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Slide 1: 

First satellite cloud climatology (January 1967-70) Why is the ITCZ displaced in the Northern Hemisphere? Why the west is warmer than the east in the Eq Pacific & Atlantic? Lecture 1 Mean State of Tropical Ocean Climate Shang-Ping Xie IPRC, University of Hawaii Coupled feedback between the ocean and atmosphere

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Mitchell and Wallace (1992, JC)

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1656 - 1742 “... Halley ... had the genius to recognise the even greater mathematical genius of Newton, to urge him to write the Principia Mathematica, and then pay for the costs of publication out of his own pocket... “ --Chapman “It is not the work of one, nor of few, but of a multitude of Observers, to bring together the experience required to compose a perfect and complete History of these Winds.” -- Edmond Halley (1686)

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Halley 1686 Eq Calm and Tornado Halley wrote about the ITCZ: “it were improper to say there is any Trade Winds, or yet a Variable; for it seems condemned to perpetual Calms, attended with terrible Thunder and Lightning, and Rains so frequent, that our Navigators from thence call this part of the Sea the Rains”.

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Hybrid Coupled Atmospheric GCM (HaGCM) CCSR/NIES AGCM T21L20; Annual-mean insolation Modified Zebiak-Cane ocean model h=h(x, y) h(x, y)

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Continental asymmetry excites a westward-traveling coupled wave front. Xie and Saito, J. Climate (2001)

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Westward control by continental geometry Xie & Saito (2001, J. Clim ) Land SST Land

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Westward control theory TN TS Eq V WES wave equation s: coupled coefficient

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Case 1: Zonally uniform Case 2: Steady state WES wave equation , Xie (1996, JAS)

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Philander et al. (1996, JC)

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Coupled feedback Continental geometry Northward-displaced ITCZ Equatorial annual cycle Weakened interhemispheric coherence of climate variability January 1967-70 Summary

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www.scotese.com It still moves. Drifting Continents

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Earth Climate: The Ocean-Atmosphere Interaction an AGU Geophysical Monograph C. Wang, S.-P. Xie, & J. A. Carton, Editors   Table of Contents Preface   A Global Survey of Ocean-Atmosphere Interaction and Climate Variability Chunzai Wang, Shang-Ping Xie, and James A. Carton   Theme I: Pacific Climate Variability Theme II: Tropical Atlantic Climate Variability Theme III: Indian Ocean Climate Variability Theme IV: Tropical-Extratropical Interaction Theme V: Cross-Basin Issues

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100 27 Comparative Climatology SST & Precip Z20 60 200 100

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Eq N Equatorial upwelling Walker Cell Bjerknes Feedback Easterly wind Eq. upwelling Thermocline rises EP cooling & reduced convection

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Effect of cross-equatorial wind Xie (1998, JC) wind Southerly wind Upwelling south of the equator Downwelling to the north Increased SST contrast across Eq Upwelling feedback Formation of equatorial front Chang & Philander (1994)

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Stronger cold tongue in a latitudinally asymmetric climate Land SST Land SST (x) on the equator in a coupled model I II I + II III

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SST Standard Deviation Equatorial mode emerges as a common feature of all tropical oceans. > 0.6 > 1.0 Pacific (70-80s): El Nino at 3-5 years intervals; strong; phase locked to December Atlantic (80s): weak and short but frequent; limited to June-September Indian (’99): infrequent and limited to a brief window of July-November

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Biases in tropical simulations by global coupled GCMs: Model climate too symmetrical about the equator Consequences Poor seasonal cycle in the equatorial Pacific and Atlantic; Distorted mean state  distorted ENSO (e.g., amplitude, spatial structure, and seasonality  teleconnection within and out of the tropics); An issue that receives little attention in applied fields such as global warming, paleoclimate, biochemical and carbon cycle modeling.

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CCSR/NIES/F CGCM OBS Cloud Radiative Forcing

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Coupled Model SST biases: ‘too cold’ tongue warm subtropical NE, SE Pac, SE Atl (Sperber et al. 2003)

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COADS annual mean deep cloud low cloud low cloud

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SST, rain & wind Basin-wide influence of SE Pacific low cloud deck via westward control (Philander et al. 1996; Ma et al. 1996; Kimoto & Shen 1997) Control Cloud-deck Exp

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Inversion T qc -QLW Profiles at 10ºS, 90ºW Similar temperature to SST Shield sunlight strong cooling to ocean & atmos Stratus: Important regulator of Earth climate Increased low cloud Increased stability Reduced SST Low cloud-SST feedback: Important in the subtropics Philander et al. (1996)

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Vertical cross-sections Cloud water & qv along 10ºS

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Bjerknes feedback in the zonal direction Cold tongue and its variability WES feedback in the meridional direction  Northward displaced ITCZ & variability Cloud-SST feedback (low cloud; convective cloud; solar & longwave radiation) Upwelling-wind feedback across the equator Air-Sea Feedbacks Summary

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Interaction or forced response? Atmospheric response Ocean response ? ?

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ITCZ’s northward displacement Annual cycle on the equator

The IPRC-RegCM (Y. Wang et al. 2003) : 

The IPRC-RegCM (Y. Wang et al. 2003) Cloud microphysics (Wang 2001) Mass flux cumulus parameterization of Tiedtke (1989), with CAPE closure of Gregory et al. (2000) Hydrostatic, primitive eqs. (0.5x0.5o; 28 -levels) Radiation transfer of Edwards and Slingo (1996) BATS land surface model (Dickinson et al. 1993) Cloud amount following Xu and Randall (1996) E- turbulence closure scheme for subgrid vertical mixing (Etling 1988)

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Model domain and topography Integration: 29 July to 31 October 1999 Lateral boundary conditions: NCEP/NCAR reanalysis Lower boundary conditions: Weekly Reynolds SST

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Surface wind & Precipitation Model QuikSCAT & TMI Observations Y. Wang et al., MWR (2003)

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Control – No-Andes Surface solar radiation & wind Xu et al., J. Clim. (2003)

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Precipitation (April and May,1999) TMI Obs

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Northward-displaced ITCZ: Climatic axis of symmetry Tropical variability and its teleconnection into the extratropics January 1967-70 Steep Andes

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T42 1/12o

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