N: 40 S: -40 E: 180 W: -180
Description
This dataset contains the Version 1.0 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 2 month latency. The reported sample locations are determined by the specular points corresponding to the Delay Doppler Maps (DDMs). The Version 1.0 CDR represents the first climate-quality release and is a collection of reanalysis products derived from the SDR v2.1 Level 1 data. Calibration accuracy and long term stability are improved relative to the SDR v2.1 using a new trackwise correction algorithm which constrains the average value of the L1 data using MERRA-2 reanalysis wind speeds. 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 v2.1 SDR data processing algorithms. These products also exhibit improved calibration accuracy and stability over SDR v2.1. 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 variations in the transmit power level of the GPS signals measured by the CYGNSS bistatic radar receivers. The SDR v2.1 L1 algorithm assumes a constant GPS transmit power and variations in it can be misinterpreted as variations in the L1 data and in subsequent L2 science data products derived from them. The GPS constellation consists of several different satellite models (a.k.a. block types) and the level of transmit power variation differs between them. The more recent Block IIF models (which account for ~37% of the GPS constellation) have significantly larger variations than the older models and, for this reason, they have been screened out and not used to produce SDR v2.1 L2 or L3 science data products. Trackwise correction eliminates the need for this screening so CDR L2 and L3 data products now include Block IIF samples. It should be noted that the trackwise correction algorithm cannot be successfully applied to all SDR v2.1 L1 data so there is also some loss of samples that were present in SDR v2.1. Overall, there is a significant increase in sampling and improvement in spatial coverage with the CDR products.
Product Summary
Citation
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Documents
USER'S GUIDE
ALGORITHM THEORETICAL BASIS DOCUMENT (ATBD)
DATA CITATION GUIDELINES
PUBLICATIONS
Dataset Resources
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 2017-03-18 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 |
| num_yslf_wind_speed_samples | The number of L2 young sea limited fetch wind speed samples used to calculate yslf_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 2017-03-18 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 |
| yslf_wind_speed | Minimum variance estimate of the young sea limited fetch 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 |
| yslf_wind_speed_uncertainty | Standard deviation of the error in the mean of all L2 samples of the young sea limited fetch wind speed within the bin. | m s-1 | float | -9999 | N/A | 1 |