Intertropical Convergence Zone Intertropical Convergence Zone The Intertropical Convergence Zone (ITCZ), known by sailors as the doldrums or the calms, is the area encircling Earth near the Equator, where the northeast and southeast trade winds converge. The ITCZ was originally identified from the 1920s to the 1940s as the "Intertropical Front" ("ITF"), but after the recognition in the 1940s and the 1950s of the significance of wind field convergence in tropical weather production, the term "ITCZ" was then applied. When it lies near the Equator, it is called the near-equatorial trough. Where the ITCZ is drawn into and merges with a monsoonal circulation,
South Atlantic Convergence Zone South Atlantic Convergence Zone The South Atlantic convergence zone, or SACZ, is an elongated axis of clouds, precipitation, and convergent winds oriented in a northwest-southeast manner across southeast Brazil into the southwest Atlantic Ocean. By definition, the feature is a monsoon trough. It is strongest in the warm season. Thunderstorm activity along the feature magnifies over three or more days when the Madden–Julian oscillation passes into the region, due to the enhanced upper divergence. Low level winds over Rondônia are tied to the strength of this zone, where westerly wind anomalies correlate to active phases of the South American monsoon,