Summer dry events on synoptic and intraseasonal timescales in the Southeast Region of Brazil

Author(s)

Anderson Augusto Bier ^[1] ; Simone Erotildes Teleginski Ferraz ^[2] ; Tercio Ambrizzi ^[3]

Affiliation

^[1] Universidade de São Paulo - Brasil

^[2] Universidade Federal de Santa Maria - Brasil

^[3] Universidade de São Paulo - Brasil

• Document type: Journal article
• Source: ATMOSFERA; v. 36, n. 1, p. 57-76, 2022-11-07.

Abstract

ABSTRACT The occurrence of dry events in the Southeast Region of Brazil (SEB) during summer (rainfall season) has been in evidence in the last years, mainly due to previous extreme events in the 2013/14 and 2014/15 seasons. Drought analyses are usually carried out with monthly data. Here our methodology addresses the issue with daily data to generate a thorough analysis. Dry events were evaluated in different homogeneous precipitation sub-regions within the SEB, over 37 December-February (DJF) seasons and with two different timescales of duration: synoptic (5-9 days) and intraseasonal (≥10 days). Two main distinct dynamic patterns were found for dry events in southern and central-northern parts of SEB, respectively, but no significant differences were identified in the different timescales of occurrence. Southern events were characterized by a stationary ridge acting over the whole of southern South America, making the approximation of the transient system to southern SEB difficult. At the same time, this pattern showed a northern-shifted South Atlantic Convergence Zone (SACZ) configuration. In the central-northern events, a high pressure centered between Brazil’s South and Southeast regions was associated with the dryness conditions. An anomalous southward shift of meteorological systems characteristic of the South American summer was also verified for these events. Over the South Atlantic, an opposite SST anomaly configuration was identified between southern and central-northern events. (AU)

• FAPESP's process: 17/09659-6 - Interannual variability of the meridional transports across the SAMOC basin-wide array (SAMBAR)
• Grantee: Edmo José Dias Campos
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 14/50848-9 - INCT 2014: INCT for Climate Change
• Grantee: Jose Antonio Marengo Orsini
• Support Opportunities: Research Program on Global Climate Change - Thematic Grants
• FAPESP's process: 18/06806-0 - Changes in the variability modes of the South Atlantic Ocean and impacts on the climate of South America under of climate change
• Grantee: Anderson Augusto Bier
• Support Opportunities: Scholarships in Brazil - Doctorate