{"id":784,"date":"2020-03-24T12:37:31","date_gmt":"2020-03-24T16:37:31","guid":{"rendered":"https:\/\/www2.whoi.edu\/site\/beaufortgyre\/?page_id=784"},"modified":"2025-05-01T11:58:01","modified_gmt":"2025-05-01T15:58:01","slug":"mooring-data","status":"publish","type":"page","link":"https:\/\/www2.whoi.edu\/site\/beaufortgyre\/data\/mooring-data\/","title":{"rendered":"Mooring data"},"content":{"rendered":"\n

\n\t\tMooring Data Description\n\t<\/h2>\n\t

1) BPR (bottom pressure recorders)<\/h2>\n

On the BG moorings, bottom pressure measurements are being made using either Sea-Bird Electronics SBE-16plus temperature and salinity recorders or SBE-53 BPR bottom pressure recorders, both with precision Paroscientific Digiquartz (6000 psia) pressure sensors. The recovered data processing procedure is fundamentally the same for either instrument.<\/p>\n

Accuracy of the pressure sensor is 0.01% full-scale (~0.4 m for 6000 psia sensor), and the long term drift is on the order of 1 ppm per year. The resolution of the pressure measurement depends on the sensitivity of the sensor and the resolution of the counter. Integrating the pressure measurements increases the resolution of the pressure measurement, although this may be limited somewhat by sensor drift, recorder time base drift, and background noise. For the SBE-16plus recorders, a measurement integration of 70 seconds should resolve better than 1 mm. The SBE-53 BPR provides higher quality data by continuously powering the pressure sensor and ovenized reference oscillator to reduce startup transients, hence a measurement integration of 1 minute should resolve better than 0.2 mm. Battery life considerations dictate the configured sampling rate for each instrument so that the frequency of SBE16plus measurements is either 25 or 30 minutes between readings, and the frequency of the SBE 53 BPR measurements is 15 minutes.<\/p>\n

After recovering the BPR, Sea-Bird SeaTerm software is used to download the data from the SBE16plus recorders in single binary hexadecimal (HEX) files, while SeaTermW software is used for the SBE53 BPRs. The hex files are converted to ASCII CNV files using the Sea-Bird Data Processing program for the SBE16plus recorders and using Seasoft for waves for the SBE53 BPRs. During this step, the instrument specific calibration adjustments are applied to the raw data. The CNV files include header information with all of the instrument specific information including the calibration coefficients used in the conversion, followed by the specific output data in columns. These data were plotted using the Sea-Bird software to visually check for obvious errors. Subsequently, the CNV files are imported into MATLAB, where deployment specific script routines operate on the data from every instrument in a single year.<\/p>\n

The MATLAB routines truncate the time series for the period when the BPR is deployed on the ocean bottom, and output the data in ASCII files. The filename format is\u00a0bgXXYY_bpr_Z.dat<\/strong>, where\u00a0XXYY<\/em><\/strong>\u00a0indicates the observation years and\u00a0Z<\/strong><\/em>\u00a0is the mooring identifier. The first two lines of the file are header information (preceded by a % character), the data follow in 3 columns, and the file terminates with %endofdat. The first line of the header includes the observation years, the mooring identifier and location, and the second line indicates the data variables and units\u00a0[%date time(UTC) pressure(dbar) temperature(C) salinity(PSU)]<\/strong>. Dates and times are given in UTC, and temperature is determined according to the ITS-90 scale.<\/p>\n

2) MMP (McLane Moored Profilers)<\/h2>\n

The results of the\u00a0BGFE 2003-04 MMP EMCTD and ACM Data Processing [PDF]<\/a>\u00a0are digitally archived in three formats that are being made publicly available here along with documentation thoroughly describing the processing procedure. The data are identical regardless of the format.<\/p>\n

The first format stores all of the processed data from all profiles from a single MMP into single Matlab-format files ending in .mat, where a, b, and c identify the mooring. Each file contains the following variables:<\/p>\nDPDT:<\/strong>\u00a0array of profiling speeds cm\/s
\nS:<\/strong>\u00a0array of salinity pss
\nSIGTH:<\/strong>\u00a0array of sigma-theta kg\/m3
\nT:<\/strong>\u00a0array of temperature deg C
\nTHETA:<\/strong>\u00a0array of potential temperature
\nTIME:<\/strong>\u00a0array of time of each measurement (encoded with datenum.m)
\nU:<\/strong>\u00a0array of east velocity cm\/s
\nV:<\/strong>\u00a0array of north velocity cm\/s
\nW:<\/strong>\u00a0array of measured vertical velocity (includes profiling velocity) cm\/s
\ndates:<\/strong>\u00a0vector string with profiler start date
\nday:<\/strong>\u00a0vector of decimal year day (2003)
\nlocation:<\/strong>\u00a0string with location of mooring
\nname:<\/strong>\u00a0string with dataset name
\nnumber:<\/strong>\u00a0vector of profile number
\npgrid:<\/strong>\u00a0vector of pressure grid m\n

The remaining two formats contain the same information in multiple ASCII text files with all the data from each profile in a single file, but differ in the method of storage to accommodate both PC and UNIX computer systems. In either case, the individual ASCII profile data files are named bg0304_mmp_a###.mat, bg0304_mmp_b###.mat, and bg0304_mmp_c###.mat, where a, b, and c identify the mooring and ### is the profile number. For PC systems, all of the files from a single MMP are zipped into single files that end in .zip. For UNIX systems, all of the files from a single MMP are compressed and tarred into single files ending in .Z. Each individual data files includes two lines of header information.<\/p>\nThe first line provides general information:
\nproject and mooring name: profile number, start date and time, location\nThe second line describes the columns of data:
\nhr:min:sec P(Dbar) T(degC) S(PSU) U(cm\/s) V(cm\/s) W(cm\/s) DPDT(cm\/s)\nThe remaining lines comprise the processed data from the profile in the following format:
\n‘%02d:%02d:%02.0f %4d %6.3f %6.3f %6.2f %6.2f %6.2f %6.2fn’\n

The lines of data increase sequentially based on the time of the observation, so downgoing profiles start at the shallowest depth and upgoing profiles start at the deepest depth. Grid points with no data (that were filled with NANs) are omitted in the ASCII files.<\/p>\n

3) ULS (upward looking sonars)<\/h2>\n

A complete description of the processing used to derive ice drafts from the ULS data is given in\u00a0BGOS ULS Data Processing Procedure [PDF]<\/a>. The output of the processed ULS data is available in two formats: 1) the complete 2-second ice draft time series, and 2) daily averages draft statistics, temperature, water level, and sound speed. With velocities provided from an outside source, the complete draft time series can be converted to a spatial distribution, and the features in the ice cover can be clearly discerned and described. If high resolution is not required, the daily average ice draft (and ancillary) data provide a synopsis of the results in a convenient abbreviated format.<\/p>\n

The complete draft time series are saved in separate ASCII text files for each mooring and year. The filename includes the deployment year and mooring identifier (for example uls03a_draft.dat). The first two lines of the file includes the experiment year, mooring location and data variable names (with units):<\/p>\n%BG 2003-2004 Mooring A: 75 00.449 N, 149 58.660 W
\n%date time(UTC) draft(m)\n

The remainder of the file includes all 15 million (2-second) draft estimates processed for the full year. Compressed versions of the text file are saved in\u00a0.ZIP<\/strong>\u00a0and\u00a0TAR.Z<\/strong>\u00a0formats.<\/p>\n

Daily average draft, betas, temperature, and water level information for each mooring and year are saved in MATLAB format files (e.g.\u00a0uls03a_daily.mat<\/strong>) with the following variables:<\/p>\ndates:<\/strong>\u00a0date string timeseries
\nname:<\/strong>\u00a0name of the mooring and dataset
\nyday:<\/strong>\u00a0year day timeseries
\nBETA:<\/strong>\u00a0final beta adjustment timeseries used in ice draft calculations
\nBTBETA:<\/strong>\u00a0initial beta timeseries based on bottom temperature
\nID:<\/strong>\u00a0number of ice drafts binned daily every 0.1 m from 0.05 to 29.95 m
\nIDS:<\/strong>\u00a0daily ice draft statistics: number, mean, std, minimum, maximum, median
\nOWBETA:<\/strong>\u00a0beta timeseries determined from open water events
\nT:<\/strong>\u00a0temperature timeseries (\u00b0C)
\nWL:<\/strong>\u00a0water level timeseries (m)\n

3) ADCP (Acoustic Doppler Current Profilers)<\/h2>\n

A 600kHz\u00a0RD Instruments ADCP was installed\u00a0on the\u00a0top flotation\u00a0package on mooring D in 2005\u00a0and two other\u00a0600kHz\u00a0ADCPs (with pressure sensors) were added to moorings A and B in 2010.\u00a0 All have been maintained on an annual basis since.\u00a0 The configuration of the instruments has varied from year to year in order to extend the\u00a0duration of the\u00a0sampling\u00a0with alkaline battery packs, or increase the standard deviation of the ensemble measurements with lithium\u00a0battery packs, but all of the processed data\u00a0consist of\u00a0hourly profiles in 2 m bins.\u00a0 Waves software was included on the ADCP on mooring A\u00a0from 2012-2013 which\u00a0required additional\u00a0processing not described here.<\/p>\n

The\u00a0data are adjusted for speed of sound and depth variations to\u00a0vertically center the depth bins,\u00a0converted to Earth-referenced velocities, and corrected\u00a0for magnetic declination using the\u00a0IGRF model<\/a>.\u00a0 The\u00a0archived products are\u00a0in Matlab format files named according to start year and mooring letter:\u00a0e.g.<\/em>\u00a0BGY05_D_Final1.mat<\/strong>.<\/p>\n

The same structure\u00a0naming of variables is applied in all files.\u00a0 The variable\u00a0adcp<\/strong>\u00a0includes\u00a0six structures:\u00a0settings<\/strong>,\u00a0velocity<\/strong>,\u00a0sensor<\/strong>,\u00a0bottom_track<\/strong>,\u00a0iceV<\/strong>, and\u00a0beam_prop<\/strong>.<\/p>\n

adcp.settings<\/strong>\u00a0includes metadata on the configuration, location, and\u00a0other information of the particular dataset.<\/p>\nadcp.velocity<\/strong>\u00a0includes the Earth referenced velocity profiles in matrix variables\u00a0u<\/strong>,\u00a0v<\/strong>, (in m\/s) and\u00a0time<\/strong>\u00a0([yr mo da hr mn ss]).\u00a0u<\/strong>\u00a0and\u00a0v<\/strong>\u00a0velocity were corrected for magnetic declination. The\u00a0declination correction convention used here was the following:\u00a0TB = MB – D (for declination West), where
\nTB=true bearing
\nMB=magnetic bearing
\nD=declination West
\nFor declination West, D=adcp.sensor.magvar<\/strong>\u00a0is negative, therefore: TB = MB +(-D) = MB – abs(D)\nadcp.sensor<\/strong>\u00a0includes the data from\u00a0the orientation and environmental\u00a0sensors. Speed of sound was calculated using the ADCP temperature sensor and salinity of 35 psu. External ULS data was used\u00a0for\u00a0the depth of the transducer, except in 2005 where\u00a0depth\u00a0was determined using ADCP surface tracking. \u00a0The\u00a0variables in\u00a0this structure are:
\nw<\/strong>\u00a0is ADCP vertical velocity profile array
\ne<\/strong>\u00a0is ADCP error velocity profile array
\ndepth<\/strong>\u00a0is\u00a0true bin depths array
\ndz<\/strong>\u00a0is distance from ADCP transducer\u00a0to center of each bin
\ndays<\/strong>\u00a0is\u00a0ADCP year day (Jan 1 = 1)
\njulian<\/strong>\u00a0is ADCP julian day
\npitch<\/strong>\u00a0is\u00a0ADCP pitch (deg)
\nroll<\/strong>\u00a0is ADCP roll (deg)
\nheading<\/strong>\u00a0is ADCP beam 3 heading (deg)
\ntemp<\/strong>\u00a0is ADCP temperature in deg C\u00a0(from ADCP)
\nsalt<\/strong>\u00a0is ADCP salinity (if available)
\nsoundV<\/strong>\u00a0is ADCP speed of sound at transducer
\ncurrent<\/strong>\u00a0is\u00a0ADCP current
\npressure<\/strong>\u00a0is\u00a0ADCP pressure in dbar (if available)
\ndatenumT<\/strong>\u00a0is ADCP datenum
\ntr_depth<\/strong>\u00a0is\u00a0transducer depth in m (from ULS)
\nmagvar<\/strong>\u00a0is\u00a0magnetic variation (deg)
\nadc<\/strong>\u00a0is\u00a0instrument ADC (1,2,3,4,5,6,7,8)
\ncc<\/strong>\u00a0is compass calibration correction (if available)\n

adcp.bottom_track<\/strong>\u00a0includes the bottom track data collected\u00a0with the\u00a0ADCP Surface Tracking feature to\u00a0estimate the ice velocity using water track pings.\u00a0 The variables in this structure are:\u00a0bt_range<\/strong>\u00a0is vertical range to surface corrected for beam angle to the surface (ice or seawater surface),\u00a0bt_vel<\/strong>\u00a0is bottom track\u00a0velocity (east,\u00a0north, up, error) corrected for magnetic variations\u00a0in the same manner as\u00a0the U and V water velocities,\u00a0bt_corr<\/strong>\u00a0is\u00a0the bottom track correlations, and\u00a0bt_pg<\/strong>\u00a0is the bottom track percent good.<\/p>\n

adcp.iceV<\/strong>\u00a0are\u00a0the Earth-referenced ice\u00a0velocity estimates (VU<\/strong>,\u00a0VV<\/strong>,\u00a0VW<\/strong>, and\u00a0VE<\/strong>=error velocity at max seawater bin)\u00a0in m\/s from the bottom track data.<\/p>\n

adcp.beam_prop<\/strong>\u00a0includes the instrument beam\u00a0property information:\u00a0for echo intensity in\u00a0echo1<\/strong>,\u00a0echo2<\/strong>,\u00a0echo3<\/strong>, and\u00a0echo4<\/strong>; for target strength in\u00a0ts1<\/strong>,\u00a0ts2<\/strong>,\u00a0ts3<\/strong>, and\u00a0ts4<\/strong>; and for percent good in\u00a0pg1<\/strong>,\u00a0pg2<\/strong>,\u00a0pg3<\/strong>, and\u00a0pg4<\/strong>. \u00a0The\u00a04-beam means for\u00a0each\u00a0property are\u00a0in variables\u00a0mn_ea<\/strong>,\u00a0mn_ts<\/strong>, and\u00a0mn_pg<\/strong>, respectively.<\/p>\n\t

Related Files<\/h2>\n

\"\"<\/a><\/p>\n