CTD Data Format Document June 18, 2008 CTD data are distributed in a format specified by the international WOCE Hydrographic Programme Office (WHPO). This document describes that format. Each station/cast is stored in a separate file. A file's name can be determined by the concatenation of 'h', 3 digit cruise number, 'a', a 2 digit station number, a 2 digit cast number and a file extension of ctd. For ex- ample, HOT-1, station 2, cast 3, would be found in h01a0203.ctd. The cruise and position information for each cast is in the cruise summary file (*.sum). The EXPOCODE, station number and cast number can be used to cross-reference the CTD data files with the cruise summary file. This code allows for the identification of the cruise. It consists of a 4 character NODC country-ship code, a maximum of 8 character cruise number followed by a "/" and leg number. For example, the EXPOCODE for HOT-13 on the R/V Moana Wave would be 31MW013/1. The CTD data file has a fixed record length of 65 characters / record. The first six records of a CTD file contain header information: Record 1: Column Format Item 9-22 a14 EXPOCODE (KA=Kaimalino,WE=Wecoma,MW=Moana Wave) 31-34 a4 WHP station identification 41-42 i2 Month 43-44 i2 Day 45-46 i2 Year FORTRAN FORMAT (8x,a14,8x,a4,6x,3i2) C "%*s %s %*s %s %*s %2d%2d%2d" Record 2: 7-12 a6 Station number 20-22 i3 Cast number 36-40 i5 Number of data records in the file FORTRAN FORMAT (6x,a6,7x,i3,13x,i5) C "%*s %d %*s %d %*s %d" Record 3: 16-21 i6 Instrument number 37-41 f5.2 Sampling rate (hz) FORTRAN FORMAT (15x,i6,15x,f5.2) C "%*s %d %*s %f" Record 4: Headers for data columns (variable labels). Record 5: Unit header for data columns. Record 6: Quality byte designators. All columns requiring a quality byte are underscored by seven asterisks. The remaining records contain CTD data. The order of variables in a record are as follows: pressure, temperature, salinity, oxygen, trans- mission, chloropigments and quality. Missing values are flagged with -99.0. Starting on HOT-177 (2006), the transmission have been replaced by continuous Nitrate data (see Readme.ctd). Data Record Format: Column Format Item 1-8 f8.1 Pressure (Decibars) 9-16 f8.4 Temperature (Degrees Celsius, International Temperature Scale of 1990) 17-25 f9.4 Salinity (1978 International Practical Salinity Scale) 26-33 f8.1 Oxygen (micromoles per kilogram) 34-41 f8.3 Transmission (% transmission), Nitrate (micromoles per kilogram) after HOT-176 42-49 f8.3 Chloropigments (microgram/liter) 50-57 i8 Number of observations averaged at this pressure level 58-65 i8 Quality (defined by investigator) ** FORTRAN FORMAT (f8.1, f8.4, f9.4, f8.1, 2f8.3, i8, i8) C "%f %f %f %f %f %f %d %d" ** The quality word is the left-to-right concatenation of required quality bytes for the variables measured. They are defined as follows: byte value Definition 1 Not calibrated with water samples. 2 Acceptable measurement. 3 Questionable measurement. 4 Bad measurement. 5 Not reported. 6 Interpolated value. 7 Not assigned for CTD data 8 Not assigned for CTD data 9 Not sampled Sample File: (First and last few records) EXPOCODE 31MW013/1 WHP-ID PRS2 DATE 010790 1 STNNBR 1 CASTNO 2 NO. RECORDS= 512 2 INSTRUMENT NO. 91361 SAMPLING RATE 24.00 HZ 3 CTDPRS CTDTMP CTDSAL CTDOXY XMISS FLUOR NUMBER QUALT1 DBAR DEG C PSS-78 UMOL/KG %TRANS WT/CM2 OBS. * ******* ******* ******* ******* ******* ******* * 0.0 25.0409 34.9405 -99.0 -99.000 0.008 36 222992 2.0 25.0391 34.9409 -99.0 -99.000 0.008 204 222992 4.0 25.0381 34.9411 -99.0 -99.000 0.008 84 222992 6.0 25.0379 34.9412 -99.0 -99.000 0.008 36 222992 1004.0 3.8761 34.5064 -99.0 -99.000 0.009 60 222992 1006.0 3.8740 34.5063 -99.0 -99.000 0.009 60 222992 1008.0 3.8729 34.5065 -99.0 -99.000 0.009 48 222992 1010.0 3.8719 34.5064 -99.0 -99.000 0.009 96 222992 1012.0 3.8726 34.5064 -99.0 -99.000 0.010 60 222992 1014.0 3.8721 34.5064 -99.0 -99.000 0.009 60 222992 1016.0 3.8715 34.5065 -99.0 -99.000 0.009 84 222992 1018.0 3.8700 34.5066 -99.0 -99.000 0.009 60 222992 1020.0 3.8700 34.5066 -99.0 -99.000 0.009 180 222992 1022.0 3.8705 34.5066 -99.0 -99.000 0.009 477 222992