Cluster Analysis of Tropical Cyclone Tracks and ENSO
Suzana J. Camargo, Andrew W. Robertson,International Research Institute for Climate Prediction,
Columbia Earth Institute, Palisades, NY
Scott J. Gaffney and Padhraic SmythDepartment of Information and Computer Science,
University of California, Irvine, CA
Outline• Introduction• Clustering Technique• Previous works on cluster analysis and tropical cyclones• Western North Pacific Results
– Mean Regression Trajectories– Tracks– Properties of main clusters– ENSO Relationship: tracks, tracks density, NTC, ACE– Composites: SST, SLP, winds, wind shear
• North Atlantic Results– Mean Regression Trajectories and Tracks– ENSO relationship– Atlantic multi-decadal signal
• Eastern North Pacific Results– Mean Regression Trajectories and Tracks– ENSO relationship
• Summary
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).
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.
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).
Western North Pacific Tropical Cyclones
Cluster AnalysisResults
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.
MEAN REGRESSIONTRAJECTORIES
TRACKS
TRACKS TROPICAL CYCLONES Western North Pacific 1983-2002
Number of TCs per Cluster
Cluster A
Landfall63% Regression
Trajectory
•67% reach typhoon intensity
FIRST POSITION DENSITY
NTC ANNUAL CYCLE
TRACK DENSITY
Cluster B
Landfall61% Regression
Trajectory
50% only reach TS intensity.
FIRST POSITION DENSITY
NTC ANNUAL CYCLE
TRACK DENSITY
Cluster C
•70% reach typhoon intensity
Landfall 7% Regression
Trajectory
FIRST POSITION DENSITY
NTC ANNUAL CYCLE
TRACK DENSITY
ENSO RelationshipNTC- Number of Tropical Cyclones ACE – Accumulated Cyclone Energy
Total ACE has a well known relationshipwith ENSO (Camargo & Sobel, 2004).
Total NTC per year is not significantlycorrelated with ENSO (e.g. Wang & Chan, 2002).
Tracks El Niño years Tracks La Niña years
Cluster A
Cluster E
Cluster G
Track Density per year: Difference El Niño and La Niña years
Full basin Cluster A
Cluster GCluster E
Mean NTC and ACE per cluster and ENSOA
A
E
E G
G
SST Anomalies Composites
TCs first positions
Regression trajectory
SST and TC data for SST composites:11/81 – 12/02
Sea Level Pressure Anomalies Composites
NCEP Reanalysis and TC data for composites: 1950-2002
Anomalous Low Level Wind Composites
Wind Shear Composites
Magnitude of the total wind shear between 200hPa and 850hPa
North Atlantic Tropical Cyclones Cluster Analysis
Results
Tracks and Regression Trajectories
Tracks Atlantic named Tropical Cyclones 1970-2003.
TRACKS
Mean RegressionTrajectory
Number of TCs per cluster
ENSO Relationship
NTC correlations
ACE correlations
Tracks El Niño years Tracks La Niña years
Cluster 1
Cluster 2
Cluster 3
Named Tropical Cyclones in warm/cold ENSO years 1950-2003
Named Tropical Cyclones: 1950-2003
SST Anomalies Composites
TCs First Positions
Main Development Region
SST and TC data for SST composites: 11/81 – 12/2003
Wind shear composites
Magnitude of the total wind shear between 200hPa and 850hPa.
NCEP Reanalysis and TC data for composites: 1950-2003.
Atlantic Multi-Decadal Signal
•S.B. Goldenberg, C.W. Landsea, A.M. Mesta-Nuñez and W.M. Gray, Science 293,474-478 (2001).
Number of Major Hurricanes per cluster
SST anomalies composite
SST composites: 11/1981-12/2003
Eastern North PacificTropical CyclonesCluster Analysis
Results
Mean Regression Trajectories and Tracks
ENSO Relationship
Tracks El Niño years Tracks La Niña years
Cluster 1
Cluster 2
Cluster 3
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.