An update on the uncertainties of water vapor measurements using cryogenic frost point hygrometers

To reduce these problems of long-term data series, all measurements should include an estimate of their uncertainty and a description of their sources. Here we present an update of the uncertainties for tropospheric and stratospheric water vapor observations using the cryogenic frost point hygrometer (CFH).

The largest source of measurement uncertainty is the controller stability, which is discussed here in detail. We describe a method to quantify this uncertainty for each profile based on the measurements. We also show the importance of a manufacturer-independent ground check, which is an essential tool to continuously monitor the uncertainty introduced by instrument variability.