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response to Arctic sea ice loss using the common SOM framework. e. Atmosphere-only model experiments with prescribed boundary conditions We also conducted a set of experiments using CCSM4 configured with only the atmosphere and land components active (e.g., CAM4–CLM4): SSTs and sea ice concentration and thickness are specified as a lower boundary condition following the Atmospheric Model Intercomparison Project (AMIP) convention. In these experiments, termed ICE21_AMIPG_Q21 and ICE21_AMIPG_Q20, global
response to Arctic sea ice loss using the common SOM framework. e. Atmosphere-only model experiments with prescribed boundary conditions We also conducted a set of experiments using CCSM4 configured with only the atmosphere and land components active (e.g., CAM4–CLM4): SSTs and sea ice concentration and thickness are specified as a lower boundary condition following the Atmospheric Model Intercomparison Project (AMIP) convention. In these experiments, termed ICE21_AMIPG_Q21 and ICE21_AMIPG_Q20, global
Antarctica, respectively, and so changes in the boundary layer/surface fluxes at this time are important for modifying the local baroclinicity, which acts to intensify the individual cyclones comprising the ASL. It is therefore not surprising to see the greatest impacts on ASL intensity being dependent upon time-varying conditions of extratropical SSTs and sea ice at these times of the year. In the other seasons, the lack of significant differences near West Antarctica in the center column of Fig. 6
Antarctica, respectively, and so changes in the boundary layer/surface fluxes at this time are important for modifying the local baroclinicity, which acts to intensify the individual cyclones comprising the ASL. It is therefore not surprising to see the greatest impacts on ASL intensity being dependent upon time-varying conditions of extratropical SSTs and sea ice at these times of the year. In the other seasons, the lack of significant differences near West Antarctica in the center column of Fig. 6
Atlantic Ocean, with zonally reentrant boundary conditions at Drake Passage latitudes to permit a representative Antarctic Circumpolar Current (ACC) flow. Within these boundaries the domain is deformed laterally to fit a 60°-wide sector with matching conditions set at the periodic boundaries ( Fig. 1 ). The Modular Ocean Model, version 5 (MOM5; Griffies 2012 ), provides the ocean component of the model and is coupled to the GFDL sea ice simulator (SIS; Winton 2000 ). Version 2 of CORE phase 2 (CORE2v
Atlantic Ocean, with zonally reentrant boundary conditions at Drake Passage latitudes to permit a representative Antarctic Circumpolar Current (ACC) flow. Within these boundaries the domain is deformed laterally to fit a 60°-wide sector with matching conditions set at the periodic boundaries ( Fig. 1 ). The Modular Ocean Model, version 5 (MOM5; Griffies 2012 ), provides the ocean component of the model and is coupled to the GFDL sea ice simulator (SIS; Winton 2000 ). Version 2 of CORE phase 2 (CORE2v
only the SST boundary conditions are modified: ATL3W , to assess the impact of positive (or warm) ATL3 events. For this experiment the pattern of monthly SST anomalies associated with ATL3, as determined through monthly regressions, is superimposed on the background climatology (see Fig. A1 for SST forcing). To avoid unrelated atmospheric responses beyond the regions of interest, the superimposed SST anomalies were constrained to the Atlantic and Pacific Oceans between 15°N and 25°S. Linear
only the SST boundary conditions are modified: ATL3W , to assess the impact of positive (or warm) ATL3 events. For this experiment the pattern of monthly SST anomalies associated with ATL3, as determined through monthly regressions, is superimposed on the background climatology (see Fig. A1 for SST forcing). To avoid unrelated atmospheric responses beyond the regions of interest, the superimposed SST anomalies were constrained to the Atlantic and Pacific Oceans between 15°N and 25°S. Linear
suitable for El Niño-flavor simulations ( Wilson et al. 2014 ). This investigation tailors the lower boundary conditions [global SSTs and sea ice concentrations (SICs)] to match various observed El Niño events, which are prescribed using a dataset designed for uncoupled CAM simulations ( Hurrell et al. 2008 ; available at http://cdp.ucar.edu/MergedHadleyOI ). This dataset synthesizes the monthly mean Hadley Centre Sea Ice and SST dataset version 1.1 (HadISST1) ( Rayner et al. 2003 ) with version 2 of
suitable for El Niño-flavor simulations ( Wilson et al. 2014 ). This investigation tailors the lower boundary conditions [global SSTs and sea ice concentrations (SICs)] to match various observed El Niño events, which are prescribed using a dataset designed for uncoupled CAM simulations ( Hurrell et al. 2008 ; available at http://cdp.ucar.edu/MergedHadleyOI ). This dataset synthesizes the monthly mean Hadley Centre Sea Ice and SST dataset version 1.1 (HadISST1) ( Rayner et al. 2003 ) with version 2 of
atmospheric boundary-layer conditions in a semi-arid basin of western Canada . J. Hydrol. , 517 , 949 – 962 , doi: 10.1016/j.jhydrol.2014.06.010 . Jeong , J. H. , B. M. Kim , C. H. Ho , and Y. H. Noh , 2008 : Systematic variation in wintertime precipitation in East Asia by MJO-induced extratropical vertical motion . J. Climate , 21 , 788 – 801 , doi: 10.1175/2007JCLI1801.1 . Jin , F. , and B. J. Hoskins , 1995 : The direct response to tropical heating in a baroclinic atmosphere
atmospheric boundary-layer conditions in a semi-arid basin of western Canada . J. Hydrol. , 517 , 949 – 962 , doi: 10.1016/j.jhydrol.2014.06.010 . Jeong , J. H. , B. M. Kim , C. H. Ho , and Y. H. Noh , 2008 : Systematic variation in wintertime precipitation in East Asia by MJO-induced extratropical vertical motion . J. Climate , 21 , 788 – 801 , doi: 10.1175/2007JCLI1801.1 . Jin , F. , and B. J. Hoskins , 1995 : The direct response to tropical heating in a baroclinic atmosphere
to seasonally varying climatologies. We refer to these first two experiments together as the Ozone ensemble. The remaining four ensembles use common SST and sea ice concentration lower boundary conditions: Observed time-varying tropical SSTs are prescribed over 28°N–28°S, and a seasonally varying climatology for SSTs and sea ice concentrations is used poleward of 35°. Between 28° and 35° latitude in both hemispheres, the SST anomalies are tapered by adding damped anomalies (linearly weighted by
to seasonally varying climatologies. We refer to these first two experiments together as the Ozone ensemble. The remaining four ensembles use common SST and sea ice concentration lower boundary conditions: Observed time-varying tropical SSTs are prescribed over 28°N–28°S, and a seasonally varying climatology for SSTs and sea ice concentrations is used poleward of 35°. Between 28° and 35° latitude in both hemispheres, the SST anomalies are tapered by adding damped anomalies (linearly weighted by
concentration. For our simulations, such boundary conditions are prescribed for 27 yr from January 1979 to December 2005. In this study we focus on December–February (DJF), the boreal winter season in which the MJO and its teleconnection to the extratropics are the most pronounced. Identical settings are used except for the choice of convective parameterization schemes. One simulation uses the default shallow ( Park and Bretherton 2009 ) and deep ( Zhang and McFarlane 1995 ) convection schemes in the CAM5
concentration. For our simulations, such boundary conditions are prescribed for 27 yr from January 1979 to December 2005. In this study we focus on December–February (DJF), the boreal winter season in which the MJO and its teleconnection to the extratropics are the most pronounced. Identical settings are used except for the choice of convective parameterization schemes. One simulation uses the default shallow ( Park and Bretherton 2009 ) and deep ( Zhang and McFarlane 1995 ) convection schemes in the CAM5
warm and dry conditions for the higher (sub-Antarctic) latitudes of Patagonia ( Moreno and Videla 2016 ; Kaplan et al. 2016 ). Conversely, strong ENSO variance in sub-Antarctic Patagonia and negative SAM-like states during the late Holocene (last ~5000 yr) appear to be reflected by cold and wet periods ( Moreno et al. 2014 ). In the present climate, the amplitudes of ENSO can be influenced by the mean state of the tropical Pacific ( Choi et al. 2009 ; Kang et al. 2015 ). The change of the
warm and dry conditions for the higher (sub-Antarctic) latitudes of Patagonia ( Moreno and Videla 2016 ; Kaplan et al. 2016 ). Conversely, strong ENSO variance in sub-Antarctic Patagonia and negative SAM-like states during the late Holocene (last ~5000 yr) appear to be reflected by cold and wet periods ( Moreno et al. 2014 ). In the present climate, the amplitudes of ENSO can be influenced by the mean state of the tropical Pacific ( Choi et al. 2009 ; Kang et al. 2015 ). The change of the
