Het is een fascinerend verschijnsel. Dat staat los van de troposferische implicaties. Vind ik.
Nu begrijp ik dat er de meeste vooral geboeid zijn door wat het betekent voor het weer op neushoogte. Recent is onderstaande studie verschenen waarin gekeken wordt naar split en displacement SSWs met hun impact op de AO. Ik heb weinig tijd. Dus zelf maar even bekijken. Maar er is in ieder geval weinig verschil. De beperkte omvang van daadwerkelijke SSWs l/blijkt dus een belangrijke rol te spelen.
"Do split and displacement sudden stratospheric warmings have different annular mode signatures?
Amanda C. Maycock and Peter Hitchcock
Abstract
Sudden stratospheric warmings (SSWs) contribute to intraseasonal tropospheric forecasting
skill due to their surface impacts. Recent studies suggest these impacts depend upon whether the polar vortex splits or is displaced during the SSW. We analyze the annular mode signatures of SSWs in a 1000 year IPSL-CM5A-LR simulation. Although small differences in the mean surface Northern Annular Mode (NAM) index following splits and displacements are found, the sign is not consistent for two independent SSW algorithms, and over 50 events are required to distinguish the responses. We use the wintertime correlation between extratropical lower stratospheric wind anomalies and the surface NAM index as a metric for two-way stratosphere-troposphere coupling and find that the differences between splits and displacements, and between classification methodologies, can be simply understood in terms of their mean stratospheric wind anomalies. Predictability studies should therefore focus on understanding the factors that determine the persistence of these anomalies following SSWs"
Uit het artikel:
Recent studies using reanalysis data have suggested that the tropospheric response to SSWs depends upon the type of event, categorized as either a vortex split or displacement [Mitchell et al., 2013; Seviour et al., 2013] (M13 and S13, respectively). These studies found that the surface anomalies following splits project more strongly onto the Northern Annular Mode (NAM) thanfor displacement events. This is in contrast with Charlton and Polvani [2007] (CP07) and Cohen and Jones [2011] who did not find a consistent difference in the impact of splits and displacements using a different method for identifying SSWs.