Thursday, August 4, 2022

PO.DAAC is pleased to announce the release of the CYGNSS Level 2 Ocean Surface Heat Flux Science Data Record (SDR) Version 2.0, which provides time-tagged and geolocated ocean surface heat flux parameters with 25x25 kilometer footprint resolution from the Delay Doppler Mapping Instrument (DDMI) aboard the CYGNSS satellite constellation. The reported sample locations are determined by the specular points corresponding to the Delay Doppler Maps (DDMs). Version 2.0 represents the second release of this product, which now uses CYGNSS Level 2 (L2) Science Data Record (SDR) Version 3.1 surface wind speeds and ECMWF Reanalysis, Version 5 (ERA5). Version 1.0 used CYGNSS L2 SDR Version 2.1 surface wind speeds and NASA Modern-Era Retrospective Analysis for Research and Applications Version 2 (MERRA-2). The Coupled Ocean-Atmosphere Response Experiment (COARE) algorithm is what is used in this dataset to estimate the latent and sensible heat fluxes and their respective transfer coefficients. While COARE's initial intentions were for low to moderate wind speeds, the version used for this product, COARE 3.5, has been verified with direct in situ flux measurements for wind speeds up to 25 m/s. As CYGNSS does not provide air/sea temperature, humidity, surface pressure or density measurements, the producer of this dataset obtains these values from ERA5.

The Cyclone Global Navigation Satellite System (CYGNSS), launched on 15 December 2016, is a NASA Earth System Science Pathfinder Mission that was developed with the purpose to collect the first frequent space-based measurements of surface wind speeds in the inner core of tropical cyclones. Made up of a constellation of eight micro-satellites, the CYGNSS observatories provide nearly gap-free Earth coverage with a mean (i.e., average) revisit time of seven hours and a median revisit time of three hours. As a result of the CYGNSS constellation coverage, these data are made available from 1 August 2018 to present with an approximate 1 week latency in the netCDF-4 formatted data files, where each file contains data within a 24-hour UTC period from a combination of up to 8 unique CYGNSS spacecraft. More information on CYGNSS can be found on the CYGNSS mission page.

Access to the data as well as a complete listing of documentation resources, read software, and access information is available here: CYGNSS_L2_SURFACE_FLUX_V2.0.

More detailed dataset information can be found in the dataset User Guide, with specific variable descriptions available in an Excel-formatted Data Dictionary.

DOI: 10.5067/CYGNS-L2H20

Citation: CYGNSS. 2022. CYGNSS Level 2 Ocean Surface Heat Flux Science Data Record Version 1.0. Ver. 1.0. PO.DAAC, CA, USA. Dataset accessed [YYYY-MM-DD] at

Reference: Crespo, J. A., Posselt, D. J., & Asharaf, S. (2019). CYGNSS Surface Heat Flux Product Development. Remote Sens. 2019, 11, 2294. DOI:

Access: Users are encouraged to use the PO.DAAC Data Downloader/Subscriber ( to download the data.

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