simulation experiments of typhoons and …...simulation experiments of typhoons and tornadoes using...
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Simulation Experiments of Typhoons and Tornadoes Using
the Cloud-Resolving Model
Palace Side Hotel, Kyoto, JapanMarch 3 - 5, 2008
1. Introduction2. Cloud Resolving Strom Simulator (CReSS)3. Numerical experiment of Toyohashi tornado4. Simulations of Typhoon 0613 and tornado5. Summary
The First International Workshop on Prevention and Mitigation of Meteorological Disasters in Southeast Asia
Kazuhisa TsubokiHydrospheric Atmospheric Research Center (HyARC),
Nagoya University
Tornadoes and waterspouts are a violently rotating air below a convective cloud. Both are called “tatsumaki” in Japanese.
About 20 % of tatsumakis occur in association with typhoons in Japan. More than 60 % in the western Japan in warm season.
Even through a typhoon center is located in the distance, a tatsumaki occasionally causes a severe disaster due to wind.
For simulation of convective clouds and storms, we have been developing a cloud resolving model named “CReSS” (the Cloud Resolving Storm Simulator).
Intense tatsumakis occurred in Toyohashi City on September 24, 1999 and in Nobeoka City on September 17, 2006.
Using the CReSS model, we studied supercell storms and tatsumakis in association with typhoons.
Introduction
CReSS is formulated on the basis of the non-hydrostatic and compressible equation system.Coordinate system is a terrain-following in a two or three dimensional domain. Finite difference method is used for the spatial representation. Ground model and surface processes is implemented.Conformal Map projections are available.The CReSS model is optimized for parallel computers to perform large computations as well as a single processor (parallel and serial versions). Parallel processing is performed by the Message Passing Interface (MPI) and OpenMP.
Characteristics of the CReSS model
Diagram of cloud micro-physical processes in CReSS
Typhoon simulation with Δx=1km :T0418
Typhoon simulation with Δx=1km :T0418
Snow storm over the Great Lakes in North America
grid size: Δx=500m
Snow storm over the Great Lakes in North America
grid size: Δx=500m
CReSS simulation Radar observation
Heavy rainfall associated with Baiu front: Niigata heavy rain
Rain by TyphoonBars:ObservationSolid line: CReSSDashed line: RSM
Rainfall intensity (mm/hr)
Time (UTC)
grid size: Δx=1km
Tiling extension function of CReSS ver.3
Precipitation rate (mm/hr) at 5 days from initial time.
Red line: JMA best track of Typhoon 18.
Black line: CReSS simulation result.
7 days simulation of T0418
Typhoons and tornadoes (tatsumakis)
ーTornado with Typhoon 9918, September 24, 1999 in Toyohashi Cityー
ーTornado with Typhoon 0613,September 17, 2006 in Nobeoka Cityー
11JST, 24 September 1999; T9918
14JST, 17 September 2006; T0613
Cloud images (IR)
ーTornado with Typhoon 9918, September 24, 1999 in Toyohashi Cityー
24 September 1999, Toyohash (from Yomiuri Shinbun )
Doppler radar observation of the supercell
PPI of Doppler velocity
U-wind
V-wind
theta
theta_e
Experimental design of Toyohashi tornado
domain 48km × 48km × 12kmhorizontal grid size 75mvertical grid size 25 ~ 200mgrid numbers 603 × 603 × 63integration time 4 hourstime increment large: 0.5s, small: 0.1smicrophysics the bulk cold rain typeinitial condition Shionomisaki sounding data at
09JST, 24 September 1999.initial disturbance warm bubbleboundary condition the wave-radiating typeplatform HITACH SR8000, 8nodes
Vorticity (/s)
Pressure perturbation (hPa)
ーTornado with Typhoon 0613,on September 17, 2006 in Nobeoka Cityー
JMA radar14JST, 17 Sept.
Nobeoka
Rainbands of T0613
CReSS Experimental Design
the Earth Simulator 128nodes (1024CPU)
the Earth Simulator128nodes(1024CPU)
Plat formcold raincold rainCloud phyc.CReSS 500mJMA-RSM(40km)BoundaryCReSS 500mJMA-RSM(40km)Initial value1.5 hours6 hoursIntegrationx:1795, y:2435, z:67x:1795, y:1795, z:67Grid numberrainband area896 km ×896 kmDomain75m500mResolutiontorunadoesconvective cloudsObjectivesExp.75mExp.500m
Experimental Design of Typhoon T0613Domain H: 896 km × 896 km × V: 20 kmH-gird size 500 mV-grid size 100 ~ 320 m (stretched) Grid numbers H: 1795 × 1795× V: 67Integration time 6 hoursTime increment large: 2 sec, small: 0.5 secMicro-physics the bulk cold rain typeInitial condition JMA Regional Spectral model (40km)Boundary JMA Regional Spectral model (40km) Surface real topography and observed SST ES node number 128 nodes (1024 CPU)
CReSS500mVelocity and rain
mixing ratio (shadings) at a height of 1.9km.
How do we find supercells in such many convective clouds ?
3 rainbands formed
Identification of supercells
Convective cells are explicitly simulated in the experiment with a horizontal resolution of 500m.A supercell is defined as “a convective cell with a vorticity larger than 0.01 /s within an upward motion”.We identify a convective cloud as supercell in the simulation using the following index.SCI(Supre Cell Index):above the cloud base ( at a height of 2~4km)
wyu
xvS ⋅⎟⎟
⎠
⎞⎜⎜⎝
⎛∂∂
−∂∂
= CI
A convective cloud with SCI > 0.1 is super cell.
Velocity vectors, rain mixing ratio (shadings)
and SCI (contours) at 1.9 km in height.
The outer rainband is composed of supercells.
The east coast of Kyushu
Toyohashi Supercell
Supercell and tornado in T0613Domain H: 60 km × 60 km × V: ~20 kmH-gird size 75 mV-grid size 40 ~ 300 m (stretched) Grid numbers H: 803 × 803× V: 67Integration time 6 hoursTime increment large: 0.5 sec, small: 0.1 secMicro-physics the bulk cold rain typeInitial condition CReSS 500m simulation outputBoundary CReSS 500m simulation output Surface real topography and observed SST Computer HITACHI SR11000 (4nodes)
Vorticity (contour) and rain (color)
1000m
central vorticity: 0.9/s
vorticity (contour) and pressure (color)
1000m
pressure perturbation:27hPa
vorticity (contour) and speed (color)
1000m
maximum speed: 70m/s
vorticity (contour) and vertical velocity (color)
1000m
1000m
Vorticity (contour) and rain mixing ratio (color)
1000m
hPa
vorticity (contour) and pressure perturbation (color)
m/s
1000m
vorticity (contour) and speed (color)
m/s
1000m
vorticity (contour) and vertical velocity (color)
Domain of 75m-resol.
CReSS Exp-75mRainfall intensity
East coast of Kyushu
How are tornadoes found in the domain?
Index to find tatsumakisThe definition of tatsumaki (tornadoes and waterspouts) is a violently rotating air column below a convective.We define a tatsumaki more strictly to distinguish it in a model output as “rotating air in a dynamic balance between pressure gradient force and centrifugal force (the cyclostrophic balance) in a high accuracy.”Tatsumaki Index (TI) is defined as follows in the lower atmosphere.
' TI pyu
xv
⋅⎟⎟⎠
⎞⎜⎜⎝
⎛∂∂
−∂∂
=
Vortex with TI <-1 is distinguish as tatsumaki.
1000m
CReSS Exp-75mrainfall intensity (shading)TI(contour)
CReSS75mrainfall intensity (shading)TI(contour)
1000m
Result of Exp-75mRainfall intensify
Many tornadoes occur along the outer rainband.
SummaryTyphoons occasionally accompany tornadoes (tatsumakis in Japnese) and cause disasters due to strong winds. CReSS simulated the tornado within the supercell with the uniformly fine grid (75m) in the large domain.The simulation shows that successive formation of tornado vortices within the maximum updraft of the supercell.When the typhoon 0613 approached the western Japan on September 17, 2006, it accompanied a severe tornado. It killed three people and caused a train accident. In the experiment with a resolutoin of 500m, 3 rainbandswere simulated on the east side of Typhoon 0613. They are composed of supercells.The high resolution (75m) simulation showed that one of the supercells spouted an intense tornado. The detailed structure of the tornado was successfully simulated.Simulation of tornado in the large domain showed that many tornadoes occur along the outer rainband.
Thank you !!The CReSS model (Ver.2.3) is free for scientific researches. If you are interested in CReSS, Please contact with me (K. Tsuboki). (HyARC, Nagoya University)