The Relationship Between ENSO and Typhoon Activity

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The Relationship Between ENSO and Typhoon Activity

• Suzana J. Camargo1 and Adam H. Sobel1,2
• (1) International Research Institute for Climate
  Prediction,
• Columbia Earth Institute, Palisades, NY
• (2) Department of Applied Physic and Applied
  Mathematics,
• Department of Earth and Environmental Sciences,
• Columbia University, New York, NY

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Relationship of ENSO and typhoon activity

• Investigated by many authors main focus number
  of tropical cyclones (Atkinson, 1977 Ramage and
  Hori, 1981 )
• Nonlinear relation of the number of tropical
  cyclones and ENSO (Chan, 1985 Chen et al.,
  1998).
• Mean genesis location southeastward
  displacement in El Niño years (Chan, 1985 Chia
  and Ropelewski, 2002).
• Lifetime of typhoons increases in El Niño years
  (Wang and Chan, 2002).
• Greater number of Central Pacific tropical
  cyclones, some move into the WNP (Chu and Wang,
  1997 Chu, 2002).
• 1997 strongest El Niño of the century, WNP had
  23 typhoons (2nd largest on record), with a
  record number of super-typhoons (11) (Lander and
  Guard, 2001).

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Objectives

• What is the relationship of ENSO with typhoon
  intensity (seasonal time scale) ?
• S.J. Camargo and A.H. Sobel, Western North
  Pacific Tropical Cyclone Intensity and ENSO,
  submitted to J. Climate (June, 2004).
• How do WNP tropical cyclones influence the large
  scale environment (short time scale)?
• Why is the annual number of TCs in the WNP so
  nearly constant (274)? Is there a negative
  feedback from one TC on genesis of later ones
  (expressed either through climatology or
  short-timescale interactions)?
• Do tropical cyclones have an ACTIVE role on ENSO
  (short time scale)?
• A.H. Sobel and S.J. Camargo, Influence of
  western North Pacific tropical cyclones on their
  large-scale environment, submitted to J.
  Atmospheric Sciences (June, 2004).

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ACE Accumulated Cyclone Energy

• Treat TCs as a climate variable.
• Sum of squared maximum
• wind speeds of all storms existing at a given
  time seasonal, weekly,(Bell et al., 2000) .
• Based on JTWC best track dataset on the period
  1950-2002.
• Measure of tropical cyclone activity number,
  intensity and lifetime.

ACE Weekly Climatology
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SEASONAL TIME SCALE
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ACE per year and NINO3.4 JASO
ACE PER YEAR
R0.70 (1970-2002)
NINO3.4 JASO
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LAG CORRELATIONS ACE and NINO INDICES
SCATTER PLOT ACE NINO3.4
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Mean ACE per TC Category
Tropical Cyclones Lifetimes
Tropical Storms
Intense Typhoons
Typhoons
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Summary

• El Niño years - WNP tropical cyclones have
  longer lifetimes, more intense (more cat. 3-5
  TCs, fewer TSs).
• La Niña years short lived, weaker TCs (many do
  not reach typhoon intensity).
• Relationship ACE NINO significant for various
  lags.
• Contribution for ACE-ENSO relationship
  lifetime, intensity, number.

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On the short time scale

• Lag-correlate and lag-regress weekly anomalous
  ACE against large-scale variables SST
  (Reynolds) winds, atmospheric temperature,
  moisture (NCEP/NCAR), OLR (NOAA)
• Correlations are low, but statistically
  significant (gt95) because ACE autocorrelation
  time lt 1 week and sample size is large.

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850 hPa Vorticity
Week -2
Week -1
Week 0
Week 1
Week 2
LAG REGRESSION ACE VORTICITY 850hPa
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OLR
Week -2
Week -1
Week 0
Week 1
Week 2
LAG REGRESSION ACE OLR
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SST
Week -2
Week -1
Week 0
Week 1
Week 2
LAG REGRESSION ACE SST
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Week -2
Week -1
Week 0
Week 1
Week 2
LAG REGRESSION ACE Surface Zonal Winds
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Equatorial Time-Longitude Hovmoeller
lag-regression plots over long timescale
Zonal wind
SST
Week 15
Week 0
Week -15
Assume week 0 occurs in peak TC season (JASO).
The El Nino is building, with help from the TCs.
The intraseasonal ringing is presumably MJO
influence.
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Week -2
Week -1
Week 0
Week 1
Week 2
Short-timescale SST changes (lag-regress SST on
weekly ACE, subtract 5-week mean)
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Coupled TC-ENSO dynamics a positive feedback
(strong form of the hypothesis)

• During peak TC season as El Niño develops, more
  intense tropical cyclones, shifted towards the
  dateline and the equator.
• More intense cyclones lead to stronger equatorial
  westerlies, warming SST.
• The westerlies/SST warming can occur far to the
  east, presumably transmitted by atmospheric
  Kelvin waves
• El Niño is intensified

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TC self-regulation, negative feedbacks

• SST reduction seen under main storm track, as
  expected.
• Atmospheric cooling and drying found over
  maritime continent Philippine sea regions which
  overlaps with storm track. Will this influence
  further TC development?

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EXTRA SLIDES
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NUMBER OF TROPICAL CYCLONES
NUMBER OF TROPICAL STORMS
NUMBER OF TYPHOONS
NUMBER OF INTENSE TYPHOONS
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Week -2
Week -1
Week 0
Week 1
Week 2
LAG REGRESSION ACE Column Water Vapor
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Week -2
Week -1
Week 0
Week 1
Week 2
LAG REGRESSION ACE Temperature