Open AccessThe Response of the Tropical Atlantic and West African Climate to Saharan Dust in a Fully Coupled GCM
Author(s) -
Jeffrey D. O. Strong,
Gabriel A. Vecchi,
Paul Ginoux
Publication year - 2015
Publication title -
journal of climate
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.315
H-Index - 287
eISSN - 1520-0442
pISSN - 0894-8755
DOI - 10.1175/jcli-d-14-00797.1
Subject(s) - intertropical convergence zone , climatology , tropical atlantic , environmental science , mineral dust , atmospheric sciences , climate model , monsoon , sea surface temperature , radiative forcing , atmosphere (unit) , radiative transfer , african easterly jet , geology , tropical wave , climate change , aerosol , physics , oceanography , precipitation , tropical cyclone , meteorology , quantum mechanics
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.