The Cloud Resolving Storm Simulator: Large-scale Parallel Computations

2. Asia-Pacific Advanced Network 27 August 2003 The Cloud Resolving Storm Simulator:Large-scale Parallel Computations HPC application to Meteorology in Japan TSUBOKI Kazuhisa SAKAKIBARA Atsushi HydrosphericAtmospheric Research Center, Nagoya University, Japan

3. OUTLINE • Description of the numerical model: the Cloud Resolving Storm Simulator(CReSS) • Numrical Experiment of tornado within supercell • Numerical Experiment of typhoon • Numerical experiment of snow cloud over the sea • Summary

4. Introduction • Convective clouds and storms are highly complicated systems of flows and hydro-meteors. Their structure and dynamics are determined by a nonlinear interaction between the fluid dynamics and the cloud microphysics. • In order to simulate an evolution of a convective cloud storm, it is essential to formulate cloud physical processes as well as the fluid dynamic and thermo- dynamic processes.

5. A detailed formulation of cloud physics requires many prognostic variables even in a bulk method such as cloud, rain, ice, snow, hail and so on. • It is impossible to perform this type of simulation of cloud systems without a huge memory and parallel computing.

6. Purposes • A thunderstorm produces many types of severe weather: heavy rain, hail storm, downburst, tornado and so on. • The purposes of this study are to develop a cloud resolving model, the Cloud Resolving Storm Simulator “CReSS” and its parallel computing to simulate cloud- scale to storm-scale phenomena. • The simulation of the thunderstorm will clarify the characteristics of dynamics and evolution and contribute to the storm-scale prediction.

7. Targets of CReSS are ... to perform large-scale numerical experiments of mesoscale storms and prediction experiments of real severe weather systems • within a very large domain, ～500 km × 500 km • with very high resolution, 1 km ～10 m in horizontal • with detailed cloud microphysics and • with optimization for high performance parallel computers (including the Earth Simulator)

8. Characteristics of CReSS • CReSS is formulated in the non-hydrostatic and compressible equation system. • Coordinate system is a terrain-following in atwo or three dimensional geometry. • Prognostic variables are: • three-dimensional velocity components • perturbation of pressure • perturbation of potential temperature • subgrid-scale turbulent kinetic energy, TKE • mixing ratios for water vapor and several types of hydrometeors

9. Finite difference method for the spatial discretization. • Time integration is mode splitting method. • Large time step: the leap-frog with the Asselin time filter. • Small time step : explicit both in horizontal and vertical or explicit in horizontal and implicit in vertical. • Advection is a fourth order scheme. • Turbulence is the first order closure and 1.5 order closure with TKE. • Numerical smoothing is the second or forth order computational mixing.

10. Cloud physics is formulated by a bulk method of cold rain. • Prognostic variables for mixing ratios are: • water vapor • cloud water • rain water • cloud ice • snow • graupel

12. Initial conditions are: • horizontally uniform field from upper air sounding or theoretical function • three-dimensionally inhomogeneous data • Lateral boundary conditions are: • rigid wall, periodic, zero normal gradient • wave-radiating • externally forced time-dependent condition • Ground model and surface processes have been implemented. • Parallel processing is performed by the Message Passing Interface, MPI.

13. Decomposition and communication

14. Overview of the tornado (TATSUMAKI) The tornado occurred on 24 September 1999 was one of the most Intense tornadoes in Japan. It occurred during day time. They took many pictures and videos. These are samples of the pictures of the tornado. A dark funnel reached to the ground from the cloud. The horizontal diameter of the tornado was about 500 m.

15. Doppler radar observation of the tornado-producing super-cell • Horizontal displays of radar echo of the super-cell with a trace of the tornado (tatsumaki) observed on 24 September 1999 in the Tokai District, Japan. The tornado occurred at the central part of the a hook- shaped echo. • Vertical cross-section of radar echo of the super-cell. A vault structure is significant. • Horizontal display of Doppler velocity. A signature of mesoscale cyclone was observed.

16. Experimental design of simulation－ Supercell and Tornado － • domain 48km × 48km × 12km • horizontal grid size 75m • vertical grid size 25 ～200m • grid numbers 603 × 603 × 63 • integration time 4 hours • time increment large: 0.5s, small: 0.1s • microphysics the bulk cold rain type • initial condition Shionomisaki soundingdata at 09JST, 24 Sept. • initial disturbance warm bubble • boundary condition the wave-radiating type • platform SR8000, 8nodes

17. The 2-dimensional horizontal display ofthe simulated super-cell CReSS successfully simulated the super-cell observed in the Tokai District. The simulated super-cell was in quasi-steady state around 1.5 hours after the initial time. The 2-dimensional horizontal display will show its evolution and movement. The color level is the mixing ratio of precipitation, the thick red lines are intense vorticity and white lines are vertical velocity at a height of 1000 m. The thick blue lines indicate the surface gust front. Arrows are the surface horizontal velocity.

18. Close view of the simulated tornado in horizontal • Vertical vorticity at a height of 100m (a) when the tornado was generated and (b) in the mature stage. • Pressure perturbation at a height of 100m (a) when the tornado was generated and (b) in the mature stage. The velocity field is in the cyclostrophic balance with the pressure field.

19. Close view of the simulated tornado in vertical • Vertical vorticity and pressure perturbation. • Vertical vorticity and vertical velocity.

20. The 3-dimensional movies of the tornado Since the tornado within the super- cell has a highly 3-dimensional structure, we made the 3-dimensional movies of the tornado obtained from the simulation experiment. The movies shows vertical vorticity larger than 0.15 /s and the surface temperature perturbation within the box of 13 km in horizontal and 12 km in vertical. The period of display is about 2 hours.

21. The 2-dimensional movie of vertical vorticity In order to examine a detailed process of the development of the tornado, we will show a 2-dim. movies of vertical vorticity which focus on the stage of the tornado genesis. The display is a projection of the tornado on the west-east vertical plane. The movies shows that the tornado developed from the lower level to the upper level.

22. Experiment of Typhoon 0111

23. Experimental Design of - Typhoon 0111 - • domain 400km × 400km × 14km • horizontal grid size 4000m • vertical grid size 400m • grid numbers 103 × 103 × 35 • integraion time 12 hours • time increment large: 3s, small: 1.5s • topographyincluded • surface processincluded • sea surface temp.contant at 300.16 K • micropysics the bulk cold rain type • initial condition JMA RSM analysis at 03Z Aug.05 2001 • boundary condition JMA RSM analysis • platform VPP5000, 1node

24. The 3D animation of Typhoon 0111 The simulation of Typhoon 0111 is visualized in 3-dims. All calculation domain is displayed. The color levels show surface pressure perturbation. The brightly white parts indicate clouds and gray parts are rain. The animation shows the typhoon which was located to the west of the domain at the initial time moved into the domain smoothly through the west boundary.

25. Experiment ofSnow Cloud Bands over the Japan Sea(the East Sea)

26. Observation of Snow Clouds Visible satellite image (GMS) at 15 JST JMA radar at a height of 2 km

27. Experimental Design of Snow Cloud Bands- Japan Sea Case on 5 January 2003 - • domain 1080km × 720km × 10km • horizontal grid size 2000m • vertical grid size 300m • grid numbers 543 × 363 × 35 • integraion time 18 hours • time increment large: 3s, small: 1s • topographyincluded • surface processincluded • sea surface temp.NCEP 1 week average • micropysics the bulk cold rain type • initial condition JMA RSM at 00Z Jan.05 2003 • boundary condition JMA RSM • platform SR8000, 8node

28. Result of the Simulation Animation of horizontal display of cloud mixing ratio (g/kg) and the horizontal wind vectors at a height of 1350 m. Animation of horizontal display of precipitation mixing ratio (g/kg) and horizontal wind vectors at a height of 450m.

29. Animation of horizontal display of vorticity (10e-3/s) and the horizontal wind vectors at a height of 1350 m. Animation of horizontal display of vertical velocity (m/s) and the horizontal wind vectors at a height of 1350 m.

30. Summary • We are developing the Cloud Resolving Storm Simulator, CReSSfor simulations of cloud-scale to storm-scale phenomena. • Parallel computing is essentially important for this type of large simulations. • CReSS characteristic features and some result obtained in dry experiments were presented. • The result suggested that CReSS is capable to simulate a thunderstorm and a related phenomenon.

31. The result of the simulation experiment of the supercell and the associated tornado was presented. CReSS simulated both disturbances with a uniformly fine grid spacing. • Prediction experiment of snow cloud over the sea showed that the detailed structure of roll convections and mesoscale disturbances of snow clouds. • The result suggested that CReSS is capable to simulate a thunderstorm and a related phenomenon.

32. Future Plans of CReSS • Detailed cloud microphysical processes which resolve size distributions of hydrometeors • Parameterization of turbulence • Nesting in a coarse-grid model • Data assimilation of Doppler radar • Radiation of cloud

33. Thank you !!

35. Summary • We are developing CReSSfor simulations of clouds and storms with parallel computation. • CReSS simulated the tornado within the supercell with the uniformly fine grid spacing (75m) in the large domain. • The simulation shows that successive formation of tornado vortex within the maximum updraft of the supercell. • The tornado develops from the surface and extends to the upper level. • We infer that the tornado is caused by stretching of the lower-level vortex resulted from shear instability.