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The research advances of the South Asian High – one of the most important members of the Asian Monsoon system. Reporter: He Jinhai ( [email protected] ) Nanjing University of Information Science & Technology (NUIST) - PowerPoint PPT Presentation
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The research advances of the South Asian High – one of the most important members
of the Asian Monsoon system
The research advances of the South Asian High – one of the most important members
of the Asian Monsoon system
Reporter: He Jinhai ([email protected])
Nanjing University of Information Science & Technology (NUIST)
Contributor: Chen Longxun, Liu yi, Wang Yuenan, Liu Boqi, Xu Kang, Shu Si
July 2010
Outlines
Introduction
The splitting and rebuilding process of the South Asian High (SAH) from April to May
Relationship between the Atmospheric Heat Source (AHS) over the eastern plateau and the SAH during summer
Relationship between the Ozone and the SAH zonal oscillation (a case study)
Summary and discussion
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The climatology (1948-2007) streamline (top and middle) and moisture transport integrated from 1000hPa to 300hPa (bottom, vector, units: kg·m-1·s-1, the magnitude greater than 150 is shaded) in January
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Winter A
The climatology (1948-2007) streamline (top and middle) and moisture transport integrated from 1000hPa to 300hPa (bottom, vector, units: kg·m-1·s-1, the magnitude greater than 150 is shaded) in July
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Summer
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1. SAH seasonal migration and its possible mechanism
1.1 Characteristics(1) The annual cycle characteristics (Zhu F. K., 1980; He J. H. et al., 2003)(2) The northward propagation of the SAH ridge line (Luo S. W., et al., 1982)(3) The winter mode and summer mode of the SAH (Qian Y. F., et al., 2002)(4) The splitting and rebuilding process of the SAH from April to May (He J. H. et al., 2006;
Wang L. J. et al., 2007; Liu B. Q. et al., 2009)
1.2 Possible mechanisms(1) The heating effect of the Tibetan Plateau (Ye D. Z. et al., 1974; Krishnamurti et al., 1973;
Huang R. H., 1985; Ding Y. H. et al., 1984; Wu A. M. et al., 1997; Zhao P. et al., 2001)(2) The “heat preference” of the SAH (Ye D. Z. et al., 1957; Qian Y. F. et al., 2002; Zhang J. J.
et al., 1984; Zheng Q. L., et al., 1993; Jian M. Q. et al., 2001)(3) The complete form of vertical vorticity equation and the themal adaptation theory (Wu G.
X. et al., 2003, 2008; Liu Y. M., et al., 2004)
Introduction
The evolution of the climatology (1948-2007) streamline on 150hPa from Jan to Dec
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The rapid westward progression of SAH from April to May is
actually the process of splitting and rebuilding.
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2. SAH zonal oscillation and its possible mechanism
(1) The west mode (Tibetan Mode) and the east mode (Iranian Mode) of the SAH (Tao S. Y. et al., 1964; Luo S. W. et al., 1982; Li W. L. et al., 1991; Zhang Q., et
al., 2002)
(2) Possible mechanism (a) Thermal influence (Liu F. M., et al., 1981; Zhang Q. et al., 1999, 2002) (b) Interaction among different circulation systems (Sun G. W., et al., 1977; Zhu B. Z. et
al., 1981; Lu L. H. et al., 1985) (c) Zonal asymmetric instability theory (Liu Y. M. et al., 2003)
Introduction
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3. SAH interannual variability and its relationship with the rainfall in China
(1) The relationship between the SAH interannual variability and the SSTA (Zhang Q., et al., 2000; Tan J. et al., 2005; Li C. Y., et al., 2001; Yang H. et al., 2005)
(2) The connection between the SAH and the flood-and-drought distribution in China (Chen L. X. et al., 1980; Zhang Q. Y. et al., 2006; Lu J. Z. et al., 1982; Zhu Q. G. et al.,
1985; Guo Q. Y., 1985; Sha W. Y., 1985; Xu X. D. et al., 1992; Wang A. Y. et al., 1993; Zhang Y. C. et al., 2002)
(3) The relationship between the SAH and the rainy band propagation in China (Zhang J. Y. et al., 1987; Zhu F. K. et al., 1987; Liu M. et al., 2007; Qian Y. F. et al.,
2002; Zhang Q. Y. et al., 2003)
(4) The linkage between the SAH and the Subtropical High (Tao S. Y. et al., 1964; Zhang Q. et al., 2002)
Introduction
Outlines
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Introduction
The splitting and rebuilding process of the South Asian High (SAH) from Apr to May
Relationship between the Atmospheric Heat Source (AHS) over the eastern plateau and the SAH during summer
Relationship between the Ozone and the SAH zonal oscillation (a case study)
Summary and discussion
The climatology (1975-2005) streamline on 150hPa from the 22nd to 30th pentad (the red line is the ridge line)
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The SAH splitting & rebuilding processes can be divided
into 3 phases:
1. pre-splitting phase: 19th-22nd pentad;
2. splitting phase: 23rd-25th pentad;
3. rebuilding phase: 26th-27th pentad.
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Spatial distribution of barotropic (baroclinic) modes in Figs.a-c (d-f) for the phased stream fields relating to the SAH splitting and rebuilding processes, with pre-splitting in a, d, splitting phase in b, e and rebuilding phase in c, f. The shading represents baroclinic vorticity in d-f.
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pre-splitting phase
splitting phase
Rebuilding phase
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Barotropic modes Baroclinic modes
Left column: the height-longitude cross section of the wind (vectors), the ascending motion (shading, 10-2 pa-1) and the Q1 (contours, K day-1) along 90o-110oE in terms of the three different phases of the SAH splitting and rebuilding processRight column: the height-latitude cross section of the wind (vectors), the divergence (shading, 10-6 s-1) and the Q1 (contours, K day-1) along 5o-20oN
pre-splitting phase
splitting phase
Rebuilding phase
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)1(1
z
Qf
t z
z
)2(1
z
Qfv
z
z
Sketch map of the SAH establishing processes on the ICP from April to May
Weak convection
Anticyclone on the West Pacific
SAH splitting
Convectionreinforcing
SAH rebuilding
Deepconvection
The northerly on the top
The southerlyon the bottom
ICPConvection
SouthAsia High
Phase I(19P-22P)
Phase II(23P-25P)
Phase III(26P-27P)
z
Qf
t z
z
1
z
Qfv
z
z
1
28P
SCSM Onset
BOBSMOnset
Stationary ResponseNon-stationary Response13
How does the SAH move onto the Tibetan Plateau?(climatology 100hPa streamline field in June)
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SAH displaces onto the Tibetan Plateau on the 33rd pentad
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Outlines
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Introduction
The splitting and rebuilding process of the South Asian High (SAH) from Apr to May
Relationship between the Atmospheric Heat Source (AHS) over the eastern plateau and the SAH during summer
Relationship between the Ozone and the SAH zonal oscillation (a case study)
Summary and discussion
Computational Method of the Atmospheric Heat Source (AHS)
In which θ is potential temperature, ω is vertical velocity, V is horizontal velocity, R is constant of dry air, Cp is specific heat.
Positive calculation needs the data of condensation heating, sensible heat and vertical transfer and radiation balance, but we pay primary attention to the variation of the total AHS. Therefore, inverse calculation is adopted to obtain the daily AHS in the entire troposphere.
pcR /
Inverse calculation (Yanai et al., 1992):
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PP
PTV
t
TCQ p
01
+ -
Correlation between AHS over the eastern plateau and AHS over other areas from 1971 to 2000
The shaded areas are statistically significant at the 5% level.The thick dashed line denotes the wavetrain.
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500hPa100hPa
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CC
100hPa
Difference fields of circulations between intense and weak AHS years over the eastern plateau (intense years minus weak years)
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500hPa
Correlation between AHS over the eastern plateau and vorticity.The shaded areas are statistically significant at the 5% level.
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South Asian High (SAH) and West Pacific Subtropical High (WPSH) move in the horizontally-opposite directions in
terms of interannual variation
100hPa
100hPa
500hPa
500hPa
Composite geopotential height (gpm) in the intense and weak years of AHS over the eastern plateau
Intense years
Weak years
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Move toward each other
Back away
Outlines
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Introduction
The splitting and rebuilding process of the South Asian High (SAH) from Apr to May
Relationship between the Atmospheric Heat Source (AHS) over the eastern plateau and the SAH during summer
Relationship between the Ozone and the SAH zonal oscillation (a case study)
Summary and discussion
Tropospheric Ozone
Stratospheric Ozone
TOZ
SCO
TCO
Total Ozone
Integrated from land surface to
the top of atmosphere
Tropospause of NCEP
Vertical classification of Ozone
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Relationship between Ozone Low Center over TP
in summer and zonal oscillations of SAH
TOZ
July 16th,2006
Total Ozone (TOZ)Low Center
(shade)
Center of SAHat the level of 100hPa
geopotential height(contour)
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West mode East mode
Choosing typical cases(July, 2006)
Choosing typical cases(July, 2006)
July,23 to 30July,23 to 30
July,14 to 20July,14 to 20
West modeWest mode
East modeEast mode
Relationship between Ozone Low Center over TP in summer and zonal oscillations of SAH
Total Ozone(TOZ)
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West mode East mode
West mode East mode
SCO
TCO
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South Asian High (SAH)
West modeweak
East modestrong
Magnitude Weak Strong
Position Over the west of TP Over the east of TP
Areas Small Large
Relationship between the South Asian High and the Ozone (TOZ, TCO, SCO) Low Center
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Possible mechanism: When the SAH appears the east (west) mode, the air with less Ozone from low latitudes is transported into the middle troposphere over the east (west) of the TP by strong (weak) summer monsoon currents, the convergence and the ascending is also strong (weak), in turn the Ozone low center is strong (weak).
Outlines
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Introduction
The splitting and rebuilding process of the South Asian High (SAH) from Apr to May
Relationship between the Atmospheric Heat Source (AHS) over the eastern plateau and the SAH during summer
Relationship between the Ozone and the SAH zonal oscillation (a case study)
Summary and discussion
Summary and discussion The South Asian High (SAH) moves onto the Indo-China Peninsula
via the splitting-rebuilding process. The process actually is a substitution that a high-level anticyclone (HLA) being generated and strengthened over the Peninsula and the original HLA getting relatively weakened over waters east of the Philippines. And the principal triggering factor is the changes in the South-Asian atmospheric diabatic heating regime.
SAH and West Pacific subtropical high move in the horizontally-opposite directions in terms of interannual variation, for which AHS over the eastern plateau seems to be thermodynamically responsible.
The oscillation of SAH in east- and west-directions maybe an important factor of the Ozone low center variation.
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