Vertical structure of the extratropical quasi‐biennial oscillation in ozone, temperature, and wind derived from ozonesonde data

Abstract

An analysis of the extratropical ozone sounding data shows that ozone, temperature, and wind as well as tropopause height reveal interannual variability with timescales in the range 24–30 months. This quasi‐biennial variability is noticed, as a rule, in a whole range of ozone sounding heights (0–35 km) and connected with the equatorial quasi‐biennial oscillation (QBO). The QBOs in ozone and temperature are revealed differently in the middle and lower stratosphere as well as in the troposphere. In the middle stratosphere a downward phase progression of the ozone QBO is noticed similar to that of the equatorial dynamical QBOs. The rate of the phase descent of the QBO depends on the geographical region and varies from 0.5 km/month to 1 km/month. In the northern hemisphere the rate is greatest in the polar region but lowest in the subtropics. Local maxima are noticed in the vertical structures of the ozone QBOs. In the northern midlatitudes these maxima are centered at heights of about 12, 20, and 30 km. In the lower stratosphere the QBO in ozone is in phase with that in temperature. Mean amplitudes of the temperature QBO in the troposphere are close to those in the stratosphere. The downward phase progression of the temperature QBO is noticed in the northern midlatitude stratosphere. There is an abrupt phase shift between the QBOs in ozone and temperature in the lower stratosphere and those in the middle troposphere. Over the North American stations the phase shift is that the temperature QBOs in the troposphere are in opposite phase with those in the stratosphere. In zonal and meridional winds the QBO are revealed in the northern midlatitudes. In contrast with the QBOs in ozone and temperature, the wind QBOs reveal the small rate of the phase changing with height. There are no significant phase shifts between the wind QBO in the lower stratosphere and that in the troposphere. The maximum amplitudes of the wind QBO are noticed in the vicinity of the tropopause position and at heights of 25–30 km. Amplitudes of the QBO in zonal wind are close to those in meridional wind. The QBO of tropopause height exposed in the northern hemisphere has the greatest amplitude over Japan. The tropopause height QBO is in opposite phase (in phase) with the QBOs in ozone and temperature in the lower stratosphere (troposphere). Vertical structures of the QBOs obtained for ozone, temperature, and wind in the stratosphere as well as the corresponding QBO of tropopause height support a hypothesis that the extratropical QBO is caused by quasi‐biennial forcing of the mean diabatic meridional circulation by planetary‐scale waves with the resulting modulation of vertical advection.