netcdf frf/oceanography/waves/8m-array/8m-array.ncml {
  dimensions:
    station_name_length = 12;
    waveFrequency = 62;
    waveDirectionBins = 72;
    time = 260032;
  variables:
    char station_name(station_name_length=12);
      :cf_role = "timeseries_id";
      :short_name = "station_name";
      :units = ;
      :long_name = "station name";
      :_ChunkSizes = 12U; // uint

    double latitude;
      :_FillValue = -999.0; // double
      :units = "degrees_north";
      :standard_name = "latitude";
      :long_name = "Latitude";
      :short_name = "lat";

    double longitude;
      :_FillValue = -999.0; // double
      :units = "degrees_east";
      :standard_name = "longitude";
      :long_name = "Longitude";
      :short_name = "lon";

    double waveFrequency(waveFrequency=62);
      :_FillValue = -999.0; // double
      :units = "s-1";
      :standard_name = "wave_frequency";
      :long_name = "Spectral Band Center Frequency";
      :short_name = "Frequency";
      :_ChunkSizes = 62U; // uint

    double waveDirectionBins(waveDirectionBins=72);
      :_FillValue = -999.0; // double
      :units = "degree";
      :long_name = "Band Center in Degrees";
      :short_name = "Direction";
      :_ChunkSizes = 72U; // uint

    double time(time=260032);
      :_FillValue = -999.0; // double
      :units = "seconds since 1970-01-01 00:00:00";
      :standard_name = "time";
      :long_name = "UTC Sample Time";
      :calendar = "gregorian";
      :short_name = "time";
      :_ChunkSizes = 1000U; // uint

    double gaugeDepth(time=260032);
      :_FillValue = -999.0; // double
      :units = "m";
      :long_name = "Sensor Depth Using Pressure, relative to mean water level";
      :short_name = "Gauge Depth";
      :_ChunkSizes = 744U; // uint

    double waveHs(time=260032);
      :_FillValue = -999.0; // double
      :units = "m";
      :standard_name = "sea_surface_wave_significant_height";
      :long_name = "Significant Wave Height";
      :description = "Significant wave height computed for spectral frquencies between 0.04 and 0.5 Hz";
      :short_name = "Hs";
      :coordinates = "lat lon";
      :_ChunkSizes = 744U; // uint

    double waveTp(time=260032);
      :_FillValue = -999.0; // double
      :units = "s";
      :standard_name = "sea_surface_wave_period_at_variance_spectral_density_maximum";
      :description = "Period of a parobolic fit to the peak of the energy density spectrum using the peak and two surrounding points.  Computed for wave periods between 2 and 25 seconds";
      :long_name = "Peak Spectral Period Between 2 and 25 Seconds";
      :coordinates = "lat lon";
      :short_name = "Tp";
      :_ChunkSizes = 744U; // uint

    double waveTm(time=260032);
      :_FillValue = -999.0; // double
      :units = "s";
      :standard_name = "sea_surface_wave_mean_period_from_variance_spectral_density_inverse_frequency_moment";
      :description = "Period for the mean of the energy density spectrum";
      :long_name = "Mean Spectral Period";
      :coordinates = "lat lon";
      :short_name = "Tm";
      :_ChunkSizes = 744U; // uint

    double waveTm1(time=260032);
      :_FillValue = -999.0; // double
      :units = "s";
      :standard_name = "sea_surface_wave_mean_period_from variance_spectral_density_first_frequency_moment";
      :description = "Period for the 1st moment mean of the energy density spectrum";
      :long_name = " 1st Moment Mean Spectral Period";
      :coordinates = "lat lon";
      :short_name = "Tm1";
      :_ChunkSizes = 744U; // uint

    double waveTm2(time=260032);
      :_FillValue = -999.0; // double
      :units = "s";
      :standard_name = "sea_surface_wave_mean_period_from variance_spectral_density_second_frequency_moment";
      :description = "Period for the 2nd moment mean of the energy density spectrum";
      :long_name = " 2nd Moment Mean Spectral Period";
      :coordinates = "lat lon";
      :short_name = "Tm2";
      :_ChunkSizes = 744U; // uint

    double wavePeakDirectionPeakFrequency(time=260032);
      :_FillValue = -999.0; // double
      :units = "degree";
      :standard_name = "sea_surface_wave_from_direction";
      :description = "Wave direction is from true north (MET convention)";
      :long_name = "Wave Direction at the Peak of the Frequency-Direction Spectrum";
      :coordinates = "lat lon";
      :short_name = "thetaP";
      :_ChunkSizes = 744U; // uint

    double waveMeanDirection(time=260032);
      :_FillValue = -999.0; // double
      :units = "degree";
      :description = "Wave direction is from true north (MET convention), energy weighted over and computed from a1 & b1";
      :long_name = "Mean Wave Direction of 2D Spectrum";
      :coordinates = "lat lon";
      :short_name = "thetaM";
      :_ChunkSizes = 744U; // uint

    double waveMeanDirectionPeakFrequency(time=260032);
      :_FillValue = -999.0; // double
      :units = "degree";
      :description = "Wave direction is from true north (MET convention), energy weighted at peak frequency";
      :long_name = "Wave Mean Direction at the Peak Frequency";
      :coordinates = "lat lon";
      :short_name = "thetaMp";
      :_ChunkSizes = 744U; // uint

    double wavePrincipleDirection(time=260032);
      :_FillValue = -999.0; // double
      :units = "degree";
      :description = "Wave direction is from true north (MET convention), energy weighted over and computed from a2 & b2";
      :long_name = "Wave Principle Direction of 2D Spectrum";
      :coordinates = "lat lon";
      :short_name = "thetaM2";
      :_ChunkSizes = 744U; // uint

    double waveEnergyDensity(time=260032, waveFrequency=62);
      :_FillValue = -999.0; // double
      :units = "m2 s";
      :standard_name = "sea_surface_wave_variance_spectral_density";
      :long_name = "Energy Density";
      :short_name = "1D Wave Energy";
      :_ChunkSizes = 744U, 62U; // uint

    double directionalWaveEnergyDensity(time=260032, waveFrequency=62, waveDirectionBins=72);
      :_FillValue = -999.0; // double
      :units = "m2 s deg-1";
      :standard_name = "sea_surface_wave_directional_variance_spectral_density";
      :long_name = "2D Wave Energy Density Spectrum";
      :short_name = "Energy Density";
      :_ChunkSizes = 1U, 62U, 72U; // uint

    double qcFlagE(time=260032);
      :_FillValue = -999.0; // double
      :units = ;
      :description = "Realtime QC flags for spectral estimates";
      :long_name = "Quality Control Flag Value for Energy Estimates";
      :flag_meanings = "1=passed, 2=not set, 3=questionable, 4=failed";
      :coordinates = "lat lon";
      :short_name = "QC_flagE";
      :_ChunkSizes = 744U; // uint

    double qcFlagD(time=260032);
      :_FillValue = -999.0; // double
      :units = ;
      :description = "Realtime QC flags for spectral direction estimates";
      :long_name = "Quality Control Flag Value for Directional Spectra Estimates";
      :flag_meanings = "1=passed, 2=not set, 3=questionable, 4=failed";
      :coordinates = "lat lon";
      :short_name = "QC_flagD";
      :_ChunkSizes = 744U; // uint

    double directionalPeakSpread(time=260032);
      :units = "deg";
      :description = "Directional spread at peak frequency with cos(2*theta) circular moments";
      :long_name = "Directional Spectra Spread at Peak Frequency";
      :coordinates = "lat lon";
      :short_name = "spreadP";
      :_FillValue = -999.0; // double
      :_ChunkSizes = 744U; // uint

    double spectralWidthParameter(time=260032);
      :_FillValue = -999.0; // double
      :units = ;
      :description = "Spectral width of 1D spectra, (m0*m4 - m2^2)/(m0*m4)  (Cartwright & Longuet-Higgins, 1956)";
      :long_name = "Spectral Width Parameter";
      :valid_min = "0";
      :valid_max = "1";
      :coordinates = "lat lon";
      :short_name = "spreadP";
      :_ChunkSizes = 744U; // uint

    double waveA1Value(time=260032, waveFrequency=62);
      :_FillValue = -999.0; // double
      :units = ;
      :description = "a1 Fourier coefficient";
      :long_name = "a1 Directional Fourier Coefficient";
      :coordinates = "lat lon";
      :short_name = "a1";
      :_ChunkSizes = 744U, 62U; // uint

    double waveB1Value(time=260032, waveFrequency=62);
      :_FillValue = -999.0; // double
      :units = ;
      :description = "b1 Fourier coefficient";
      :long_name = "b1 Directional Fourier Coefficient";
      :coordinates = "lat lon";
      :short_name = "b1";
      :_ChunkSizes = 744U, 62U; // uint

    double waveA2Value(time=260032, waveFrequency=62);
      :_FillValue = -999.0; // double
      :units = ;
      :description = "a2 Fourier coefficient";
      :long_name = "a2 Directional Fourier Coefficient";
      :coordinates = "lat lon";
      :short_name = "a2";
      :_ChunkSizes = 744U, 62U; // uint

    double waveB2Value(time=260032, waveFrequency=62);
      :_FillValue = -999.0; // double
      :units = ;
      :description = "b2 Fourier coefficient";
      :long_name = "b2 Directional Fourier Coefficient";
      :coordinates = "lat lon";
      :short_name = "b2";
      :_ChunkSizes = 744U, 62U; // uint

  // global attributes:
  :featureType = "timeSeries";
  :title = "FRF 8m Array";
  :summary = "USACE Coastal Observation and Analysis Branch (COAB) collected directional wave data using \n an array of pressure sensors at the Field Research Facility (FRF) in Duck, NC.  The array\n consists of 15 pressure gauges mounted approximately 0.5 m (1.6 ft) off the bottom in the \n vicinity of the 8-m (26-ft) isobath about 900 m (2,953 ft) offshore and to the north of the \n research pier.  Directional information is computed from these gauges using an iterative \n maximum likelihood estimator.\n\n The location satisfies three constraints. First, it is generally outside the surf zone \n so that linear wave theory is applicable in data processing. Second, it is in water shallow \n enough that signals from 3-sec waves, the shortest periods of interest here, are detectable \n above background noise at the bottom-mounted gauges. Third, it is located away from the \n irregular isobaths around the pier and in the nearshore bar system, which helps minimize \n bathymetrically induced inhomogeneities in the wave field.  The location of sensor 111 \n is selected as the nominal coordinate for this 120x255m array. \n\n Spacing between gauges in the array appears irregular in the figure but, for the most part, \n corresponds to the array-design criterion posed by Davis and Regier (1977) that every gauge \n pair has a unique separation. The array geometry encompasses considerable ranges in both \n sizes and numbers of gauge separations. Minimum gauge spacing is 5 m (16.4 ft) in both the \n alongshore and cross-shore directions. Maximum spacing is 255 m (837 ft) in the alongshore \n direction and 120 m (394 ft) in the cross-shore direction. Intermediate gauge spacings are \n in multiples of5 m (16.4 ft). With 15 gauges, there are 105 possible unique spacings. In \n the FRF array, 12 redundant spacings are intentionally left for ancillary examination of \n spacial homogeneity of the wave field, so that 93 unique spacings remain. \n\n Each pressure gauge is a Senso-Metric Model SP973(C), in which a piezoelectric strain gauge \n detects displacement of a pressure-sensitive diaphragm referenced to an evacuated cavity. \n Site calibrations indicate an accuracy of the pressure equivalent of 0.006 m (0.02 ft) of \n water for wave-induced fluctuations about a static water column height of 8 m (26 ft). \n Voltage analogs of pressure signals are hard-wired through 10-Hz, fourth-order, Butterworth \n filters (primarily to eliminate 60-Hz noise) to an analog-to-digital signal converter.\n Discretization of the full-scale signal to 16-bit binary form results in a digitization \n step of the equivalent of 0.0005 m (0.002 ft) of water, exceeding the accuracy of the \n Senso-Metric gauges.\n\n Gauge locations as of 3 Sep 2015, geographic, NC state plane, and FRF shore orthogonal; \n\n Gauge     Lon         Lat      Easting   Northing   FRF-X   FRF-Y   FRF-Z   Depth\n       (deg)       (deg)       (m)       (m)       (m)     (m)     (m)   NAVD88 (m)\n 161  -75.7425750  36.1864616  902558.78  275097.18  914.22  735.43  -7.89  -8.44\n 151  -75.7426690  36.1866799  902549.54  275121.12  913.72  761.09  -7.87  -8.38\n 141  -75.7427900  36.1869757  902537.58  275153.56  913.60  795.65  -7.91  -8.42\n 231  -75.7429120  36.1869993  902526.52  275155.82  903.98  801.57  -7.84  -8.30\n 221  -75.7432144  36.1869112  902499.66  275145.16  875.09  800.75  -7.67  -8.18\n 211  -75.7436517  36.1868046  902460.74  275132.05  834.03  801.76  -7.35  -7.83\n 131  -75.7427930  36.1870246  902537.13  275158.98  915.03  800.90  -7.93  -8.46\n 241  -75.7425835  36.1870770  902555.78  275165.40  934.75  800.55  -7.99  -8.57\n 251  -75.7423697  36.1871292  902574.80  275171.83  954.82  800.08  -8.14  -8.66\n 101  -75.7428053  36.1871703  902535.50  275175.09  919.01  816.61  -7.94  -8.47\n 121  -75.7428605  36.1871544  902530.59  275173.17  913.75  816.48  -7.93  -8.44\n 111  -75.7428906  36.1872375  902527.58  275182.30  914.05  826.08  -7.90  -8.46\n 171  -75.7432552  36.1881327  902491.55  275280.50  913.82  930.69  -8.07  -8.78\n 181  -75.7433438  36.1883522  902482.79  275304.58  913.83  956.31  -8.06  -8.59\n 191  -75.7434516  36.1886457  902472.02  275336.81  914.75  990.29  -7.98  -8.46\n 261  -75.7428410  36.1872500  902531.99  275183.86  918.72  826.04  -7.95  -8.43\n\n Directional spectral analysis uses different subsets of sensors for different frequency\n bands;\n\n Freq (f, Hz)                Gauges Used (if passed QC tests)\n  0.04 <= f < 0.07   [191 181 171 111 121 251 241 131 231 221 211 151 161]\n  0.07 <= f < 0.11   [171 111 101 121 251 241 131 231 221 141 151 161]\n  0.11 <= f < 0.18   [111 101 121 251 241 131 231 141 151 161]\n  0.18 <= f < 0.25   [111 101 121 241 131 231 141 151]\n  0.25 <= f < 0.40   [111 101 121 241 131 231 141]\n\n Wave frequency and direction bins have been interpolated to 0.01 Hz and 5 degrees from \n the original analysis. This was done to maintain compatibility with other FRF directional \nwave data sets. \n***** Wave directions are coming from, degrees clockwise from true north (TN). *****\n\n\n Quality Control flag (qcFlag)-\n QC analysis follows the guidance in the NOAA IOOS manual for Real-Time Quality Control of\n In Situ Surface Wave Data, A Guide to Quality Control and Quality Assurance of In Situ \n Surface Wave Observations, Version 2.0, August 2015. This document was developed in NOAA\'s \n Quality Assurance of Real-Time Oceanographic Data (QARTOD) program.\n\n The qcFlags has the following values:\n   1 = Checked - OK with automated realtime QC\n   2 = Not checked\n   3 = Questionable\n   4 = Failed\n   5 = Human checked/validated\n  -9 = Missing data, used as a place holder\n\n There are separate qcFlags for the 1D and 2D spectra.  The qcflag_spec1D is considered the primary\n flag since if the 1D energy spectrum is bad then the 2D direction spectrum would also be bad.  There\n are occasions when the directional analysis did not obtain a reliable solution and the secondary\n qcFlag_spec2D flag is set.\n\n An additional flag (qcBitflag) contains additional information that may be useful for \n interpreting the questionable or failed qcFlags.  This is stored as a 4-byte integer with bits \n set (to 1) for various QC tests.  \n\n For the 8m-Array each sensor had its own bitFlag in the analysis.  If a sensor failed the QC\n tests it was dropped in the analysis.  The bitFlag with this data set is used to indicate if \n the number of gauges dropped made the directional estimate questionable or failed.\n\n The qcBitflag bit numbers, LSB=1, MSB=16, if set to 1 == problem:\n 1 = suspect wave height\n 2 = failed wave height, out of range \n 3 = suspect wave period\n 4 = failed wave period, out of range \n 5 = suspect wave direction out of range (alongshore)\n 6 = failed wave direction out of range (from shore)\n 7 = suspect low signal to noise ratio (SNR), mean of all used gauges  \n 8 = failed low signal to noise ratio (SNR), mean of all used gauges\n 9 = suspect high energy at low frequencies, mean of all used gauges\n10 = failed, excessive high energy at low frequencies, mean of all used gauges 17 = directional estimate for freq-band 1 questionable 18 = directional estimate for freq-band 2 questionable 19 = directional estimate for freq-band 3 questionable 20 = directional estimate for freq-band 4 questionable 21 = directional estimate for freq-band 5 questionable 22 = directional estimate for freq-band 1 failed (10^-6 energy density filled)   23 = directional estimate for freq-band 2 failed (10^-6 energy density filled)   24 - directional estimate for freq-band 3 failed (10^-6 energy density filled)   25 = directional estimate for freq-band 4 failed (10^-6 energy density filled)   26 = directional estimate for freq-band 5 failed (10^-6 energy density filled)  \n\n Directional estimates would be flagged questionable if only 3 sensors (minimal but possibly OK) \n were used in that frequency band. If less than half the gauges are used for the first 3 (of 5)\n frequency bands and Directional estimates are flagged failed when less than 3 \n gauges were available.\n";
  :history = "1991-01-01:dataset created";
  :source = "In situ observations from FRF-ocean_waves_8m-array_YYYYMM.mat";
  :sourceUrl = "(local files)";
  :standard_name_vocabulary = "CFv25";
  :Metadata_Conventions = "Unidata Dataset Discovery v1.0, CF-1.6";
  :metadata_link = "N/A";
  :Conventions = "CF-1.6";
  :creator_name = "USACE/CHL/COAB";
  :creator_url = "http://www.frf.usace.army.mil";
  :creator_email = "frfwebmaster@usace.army.mil";
  :license = "These data may be redistributed and used without restriction. Data are intended for scholarly use by the research community, with the express agreement that users will properly acknowledge the USACE Field Research Facility and the supporting investigator(s). Use or reproduction of these data for commercial purposes is prohibited without prior written permission.";
  :keywords_vocabulary = "Global Change Master Directory (GCMD) Earth Science Keywords; CF Standard Name Table (v23, 23 March 2013)";
  :keywords = "Oceans > Ocean Waves > Wave Frequency, Oceans > Ocean Waves > Wave Height, Oceans > Ocean Waves > Wave Period, Oceans > Ocean Waves > Wave Spectra, Oceans > Ocean Waves > Wave Direction, DOD > DOD/USARMY/USACE/CHL/FRF > Field Research Facility, Coastal And Hydraulics Laboratory,U. S. Army Corps Of Engineers, U.S. Army, U. S. Department Of Defense, sea_surface_wave_variance_spectral_density, sea_surface_wave_significant_height, sea_surface_wave_from_direction,  sea_surface_wave_directional_variance_spectral_density\"";
  :pprocessing = "realtime";
  :organization = "USACE/CHL/COAB";
  :publisher_url = "http://www.frf.usace.army.mil";
  :infoUrl = "http://frf.usace.army.mil";
  :publisher_email = "frfwebmaster@usace.army.mil";
  :publisher_name = "USACE/CHL/COAB";
  :format_version = "v1.0";
  :institution = "USACE/CHL/COAB";
  :contact = "USACE/CHL/COAB";
  :contact_info = "USACE/CHL/COAB";
  :contact_role = "Owner";
  :contributor_name = "USACE/CHL/COAB";
  :contributor_role = "USACE/CHL/COAB";
  :naming_authority = "FRF";
  :origin = "USACE/CHL/COAB";
  :date_created = "2025-03-31";
  :date_issued = "2025-03-31";
  :acknowledgement = "Data are provided by the Field Research Facility; Coastal Observations and Analysis Branch; US Army Corps of Engineers, Duck, North Carolina.";
  :project = "USACE/COAB observations";
  :id = "FRF-ocean_waves_8m-array";
  :pprocessing_level = "L1";
  :geospatial_vertical_units = "m";
  :geospatial_vertical_resolution = 0.0; // double
  :geospatial_vertical_min = 0.0; // double
  :geospatial_vertical_max = 0.0; // double
  :geospatial_vertical_origin = "sea surface";
  :geospatial_lat_min = 36.1872375; // double
  :geospatial_lat_max = 36.1872375; // double
  :geospatial_lat_units = "degrees_north";
  :geospatial_lon_min = -75.7428906; // double
  :geospatial_lon_max = -75.7428906; // double
  :geospatial_lon_units = "degrees_east";
  :geospatial_vertical_positive = "up";
  :time_coverage_start = "2025-03-01T00:00:00";
  :time_coverage_end = "2025-03-31T23:00:00";
  :deployment_start = "1991-01-01T00:00:00Z";
  :platform = "FRF 8m Pressure Array";
  :instrument = "Bottom Mounted Senso-Metric Pressure Sensors";
  :cross_shore_angle_units = "degrees";
  :cross_shore_angle_description = "cross shore angle at the USACE FRF site in DUCK, NC, clockwise from true north";
  :cross_shore_angle = 71.8; // double
}