1. Vertical Coordinates and Nesting

2. Vertical Coordinate Systems
Originally p and z: but they had a problem…BC when the grid hit terrain!
Then eta, sigma p and sigma z, theta
Increasingly use of hybrids– e.g., sigma-theta

3. Sigma

4. Sigma-Theta

5. Hybrid and Eta Coordinates
Ptop
Ptop
 = 0
Pressure domain
 = 0
Sigma domain
ground
 = 1
ground
 = 1
MSL

6. Horizontal resolution of 12 km
12-km terrain

7. Nesting

8. Why Nesting?
Could run a model over the whole globe, but that would require large amounts of computational resource, particularly if done at high resolution.
Alternative is to only use high resolution where you need it…nesting is one approach.
In nesting, a small higher resolution domain is embedded with a larger, lower-resolution domain.

11. Nesting Can be one-way or two way.
In the future, there will be adaptive nests that will put more resolution where it is needed.
And instead of rectangular grids, other shapes can be used.