On the structural changes in the Brewer-Dobson circulation after 2000
In this paper we present evidence that the observed increase in tropical upwelling after the year 2000 may be attributed to a change in the Brewer-Dobson circulation pattern. For this purpose, we use the concept of transit times derived from residual circulation trajectories and different in-situ measurements of ozone and nitrous dioxide. Observations from the Canadian midlatitude ozone profile record, probability density functions of in-situ N<sub>2</sub>O observations and a shift of the N<sub>2</sub>O-O<sub>3</sub> correlation slopes, taken together, indicate that the increased upwelling in the tropics after the year 2000 appears to have triggered an in…
Quantifying transport into the lowermost stratosphere using simultaneous in-situ measurements of SF&lt;sub&gt;6&lt;/sub&gt; and CO&lt;sub&gt;2&lt;/sub&gt;
Abstract. The seasonality of transport and mixing of air into the lowermost stratosphere (LMS) is studied using distributions of mean age of air and a mass balance approach, based on in-situ observations of SF6 and CO2 during the SPURT (Spurenstofftransport in der Tropopausenregion, trace gas transport in the tropopause region) aircraft campaigns. Combining the information of the mean age of air and the water vapour distributions we demonstrate that the tropospheric air transported into the LMS above the extratropical tropopause layer (ExTL) originates predominantly from the tropical tropopause layer (TTL). The concept of our mass balance is based on simultaneous measurements of the two pas…