CYGNSS Level 3 Climate Data Record Version 1.0

Processing Level3
Start/Stop Date2017-Mar-18 to 2021-Feb-28
Short NameCYGNSS_L3_CDR_V1.0
DescriptionThis dataset contains the Version 1.0 CYGNSS Level 3 Climate Data Record which provides the average wind speed and mean square slope (MSS) on a 0.2x0.2 degree latitude by longitude equirectangular grid obtained from the Delay Doppler Mapping Instrument aboard the CYGNSS satellite constellation. The Level 2 Delay Doppler Map (DDM) data are used in the direct processing of the average wind speed and MSS data that are binned on the Level 3 grid. A subset of DDM data used in the direct processing of the average wind speed and MSS is co-located inside of the Level 2 data files. A single netCDF-4 data file is produced for each day of operation with an approximate 2 month latency. The reported sample locations are determined by the specular points corresponding to the Delay Doppler Maps (DDMs). The Version 1.0 CDR represents the first climate-quality release and is a collection of reanalysis products derived from the SDR v2.1 Level 1 data. Calibration accuracy and long term stability are improved relative to the SDR v2.1 using a new trackwise correction algorithm which constrains the average value of the L1 data using MERRA-2 reanalysis wind speeds. Details of the algorithm are provided in the Trackwise Corrected CDR Algorithm Theoretical Basis Document. CDR Level 2 and 3 products (ocean surface wind speed, mean square slope, and latent and sensible heat flux) are generated from the CDR L1 data using the v2.1 SDR data processing algorithms. These products also exhibit improved calibration accuracy and stability over SDR v2.1. Trackwise correction is applied to the two primary CYGNSS L1 science data products the normalized bistatic radar cross section (NBRCS) and the leading edge slope of the Doppler-integrated delay waveform (LES). The correction compensates for variations in the transmit power level of the GPS signals measured by the CYGNSS bistatic radar receivers. The SDR v2.1 L1 algorithm assumes a constant GPS transmit power and variations in it can be misinterpreted as variations in the L1 data and in subsequent L2 science data products derived from them. The GPS constellation consists of several different satellite models (a.k.a. block types) and the level of transmit power variation differs between them. The more recent Block IIF models (which account for ~37% of the GPS constellation) have significantly larger variations than the older models and, for this reason, they have been screened out and not used to produce SDR v2.1 L2 or L3 science data products. Trackwise correction eliminates the need for this screening so CDR L2 and L3 data products now include Block IIF samples. It should be noted that the trackwise correction algorithm cannot be successfully applied to all SDR v2.1 L1 data so there is also some loss of samples that were present in SDR v2.1. Overall, there is a significant increase in sampling and improvement in spatial coverage with the CDR products.
Name: Cyclone Global Navigation Satellite System (CYGNSS)
Orbit Period: 94.0 minutes
Inclination Angle: 35.0 degrees
Name: Delay Doppler Mapping Instrument (DDMI)
Swath Width: 25.0 kilometers
Description: Spacecraft angular distance from orbital plane relative to the Equator.

ProjectCyclone Global Navigation Satellite System (CYGNSS)
Data ProviderPublisher: PO.DAAC
Creator: CYGNSS
Release Place: PO.DAAC
Release Date: 2020-May-22

Keyword(s)cygnss, ddm, ddmi, doppler, delay doppler, delay, specular point, wind, winds, wind speed, cdr, climate data record, climate, version 1.0, v1.0
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Spatial Resolution: 0.2 Decimal Degrees x 0.2 Decimal Degrees
Temporal Resolution: Hourly - < Daily
Region: GLOBAL
North Bounding Coordinate: 40 degrees
South Bounding Coordinate: -40 degrees
West Bounding Coordinate: -180 degrees
East Bounding Coordinate: 180 degrees
Time Span: 2017-Mar-18 to 2021-Feb-28
Granule Time Span: 2017-Mar-18 to 2021-Feb-28
Projection Type: Cylindrical Lat-Lon
Projection Detail: Geolocation information included for each pixel
Ellipsoid: WGS 84
NameLong NameUnit
epoch_timeTime Centering of Data Based on Epoch Referencehours since 2017-03-18 00:30:00.000000000
mean_square_slopeMean square slope1
mean_square_slope_uncertaintyMean square slope uncertainty1
merra2_wind_speedMERRA-2 reference wind speedm s-1
num_merra2_wind_speed_samplesNumber of MERRA-2 wind speed samples1
num_mss_samplesNumber of mean square slope samples1
num_wind_speed_samplesNumber of wind speed samples1
num_yslf_wind_speed_samplesNumber of young sea limited fetch wind speed samples1
timeReference time of filehours since 2017-03-18 00:30:00.000000000
wind_speedWind speedm s-1
wind_speed_uncertaintyWind speed uncertaintym s-1
yslf_wind_speedYoung sea limited fetch wind speedm s-1
yslf_wind_speed_uncertaintyYoung sea limited fetch wind speed uncertaintym s-1
    Ruf, C., S. Asharaf, R. Balasubramaniam, S. Gleason, T. Lang, D. McKague, D. Twigg, and D. Waliser. (2019). In-Orbit Performance of the Constellation of CYGNSS Hurricane Satellites. Bull. Amer. Meteor. Soc., 100, 2009 - 2023,
    Ruf, C., R. Atlas, P. Chang, M. Clarizia, J. Garrison, S. Gleason, S. Katzberg, Z. Jelenak, J. Johnson, S. Majumdar, A. O'Brien, D. Posselt, A. Ridley, R. Rose, V. Zavorotny (2015). New Ocean Winds Satellite Mission to Probe Hurricanes and Tropical Convection. Bull. Amer. Meteor. Soc., doi:10.1175/BAMS-D-14-00218.1.
Citation is critically important for dataset documentation and discovery. Please cite the data as follows, and cite the reference papers when it is appropriate.
Citation CYGNSS. 2020. CYGNSS Level 3 Climate Data Record Version 1.0. Ver. 1.0. PO.DAAC, CA, USA. Dataset accessed [YYYY-MM-DD] at

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For more information see Data Citations and Acknowledgments.

Journal Reference Ruf, C. S., Chew, C., Lang, T., Morris, M.G., Nave, K., Ridley, A., Balasubramaniam, R. . 2018. A New Paradigm in Earth Environmental Monitoring with the CYGNSS Small Satellite Constellation, Scientific Reports, 8, 8782.

VersionDatasetVersion DateStatus
3.2CYGNSS Level 3 Climate Data Record Version 3.22024-04-10ACTIVE2024-04-10T19:27:00.000Z
1.2CYGNSS Level 3 Climate Data Record Version 1.22022-05-19ACTIVE2022-05-19T21:12:00.000Z
1.1CYGNSS Level 3 Climate Data Record Version 1.12022-04-11ACTIVE2022-04-11T15:44:00.000Z
1.0CYGNSS Level 3 Climate Data Record Version 1.02021-08-26COMPLETE2021-08-26T14:45:00.000Z