The polar vortex usually encompasses the polar region in the winter stratosphere, but sometimes shifts markedly away from its normal position and distorts during stratospheric sudden warmings (SSWs).
A stratospheric sudden warming is perhaps one of the most radical changes of weather observed in our planet. As numerical weather prediction models have been improved, including better representation of the stratosphere, an extensive amount of studies have been investigating forecasts for major stratospheric sudden warmings (MSSWs), which affect all layers of the atmosphere, changing wind circulation patterns and space weather effects like the aurora.
Whereas most previous studies employed single systems for a limited number of MSSWs, a new study published in Advances in Atmospheric Sciences (AAS) sought to verify multi-system MSSW forecasts using hindcasts of four systems archived in the subseasonal-to-seasonal prediction project database. AAS is published by Springer and hosted by the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences (CAS).
"The target hindcast period extended from 1998/99 to 2012/13, including 12 MSSWs," said the author, Prof. Masakazu TAGUCHI, from the Department of Earth Science, Aichi University of Education in Japan, "the results show that all four systems can be judged to be skillful for five-day MSSW forecasts when averaged across all available MSSWs."
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