Subseasonal to seasonal (S2S) climate variability and predictions

亚季节到季节（S2S）时间尺度是指从一周到一个季节的时间尺度。一个有用的超过一周的天气预报具有相当大的社会经济价值。本研究的长期目标是提高对大气变率的认识，为S2S预测极端风、降水和气温发生概率等大气条件提供依据。未来5年，我们将重点关注S2S气候变率的关键过程。特别是，我们将研究热带-温带相互作用和大气远相关。我们的目标是量化温带和高纬度地区的S2S预测技能，确定可预测性的限制，并确定熟练的S2S预测机会。不同复杂程度的数值模型将被用来模拟过程，对物理机制进行诊断分析，并进行预测实验。国际S2S项目数据库包括10多个运行S2S模式的再预报和预报数据，将用于评估S2S预报技能并帮助确定可预测性的来源。预计这项工作将澄清与亚季节到季节变率有关的一些重要问题，并有助于加拿大S2S天气预报能力的发展。

The subseasonal to seasonal (S2S) time scale refers to that ranging from a week to a season. A useful weather forecast beyond a week is of considerable socio-economic value. The long-term objective of this research is to improve the understanding of the atmospheric variability that provides a basis for S2S forecasting of atmospheric conditions including the probability of extreme winds, precipitation, and air temperature. In the next five years we propose to focus on key processes in the S2S climate variability. In particular, we will study the tropical-extratropical interactions, and atmospheric teleconnections. We aim to quantify S2S forecast skill in the extratropical and high-latitude regions, to determine the limits of predictability, and to identify opportunities for skillful S2S forecasts. Numerical models with different complexities are to be utilized to simulate the processes, perform diagnostic analyses for physical mechanisms, and conduct forecast experiments. The database of the international S2S project which includes re-forecast and forecast data of more than 10 operational S2S models will be utilized to assess the S2S forecast skill and to help to identify the sources of predictability. It is expected that this work will clarify some important issues related to subseasonal to seasonal variability, and contribute to the development of S2S weather forecasting capability in Canada.