An upper-branch Brewer–Dobson circulation index for attribution of stratospheric variability and improved ozone and temperature trend analysis

摘要

We find that wintertime temperature anomalies near 4 hPa and50° N/S are related, through dynamics, to anomalies in ozone andtemperature, particularly in the tropical stratosphere but also throughoutthe upper stratosphere and mesosphere. These mid-latitude anomalies occur ontimescales of up to a month, and are related to changes in wave forcing. Achange in the meridional Brewer–Dobson circulation extends from the middlestratosphere into the mesosphere and forms a temperature-change quadrupolefrom Equator to pole. We develop a dynamical index based on detrended,deseasonalised mid-latitude temperature. When employed in multiple linearregression, this index can account for up to 60 % of the total variabilityof temperature, peaking at  ∼  5 hPa and dropping to 0 at  ∼  50and  ∼  0.5 hPa, respectively, and increasing again into the mesosphere. Ozonesimilarly sees up to an additional 50 % of variability accounted for, witha slightly higher maximum and strong altitude dependence, with zeroimprovement found at 10 hPa. Further, the uncertainty on all equatorialmultiple-linear regression coefficients can be reduced by up to 35 and20 % in temperature and ozone, respectively, and so this index is animportant tool for quantifying current and future ozone recovery.