Downward propagation and statistical forecast of the near-surface weather

We investigate the potential for using the downward propagation of anomalies from the stratosphere to the troposphere in extended-range statistical forecasts. Considering the near-surface zonal mean zonal wind at 60 degrees N and the near-surface temperature in northern Europe as predictands, we find that the inclusion of stratospheric information improves the daily forecast on lead times larger than 5 days. The best forecasts are obtained for predictors in the lower stratosphere. Similar predictions cannot be obtained if the statistical forecast only includes tropospheric information. The simple statistical forecast based on stratospheric winds compares favorably to the forecasts of a state-of-the-art dynamical ensemble prediction system. The statistical forecast can be substantially improved by considering only strong stratospheric anomalies and by predicting averaged values.