Title: Harnessing S2S Predictability from Annual Evolution
Lecturer: Prof. Ming Cai（Florida State University）
Inviter: Prof. Zhe-Min Tan
Time: Thursday March 19, 2026 at 10:00 AM
Venue: Lecture Hall D103, School of Atmospheric Sciences
Abstract: Subseasonal-to-seasonal (S2S) prediction is often regarded as a “desert” of forecast skill. Weather forecasts lose accuracy beyond the two-week limit, while seasonal forecasts benefit from slowly varying external influences such as ocean conditions and solar forcing. Moreover, most S2S forecasts focus primarily on anomaly fields, separating S2S anomalies from the annual evolution in which they are embedded. Here we propose a new paradigm: a substantial portion of S2S anomalies may be embedded in the annual evolution of the climate system, which itself varies from year to year. Because annual evolution reflects the influence of slowly varying external drivers, it may be inherently more predictable than S2S anomalies alone. We confirm that a large portion of cold-season S2S Northern Hemisphere stratospheric polar vortex (SPV) anomalies is closely associated with differences in the SPV annual evolution across years. By predicting these annually varying parameters before the onset of the cold season, the framework enables skillful prediction of S2S SPV anomalies in the cold season at lead times of up to six months. Our study suggests that S2S predictability may be harnessed in other climate systems with strong seasonal cycles, such as Arctic sea-ice variability, the East Asian monsoon, and regional temperature and precipitation extremes. Harnessing S2S predictability from annual evolution offers a new pathway for improving extended-range forecast skill.
Brief introduction to the speaker: Ming Cai is a full professor at Department of Earth, Ocean, and Atmospheric Science, Florida State University. He served as Editor of the Journal of Atmospheric Sciences from 2010 to 2016 and the Director of Large-Scale and Climate Dynamics Program at (U.S.) National Science Foundation from 2016-2019. His current research interests are in the areas of climate dynamics, theory of global change, linear/nonlinear dynamics of large-scale atmospheric motions, dynamics of tropical cyclones, short-time climate variability, global mass circulation theory and its applications for climate predictions and projections. He has authored or co-authored over 110 peer-reviewed journal papers.