Seasonal and CO 2 -Induced Shifts of the ITCZ: Testing Energetic Controls in Idealized Simulations with Comprehensive Models

Biasutti, Michela; Voigt, Aiko

doi:10.1175/JCLI-D-19-0602.1

Title: Seasonal and CO ₂ -Induced Shifts of the ITCZ: Testing Energetic Controls in Idealized Simulations with Comprehensive Models

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Abstract

The Tropical Rain Belts with an Annual Cycle and Continent Model Intercomparison Project (TRACMIP) ensemble—a multimodel ensemble of slab-ocean simulations in idealized configurations—provides a test of the relationship between the zonal mean ITCZ and the cross-equatorial atmospheric energy transports (AHT _eq ). In a gross sense, the ITCZ position is linearly related to AHT _eq , as expected from the energetic framework. Yet, in many aspects, the TRACMIP model simulations do not conform to the framework. Throughout the annual cycle there are large excursions in the ITCZ position unrelated to changes in the AHT _eq and, conversely, substantial variations in the magnitude of the AHT _eq while the ITCZ is stationary at its northernmost position. Variations both in the net vertical energy input at the ITCZ location and in the vertical profile of ascent play a role in setting the model behavior apart from the conceptual framework. Nevertheless, a linear fit to the ITCZ–AHT _eq relationship captures a substantial fraction of the seasonal variations in these quantities as well as the intermodel or across-climate variations in their annual mean values. The slope of the ITCZ–AHT _eq linear fit for annual mean changes across simulations with different forcings and configurations variesmore »« less

Authors:

^[1]; Voigt, Aiko ^[2]

Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York
Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York, and Institute of Meteorology and Climate Research–Department Troposphere Research, Karlsruhe Institute of Technology, Karlsruhe, Germany

Publication Date:: 2020-04-01

Research Org.:: Columbia Univ., New York, NY (United States)

Sponsoring Org.:: USDOE Office of Science (SC); National Science Foundation (NSF); German Ministry of Education and Research (BMBF)

OSTI Identifier:: 1603215

Alternate Identifier(s):: OSTI ID: 1802642

Grant/Contract Number:: SC0014423; AGS-1565522; 01LK1509A

Resource Type:: Published Article

Journal Name:: Journal of Climate

Additional Journal Information:: Journal Name: Journal of Climate Journal Volume: 33 Journal Issue: 7; Journal ID: ISSN 0894-8755

Publisher:: American Meteorological Society

Country of Publication:: United States

Language:: English

Subject:: 54 ENVIRONMENTAL SCIENCES; meteorology & atmospheric sciences; atmosphere; tropics; atmospheric circulation; large-scale motions; precipitations

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                    Biasutti, Michela, and Voigt, Aiko. Seasonal and CO 2 -Induced Shifts of the ITCZ: Testing Energetic Controls in Idealized Simulations with Comprehensive Models.  United States: N. p., 2020. 
Web.  doi:10.1175/JCLI-D-19-0602.1.

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                    Biasutti, Michela, & Voigt, Aiko. Seasonal and CO 2 -Induced Shifts of the ITCZ: Testing Energetic Controls in Idealized Simulations with Comprehensive Models.  United States.  https://doi.org/10.1175/JCLI-D-19-0602.1

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                    Biasutti, Michela, and Voigt, Aiko. Wed .  
"Seasonal and CO 2 -Induced Shifts of the ITCZ: Testing Energetic Controls in Idealized Simulations with Comprehensive Models".  United States.  https://doi.org/10.1175/JCLI-D-19-0602.1.

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@article{osti_1603215,

  title        = {Seasonal and CO 2 -Induced Shifts of the ITCZ: Testing Energetic Controls in Idealized Simulations with Comprehensive Models},

  author       = {Biasutti, Michela and Voigt, Aiko},

  abstractNote = {The Tropical Rain Belts with an Annual Cycle and Continent Model Intercomparison Project (TRACMIP) ensemble—a multimodel ensemble of slab-ocean simulations in idealized configurations—provides a test of the relationship between the zonal mean ITCZ and the cross-equatorial atmospheric energy transports (AHT eq ). In a gross sense, the ITCZ position is linearly related to AHT eq , as expected from the energetic framework. Yet, in many aspects, the TRACMIP model simulations do not conform to the framework. Throughout the annual cycle there are large excursions in the ITCZ position unrelated to changes in the AHT eq and, conversely, substantial variations in the magnitude of the AHT eq while the ITCZ is stationary at its northernmost position. Variations both in the net vertical energy input at the ITCZ location and in the vertical profile of ascent play a role in setting the model behavior apart from the conceptual framework. Nevertheless, a linear fit to the ITCZ–AHT eq relationship captures a substantial fraction of the seasonal variations in these quantities as well as the intermodel or across-climate variations in their annual mean values. The slope of the ITCZ–AHT eq linear fit for annual mean changes across simulations with different forcings and configurations varies in magnitude and even sign from model to model and we identify variations in the vertical profile of ascent as a key factor. A simple sea surface temperature–based index avoids the complication of changes in the vertical structure of the atmospheric circulation and provides a more reliable diagnostic for the ITCZ position.},

  doi          = {10.1175/JCLI-D-19-0602.1},

  journal      = {Journal of Climate},

  number       = 7,

  volume       = 33,

  place        = {United States},

  year         = {2020},

  month        = {4}

}

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Title: Seasonal and CO 2 -Induced Shifts of the ITCZ: Testing Energetic Controls in Idealized Simulations with Comprehensive Models

Abstract

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Title: Seasonal and CO ₂ -Induced Shifts of the ITCZ: Testing Energetic Controls in Idealized Simulations with Comprehensive Models