Recorded presentation2.1
Simulation of the atmospheric tape recorder signal in HCN
Robert Walter, Forschungszentrum Jülich, Juelich, Germany; and R. Müller, P. Konopka, G. Günther, J. Grooß, A. Heil, M. Schultz, M. Riese, and H. C. Pumphrey
Variations in the mixing ratio of long-lived trace gases entering
the stratosphere in the tropics are carried upward with the rising
air with the signal being observable throughout the tropical lower
stratosphere. This phenomenon is referred to as "atmospheric tape
recorder". The tape recorder phenomenon has been observed for water
vapour, for CO2, and for CO; for all three trace gases, the cycle
repeats every year. Recently, based on Microwave Limb Sounder (MLS)
and Atmospheric Chemistry Experiment (ACE) satellite measurements,
tape recorder signal has been observed for HCN but with an
approximately two year period. Here we report a model simulation of
the HCN tape recorder for the time period 2005-2008 using the
Chemical Lagrangian Model of the Stratosphere (CLaMS). We find that
the observed pattern of the HCN tape recorder signal can be
reproduced by a model simulation using only emissions from
Indonesian fires as boundary conditions at the ground. This finding
supports the notion that inter-annual variations in biomass burning
in Indonesia, which are strongly influenced by El Nino events,
control the HCN tape recorder signal. This implies that the signal
will have an irregular cycle rather than a two-year cycle.
Session 2, Upper Troposphere/Lower Stratosphere II
Monday, 8 June 2009, 10:20 AM-12:20 PM, Pinnacle A
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