edu.ucar.opensky::articles:17303 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-26T15:31:38.354918 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d71v5g8b Chemical behavior of the tropopause observed during the Stratosphere-Troposphere Analyses of Regional Transport experiment 2007-09-26T00:00:00Z publication https://n2t.org/ark:/85065/d71v5g8b https://doi.org/10.1029/2007JD008645 Pan, Laura L. author Bowman, K. author Shapiro, Melvyn A. author Randel, William author Gao, R. author Campos, Teresa author Davis, Christopher A. author Schauffler, Sue author Ridley, Brian A. author Wei, J. author Barnet, C. author UCAR/NCAR - Library publisher During the Stratosphere-Troposphere Analyses of Regional Transport (START) experiment in December 2005, the behavior of the extratropical tropopause was examined under a variety of dynamical conditions. Using in situ measurements of ozone and water vapor, on board the new NSF/NCAR research aircraft Gulfstream V, and data from large-scale meteorological analyses, we address issues of the tropopause definitions and sharpness. Comparisons of the data from two flights show that the sharpness of chemical transitions across the tropopause varies with the sharpness of the static stability change across the tropopause. Using tracer correlations, air masses of mixed stratospheric and tropospheric characteristics are identified. The mixed air mass does not form a uniform mixing layer near the tropopause, but rather shows strong spatial variation. A depth of mixed air (~5 km in vertical distribution) is found on the cyclonic side of the polar jet, where the thermal gradient is weak and significant separation occurs between the thermal and the dynamical tropopause. Away from the jet or on the anticyclonic side of the jet, where the stability gradient is strong, the chemical transition across the tropopause was much more abrupt and shows minimum mixing. In both cases (either significant or minimal mixing), the thermal tropopause is shown to be approximately at the center of the mixing layer, and the altitude relative to the thermal tropopause is found to be an effective coordinate for locating the chemical transition. To further understand the role of the thermal and dynamical tropopause as a chemical transport boundary, tracer correlations are used to examine the chemical characteristics, and the trajectory calculations are used to infer the fate of the air mass between the thermal and dynamic tropopauses in the region of significant separation. The tracer correlation analysis shows that the air mass in this region is a mixture of stratospheric and tropospheric air but predominantly of tropospheric characteristics. Trajectory model calculations show that a significant fraction of the air parcels in this region ended in the mid to lower troposphere, which suggest the irreversible nature of the observed stratospheric intrusion. UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication An edited version of this paper was published by AGU. Copyright 2007 AGU. None eng geoscientificInformation