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QuikSCAT Level 1C Averaged Sigma-0 and Winds from Non-spinning Antenna Version 2.0

Metadata Updated: December 7, 2023

This dataset is Version 2 of the geo-located and averaged Level 1B Sigma-0 measurements and wind retrievals from the SeaWinds on QuikSCAT platform, initiated in the months following the failure of the rotating antenna motor on 22 November 2009, using the various incidence angles at which QuikSCAT was pointed during the time period from November 2009 until present. Incidence angles were varied in order to cross-calibrate the Oceansat-2 and RapidScat scatterometers and to extend the known Ku-band geophysical model function. The averaging of the L1B input data combined with the wind vector processing results are both contained in this product referred to hereafter as Level 1C (L1C). The fixed and repointed beam processing is relative to either the one corresponding to the vertically polarized "outer" beam or the other corresponding to the horizontally polarized "inner" beam. The Sigma-0 values from the fixed operating beam for each frame are averaged to a single value representing approximately 50 samples. The data points are land flagged, collocated with ECMWF surface winds, and have climatological nadir attenuations provided for the location and time of the data (not applied to the sigma0). The following enhancements have been applied in the Version 2 re-processing: 1) the GMF has been updated (QNS2016a) to make use of ECMWF nowcast 1x1 degree resolution wind direction information for the entire historical data record; 2) the new QNS2016a GMF leverages a calibration adjustment from Remote Sensing Systems (RSS) resulting in a consistently lower Normalized Radar Cross Section (NRCS or Sigma-0) measurements that establishes a Sigma-0 bias of -0.25 dB (-5.9% linear scale) compared to the L1C Version 1 data; 3) the new QNS2016a GMF also applies an azimuthal modulation that is decreased by several tenths of a dB (for Sigma-0) in variation with wind speed; this results in a more consistent wind speed retrieval comparison between "non-spinning" and "spinning" modes of the QuikSCAT instrument; 4) spacecraft attitude was re-estimated using slice data over multiple orbits as a replacement for lost echo-tracking capability during the "non-spinning" mode of the instrument; this new attitude estimation follows an unpublished manual technique that leverages the echo power of individual slice observations; since only a small subset of slice observations are analyzed, rapid variations in attitude are not captured; 5) continues data production beyond October 2016 through the end of mission on 30 August 2018. Retrieved wind directions are only slightly different from ECMWF values and should not be considered an independent measurement of wind direction. Retrieved wind speeds do not depend significantly on ECMWF speeds as evidenced by the fact that they agree closely with WindSAT polarimetric radiometer speeds whenever WindSAT and ECMWF disagree. The Sigma0 values have also been corrected for scan loss (due to the fact that the antenna does not scan) and for X-factor changes due to repointing.

Access & Use Information

Public: This dataset is intended for public access and use. License: No license information was provided. If this work was prepared by an officer or employee of the United States government as part of that person's official duties it is considered a U.S. Government Work.

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Metadata Created Date April 27, 2023
Metadata Updated Date December 7, 2023

Metadata Source

Harvested from NASA Data.json

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Additional Metadata

Resource Type Dataset
Metadata Created Date April 27, 2023
Metadata Updated Date December 7, 2023
Identifier C2617177020-POCLOUD
Data First Published 2017-08-30
Language en-US
Data Last Modified 2017-08-30
Category QUIKSCAT, geospatial
Public Access Level public
Bureau Code 026:00
Metadata Context
Metadata Catalog ID
Schema Version
Catalog Describedby
Citation JPL. 2019-02-13. QuikSCAT Level 1C Averaged Sigma-0 and Winds from Non-spinning Antenna. Version 2.0. QuikSCAT Level 1C Averaged Sigma-0 and Winds from Non-spinning Antenna Version 2.0. PO.DAAC. Archived by National Aeronautics and Space Administration, U.S. Government, PO.DAAC. JPL, PO.DAAC, 2019-02-13, QuikSCAT Level 1C Averaged Sigma-0 and Winds from Non-spinning Antenna Version 2.0, .
Creator JPL
Graphic Preview Description Thumbnail
Graphic Preview File
Harvest Object Id daabdd61-a22b-4a3c-8f13-44a90518a83c
Harvest Source Id 58f92550-7a01-4f00-b1b2-8dc953bd598f
Harvest Source Title NASA Data.json
Homepage URL
Metadata Type geospatial
Old Spatial -180.0 -89.875 180.0 89.875
Program Code 026:001
Release Place PO.DAAC
Series Name QuikSCAT Level 1C Averaged Sigma-0 and Winds from Non-spinning Antenna
Source Datajson Identifier True
Source Hash fe3a6f54b9d2ccb74963c4c2d6656b3b15a6d1e7d44abd08d975a2985321f7e8
Source Schema Version 1.1
Temporal 2010-07-16T00:00:00Z/2018-08-30T23:59:59.999Z

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