CTD System

Posted in CTD Data

A Sea-Bird Electronics 911plus V2 CTD collects vertical profile data at every CalCOFI station. In addition to being a dual TCO (temperature, conductivity, and oxygen) system, the CTD also interfaces with a transmissometer, fluorometer, PAR/SPAR meters, altimeter, nitrate, and pH sensor. Connected to a shipboard data-acquisition computer through an electronically-conductive winch wire, sensor data are collected and displayed real-time using Seasave V7. The CTD is normally lowered to terminal depth of 515 m, bottom-depth permitting, but is routinely deployed within meters from the seafloor at nearshore SCCOOS and basin stations. To ensure high resolution sampling in areas with significant hydrological and biological gradients a speed of ~30 m/min is used for the first 100 m then ~60 m/min to depth without stopping. During retrieval, the CTD is paused for at least 20 seconds at target bottle depths to adequately flush each 10 liter sample bottle prior to closure. Seawater samples are analyzed onboard (e.g., salinity, oxygen, nutrients, chl) and are used to correct measured CTD values.

SBE and CalCOFI Formats

Posted in CTD Data

SBE formats

There are two types of SBE files that CalCOFI provides to users. There are six types of cast data created each cast by SeaBird's Seasave program during each CalCOFI station. ASC-HDR files are created by SBE Data Processing software module ASCII Out. This routine outputs the header portion (.hdr) and the data portion (.asc) of a processed converted data file (.cnv).

CTD Data

Posted in CTD Data

CalCOFI CTD Data

CalCOFI CTD Data are available in three formats: CTD cast files, CTD preliminary files and CTD final files.  YY-YYMMSC refers to year, month, & shipcode associated with each CalCOFI cruise e.g. 20-1411NH = 2014 Nov New Horizon (1411NH).  Browse our CTD Archive.

Latest Raw & preliminary CTD data:

1708 • 1 - 16 Aug 2017 • R/V Sally Rde; 73 stations; 20-1708 CTD cast files; 20-1708 CTD preliminary asc-hdr files. Cast.zip file contains raw, unprocessed CTD cast files.  Prelim.zip file contains Seasoft-processed CTD data, preliminary bottle-corrected CTD data, & preliminary bottle data.  Preliminary data are subject to change as CalCOFI data-quality, error-checking protocols are applied.  

Latest Final bottle-corrected CTD data: 

1701 • 05 - 29 Jan 2017 • NOAA Reuben Laskar; 75 Stations; 20-1701 CTD cast files; 20-1701 CTD final asc-hdr files. Cast.zip file contains raw, unprocessed CTD cast files.  Final.zip file contains Seasoft-processed CTD data, final bottle-corrected CTD data, & final bottle data.  Final data suitable for publication.

CalCOFI Final CTD Database (Sept2015):

2005 - 2012 CalCOFI CTD data are final Seabird-processed, bottle-corrected 1m CTD data. The CTD database is constructed or updated from each cruises' CTD cast files after bottle-corrections have been applied. Two tables - upcast & downcast - are in the database along with bottle data used to calibrate the sensors. Note that typically three columns are available for each sensor: Seasave-only processed sensor data - no bottle correction applied; cruise-corrected ("CruiseCorr") = bottle-corrected sensor data using coefficients derived from regressing all bottle data to sensor data; station-corrected ("StaCorr") = bottle-corrected sensor data using coefficients derived from regressing only the current station's bottle data to sensor data. Station-corrected sensor data is considered the best when 20 or more bottle samples are available to calibrate the sensor measurements. Station-correcting helps eliminate the station-to-station variability in certain sensor, particularly the ISUS when a new lamp is installed and experiencing "burn-in" drift.

CTD Data Description

 
Cast Files
Files as created by SeaBird's Seasave program during each CalCOFI station. These data are unaltered and may contain errors (e.g., incorrect header information) or be incomplete due to system failure during collection. Two or more files may be available for a single station in the latter case. Each cruise will have a single cast data file. This file is a compressed .zip containing .zip files for each cast of the cruise, yymm_CTDCast.zip and yymm_llllssss_###.zip respectively. Each station .zip should contain the following: .bl, .con, .hdr, .hex, .mrk, and .prn files.
Preliminary data
Those which have been processed without final bottle data. The bottle data used to create bottle versus CTD regression calculations and corrections, and appended bottle data has only gone through a cursory and thus incomplete quality control process. Sensor data taken during the cast may also contain anomolous features (e.g., drop outs and spikes) that have not been complety processed. Preliminary CTD data is offered as a single compressed .zip file as yymm_CTDPrelim.zip that may contain files and folder structure for ASC-HDR, CSV-Plot, and metadata formats as they becomne available.
Final data
Those which have passed through the CalCOFI quality control process and have become publicly available. They differ from preliminary data in that the bottle data has been ammended leaving bottle versus CTD regression calculations and corrections, and appended bottle data in their final corrected form. Final CTD data is offered as a single compressed .zip file (i.e., yymm_CTDFinal.zip) containing files and folder structure for ASC-HDR, CSV-Plot, and metadata formats.