Drought effects on a cornfield in Texas
Corn shows the effects of drought in Texas on 20 August 2013. Credit: USDA/Bob Nichols.

Weather and climate variations on subseasonal to decadal timescales can have enormous social, economic, and environmental impacts, making skillful predictions on these timescales a valuable tool for policy makers. As such, there is growing interest in the scientific, operational, and applications communities in developing forecasts to improve our foreknowledge of events. On subseasonal to seasonal (S2S) timescales, these include risks of such high-impact meteorological events as tropical cyclones, floods, droughts, and heat and cold waves. On seasonal to decadal (S2D) timescales, although the focus broadly remains on precipitation, surface and upper ocean temperatures, and their effects on the probability of extreme meteorological events, competing roles of internal and externally forced variability also become important. The S2S and S2D communities share very similar, if not identical, scientific and technical challenges. These common challenges include forecast initialization and ensemble generation; initialization shock and drift; understanding the onset of model systematic errors; bias correction, calibration, and skill assessment; model resolution; atmosphere-ocean coupling; and linking research, operations, and users.

With this background, International Conferences on Subseasonal to Decadal Prediction featured the Second International Conference on S2S Prediction, the Second International Conference on S2D Prediction, and a joint segment addressing common issues. The conferences brought together the scientists, producers, and users who are at the forefront of S2S and S2D prediction and related research, development, and application areas to foster the exchange of information and knowledge between the communities toward more seamless subseasonal to decadal predictions. More than 350 participants from 38 countries, including over 90 early-career scientists, attended the conferences. Over 140 oral and more than 220 poster presentations highlighted the current level of progress and accomplishments in S2S and S2D predictions and reviewed our current abilities to make skillful predictions. They also identified existing and new challenges for both improving predictions and transitioning the S2S and S2D prediction research efforts to operations.

Surface temperature and precipitation predictions
Subseasonal (left) and decadal (right) predictions from initial conditions in late 2017. The subseasonal prediction shows mean temperature anomalies relative to 1999–2010 climatology in week 3 following 2 November initialization, from 11 models contributing to the Subseasonal to Seasonal Prediction Project. The decadal prediction shows mean temperature anomalies in 2018–2022 relative to 1971–2000 climatology, from 9 models contributing to the WMO Lead Centre for Annual-to-Decadal Climate Prediction. Credit: Subseasonal to Seasonal Prediction Project/ECMWF (left); WMO Lead Centre for Annual-to-Decadal Climate Prediction/UK Met Office (right)

A key success of the conferences was the interaction and information exchange that they facilitated both within the respective S2S and S2D communities and, more important, across these two communities, including their operational components. This led to new collaborations among meeting participants. In addition, several challenges were identified specifically as impeding progress. These include the adverse effects of persistent model biases and systematic errors on predictability and prediction skill, a critical lack of understanding at the process level, issues with initialization shock and bias corrections, and a lack of robust improvements with higher spatial resolutions.

The meeting agenda and presentations are available online.

The conferences were planned by the Executive Committee; the S2S Scientific Organizing Committee (SOC), chaired by Andrew Robertson and Frederic Vitart; the S2D SOC, chaired by Doug Smith and William Merryfield; Organizing Committee members Gokhan Danabasoglu, Heidi Allen, Estelle De Coning, Catherine Michaut, Mike Patterson, Michel Rixen, Melanie Russ, and Matthias Tuma; and Kristan Uhlenbrock and Jeff Becker from the U.S. Climate Variability and Predictability Program.

—Gokhan Danabasoglu (gokhan@ucar.edu), Climate and Global Dynamics Laboratory, National Center for Atmospheric Research, Boulder, Colo.; Frederic Vitart, European Centre for Medium-Range Weather Forecasts, Shinfield Park, Reading, U.K.; and William J. Merryfield, Canadian Centre for Climate Modelling and Analysis, Environment Canada, University of Victoria, B.C., Canada


Danabasoglu, G.,Vitart, F., and Merryfield, W. J. (2019), Subseasonal to decadal predictions: Successes and challenges, Eos, 100, https://doi.org/10.1029/2019EO114937. Published on 31 January 2019.

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