The nature of a heat wave in eastern Argentina occurring during SALLJEX

CERNE, BIBIANA; VERA, CAROLINA; LIEBMANN, BRANT

MONTHLY ENERGY REVIEW

American Meteorological Society

Año: 2007 vol. 135 p. 1165 - 1174

0027-0644

This paper describes the physical processes associated with the occurrence of a heat wave over central Argentina during the austral summer of 2002-2003, during which the South American Low-Level Jet Experiment (SALLJEX) was carried out. The SALLJEX heat wave that lasted between 25 January and 2 February of 2003 was punctuated by extreme conditions during the last 3 days with the largest historical temperature recorded over the last 35 years in several stations of the region. It was found that not only the activity of synoptic scale waves, but also the intraseasonal oscillation variability had a strong impact on the temperature evolution during that particular summer. During the weeks previous to the heat wave development, an intensified South Atlantic Convergence Zone (SACZ) dominated the atmospheric conditions over tropical South America. Temperature started to increase in the subtropics due to the subsidence and diabatic warming associated with the SACZ, as depicted by SALLJEX upper-air observations. An extratropical anticyclone that evolved along southern South America further intensified subsidence conditions. By the end of January the warming processes associated with SACZ activity weakened, while horizontal temperature advection begun to dominate over central Argentina due to the intensification of the South American Low-Level Jet.  The approach of an extratropical frontal system produced the maximization of such mechanisms leading to temperature extremes by 2 February with temperature anomalies at least two standard deviations larger than the climatological mean values.