Trends in Tropospheric Humidity and Water Vapor from 1973–2008

Recent changes in tropospheric (up to 100mb) specific (q) and relative humidity (RH) and precipitable water (PW) are analyzed using a newly homogenized global daily radiosonde data set, which contains about 880 stations with sufficient observations during 1973-2008. The homogenization removes most of the major discontinuities in the radiosonde humidity records and improves the spatial coherency of the trends in the humidity and PW. It is found that most of the RH changes in the raw radiosonde data are likely due to inhomogeneities resulting from instrumental and observational changes. The q and PW trends in the homogenized data are largely controlled by (homogenized) tropospheric temperature changes. Results for changes in temperature, q, and RH at different levels and for PW will be presented.