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…