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Simulated Responses of the West African Monsoon and Zonal-Mean Tropical Precipitation to Early Holocene Orbital Forcing

Smyth, Jane E. and Hill, Spencer A. and Ming, Yi (2018) Simulated Responses of the West African Monsoon and Zonal-Mean Tropical Precipitation to Early Holocene Orbital Forcing. Geophysical Research Letters, 45 (21). pp. 12049-12057. ISSN 0094-8276.

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This study seeks to improve our mechanistic understanding of how the insolation changes associated with orbital forcing impact the West African monsoon and zonal‐mean tropical precipitation. We impose early Holocene orbital parameters in simulations with the Geophysical Fluid Dynamics Laboratory AM2.1 atmospheric general circulation model, either with fixed sea surface temperatures, a 50‐m thermodynamic slab ocean, or coupled to a dynamic ocean (CM2.1). In all cases, West African Monsoon rainfall expands northward, but the summer zonal‐mean Intertropical Convergence Zone does not—there is drying near 10°N, and in the slab ocean experiment a southward shift of rainfall. This contradicts expectations from the conventional energetic framework for the Intertropical Convergence Zone location, given anomalous southward energy fluxes in the deep tropics. These anomalous energy fluxes are not accomplished by a stronger Hadley circulation; instead, they arise from an increase in total gross moist stability in the northern tropics.

Item Type:Article
Related URLs:
URLURL TypeDescription
Smyth, Jane E.0000-0003-3497-5722
Hill, Spencer A.0000-0001-8672-0671
Ming, Yi0000-0002-5324-1305
Additional Information:© 2018. American Geophysical Union. Received 10 NOV 2017. Accepted 31 OCT 2018. Accepted article online 5 NOV 2018. Published online 9 NOV 2018. Corrected 3 DEC 2018. J.E.S. was partly supported by the NOAA Ernest F. Hollings Scholarship Program. S.A.H. is supported by an NSF AGS Postdoctoral Research Fellowship, NSF Award 1624740. Data used in this study can be retrieved from
Errata:In the originally published version of this article, a typographical error was introduced into the Plain Language Summary. The fifth sentence should have correctly read “To isolate the role of sea surface temperature changes, one set of simulations fixes them at modern values, another represents the ocean as a static 50‐m slab of water, and a third allows the ocean circulation to respond to the sunlight changes to respond to the sunlight changes.” The error has since been corrected, and the present version may be considered the authoritative version of record.
Funding AgencyGrant Number
National Oceanic and Atmospheric Administration (NOAA)UNSPECIFIED
NSF Postdoctoral FellowshipAGS-1624740
Subject Keywords:tropical dynamics; West African monsoon; intertropical convergence zone; Hadley circulation; energy transport; precipitation
Issue or Number:21
Record Number:CaltechAUTHORS:20181220-092840813
Persistent URL:
Official Citation:Smyth, J. E., Hill, S. A., & Ming, Y. (2018). Simulated responses of the West African monsoon and zonal‐mean tropical precipitation to early Holocene orbital forcing. Geophysical Research Letters, 45, 12,049–12,057.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:91928
Deposited By: George Porter
Deposited On:20 Dec 2018 18:18
Last Modified:03 Oct 2019 20:39

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