• Bi, L., Jung J. A. , Morgan M. C. , and Le Marshall J. F. , 2011: Assessment of assimilating ASCAT surface wind retrievals in the NCEP Global Data Assimilation System. Mon. Wea. Rev.,139, 3405–3421.

  • Desroziers, G., Berre L. , Chapnik B. , and Poli P. , 2005: Diagnosis of observation, background and analysis-error statistics in observation space. Quart. J. Roy. Meteor. Soc., 131, 33853396.

    • Search Google Scholar
    • Export Citation
  • Figa-Saldaña, J., Wilson J. J. W. , Attema E. , Gelsthorpe R. , Drinkwater M. R. , and Stoffelen A. , 2002: The Advanced Scatterometer (ASCAT) on the Meteorological Operational (MetOp) platform: A follow on for the European wind scatterometers. Can. J. Remote Sens., 28, 404412.

    • Search Google Scholar
    • Export Citation
  • Gustafsson, H., Berre L. , Hornquist S. , Huang X. Y. , Lindskog M. , Navascues B. , Mogensen K. S. , and Thorsteinsson S. , 2001: Three-dimensional variational data assimilation for a limited area model. Part I: General formulation and background constraint. Tellus, 53A, 425446.

    • Search Google Scholar
    • Export Citation
  • Hersbach, H., and Janssen P. , 2007: Operational assimilation of surface wind data from the MetOp ASCAT scatterometer at ECMWF. ECMWF Newsletter, No. 113, ECMWF, Reading, United Kingdom, 6–8.

  • Hersbach, H., Stoffelen A. , and de Haan S. , 2007: An improved C-band scatterometer ocean geophysical model function: CMOD5. J. Geophys. Res., 112, C03006, doi:10.1029/2006JC003743.

    • Search Google Scholar
    • Export Citation
  • Hollingsworth, A., and Lönnberg P. , 1986: The statistical structure of short-range forecast errors as determined from radiosonde data. Part 1: The wind field. Tellus, 38A, 111136.

    • Search Google Scholar
    • Export Citation
  • Järvinnen, H., and Unden P. , 1997: Observation screening and first-guess quality control in the ECMWF 3D-Var data assimilation system. Research Department Tech. Memo. 236, ECMWF, Reading, United Kingdom, 34 pp.

  • Lindskog, M., and Coauthors, 2001: Three-dimensional variational data assimilation for a limited area model. Part II: Observation handling and assimilation experiments. Tellus, 53A, 447468.

    • Search Google Scholar
    • Export Citation
  • Pirkka, O., 2010: Feasibility of assimilating ASCAT surface winds into a limited area. M.S. thesis, Dept. of Physics, University of Helsinki, 81 pp. [Available online at https://helda.helsinki.fi/bitstream/handle/10138/20968/feasibil.pdf.]

  • Portabella, M., and Stoffelen A. , 2004: A probabilistic approach for SeaWinds data assimilation. Quart. J. Roy. Meteor. Soc., 130, 126.

    • Search Google Scholar
    • Export Citation
  • Singh R., Pal P. K. , Kishtawal C. M. , and Joshi P. C. , 2008: The impact of variational assimilation of SSM/I and QuikSCAT satellite observations on the numerical simulation of Indian Ocean tropical cyclones. Wea. Forecasting,23, 460–476.

  • Stoffelen, A., 1998: Toward the true near-surface wind speed: Error modeling and calibration using triple collocation. J. Geophys. Res., 103 (C4), 77557766.

    • Search Google Scholar
    • Export Citation
  • Stoffelen, A., and Anderson D. , 1997: Scatterometer data interpretation: Measurement space and inversion. J. Atmos. Oceanic Technol., 14, 12981313.

    • Search Google Scholar
    • Export Citation
  • Stoffelen, A., and van Beukering P. , 1997: Improved backscatter processing and impact of tandem ERS winds on HIRLAM. HIRLAM Project Rep. 31, IMET, Dublin, Ireland, 86 pp.

  • Unden, P., 2002: HIRLAM-5 scientific documentation. HIRLAM-5 Project, Norrköpping, Sweden, 144 pp. [Available online at http://hirlam.org/index.php?option=com_docman&task=doc_details&gid=308&Itemid=139.]

  • Verspeek, J. A., Stoffelen A. , Portabella M. , Bonekamp H. , Anderson C. , and Figa J. , 2010: Validation and calibration of ASCAT using CMOD5.n. IEEE Trans. Geosci. Remote Sens., 48, 386395, doi:10.1109/TGRS.2009.2027896.

    • Search Google Scholar
    • Export Citation
  • Vogelzang, J., Stoffelen A. , Verhoef A. , de Vries J. , and Bonekamp H. , 2009: Validation of two-dimensional variational ambiguity removal on SeaWinds scatterometer data. J. Atmos. Oceanic Technol., 26, 12291245.

    • Search Google Scholar
    • Export Citation
  • Vogelzang, J., Stoffelen A. , Verhoef A. , and Figa-Saldaña J. , 2011: On the quality of high-resolution scatterometer winds. J. Geophys. Res.,116, C10033, doi:10.1029/2010JC006640.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 146 77 1
PDF Downloads 96 54 0

Impact of ASCAT Scatterometer Wind Observations on the High-Resolution Limited-Area Model (HIRLAM) within an Operational Context

View More View Less
  • 1 KNMI, De Bilt, Netherlands
Restricted access

Abstract

Denial experiments, also denoted observing system experiments (OSEs), are used to determine the impact of an observing system on the forecast quality of a numerical weather prediction (NWP) model. When the impact is neutral or positive, new observations from this observing system may be admitted to an operational forecasting system based on that NWP model. A drawback of the method applied in most denial experiments is that it neglects the operational time constraint on the delivery of observations. In a 10-week twin experiment with the operational High-Resolution Limited-Area Model (HIRLAM) at KNMI, the impact of additional ocean surface wind observations from the Advanced Scatterometer (ASCAT) on the forecast quality of the model has been verified under operational conditions. In the experiment, the operational model was used as reference, parallel to an augmented system in which the ASCAT winds were assimilated actively. Objective verification of the forecast with independent wind observations from moored buoys and ASCAT winds revealed a slight improvement in forecast skill as measured by a decrease in observation-minus-forecast standard deviation in the wind components for the short range (up to 24 h). A subjective analysis in a case study showed a realistic deepening of a low pressure system over the North Atlantic near the coast of Ireland through the assimilation of scatterometer data that were verified with radiosonde observations over Ireland. Based on these results, the decision was made to include ASCAT in operations at the next upgrade of the forecasting system.

Corresponding author address: Gert-Jan Marseille, KNMI, Wilhelminalaan 10, 3732 GK De Bilt, Netherlands. E-mail: gert-jan.marseille@knmi.nl

Abstract

Denial experiments, also denoted observing system experiments (OSEs), are used to determine the impact of an observing system on the forecast quality of a numerical weather prediction (NWP) model. When the impact is neutral or positive, new observations from this observing system may be admitted to an operational forecasting system based on that NWP model. A drawback of the method applied in most denial experiments is that it neglects the operational time constraint on the delivery of observations. In a 10-week twin experiment with the operational High-Resolution Limited-Area Model (HIRLAM) at KNMI, the impact of additional ocean surface wind observations from the Advanced Scatterometer (ASCAT) on the forecast quality of the model has been verified under operational conditions. In the experiment, the operational model was used as reference, parallel to an augmented system in which the ASCAT winds were assimilated actively. Objective verification of the forecast with independent wind observations from moored buoys and ASCAT winds revealed a slight improvement in forecast skill as measured by a decrease in observation-minus-forecast standard deviation in the wind components for the short range (up to 24 h). A subjective analysis in a case study showed a realistic deepening of a low pressure system over the North Atlantic near the coast of Ireland through the assimilation of scatterometer data that were verified with radiosonde observations over Ireland. Based on these results, the decision was made to include ASCAT in operations at the next upgrade of the forecasting system.

Corresponding author address: Gert-Jan Marseille, KNMI, Wilhelminalaan 10, 3732 GK De Bilt, Netherlands. E-mail: gert-jan.marseille@knmi.nl
Save