Interannual variability of the frontal activity in the Southern Hemisphere: relationship with atmospheric circulation and precipitation over southern South America

The interannual variability of the frontal activity over the western Southern Hemisphere and its linkage with the variability of the atmospheric circulation and precipitation over southern South America is studied. The analysis is focused on the austral winter and spring seasons. The frontal activit...

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Bibliographic Details
Published in:Climate dynamics 2017-04, Vol.48 (7-8), p.2569-2579
Main Authors: Blázquez, Josefina, Solman, Silvina A.
Format: Article
Language:English
Subjects:
Atmosphere
Atmospheric circulation
Climatology
Correlation coefficient
Earth and Environmental Science
Earth Sciences
El Nino
Geophysics/Geodesy
Oceanography
Oceans
Precipitation
Precipitation variability
Seasons
Spring
Studies
Temperature
Temperature gradients
Variability
Winter
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Summary:The interannual variability of the frontal activity over the western Southern Hemisphere and its linkage with the variability of the atmospheric circulation and precipitation over southern South America is studied. The analysis is focused on the austral winter and spring seasons. The frontal activity is represented by an index defined as the product between the horizontal gradient of temperature and the relative vorticity at 850 hPa (FI) and is computed from the ERA Interim and NCEP2 reanalysis. For the two seasons the main mode of variability of FI, as depicted by the first Empirical Orthogonal Function, presents centres of action located in the southern part of the western Southern Hemisphere. This pattern is present in the two reanalysis datasets. The correlation coefficients between the principal component of the leading mode of FI and the two main modes of the 500 hPa geopotential height indicate that both the ENSO-mode and the SAM modulate the leading pattern of FI in winter while during the spring season the ENSO-mode controls the FI variability. The variability of the FI has a robust influence on the interannual variability of precipitation over southern South America and adjacent oceans. Over the continent, it was found that the pattern of precipitation anomalies associated with the variability of the FI depicts significant signals over southeastern South America (SESA), centre and south of Chile for winter and over SESA and southeastern Brazil for spring and agrees with the pattern of the leading mode of precipitation variability over southern South America.
ISSN:0930-7575
1432-0894
DOI:10.1007/s00382-016-3223-3