Southeastern Pacific blocking episodes and their effects on the South American weather

Authors
Citation
Mt. Kayano, Southeastern Pacific blocking episodes and their effects on the South American weather, METEOR ATM, 69(3-4), 1999, pp. 145-155
Citations number
28
Categorie Soggetti
Earth Sciences
Journal title
METEOROLOGY AND ATMOSPHERIC PHYSICS
ISSN journal
01777971 → ACNP
Volume
69
Issue
3-4
Year of publication
1999
Pages
145 - 155
Database
ISI
SICI code
0177-7971(1999)69:3-4<145:SPBEAT>2.0.ZU;2-N
Abstract
Southeastern Pacific blocking episodes are studied using 17 years of reanal yzed daily data from the National Centers for Environmental Prediction (NCE P). The anomalous sea level pressure (SLP) within the area bounded by the l ongitudes of 130 degrees W and 100 degrees W and the latitudes of 50 degree s S and 70 degrees S is used as the base variable to determine periods with 7 or more sequential days with positive anomalies in this domain. Using th ese periods, composites are calculated for the SLP and its anomalies, 500-h Pa geopotential height anomalies and the 250-hPa and 925-hPa wind vectors i n the western southern hemisphere (SH). Composites for austral winter and s ummer exhibit atmospheric circulation features quite similar to those assoc iated with the blocking episodes in the southeastern Pacific. The correspon ding composite patterns of the precipitable water (Pw) and 925-hPa temperat ure anomalies for the South American sector are also discussed. For both se asons blocking episodes in the southeastern Pacific change the distribution s of these thermodynamic variables over South America, in particular in its southern and southeastern regions by reducing (increasing) the Pw and low- level temperature in the southern South America (the central part of the co ntinent). Therefore, monitoring the southeastern Pacific circulation patter ns may lead to improved weather forecast for the South American sector.