2.1 Simulation of the atmospheric tape recorder signal in HCN

Monday, 8 June 2009: 10:20 AM
Pinnacle A (Stoweflake Resort and Confernce Center)
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.

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