Synoptic situations related to spells of extreme temperatures over Argentina

Abstract

AbstractThis study analyses some synoptic situations in which extreme temperatures occur. Cases of temperature‐anomaly spells from ten stations in Argentina are studied. The duration and the maximum deviation in each case are considered. The Lund correlation method or manual classification was used to analyse the synoptic situations. The cold spells in winter during the period 1971/80 occurred in three kinds of synoptic situation. Most of the days have a high‐pressure system to the west and a trough in the centre of the country, which is associated with south‐westerly winds. The coldest days have south‐easterly winds to the north (from the Atlantic), which blow around a high‐pressure system over the southern part of the country. There is a difference between this synoptic situation and the coldest synoptic situation in summer. The coldest conditions in summer take place in south‐westerlies when three or more cold fronts have passed over the area. The warmest spell in summer (January 1972) occurred with a cold front coming from the south, a low‐pressure centre in the middle of the country (between two high‐pressure systems), with a flow from the north over Argentina. In winter the warmest spells occur in similar situations, but there are also warm fronts present over the northern part of the country. Lund's method is appropriate for finding the synoptic situations connected with some special cases.