A New Tropopause Definition from Simultaneous Ozone-Temperature Profiles.

Historically, the tropopause has been defined arbitrarily in terms of particular features present in a temperature profile. This study suggests a modified definition which is consistent with the assumption that the tropopause is a boundary between the ozone rich air of the stratosphere and the ozone poor air of the troposphere. Several hundred simultaneous temperature and ozone profiles from the middle 1960s and the latter 1970s were examined in order to arrive at a tropopause definition based on temperature and yet consistent with the ozone evidence. These data span a wide range of latitudes and seasons. Agreement between the conventional World Meteorological Organization (WMO) defined tropopause based on temperature lapse rate, and a tropopause defined subjectively on the basis of ozone gradients was found to be only 68%. However, a modification of the WMO tropopause definition, which relaxed the thickness criterion and considered the relative change in lapse rate from troposphere to stratosphere, produced a 95% agreement with the subjective tropopause based on ozone. (Author)