Moisture transport and intraseasonal variability in the South America monsoon system

This paper examines moisture transport on intraseasonal timescales over the continent and over the South Atlantic convergence zone (SACZ) during the South America (SA) summer monsoon. Combined Empirical Orthogonal Function analysis (EOFc) of Global Precipitation Climatology Project pentad precipitat...

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Bibliographic Details
Published in:Climate dynamics 2011-05, Vol.36 (9-10), p.1865-1880
Main Authors: Carvalho, Leila M. V, Silva, Ana E, Jones, Charles, Liebmann, Brant, Silva Dias, Pedro L, Rocha, Humberto R
Format: Article
Language:English
Subjects:
Air temperature
Analysis
Atmospheric circulation
Bgi / Prodig
Climate
Climatology
Climatology. Bioclimatology. Climate change
Earth and Environmental Science
Earth Sciences
Earth, ocean, space
Exact sciences and technology
External geophysics
Geophysics/Geodesy
humidity
Marine
Meteorology
monsoon season
Monsoons
Ocean-atmosphere interaction
Oceanography
Physical geography
Rain and rainfall
Seasons
Specific humidity
summer
variance
Warm and intertropical climates
Water in the atmosphere (humidity, clouds, evaporation, precipitation)
Wind
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Summary:This paper examines moisture transport on intraseasonal timescales over the continent and over the South Atlantic convergence zone (SACZ) during the South America (SA) summer monsoon. Combined Empirical Orthogonal Function analysis (EOFc) of Global Precipitation Climatology Project pentad precipitation, specific humidity, air temperature, zonal and meridional winds at 850 hPa (NCEP/NCAR reanalysis) are performed to identify the large-scale variability of the South America monsoon system and the SACZ. The first EOFc was used as a large-scale index for the South American monsoon (LISAM), whereas the second EOFc characterized the SACZ. LISAM (SACZ) index showed spectral variance on 30-90 (15-20) days and were both band filtered (10-100 days). Intraseasonal wet anomalies were defined when LISAM and SACZ anomalies were above the 75th percentile of their respective distribution. LISAM and SACZ wet events were examined independently of each other and when they occur simultaneously. LISAM wet events were observed with the amplification of wave activity in the Northern Hemisphere and the enhancement of northwesterly cross-equatorial moisture transport over tropical continental SA. Enhanced SACZ was observed with moisture transport from the extratropics of the Southern Hemisphere. Simultaneous LISAM and SACZ wet events are associated with cross-equatorial moisture transport along with moisture transport from Subtropical Southwestern Atlantic.
ISSN:0930-7575
1432-0894
DOI:10.1007/s00382-010-0806-2