CTD Data Format Document September 27, 2024 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 h001a0203.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 32MW013/1. 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, KI=Ka'Imikai-O-Kanaloa,KB= Kilo Moana) 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, transmission, chloropigments, Number of Observations and quality. Missing values are flagged with -99.0 or -9.0. Starting with cruise HOT-173 (2006) until HOT-302 (2018), the transmission was replaced by continuous Nitrate concentration 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) from HOT-173 until HOT-302. 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 33KB300/1 WHP-ID PRS2 DATE 022518 1 STNNBR 2 CASTNO 1 NO. RECORDS= 513 2 INSTRUMENT NO. 91361 SAMPLING RATE 24.00 HZ 3 CTDPRS CTDTMP CTDSAL CTDOXY NITRATE CHLPIG NUMBER QUALT1 DBAR ITS-90 PSS-78 UMOL/KG UMOL/KG uG/L OBS. * ******* ******* ******* ******* ******* ******* * 0.0 23.1118 35.0368 214.7 -4.004 0.1129 0 226663 2.0 23.1258 35.0368 214.7 -4.004 0.2340 0 226662 4.0 23.1274 35.0368 214.7 -4.004 0.1965 36 222162 6.0 23.1260 35.0369 215.2 -4.004 0.2044 72 222162 1004.0 4.1456 34.4756 39.8 43.591 0.0852 48 222122 1006.0 4.1436 34.4756 39.9 42.590 0.0839 108 222122 1008.0 4.1421 34.4760 39.9 44.560 0.0840 48 222122 1010.0 4.1391 34.4765 40.0 45.177 0.0846 36 222122 1012.0 4.1378 34.4763 40.0 45.415 0.0839 120 222122 1014.0 4.1348 34.4769 40.1 46.851 0.0845 48 222122 1016.0 4.1313 34.4772 40.1 44.771 0.0844 36 222122 1018.0 4.1292 34.4772 40.1 41.733 0.0831 120 222122 1020.0 4.1238 34.4780 40.1 42.120 0.0845 48 222122 1022.0 4.1214 34.4784 40.2 43.425 0.0851 48 222122 1024.0 4.1218 34.4783 -9.0 43.967 0.0817 36 222522