August 27, 2019

The Cyclone Global Navigation Satellite System (CYGNSS), launched on 15 December 2016, is a NASA Earth System Science Pathfinder Mission that is designed 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. Primarily intended to be an ocean surface wind speed measuring mission, CYGNSS has been measuring science-quality ocean surface wind speed data since the beginning of the observation record on 18 March 2017. Following multiple years of data collection, CYGNSS has proven capable of estimating ocean surface measurements beyond wind speed. The PO.DAAC has just released the first version of the Level 2 Ocean Surface Heat Flux Science Data Record. This dataset was provided courtesy of CYGNSS Science Team investigators Derek Posselt (PI, JPL) and Juan Crespo (Co-I, JPL), and delivers time-tagged and geolocated ocean surface heat flux parameters in daily netCDF-4 formatted files with 25x25 kilometer footprint resolution from the Delay Doppler Mapping Instrument (DDMI) aboard the CYGNSS satellite constellation.

Animation of the ocean surface heat flux (top: latent heat; bottom: sensible heat) over the period 18 March 2017 to 30 June 2019 from theĀ CYGNSS Level 2 Ocean Surface Heat Flux Science Data Record Version 1.0

The Coupled Ocean-Atmosphere Response Experiment (COARE) algorithm 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 is updated on a monthly interval, this heat flux dataset is released in monthly increments.

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

More detailed dataset information can be found in the dataset user guide, with specific variable descriptions available in an Excel-formatted data dictionary.