Cluster Analysis of Tropical Cyclone Tracks

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Cluster Analysis of Tropical Cyclone Tracks

• Suzana J. Camargo

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Collaborators

• Andrew W. Robertson,
• IRI, Columbia University
• Scott J. Gaffney and Padhraic Smyth, University
  of California, Irvine
• Michael Ghil,
• University of California, Los Angeles.

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Outline

• Introduction
• Clustering Technique
• Previous works
• Western North Pacific Results
• Mean Regression Trajectories
• Tracks
• Properties of main clusters
• ENSO Relationship
• Composites

• Eastern North Pacific Results
• Mean Regression Trajectories and Tracks
• ENSO relationship
• North Atlantic Results
• Mean Regression Trajectories and Tracks
• ENSO relationship
• Atlantic multi-decadal signal

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Introduction

• Identify different track types, their seasonality
  and relation with large-scale circulation and
  ENSO.
• Importance different track types have higher
  incidence on some years and make landfall in
  different regions.
• New clustering technique used.
• Best track datasets
• Western North Pacific JTWC 1950-2002.
• North Atlantic NHC 1851-2003.
• Eastern North Pacific NHC 1949-2003.
• Only tropical cyclones (TCs) with tropical storm
  or hurricane (typhoon) intensity (no tropical
  depressions).

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Clustering Technique

• Developed by S.J. Gaffney and P. Smyth
• - S.J. Gaffney (2004), Ph.D. thesis, University
  of California, Irvine.
• Mixture of polynomial regression models (curves)
  to fit the geographical shape of the
  trajectories.
• Extension of the standard multivariate finite
  mixture model to allow quadratic functions.
• Enable highly non-Gaussian density functions to
  be expressed as a mixture of a few PDFs.
• Fitting by maximizing the likelihood of the
  parameters.
• Rigorous probabilistic context for clustering
• Accommodate easily tropical cyclone tracks of
  different lengths.

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Previous works on Cluster Analysis and Tropical
Cyclones

• Western North Pacific
• P.A. Harr and R.L. Elsberry, Mon. Wea. Rev. 123,
  1225-1246 (1985).
• J.B. Elsner and K.B. Liu, Climate Research 25,
  43-54 (2003)
• North Atlantic
• J.B. Elsner, Bull. Amer. Meteor. Soc. 84, 353-356
  (2003) J.B. Elsner et al., J. Climate 13,
  2293-2305 (2000).
• Eastern North Pacific (TC precursors)
• J.B. Mozer and J.A. Zehnder, J. Geophys. Res.
  Atmos. 99, 8085-8093 (1994).

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Western North Pacific Tropical Cyclones Cluster
AnalysisResults
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Mean Regression Trajectories

• Appropriate number of clusters appears to be
  seven.
• Quantitative (out of sample likelihood) and
  subjective analysis.
• Two main trajectory-types straight-movers and
  recurvers.
• Additional clusters detailed differences in
  shape among these types.

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TRACKS TROPICAL CYCLONES Western North Pacific
1983-2002
TRACKS
MEAN REGRESSION TRAJECTORIES
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Number of TCs per Cluster
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Cluster A
TRACK DENSITY
FIRST POSITION DENSITY
NTC ANNUAL CYCLE
Landfall 63
Regression Trajectory

• 67 reach typhoon intensity

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Cluster B
TRACK DENSITY
FIRST POSITION DENSITY
NTC ANNUAL CYCLE
Landfall 61
Regression Trajectory
50 only reach TS intensity.
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Cluster C
TRACK DENSITY
FIRST POSITION DENSITY
NTC ANNUAL CYCLE
Landfall 7
Regression Trajectory

• 70 reach typhoon intensity

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ENSO Relationship
NTC- Number of Tropical Cyclones
ACE Accumulated Cyclone Energy
Total ACE has a well known relationship with ENSO
(Camargo Sobel, 2005).
Total NTC per year is not significantly correlated
with ENSO (e.g. Wang Chan, 2002).
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Tracks El Niño years
Tracks La Niña years
Cluster A
Cluster E
Cluster G
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Track Density per year Difference El Niño and La
Niña years
Full basin
Cluster A
Cluster G
Cluster E
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Mean NTC and ACE per cluster and ENSO
A
E
G
A
G
E
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SST Anomalies Composites
TCs first positions
SST and TC data for SST composites11/81 12/02
Regression trajectory
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Sea Level Pressure Anomalies Composites
NCEP Reanalysis and TC data for composites
1950-2002
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Anomalous Low Level Wind Composites
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Wind Shear Composites
Magnitude of the total wind shear between 200hPa
and 850hPa
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North Atlantic Tropical Cyclones Cluster
AnalysisResults
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Tracks and Regression Trajectories
Mean Regression Trajectory
TRACKS
Tracks Atlantic named Tropical Cyclones 1970-2003.
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Number of TCs per cluster
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ENSO Relationship
NTC correlations
ACE correlations
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Tracks El Niño years
Tracks La Niña years
Cluster 1
Cluster 2
Cluster 3
Named Tropical Cyclones in warm/cold ENSO years
1950-2003
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Named Tropical Cyclones 1950-2003
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Atlantic Multi-Decadal Signal

• S.B. Goldenberg, C.W. Landsea, A.M. Mesta-Nuñez
  and W.M. Gray, Science 293,
• 474-478 (2001).

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Number of Major Hurricanes per cluster
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SST anomalies composite
SST composites 11/1981-12/2003
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Eastern North PacificTropical CyclonesCluster
Analysis Results
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Mean Regression Trajectories and Tracks
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ENSO Relationship
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Tracks El Niño years
Tracks La Niña years
Cluster 1
Cluster 2
Cluster 3
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Summary

• New clustering technique applied to Northern
  Hemisphere TC tracks.
• Clusters with different properties genesis and
  track regions, intensity, timing.
• In all basins clusters strongly related to ENSO
  are identified.
• Composites of large scale fields with different
  characteristics for each cluster identify the
  factors influencing the formation and movement of
  TCs in each cluster.

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SST Anomalies Composites
Main Development Region
SST and TC data for SST composites 11/81
12/2003
TCs First Positions
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Wind shear composites
NCEP Reanalysis and TC data for composites
1950-2003.
Magnitude of the total wind shear between 200hPa
and 850hPa.