Thunderstorm documentation, simulation and verification over

Pune P. Mukhopadhyay

Forecasting Research divisionIndian Institute of Tropical Meteorology

Pune-411008

Email:mpartha@tropmet.res.in

Outline of talk• Motivation for the study• Documenting few cases• Simulation with a mesoscale model• Verification of the result• Conclusion

• Thunderstorms are localized (Pune) mesoscale systems. Is it possible to document the life cycle of these events in the absence of any meso network?

• Whether such mesoscale systems can be simulated using numerical model?

• To what level of accuracy? (validation)

Thunderstorms Events over Pune (73.85oE, 18.53oN)• 9 June 2003

• 10 June 2003

Synoptic conditions of 9 June 2003

According to IMD’s Indian Daily Weather Report (IDWR): There was an off shore trough from Maharashtra to North Kerala on 8 June which further extends from Gujarat to Kerala coast on 9 June. The trough had a vertical extension between 3.1 to 4.5 km above sea level (a. s. l.).

There was a cyclonic circulation over Pakistan and adjoining Jammu and Kashmir with vertical extension upto 4.5 km a.s.l. The surface chart of 9 June shows the west coast trough and the low pressure area over Pakistan very clearly.

Synoptic conditions of 10 June 2003

According to IMD’s Indian Daily Weather Report (IDWR):

The persistence of off shore trough from Gujarat to Kerala coast.

One fresh cyclonic circulation is reported to have formed off Karnataka-Maharashtra coast between 2.1 and 4.5 km.

Contrasting rainfall of the events

For 9 June(IMD)’s Agricultural Observatory ( CAgMO) site 57.8 mm and at IMD’s Central Training Institute (CTI) observatory at Pashan (~ 6 km from IMD CAgMO site) was 65 mm For 10 JuneThe rainfall recorded at IMD CAgMO site is 2.6 mm where as that recorded in CTI, Pashan was 24.2 mm Rainfall for both the events lasted for an hour 1700-1800 IST

a. 0830Z 090603 WV b.10 Z 090603 IR c. 11 Z 090603 VIS d. 1230 Z 090603 VIS

e. 13 Z 090603 VIS f. 14 Z 090603 IR g. 15 Z 090603 IR h. 1730 Z 090603 WV

a. 0730Z 100603 WV b. 09Z 100603 VIS c.10Z 100603 VIS d. 11Z 100603 VIS

e.1230Z 100603 VIS f. 14Z 100603 IR g.15Z 100603 IR h. 1730 Z 100603 WV

Remarks•METEOSAT-5 Satellite images do capture different stages (genesis, maturity, dissipation) of the two localized thunderstorm events• However it does not provide information about the internal structure of the storm• As a consequence it is hard to diagnose the cause of contrasting rainfall by the two events just by satellite imageries

Simulation of 9 June 2003 event • Model – Regional Atmospheric Modelling System

(RAMS) [Cotton et al., 2003; Pielke et al. 1992]

(www.atmet.com latest version RAMSv6.0b2)

Some features of RAMS:• Nonhydrostatic, compressible

• Terrain following height coordinate [Gal-chen & Somerville,

1975; Clark, 1977]• Cumulus parameterization Kuo, KF• Radiation [Harrington, 1997]

• Cloud microphysics [Walko et al. 1995]• Land surface model- LEAF2 [Walko et al. 2000]

• Initialization Horizontally homogeneous, gridded anl

• Equations of motion

• Thermodynamic equation

• Water species mixing ratio continuity equation

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Model set up for the simulation

•Nos. of Domains – 2 [outer domain hor. Res. 16 km

inner domain hor. Res. 4km]•Nos. of Grid points- 68 x 68 x 36 [outer domain]

58 x 58 x 36 [inner domain]• Stretched vertical levels- 36 levels at 1.1:100:2000 (first level will have a thickness of 100 m, the next level will be of thickness 110m and so on till the level reaches the thickness of 2000m. When

thickness will be 2000 m, it will remain fixed for the rest of the levels.)

• Domain centered at- 73.85oE, 18.53oN • Cu parameterization- kuo scheme•Explicit microphysics – prognostic equation of rain,

pristine ice, snow, aggregates, graupel and hail.

Data Used• 6 hourly NCEP daily analyses

•RS/RW of Mumbai (76.3oE, 9.12oN) • USGS topography and vegetation at 30 arc sec resolutionSimulation experiments

Exp-1• 00 UTC 9 June 2003 initial condition•Initial nudging 6 hr•Forecast for 12 hr from 06 to 18 UTC

Exp-2• RS/RW data merged with NCEP anl and a mesoscale reanalyses at 16 km is made• Remaining steps are same as previous expt-1.

Hourly Total cloud condensate forecast Exp-1, 16-km domain

Hourly Total cloud condensate forecast Exp-2

Hourly Total cloud condensate forecast Exp-1, 4 -km domain

Hourly Total cloud condensate forecast Exp-2, 4 -km domain

Ver. Velocity at 850 hPa, Exp-1, 16-km domain

Ver. Velocity at 850 hPa, Exp-2, 16-km domain

Ver. Velocity at 850 hPa, Exp-1, 4-km domain

Ver. Velocity at 850 hPa, Exp-2, 4-km domain

Vert Vel (Red) at 850 hPa, Pcprate (blue) and Temp in deg cent (Green) at a grid close to Pune lat-lon

Forecast rain (left panel), CPC daily accumulated rain (mm) right panel

Concluding remarks

• The life cycle of localized thunderstorms of 9 and 10 June 2003 over Pune is reasonably well captured by the hourly Meteosat imageries.

• Mesoscale model RAMS could simulate the storm of 9 June with weaker intensity as compared to observation

• To document further details of a localized thunderstorm and to prepare a better input for mesoscale simulation and for model verification, data from remote sensing devices such as WP/RASS will be highly beneficial