Abstract:
This report contains conductivity, temperature, depth (CTD), and auxiliary physiochemical sensor data (cumulatively referred to as “CTD data” herein) and provides additional context for the posted dataset, including information about the collection, analysis, and organization of the data. Characteristics of this dataset include the following: • This dataset consists of vertical cast water column CTD data collected as part of Response and NRDA efforts from May through September 9 of 2010. • This dataset includes CTD data from several cruises; data were collected cooperatively by the Trustees and BP or independently by the Trustees. • All data included in this posting were processed and validated cooperatively by Trustee and BP representatives. The focus of this data posting is vertical cast water column CTD data collected in the Gulf of Mexico from May through September 2010. This posting includes 13 studies encompassing 39 cruises and 829 CTD casts. These studies can be classified into three general categories: • NRDA Cooperative—Studies conducted as part of the NRDA which were agreed to and executed cooperatively by the National Oceanic and Atmospheric Administration (NOAA), U.S. Department of Interior (DOI) and/or other Trustees, and BP. • Trustee Independent—Studies conducted by NOAA, DOI, and/or other Trustees independently to develop data to support and inform the NRDA. • Response (non-NRDA)—Studies conducted by BP and/or government representatives under the direction of the Unified Area Command and in association with activities performed in response to the DWH accident (the Response). The physical and chemical CTD data parameters provided in this data posting are as follows: • Conductivity • Temperature • Depth • Pressure • Salinity • Dissolved oxygen • Fluorescence • Turbidity • Chlorophyll • pH • Sound Velocity All water column CTD datasets include conductivity, temperature, depth, pressure, and salinity; the auxiliary sensor packages varied by work plan and/or vessel. To facilitate use of the CTD data, BP is providing processed data in the form of multiple data files and data types, specific to each individual cast. The various files associated with casts conducted during each cruise are compiled into a single zipped file folder, whenever practical. When not practical, overly large folders have been broken out into multiple zipped folders which are indicated by including an a, b, c, etc. at the end of each file name. A data posting station summary file has been provided to serve as an index for all studies and cruises and contains the coordinates for each CTD cast. Additionally, a PDF file containing CTD cast location maps for each cruise is provided to illustrate their spatial extent. The folder/file structure used in the report primarily identifies six file types: • Conversion data files (.cnv) • ASCII files (.asc) • Header files (.hdr) • Bottle summary files (.btl) • Rosette files (.ros) • Network common data form (netCDF) files (.nc) Due to the variety and unique combinations of sensors, the data fields and associated units may vary between cruises. The metadata presented here lists common field names/parameters stored in these files, a description of those parameters, and units.
Data Parameters and Units:
timeJ Julian Days = Time recorded at each sensor reading (Julian days (J)); scan: Scan Count = A record of measurement by the CTD. Each record is assigned a scan number. (No units); latitude: Latitude [decimal deg] = Latitude of the vessel position for each scan. (Decimal degrees); longitude: Longitude [decimal deg] = Longitude of the vessel position for each scan (Decimal degrees); dz/dtM: Descent Rate [m/s], WS = Calculated rate of decent of the CTD package. (Meters per second (mis)); depSF:Depth (salt water, ft) lat = = Calculated depth of the measurement (scan) in feet at a given latitude, entered manually. (Feet (ft)); depSM Depth [salt water, m) lat = = Calculated depth of the measurement (scan) in feet at a given latitude, entered manually. (Meters (m)); t090C: Temperature (ITS- 90,deg C) = Measured water temperature using the ITS-90 calibration standard. (Degrees Celcius (°C)); t190C: Temperature, 2 (ITS-90, deg C) = Measured water temperature (measured by a second temperature sensor) using the ITS-90 calibration standard. (Degrees Celcius (°C)); T2-T190C: Temperature Difference, 2 - 1 (ITS-90, deg C) = The difference between the two temperature measurements,if there is a second sensor. (Degrees Celcius (°C)); potemp090C: Potential Temperature (ITS-90, deg C) = Potential temperature is calculated by assuming the water parcel is raised to the surface (pressure=O}, instead of at the pressure of the actual measurement. (Degrees Celcius (°C)); prSM: Pressure, Strain Gauge [db] = Pressure measured using a strain gauge sensor. (Decibar (db)); prDM: Pressure, Digiquartz [db] = Pressure measured using a digiquarts sensor. (Decibar (db)); cOS m: Conductivity [S/m] = Measured conductivity. (Siemens per meter (S/m)); c1Slm: Conductivity, 2 [S/m] = Conductivity measured by a second conductivity sensor. (Siemens per meter (S/m)); C2-C1S m: Conductivity Difference, 2 - 1 [S/m] = The difference between the two conductivity measurements, if there is a second sensor. (Siemens per meter (S/m)); salOO Salinity, Practical [PSU] = Salinity calculated from conductivity and temperature. (Practical Salinity Units (PSU)); sigma-eOO: Density [sigma-theta, (Kg/m3) = Density anomaly calculated from potential temperature, conductivity, and a pressure of zero. (Kilograms per meter cubed (kg/m3)); sigma-tOO: Density [sigma-!,(Kg/m3) = Density anomaly calculated from temperature, conductivity, and a pressure of zero. (Kilograms per meter cubed (kg/m3)); sbeoxOV: Oxygen raw, SBE 43 (V) = Measured dissolved oxygen. (Volts (V)); oxsatMg/L: Oxygen Saturation, Weiss (mg/I) = Theoretical maximum amount of dissolved oxygen a parcel of seawater can hold. Calculated from temperatu re and salinity. (Milligrams per liter (mg/I)); oxsatML/L: Oxygen Saturation, Weiss (ml/l) = Theoretical maximum amount of dissolved oxygen a parcel of seawater can hold. Calculated from temperature and salinity. (Milliliters per liter (ml/I)); sbeoxOMg/L: Oxygen, SBE 43 (mg/I). WS = Measured dissolved oxygen. (Milligrams per liter (mg/I)); sbeoxOML/L: Oxygen, SBE 43 (ml/I),WS = Measured dissolved oxygen. (Milliliters per liter (ml/I)); wetCDOM: Fluorescence, WET Labs CDOM (mg/m3) = Measured colored dissolved organic matter (CDOM) fluorescence by a WET Labs sensor. (Milligrams per meter cubed (mg/m3)); wetStar: Fluorescence, WET Labs WETstar (mg/m3) = Measured fluorescence by a WET Labs Wet Star sensor. (Milligrams per meter cubed (mg/m3)); flCUVA: Fluorescence, Chelsea UV Aquatracka (ug/l) = Measured fluorescence by a Chelsea UV Aquatracka sensor. (Micrograms per liter (ug/l)); flSCC Fluorescence, Turner Cor Chi [ug/L) = Measured fluorescence by a Turner Designs sensor. (Micrograms per liter (ug/l)); flScufa Fluorescence, Turner SCUFA (RFU) = Measured fluorescence by a Turner Designs SCUFA senor (Relative fluorescence units (RFU)); flScufa1 Fluorescence, Turner SCUFA,2 (RFU) = Measured fluorescence by a second Turner Designs SCUFA sensor. (Relative fluorescence units (RFU)); flScufadiff Fluorescence, Turner SCUFA Ditf, 2 -1 = The difference between the measurements for the two Turner Designs SCUFA fluorescence sensors. (Relative fluorescence units (RFU)); flSP Fluorescence, Seapoint = Measured fluorescence by a Seapoint sensor. (Parts per billion (ppb)); obsscufa: OBS, Turner SCUFA [NTU) = Optical backscatter measured by a Turner Designs SCUFA sensor. (Nephelometric turbidity units (NTU)); obs3+ OBS, D & A 3plus (NTU) = Optical backscatter measured by a D&A 3plus sensor. (Nephelometric turbidity units (NTU)); obs3+1:OBS, D & A 3plus, 2 (NTU) = Optical backscatter measured by a second D&A 3plus sensor. (Nephelometric turbidity units (NTU)); seaTurbMtr Turbidity, Seapoint (FTU) = Turbidity measured by a Seapoint sensor. (Formazine turbidity units (FTU)); turbflTCO: Turbidity, Turner Cyclops (NTU) = Turbidity measured by a Turner Designs Cyclops sensor (Nephelometric turbidity units (NTU)); turbWETntuO: Turbidity, WET Labs ECO (NTU) = Turbidity measured by a WET Labs ECO sensor (Nephelometr ic turbidity units (NTU)); spar SPAR/Surface lrradiance = Surface irradiance measured by a surface photosynthetically active radiation (SPAR) sensor. (Micro Einsteins per meter squared per second (uE/m2/s)); par: PAR/irradiance, Biospherical/Licor = irradiance measured by a photosynthetically active radiation (PAR) sensor.from Biospherical/Licor (Micro Einsteins per meter squared per second (uE/m2/s)); bat: Beam Attenuation, Chelsea/Seatech (1/m) = Beam attenuation measured by a Chelsea Seatech sensor. (Inverse meters (1/m)); CStarAtO: Beam Attenuation,WET Labs C-Star (1/m) = Beam attenuation measured by a WET Labs CStar sensor. (Inverse meters (1/m)); CStarTrO: Beam Transmission,WET Labs C-Star [%] = Beam transmission measured by a WET Labs CStar sensor. (Percentage (%)); xmiss: Beam Transmission, Chelsea/Seatech [%] = Beam transmission measured by a Chelsea Seatech sensor. (Percentage (%)); ph: pH = Measured acidity of the seawater. (No units); svCM Sound Velocity (Chen-Millero, mis) = The velocity of sound calculated from temperature, salinity, and pressure. (Meters per second (mis)); avgsvCM: Average Sound Velocity [Chen- Millero,m/s). minP = The average sound velocity calculated from temperature, salinity, and pressure. (Meters per second (mis)); sva: Specific Volume Anomaly (10-8 • m3/Kg) = Specific volume anomaly is the difference between the specific volume of each scan and the specific volume at a salinity of 35, a temperature of 0, and the pressure of the scan. The specific volume of each scan is the inverse of the density of the scan. (10 to the minus 8 meters cubed per kilogram (10-8 m3/kg)); altM Altimeter [m] = Measurement of the distance between the CTD package and the sea floor. (Meters (m)); croilflTCO: Crude Oil, Turner Cyclops (ppb QS) = Crude oil measured by a Turner Designs Cyclops sensor (Parts per billion (ppb)); vO: Voltage 0 = Free channel. (No units); v1: Voltage 1 = Free channel. (No units); v2: Voltage 2 = Free channel. (No units); v3: Voltage 3 = Free channel. (No units); flag:flag = An error flag used by the SBE processing software to identify bad scans. In the final processed data files the flags are typically zero. (No units); Cast ID = Randomly generated sequential number assigned to each cast; Cast Name = Unique name assigned to each cast using the vessel name abbreviation, cruise number,date of the cast (YYYYMMDD} , and the sequential number of the cast during the cruise; Cast Direction = A letter indicating downcast (d) or upcast (u); Variable Name = The selected parameter (e.g. temperature,conductivity, etc.); Number Review Flag Assigned = The total number of scans a Review flag with that Reason was assigned to that cast,in that direction, for that variable; Percentage Review Flag Assigned = The percentage of scans a Review flag with that Reason was assigned to that cast,in that direction, for that variable; Data Quality Review Flag = The data quality Review flag; Data Quality Reason Flag = The Reason the data quality review flag was assigned; Data Publication Date = Date associated with the current data posting (MM/DD/YYYY); Data Publication Reference = A general description of data provided in the data posting and a version control number; CTD Cruise File Name = Name of the zip file containing the CTD data for this cruise in this dataset; Study Reference Number = Study reference number (SRN) assigned by BP to provide a link between the data provided in the data file and the associated work plans and study descriptions ; Harmonized Study Name = Abbreviated name of the study in the database. This name is part of the primary key of this table and is used within other documents provided by BP; NRDA/Response = The program the study was part of (NRDA or Response); Vessel = The name of the vessel (ship) from which the CTD data were collected; Cruise ID = The unique identifier for the cruise; Date Sampled = Date which the CTD cast was conducted (MM/DD/YYYY); Station ID = The unique identifier of the cast (station); Latitude = The latitude coordinate in decimal degrees of the Station ID where the CTD cast was conducted; Longitude = The longitude coordinate in decimal degrees of the Station ID where the CTD cast was conducted; Cast Depth (m) = The depth (in meters) of the CTD cast at the individual Station ID listed (not always to the sea floor); QA Status = The quality assurance (QA) status of the CTD data being released. Based on NRDA Cooperative CTD process or another QA process; Data Types = Types of measured and calculated data contained in the CTD data files. (Conductivity, Temperature, Depth, Pressure, Dissolved Oxygen, Fluorescence, Salinity, Turbidity , pH, Density, Sound Velocity, Altimetry, Transmissometry, Irradiance)
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