The Effect of an Equatorial Continent on the Tropical Rain Belt. Part 1: Annual Mean Changes in the ITCZ

Biasutti, Michela; Russotto, Rick D.; Voigt, Aiko; Blackmon-Luca, Charles C.

doi:10.1175/jcli-d-20-0739.1

Title: The Effect of an Equatorial Continent on the Tropical Rain Belt. Part 1: Annual Mean Changes in the ITCZ

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Abstract

The TRACMIP (Tropical Rain Belts with an Annual Cycle and Continent Model Intercomparison Project) ensemble includes slab-ocean aquaplanet controls and experiments with a highly idealized tropical continent, characterized by modified aquaplanet grid cells with increased evaporative resistance, increased albedo, reduced heat capacity, and no ocean heat transport (zero Q-flux). In the annual mean, an equatorial cold tongue develops west of the continent and induces dry anomalies and a split in the oceanic intertropical convergence zone (ITCZ). Ocean cooling is initiated by advection of cold, dry air from the winter portion of the continent; warm, humid anomalies in the summer portion are restricted to the continent by anomalous surface convergence. The surface energy budget suggests that ocean cooling persists and intensifies because of a positive feedback between a colder surface, drier and colder air, reduced downwelling longwave (LW) flux, and enhanced net surface LW cooling (LW feedback). A feedback between wind, evaporation, and SST (so-called WES feedback) also contributes to the establishment and maintenance of the cold tongue. Simulations with a gray-radiation model and simulations that diverge from protocol (with negligible winter cooling) confirm the importance of moist-radiative feedbacks and of rectification effects on the seasonal cycle. This mechanism coupling themore »« less

Authors:

Biasutti, Michela ^[1]; Russotto, Rick D. ^[1]; Voigt, Aiko ^[2]; Blackmon-Luca, Charles C. ^[3]

Columbia Univ., Palisades, NY (United States). Lamont-Doherty Earth Observatory
Karlsruhe Inst. of Technology (KIT) (Germany). Research Inst. for Meteorology and Climate Research. Dept. of Troposhere
Columbia Univ., New York, NY (United States)

Publication Date:: Thu Jun 10 00:00:00 EDT 2021

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

Sponsoring Org.:: USDOE Office of Science (SC)

OSTI Identifier:: 1851917

Grant/Contract Number:: SC0014423

Resource Type:: Accepted Manuscript

Journal Name:: Journal of Climate

Additional Journal Information:: Journal Volume: 34; Journal Issue: 14; Journal ID: ISSN 0894-8755

Publisher:: American Meteorological Society

Country of Publication:: United States

Language:: English

Subject:: 54 ENVIRONMENTAL SCIENCES; Meteorology & Atmospheric Sciences; Dynamics; Rainbands; Monsoons; Climate models; Model comparison; Intertropical convergence zone; Bias; Idealized models

Citation Formats


                    Biasutti, Michela, Russotto, Rick D., Voigt, Aiko, and Blackmon-Luca, Charles C. The Effect of an Equatorial Continent on the Tropical Rain Belt. Part 1: Annual Mean Changes in the ITCZ.  United States: N. p., 2021. 
Web.  doi:10.1175/jcli-d-20-0739.1.

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                    Biasutti, Michela, Russotto, Rick D., Voigt, Aiko, & Blackmon-Luca, Charles C. The Effect of an Equatorial Continent on the Tropical Rain Belt. Part 1: Annual Mean Changes in the ITCZ.  United States.  https://doi.org/10.1175/jcli-d-20-0739.1

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                    Biasutti, Michela, Russotto, Rick D., Voigt, Aiko, and Blackmon-Luca, Charles C. Thu .  
"The Effect of an Equatorial Continent on the Tropical Rain Belt. Part 1: Annual Mean Changes in the ITCZ".  United States.  https://doi.org/10.1175/jcli-d-20-0739.1.  https://www.osti.gov/servlets/purl/1851917.

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@article{osti_1851917,

  title        = {The Effect of an Equatorial Continent on the Tropical Rain Belt. Part 1: Annual Mean Changes in the ITCZ},

  author       = {Biasutti, Michela and Russotto, Rick D. and Voigt, Aiko and Blackmon-Luca, Charles C.},

  abstractNote = {The TRACMIP (Tropical Rain Belts with an Annual Cycle and Continent Model Intercomparison Project) ensemble includes slab-ocean aquaplanet controls and experiments with a highly idealized tropical continent, characterized by modified aquaplanet grid cells with increased evaporative resistance, increased albedo, reduced heat capacity, and no ocean heat transport (zero Q-flux). In the annual mean, an equatorial cold tongue develops west of the continent and induces dry anomalies and a split in the oceanic intertropical convergence zone (ITCZ). Ocean cooling is initiated by advection of cold, dry air from the winter portion of the continent; warm, humid anomalies in the summer portion are restricted to the continent by anomalous surface convergence. The surface energy budget suggests that ocean cooling persists and intensifies because of a positive feedback between a colder surface, drier and colder air, reduced downwelling longwave (LW) flux, and enhanced net surface LW cooling (LW feedback). A feedback between wind, evaporation, and SST (so-called WES feedback) also contributes to the establishment and maintenance of the cold tongue. Simulations with a gray-radiation model and simulations that diverge from protocol (with negligible winter cooling) confirm the importance of moist-radiative feedbacks and of rectification effects on the seasonal cycle. This mechanism coupling the continental and oceanic climate might be relevant to the double ITCZ bias. The key role of the LW feedback suggests that the study of interactions between monsoons and oceanic ITCZs requires full-physics models and a hierarchy of land models that considers evaporative processes alongside heat capacity as a defining characteristic of land.},

  doi          = {10.1175/jcli-d-20-0739.1},

  journal      = {Journal of Climate},

  number       = 14,

  volume       = 34,

  place        = {United States},

  year         = {Thu Jun 10 00:00:00 EDT 2021},

  month        = {Thu Jun 10 00:00:00 EDT 2021}

}

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