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Tropical forcing for the interannual variability of the subtropical high. Pei-Hsuan Chung and Chung-Hsiung Sui Department of Atmospheric Sciences, National Central University, Jhong Li, Taiwan Tim Li Department of Meteorology and IPRC, University of Hawaii, Honolulu, Hawaii, USA. - PowerPoint PPT Presentation
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Tropical forcing for the interannual variability of the subtropical high
Pei-Hsuan Chung and Chung-Hsiung SuiDepartment of Atmospheric Sciences, National Central University,Jhong Li, Taiwan
Tim LiDepartment of Meteorology and IPRC, University of Hawaii, Honolulu, Hawaii, USA
Sui, C. -H., P. -H. Chung, and T. Li, 2007: Interannual and interdecadal variability of the summertime western North Pacific subtropical high. Geophys. Res. Lett., 34, 253 L11701, doi:10.1029/2006GL029204.
Time SeriesWNPSHI = H500 anom (120-140E, 10-30N)
OBS AnalysisOBS Analysis
Power Spectrum of WNPSH I ndex
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2
3
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Periods (Years)
Pow
er
Den
sit
y
Density
95% TEST
2.5 Yrs
3.6 Yrs
Power Spectrum of WNPSH Index
Time Filtering: 2-3-yr and 3-5-yr WNPSH Index
Shading: vertical p-velocity (Pa/s) Vectors: significant W500 (m/s)Color contours: OLR (W/m2) Black contour: H500 (unit: m)
Shading: vertical p-velocity (Pa/s) Vectors: significant W500 (m/s)Color contours: OLR (W/m2) Black contour: H500 (unit: m)
What are the key SSTA forcing dominated in 2-3-yr and 3-5-yr oscillations of the westwarding WNP subtropical
high?
Model Simulation
QTCM Model QTCM : Quasi-equilibrium Tropical Circulation
Model with a single vertical structure of temperature and moisture for deep convection
Intermediate complexity atmospheric model The model formulation makes use of the
constraints placed on the flow by deep convection, as represented by quasi-equilibrium (QE) convective parameterizations
Experiment design
Control SST Run 1958-2005 monthly mean SST to run 50
years simulations and use the middle 30 years results
Prescribe SSTA Run MJJA : Add (High-Low) composite SSTA
in some key regions JFMA and SOND : Climate SST as CTRL Prescribe SSTA Run - Control SSTA Run
2-3-yr oscillation
MJJA SSTA
(High-Low) Comp
CEP RunMC Run
MC Run
CEP Run
Total Run
WNP Run
IO+EP Run
3-5-yr oscillation
MJJA SSTA
(High-Low) Comp
WNP Run
EP+IO Run
Total Run
Discussion
2-3-yr oscillation ~ Total run 3-5-yr oscillation ~ WNP run
(local cold SSTA)
Using “heating” instead of SSTA GCM models
