Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

NWP lecture > chapter 4 summery > Flashcards

chapter 4 summery Flashcards

1
Q

Model domain refers to:

A
  • Model’s forecast area of coverage
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Numerical models divide into:

A
  • Global models
    • Covering the whole globe
  • Regional models
    • Covering a more limited area
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Limited area models (LAM) boundaries

A
  • Horizontal (lateral)
  • Top and bottom (vertical)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Global models boundaries:

A
  • One vertical boundary (by nature cover the entire earth)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Domain of an NWP model can be viewed as:

A
  • 3D array of cubes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Describe the NWP model 3D array cubes:

A
  • Each cube encompasses a volume of the atmosphere corresponding to a model grid point
  • Forecast values for met variables in each cube are derived from
    • The current values within the cubes + from the surrounding cubes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Information needed to provide forecast values for the meteorological parameters. Why?

A
  • Cannot be determined using only the data contained in the model
  • Because he cubes on the boundaries are not surrounded by other cubes on all sides
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How to solve the problem?

A
  • The information from the outside boundaries must be supplied from another source (boundary conditions)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Global model merits:

A
  • Global coverage
  • Don’t require boundary conditions
  • Necessary at longer lead times when weather at a location is effected by distant weather system
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Global model drawbacks:

A
  • Coarse spatial resolution
    • Need parameterization of sub grid scale physical processes
  • On a regular latitude-longitude grid, the grid boxes will become smaller in the longitude direction near the poles (high possibility of CFL condition violation)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Regional models merits:

A
  • Higher resolution
    • Higher spatial resolution
      • Do not require parameterization of some physical processes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Regional models drawbacks:

A
  • Require boundary conditions
  • (for boundary conditions) regional models depend on global models
  • Parameterization required for physical processes smaller than the grid size
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Requirements to solve the forecast equations:

A
  • Accurate information
    • for all forecast variables and
    • Along each model boundary
      • Lateral
      • Top
      • Bottom
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How is the lateral boundary conditions data supplied to LAM?

A
  • Using large-domain models
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Boundary values are obtained from:

A
  • Observed data
    • Data assimilation system
  • Forecast values from a current or previous cycle of a large scale model (LBC in LAM)
  • Climatological or fixed values
    • For specifying some surface characteristics such as
      • Soil moisture
      • SST
      • Vegetation type
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Favorable source of boundary values is:

A
  • Observed data
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Favorable source of lateral boundary conditions values is:

A
  • Previous run of a large domain model
18
Q

Factor effecting the quality of LAM predictions

A
  • Quality of predictions produced by the model supplying the LBC
19
Q

Consequence of errors in forecast from large domain model:

A
  • Error will move into the LAM’s forecast domain and amplify
20
Q

LBC control:

A
  • Position
  • Evolution of features that cover the entire forecast domain
21
Q

Longwave patterns are largely determined by

A
  • Boundary conditions
22
Q

Weaker impacts are noted on

A
  • Jet streaks and fronts
    • Regions far downwind from the upstream boundary
23
Q

Synoptic scale model supplying the boundary conditions determine

A
  • The placement and
  • Timing of synoptic scale features
24
Q

Influence of boundary conditions:

A
  • Spread away from (downstream) of the boundary
  • Effects amplify downstream
25
Q

Preferable area of primary forecast concern:

A
  • As far from the boundaries as possible
    • Especially the upstream boundary
26
Q

Boundary influence is carried by:

A
  • The wind
27
Q

…………………….. and ……………………. Will vary from one flow regime to another

A
  • The wind and
  • The direction of greatest forecast impact
28
Q

Forecasters should pay attention to

A
  • How long it takes a trajectory to move from the model boundary to the vicinity of their forecast area
29
Q

How to reduce the influence of boundary errors within the area of interest:

A
  • Placing the upstream boundary well outside the forecast area
30
Q

One-way interaction:

A
  • If information flows in one direction, from larger domain model to the smaller domain model
31
Q

Nested model:

A
  • Some LAM (eg. MM5) are run with small-area, finer-resolution grids nested inside of coarser-resolution grids within the same model
32
Q

Nesting is necessary because:

A
  • Computer memory ad speed limitations prohibit fine-resolution grids from covering the entire model domain
33
Q

How information from outer boundaries are supplied to nested grid models:

A
  • Supplied from an outside source using one-way interaction
34
Q

Interface between the grids inside the nested grid model are determined from:

A
  • The forecasts within the model itself
35
Q

The forecast variables for the coarse grid are updated based on:

A
  • Fine grid prediction
    • Where the fine grid covers the coarse grid
36
Q

Two way interaction:

A
  • Coarse-grid prediction affects the fine grid prediction by
    • Supplying boundary conditions on the mesh surface
      • (this information flows both ways)
37
Q

Weather forecasting is:

A
  • An initial value problem (IVP):
    • The outcome is significantly determined by the conditions given at the start
38
Q

To produce a forecast for tomorrow you need:

A
  • To start by determining, as precisely as possible, the state of the atmosphere today
39
Q

The initial conditions describe:

A
  • The state of the atmosphere (at grid points) at the starting point of the forecast
40
Q

Initial conditions include:

A
  • The 3D fields of the forecast variables (u,v,w,T,p..) over the model domain
41
Q

The initial conditions are obtained from:

A
  • The observed data and
  • Previous forecast

Through a process known as data assimilation

42
Q

Local winds upstream and downstream:

A

The same direction of local wind is downstream boundary while if it is opposite to the local wind it is upstream

NWP lecture (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions