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

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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 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
03 UTC 23 March
15 UTC 22 March
15 UTC 23 March
03 UTC 24 March
03 UTC 25 March
15 UTC 2 March
15 UTC 24 March
0/ UTC 26 March
15 UTC 27 March
15 UTC 28 March
15 UTC 26 March
From Gan and Rao 2006
Pezza and Simmonds, 2005
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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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Relative humidity - shaded Potential temperature
(isolines)
From Bonatti et al. 2006
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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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Surface Fluxes
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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?
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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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Warm pools detached from Brazil Current are
common but this one cant 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
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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 QT
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 QT
Typical barocliniic conversion
Ke-gtKZ
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See www.master.iag.usp.br/intercomp
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Conceptual view of the energetics
Bomb cyclone
Hurricane
QT
most
Few (hybrid)
Tropical storms
baroclinic
VTdU/dy
AZ -gtAE
barotropic
uvdU/dy KZ -gt 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