Analysis of Intense Small Summers in Southern Brazil and Associated Synoptic Conditions

• Main Authors: William Duarte Jacondino, Humberto Conrado, Ana Nascimento
• Format: Article
• Language: English
• Published: Universidade Federal do Rio de Janeiro 2018-08-01
• Series: Anuário do Instituto de Geociências
• Subjects: blocking; south region; composite fields; small summer
• Online Access: http://www.anuario.igeo.ufrj.br/2018_2/2018_2_377_389.pdf
• ISSN: 0101-9759; 1982-3908

Small summers are assigned to situations where the regular regime of the cold season of a region is interrupted, being characterized by having a prolonged period of anomalously high temperatures for a given season of the year and insignificant precipitation (equal to or less than 1 mm). The objective of this paper was to apply a methodology that allows to quantificate the most intense small summers events that occurred in the seasonal period from may to september during the period from 1991 to 2015 in the southern region of Brazil and obtain a detailing description of the predominant synoptic environment associated with the stages of formation and maturation of these events. A total of 72 events were identified, of which 27 were considered intense events according to thresholds established according to duration, range and magnitude criteria. The results indicate that the phenomenon acts with greater magnitude in the state of Rio Grande do Sul, with August and September presenting greater magnitude, whereas only August shows more cases. Composite fields of atmospheric variables are calculated about the 27 most intense cases. The analyzes indicates that the phenomenon is associated with the configuration of a persistent amplified ridge on the center-east of South America and favored transport in low levels of hot and dry air from the Midwest region to the South of Brazil. The analyzes also indicates that in the days before the small summer longer waves predominate over the Pacific Ocean.