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.