Strat-Trop Coupling

Water in its various phases is a controlling influence on the radiative and dynamical balance of the UT/LS and TTL and their response to climate forcing, as well as having an impact on global UV dosage through waters control of heterogeneous stratospheric ozone depletion. For example, in the UT/LS, as well as the TTL, water vapor concentrations are central to the formation, evolution, and lifetime of cirrus that not only play a critical role in the radiative balance in the TTL and UT/LS but also in the dehydration of air in this region. Furthermore, quantifying the importance of convection in transporting boundary layer air to the TTL and lowermost stratosphere, using measurements of water in its various phases, is pivotal for understanding the mechanisms that control the stratospheric water vapor budget and accordingly that of other trace gases and particulates. These scientific issues have in fact been a primary focus of recent NASA airborne campaigns.