Bretherton Christopher S.

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Christopher S.

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  • Article
    The Community Climate System Model version 3 (CCSM3)
    (American Meteorological Society, 2006-06-01) Collins, William D. ; Bitz, Cecilia M. ; Blackmon, Maurice L. ; Bonan, Gordon B. ; Bretherton, Christopher S. ; Carton, James A. ; Chang, Ping ; Doney, Scott C. ; Hack, James J. ; Henderson, Thomas B. ; Kiehl, Jeffrey T. ; Large, William G. ; McKenna, Daniel S. ; Santer, Benjamin D. ; Smith, Richard D.
    The Community Climate System Model version 3 (CCSM3) has recently been developed and released to the climate community. CCSM3 is a coupled climate model with components representing the atmosphere, ocean, sea ice, and land surface connected by a flux coupler. CCSM3 is designed to produce realistic simulations over a wide range of spatial resolutions, enabling inexpensive simulations lasting several millennia or detailed studies of continental-scale dynamics, variability, and climate change. This paper will show results from the configuration used for climate-change simulations with a T85 grid for the atmosphere and land and a grid with approximately 1° resolution for the ocean and sea ice. The new system incorporates several significant improvements in the physical parameterizations. The enhancements in the model physics are designed to reduce or eliminate several systematic biases in the mean climate produced by previous editions of CCSM. These include new treatments of cloud processes, aerosol radiative forcing, land–atmosphere fluxes, ocean mixed layer processes, and sea ice dynamics. There are significant improvements in the sea ice thickness, polar radiation budgets, tropical sea surface temperatures, and cloud radiative effects. CCSM3 can produce stable climate simulations of millennial duration without ad hoc adjustments to the fluxes exchanged among the component models. Nonetheless, there are still systematic biases in the ocean–atmosphere fluxes in coastal regions west of continents, the spectrum of ENSO variability, the spatial distribution of precipitation in the tropical oceans, and continental precipitation and surface air temperatures. Work is under way to extend CCSM to a more accurate and comprehensive model of the earth's climate system.
  • Article
    Ocean–cloud–atmosphere–land interactions in the southeastern Pacific : the VOCALS Program
    (American Meteorological Society, 2014-03) Mechoso, C. R. ; Wood, R. ; Weller, Robert A. ; Bretherton, Christopher S. ; Clarke, A. D. ; Coe, Hugh ; Fairall, Christopher W. ; Farrar, J. Thomas ; Feingold, Graham ; Garreaud, R. ; Grados, Carmen ; McWilliams, James C. ; de Szoeke, Simon P. ; Yuter, Sandra ; Zuidema, Paquita
    The present paper describes the Variability of the American Monsoon Systems (VAMOS) Ocean–Cloud–Atmosphere–Land Study (VOCALS), an international research program focused on the improved understanding and modeling of the southeastern Pacific (SEP) climate system on diurnal to interannual time scales. In the framework of the SEP climate, VOCALS has two fundamental objectives: 1) improved simulations by coupled atmosphere–ocean general circulation models (CGCMs), with an emphasis on reducing systematic errors in the region; and 2) improved estimates of the indirect effects of aerosols on low clouds and climate, with an emphasis on the more precise quantification of those effects. VOCALS major scientific activities are outlined, and selected achievements are highlighted. Activities described include monitoring in the region, a large international field campaign (the VOCALS Regional Experiment), and two model assessments. The program has already produced significant advances in the understanding of major issues in the SEP: the coastal circulation and the diurnal cycle, the ocean heat budget, factors controlling precipitation and formation of pockets of open cells in stratocumulus decks, aerosol impacts on clouds, and estimation of the first aerosol indirect effect. The paper concludes with a brief presentation on VOCALS contributions to community capacity building before a summary of scientific findings and remaining questions.