Análise em componentes principais das condições atmosféricas em episódios de rajadas de vento na região metropolitana de Salvador.

Abstract

The focus in this work is the wind gusts registered at the Salvador International Airport during the period 2003-2011. Surface meteorological variables observed within the airport area, meteorological satellite images and gridpoint data are used to analyze the wind gusts interannual, seasonal and hourly variability, to identify scales and physical factors involved by means of the principal component analysis, and to diagnose the synoptic conditions of two selected episodes. A total of 63 wind gusts were found; 51% occurred in 2003 and 2007, altogether. Gusts on the south sector of the wind rose are the most frequent. The hourly frequency of the gusts has a minimum between midnight and 7 A. M. May 2007 and 2009 have the maximum number of wind gusts. The factor loadings retained in the principal component analysis indicate the contribution of the synoptic and daily time scales in these months. On May 2007 there are five wind gusts, on the 10th and 11th, including the strongest of the period of study (68.5 km/h). On May 2009 there are five wind gusts also, on the 22th. The synoptic analysis of these gust days highlights the role played by: (a) an austral frontal system on the first episode (10-11 May 2007), and (b) a trough on the trades over the Northeast Brazil eastern area on the second episode (22 May 2009). All wind gusts, with exception of one, occurred in the presence of deep cumulus clouds (cumulus congestus). The Civil Defense of Salvador (CODESAL) indicates that the disasters registered on these days are due to meteorological factors such as strong winds.