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Cyclone Classification:  Internal Structure versus Energetics - An aplication to the Catarina Event. . Pedro Leite da Silva Dias National Laboratory of Scientific Computing Ministry of Science and Technology Institute of Astronomy, Geophysics and Atmospheric Sciences

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Cyclone Classification:  Internal Structure versus Energetics - An aplication to the Catarina Event.

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Classical view 3a

Cyclone Classification:  Internal Structure versus Energetics - An aplication to the Catarina Event.

Pedro Leite da Silva Dias

National Laboratory of Scientific Computing

Ministry of Science and Technology

Institute of Astronomy, Geophysics and Atmospheric Sciences

University of São Paulo (USP)

Lll

Encontro internacional sobre ciclones do atlântico sul, previsão de trajetórias e avaliação de riscos

Rio de Janeiro, 19 a 21 de maio de 2008


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Classical view:


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But, on March 28 2004 …..


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03 UTC 22 March

15 UTC 22 March

03 UTC 23 March

15 UTC 23 March

03 UTC 24 March

15 UTC 24 March

03 UTC 25 March

15 UTC 2 March

0/ UTC 26 March

15 UTC 26 March

15 UTC 27 March

15 UTC 28 March

From Gan and Rao 2006

Pezza and Simmonds, 2005


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Produced by J. Conrado)


Classical view 3a

Produced by J. Conrado)


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Produced by J. Conrado)


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Produced by J. Conrado)


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Produced by J. Conrado)


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Produced by J. Conrado)


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Produced by J. Conrado)


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How about satellite derived precipitation?


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GOES/TRMM

(R.Gevaerd


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27 March 2004 11 Z

5-8km


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Vertical structure


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Relative humidity - shaded

Potential temperature (isolines)

From Bonatti et al. 2006

Q


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From Bonatti et al. 2006

Relative humidity - shaded

Potential temperature (isolines)

Q

F

F


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From Bonatti et al. 2006

Relative humidity - shaded

Potential temperature (isolines)


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Vertical Structure - FSU

http://www.moe.met.fsu.edu

Low troposphere vertical shear (warm x cold core)

Upper troposphere vertical shear

symmetry

Hart 2003 - Cyclone Phase


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upper

troposphere

AVN – ANALYSIS

lower troposphere


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upper

troposphere

CIRA AMSU retrieval

lower troposphere


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Cross section at 29.3S

00Z28Mar2004

Q1

EYE

Q2

EYE

NCEP – High resolution GFS analysis

50km


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SurfaceFluxes


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Sensible Heat Flux Anomaly

Surface


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Latent Heat Flux Anomaly

Surface


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How about the numerical guidance from the operational models?


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162 h 136h 114h

CPTEC ETA forecast at 06 UTC 28 Mar 2004


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90 h 66h 42h

CPTEC ETA forecast at 06 UTC 28 Mar 2004


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Does increased resolution improve the numerical results?


Brams

BRAMS

  • Version 3.0

    • Based on RAMS 5.04

    • Maintained by CPTEC

    • Particular features:

      • Shallow Cumulus Parameterization

      • Deep cumulus parametrization – “Grell-Ensemble”

      • Initialization of soil moisture

      • Option for surface processes: LEAD and SIB2 (with Carbon)

      • Surface data assimilation with internal quality control

      • CATT – dispersion module for gases and aerosols produced by biomass burning and urban sources

  • 2 grids: 32 km and 8 km (with cloud microphysics)

    • Previous experiments by Menezes et al. 2004- CBMET


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3h Precipitation BRAMS at 8km resolution


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Warm pools detached from Brazil Current are common but this one can’t be tracked …

This warm area may be important..

SST Anomalies – High Resolution data -20km


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Effect of high

Resolution SST:

less intense system !!!!

See Renato Silva 2004 -XIIICBMet


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Impact of perturbation in the latent heating vertical profile

Geopotential tendency is proportional to the vertical derivative of the diabatic heating


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Possible Trajectories with perturbed convective heating


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Better fit to obs


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Better fit to obs


Summary

Summary

  • Do tropical cyclones belong to a unique family?

  • OR are we artificially separating a continuum of atmospheric vortices into groups?

  • In Australia: subtropical lows with hurricane intensity winds


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ENERGETICS

Brennan e Vincent (1980)


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Cyclone tracking:

At each time, energetics at the box is computed


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NCEP GFS operational Analysis (high resolution 50km) of Catarina


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Other peculiar cases….


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Typical baroclinic system…


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This is the previous cyclone yesterday .ppt

Note large baroclinic conversion and increase of Ke

Small contribution of Q’T

Increase of Ke also related to barotropic conversion


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Ciclone off the S coast of Brazil - 13/Feb/2008

Initial phase is typically baroclonic

Latent heat picks up later…

Strong energy conversion

Barotropic conversion from Ke to Kz except at the end


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An interesting case of a schizophrenic cyclone…

(Santis et al. 2008)


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  • Ciclone 31/12/2007

  • Early moist baroclinic phase

  • Latter barotropic conversion


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Low predictability case:


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Small Q’T

Typical barocliniic conversion

Ke->KZ


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See www.master.iag.usp.br/intercomp


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Conceptual view of the energetics

Bomb cyclone

Hurricane

Q’T’

most

Few (hybrid)

Tropical storms

baroclinic

V’T’dU/dy

AZ ->AE

barotropic

u’v’dU/dy KZ -> KE


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Conclusions- I

  • Vertical profile of diabatic heating in operational models is too high: global and regional

  • Downscaling also lead to heating at higher levels: not enough pressure drop at low levels and therefore models underestimated the wind speed;

  • Perturbations in the vertical heating profile lead to intensification of the system: in one case the trajectory was substantially changed – the low pressure veered to the north and eventually reached the Rio de Janeiro coast

  • Energetics: early phase follows typical evolution of cold moist baroclinic perturbation. Later phase: barotropic conversion + moist conversion (not large).Hybrid system –subtropical low with hurricane intensity (1) at the end.


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  • Recommendations

  • Need objective classification system for hybrid systems such as Catarina: energetics is a possible choice;

  • The workshop organized by the Brazilian Meteorological Society recommended that in spite of the hybrid structure of the cyclone, if another case arises in the future, it is recommended that the systems be called “hurricane” when the estimated wind speed falls in the category I. This recommendation is based on the fact that the public perception that this type of event is significantly different from the regular extratropical and subtropical lows that regularly reach the southern part of Brazil

  • Articulated solution with WMO should be sought in order to improve classification of cyclones (according to the WMO manual: hurricanes are non frontal structures…) , personnel training and dissemination of the information. - IWTC Costa Rica Nov. 2006


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