Friday, February 5, 2021

The PO.DAAC is pleased to announce the public release of the CYGNSS Climate Data Record (CDR) Version 1.1 (v1.1) datasets. More information regarding the CYGNSS mission and instrumentation is available from PO.DAAC’s mission webpage. The CDR Version 1.1 collection provides a total of 3 unique datasets, each corresponding to processing Levels 1 (L1), 2 (L2) and 3 (L3), respectively. While there are a large number of variables and measurement parameters in each dataset, the primary measurement in L1 is the Bistatic Radar Cross Section (BRCS) and in both L2 and L3 it is wind speed, expressed in units of meters per second. This version of CDR data is made available from 1 August 2018 to present with an approximate forward production latency of 1 to 2 months in netCDF-4 formatted data files, in which data is contained within a 24-hour UTC period. For L1 data, the files are separated according to the specified spacecraft identifier. For L2 and L3 data, the data files represent a daily aggregation from a combination of up to 8 unique CYGNSS spacecraft. The CDR v1.1 data is intended to provide time series continuity to the CDR v1.0 data that is available prior to August 2018.

This CDR V1.1 update was produced in response to changes and improvements observed within the Science Data Record (SDR) version 3.0 (v3.0) L1 data calibration that took place on 1 August 2018, corresponding to the start of production in the data time series. These datasets comprise a collection of reanalysis products derived from the SDR v3.0 Level 1 data ( Calibration accuracy and long term stability are improved relative to SDR v3.0 using the same trackwise correction algorithm as was used by CDR v1.0 (, which was derived from SDR v2.1 Level 1 data ( Details of the algorithm are provided in the Trackwise Corrected CDR Algorithm Theoretical Basis Document. It is noted that the trackwise correction algorithm cannot be successfully applied to all SDR L1 data, so there is also some loss of samples in the CDR that are otherwise present in the SDR. Calibration accuracy and stability improvements in CDR v1.1 L1 also extend downstream to the L2 and L3 datasets (e.g., ocean surface wind speed and mean square slope).

As a departure from previous versions of CDR and SDR, the CDR v1.1 L2 and L3 datasets do not include a Young Seas with Limited Fetch (YSLF) wind speed product, and investigators requiring wind speed measurements in and near the inner core of tropical cyclones are advised to use the SDR v3.0 L2/L3 datasets. The YSLF wind speed retrieval is omitted in this release as a quality control measure in response to the trackwise correction algorithm, which constrains the average value of the L1 data using MERRA-2 reanalysis wind speeds; this results in a persistent bias toward fully developed sea (FDS) state conditions, thus improving wind speed retrieval for FDS while underestimating in YSLF conditions.


  1. CYGNSS. 2021. CYGNSS Level 1 Climate Data Record Version 1.1. Ver. 1.1. PO.DAAC, CA, USA. Dataset accessed [YYYY-MM-DD] at
  2. CYGNSS. 2021. CYGNSS Level 2 Climate Data Record Version 1.1. Ver. 1.1. PO.DAAC, CA, USA. Dataset accessed [YYYY-MM-DD] at
  3. CYGNSS. 2021. CYGNSS Level 3 Climate Data Record Version 1.1. Ver. 1.1. PO.DAAC, CA, USA. Dataset accessed [YYYY-MM-DD] at

Reference: Ruf, C. S., S. Asharaf, R. Balasubramaniam, S. Gleason, T. Lang, D. McKague, D. Twigg, D. Waliser, 2019. In-Orbit Performance of the Constellation of CYGNSS Hurricane Satellites. Bull. Amer. Meteor. Soc., doi: 10.1175/BAMS-D-18-0337.1.

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Comments/Questions? Please contact or visit the PO.DAAC Ocean Wind Forum.