The PO.DAAC is pleased to announce the release of the "RapidScat Level 2B Ocean Wind Vectors in 12.5km Slice Composites" dataset produced by the RapidScat Science Data Systems Team at the Jet Propulsion Laboratory (JPL). This dataset consists of the version 1 Level 2B (L2B) science-quality ocean surface wind vector retrievals from the RapidScat Ku-band scatterometer, which was designed from the recycled parts of the SeaWinds/QuikSCAT test instrument and launched by a Space-X Falcon-9/Dragon commercial cargo resupply spacecraft on 21 September 2014 which was delivered and mounted to the International Space Station (ISS). The current dataset time series extends from 3 October 2014 until near present day; new data will be provided iteratively for each orbit on a daily delivery cycle with a latency of no earlier than 7 days. The L2B data is provided on a non-uniform grid within the swath at 12.5 km pixel resolution. This resolution is achieved through a slice composite technique in which high-resolution slice measurements from L1B data are composited into a 12.5 km wind vector cell. This version contains an improved geophysical model function (GMF), known as QSCAT12 (Fore et al., 2014; Jaruwatanadilok et al., 2014), consistent with the Remote Sensing Systems Ku2011 GMF (Meissner et al. 2011), and improved rain detection and flagging algorithm; these algorithms are also consistent with the latest reprocessed version 3 QuikSCAT L2B dataset. Each L2B file corresponds to a specific orbital revolution number, which begins at the southernmost point of the ascending orbit. This dataset is provided in netCDF-4 "classic" format and made available via FTP and OPeNDAP.
Unlike QuikSCAT, the International Space Station (ISS) is not in sun-synchronous orbit, and flies at roughly half the altitude with a low inclination angle that restricts data coverage to the tropics and mid-latitude regions; the extent of latitudinal coverage stretches from approximately 60 degrees North to 60 degrees South. Furthermore, there is no consistent local time of day retrieval. More details on the ISS-RapidScat mission are available here: http://winds.jpl.nasa.gov/missions/RapidScat/
The primary dataset information page is provided through our web portal at: http://podaac.jpl.nasa.gov/dataset/RSCAT_LEVEL_2B_OWV_COMP_12_V1.
Data files are provided in a CF-compliant, netCDF version 4 format, accessible at: ftp://podaac.jpl.nasa.gov/allData/rapidscat/L2B12/v1.
Read software is made available in MATLAB, Python, R and IDL and is accessible here: ftp://podaac.jpl.nasa.gov/allData/rapidscat/L2B12/sw.
Should you have any questions or wish to provide feedback on this dataset,
please contact us at: podaac@podaac.jpl.nasa.gov
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Cautionary Notes:
1) This dataset has gone through an expedited public release, and although this dataset has completed cal/val through the RapidScat science team, the PO.DAAC is not prepared to provide full user support until the completion of a user guide, which will provide details on any known issues and caveats with the dataset. The user guide is expected for release by January 2015.
2) The data fields containing the number of measurements of each type for each wind vector cell are currently zero filled. These fields include number_in_aft, number_in_fore, number_out_aft, and number_out_fore. In the next release the correct number of measurements will be included, but for now these fields are zeroed out. Until the next data release, please ignore these data fields.
3) The wind_obj data field that is supposed to contain the likelihood
value of the DIRTH wind vector is also not properly set.
For now this field is filled with -Inf values. This will be corrected in a
future release. Until that time, users interested in the likelihood values
for the solution are encouraged to use the values for the 4 peaks of the
likelihood function contained in the ambiguity_obj data field.
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References:
[1] Fore, A.G., Stiles, B.W., Chau, A.H., Williams, B.A., Dunbar, R. S., Rodriguez E., 2013: Point-wise Wind Retrieval and Ambiguity Removal Improvements for the QuikSCAT Climatological Data Set. IEEE Trans. Geoscience and Remote Sensing, doi:10.1109/TGRS.2012.2235843.
[2] T. Meissner, L. Ricciardulli, and F. Wentz, 2011: All-weather wind vector measurements from intercalibrated active and passive microwave satellite sensors. Geoscience and Remote Sensing Symposium (IGARSS), 2011 IEEE International. July 2011. pp. 1509 –1511.
[3] S. Jaruwatanadilok, B. W. Stiles, and A.G. Fore, 2014: Cross calibration between QuikSCAT and Oceansat-2. IEEE Trans. on Geoscience and Remote Sensing, doi: 10.1109/TGRS.2013.2295539.
Special Note:
These papers describe the wind retrieval and calibration algorithms used
to process the QuikSCAT version 3 wind product. The RapidScat data was
processed using the same techniques.