Chemical transition between stratosphere and troposphere in the presence of mountain waves

Correlation between chemical tracers can be used to identify the chemical transition between the stratosphere and troposphere. Using the correlations between ozone and carbon monoxide, measured on the NASA ER-2 aircraft during the STRAT and POLARIS field campaigns (1995-1997), a chemical transition layer, ~ ± 1 km across the extratropical tropopause, was identified [Pan et al., 2004]. This layer was characterized as a mixture of stratosphere and troposphere air. The mechanism that produces and controls the width of this mixing layer is not completely understood. Based on a model simulation combined with the observations, it has been shown that large scale wind shears can be responsible for the mixing layer [ Pan et al., 2006]. Whether and how the mesoscale dynamical processes, such as turbulence and gravity wave breaking, contribute to this mixing layer is not known. During the Terrain –induced Rotor Experiment (T-REX), a suite of chemical tracer instruments, including ozone, carbon monoxide, and water vapor, were deployed on the NSF/NCAR Gulfstream V aircraft (GV), HIAPER. In addition to these longer -lived chemical tracers, aerosol measurements were also made on the GV, and they will be used as additional tracers. One of the objectives of bringing these measurements on board GV is to investigate the impact of mountain waves on the chemical transition layer. We will show the comparison of tracer correlations from T-REX with those from ER-2 measurements at similar latitude and season and address questions of whether the presence of intense mountain waves alters the characteristics and the width of the mixing layer.