Sudden stratospheric warmings and their mesospheric precursors

Contact: Hauke Schmidt, Elisa Manzini, Felix Bunzel, Andreas Miller

In extreme cases, the deceleration of the polar night jet forced by the dissipation of planetary waves, can lead to a reversal of the zonal-mean zonal wind at 10 hPa at 60 deg N, and cause the occurrence of a major sudden stratospheric warming (SSW) event. During these events, which usually last for not longer than a few weeks, the polar cap temperature may exceed the climatology by up to 30 K for a few days.

The figures above show zonal-mean zonal wind and temperature anomalies of a composite of 19 major SSW events, obtained from a 20-year HAMMONIA model simulation. The central date (day 0) is defined as the day of the zonal-mean zonal wind reversal at 10 hPa at 60 deg N. The time axis extends from 15 days before to 15 days after the central date. The stratospheric warming is clearly accompanied by a mesospheric cooling. At least from the temperature anomalies, it could be argued if a mesospheric cooling signal, a mesospheric precursor, shows up a few days before the stratospheric warming signal occurs.