Abstract
Abstract. We present optimal estimates of tropospheric H2O and δD derived from radiances measured by the instrument IASI (Infrared Atmospheric Sounding Interferometer) flown on EUMETSAT's polar orbiter METOP. We document that the IASI spectra allow for retrieving H2O profiles between the surface and the upper troposphere as well as middle tropospheric δD values. A theoretical error estimation suggests a precision for H2O of better than 35% in the lower troposphere and of better than 15% in the middle and upper troposphere, respectively, whereby surface emissivity and atmospheric temperature uncertainties are the leading error sources. For the middle tropospheric δD values we estimate a precision of 15–20‰ with the measurement noise being the dominating error source. The accuracy of the IASI products is estimated to about 20–10% and 10‰ for lower to upper tropospheric H2O and middle tropospheric δD, respectively. It is limited by systematic uncertainties in the applied spectroscopic parameters and the a priori atmospheric temperature profiles. We compare our IASI products to a large number of near coincident radiosonde in-situ and ground-based FTS (Fourier Transform Spectrometer) remote sensing measurements. The bias and the scatter between the different H2O and δD data sets are consistent with the combined theoretical uncertainties of the involved measurement techniques.
Highlights
The continuous cycle of evaporation, vapour transport, cloud formation, and precipitation distributes water and energy around the globe
Upper tropospheric humidity is controlled by various processes, e.g., by diffusion, by turbulent mixing, or by detrainment of water condensates inside convective clouds
For reliable climate prediction it is important to identify the relative contribution of the individual processes
Summary
Upper tropospheric humidity is controlled by various processes, e.g., by diffusion, by turbulent mixing, or by detrainment of water condensates inside convective clouds. Today atmospheric water isotopologue research is still limited by the lack of lower to upper tropospheric data (in addition to the precipitation data collected on the Earth’s surface). There has been large progress in observing tropospheric water isotopologues by remote sensing techniques. Schneider et al (2006b, 2010b) document the possibility of the global network of FTS (Fourier Transform Spectrometer) systems for a ground-based remote sensing of tropospheric H2O and δD profiles. The remote sensing techniques can provide continuous data sets and – if performed from space – they offer the possibility for almost global scale observations and novel research opportunities. A good overview of the currently available tropospheric water isotopologue data sets obtained from different in-situ and remote sensing measurement techniques and their potential for atmospheric water cycle research is given by Risi et al (2011a,b). We compare the IASI data to a large number of insitu radiosonde measurements of H2O as well as to groundbased FTS remote sensing measurements of H2O and δD, which are made in coincidence to IASI overpasses
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
