Bathythermograph (BT) Data The following group of four related files contains temperature profile data (temperature versus depth) from the mechanical bathythermograph (MBT) and its successor instrument, the expendable bathythermograph (XBT). Although the NODC still receives some MBT data (in digital form) from foreign sources, most new data are from XBTs. XBT data are received in delayed mode as analog strip charts (that must be digitized), as digital data already derived from analog strip charts, and, increasingly, as digital data recorded directly on cassette tapes by newer XBT systems. NODC also receives BT data in near- real-time as telecommunicated (radio message) observations collected in support of the Integrated Global Ocean Services System (IGOSS). Because they vary in quality, the way in which they are reported to the NODC, and the depths at which they are recorded, the data are maintained in separate files. The data are all recorded in the same format, however, and may be merged if desired. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ File: MECHANICAL BATHYTHERMOGRAPH (MBT) DATA This file format is used for temperature-depth profile data obtained using the mechanical bathythermograph (MBT) instrument. The maximum depth of MBT observations is approximately 285 m. Therefore, MBT data are useful only in studying the thermal structure of the upper layers of the ocean. Cruise information, date, position, and time are reported for each observation. The data record comprises pairs of temperature-depth values. Temperature data in this file are recorded at uniform 5 m depth intervals. (Note: The mechanical bathythermograph instrument is now obsolete, having been superseded by the faster, easier-to-operate expendable bathythermograph.) ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ File: EXPENDABLE BATHYTHERMOGRAPH (XBT) DATA This file format is used for temperature-depth profile data obtained using expendable bathythermograph (XBT) instrument. Standard XBTs can obtain profiles at depths of about 450 or 760 m. With special instruments, measurements can be obtained to 1830 m. Cruise information, position, date, and time are reported for each observation. The data record comprises pairs of temperature-depth values. Unlike the MBT data file, in which temperature values are recorded at uniform 5m intervals, the XBT Data File contains temperature values at non-uniform depths. These depths are at a minimum number of points ("inflection points") required to record the temperature curve to an acceptable degree of accuracy. On output, however, the user may request temperature values either at inflection points or interpolated to uniform depth increments. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ File: SELECTED DEPTH BATHYTHERMOGRAPH DATA (SBT) This file format is used for temperature-depth data obtained from mechanical (MBT) and expendable (XBT) bathythermograph instruments. Data in this file were sent to NODC at depths selected by the originator - usually at standard horizons or some fixed interval. The MBT file holds data reported at a 5-meter depth interval, and depths in the XBT file are chosen at significant inflection points of the temperature-depth profile. SBT data can be selected from specific geographic regions or from specified cruises. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ File: RADIO MESSAGE BATHYTHERMOGRAPH DATA (IBT) This file format is used for telecommunicated bathythermograph (principally XBT) data transmitted by ships at sea over the Global Telecommunications System in the Integrated Global Ocean Services System (IGOSS) BATHY format. These data are accumulated and transmitted to NODC from two U.S. operational centers: the NOAA National Meteorological Center (NMC) and the U.S. Navy Fleet Numerical Oceanography Center (FNOC). Like XBT data, IBT data temperature values are recorded at inflection point depths. The BATHY radio message allows for a limited number of depth-temperature pairs to be reported, however. Therefore, compared to delayed-mode XBT data, IBT data present a coarser representation of ocean temperature profiles. File Structure: One variable-length record (maximum 2,540 characters). File Format: (Universal for all four BT data types) Bathythermograph Data (BT) PARAMETER DESCRIPTION STARTING FIELD COLUMN LENGTH TWO-CHARACTER CODE - ('X '=XBT AT INFLECTION POINT DEPTHS; FILE ID 'M '=MBT AT 5-METER DEPTHS; 1 2 'XS'=XBT AT ORIGINATOR DEPTHS; 'MS'=MBT AT ORIGINATOR DEPTHS) AREA ONE-DIGIT CODE - WMO QUADRANT (= 1, 3, 5, OR 7) 3 1 LATITUDE DDMMX (DEGREES, MINUTES TO TENTHS) 4 5 LATITUDE ONE-CHARACTER CODE - 'N' OR 'S' 9 1 HEMISPHERE LATITUDE ONE-DIGIT CODE - USE NODC CODE 0606 10 1 PRECISION LONGITUDE DDDMMX (DEGREES, MINUTES TO TENTHS) 11 6 LONGITUDE ONE-CHARACTER CODE - 'E' OR 'W' 17 1 HEMISPHERE LONGTITUDE ONE-DIGIT CODE - USE NODC CODE 0606 18 1 PRECISION DATE (GMT) YYMMDD - YEAR, MONTH, DAY 19 6 TIME (GMT) XXXX (HOURS AND MINUTES) 25 4 TIME PRECISION ONE-DIGIT CODE - USE NODC CODE 0607 29 1 BLANK ONE BLANK 30 1 SUBMITTING TWO-CHARACTER NODC COUNTRY CODE 31 2 COUNTRY BLANK ONE BLANK 33 1 SUBMITTING TWO-CHARACTER NODC INSTITUTION CODE 34 2 INSTITUTION CRUISE XXXXX - NODC CRUISE NUMBER 36 5 CONSEC XXXX - NODC CONSECUTIVE STATION NUMBER 41 4 DATA ORIGIN COUNTRY OF TWO-CHARACTER COUNTRY CODE 45 2 PLATFORM INSTITUTION TWO-CHARACTER INSTITUTION CODE 47 2 PLATFORM TWO-CHARACTER PLATFORM CODE 49 2 ONE-CHARACTER CODE - INDICATES OCEAN STATION OSV FLAG VESSEL (OCEAN WEATHER STATION)-USE NODC CODE 51 1 0610 DNP FLAG ONE-CHARACTER CODE - INDICATES DECLARED 52 1 NATIONAL PROGRAM STATUS-USE NODC CODE 0609 BLANK TWO BLANKS 53 2 CRUISE XXXXXXXX - ORIGINATOR'S CRUISE NUMBER 55 8 CONSEC XXXX - ORIGINATOR'S CONSECUTIVE STATION NUMBER 63 4 XBT CALIBRATION XXX - DEPTH AT CALIBRATION TICK; UNITS (METERS, 67 3 DEPTH FEET) DEPENDING ON PROBE TYPE XBT CALIBRATION XXX - TEMPERATURE AT CALIBRATION TICK; (DEG C TEMPERATURE TO TENTHS OR DEG F TO TENTHS, DEPENDING ON 70 3 PROBE TYPE) INSTRUMENT TYPE ONE-DIGIT CODE - (1 = XBT, 2 = HXBT, 3 = SXBT, 73 1 4 = AXBT, BLANK = MBT) MBT GRID OR XBT ONE-CHARACTER CODE - USE NODC CODE 0616 OR CODE 74 1 PROBE TYPE 0611 ONE-CHARACTER CODE - INDICATES WHETHER XBT XBT BOTTOM FLAG PROBE HIT BOTTOM (B = YES, BLANK = NO - NODC 75 1 CODE 0617) XBT DIGITIZATION TWO-DIGIT CODE - USE NODC CODE 0612 76 2 METHOD XBT DIGITIZATION TWO-DIGIT CODE - USE NODC CODE 0613 78 2 INTERVAL XBT DATA TREATMENT AND TWO-DIGIT CODE - USE NODC CODE 0614 80 2 STORAGE BOTTOM DEPTH XXXX (WHOLE METERS) 82 4 MBT CORRECTION XXX (WHOLE METERS; NEGATIVE VALUE PRECEDED BY 86 3 DEPTH MINUS SIGN) MBT TEMPERATURE XXX (DEG C TO TENTHS; NEGATIVE VALUE PRECEDED 89 3 CORRECTION SIGN) MBT REFERENCE TEMPERATURE ONE-DIGIT CODE - USE NODC CODE 0615 92 1 TYPE MBT REFERENCE XXX (DEG C TO TENTHS) 93 3 TEMPERATURE COUNT XXXX - NUMBER OF DEPTH -TEMPERATURE PAIRS 96 4 (MAXIMUM = 305) BLANK ONE BLANK 100 1 DEPTH* XXXX (WHOLE METERS) 101 4 TEMPERATURE* XXXX (DEG C TO HUNDREDTHS) 105 4 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ *DEPTH-TEMPERATURE PAIRS (8 CHARACTERS) REPEATED AS MANY TIMES AS INDICATED BY 'COUNT' FIELD UP TO MAXIMUM OF 305 PAIRS (2440 CHARACTERS); MAXIMUM RECORD LENGTH, THEREFORE EQUALS 2440 + 100 (HEADER INFORMATION) = 2540 CHARACTERS. NODC Code Tables Used with this Format CODE NUMBER CODE NAME 0606 POSITION PRECISION 0607 TIME PRECISION 0609 DECLARED NATIONAL PROGRAM 0610 OCEAN WEATHER STATION 0611 XBT PROBE TYPE 0612 DIGITIZATION METHOD 0613 DATA INTERVAL (XBT) 0614 DATA TREATMENT AND STORAGE 0615 BT REFERENCE TEMPERATURE 0616 UBT FILE ID 0617 BOTTOM HIT -- NODC COUNTRY CODE -- NODC PLATFORM (SHIP) CODE -- NODC INSTITUTION CODE