Update of the meteorological situation

10th February 2005

The Arctic vortex in the lower stratosphere continues to be unusually cold and stable. A disturbance over the past two weeks culminated in a minor warming during the first days of February with a reversal of the zonal mean temperature gradient between 90ºN and 60ºN at altitudes around 25 km (10 hPa). However, this event had little impact on lower altitudes where the cold. stable conditions are necessary precursors for ozone depletion. At altitudes around 18km, the area where polar stratospheric clouds can form peaked in late January and has remained unusually large since then.

Forecasts for the next days show further radiative cooling and a decay of the dynamical activity that was related to the recent weak warming. In the less reliable 8-10 day forecasts there are signs of increased disturbances. However these forecasts do not show clear signs of an impending major warming pulse. Taking into account the time any major warming would need to propagate to lower levels, it seems to be likely that temperatures will remain low enough for polar stratospheric clouds to form in the lower stratosphere for at least another two weeks.

The conditions in the Arctic ozone stratosphere remain conducive to ozone loss. Scientists will continue to monitor the situation closely.