Lagrangian approach to quantifying processes influencing the lower stratosphere using Aura MLS observations

The Aura Microwave Limb Sounder (MLS) measures vertical profiles of atmospheric composition, humidity and cloud ice from the upper troposphere to the mesosphere. We have recently developed a set of MLS "Lagrangian Trajectory Diagnostics", which report the location of airmasses observed by MLS during the period from 15-days prior to 15-days following each MLS observation. This paper describes these diagnostics, and gives examples of their application to studies of process affecting the upper troposphere and lower stratosphere. In particular, we employ the trajectory diagnostics in a set of "Match" calculations that identify cases where MLS observes the same airmass on multiple days. We demonstrate the use of the Match approach to quantify chemical destruction of ozone in the polar lower stratosphere each Arctic and Antarctic winter, and compare results from selected years to ozone destruction estimates from previous studies. In addition, we apply the Match approach to the MLS observations of nitrous oxide, a long lived tracer, and explore the use of these to validate the transport calculations.