Scatterometer Wind Services in Europe
Stoffelen, Ad1; Verhoef, Anton1; Verspeek, Jeroen1; Vogelzang, Jur1; Driesenaar, Tilly1; Bentamy, Abderrahim2

High accuracy wind vector data are being produced at the Royal Dutch Meteorological Institute (KNMI) from a large set of scatterometers, the ERS Active Microwave Instrument, ASCAT-A, ASCAT-B on MetOp, SeaWinds on QuikScat and ADEOS-II, NSCAT on-board ADEOS-I, the Indian OceanSat-2 (OSCAT) and the Chinese HY2A. A multi-agency CEOS Virtual Constellation (VC) on Ocean Vector Winds has been established to coordinate the spatial and temporal sampling, but also develop standards in intercalibration and validation of the diverse instruments. Although Geophysical Model Functions (GMF) for all these instruments are empirical, KNMI succeeds in using standard processing with unique C-band and Ku-band GMFs after calibration of the different backscatter distributions from the different scatterometer systems. Also, calibration, validation, quality monitoring, and processing streams are set up using standard tools, which are being shared through the International Ocean Vector Winds Science Team and further developed and coordinated. Such standard processing is not only useful for near-real time processing, but also allows the generation of long-range climate data sets with uniform characteristics.

The (KNMI) is involved in manifold wind scatterometer services for the meteorological, ocean and climate communities at large (see also

(1) Within the EUMETSAT Ocean and Sea Ice (OSI) Satellite Application Facility (SAF) KNMI provides near-real time (NRT) wind data products for all ASCATs,

(2) Regional ASCAT-A and -B winds are within 30 minutes through EUMETSAT EARS,

(3) In addition to mid-morning and evening ASCAT wind processing, the OSI SAF also processes the noon and midnight (00:00 LTAN) data of OSCAT,

(4) The ocean winds user community moreover looks forward to the complementary winds of the HY2A satellite at 6:00 LTAN, since its addition would provide all-day-round coverage. KNMI off-line produced high-quality winds from HY2A,

(5) Within the European Union MyOcean(2) project, KNMI manages higher level wind products in collaboration with IFREMER. At KNMI scatterometer winds are provided on a geographical grid, e.g., Level 3 (L3) ASCAT and OSCAT winds; IFREMER combines NWP winds with several L3 satellite wind products and provides Level 4 winds and stresses,

(6) the freely available OSCAT Wind Data Processor (OWDP) and ASCAT Wind Data Processors (AWDP) have been developed from resp. the SeaWinds scatterometer Data Processor (SDP) and the ERS data processor within the Numerical Weather Prediction (NWP) SAF,

(7) KNMI further provides monitoring, training and documentation on these services.

All processors provides unique quality winds as verified against buoys. The main idea is that when, e.g., OSCAT would provide similar ocean backscatter PDF and backscatter quality to SeaWinds, then an identical wind retrieval procedure would deliver OSCAT winds of similar quality to SeaWinds, i.e., both would be intercalibrated. Indeed good OSCAT winds emerge from OWDP. Other advantages of standard processors exist in standardization and that Quality Assurance, Quality Control and monitoring, but also file formats, closely resemble those for SeaWinds and ASCAT, for user's convenience. The intercalibrated processors and diverse satellite data will be reprocessed within ESA projects, the OSI SAF (L2) and the MyOcean (L3,L4) projects.

The new scatterometer constellation allows the depiction of diurnal and sub-diurnal processes and initialisation of mesoscale wind structures. Moreover, the ASCAT-A and ASCAT-B configuration facilitates a new view on short-lived dynamical processes, e.g., related to deep convection or polar low development. A brief overview of these services and their scientific background, application and usefulness for the ocean winds community will be presented at the meeting.

First ASCAT-B winds (blue) preceeding a pass of ASCAT-A winds (red). ASCAT-A and ASCAT-B winds closely correspond, except near deep tropical convection (wind downbursts).