1. Gravity waves above deep convection: Modeling results showing wave breaking & turbulence in a 3D model. NCAR-RAL 6 July 2006 Todd Lane The University of Melbourne Australia - How / when do gravity waves break down near convection. - What is the nature of the resultant turbulence. - What can we learn from high resolution cloud models.

2. From Lane, Sharman, Clark, & Hsu, JAS 2003. U(z)  U ~ 10 m/s will give (U-C) = 0 for downshear waves. ~5-10 km. 2D Breaking - Dickinson Case.

4. Questions raised… To date - this breaking in lower-stratosphere (in a high- resolution complete CRM simulation) has only been demonstrated in 2D. What happens in 3D? - Do waves break at same location? - 2D case should maximize breaking. 3D required to quantify turbulence & determine details of breakdown. To date - this breaking in lower-stratosphere (in a high- resolution complete CRM simulation) has only been demonstrated in 2D. What happens in 3D? - Do waves break at same location? - 2D case should maximize breaking. 3D required to quantify turbulence & determine details of breakdown.

5. 3D Cloud model - Clark model.  x=  y=  z= 150 m 674 (L) x 338 (W) x 234 (H) 100 km x 50 km x 35 km Anelastic, nonhydrostatic. Simplified microphysics - Kessler warm rain Smagorinsky turbulence. Midlatitude, real sounding case. Moderate negative shear above cloud top. (Same scenario as previous 2D cases).

6. Potential temperature (2 K intervals), t = 60 mins

7. Potential temperature (2 K intervals), t = 75 mins But what does the 3D breaking look like? Similar pattern of breaking - breaking of downshear waves. - Less mixing in 3D

9. “New” waves emanating from breaking region. - secondary waves.

10. TKE 1/2 = TKE 1/2 (subgrid)+TKE 1/2 (resolved) resolved: <= 2 km

13. Do waves only break above convection? 2D - Case using real sounding over Nashville,TN. Smooth waves above cloud - turbulence upstream.

14. Future Directions: -Explore the parameter space - currently underway. -More real case studies. - What conditions lead to breaking around convection. - Is this uncommon - or just a low probability of encountering turbulence?

15. Vertical Velocity @ 15 km (0.2 m/s interval)