1. Bill Scheftic Atmo 558 May 6th 2008
The (attempted) development of a cloud model from Fovell’s warm bubble exercise
Bill Scheftic
Atmo 558
May 6th 2008

2. Outline Introduction to model Model Dynamical Core in 3-d
Example of Discretization
Kessler Microphysics
Basic State
No Shear Case
Shear Case
00Z May 5, 2007 Case

3. Introduction to Model Pseud0-anelastic (flux form equations)
Boussinesq
No Coriolis force
Time resolution = 2 or 2.5 second
Horizontal grid: 500 m 750 m
Vertical grid: 500 m to 700 m

4. 3d - Dynamic Core – flux form

5. Discretization – Arakawa-C
Horizontal
Vertical
j=3 v v
k=3 w w
j=2 u s u s u
k=2 u s u s u
j=2 v v
k=2 w w
j=1 u s u s u
k=1 u s u s u
j=1
k=1 v v w w
i=1
i=1
i=2
i=2
i=3
i=1
i=1
i=2
i=2
i=3

6. Example for w-equation

7. Kessler Microphysics
Modified from WRF code (Kessler 1969, Klemp and Wilhelmson 1978, Wicker and Wilhelmson 1995)
Kessler scheme takes in prs, density, temp, Qv, Qc, and Qr
Returns a modified value of temp, Qv, Qc, and Qr over a given timestep.
Computes,
fall velocity of rain drops
autoconversion and collection.
condensation
evaporation of rain
Did not implement as tendency, rather updated at every timestep.

8. Basic State and Initial Cond.
Initialized sounding has about 1200 J/kg of Cape
Tropopause at 12000m
Lowest layer approx. 16 g/kg
Initial condition
0.7 K temp perturbation
8000 m diameter
Hydrostatically balanced at start

9. No-Shear

10. No-Shear

11. No-Shear

12. No-Shear

13. Shear

14. Shear

15. Shear

16. Shear

17. 00Z May 5, 2007 Case

18. 00Z May 5, 2007 Case

19. 00Z May 5, 2007 Case

20. 00Z May 5, 2007 Case

21. 00Z May 5, 2007 Case