Overview

glider_data_units
optical fouling


Sheet 1: glider_data_units

Description of glider Preliminary Ascii datasets available at cormp.org/glider. Asterisked variables are also available in an online queriable database; others are available only in the individual ascii files.







Descriptive Name
Name
(units) [expected range] Description
Year * YYYY
(y) [2005-2015] GMT time 4 digit year (glider Pelagia first mission: June 2005)
Month * MM
(mo) [1-12] GMT time 2 digit month
Day of month * DD
(d) [1-31] GMT time 2 digit day of month
Hour * hh
(hr) [0-23] GMT time 2 digit hour of day
Minute * mm
(min) [0-59] GMT time 2 digit minutes
Second * ss
(s) [0-59] GMT time 2 digit seconds
Latitude * latitude
(degrees) [-90 to 90] decimal latitude
Longitude * longitude
(degrees) [-180 to 180] decimal longitude
Depth * depth_meters
(m) [0-200] depth in meters calculated from best_pressure and latitude using Matlab function sw_dpth.m from CSIRO Seawater library Ver 3.0 downloaded from http://www.mathtools.net/MATLAB/Earth_Sciences_and_Mapping/. Software version info: sw_dpth.m,v 1.1 2003/12/12 04:23:22 pen078 Copyright (C) CSIRO, Phil Morgan 1992. AUTHOR: Phil Morgan 92-04-06 (morgan@ml.csiro.au).
Water Temp * sci_water_temp
(degrees C) [0-40] in-situ temperature in degrees C measured by SeaBird SBE-41cp CTD
Salinity * salinity
(PSU) [0-40] salinity calculated from SeaBird CTD conductivity, temperature and best_pressure using Matlab function sw_salt.m from CSIRO Seawater library Ver 3.0 downloaded from http://www.mathtools.net/MATLAB/Earth_Sciences_and_Mapping/. Software info: sw_salt.m,v 1.1 2003/12/12 04:23:22 pen078 Copyright (C) CSIRO, Phil Morgan 1993. AUTHOR: Phil Morgan 93-04-17, Lindsay Pender (Lindsay.Pender@csiro.au) Calculation of salinity is based on Unesco 1983 polynomial, see: Fofonoff, P. and Millard, R.C. Jr. Unesco 1983. Algorithms for computation of fundamental properties of seawater, 1983. _Unesco Tech. Pap. in Mar. Sci._, No. 44, 53 pp.
Density * sigma_theta
(kg m^-3) [-10 to 40] potential density anomaly, which is potential density -1000 kg m^-3. Potential density is calculated from temperature, salinity and pressure using Matlab function sw_pden.m from CSIRO Seawater library Ver 3.0 downloaded from http://www.mathtools.net/MATLAB/Earth_Sciences_and_Mapping/. Software info: sw_pden.m,v 1.1 2003/12/12 04:23:22 pen078 Exp Copyright (C) CSIRO, Phil Morgan 1992. AUTHOR: Phil Morgan 1992/04/06, Lindsay Pender (Lindsay.Pender@csiro.au)
Current Magnitude * mag
(m s^-1) [0-2] water velocity (current speed) relative to the seafloor, in m s^-1, determined when glider surfaces based on expected and actual GPS location
Current Direction * dir_true
(compass degrees) [0-360] direction toward which the water currents are flowing, in compass degrees from true north, determined when glider surfaces based on expected and actual GPS location. Magnetic declination used for converting magnetic to true was obtained from http://www.ngdc.noaa.gov/seg/geomag/jsp/struts/calcDeclination with a value of mag_decl=-8.8667 , ie 8°52'W for Wilmington, NC, Onslow Bay, NC, June, 2006
Chlorophyll Fluorescence (ug/l) * chl_ugl
(micrograms L^-1) [0-100] Wetlabs Ecopuck chlorophyll a fluorescence in calibrated engineering units based on factory calibration
Chlorophyll (mg/m3) * chlconc
(mg m^-3) [0-100] Wetlabs Ecopuck oceanic chlorophyll a concentration based on linear regression of chl_ugl with intracoastal waterway and Onslow Bay chlorophyll a concentrations as measured on a Turner fluorometer after filtration onto GF/F filters.
Oxygen (% sat.) * O2_sat
(%) [0-150] percent saturation of dissolved oxygen concentration relative to atmospheric equilibrium, as measured by the Aanderaa Optode 3835 oxygen sensor, after applying a minor depth correction (x1.004 at 100 m) to account for the instrument's sensitivity.
Oxygen (mg/l) * DO_mg_l
(mg L^-1) [0-10] oxygen concentration in milligrams per liter of seawater from Aanderaa Optode 3835 sensor, calculated as DO_uM/31.25
Light scatter * beta
(m^-1 sr^-1) [0-0.010] Wetlabs Ecopuck Beta117°(660nm) based on factory calibration
Oceanic particle concentration * SPM
(g m^-3) [0-100] Wetlabs Ecopuck suspended particulate matter (SPM) concentrations based on linear regression of beta with Onslow Bay surface water SPM concentrations measured gravimetrically. Because oceanic particles and intracoastal waterway particles are optically different, concentrations of surface water particles in Onslow Bay may be more accurately represented by this variable (SPM) than by the SPMturbid variable.
Coastal particle concentration * SPMturbid
(g m^-3) [0-100] Wetlabs Ecopuck suspended particulate matter (SPM) concentrations based on linear regression of beta with intracoastal waterway SPM concentrations measured gravimetrically. Because oceanic particles and intracoastal waterway particles are optically different, concentrations of resuspended sediments in Onslow Bay bottom waters may be more accurately represented by this variable (SPMturbid) than by the SPM variable, if intracoastal waterway particles are similar in scattering properties to Onslow Bay resuspended sediments.
Light beam attenuation * true_c_SeaTech
(m^-1) [0-100] beam attenuation coefficient at 660 nm from SAM based on linear regression of SAM output to simultaneous SeaTech transmissometer data; this corrects for the apparent underestimation of beam c by SAM (and is at a different wavelength). As of Sep 2006 separate regressions are done for oceanic and turbid (beam c > 5.36 m^-1) waters, with the oceanic water comparison based on a line through a single comparison point rather than a linear regression; therefore these data should be considered very preliminary.
Diver Visibility * SAM_vis
(m) [0-100] diver visibility from SAM, calculated as a function of beam attenuation coefficient by the algorithm Zaneveld and Pegau (2003), Optics Express 11(23):2997-3009
CDOM Fluorescence (qsde) * cdom_qsde
(ppb) [0-50] Wetlabs Ecopuck CDOM fluorescence in quinine dihydrate equivalent concentration ppb based on factory calibration
CDOM abs coeff (m-1) * ay400
(m^-1) [0-50] Wetlabs Ecopuck CDOM absorption coefficient based on linear regression of cdom_qsde with intracoastal waterway and Onslow Bay dissolved absorption coefficients ay (m^-1).


m_depth
(db) [0-200] decibars of pressure from navigational pressure sensor (Micron 300 PSIA strain gauge transducer) used as approximation for depth in meters. Crush depth for glider is 200m.


m_present_time
(s) [1*10^9-1.2*10^9] GMT time seconds since 1970


m_present_secs_into_mission
(s) [0-2600000] seconds since mission start


best_pressure
(bar) [0-20] best available pressure in bars, from the CTD when it was working and if not then from the navigational pressure transducer data, which were interpolated based on time assuming a constant rate of descent. CTD pressure data were mostly not usable during G002, G003, G004, and G005 missions (Sep 2005 - Sep 2006) due to pressure tube clogging beginning during G002 mission.


pflags

[0-31] pressure flags where bit 2^0 indicates unrealistically high CTD pressure based on a cutoff value of max_realistic_pressure chosen by user for that mission, bit 2^1 indicates CTD pressures were discarded due to deep water (>5 m) disagreement of >20% between CTD and navigational pressure, bit 2^2 indicates CTD pressures were discarded due to shallow water (<=5m) disagreement of > 25% between CTD and navigational pressure, bit 2^3 indicates CTD pressure values were from interpolation based on time, bit 2^4 indicates that the navigational sensor pressure is being used instead of CTD pressure in best_pressure and depth_meters.


sci_water_cond
(Siemens m^-1) [0-5] conductivity, measured by the SeaBird SBE-41cp CTD


sci_water_pressure
(bar) [0-20] pressure, measured by the SeaBird SBE-41cp CTD 500 PSI pressure transducer


m_water_depth
(m) [0-1000] depth of the water, ie distance from water surface to sea floor


m_altitude
(m) [0-1000] distance from the glider to the sea floor


m_final_water_vx
(m s^-1) [0-2] the magnetic eastward component of water velocity (current) relative to the seafloor, in m s^-1, determined when glider surfaces based on expected and actual GPS location


m_final_water_vy
(m s^-1) [0-2] the magnetic northward component of water velocity (current) relative to the seafloor, in m s^-1, determined when glider surfaces based on expected and actual GPS location


u_true
(m s^-1) [0-2] the eastward component of water velocity (current) relative to the seafloor, in m s^-1, determined when glider surfaces based on expected and actual GPS location


v_true
(m s^-1) [0-2] the northward component of water velocity (current) relative to the seafloor, in m s^-1, determined when glider surfaces based on expected and actual GPS location


u_offshore
(m s^-1) [0-2] the offshore component of water velocity (current) relative to the seafloor, in m s^-1, determined when glider surfaces based on expected and actual GPS location. A shoreline angle of 60 degrees for Onslow Bay, NC was used to rotate the x,y coordinate system from E, N to offshore, alongshore.


v_alongshore
(m s^-1) [0-2] the alongshore component of water velocity (current) relative to the seafloor, in m s^-1, determined when glider surfaces based on expected and actual GPS location. Alongshore is positive in the direction of upwelling favorable wind stress, ie approximately northeastward in Onslow Bay, NC. A shoreline angle of 60 degrees for Onslow Bay, NC was used to rotate the x,y coordinate system from E, N to offshore, alongshore.


midpt_depths
(m) [0-200] depths of the bin midpoints used to calculate Brunt-Vaisala frequencies


BVfreq_squared
(s^-2) [0-10^-3] square of the Brunt-Vaisala frequency, calculated from salinity, temperature, pressure and latitude using Matlab function sw_bfrq.m from CSIRO Seawater library Ver 3.0 downloaded from http://www.mathtools.net/MATLAB/Earth_Sciences_and_Mapping/. Software info: sw_bfrq.m,v 1.1 2003/12/12 04:23:22 pen078 Exp Copyright (C) CSIRO, Phil Morgan 1993. AUTHOR: Phil Morgan 93-06-24, Lindsay Pender (Lindsay.Pender@csiro.au)


PPV
(ms)^-1 [-10^-9-10^-9] Planetary Potential Vorticity, calculated from salinity, temperature, pressure and latitude using Matlab function sw_bfrq.m from CSIRO Seawater library Ver 3.0 downloaded from http://www.mathtools.net/MATLAB/Earth_Sciences_and_Mapping/. Software info: sw_bfrq.m,v 1.1 2003/12/12 04:23:22 pen078 Exp Copyright (C) CSIRO, Phil Morgan 1993. AUTHOR: Phil Morgan 93-06-24, Lindsay Pender (Lindsay.Pender@csiro.au)


sci_oxy3835_saturation
(%) [0-150] percent saturation of dissolved oxygen concentration relative to atmospheric equilibrium, as measured by the Aanderaa Optode 3835 oxygen sensor, prior to the minor depth correction needed (x1.004 at 100 m) to account for the instrument's sensitivity.


DO_uM
(micromolar) [0-500] micromolar concentration of oxygen calculated as O2_sat.*sol_O2./2.2414 where sol_O2 is the solubility of oxygen in seawater of a given temperature and salinity at atmospheric pressure. The Matlab function for calculating oxygen solubility came from http://bluemoon.ucsd.edu/rhamme/O2sol.m but was modified slightly to use the coefficients from the third column rather than the first column (an alternative curve fit) of Garcia & Gordon 1992 Table 1, in Garcia, H. & Gordon, L., 1992. Limnology & Oceanography 37(6) p1307. This change was made because the Aanderaa Optode 3835 Operating Manual page 30 uses the Garcia & Gordon 1992 coefficients from the third col.


O2_sat_YSI
(%) [0-150] oxygen saturation measured by Aanderaa Optode 3835 but adjusted using a linear regression relationship between optode data and simultaneous YSI sonde data in a tank. This variable is now obsolete and will probably be eliminated in future glider processing software changes.


DO_mg_l_YSI
(mg L^-1) [0-10] oxygen concentration measured by Aanderaa Optode 3835 but adjusted using a linear regression relationship between optode data and simultaneous YSI sonde data in a tank. This variable is now obsolete and will probably be eliminated in future glider processing software changes.


sci_sam_s1
(counts) [0-~4000] raw signal 1 counts from Wetlabs Scatter Attenuation Meter (SAM)


sci_sam_s2
(counts) [0-~4000] raw signal 2 counts from Wetlabs Scatter Attenuation Meter (SAM)


sci_sam_ref
(counts) [0-~4000] reference counts from Wetlabs Scatter Attenuation Meter (SAM)


SAMc_lin
(m^-1) [0-100] beam attenuation coefficient at 650 nm from SAM using linear calculation method


SAMc_exp
(m^-1) [0-100] beam attenuation coefficient at 650 nm from SAM using exponential calculation method


SAMc_mix
(m^-1) [0-100] beam attenuation coefficient at 650 nm from SAM using mixed (linear & exponential) calculation method


sci_bbfl2s_cdom_sig
(counts) [0-~4000] Wetlabs Ecopuck chromophoric dissolved organic matter (CDOM) fluorescence counts


sci_bbfl2s_cdom_ref
(counts) [0-~4000] Wetlabs Ecopuck CDOM fluorometer reference counts


sci_bbfl2s_chlor_sig
(counts) [0-~4000] Wetlabs Ecopuck chlorophyll a fluorescence counts


sci_bbfl2s_chlor_ref
(counts) [0-~4000] Wetlabs Ecopuck chlorophyll a fluorometer reference counts


sci_bbfl2s_bb_sig
(counts) [0-~4000] Wetlabs Ecopuck scatter counts from volume scattering function Beta117°(660nm) sensor


sci_bbfl2s_bb_ref
(counts) [0-~4000] Wetlabs Ecopuck scatter reference counts

Sheet 2: optical fouling

Preliminary Ascii data are not corrected for optical fouling of sensor.
G005: optical fouling is likely after 6/1/2006.
G004: optical fouling is likely after 4/20/2006.
G003: no optical fouling is observed.
G002: optical fouling is likely after 10/6/2005.