Level 2 Directory README File contents: This directory contains the Version 2.1. science-quality release of the CYGNSS Level 2 (L2) Science Data Record. CYGNSS L2 files have been generated using calibrated and validated level 2 calibration algorithms, which were trained and assessed using engineering and science data collected during Phase E operations. The algorithms and their performance assessment are expected to be improved upon as more data are collected over a wider dynamic range of ocean surface wind speeds and a wider variety of measurement geometries. The primary L2 calibrated measurement parameters are the wind speed and mean square slope (MSS) derived from Delay Doppler Maps (DDMs). The data are provided in netCDF-4 format. Version 2.1 differs from the previous version 2.0 as follows: 1) revised Geophysical Model Functions (GMFs) for both Fully Developed Seas (FDS) and Young Seas with Limited Fetch conditions, to be consistent with the calibration changes made to the v2.1 Level 1 science data products.; 2) Revised covariance matrix between DDMA and LES versions of the FDS wind speed retrieval, used by the minimum variance estimator, resulting from changes made to the v2.1 Level 1 science data products; 3) Revised debiasing algorithm coefficients used by the FDS L2 retrieval algorithm, resulting from changes made to the v2.1 Level 2 science data products; 4) revised quality control (Q/C) flags related to the required level of consistency between DDMA and LES versions of the FDS wind speed retrieval. The errors in the two retrievals are now less correlated so larger discrepancies are allowed. If either retrieval is not available, the sample receives a fatal Q/C flag; 5) new Q/C flag related to the block type of the GPS satellite which provided the transmitted signal. Samples using block II-F signals receive a fatal Q/C flag due to the higher level of uncertainty in their radiated power; 6) revised wind speed uncertainty values as a function of RCG and wind speed, plus a new dependence of the uncertainty on GPS block type to reflect the higher uncertainty in GPS radiated power for block II-F satellites. A citable landing page, which also includes more complete description of this dataset is available here: https://podaac.jpl.nasa.gov/dataset/CYGNSS_L2_V2.1 Sub-directory structure is as follows: ./YYYY/DDD/ ...where YYYY = 4-digit Year and DOY = 3-digit Day of Year. The filenaming convention is as follows: cyg.ddmi.sYYYYMMDD-HHmmSS-eYYYYMMDD-HHmmSS.l2.wind-mss.aAA.dVV.nc cyg: Spacecraft/Mission identifier, where "cyg" refers to the CYGNSS constellation and NASA EV mission title. ddmi: Primary remote sensing subsystem known as the "Delay Doppler Mapping Instrument", or "ddmi". sYYYYMMDD-HHmmSS: Date/time stamp representing the UTC date and time of the first data point in the file in ISO-8601 format. YYYYMMDD represents the 4-digit year, 2-digit month, and 2-digit day of month (respectively). The "s" prefix indicates this is the "starting" point representing the first retrieved measurement in the data file. HHmmSS represents the 2-digit hour, 2-digit minute, and 2-digit second (respectively). eYYYYMMDD-HHmmSS: Date/time stamp representing the UTC date and time of the last data point in the file in ISO-8601 format. YYYYMMDD represents the 4-digit year, 2-digit month, and 2-digit day of month (respectively). The "e" prefix indicates this is the "ending" point representing the last retrieved measurement in the data file. HHmmSS represents the 2-digit hour, 2-digit minute, and 2-digit second (respectively). l2: Data Processing Level 2. wind-mss: Primary Measurement, i.e., "wind-mss", in which the "wind" represents the wind speed and the "mss" represents the Mean Square Slope. aAA: Algorithm version, where AA is the numerical algorithm version identifier. E.g., "a21" = Algorithm Version 2.1. Note: the Algorithm version is numerically de-coupled from the Dataset Version (see below). dVV: Dataset version, where VV is the numerical dataset version identifier. E.g., "d21" = Dataset Version 2.1. Note: the Dataset version is numerically de-coupled from the Algorithm Version (see above). nc: File type: "nc" = netCDF. The CYGNSS Handbook and ATBD will soon be updated to include details regarding the Version 2.1 calibration, algorithm improvements, and updates to the data model. The Handobok, ATBD, and other reference materials may be accessed here: https://podaac.jpl.nasa.gov/CYGNSS Comments/Questions? Please visit our Forum: https://podaac.jpl.nasa.gov/forum/ Last modified on 13 September 2018.