The PO.DAAC is pleased to announce the public release of the (Cyclone Global Navigation Satellite System) CYGNSS Science Data Record (SDR) Version 3.1 (V3.1) Level 1 (L1) DDM calibration, Level 2 (L2) wind speed retrieval , and Level 3 (L3) gridded wind speed datasets. Improvements have been made relative to the previous v3.0 L1 and L2 algorithms, as described below. The data are provided in netCDF-4 format and extend from 1 August 2018 to present with an approximate 6 day latency.
L1 – The CYGNSS science antenna gain patterns have been adjusted to improve the accuracy of the ocean surface normalized bistatic radar cross section (NBRCS) calibration. They are adjusted so that the annual average observed NBRCS matches the model-predicted average as derived from Wavewatch-3 estimates of the surface roughness with the appropriate spectral tail extension added to the roughness spectrum. The adjustment is made independently at each position in the science antenna pattern. A correction for coarse quantization effects by the on-board digital processor has also been added. This reduces the effects of radio frequency interference, which appeared as calibration biases in the v3.0 L1 NBRCS and retrieval biases in the v3.0 L2 wind speed that were persistent at certain locations.
L2 – The L2 Geophysical Model Functions (GMFs) that map L1 observables to ocean surface wind speed were rederived to be consistent with the v3.1 L1 calibration. The method used for deriving the GMFs is the same as for v3.0. A new correction has been added to both the Fully Developed Seas (FDS) and Young Seas Limited Fetch (YSLF) wind speed products that is a function of the Significant Wave Height (SWH) of the ocean surface. The correction is based on an observed correlation between the wind speed error and SWH. The SWH value used by the correction algorithm is the ERA5 reanalysis product, coincident in space and time with a CYGNSS measurement. The FDS and YSLF retrieval algorithms are otherwise the same as v3.0.
L3 – The L3 algorithm is unchanged. The v3.1 L3 gridded products inherit the v3.1 L2 data as input at the same temporal and spatial resolution as the Level 2 data, sampled on consistent 0.2 by 0.2 degree latitude by longitude grid cells.
More information on the CYGNSS mission can be found here: https://podaac.jpl.nasa.gov/cygnss
DOIs:
Citations:
- CYGNSS. 2021. CYGNSS Level 1 Science Data Record Version 3.1. Ver. 3.1. PO.DAAC, CA, USA. Dataset accessed [YYYY-MM-DD] at https://doi.org/10.5067/CYGNS-L1X31
- CYGNSS. 2021. CYGNSS Level 2 Science Data Record Version 3.1. Ver. 3.1. PO.DAAC, CA, USA. Dataset accessed [YYYY-MM-DD] at https://doi.org/10.5067/CYGNS-L2X31
- CYGNSS. 2021. CYGNSS Level 3 Science Data Record Version 3.1. Ver. 3.1. PO.DAAC, CA, USA. Dataset accessed [YYYY-MM-DD] at https://doi.org/10.5067/CYGNS-L3X31
References:
Gleason, S., M. M. Al-Khaldi, C. Ruf, D. S. McKague, T. Wang, A. Russel (2021). Characterizing and Mitigating Digital Sampling Effects on the CYGNSS Level 1 Calibration. IEEE Trans. Geosci. Remote Sens., doi: 10.1109/TGRS.2021.3120026.
Pascual, D., M. P. Clarizia, C. S. Ruf (2021). Improved CYGNSS Wind Speed Retrieval Using Significant Wave Height Correction. Remote Sensing, doi: 10.3390/rs13214313.