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Title: Black carbon aerosol-induced Northern Hemisphere tropical expansion

Abstract

Global climate models (GCMs) underestimate the observed trend in tropical expansion. Recent studies partly attribute it to black carbon (BC) aerosols, which are poorly represented in GCMs. In this paper, we conduct a suite of idealized experiments with the Community Atmosphere Model version 4 coupled to a slab ocean model forced with increasing BC concentrations covering a large swath of the estimated range of current BC radiative forcing while maintaining their spatial distribution. The Northern Hemisphere (NH) tropics expand poleward nearly linearly as BC radiative forcing increases (0.7° W -1 m 2), indicating that a realistic representation of BC could reduce GCM biases. We find support for the mechanism where BC-induced midlatitude tropospheric heating shifts the maximum meridional tropospheric temperature gradient poleward resulting in tropical expansion. Finally, we also find that the NH poleward tropical edge is nearly linearly correlated with the location of the Intertropical Convergence Zone, which shifts northward in response to increasing BC.

Authors:
 [1];  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Computational Earth Sciences Group and Climate Change Science Inst.
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER)
OSTI Identifier:
1324138
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Geophysical Research Letters
Additional Journal Information:
Journal Volume: 42; Journal Issue: 12; Journal ID: ISSN 0094-8276
Publisher:
American Geophysical Union
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 54 ENVIRONMENTAL SCIENCES; tropical expansion; black carbon aerosol; midlatitude warming

Citation Formats

Kovilakam, Mahesh, and Mahajan, Salil. Black carbon aerosol-induced Northern Hemisphere tropical expansion. United States: N. p., 2015. Web. doi:10.1002/2015GL064559.
Kovilakam, Mahesh, & Mahajan, Salil. Black carbon aerosol-induced Northern Hemisphere tropical expansion. United States. https://doi.org/10.1002/2015GL064559
Kovilakam, Mahesh, and Mahajan, Salil. Tue . "Black carbon aerosol-induced Northern Hemisphere tropical expansion". United States. https://doi.org/10.1002/2015GL064559. https://www.osti.gov/servlets/purl/1324138.
@article{osti_1324138,
title = {Black carbon aerosol-induced Northern Hemisphere tropical expansion},
author = {Kovilakam, Mahesh and Mahajan, Salil},
abstractNote = {Global climate models (GCMs) underestimate the observed trend in tropical expansion. Recent studies partly attribute it to black carbon (BC) aerosols, which are poorly represented in GCMs. In this paper, we conduct a suite of idealized experiments with the Community Atmosphere Model version 4 coupled to a slab ocean model forced with increasing BC concentrations covering a large swath of the estimated range of current BC radiative forcing while maintaining their spatial distribution. The Northern Hemisphere (NH) tropics expand poleward nearly linearly as BC radiative forcing increases (0.7° W-1 m2), indicating that a realistic representation of BC could reduce GCM biases. We find support for the mechanism where BC-induced midlatitude tropospheric heating shifts the maximum meridional tropospheric temperature gradient poleward resulting in tropical expansion. Finally, we also find that the NH poleward tropical edge is nearly linearly correlated with the location of the Intertropical Convergence Zone, which shifts northward in response to increasing BC.},
doi = {10.1002/2015GL064559},
url = {https://www.osti.gov/biblio/1324138}, journal = {Geophysical Research Letters},
issn = {0094-8276},
number = 12,
volume = 42,
place = {United States},
year = {2015},
month = {6}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Citation Metrics:
Cited by: 9 works
Citation information provided by
Web of Science

Works referenced in this record:

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    Works referencing / citing this record:

    Recent Hadley cell expansion: The role of internal atmospheric variability in reconciling modeled and observed trends: MODELS CAPTURE HC SHIFT
    journal, December 2015


    Individual particle morphology, coatings, and impurities of black carbon aerosols in Antarctic ice and tropical rainfall
    journal, November 2016


    The Response of Local Precipitation and Sea Level Pressure to Hadley Cell Expansion: Local Response to Hadley Cell Expansion
    journal, October 2017


    Carbon Dioxide Physiological Forcing Dominates Projected Eastern Amazonian Drying
    journal, March 2018


    Are Changes in Atmospheric Circulation Important for Black Carbon Aerosol Impacts on Clouds, Precipitation, and Radiation?
    journal, July 2019