N: 40 S: -40 E: 180 W: -180
Description
This dataset contains the Version 1.1 CYGNSS Level 3 Climate Data Record which provides the average wind speed and mean square slope (MSS) on a 0.2x0.2 degree latitude by longitude equirectangular grid obtained from the Delay Doppler Mapping Instrument aboard the CYGNSS satellite constellation. The Level 2 Delay Doppler Map (DDM) data are used in the direct processing of the average wind speed and MSS data that are binned on the Level 3 grid. A subset of DDM data used in the direct processing of the average wind speed and MSS is co-located inside of the Level 2 data files. A single netCDF-4 data file is produced for each day of operation with an approximate 1 to 2 month latency. The reported sample locations are determined by the specular points corresponding to the Delay Doppler Maps (DDMs). The Version 1.1 CDR is a collection of reanalysis products derived from the SDR v3.0 Level 1 data (https://doi.org/10.5067/CYGNS-L1X30 ). Calibration accuracy and long term stability are improved relative to SDR v3.0 (https://doi.org/10.5067/CYGNS-L3X30 ) using the same trackwise correction algorithm as was used by CDR v1.0 (https://doi.org/10.5067/CYGNS-L3C10 ), which was derived from SDR v2.1 Level 1 data (https://doi.org/10.5067/CYGNS-L1X21 ). Details of the algorithm are provided in the Trackwise Corrected CDR Algorithm Theoretical Basis Document. CDR Level 2 and 3 products (ocean surface wind speed, mean square slope, and latent and sensible heat flux) are generated from the CDR L1 data using the v3.0 SDR data processing algorithms. These products also exhibit improved calibration accuracy and stability over SDR v3.0. Trackwise correction is applied to the two primary CYGNSS L1 science data products, the normalized bistatic radar cross section (NBRCS) and the leading edge slope of the Doppler-integrated delay waveform (LES). The correction compensates for small errors in the Level 1 calibration, due e.g. to uncertainties in the GPS transmitting antenna gain patterns and the CYGNSS receiving antenna gain patterns. CDR v1.1 does 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 should use the SDR v3.0 YSLF wind speed product. A YSLF wind speed product is omitted because the trackwise correction algorithm, which constrains the average value of the L1 data using MERRA-2 reanalysis wind speeds, is inherently biased toward fully developed sea state conditions. The constraint improves wind speed retrieval performance in fully developed seas but produces underestimates in YSLF conditions. It should also be noted that the trackwise correction algorithm cannot be successfully applied to all SDR v3.0 L1 data so there is also some loss of samples that were present in SDR v3.0.
Product Summary
Citation
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Documents
USER'S GUIDE
ALGORITHM THEORETICAL BASIS DOCUMENT (ATBD)
DATA CITATION GUIDELINES
PUBLICATIONS
Variables
Variables are a set of physical properties whose values determine the characteristics or behavior of something. For example, temperature and pressure are variables of the atmosphere. Parameters and variables can be used interchangeably. Variable level attributes provide individual information for each variable.
The Name in this table is the variable name. Fill value indicates missing or undefined data points in a variable. Valid range is the range of values the variable can store. Scale factor is used to increase or decrease the size of an object and can be used to correct for distortion. For questions on a specific variable, please use the Earthdata Forum.
| Name Sort descending | Description | Units | Data Type | Fill Value | Valid Range | Scale Factor |
|---|---|---|---|---|---|---|
| epoch_time | Timestamp coordinate is at the center of the 1 hr bin, at 1 hour resolution referenced by the historical Epoch reference date/time. The Epoch reference date/time corresponds to the first observation time window in the CYGNSS historical data record. Total number of timestamps in a file corresponds to one UTC day. This value is rounded to the nearest hour since leap seconds may have occured making the number of hours since the start of the mission not exact. | hours since 2018-08-01 00:30:00.000000000 | int | N/A | N/A | 1 |
| lat | Latitude coordinate at the center of the 0.2 degree bin, degrees_north, at 0.2 degree resolution. Range is -39.9 .. 39.9. | degrees_north | float | N/A | N/A | 1 |
| lon | Longitude coordinate at the center of the 0.2 degree bin, degrees_east, at 0.2 degree resolution. Range is 0.1 .. 359.9. | degrees_east | float | N/A | N/A | 1 |
| mean_square_slope | Mean MSS in the bin over the spatial and temporal intervals specified by the bin's boundaries. | 1 | float | -9999 | N/A | 1 |
| mean_square_slope_uncertainty | Standard deviation of the error in the mean of all L2 samples of the MSS within the bin. | 1 | float | -9999 | N/A | 1 |
| merra2_wind_speed | Mean MERRA-2 wind speed in the bin over the spatial and temporal intervals specified by the bin's boundaries. See https://disc.gsfc.nasa.gov/datasets/M2I1NXASM_5.12.4/summary?keywords=%22MERRA-2%22 | m s-1 | float | -9999 | N/A | 1 |
| num_merra2_wind_speed_samples | The number of L2 MERRA-2 wind speed samples used to calculate merra2_wind_speed. | 1 | int | -99 | N/A | 1 |
| num_mss_samples | The number of L2 MSS samples used to calculate mean_square_slope. | 1 | int | -99 | N/A | 1 |
| num_wind_speed_samples | The number of L2 wind speed samples used to calculate wind_speed. | 1 | int | -99 | N/A | 1 |
| time | Timestamp coordinate at the center of the 1 hr bin, at 1 hour resolution. Range is one UTC day. | hours since 2018-08-10 00:30:00.000000000 | byte | N/A | N/A | 1 |
| wind_speed | Minimum variance estimate of the mean wind speed in the bin over the spatial and temporal intervals specified by the bin's boundaries. This is done using an inverse-variance weighted average of all L2 samples of the wind speed that were made within the bin. | m s-1 | float | -9999 | N/A | 1 |
| wind_speed_uncertainty | Standard deviation of the error in the mean of all L2 samples of the wind speed within the bin. | m s-1 | float | -9999 | N/A | 1 |