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

Pedro Leite da Silva DiasNational Laboratory of Scientific ComputingMinistry of Science and TechnologyInstitute of Astronomy, Geophysics and Atmospheric Sciences University of São Paulo (USP)

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

Rio de Janeiro, 19 a 21 de maio de 2008

Classical view:

But, on March 28 2004 …..

From Gan and Rao 2006

Pezza and Simmonds, 2005

03 UTC 22 March 03 UTC 23 March

03 UTC 24 March 03 UTC 25 March

0/ UTC 26 March 15 UTC 27 March 15 UTC 28 March15 UTC 26 March

15 UTC 2 March15 UTC 24 March

15 UTC 22 March 15 UTC 23 March

Produced by J. Conrado)

Produced by J. Conrado)

Produced by J. Conrado)

Produced by J. Conrado)

Produced by J. Conrado)

Produced by J. Conrado)

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How about satellite derived precipitation?

GOES/TRMM

(R.Gevaerd

27 March 2004 11 Z

5-8km

Vertical structure

Q

Relative humidity - shadedPotential temperature (isolines)

From Bonatti et al. 2006

Q

FF

From Bonatti et al. 2006 Relative humidity - shadedPotential temperature (isolines)

Relative humidity - shadedPotential temperature (isolines)

From Bonatti et al. 2006

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

AVN – ANALYSIS

uppertroposphere

lower troposphere

CIRA AMSU retrieval

uppertroposphere

lower troposphere

Cross section at 29.3S

00Z28Mar2004

Q1

Q2

EYE

EYE

NCEP – High resolution GFS analysis

50km

Surface Fluxes

Sensible Heat Flux Anomaly

Surface

Latent Heat Flux Anomaly

Surface

How about the numerical guidance from the operational models?

162 h 136h 114h

CPTEC ETA forecast at 06 UTC 28 Mar 2004

90 h 66h 42h

CPTEC ETA forecast at 06 UTC 28 Mar 2004

Does increased resolution improve the numerical results?

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

3h Precipitation BRAMS at 8km resolution

SST Anomalies – High Resolution data -20km

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

This warm area may be important..

Effect of high

Resolution SST:

less intense system !!!!

See Renato Silva 2004 -XIIICBMet

Impact of perturbation in the latent heating vertical profile

2 fo2 2

p2 tfoV

g

2

fo+ f

f o2

R

p

V g T

pf o2

R

cp

pJp

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

Possible Trajectories with perturbed convective heating

Better fit to obs

Better fit to obs

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

ENERGETICS

Brennan e Vincent (1980)

αω−=dt

dTCpQ

Cyclone tracking:

At each time, energetics at the box is computed

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

Other peculiar cases….

Typical baroclinic system…

Note large baroclinic conversion and increase of Ke

Increase of Ke also related to barotropic conversion

Small contribution of Q’T

This is the previous cyclone yesterday .ppt

Initial phase is typically baroclonic Latent heat picks up

later…

Strong energy conversion

Barotropic conversion from Ke to Kz except at the end

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

An interesting case of a schizophrenic cyclone…

(Santis et al. 2008)

Ciclone 31/12/2007

•Early moist baroclinic phase

•Latter barotropic conversion

Low predictability case:

Small Q’T

Ke->KZ

Typical barocliniic conversion

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

Conceptual view of the energetics

Q’T’

V’T’dU/dy

u’v’dU/dy KZ -> KE

barotropic

baroclinic

Bomb cyclone

Hurricane

Tropical storms

Few (hybrid)

most

AZ ->AE

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.

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

•The workshop organized by the Brazilian Meteorological Society

•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

• 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