Water vapor in the upper troposphere and in the stratosphere

Knowledge of the global water vapor distribution and its seasonal changes in the upper troposphere and stratosphere is reviewed. The circulation of water vapor and the exchange processes between troposphere and stratosphere are emphasized in terms of contributions from satellite observation. In contrast to known mean water vapor distributions in the upper troposphere, only single measurements of the mixing ratio have been published for the stratosphere so that the theory about the stratospheric water vapor cycle cannot yet be confirmed. Although expected results of two limb sounding experiments aboard Nimbus 7 will yield new information, recommendations for future improved satellite systems are offered.