Influência das correntes de jato globais na formação de jato no Nordeste brasileiro

Abstract

The Brazilian Northeast jet stream (CJNEB), internationally recognized in 2017, is located between 0ºS and 20ºS with a speed greater than 20m/s. CJNEB is a mechanism of interaction and circulation between the hemispheres, but they are still poorly studied. The aim of this study is to analyze and classify how global circulation behave during interaction with CJNEB. Three study areas were used: area I includes AS (70ºN - 70ºS and 0-90ºW); Areas 2 and 3 encompass the entire planet between latitudes 70-30o S to 70-30o N for two hemispheres, respectively. The data used for the years 2018 to 2020 were: 1) NCEP/NCAR reanalysis data, with horizontal resolution of 2.5 ºx2.5º and 17 pressure levels (between 1000hPa - 100hPa); 2) satellite images gridded in the infrared and water vapor channels of the GIBBS (Global ISCCP B1). CJNEB was identified by its location and winds velocity above 20 m/s at the 200 hPa level. The events of inter-hemispheric linkages were chosen: (a) through advancement of the CJSTHN to latitudes 0-5ºN and (b) the existence of the link with the CJNEB. There was a total of 671 occurrences of advances (a), which resulted in 266 occurrences of connections (b). Connections lasting one and more days (16 events) were analyzed in detail from formation to dissipation. These events were classified as Complete (LC) and Incomplete (LI) Bindings: 1) when CJSTHN (CJSTHS) together with CJNEB enters HS (HN) but does not join CJSTHS (CJSTHN) (LI) and 2) when CJSTHN (CJSTHS) with CJNEB enters HS (HN) and joins with CJSTHS (CJSTHN) (LC). North’s incomplete bindings (14 events) are the most common with a duration of 1 to 13 days. Zonal and meridional processes were identified by 1) number of geopotential height anomaly nuclei (nuclei) and 2) families of baroclinic cyclones in satellite images (families). The shape of the H N current has always been meridional and the HS has generally changed from zonal to meridional. The number of nuclei/families is 5/6 in the HS while in the HN they can reach 6/7, that is, the southern circulation in the HN was more intense than in the HS. Upper Tropospheric Cyclonic Vortex and Trough of Bolivian High had a strong influence on the interhemispheric connection. Conceptual models, which show the conditions for the interhemispheric connection, were elaborated. These results will be used in operational practice to forecast meridional processes influenced by the circulation from HN to HS.