CIMA   09099
CENTRO DE INVESTIGACIONES DEL MAR Y LA ATMOSFERA
Unidad Ejecutora - UE
artículos
Título:
Trends in Total and Extreme South American Rainfall in 19602000 and Links with Sea Surface Temperature
Autor/es:
M. R. HAYLOCK,A T. C. PETERSON,B L. M. ALVES,C T. AMBRIZZI,D Y. M. T. ANUNCIAÇÃO,E J. BAEZ,FV. R. BARROS,G M. A. BERLATO,H M. BIDEGAIN,I ET AL
Revista:
JOURNAL OF CLIMATE
Editorial:
AMS
Referencias:
Lugar: , Boston; Año: 2006 vol. 19 p. 1490 - 1512
ISSN:
0894-8755
Resumen:
A weeklong workshop in Brazil in August 2004 provided the opportunity for 28 scientists from southern South America to examine
daily rainfall observations to determine changes in both total and extreme rainfall. Twelve annual indices of daily rainfall were
calculated over the period 1960 to 2000, examining changes to both the entire distribution as well as the extremes. Maps of trends in
the 12 rainfall indices showed large regions of coherent change, with many stations showing statistically significant changes in some of
the indices. The pattern of trends for the extremes was generally the same as that for total annual rainfall, with a change to wetter
conditions in Ecuador and northern Peru and the region of southern Brazil, Paraguay, Uruguay, and northern and central Argentina.
A decrease was observed in southern Peru and southern Chile, with the latter showing significant decreases in many indices. A
canonical correlation analysis between each of the indices and sea surface temperatures (SSTs) revealed two large-scale patterns that
have contributed to the observed trends in the rainfall indices. A coupled pattern with ENSO-like SST loadings and rainfall loadings
showing similarities with the pattern of the observed trend reveals that the change to a generally more negative Southern Oscillation
index (SOI) has had an important effect on regional rainfall trends. A significant decrease in many of the rainfall indices at several
stations in southern Chile and Argentina can be explained by a canonical pattern reflecting a weakening of the continental trough
leading to a southward shift in storm tracks. This latter signal is a change that has been seen at similar latitudes in other parts of the
Southern Hemisphere. A similar analysis was carried out for eastern Brazil using gridded indices calculated from 354 stations from the
Global Historical Climatology Network (GHCN) database. The observed trend toward wetter conditions in the southwest and drier
conditions in the northeast could again be explained by changes in ENSO.