Characterization of the double band of the intertropical convergence zone (ITCZ) over the atlantic ocean

Abstract

Several studies have documented the presence of double band (DB) of the Intertropical Convergence Zone (ITCZ) in the Pacific Ocean, while in the Atlantic Ocean, even though this phenomenon is known, there is practically no literature. Therefore, the purposes of this study are: to identify the occurrence of DB in the tropical Atlantic Ocean in the summer and autumn seasons, from 2010 to 2017; to perform a composition analysis to different atmospheric variables considering events with DB and events without DB in order to showing the difference between them and to evaluate a hypothesis that tries to explain the formation process of DB in the Atlantic Ocean. To identify the DB cases, the synoptic surface charts prepared by the Weather Prediction Group (GPT) of the Center for Weather Forecasting and Climate Studies of the National Institute of Space Research (CPTEC/INPE), satellite images and the European Centre for Medium--Range Weather Forecasts (ECMWF) Re-Analysis (ERA-Interim) reanalysis were used. The results show that the DBs are more frequent and lasting in March and April and that the two bands are distant from each other in ~ 4º of latitude. In the DB composite, the variables 10-m mass convergence and outgoing longwave radiation represent better the DB than the other variables. In the comparison of the composites for events with and without DB of the quoted variables, there are statistically significant negative anomalies southward equator. The hypothesis tested to explain the formation of DB in the Tropical Atlantic Ocean was partially proven.