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