Padrões atmosféricos associados aos Distúrbios Ondulatórios de Leste no leste do Nordeste do Brasil.

Abstract

The present study intends to advance the knowledge about Easterly Wave Disturbances (EWD) that act on the coast of Northeast Brazil (NEB), using a temporal cut of 16 years (2000 to 2015). Through the application of techniques to identify the trough associated to the system, it is sought to investigate the atmospheric patterns associated with its occurrence, the moisture coupling to the system and to deepen the knowledge of its dynamic and thermodynamic characteristics, using reanalysis, satellite and observational data. Through Hovmöller diagrams of filtered meridional wind component in the 2 6 days band, using the Lanczos filter, it was possible to identify the signal of troughs and ridges associated with waves in the easterly flow at levels of 925 hPa, 850 hPa and 700 hPa, being most evident at 700 hPa, revealing larger waves at that level. To eliminate the noise associated with other coincident scale systems and to filter the less intense troughs, the filtered curvature vorticity in the stream function (2 6 days) was used to identify the troughs near NEB. Troughs were identified during all months of the year, both through the filtered meridional wind component, and through the filtered curvature vorticity. The dates in which the troughs were identified in the filtered curvature vorticity were used to calculate the mean fields and the anomalous fields of a series of variables. Results indicated average fields, in which the troughs were inserted, between February and November consistent with the climatology, with greater precipitation on the east of the NEB between May and July. The anomalous fields presented dry atmosphere in the axis of the troughs, humid atmosphere in the front and the rear of the troughs from low to middle troposphere, contrary to what the literature presents for the EWD in the east of the NEB, however, with characteristics similar to the moisture pattern of the Mixed Rossby Gravity waves. Three cases of EWD were analyzed, applying an objective identification method successfully, but without imposition of curvature vorticity thresholds. The cases allowed to confirm the anomalous patterns observed in the composites and it was verified a joint action of the EWD with frontal systems, cyclones and mixed Rossby Gravity waves, whose interaction can be associated to two moments of precipitation on the coast of NEB preceding and succeeding the passage of the EWD troughs.