Oceans and Climate Branch: Data Processing and Analysis Methods
The CTD data are collected using SeaBird Electronics SBE19+ CTD units. The instruments are deployed in two modes. During bongo net tows for plankton samples, the CTD instrument is mounted on the conducting wire above the bongo frame with the sensors pointed up. The data from the in-haul portion of the tow are retained for processing. For vertical casts (i.e., all non-net tow situations), the instrument is mounted on the wire with the sensors pointed down and the data from the down cast are retained for processing. Generally two water samples are collected per day using a water sampling bottle during vertical casts. These samples are analyzed for salinity in the laboratory after the cruise to provide quality control of the CTD salinity data.
All raw Profiler data were processed using the Seabird manufactured software: DATCNV, FILTER, ALIGNCTD, BINAVG, DERIVE, and ASCIIOUT to produce 1 decibar averaged ASCII files. The data were edited, cleaned, and converted to a standard 80-column ASCII formatted cruise file and were archived in ORACLE tables and in the NEFSC anonymous FTP account (ftp://ftp.wh.whoi.edu/pub/hydro).
Station distributions and horizontal contour plots of the surface and bottom temperature and salinity and the anomalies of both parameters are prepared for each survey, if the spatial coverage of sampling was sufficient. In addition, each year all the hydrographic data are combined and sorted into 2-month time bins. Areal average temperatures and salinities are calculated for the six time periods and for the five regions of the northeast continental shelf: western and eastern Gulf of Maine (GOMW, GOME), Georges Bank (GB), and the northern and southern Middle Atlantic Bight (MABN, MABS). Anomalies for the temperature and salinity observations are determined relative to MARMAP reference values, using the method described by Holzwarth and Mountain (1990) as modified by Mountain et al. (2004). The areal averaging also is done using the method described in Holzwarth and Mountain (1990) as modified by Mountain et al. (2004).
Holzwarth, T.J. and D. Mountain. 1990. Surface and bottom temperature distributions from the Northeast Fisheries Center spring and fall bottom trawl survey program, 1963-1987. Woods Hole, MA: Northeast Fisheries Center. Reference Document 90-03. Available from: Information Services Section, NMFS/Northeast Fisheries Science Center, Woods Hole, MA 02543
Mountain, D.G., M.H. Taylor and C. Bascun. 2004. Revised Procedures for Calculating Regional Average Water Properties for Northeast Fisheries Science Center Cruises. Woods Hole, MA: Northeast Fisheries Center. Reference Document 04-08. Available from: Information Service Section, NMFS/Northeast Fisheries Science Center, Woods Hole, MA 02543.