1 / 26

The inter-comparison of IASI water vapour retrieval schemes

The inter-comparison of IASI water vapour retrieval schemes. Martin Stengel , Marc Schröder, Nadine Schneider, Theo Steenbergen, Marc Schwärz, Katie Lean, Roger Saunders, Adrian Doicu. Outline. Background IASI assessment in GlobVapour Retrieval systems Comparison approach First results

arion
Download Presentation

The inter-comparison of IASI water vapour retrieval schemes

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The inter-comparison of IASI water vapourretrieval schemes Martin Stengel, Marc Schröder, Nadine Schneider, Theo Steenbergen,Marc Schwärz, Katie Lean, Roger Saunders, Adrian Doicu

  2. Outline • Background • IASI assessment in GlobVapour • Retrieval systems • Comparison approach • First results • Outlook

  3. Outline • Background • IASI assessment in GlobVapour • Retrieval systems • Comparison approach • First results • Outlook

  4. Background • Previous studies and investigations have shown the benefit of Infrared Atmospheric Sounding Interferometer (IASI) measurements for atmospheric analysis in one- and multi-dimensional analysis schemes. • Beside IASI’s application in e.g. NWP frameworks, growing long-term records of its measurements suggest the utilization of IASI retrieval products of atmospheric parameters for climate monitoring and subsequently for e.g. evaluation of climate models (i.e. hintcast simulations) • The (inter-) comparisons of IASI retrieval schemes has only been tackled by a few studies so far (e.g. Hilton et al., 2009)

  5. Background • As a substantial part of the ESA DUE GlobVapour project, DWD and project partners are conducting a comprehensive IASI retrieval inter-comparison study. • The focus of this assessment is directed towards the identification of an optimal algorithm scheme for climate monitoring of atmospheric water vapour. • Comparison criteria include the retrieval quality and application limitations, but also the performance and applicability in re-processing frameworks. • The study will include several IASI retrieval algorithms provided by the project partners (DLR, UK Met-Office, DWD) and additionally participating groups (EUMETSAT, NOAA).

  6. Background • Hilton et al. (2009): An investigation into the performance of retrievals of temperature and humidity from IASI: • Nine different physically based retrieval schemes were applied to 25 clear sky cases IASI footprints over the Gulf of Mexico, which were characterized by near-coincident dropsonde observations taken during the Joint Airborne IASI Validation Experiment (JAIVEx) campaign of April-May 2007 • On focus of this study: Can fine vertical structure and sharp gradients be seen in the retrievals even though if they are not present in the a priori profile information used by the retrieval system.

  7. Background • Case study of dry layer atapprox. 720 hPa: (from Hilton et al., 2009)

  8. Background • Case study of dry layer atapprox. 720 hPa: (from Hilton et al., 2009)

  9. Background • Assessing the impact of type of background information (from Hilton et al., 2009)

  10. Background • Assessing the impact of type of background information (from Hilton et al., 2009)

  11. Outline • Background • IASI assessment in GlobVapour • Retrieval systems • Comparison approach • First results • Outlook

  12. IASI assessment in GlobVapour • The focus of this assessment is directed towards the identification of an optimal algorithm scheme for monitoring of atmospheric water vapour. • It was planned to include the ‘winner’-algorithm in a joint-retrieval processor (together with SEVIRI LCWV) to produce a superior water vapour dataset for three tropospheric layers, benefiting from the high quality, vertically-resolved IASI retrievals and the high temporal resolution of SEVIRI retrievals (Nowcasting SAF retrieval system) • Goals: • Determination of absolute accuracy of each participating retrieval by comparison with ground-based reference measurements • Analysis of the deviations among the retrieval systems and their strengths and weaknesses with respect to a long-term analysis of the water vapour in a reprocessing framework

  13. IASI assessment in GlobVapour • Participating groups • DWD (1D-Var) • UK Met Office (1D-Var) • DLR - German Aerospace Center • NOAA • EUMETSAT (v4, v5) • Data production • The IASI retrieval algorithms will be run at each of the participating institutions. • Provision of retrieved profiles of temperature and specific humidity to DWD (including additional information, e.g. vertical grid, latitude, longitude, quality flags and time stamps, …) • All this information will be inferred for 121 footprints in a 11-by-11 footprints box, which is centered at the corresponding reference sites.

  14. IASI assessment in GlobVapour • Reference sites & data (3 ARM, 2 GUAN sites) • Lindenberg, Sodankyla, Barrow, Lamont, Nauru • Six months considered (July, August 2007, and January, June, August, December 2008) • TCWV (ground-based MWR), WV profiles (radiosondes)

  15. IASI assessment in GlobVapour • Data availability

  16. IASI assessment in GlobVapour • Data availability 1 3 2

  17. IASI assessment in GlobVapour • Selection criteria: • Select closest clear-sky-retrieval pixel (with respect to the reference site) from each retrieval • Select case if MWR ‘says’ clear-sky (LWP .lt. threshold) • All selected pixels from all retrievals have to match site’s location within 0.75° distance and temporally match the ground radiosonde measurement within ± 3 hours

  18. IASI assessment in GlobVapour • Case 1: June 2008, Lindenberg • UKMO 1D-Var only partly available

  19. IASI assessment in GlobVapour • Case 1: June 2008, Lindenberg • UKMO 1D-Var only partly available ERA-Interim forecast might bevery closed to radiosondes sincethey are assimilated

  20. IASI assessment in GlobVapour • Case 2: August 2008, Lamont

  21. IASI assessment in GlobVapour • Case 2: August 2008, Lamont

  22. IASI assessment in GlobVapour • Case 3: July 2007, Lamont

  23. IASI assessment in GlobVapour • Case 3: July 2007, Lamont Missing bias correction?!

  24. Summary and Outlook • IASI retrieval assessment has started within the ESA DUE GlobVapour project • First results have been collected and inter-compared • More data needed to draw possible conclusions • NOAA retrieval data will included soon, maybe also EUMETSAT v5

  25. Summary and Outlook • Also use other pixels in comparisons… • Advanced validation tools to be used: • Software following the approach of Pougatchev (2008), Pougatchev et al. (2009). • The model developed accounts for differences in horizontal, vertical, and temporal resolution as well as noise level of the IASI instrument and radiosondes. • We plan to adapt this metho-dology also to the problem ofcomparison of TCWV estimatesto ground-based observationsand to comparisons among theproducts.

  26. Fiona Hilton, Paolo Antonelli, Xavier Calbet, Tim Hultberg, Lydie Lavanant, Xu Liu, Guido Masiello, Stuart Newman, Jonathan Taylor, Carmine Serio, Daniel Zhou, 2009: AN INVESTIGATION INTO THE PERFORMANCE OF RETRIEVALS OF TEMPERATURE AND HUMIDITY FROM IASI, Conference proceeding EUMETSAT conference 2009 • N. Pougatchev, T. August, X. Calbet, T. Hultberg, O. Oduleye, P. Schlüssel2, B. Stiller, K. St. Germain, and G. Bingham, 2009: IASI temperature and water vapor retrievals – error assessment and validation, Atmos. Chem. Phys., 9, 6453–6458 • Pougatchev, N. S.: Validation of atmospheric sounders by correlative measurements, Appl. Opt., 47,4739–4748, 2008. www.globvapour.info Thank you

More Related