Improving stratospheric and tropical forecasts would improve monthly forecasts for Europe

The results of the recently published study showed that perfect knowledge of the tropical weather conditions would improve at least every fifth forecast in mid- and high latitudes. Perfect knowledge of the stratosphere would also improve monthly forecasts especially over Northern Atlantic and Europe, and especially during periods when the stratospheric polar vortex was weakening. Stratosphere is the part of the atmosphere located at 15–50 kilometers above the ground. 

Monthly forecasts predict weekly mean weather conditions usually up to three to four weeks ahead. Such long forecasts are made possible by so-called teleconnections. Teleconnections link local weather to remote regions where weather conditions can be predicted for longer time. During winter, such teleconnections are mostly associated with the tropics and the stratosphere. 

The researchers applied so-called “nudging”-technique, which allowed perfect simulations of the stratosphere and tropical atmosphere, and then analyzed how the teleconnections from these regions improve the forecast quality. The results of the research improve our understanding of how the teleconnections work in the atmosphere, and this knowledge can be used for improving forecast models. The research is based on forecasts by the European Centre for Medium Range Weather Forecasts (ECMWF), reanalysis data for the winter seasons 1999-2019. 

Additional information: 

Research professor Alexey Karpechko, Finnish Meteorological Institute, alexey.karpechko@fmi.fi 

The research article is available from: Quarterly Journal of Royal Meteorological Society. 

Karpechko, A. Yu., F. Vitart, I. Statnaia, M. A. Balmaseda, A. J. Charlton‐Perez, I. Polichtchouk (2024). The tropical influence on sub-seasonal predictability of wintertime stratosphere and stratosphere–troposphere coupling, Quarterly Journal of the Royal Meteorological Society, 1– 18. https://doi.org/10.1002/qj.4649