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The Response of the Tropical Atlantic and West African Climate to Saharan Dust in a Fully Coupled GCM

Author(s): Strong, Jeffrey DO; Vecchi, Gabriel A; Ginoux, Paul

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Abstract: This study examines the climate response in West Africa and the tropical Atlantic to an idealized aerosol radiative forcing from Saharan mineral dust, comparable to the observed changes between the 1960s and 1990s, using simulations with the fully coupled GFDL Climate Model, version 2.1 (CM2.1), for two optical property regimes: more absorbing (ABS) and more scattering (SCT) dust. For both regimes dust induces significant regional reductions in radiative flux at the surface (approximately −30 W m−2). At the top of the atmosphere (TOA) dust in the two simulations produces a radiative flux anomaly of opposite sign (+30 W m−2 in the ABS case and −20 W m−2 in the SCT case). These differences result in opposing regional hydrologic and thermodynamic effects of dust. The ABS-forced simulations show an increase in the West African monsoon resulting from dust, whereas in the SCT-forced simulations dust causes a decrease in the monsoon. This is due to moist enthalpy changes throughout the atmospheric column over West Africa creating either horizontal divergence or convergence near the surface, respectively. In the tropical North Atlantic, dust acts to cool the ocean surface. However, in the subsurface the ABS-forced simulations show a decrease in upper-ocean heat content, while the SCT-forced simulations show an increase in upper-ocean heat content. The peak differences primarily arise from the wind stress curl response to a shift in the Atlantic ITCZ and associated mixed layer depth anomalies. Changes to upper-ocean currents are also found to be important in transporting energy across the equator.
Publication Date: 15-Sep-2015
Citation: Strong, Jeffrey D.O., Gabriel A. Vecchi, and Paul Ginoux. "The response of the tropical Atlantic and West African climate to Saharan dust in a fully coupled GCM." Journal of Climate 28, no. 18 (2015): 7071-7092. doi:10.1175/JCLI-D-14-00797.1.
DOI: doi:10.1175/JCLI-D-14-00797.1
ISSN: 0894-8755
EISSN: 1520-0442
Pages: 7071 - 7092
Type of Material: Journal Article
Journal/Proceeding Title: Journal of Climate
Version: Final published version. Article is made available in OAR by the publisher's permission or policy.

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