Bimodality in the Vertical Structure of Tropical Diabatic Heating

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Bimodality in the Vertical Structure of Tropical
Diabatic Heating

• Chidong Zhang
• RSMAS, University of Miami
• In collaboration with
• Samson Hagos, Wei-Kuo Tao, Steve Lang , Yukari
  Takayabu,
• Shoichi Shige, and Masaki Katsumata
• BIRS Conference on Multiscale Processes in the
  Tropics
• April, 27- May 1, 2009
• Banff, Alberta
• Canada

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Derive Q1 from in situ Observations
From sounding data (Yanai et al. 1973)
From radar data (Houze 1983)
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Idealized Tropical Meso-Scale Latent Heating
Profiles
Schumacker et al. (2008)
Premise Diabatic heating profiles directly
relevant to the tropical large-scale circulation
are aggregates of heating profiles associated
with different types of cloud systems.
Hartmann et al (1984) Mapes and Houze (1995)
Schumacher et al. (2004)
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• Questions
• What are the structure and evolution of
  prevailing diabatic heating profiles directly
  relevant to the tropical large-scale circulation?
• How do the tropical large-scale atmospheric
  circulations respond to the prevailing heating
  profiles?
• What are the roles of heating profiles in the
  MJO?

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Sounding Data Sources
with help from Paul Ciesielski, Steve Esbensen,
Richard Johnson, Masaki Katsumata, Yasu-Masa
Kodama, Steve Kruger, Wei-kuo Tao, Wen-wen Tung,
Xiaoqing Wu, Michel Yanai, Xiping Zeng, and
Minghua Zhang
Marshal Islands (Yanai et al 1973) Winter MONEX
(Johnson and Young 1983) AMEX (Frank and McBride
1989) BOMEX (Nitta and Esbensen 1974) TAMEX
(Johnson and Bresch 1991)
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TOGA COARE Q1
mean
meanstd dev
EOF2
REOF1
REOF2
EOF1
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TOGA COARE Q1 Time Series
Original
Reconstructed from the first two REOF modes
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original
REOF12
REOF1
REOF2
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Combined REOF Analysis
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6-hourly and daily data
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6-hourly
daily
6-hourly and daily data
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Latent Heating Profiles 15S 15N
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Latent Heating Profiles (mean standard
deviation) 15S 15N
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Probability Distribution Function as a Function
of Height
TRMM Storm Height (30S-30N)
Maximum Q1 from the soundings
Short and Naramura 2000
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A linear, steady-state model (nondimensionalized)
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mean
A
B
C
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A
B
C
A
B
C
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Spectra of REOF PCs for TRMM Latent Heating
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Composite heating for eight phases defined by the
two leading HSVD modes for CSH based on its two
leading REOF modes combined (left) and overlaid
(right).
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Composite heating for eight phases defined by the
two leading HSVD modes for CSH using (left) its
two leading REOF modes plus the time mean and
(right) the original data.
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90E
120E
150E
Lin et al (2004)
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(Wu 2003)
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Zhang and Mu (2005)
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Zhang and Mu (2005)
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A GCM experiment (Li et al. 2009) R42L9 Radiation
scheme Slingo et al (1996) Cumulus scheme
Manabe et al. (1965) Boundary layer Holtslag and
Boville (1993) Land surface Xue et al. (1991)
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Summary

• Tropical large-scale diabatic (and latent) heat
  profiles are ubiquitously dominated by two modes
  deep and shallow, independent of location and
  data sources (soundings, TRMM retrievals, global
  reanalyses)
• These two modes define three prevailing
  large-scale diabatic heating profiles that evolve
  in a sequence of bottom, middle, and top heavy
  structures
• The large-scale vertical overturning circulations
  responding to the three prevailing heating
  profiles are of multi-cell structures
• Low-level, bottom-heavy heating appears to be
  essential to the MJO.

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Questions

• What are the physical/dynamical reasons for the
  two dominant heating modes? Or are they simply
  statistical artifacts?
• Are the two dominant modes of heating profiles
  related in any way to the bimodal distributions
  of heating peaks and precipitation echo height?
• Which one is more fundamental to the MJO,
  low-level moistening or low-level heating?
• Is the multi-scale interaction in horizontal
  (synoptic vs. planetary) or vertical (shallow vs.
  deep) more fundamental to the MJO?