An examination of the transition region between the troposphere and stratosphere using tracer space.
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
Stratosphere Troposphere exchange (STE) is important to study as it controls the chemical composition of the upper troposphere/lower stratosphere (UTLS) and thus the radiative balance of this region. STE also controls the transport of chemicals into the stratosphere which are vital to ozone depletion. The troposphere and the stratosphere have specific chemical characteristics and the transition region between these regions displays characteristics of both. Ozone and water vapour concentrations can be used as tracers for the characteristics of the troposphere and stratosphere. This thesis develops measures in tracer space, which allow the determination of the strength and depth of atmospheric mixing between the troposphere and the stratosphere in extratropical regions.
The application of entropy as a measure of atmospheric mixing as introduced by Patmore and Toumi , is improved in this study. This is a measure of how the ozone and water vapour mixing ratios vary as a result of mixing. An additional metric to give further information on the form of the mixing line in tracer space is also developed. This measure uses the ozone and water vapour mixing ratios at the boundaries of the transition region (BO3 and BH2O). This study uses data from ozonesondes and hygrometers, along with satellite data from the Atmospheric Infrared Sounder (AIRS). The ozone product from AIRS is also validated as part of this study.
The entropy, BO3 and BH2O measures from this study, are successfully shown to detect regions of enhanced mixing in comparison studies. A key comparison shows that the measures developed in this study are able to produce comparable conclusions to higher resolution aircraft data, with regards to mixing. The separation of entropy, BO3 and BH2O, into different categories allows mixing processes to be assigned to some of the categories. Mixing is shown to have geographic preference, with some regions having significantly more mixing. Some categories have preference with regards to their location either poleward or equatorward of the jet stream. In addition, some information as to the direction of the vertical transport, whether stratosphere to troposphere or vice versa, is obtained.