HY-2B and HY-2C winds and services from the OSI SAF

  • HY-2B and HY-2C winds are now being produced for evaluation by a limited group of European users. They will become available on EUMETCast on the 4th November 2021.

  • HY-2C wind field on 21 August 2021 12:40 UTC east of the USA coast showing hurricane Henri

    The Haiyang 2B (HY-2B) satellite was launched on 25 October 2018 and Haiyang 2C (HY-2C) was launched on 21 September 2020.

    Both satellites are operated by the Chinese National Satellite Ocean Application Service (NSOAS) and carry a Ku-band pencil-beam scatterometer similar in concept as the US QuikSCAT and the Indian OSCAT scatterometers:

    • HY-2B is in a sun-synchronous orbit with a local time of descending node at 6:00.
    • HY-2C is in a drifting orbit with 66° inclination and provides wind measurements between ~73° N and ~73° S which includes almost all global oceans.
  • Data products and availability

    Within the context of the EUMETSAT Ocean and Sea Ice Satellite Application Facility, KNMI produces level 2 wind data from various scatterometer instruments in near-real time. HY-2B and HY-2C winds are now being produced for evaluation by a limited group of European users. Level 3 gridded winds are produced as well (currently only for HY-2B) and these are available to every interested user.

    Wind products are created with 25 km and 50 km swath grid spacing. The processing algorithms for the wind processing are to a great extent based on the algorithms as developed in the OSI SAF and Numerical Weather Prediction (NWP) SAF for earlier Ku-band scatterometers, and have been improved in close cooperation with colleagues from China.

  • Daily coverage of ascending HY-2B orbits
    Daily coverage of ascending HY-2B orbits

    The HY-2B/C data are acquired via non-polar ground stations in China which means that timeliness is not optimal since downloads are available in principle only twice per day.

    Daily coverage of ascending HY-2C orbits
    Daily coverage of ascending HY-2C orbits

    However, EUMETSAT currently facilitates 5-7 daily orbit dumps to a Finnish ground station to improve timeliness.

  • HY-2B winds are available as near-real time L3 products to the EU Copernicus Marine Environment Monitoring Service (CMEMS, https://marine.copernicus.eu/about-us/about-producers/wind-tac/).

  • Timeliness of HY-2B winds: approximately 50% of the data are available after 180 minutes (3 h), approximately 95% of the data are available after 600 minutes (10 h)

    The local time of Equator crossing of the polar orbit is 6:00 for HY-2B. Due to this the mission helps to close the gaps in the temporal coverage of the current operational missions of ASCAT on the Metop satellites (9:30). Due to its drifting orbit HY-2C provides a good monitoring of the diurnal cycle and regular collocations with all other scatterometers in operation which helps in instrument intercalibrations. Both products are visualised in the Multi-Platform product viewer on the OSI SAF wind web-site (https://scatterometer.knmi.nl/tile_prod/). This viewer allows the user to zoom in on a region of interest and conveniently display the wind fields from different satellites over time. Hence, the development of meteorologically interesting features can be easily followed by comparing different products.

     

  • Validation results

    The products provide wind quality well within the OSI SAF product requirements (better than 2 m/s in wind component standard deviation with a bias of less than 0.5 m/s in wind speed on a monthly basis). The results show that HY-2B and HY-2C winds have a slightly better quality than ScatSat-1 winds which may be due to recent improvements in the OSI SAF wind processing and to differences in the instrument characteristics between HSCAT and OSCAT.

    More information is available from the  Scientific Validation Report for the HY-2 winds (https://scatterometer.knmi.nl/publications/pdf/osisaf_cdop3_ss3_svr_hy-2_winds.pdf)

  • Buoy comparison results of HY-2B, HY-2C, and ScatSat-1 wind products
    Buoy comparison results of HY-2B, HY-2C, and ScatSat-1 wind products

    The HY-2B and HY-2C winds have been validated using in situ winds from moored buoys.

    ECMWF comparison results of HY-2B, HY-2C, and ScatSat-1 wind products
    ECMWF comparison results of HY-2B, HY-2C, and ScatSat-1 wind products

    The HY-2B and HY-2C winds have also been validated using ECMWF forecast winds

  • Outlook

    The winds have been fully reviewed and an operational product status is expected on the 4th November 2021. HY-2B and HY-2C winds are now being produced for evaluation by a limited group of European users. A wider distribution is strived for, depending on agreements between EUMETSAT and NSOAS. The OSI SAF winds will become available on EUMETCast soon.

    The new HY-2D satellite was launched on 19 May 2021 and it is in a similar non-sun-synchronous orbit as HY-2C. HY-2D will help to increase the temporal coverage of scatterometer winds. Some first test data have been assessed and the results look very similar to those of HY-2B and HY-2C.

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