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# [AAS11-12] Diffusive separation of major atmospheric components in the stratosphere over Indonesia

Keywords:gravitational separation of atmospheric components, cryogenic air sampler, stratosphere over Indonesia

_{2})

_{,}delta(O

_{2}/N

_{2}), delta

^{15}N of N

_{2}, delta

^{18}O of O

_{2}and delta

^{40}Ar by using a mass spectrometer (Ishidoya and Murayama, 2014), and the measured values showed small but significant decrease with altitude probably due to gravitational separation. The amount of gravitational separation, evaluated as delta values for the mass number difference of 1 (e.g. delta for

^{15}N

^{14}N/

^{14}N

^{14}N), is found to be 11 per meg at the height of 29 km. Based on the observed gravitational separation and a 1-dimensional steady state eddy diffusion/molecular diffusion model, we estimated 1-dimensional vertical eddy diffusion coefficients (K

_{z}) over the equatorial region. By using the average K

_{z}from the surface to the middle stratosphere, we calculated a timescale of the vertical diffusion for a length scale from the surface to the middle stratosphere assuming simple Fickian diffusion. We found that the calculated timescale agrees with the elapsed time since the stratospheric air passed an upper boundary of the tropical tropopause layer (TTL), estimated from tape recorder signals of stratospheric water vapor (Mote et al., 1996), which is significantly smaller than the mean age of air estimated from CO

_{2}concentration (CO

_{2}age). This discrepancy may be due to insensitivity of gravitational separation to mixing processes in Brewer-Dobson circulation, of which variations change the mean age of air significantly.

References

Ishidoya, S. et al. (2013) Gravitational separation in the stratosphere – a new indicator of atmospheric circulation.

*Atmos. Chem. Phys.*, 13, 8787–8796, www.atmos-chem-phys.net/13/8787/2013/, doi:10.5194/acp-13-8787-2013.

Ishidoya, S. & Murayama, S. (2014) Development of high precision continuous measuring system of the atmospheric O

_{2}/N

_{2}and Ar/N

_{2}ratios and its application to the observation in Tsukuba, Japan.

*Tellus B*, 66, 22574, http://dx.doi.org/ 10.3402/tellusb.v66.22574.

Morimoto et al. (2009) A new compact air sampler and its application in stratospheric greenhouse gas observation at Syowa station, Antarctia.

*J. Atmos. Oceanic and Technol.*, 26 10.1175/2009JTECHA1283.1.

Mote, P. W. et al. (1996) An atmospheric tape recorder: The imprint of tropical tropopause temperatures on stratospheric water vapor.

*J. Geophys. Res.*, 101, 3989-4006.