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Due to its importance for water availability in the tropics and subtropics, efficient tracking of the seasonal and long-term shifts of the intertropical convergence zone (ITCZ) is of great value. Current approaches, which are based on tracking changes in the annual mean of single variables, ignore the intra-annual dynamics, while more sophisticated methods are computationally intensive. Here we propose a new probabilistic framework to track the ITCZ, which is based on tracking the location of maximum precipitation and minimum outgoing longwave radiation in overlapping longitudinal windows. Our framework is seasonally and longitudinally explicit, allows for joint consideration of multiple variables to define the ITCZ, and is flexible in its implementation, thus, it can be used in analyses of different scales and scopes. We apply our framework to analyze the recent climatology of the ITCZ and report a southward trend in its location over central Pacific in the late twentieth century.

Plain Language Summary The zone of deep air convection and heavy precipitation in the Earth's tropics, known as the intertropical convergence zone (ITCZ), is characterized by seasonal southward and northward movement, following Sun's radiation, as well as long-term meridional shifts, which greatly affect water availability in many regions around the world. This study proposes and applies a new probabilistic framework to track the ITCZ by jointly considering multiple physical variables to define its location. It also allows for detailed analysis of the intra-annual dynamics in all longitudes of the globe, while being computationally efficient and flexible in its implementation. We reveal a statistically significant southward trend in the location of the ITCZ over the central Pacific.