Role of the global oceans and land–atmosphere interaction on summertime interdecadal variability over northern Argentina

This study uses experiments with an atmospheric general circulation model (AGCM) to address the role of the oceans and the effect of land–atmosphere coupling on the predictability of summertime rainfall over northern Argentina focusing on interdecadal time scales during 1901–2006. Ensembles of exper...

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Bibliographic Details
Published in:Climate dynamics 2014-04, Vol.42 (7-8), p.1733-1753
Main Authors: Barreiro, Marcelo, Díaz, Nicolas, Renom, Madeleine
Format: Article
Language:English
Subjects:
Analysis
Atmosphere
Atmospheric circulation
Atmospheric models
Climate
Climate cycles
Climatology
Climatology. Bioclimatology. Climate change
Earth and Environmental Science
Earth Sciences
Earth, ocean, space
Evaporation
Exact sciences and technology
External geophysics
Geophysics/Geodesy
Marine
Meteorology
Ocean-atmosphere interaction
Oceanography
Oceans
Precipitation variability
Rainfall
Sea surface temperature
Soil moisture
Summer
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Summary:This study uses experiments with an atmospheric general circulation model (AGCM) to address the role of the oceans and the effect of land–atmosphere coupling on the predictability of summertime rainfall over northern Argentina focusing on interdecadal time scales during 1901–2006. Ensembles of experiments where the AGCM is forced with historical sea surface temperature (SST) in the global, Pacific and tropical-North Atlantic domains are used. The role of land–atmosphere interaction is assessed comparing the output of simulations with active and climatological soil moisture. A maximum covariance analysis between precipitation and SST reveals the impact of the Pacific Decadal Oscillation, the Atlantic Multidecadal Oscillation and the equatorial–tropical South Atlantic on rainfall over northern Argentina. Model simulations further show that while the dominant influence comes from the Pacific basin, the Atlantic influence can explain a large transition from dry to wet decades over northern Argentina during the beginning of the 1970s. Analysis of anomalies before and after the transition reveals an upper level anticyclonic circulation off the Patagonian coast with barotropic structure. This circulation enhances the moisture transport and convergence in northern Argentina and, together with enhanced evaporation, increased the rainfall after 1970. The SST pattern is dominated by cold conditions in the equatorial Atlantic and warm eastern Pacific and South Atlantic. We also found that land–atmosphere interaction leads to a representation of the long term rainfall evolution over northern Argentina that is closer to the observed one. Moreover, it leads to a smaller dispersion among ensemble members, thus resulting in a larger signal-to-noise ratio.
ISSN:0930-7575
1432-0894
DOI:10.1007/s00382-014-2088-6