Upper Tropospheric and Lower Stratosphere Water Vapor Observations from Satellite, Balloon and Aircraft: What Have We Learned over the Past 70 Years?

The first stratospheric water vapor measurements were made using an aircraft frost point hygrometer in 1943; while originally intended to assess when contrails would form, these measurements were then used to determine mass transport throughout the stratosphere.  Balloon measurement of stratospheric water started in the 1960s, and the first global satellite measurements were in 1978.  A limited number of stations have made measurements long enough to assess trends, and there have been numerous aircraft measurements using multiple techniques to examine processes in the upper troposphere and lower stratosphere (UTLS).  These are of interest from a climate perspective, due to the radiative impact of UTLS water, and because analysis of variations in UTLS water leads to increased understanding of both atmospheric transport and microphysical processes.  This presentation will provide a brief review of UTLS water vapor measurements and key findings learned from analysis of aircraft, balloon and satellite measurements.