Padrões de circulação atmosférico associados á ligação da extremidade frontal com a ZCIT

Abstract

This research deals with meteorological aspects of the rainfall intense in the Northeast Brazil (NEB) and specifically about cold fronts arrivals to the north of the NEB from 2008 to 2017. The purpose of this study is 1) identification of the frontal systems structure connected with the Intertropical Convergence Zone (ITCZ) in the NEB, 2) development of the Atmospheric circulation pattern and 3) associated phenomena analyses. Satellite images together with the fields of the advection of the equivalent potential temperature and relative vorticity were used for the frontal systems identification in the NEB. Twenty-seven cold fronts were recorded by the clime-analyses database and by the cloudiness band analyses during 10 years (2008-2017). 5 cases appear to be connected with the ITCZs. Troposphere synoptic analysis showed the differences between the structure of the fronts connected with ITCZ and fronts without such connection. In the cases with connection some anticyclonic circulation was observed at the high levels (200 hPa) in the NEB and the position of the subtropical jet stream was to the south of South America (between 16 ° to 25 ° S). In the cases without connection cyclonic circulation at the high levels (200 hPa) and the influence of the subtropical jet stream was observed in the NEB. Adverse phenomena analysis in the NEB region recorded the occurrence of the wet fog and strong rain in all cases with connection. Case occurred between 20 and 28/05/2017 provoked landslides, resulting in the death of 4 people in Maceio. According to the civil defence of the Alagoas state landslides have led to large material losses. Troposphere standards have been developed to determine whether the frontal zone is associated with ITCZ or not. This association can be detected when: a) the position of the subtropical jet stream is located approximately in the southwestern Brazil, without an influence on the NEB region; b) anticyclonic circulation at the high levels (200 hPa) on the NEB, contributing in the displacement of the subtropical jet stream on the southwestern Brazil, allowing displacement of the cold front toward the northern NEB. The connection does not happen when: a) Position of the subtropical jet stream is located in the NEB, with the influence in this region; b) Cyclonic circulation at the high levels (200 hPa) of the NEB region contributing in the displacement of jet stream to the NEB region, blocking the entrance of the frontal systems to the northern NEB.