1. An exploration of basic aspects of modeling using the warm bubble Kim Wood May 7, 2008 a.k.a. A documentary of a newbie’s journey through the jungles of Fortran code, discretization, and basic modeling

2. Outline  Introduction  Approach  Process  Results  Conclusions

3. Introduction  Warm bubble: basic modeling situation  Simple parameters  Dry, isentropic atmosphere  Small domain size  Artificially slowed sound waves (50 m/s)  Arakawa-C grid

4. Approach  Still new to modeling: wanted something relatively straightforward  Followed outline of programming methods in the notes by Robert Fovell  Learned GrADS for output

5. Process  Grid setup  Taking the time to digest what’s going on  Initialization of fields: Exner function, theta  Discretization and coding of equations  Troubleshooting  Debugging  Rinse, repeat…

6. Warm bubble, standard

7. And the opposite…

8. Changing parameters  Same amount of time elapsed in each 1sec dt, 400x400 resolution 1sec dt, 1000x1000 resolution

9. Changing parameters 2.5 sec dt, 400x400 resolution 2.5 sec dt, 1000x1000 resolution

10. Model: speed of sound  Initial: dt=2s, c s =50m/s  For dt=2s, c s =100m/s, the model crashed  For dt=1s, c s =100m/s, it ran normally but took longer  Same: dt=.5s, c s =200m/s  This reinforces similar discussions from class

11. Trying a tracer  Attempted to insert a passive tracer into the model  The results weren’t quite what was desired  Future work will try to explore this in greater detail

12. Conclusions  It is possible to program a warm bubble!  Process improved understanding of grid domains, boundaries, and discretization  Good project for a beginner in the subject  Future experimentation:  Constant heat source  Moisture manipulation  Modeling of the sea breeze circulation

13. Acknowledgements  Andy and Rafael, for putting up with my constant questions and getting me started (and often unstuck) in both Fortran and GrADS – Thanks! =)