Examining the Strength of the Hadley Cell and It

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Examining the Strength of the Hadley Cell and
Its Influence on the Strength and Displacement
of the 200 hPa East Asian Jet
Michael J. Bodner AOSC 617 31 March
2006
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Variations of East Asian Jet Stream (EAJS)
influence climate and weather across the
Asia-Pacific-America (APA) region (Yang et al.
2002)

• PNA pattern
• Closely associated with synoptic scale phenomena
  such as cyclogenesis, blocking and storm track
  activity
• More strongly linked to climate signals of APA
  than ENSO
• Intensification of the EAJS is associated with
  temperature and precipitation anomalies over
  North America
• Anomalous longitudinal and latitudinal
  displacements are mostly independent of ENSO

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Forcing mechanisms which contribute to strength
and variability of the East Asian Jet Stream

• Diabatic heating over the western tropical
  Pacific
• - can influence width, shape and
  speed of EAJS
• (Chang 2001)
• Orography and land-sea thermal contrast
• - Influence of Himalayas, Rockies
  and Andes on mean
  zonal westerlies (Bolin 1950)
• Hadley circulation
• - Observational (Krishnamurti 1961,
  Bjerknes 1966)
• - GCM Model (Hou 1995 and 1998,
  Chang 1995)
• - Reanalysis studies (Berbery 1993,
  Hou 1998)

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Some of the work done on Hadley circulation
influence on subtropical and mid latitude zonal
jet

• Bjerknes 1966 Anomalously high SSTs during
  1957-58 El Nino event contributed to a stronger
  Hadley Cell, increased northward transport of
  angular momentum and stronger than normal
  westerlies in the mid latitudes.
• Hou 1998
• GCM results indicated that
  intensification and poleward movement of the
  cross-equatorial Hadley Cell can lead to enhanced
  vertical shear of the zonal wind in the
  subtropics and midlatitudes, accompanied by a
  reduction in the meridional temperature and PV
  gradients (high zonal index)
• - A reduction of Hadley cell
  intensity is associated with increased meridional
  temperature/PV gradient (low zonal index)
• - GOES-1 Reanalysis showed similar
  results during austral winters
• ? Berbery 1993 used objectively analyzed
  ECMWF data to show that westerly zonal wind
  accelerations increase with a strenghening Hadley
  Cell over SH

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Its been demonstrated that a strong Hadley Cell
contributes to a strong zonal mean wind (u).But
is there any relationship between the strength of
the Hadley Cell and the latitudinal/longitudinal
displacement of the jet?
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200 hPa Average u-wind and Standard Deviation (m
sec-1) NCEP Reanalysis Data NDJFM 1958-2001
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DJF 1997-98 SST Anomaly over Nino 3.4 Region
(2.4)
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DJF 1980-81 SST Anomaly over Nino 3.4 Region
(-0.3)
DJF 1978-79 SST Anomaly over Nino 3.4 Region
(-0.1)
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To better depict the geometry and strength of the
Hadley cell, the divergent component (V?) of the
wind was calculated at 200 hPa.

• Using NCEP Reanalysis data, ? (chi) was obtained
  from the relationship
  (Krishnamurti 1973)
• Vector and scalar plots of ? (chi) were generated
  to better depict the shape of the western Pacific
  Hadley cell show potential areas of strong
  meridional over turning
• Standard deviations of ? (chi) and vertical plots
  of ? (chi) still need to be done

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Average Divergence of Chi (Vector and Scalar)
10-5 sec-1 NCEP Reanalysis Data NDJFM 1958-2001
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Mean Zonal Wind (200 hPa) Average Divergence of
Chi (Vector) 10-5 sec-1 NCEP Reanalysis Data
NDJFM 1958-2001
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Using Grads/GEMPAK software packages and NCEP
Reanalysis data, two additional methods of
estimating the strength of the Hadley Cell will
be attempted.
1) Estimating the maximum value of the mean
meridional streamfunction (?n) by integrating the
equation for meridional velocity from the top of
the atmosphere downward
2) Using the difference between the
upper level meridional wind and the lower
tropospheric meridional wind

Oort 1996
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The goal of the project is to use the estimated
Hadley Cell strength indicators to

• Test for correlation between the strength of the
  Hadley cell (using ?, ? and/or ?vn ) and the
  strength of the 200 hPa zonal mean wind at the
  points 30N 160W and at 45N 180W.
• Apply this procedure to examine ENSO warm and
  cold winters, both phases of PDO (1958-1978 and
  1979-1999) and significant positive/negative jet
  anomalies from ENSO neutral winters.
• Determine whether or not a pattern or prediction
  index can be identified.

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References
Berbery, E.H., 1993Intraseasonal interactions
between the tropics and extratropics in the
southern hemisphere. Journal of Atmospheric
Sciences, 50, 1950-1965. Bjerknes, J., 1966 A
possible response of the atmospheric Hadley
circulation to equatorial anomalies of ocean
temperature. Tellus., 18, 820829. Bolin, B.,
1950 On the influence of the earths orography
on the general character of the westerlies.
Tellus, 2, 184-196. Chang, E.K.M., 2001 GCM and
observational diagnosis of the seasonal and
interannual variations of the Pacific storm track
during the cool season. Journal of Atmospheric
Sciences, 58, 1784-1800. Chang, E.K.M., 1995 The
influence of Hadley circulation intensity changes
on extratropical climate in an idealized model.
Journal of Atmospheric Sciences, 52,
2006-2024. Hou, A,Y., 1998 Hadley circulation as
a modulator of the extratropical climate. Journal
of Atmospheric Sciences, 55, 2437- 2457. Hou,
A,Y., 1995 Modulation of dynamic heating in
winter extratropics associated with
cross-equatorial Hadley circulation. Journal of
Atmospheric Sciences, 52, 2609-2626. Krishnamurti,
T.N., M. Kananitsu, W.J. Koss and J.D. Lee,
1973 Tropical east-west circulations during the
northern winter. Journal of Atmospheric Sciences,
30, 780-787. Krishnamurti, T.N., 1961 The
subtropical jet stream of winter. Journal of
Atmospheric Sciences, 2, 172-191. Oort, A.H.,
J.J. Yienger, 1996 Observed interannual
variability in the Hadley circulation and its
connection to ENSO. Journal of Climate, 9,
2751-2767. Yang, Song, K.-M. Lau, K.-M. Kim,
2002 Variations of the east Asian jet stream and
Asian-Pacific-American winter climate anomalies.
Journal of Climate, 15, 306-325.
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