A climatology of frozen-in anticyclones in the spring arctic stratosphere over the period 1960-2011

摘要: During springtime, following the stratospheric final warming, intrusions from low latitudes can become trapped at polar in long-lived anticyclones. Such "frozen-in" anticyclones (FrIACs) have occasionally been observed to persist as late August, advected by summer easterlies. In this study, high-resolution advection contour model MIMOSA is used advect a pseudo-potential vorticity tracer. The driven ERA-40 and ERA-Interim reanalyses over period 1960-2011. We first identify remarkable FrIAC event spring 2011. addition, we developed method detect characteristic size of low-latitude into region time transition, Years are classified either Type-A when small, or Type-B large, potentially evolving FrIACs. For occur, require an additional criterion based on in-phase character core anticyclone. 52 analysed years, 9 events identified: 1 1960s, 1980s, 2 1990s 5 2002. predominantly intrusions, which occur association with abrupt early reversal easterlies large heat flux pulse around date wind reversal. Finally, results discussed climatological context.