HDO measurements with MIPAS

We have used high spectral resolution spectroscopic measurements from the MIPAS instrument on the Envisat satellite to simultaneously retrieve vertical profiles of H2O and HDO in the stratosphere and uppermost troposphere. Variations in the deuterium content of water are expressed in the common delta notation, where delta D is the deviation of the Deuterium/Hydrogen ratio in a sample from a standard isotope ratio. A thorough error analysis of the retrievals confirms that reliable delta D data can be obtained up to an altitude of similar to 45 km. Averaging over multiple orbits and thus over longitudes further reduces the random part of the error. The absolute total error of averaged delta D is between 36% and 111 parts per thousand. With values lower than 42 parts per thousand the total random error is significantly smaller than the natural variability of delta D. The data compare well with previous investigations. The MIPAS measurements now provide a unique global data set of high-quality delta D data that will provide novel insight into the stratospheric water cycle.