ASEP Group Data


README. March 8,  2011.


NBP data (1994, 2000, 2007 and 2009) 


UPDATE March 2011 : 2009 CTD/O is now Final Processed Data. The archive file 2009_ctd_ladcp.tar.bz2 contains the "final" 2009 CTD data.  Please replace previous versions, advice your ASEP collaborators, and let us know if anomalies are encountered.



This directory contains the processed CTD/O data collected during 1994, 2000, 2007 and 2009 aboard the R/V NB Palmer. CTD/O data are final and were submitted to NODC. CTD casts were made with a Seabird SEB 911+ system. CTD/O data had been processed with standard SeaBird processing software combining pre-cruise and after cruise calibration for each sensor (pressure, temperature, conductivity and oxygen). Water samples were collected using 10-liter bottles on a rosette for dissolved oxygen and salinity to monitor/calibrate sensor performance during/after the cruise.


About transmissometer data:

The transmissometer data for 2009, represent the percentage of  light transmission relative to pure water.  These data have only a pre-cruise calibration. The raw voltages acquired during the CTD cast were converted to % light transmission, and voltage could be retrieved if necessary, or to apply a different calibration, from:

Light transmission [%] = (M * voltage output ) + B


or one calculate Beam attenuation coefficient:


c = -(1/z) * ln (light transmission [decimal])


where


M and B are the calibration coefficients.

z is the transmissometer path length (meters).

Light transmission [decimal] is light transmission divided by 100.

M,B and z are input to the CTD configuration file.


For the 2009 cruise, the values used were:


M = 21.0770

B = -1.1840

z = 0.25 m


Transmissometer Sensor Serial Number: CST-831DR




Data files: 


Filenames: cruiseID.NNN, where NNN indicates station number (cruiseIDu.NNN correspond to CTD upcast; cruiseID_ctd_D.NNN, where D indicates CTD downcast or U for upcast).


Example:

nbp0901_ctd_D.001       NBP0901 cruise, downcast CTD, station 001.


Description of data files:


All data files are written in ASCII format, separated by blanks.


First line:

In the first line of the CTD files we report parameters measured at the beginning of the cast (downcast).


The first line of data files is in the format:

 

TPPCC SSSS   CN   SDD.DDDD  SDDD.DDDD  YYYY/MM/DD    YDA  HH:MM    CRUISE_ID

C3206  104  1 -74.1660 -104.0021 2009/01/31  31 18:01  NBP0901



                T  -  Data type (C: CTD, B: bottle)

                PP - NODC platform code

                CC - NODC country code of the platform

                SSS - Station number (001-160).

                CN - Cast number

                SDD.DDDD - Latitude in decimal degrees  at GMT (S; sign, negative in the Southern hemisphere)

                SDDD.DDDD - Longitude in decimal degrees at GMT (S: sign, negative in the Western Hemisphere).

                YY/MM/DD - Date: year/month/day

                YDA - Year-day for year of collection

                HH:MM - hour:minutes (GMT) at the start (D) or end (U) of each cast.

                CRUISE_ID - Internal (LDEO) cruise name.


Second line:

The second line is preceded by the "&" character and contains additional cast information:


&zc:321  zm:8  ta:-4.2  ap:997.6  ws:2.3  wd:136


 

zc Bottom depth in meters, approximately CTD maximum depth + ZM. 

zm Closest approach of the CTD to the bottom in meters. 

ta Air temperature in °C. 

ap Barometric sea surface pressure in milibars.

ws Wind speed in meters/sec. 

wd Wind direction in degrees from North.


For CTD files: 

The third line begins with “@” where each data column is identified by a two letter mnemonic:


@pr te sa ox pt tr de


pr Pressure [decibars].

te In-situ temperature [°C] (IPTS-68).

sa Salinity (PSS-78).

ox Oxygen [ml/l].

de       Depth [m].

tr Light transmission [%].

pt Potential Temperature [°C].




NO VALUES:  indicated by -9.



Contacts:  Stan Jacobs           sjacobs@ldeo.columbia.edu

        Claudia Giulivi      claudiag@ldeo.columbia.edu