Chapter 11
Stratospheric Age-Of-Air and SF6
Simulations with Silam
Rostislav Kouznetsov, Mikhail Sofiev, Julius Vira and Gabriele Stiller
Abstract The spatial distribution of Age of Air (AoA) in the stratosphere has been
extensively used to evaluate and compare general circulation and chemical transport
models. We performed multi-decade simulations of SF6 and several AoA tracers
in the atmosphere with Silam chemistry-transport model driven with ERA-Interim
reanalysis. The resulting distributions of AoA agree well with each other and with
simulations made earlier, however disagree with AoA derived from observed SF6
concentrations in polar areas. The simulations of SF6 were made in two variants:
fully passive passive, and with account for mesospheric depletion and for gravitational separation. The results indicate a good agreement with observations by MIPAS
satellite instrument for non-passive SF6, and have substantial discrepancies in polar
areas for passive SF6. Thus we conclude that the discrepancy between SF6 and modelled AoA originates from the violation of the assumption of the SF6 passiveness.
11.1 Introduction
Age of air (AoA) at some point in stratosphere is defined as the average time elapsed
since molecules of air there had last been in troposphere. The spatial distribution of
AoA in the stratosphere is a good indicator of global atmospheric circulation and
had been extensively used to evaluate and compare general circulation and chemical
transport models in the stratosphere [10]. In particular, numerous studies use AoA
as a diagnostics of stratospheric circulation.
R. Kouznetsov (B) · M. Sofiev
Finnish Meteorological Institute, Helsinki, Finland
e-mail: Rostislav.Kouznetsov@fmi.fi
R. Kouznetsov
Obukhov Inst. of Atmospheric Physics, Moscow, Russia
J. Vira
Cornell University, Ithaca, NY, USA
G. Stiller
Karlsruhe Institute of Technology, Karlsruhe, Germany
© Springer Nature Switzerland AG 2020
C. Mensink et al. (eds.), Air Pollution Modeling and its Application XXVI,
Springer Proceedings in Complexity,
https://doi.org/10.1007/978-3-030-22055-6_11
65
Stratospheric Age-Of-Air and SF6
Simulations with Silam
Rostislav Kouznetsov, Mikhail Sofiev, Julius Vira and Gabriele Stiller
Abstract The spatial distribution of Age of Air (AoA) in the stratosphere has been
extensively used to evaluate and compare general circulation and chemical transport
models. We performed multi-decade simulations of SF6 and several AoA tracers
in the atmosphere with Silam chemistry-transport model driven with ERA-Interim
reanalysis. The resulting distributions of AoA agree well with each other and with
simulations made earlier, however disagree with AoA derived from observed SF6
concentrations in polar areas. The simulations of SF6 were made in two variants:
fully passive passive, and with account for mesospheric depletion and for gravitational separation. The results indicate a good agreement with observations by MIPAS
satellite instrument for non-passive SF6, and have substantial discrepancies in polar
areas for passive SF6. Thus we conclude that the discrepancy between SF6 and modelled AoA originates from the violation of the assumption of the SF6 passiveness.
11.1 Introduction
Age of air (AoA) at some point in stratosphere is defined as the average time elapsed
since molecules of air there had last been in troposphere. The spatial distribution of
AoA in the stratosphere is a good indicator of global atmospheric circulation and
had been extensively used to evaluate and compare general circulation and chemical
transport models in the stratosphere [10]. In particular, numerous studies use AoA
as a diagnostics of stratospheric circulation.
R. Kouznetsov (B) · M. Sofiev
Finnish Meteorological Institute, Helsinki, Finland
e-mail: Rostislav.Kouznetsov@fmi.fi
R. Kouznetsov
Obukhov Inst. of Atmospheric Physics, Moscow, Russia
J. Vira
Cornell University, Ithaca, NY, USA
G. Stiller
Karlsruhe Institute of Technology, Karlsruhe, Germany
© Springer Nature Switzerland AG 2020
C. Mensink et al. (eds.), Air Pollution Modeling and its Application XXVI,
Springer Proceedings in Complexity,
https://doi.org/10.1007/978-3-030-22055-6_11
65