The ultimate test of our understanding of the working of the climate system is how well our models simulate the behavior of the climate system. Our efforts in helping to build better and better models are currently focused on diagnosing the causes of outstanding biases in the state-of-the-art climate models--Coupled General Circulation Models (CGCMs) (or Climate System Models). We are currently working with modelers at NCAR, GFDL, NASA, and IAP attempting to understand the causes of outstanding tropical biases in CGCMs: the excessive cold-tongue, the double ITCZ, etc. As few processes are not coupled, key to diagnosing the causes of biases in climate simulations by CGCMs is to evaluate the various feedbacks in the models and understand the climatic roles of feedbacks. A precise knowledge of the major feedbacks in the climate system, such as the feedbacks of water vapor and clouds, is also necessary for understanding the causes of the observed climate change and for predicting future climate.

Publications

• Wu, C., T. Zhou, and D.-Z. Sun, 2008: Atmospheric Feedbacks over the Tropical Pacific in Observations and Atmospheric General Circulation Models: An Extended Assessment. J. Climate, Submitted.
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• Zhang,T.,D.-Z. Sun, R. Neal, and P. Rasch, 2008: An Evaluation of ENSO Asymmetry in the Community Climate System Models: A View from the Subsurface. J.Climate, Submitted. Abstract / PDF

• Yu, Y., and D.-Z. Sun, 2008: Response of ENSO and the Mean State of the Tropical Pacific to Extratropical Cooling/Warming: A Study Using the IAP Coupled Model. J. Climate, Submitted.

• Wu, C., T. Zhou, R. Yu, and D.-Z.Sun, 2008: Regime behavior in the SST-cloud forcing relationships over the Pacific cold-tongue region. J. Climate, Submitted.

• Sun, D.-Z., Y. Yu, and T. Zhang, 2009: Tropical Water Vapor and Cloud Feedbacks in Climate Models: A Further Assessment Using Coupled Simulations. J. Climate, 22, 1287-1304.
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• Zhang, T., and D.-Z. Sun, 2008: What Causes the Excessive Response of the Clear-Sky Greenhouse Effect to El Nin˜o Warming in the NCAR Community Atmosphere Models? J. Geophys. Research, 113, D02108, doi:10.1029/2007JD009247.
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• Sun, D.-Z., 2007: The Role of ENSO in Regulating its Background State. In "Nonlinear Dynamics in Geosciences", pages 537-555, Springer New York, 604 pages, Edited by J. Elsner and A. Tsonis.
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• Sun, D.-Z. and T. Zhang 2006: A Regulatory Effect of ENSO on the Time-Mean Thermal Stratification of the Equatorial Upper Ocean. Geophys. Res. Lett., Vol. 33, L07710, doi:10.1029/2005GL025296.
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• Sun, D.-Z., T. Zhang, C. Covey,S. Klein, W.D. Collins, J.J. Hack, J.T. Kiehl, G.A. Meehl, I.M. Held, and M. Suarez, 2006 : Radiative and Dynamical Feedbacks Over the Equatorial Cold-tongue: Results from Nine Atmospheric GCMs. J. Climate , 19 , 4059-4074.
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• Zhang, T. and D.-Z. Sun, 2006 :Response of water vapor and clouds to El Nino warming in three NCAR models J. Geophys. Res.,111 , D17103, doi:10.1029/2005JD006700 .
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• Sun, D.-Z., 2004: The Control of Meridional Differential Heating Over the Level of ENSO activity: A Heat-Pump Hypothesis. page 71--83. In Earth's Climate: The Ocean-Atmosphere Interaction, AGU Geophysical Monograph, Vol. 147, 414 pages. Edited by C. Wang, S.-P. Xie, and J. Carton.
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• Sun, D.-Z., T. Zhang, and S.-I. Shin, 2004 : The effect of subtropical cooling on the amplitude of ENSO: a numerical study. J. Climate , 17, 3786-3798.
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• Sun, D.-Z., J. Fasullo, T. Zhang, and A. Roubicek, 2003:On the Radiative and Dynamical Feedbacks over the Equatorial Cold-tongue. J. Climate, 16. 2425-2432
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• Sun, D.-Z., 2003:A Possible Effect of An Increase in the Warm-pool SST on the Magnitude of El Niño Warming. J. Climate, 16, 185-205
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• Sun, D.-Z., C. Covey, and R.S. Lindzen, 2001: Vertical correlations of water vapor in GCMs. Geophys. Res. Lett., 28 , 259-262.
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• Fasullo, J., and D.-Z. Sun , 2001: Radiative sensitivies to tropical water vapor under all-sky conditions. J. Climate, 14, 2798-2807
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• Sun, D.-Z., 1997: El Niño: a coupled response to radiative heating? Geophys. Res. Lett., 24, 2031-2034.

• Sun, D.-Z. and Z. Liu, 1996 : Dynamic ocean-atmosphere coupling: a thermostat for the tropics. Science, 272, 1148-1150.

• Sun, D.-Z. and I.M. Held, 1996 : A comparison of modeled and observed relationships between interannual variations of water vapor and temperature. J. Climate, 9, 665-675.

• Sun, D.Z. and R.S. Lindzen, 1994 : A PV view of the zonal mean distribution of temperature and wind in the extratropical troposphere. J. Atmos. Sci., 51, 757-772.

• Sun, D.-Z. and R.S. Lindzen, 1993a : Distribution of tropical tropospheric water vapor. J. Atmos. Sci., 50, 1643-1660.

• Sun, D.-Z. and R.S. Lindzen, 1993b: Water vapor feedback and the ice age snowline record. Ann. Geophys., 11, 204-215.