Assessment of the Intertropical Convergence Zone over the Atlantic Ocean through an Algorithm Based on Precipitation

Abstract

The Intertropical Convergence Zone (ITCZ) is a key atmospheric system on a global scale, primarily driven by trade wind convergence near the equator. The ITCZ plays a crucial role in modulating the climate of the borders of tropical continental areas. For instance, Northeastern Brazil experiences a climate influenced by the ITCZ over the Atlantic Ocean. In some periods, the ITCZ exhibits double bands, known as the double ITCZ. While the features of the ITCZ have been described using various approaches and atmospheric variables, there is still a lack of regional studies focusing on the ITCZ and double ITCZ in the Atlantic Ocean. In this context, the main goals of this study are (1) to describe a simple algorithm based on precipitation to identify the ITCZ and double ITCZ, (2) to present a climatology (1997–2022) of the position, width, and intensity of these two convective bands, and (3) to investigate variabilities in the ITCZ characteristics associated with anomalies of sea surface temperature (SST) in the tropical Pacific and Atlantic oceans. The double ITCZ typically occurs southward of the main cloud band, and between February and April, both bands are more distant (~4.5°). In the western sector of the Atlantic Ocean, the ITCZ and its double band extend to more southerly latitudes in austral autumn. Considering the entire Atlantic basin, the annual mean of the latitudinal position, width, and intensity of the ITCZ is 4.9°N, 4.2°, and 11 mm/day, respectively, while for the double ITCZ, it is 0.4°N, 2.6°, 10.3 mm/day, respectively. While the SST anomalies in the Pacific Ocean (El Niño and La Niña episodes) affect more the ITCZ width, the SST anomalies in the Tropical South Atlantic affect both its position and width.