The PO.DAAC announces the availability of a new Level-2 Advanced Scatterometer (ASCAT) ocean surface wind vector dataset optimized for coastal ocean regions from the Ocean and Sea Ice Scatterometer Application Facility (OSI SAF), provided at 12.5-km sampling in near-real-time (~2 hour latency) over the global ice-free oceans. The data record begins on 18 August 2010. This experimental dataset differs from the standard 12.5 and 25 km datasets in that it utilizes a spatial box filter (rather than the Hamming filter) to generate a spatial average of the full resolution Sigma-0 measurements from the Level 1B data; all basic Sigma-0 measurements within a 15 km radius of the wind vector cell center are used in the averaging. Since the full resolution L1B Sigma-0 retrievals are used, all non-sea retrievals are discarded prior to the Sigma-0 averaging. Each box average Sigma-0 is then used to
compute the wind vector cell using the same CMOD5.n geophysical model function as in the standard OSI SAF ASCAT wind vector datasets. With this enhanced coastal retrieval, winds can be computed as close to ~15 km from the coast, as compared to the static ~35 km land mask in the standard 12.5 km dataset. Each file is provided in netCDF version 3 format, and contains one full orbit derived from 3-minute orbit granules.
ASCAT is a real aperture radar operating at 5.255 GHz (C-band) and uses vertically polarized antennas in a dual fan beam configuration to provide 70% global coverage each day over the ice free oceans. It is flown on the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT) MetOp-A satellite. The prime objective of ASCAT is to measure vector wind over the ocean���s surface. Scatterometer data has also proved to be very useful in a variety of studies including polar ice and soil moisture. The Royal Netherlands Meteorological Institute (KNMI) produces and monitors the EUMETSAT OSI SAF coastal ASCAT wind dataset (see www.knmi.nl/scatterometer/).
All ASCAT datasets are being distributed as "Preview". This means that although significant validation efforts have been made by KNMI/EUMETSAT, the data continue to undergo scientific evaluation and may receive periodic adjustments and updates accordingly. As part of the data evaluation phase, all ASCAT data users are encouraged to provide feedback.
The OSI SAF still regards this new dataset as experimental. As such, It is important to remind users that there have been and will continue to be a number of incremental changes and improvements as this dataset matures. Users should be mindful about these adjustments if the data are used for climate-related studies. A history of modifications and anomalies has been made available here: http://www.knmi.nl/scatterometer/ascat_osi_co_prod/ascat_app.cgi - modifications.
If you wish to access and read more about this ASCAT dataset, please visit our web portal: http://podaac.jpl.nasa.gov/dataset/ASCAT-L2-Coastal
Should you have any questions or wish to provide feedback on the ASCAT datasets, please contact us at: podaac@podaac.jpl.nasa.gov
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