Scientists and forecasters working through the World Meteorological Organization’s World Weather Research Programme (WWRP) advanced the idea of a long-term, international “Polar Prediction Project.” The goal was to improve environmental prediction in the Arctic and Antarctic, where sparse observations make forecasts harder than at lower latitudes.
The Polar Prediction Project started as a roughly 10-year effort (2013–2022) under WMO/WWRP. It created a formal international structure for coordinating research, observations, and forecast-system development focused on polar regions.
PPP’s Steering Group published an implementation plan describing the “Year of Polar Prediction” (YOPP) as PPP’s flagship activity. The plan set out a phased approach—preparation, a core intensive period, and a consolidation phase—linking enhanced observations with modelling, verification (forecast checking), and user engagement.
As YOPP approached launch, partners outlined “Special Observing Periods” (SOPs) with extra measurements such as more frequent weather-balloon launches and additional buoy data. These SOPs were designed to create concentrated datasets that could be used to test how extra polar observations change forecast quality.
YOPP’s core effort began with an official launch event timed with the start of major coordinated activities. A key emphasis was that operational weather centers and research teams would work from common observing and modelling plans, so results could be compared across countries and systems.
ECMWF began generating an extended global forecast dataset to support YOPP research. By archiving extra model output beyond routine products, the dataset made it easier to diagnose why forecasts succeed or fail in polar conditions and to connect model behavior with observations.
The first Arctic Special Observing Period ran in late winter 2018, increasing routine measurements such as radiosonde (weather balloon) launches. The intent was to reduce data gaps during a challenging season for forecasting and to provide a clear test period for observing-system experiments.
A second Arctic SOP ran during summer 2018, again boosting routine observations and coordinating additional measurements at selected “supersites.” This helped capture different polar weather and sea-ice processes than in winter, allowing comparisons across seasons.
YOPP’s Antarctic SOP ran across the austral summer, extending enhanced observing to the Southern Hemisphere. This supported YOPP’s aim of covering a full annual cycle in both polar regions and testing forecast systems under Antarctic conditions.
Starting in June 2019, YOPP shifted from intensive observing into a “consolidation phase” focused on turning collected data into lasting improvements. Activities emphasized data release, common evaluation methods, and translating research findings into better operational forecast products for polar users.
The planned core phase of YOPP ran from May 2017 to June 2019, centered on 2018. By the end of this period, the project had produced coordinated sets of observations and model output intended for forecast verification, process studies, and model improvement work.
One legacy effort, YOPPsiteMIP, organized process-based evaluation of forecast models using high-quality “supersite” observations. Standardized “Merged Observatory Data Files” (MODFs) made it easier to compare measurements across sites and match them to model output during the Arctic SOP periods.
Year of Polar Prediction (YOPP) coordinated observing period (2017–2019)