Changes in stratospheric water vapor

A variety of possible mechanisms for changing stratospheric water vapor have been proposed related to general circulation changes (Nedoluha et. al, 1999; Rosenlof, 2002). Of interest is that over the past 5 years, there is an apparent reduction in stratospheric water vapor as measured from satellite as well as a difference in calculated trends estimated from satellite and a long-term one station balloon record (Randel et. al, 2004). In this presentation we will show the the differences between water vapor data sets and the apparent magnitude of long-term trends in water vapor over the past few decades, extending the work presented in Kley et al. [2000]. The best continuous stratospheric water vapor data started in the early 1980s. For that reason, we will initially concentrate on examining 20-25 year changes. We will use in situ measurements taken by frost point balloon and satellite water vapor measurements to examine temporal changes since the early 1980s. We will then discuss possible reasons for the observed temporal changes by analyzing operational radiosonde data and assimilated wind and temperature fields.