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。

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.