Consideration of Lifetimes of Tracers for the Determination of Stratospheric Age Spectra and the Brewer Dobson Circulation (CoLiBri)

该项目的目标是在考虑到示踪剂寿命的情况下，探索使用寿命长的示踪物质来限制平流层环流。通过迈克尔逊被动大气探测干涉仪（MIPAS）测量，可获得SF6、CFC-11、CFC-12、HCFC-22、CH 4、N2 O和H2O的全球分布。从SF6分布推断平流层空气的年龄是直接的，因为没有平流层汇，并已执行评估布鲁尔多布森环流的强度。为此目的使用其他示踪剂更具挑战性，因为必须考虑它们的特定寿命。由于这些物种的分解取决于海拔和纬度，它们的有效寿命又取决于布鲁尔多布森环流的速度。该项目将采取下列步骤处理这一问题：（a）将制定一种取决于高度和纬度的示踪剂寿命参数，以便使这些气体可用作年龄示踪剂;（B）将从MIPAS SF6测量得出的取决于纬度和高度的空气分布年龄推断出环流和混合模式;（c）根据这些环流和混合模式以及当地寿命估计，将推断出示踪剂分布，并与MIPAS测量的示踪剂分布进行比较;（d）将分析计算的示踪剂分布与测量的示踪剂分布之间的差异，以查明关于混合和输送过程的不适当假设。

The goal of this project is to explore the use of long-lived trace species to constrain stratospheric circulation under consideration of tracer lifetimes. From Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) measurements global distributions of SF6, CFC-11, CFC-12, HCFC-22, CH4, N2O and H2O are available. The inference of age of stratospheric air from SF6 distributions is straight forward since there are no stratospheric sinks, and has already been performed to assess the intensity of the Brewer Dobson circulation. The use of the other tracers for this purpose is more challenging, since their specific lifetimes have to be considered. Since the decomposition of these species is altitude and latitude-dependent, their effective lifetimes depend in turn on the velocity of the Brewer Dobson circulation. This project shall tackle this problem in the following steps: (a) An altitude- and latitude-dependent parametrization of tracer lifetimes will be developed, in order to make these gases usable as age-tracers; (b) from latitude- and altitude dependent age of air distributions derived from MIPAS SF6 measurements, circulation and mixing patterns will be inferred; (c) on the basis of these circulation and mixing patterns and local lifetime estimates, tracer distributions will be deduced and compared to the tracer distributions measured by MIPAS; (d) discrepancies between calculated and measured tracer distributions will be analyzed to identify inappropriate assumptions on mixing and transport processes.