TY  - JOUR
A1  - Bönisch, Harald
A1  - Engel, Andreas
A1  - Curtius, Joachim
A1  - Birner, Thomas
A1  - Hoor, Peter
T1  - Quantifying transport into the lowermost stratosphere using simultaneous in-situ measurements of SF₆ and CO₂
T2  - Atmospheric chemistry and physics
N2  - 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 passive tracers and the assumption that transport into the LMS can be described by age spectra which are superposition of two different modes. Based on this concept we conclude that the stratospheric influence on LMS composition is strongest in April with extreme values of the tropospheric fractions (alpha1) below 20% and that the strongest tropospheric signatures are found in October with alpha1 greater than 80%. Beyond the fractions, our mass balance concept allows us to calculate the associated transit times for transport of tropospheric air from the tropics into the LMS. The shortest transit times (<0.3 years) are derived for the summer, continuously increasing up to 0.8 years by the end of spring. These findings suggest that strong quasi-horizontal mixing across the weak subtropical jet from summer to mid of autumn and the considerably shorter residual transport time-scales within the lower branch of the Brewer-Dobson circulation in summer than in winter dominates the tropospheric influence in the LMS until the beginning of next year's summer.
Y1  - 2009
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/6713
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30-68275
SN  - 1680-7316
SN  - 1680-7324
N1  - © Author(s) 2009. This work is distributed under the Creative Commons Attribution 3.0 License.
VL  - 9
SP  - 5905
EP  - 5919
PB  - European Geosciences Union
CY  - Katlenburg-Lindau
ER  -