CYGNSS Level 2 Ocean Surface Heat Flux Science Data Record Version 1.0
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DescriptionThis dataset contains the Version 1.0 CYGNSS Level 2 Ocean Surface Heat Flux Science Data Record, which provides the 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). Only one netCDF-4 data file is produced each day (each file containing data from a combination of up to 8 unique CYGNSS spacecraft) with a latency of approximately 1 to 2 months from the last recorded measurement time. Version 1.0 represents the first release. The Cyclone Global Navigation Satellite System (CYGNSS), launched on 15 December 2016, is a NASA Earth System Science Pathfinder Mission that was launched 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. The 35 degree orbital inclination allows CYGNSS to measure ocean surface winds between approximately 38 degrees North and 38 degrees South latitude using an innovative combination of all-weather performance Global Positioning System (GPS) L-band ocean surface reflectometry to penetrate the clouds and heavy precipitation. 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, the producer of this dataset obtains these values from the NASA Modern-Era Retrospective Analysis for Research and Applications Version 2 (MERRA-2), which uses data assimilation to combine all available in situ and satellite observation data with an initial estimate of the atmospheric state, provided by a global atmospheric model. Since the MERRA-2 data is only updated on monthly intervals, this corresponding heat flux dataset is likewise updated on a monthly interval to reflect the latest data available from MERRA-2, thus accounting for measurement latency, with respect to CYGNSS observables, ranging from 1 to 2 months. The data from this release compares well with in situ buoy data, including: Kuroshio Extension Observatory (KEO), National Data Buoy Center (NDBC), Ocean Sustained Interdisciplinary Time-series Environment observation System (OceanSITES), Prediction and Research Moored Array in the Tropical Atlantic (PIRATA), Research Moored Array for African-Asian-Australian Monsoon Analysis and Prediction (RAMA), and the Tropical Atmosphere Ocean (TAO) array. As this marks only the first data release, future work is expected to provide comparisons and validation with various field campaigns (e.g., PISTON, CAMP2Ex) as well as more buoy data, especially at higher flux estimates.
Dataset TypeOPEN
Processing Level2
CoverageRegion: Global
Northernmost Latitude: 40 degrees
Southernmost Latitude: 40 degrees
Westernmost Longitude: 0 degrees
Easternmost Longitude: 360 degrees
Time Span: 2017-Mar-18 to Present
Granule Time Span: 2017-Mar-18 to 2020-Mar-31
ResolutionSpatial Resolution: 25 km (Along) x 25 km (Across)
Ellipsoid: WGS 84
Latency1440 hours
Swath Width25000 m
Sample Frequency-
Temporal Repeat (Nominal)7.2 Hour
Temporal Repeat (Min)2.8 Hour
Temporal Repeat (Max)24 Hour
Name: Cyclone Global Navigation Satellite System (CYGNSS)
Orbit Period: 94 minutes
Inclination Angle: 35 degrees
Ascending Node: 1970-Jan-01 00:00:00
Name: Delay Doppler Mapping Instrument (DDMI)
Swath Width: 25 km
Description: Delay Doppler Mapping Instrument (DDMI)

ProjectCyclone Global Navigation Satellite System (CYGNSS)
Data ProviderCreator: CYGNSS
Release Place: PO.DAAC
Release Date: 2019-Aug-11
Keyword(s)cygnss, ddm, ddmi, doppler, delay doppler, delay, specular point, wind, winds, wind speed, heat flux, shf, lhf, sensible heat, latent heat, flux, fluxes, heat fluxes, version 1.0, v1.0, version 1, v1
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User's Guide
Level 2 netCDF Surface Flux Data Dictionary
Data Variable Dictionary
CYGNSS Level 2 Heat Flux Dataset Version 1.0 Guide Document
User Guide for the CYGNSS Surface Flux Dataset
Deriving Surface Winds from Tropical Cyclones
Project Materials
CYGNSS Mission Page
CYGNSS Mission Page at University of Michigan
CYGNSS Algorithm Theoretical Basis Document Level 2 Wind Speed Retrieval
Level 2 Wind Speed Retrieval Algorithm Theoretical Basis Document, M. P. Clarizia, V. Zavarotny, C. Ruf, CYGNSS Project Document 148-0138, Rev 5, 17 Aug. 2018.
Journal References
Ruf et al. 2018 (JSTARS)
Ruf, C., R. Balasubramaniam, 'Development of the CYGNSS Geophysical Model Function for Wind Speed', IEEE J. Sel. Topics Appl. Earth Obs. Remote Sens., doi: 10.1109/JSTARS.2018.2833075, 2018.
Ruf et al. 2015 (BAMS)
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.
In-Orbit Performance of the Constellation of CYGNSS Hurricane Satellites
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,
Clarizia et al. 2016 (TGRS)
Clarizia, M. P., and C. S. Ruf, 'Wind Speed Retrieval Algorithm for the Cyclone Global Navigation Satellite System (CYGNSS) Mission', IEEE Trans Geosci. Remote Sens., doi:10.1109/TGRS.2016.2541343, 2016.
CYGNSS Surface Heat Flux Product Development
Crespo, J. A., Posselt, D. J., & Asharaf, S. (2019). CYGNSS Surface Heat Flux Product Development. Remote Sens. 2019, 11, 2294. DOI: 10.3390/rs11192294.
Known Issues
Spacecraft Attitude Tables
Updated Monthly
Citation CYGNSS. 2019. 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

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Journal Reference Crespo, J. A., Posselt, D. J., & Asharaf, S. (2019). CYGNSS Surface Heat Flux Product Development. Remote Sens. 2019, 11, 2294. DOI: 10.3390/rs11192294