meteorological feature span in order to be adequately forecast in a gridpoint model

5 to 7

Whats the difference between an analysis and forecast?

Analysis consists of the observed and model conditions at present or past times. A forecast is based on initial conditions or observations for predicting future conditions.

Why is ensemble forecasting needed

Because of chaos, climate forecasters have to resort to something called 'ensemble forecasting' which means that we need to repeat the model runs with slightly different initial conditions many times and use averages and other statistical quantities (e.g. standard deviation) to 'settle' on a forecast.

Clouds and rain are associated with CVA or AVA

CVA

blank reproduce some realistic cloud processes, such as hydrometeor interactions and the effects of suspended hydrometeors on precipitation formation, while blank reproduce some liquid and ice precipitation generation processes, but can only predict a very limited range of circumstances and intensities.

Complex cloud schemes | simple cloud schemes

What are the Kuo Schemes triggers

Convection is triggered by any amount of CAPE and column-integrated moisture convergence exceeding a threshold value.

Which of the following statements regarding explicitly predicted convection are accurate?

Convective initiation is often poor when forcing is weak. Convective mode (e.g. isolated cells, bow echoes) is often well-predicted. Explicitly predicted convection with initial conditions coming from a coarser-resolution model is more likely to have a better forecast later rather than earlier in the forecast period.

In WRF, what does real.exe do

Create vertical model levels, Interpolate meteorological data to vertical model levels, Create input files for numerical integration (WRF)

You are forecasting for a location downstream of a weakening mesoscale convective complex (MCC). Model fields show development of a mid- to upper-level circulation center associated with the MCC propagating over your area within the next 24 hours, along with moderate-to-heavy precipitation amounts. There is no evidence in satellite and radar observations that a vortex exists, and no other features are evident to help focus or enhance the precipitation. What adjustments to the model forecast may be necessary?

Decrease cloud cover and increase daytime temperatures. Decrease forecast precipitation amounts

Assume that model output shows a lot of "grid-scale" precipitation and very little or no convective precipitation in a convective situation affecting your area of forecast responsibility. What adjustments might you have to make?

Decrease surface low intensity, Increase convective precipitation, Decrease grid-scale precipitation

List four advantages of ensemble forecasting.

Ensemble mean has more skill than individual members, Provides a quantitative measure of forecast confidence by lead time and location, Probabilistic forecast can easily be produced, Ensemble system tells us where model is not confident so we can use 'targeted observations' to improve forecasts

For convective parameterization the primary function is to forecast convective precipitation

False

Sigma coordinates dive into the ground when there are mountains.

False

Temperature is a suitable variable to use as a vertical coordinate.

False, because it needs to be monotonic, potential temperature.

Temperatures is a suitable variable to use as a vertical coordinate

False, because you can have the same temp at different heights.

Tomorrows weather will be the same as that of a typical Jan 27 is an example of persistence forecast.

False, climatology.

Since sigma coordinates are given by p/ps, sigma increases with height

False, decreases with height

The GFS is a limited area model

False, it is a global area model.

Vertical velocity is not a predicted variable non-hydrostatic model.

False, it is a predicted variable.

Isentrophic coordinates are based on temperature.

False, potential temperature.

Pressure coordinates are better than sigma coordinates for flow near the ground.

False, sigma are terrain following.

The shortest timestep allowed for a model with 30 km resolution and 100 m/s max wind speed is 10 minutes.

False, the CFL condition states that C is greater than or equal to dx over dy.

In a digging trough the jet streak is present to the east of the trough. A digging trough indicates strengthening and equatorward movement of the trough.

False, the jet streak is to the west.

The CFL condition establishes the minimum timestep that can be used for a given horizontal resolution.

False. It establishes the max timestep.

In general, which of the following has the most significant impact on forecasting precipitation location in large-scale models?

Initial and forecast moisture and vertical motions

What is the initial condition?

Initial state of the atmosphere at the beginning of the simulation.

What are three strategies that can be used to generate the different ensemble members in a forecast.

Introduce perturbations to initial conditions, Change model physical parameterizations, Combine results from different models into an ensemble.

List three processes that are usually parameterized.

Net (upward and downward) radiative fluxes at the TOA and surface, and internal heating rates, Treatment of absorption and scattering of solar and IR radiation by air molecules (O3, H2O, CO2,O2, some aerosols and other trace gases), Radiative transfer equation

what models predict vertical velocity.

Non-hydrostatic

At the surface, is cold air located to the north of the jet or south of the jet?

North

In WRF, what does wrf.exe do.

Numerically approximate the solutions to the model equations to produce a forecast. Wrf.exe is run for both idealized and real cases. Processing time varies based on parameters set in namelist.input and namelist.wps. Highly dependent on computing resources.

The first NWP model was performed by who using the equation in the year what?

Rossby, the absolute vorticity conservation principal in 1954

What is data assimilation?

SST, Surface type (land, ocean, forest, desert, ice, etc), Surface roughness length, Surface albedo, Soil moisture, Ozone mixing ratio, Orography and sub-grid variance of orography, Ozone mixing ratio

Which of the schemes is most effective for events involving advection of precipitation such as orographic or lake effect events?

Simple cloud schemes

All other things being equal, what general statements can be made about when the various precipitation schemes initiate precipitation reaching the ground relative to the correct time?

Simple cloud schemes are too early. Complex cloud schemes are nearest the correct time

At the surface, is warm air located to the north of the jet or the south of the jet?

South

The first operational numerical weather forecast was made in.

Sweden in 1954

What is the Arakawa-Schubert scheme

This is a complex scheme. It includes the effects of 1) moisture detrainment from convective clouds, 2) warming from environmental subsidence, and 3) convective stabilization in balance with the large-scale destabilization rate.

What is the Kuo Scheme?

This is a simple scheme that produces precipitation and increases static stability by emulating the moist-adiabatic ascent of a parcel. It adjusts the temperature and moisture profiles toward moist adiabatic.

What are Arakawa-Schuberts schemes triggers.

To trigger convection, the scheme requires some boundary-layer CAPE. Although it varies in specific implementations, the general formulation requires the presence of large-scale atmospheric destabilization with time.

For convective parameterization the primary function is to remove excess instability.

True

For convective parameterization they do not directly affect the vertical motion field.

True

For convective parameterization they produce precipitation as a by-product.

True

In a one-way interacting nested model the child grid does not affect the parent grid

True

Pressure is a suitable variable to use as a vertical coordinate

True

Richardson first weather forecast in 1922 calculated a change in pressure of 145 mb over a period of 6 hours. This unrealistic forecast forecast resulted from imbalances between the initial pressure and wind fields, and from violation of the CFL condition.

True

Sigma coordinates are terrain-following coordinates

True

Aliasing describes what happens when you sample a signal too infrequently.

True, you need more points for accuracy.

A non-hydrostatic model is required to study the eyewall of a hurricane.

True.

A spectral model represents the spatial variations of meteorological variables as a series of orthogonal functions called "basis functions".

True.

The WRF is a limited area model

True.

In WRF, what does the WPS do?

WPS is composed of geogrid (for geography data), ungrib (to extract the meterological data), and metgrid which prepares the geogrid and ungrib files for use in WRF, WPS is only necessary for real data cases, and is not needed for idealized cases

Wavelengths shorter than twice the size of the grid box will be 'seen' by the model as longer waves. This error/effect is called

aliasing

What is chaos?

chaos means that very small changes in the initial state of the ocean-atmosphere system can result in very large changes in the final result of the model simulation. It means sensitive dependency on initial conditions. Because of chaos both weather and climate forecasts are doomed to be probabilistic no matter how good the models, computers or data.

The primary purpose of microphysics schemes in NWP models is to simulate blank.

cloud and precipitation processes to remove excess atmospheric moisture directly resulting from model dynamics and physical parameterizations

The primary purpose of Convective Parameterization (CP) in NWP models is to simulate blank.

convective effects through the redistribution of temperature and moisture in a grid column, which reduces atmospheric instability

Numerical weather forecasts require knowledge of the initial conditions of the atmosphere. Initial conditions are usually a combination of observations from weather stations, satellites, radar, etc and previous runs of numerical models. The process for combining these observations together to create the model's initial conditions is called

data assimilation

AVA is associated with upward or downward motion.

downward motion

What is ensemble forecasting?

ensemble forecasts help to attack the chaos problem

The CFL condition requires smaller time steps for larger grid lengths.

false

Models that represent the spatial variations of meteorological variables on points of a pre-established grid are referred to as what models.

finite difference

The WRF is a what model.

finite difference

The GFS is a what model.

hydrostatic

For dynamic features (e.g., not driven by sharp topography or land-sea contrast, but by internal atmospheric processes), gridpoint models blank features too small to predict accurately while spectral models blank features too small to predict accurately.

include but poorly represent, omit

then is is apparent that the necessary and sufficient conditions for the rational solution of forecasting problems are knowledge of

initial conditions and governing equations

The model treatment of clouds, precipitation, radiation, turbulence and convection is known as

model physics

anticyclone vorticity is positive or negative?

negative

the sign of the vorticity in a SH cyclone is negative or positive

negative

The WRF is a what model.

non-hydrostatic

Cyclone vorticity is positive or negative?

positive

The sign of the vorticity in a NH cyclone is positive or negative

positive

Which of the following are true for pressure coordinates? pressure surfaces can go under the ground they follow the terrain they make the continuity equation very complicated all of the above

pressure surfaces can go under the ground

Which of the following vertical coordinates is best to simulate flow around mountains?

sigma coordinates

Models that represent the spatial variations of meteorological variables in terms of basis functions (e.g. trigonometric functions, Legendre polynomials) are referred to as what models.

spectral

The GFS is a what model

spectral

The Arakawa C-grid is a staggered grid

true

The smallest wavelength that a model can 'see' is twice the size of the grid box.

true

Violation of the CFL condition can result in large model errors and model crashes.

true

A spectral model represents the spatial variations of meteorological variables as a series of orthogonal functions called basis functions.

true, these waves help global models.

CVA is associated with upward or downward motion?

upward motion

Which of the following is true for a hydrostatic model? (Check all that apply) uses the hydrostatic approximation, vertical velocity is not a predicted variable, can be used to predict individual convective clouds, can be used to represent frontal systems, can be used to represent the sea-breeze, Can be used in a model with 3 km horizontal resolution, Use the full vertical momentum equation, vertical velocity is a predicted variable

uses the hydrostatic approximation, vertical velocity is not a predicted variable, can be used to represent frontal systems, can be used to represent the sea-breeze

Which of the following is/are true for a non-hydrostatic model? (choose all that apply) vertical velocity is predicted can not resolve convection explicitly, can be used to simulate a hurricane eyewall, can be used in models that have horizontal resolution greater than 50 km

vertical velocity is predicted, can be used to simulate a hurricane eyewall