Interannual and Intraseasonal Variations of the Onset and Demise of the Pre-Wet Season and the Wet Season in the Northern Northeast Brazil

Author(s)

Francisco das Chagas Vasconcelos Junior ^[1] ; Charles Jones ^[2] ; Adilson Wagner Gandu ^[3]

Affiliation

^[1] Fundação Cearense de Meteorologia e Recursos Hídricos - Brasil

^[2] University of California Santa Barbara. Department of Geography and Earth Research Institute - Estados Unidos

^[3] Universidade Federal do Ceará. Instituto de Ciências do Mar - Brasil

• Document type: Journal article
• Source: Revista Brasileira de Meteorologia; v. 33, n. 3, p. 472-484, 2018-09-00.

Abstract

Abstract The Northern Northeast Brazil (NNB) has two rainy periods, namely Pre-Wet Season (PWS) and Wet Season (WES), which are usually treated as one system. The precipitation pattern on NNB is influenced by sea surface temperature (SST) anomalies in the Atlantic and Pacific Ocean on interannual timescales particularly by the Interhemispheric Gradient of SST anomalies (IGS) and El Niño Southern Oscillation (ENSO). On intraseasonal time scales, the MJO is especially important. This study investigates the variability of the PWS/WES. The PWS is largely associated with the development of the South America Monsoon System and South Atlantic Convergence Zone (SAMS/SACZ); the onset is depicted by incursion of the SAMS/SACZ northward. Anomalous atmospheric cyclonic circulation over the southeastern Brazil along with easterlies over the northern Tropical Atlantic marks the early onset of the PWS, while easterlies over the southern Tropical Atlantic are related to late onset episodes. The demise of the PWS is significantly associated with propagation of the MJO, specifically during phases 4-5 of the MJO lifecycle. A Rossby wave train in 200-hPa geopotential height with positive anomalies over central-southern Brazil is depicted during transition between PWS and WES. (AU)

• FAPESP's process: 13/09642-5 - Relations between high precipitation events in the northern Northeast Brazil and the role of the Madden-Julian oscillation
• Grantee: Francisco das Chagas Vasconcelos Júnior
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• FAPESP's process: 11/09314-2 - Water vapor intraseasonal variability over northern Northeast Brazil and the southern hemisphere summer: present climate and future projections
• Grantee: Francisco das Chagas Vasconcelos Júnior
• Support Opportunities: Scholarships in Brazil - Doctorate