TY  - JOUR
A1  - Bönisch, Harald
A1  - Engel, Andreas
A1  - Birner, Thomas
A1  - Hoor, Peter
A1  - Tarasick, David W.
A1  - Ray, Eric A.
T1  - On the structural changes in the Brewer-Dobson circulation after 2000
T2  - Atmospheric chemistry and physics
N2  - 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 N2O observations and a shift of the N2O-O3 correlation slopes, taken together, indicate that the increased upwelling in the tropics after the year 2000 appears to have triggered an intensification of tracer transport from the tropics into the extratropics in the lower stratosphere below about 500 K. This finding is corroborated by the fact that transit times along the shallow branch of the residual circulation into the LMS have decreased for the same time period (1993–2003). On a longer time scale (1979–2009), the transit time of the shallow residual circulation branch show a steady decrease of about −1 month/decade over the last 30 yr, while the transit times of the deep branch remain unchanged. This highlights that changes in the upwelling across the tropical tropopause are not sufficient as an indicator for changes in the entire Brewer-Dobson circulation.
Y1  - 2011
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/25228
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-252288
SN  - 1680-7324
VL  - 11
SP  - 3937
EP  - 3948
PB  - European Geosciences Union
CY  - Katlenburg-Lindau
ER  -