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Aqua-planet simulations of the formation of the South Atlantic convergence zoneThe impact of Amazon Basin convection and cold fronts on the formation and maintenance of the South Atlantic convergence zone (SACZ) is studied using aqua-planet simulations with a general circulation model. In the model, a circular patch of warm sea-surface temperature (SST) is used to mimic the effect of the Amazon Basin on South American monsoon convection. The aqua-planet simulations were designed to study the effect of the strength and latitude of Amazon Basin convection on the formation of the SACZ. The simulations indicate that the strength of the SACZ increases as the Amazon convection intensifies and is moved away from the equator. Of the two controls studied here, the latitude of the Amazon convection exerts the strongest effect on the strength of the SACZ. An analysis of the synoptic-scale variability in the simulations shows the importance of frontal systems in the formation of the aqua-planet SACZ. Composite time series of frontal systems that occurred in the simulations show that a robust SACZ occurs when fronts penetrate into the subtropics and become stationary there as they cross eastward of the longitude of the Amazon Basin. Moisture convergence associated with these frontal systems produces rainfall not along the model SACZ region and along a large portion of the northern model Amazon Basin. Simulations in which the warm SST patch was too weak or too close to the equator did not produce frontal systems that extended into the tropics and became stationary, and did not form a SACZ. In the model, the SACZ forms as Amazon Basin convection strengthens and migrates far enough southward to allow frontal systems to penetrate into the tropics and stall over South America. This result is in agreement with observations that the SACZ tends to form after the onset of the monsoon season in the Amazon Basin.
Document ID
20140009146
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Nieto Ferreira, Rosana
(Department of Geography, East Carolina University)
Chao, Winston C.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Date Acquired
July 14, 2014
Publication Date
March 15, 2013
Publication Information
Publication: International Journal of Climatology
Publisher: Wiley
Volume: 33
Issue: 3
ISSN: 1097-0088
Subject Category
Meteorology And Climatology
Report/Patent Number
GSFC-E-DAA-TN10520
Funding Number(s)
CONTRACT_GRANT: NA07OAR4310495
Distribution Limits
Public
Copyright
Public Use Permitted.
Keywords
South American Monsoon
Cold Fronts
SACZ
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