Hannover 2003 – wissenschaftliches Programm

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UP: Umweltphysik

UP 5: Atmosphäre und Klima

UP 5.2: Vortrag

Freitag, 28. März 2003, 11:45–12:00, TIB

Enhanced upper tropical tropospheric COS from biomass burning: Impact on the stratospheric aerosol layer — •Justus Notholt¹, Zhiming Kuang², Markus Rex³, Heinz Bingemer⁴, Rolf Weller³, and Otto Schrems³ — ¹Universitaet Bremen — ²California Institute of Technology — ³Alfred-Wegener-Institut — ⁴J.W.-Goethe-Universitaet

The stratospheric aerosol layer has an important impact on the radiation budget of the stratosphere, its dynamical structure, and chemistry. Carbonyl sulphide (COS) is considered to be a major source of the stratospheric sulphate aerosol during periods of volcanic quiescence. Biomass burning is assumed to contribute 10-20 strength of COS. However, model calculations, based on currently available data, indicate that the net flux of COS is much too small to maintain the observed background aerosol layer. We have measured the COS concentrations at the tropical tropopause and find mixing ratios 20-50 assumed in models. The enhanced COS levels are correlated with high concentrations of biomass burning pollutants like CO and HCN. The analysis of backward trajectories and global maps of fire statistics suggest that biomass burning emissions transported upwards by deep convection are the source of the enhanced COS in the upper tropical troposphere.