Do we understand the transport of trace gases between the troposphere and the stratosphere and the role of upper tropospheric aerosols, water vapor and ozone in climate change?
The importance of the upper troposphere/lower stratosphere (UT/LS) in chemistry and climate problems is well stated in a number of international assessment documents . Within the context of chemical problems one of the largest uncertainties is how much ozone and odd nitrogen is supplied to the troposphere from the stratosphere. Even estimates of the cross tropopause flux of ozone from the stratosphere are uncertain to within 15% or greater. There are fundamental climate change questions related to moistening or drying of the upper troposphere as convective activity changes. For example, it is now understood that the IR cooling of the atmosphere is strongly influenced by upper tropospheric/ lower stratospheric water vapor, aerosols and ozone. On decadal time scales, signals from greenhouse gas changes and signals from the changes in reactive constituents are intertwined and difficult to untangle. The tropopause is a complex internal boundary within the atmosphere related to both radiati
