Current direction, bathythermograph (xbt), CTD, and other data from moored current meter casts and other instruments in the Gulf of Mexico as part of the Gulf of Mexico Physical Oceanography (GMPO) project, 1987-04-04 to 1988-11-02 (NCEI Accession 8900259)

Current direction, bathythermograph (xbt), CTD, and other data were collected using moored current meter casts and other instruments in the Gulf of Mexico from April 4, 1987 to November 2, 1988. Data were submitted by Science Applications, INC - Raleigh NC as part of the Gulf of Mexico Physical Oceanography (GMPO) project. Data has been processed by NODC to the NODC standard F015- Current Meter Data, F022- CTD High Resolution, C100- Ocean Station Data, and C116/118- Bathythermograph XBT formats.

The F015 format is used for time series measurements of ocean currents. These data are obtained from current meter moorings and represent Eulerian method of current measurement, i.e., the meters are deployed at a fixed point and measure flow past a sensor. Position, bottom depth, sensor depth, and meter characteristics are reported for each station. The data record comprises values of east-west (u) and north-south (v) current vector components at specified date and time. Current direction is defined as the direction toward which the water is flowing with positive directions east and north and negative directions west and south. Data values may be subject to averaging or filtering and are typically reported at 10-15 minute time intervals. Water temperature, pressure, and conductivity or salinity may also be reported. A text record is available for optional comments.

The F022 format contains high-resolution data collected using CTD (conductivity-temperature-depth) and STD (salinity-temperature-depth) instruments. As they are lowered and raised in the oceans, these electronic devices provide nearly continuous profiles of temperature, salinity, and other parameters. Data values may be subject to averaging or filtering or obtained by interpolation and may be reported at depth intervals as fine as 1m. Cruise and instrument information, position, date, time and sampling interval are reported for each station. Environmental data at the time of the cast (meteorological and sea surface conditions) may also be reported. The data record comprises values of temperature, salinity or conductivity, density (computed sigma-t), and possibly dissolved oxygen or transmissivity at specified depth or pressure levels. Data may be reported at either equally or unequally spaced depth or pressure intervals. A text record is available for comments.

The Oceanographic Station Data (C100) format contains physical-chemical oceanographic data recorded at discrete depth levels. Most of the observations were made using multi-bottle Nansen casts or other types of water samplers. A small amount (about 5 percent) were obtained using electronic CTD conductivity-temperature-depth) or STD (salinity-temperature-depth) recorders. The CTD/STD data were reported to NODC at depth levels equivalent to Nansen cast data, however, and have been processed and stored the same as the Nansen data. Cruise information (e.g., ship, country, institution), position, date, and time, and reported for each station. The principal measured parameters are temperature and salinity, but dissolved oxygen, phosphate, total phosphorus, silicate, nitrate, nitrite, and pH may be reported. Meteorological conditions at the time of the cast (e.g., air temperature and pressure, wind, waves) may also be reported, as well as auxiliary data such as water color (Forel-Ule scale), water transparency (Secchi disk depth), and depth to bottom. Values of density (sigma-t), sound velocity, and dynamic depth anomaly are computed from measured parameters. Each station contains the measurements taken at the observed depth levels, but also includes data values interpolated to a set of standard depth levels.

The C116/C118 format contains temperature-depth profile data obtained using expendable bathythermograph (XBT) instruments. Cruise information, position, date and time were reported for each observation. The data record was comprised of pairs of temperature-depth values. Unlike the MBT Data File, in which temperature values were recorded at uniform 5 m intervals, the XBT data files contained temperature values at non-uniform depths. These depths were recorded at the minimum number of points ("inflection points") required to accurately define the temperature curve. Standard XBTs can obtain profiles to depths of either 450 or 760 m. With special instruments, measurements can be obtained to 1830 m. Prior to July 1994, XBT data were routinely processed to one of these standard types. XBT data are now processed and loaded directly in to the NODC Ocean Profile Data Base (OPDB). Historic data from these two data types were loaded into the OPDB.

Tags: oceanography
Organization: National Oceanic and Atmospheric Administration, Department of Commerce