ch2-partB summery Flashcards
1
Q
Space difference schemes are used to:
A
- March forward in space
2
Q
Time difference schemes are used to:
A
- March forward in time
3
Q
Time difference schemes meet:
A
- The accuracy requirement at the first and second order
- Higher order schemes appear cumbersome and are not widely used in NWP
4
Q
Temporal differencing schemes:
A
- Explicit
- Model prognostic equations are approximated using finite differences so that the variables at the future time appear only on one side of the equation
- Implicit
- Variables at the future time appear on both sides of the equation
5
Q
Leapfrog time differencing:
A
- An example of explicit schemes
6
Q
To obtain leapfrog time differencing equation:
A
- Apply centered finite difference approximation in time and space to partial derivatives
7
Q
To obtain implicit equations:
A
- Apply:
- Backward finite difference in time and
- Centered finite difference in space
8
Q
The resulted equation (from implicit scheme):
A
- Implicit time differencing scheme
9
Q
Courant number:
A
- Limiting value that is necessary for the time differencing schemes to produce numerically-stable solutions
- Non-dimensional
10
Q
CFL conditions:
A
- Limiting value of the courant number
11
Q
CFL conditions represent:
A
- The maximum value of the courant number that permits numerically-stable model solutions
12
Q
The exact value of the CFL conditions:
A
- Vary
13
Q
The exact value of the CFL conditions varies depending on:
A
- Spatial and temporal finite different scheme utilized
14
Q
Choosing fine grid spacing result on
A
- Small steps between intermediate forecasts leading to an increase in
- The number of time steps and
- Computing time
15
Q
According to CFL conditions fine mesh model forecasts require:
A
- More number of intermediate time steps and therefore
- Need powerful computers
