ALACE subsurface drifter data in South Pacific, for March 1995 (NCEI Accession 9500149)
The ALACE (Autonomous LAgrangian Circulation Explorer) is a subsurface drifter, periodically rising to the surface to relay data to ARGOS. Instrument location is then obtained from ARGOS. An ALACE profiler collects data on ascent and relays a compressed data set to ARGOS. The amount of time spent at its neutrally-buoyant depth, and then at the surface, is variable, dependent upon the deployment site and the main scientific objective of the ALACE. Profiling ALACEs generally complete a cycle every 8-10 days, spending 24 hours at the surface transmitting to ARGOS.
Dataset Citation
- Cite as: Sherman, Jeffrey T.; Scripps Institution of Oceanography (2002). ALACE subsurface drifter data in South Pacific, for March 1995 (NCEI Accession 9500149). [indicate subset used]. NOAA National Centers for Environmental Information. Dataset. https://www.ncei.noaa.gov/archive/accession/9500149. Accessed [date].
Dataset Identifiers
ISO 19115-2 Metadata
gov.noaa.nodc:9500149
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Ordering Instructions | Contact NCEI for other distribution options and instructions. |
Distributor |
NOAA National Centers for Environmental Information +1-301-713-3277 NCEI.Info@noaa.gov |
Dataset Point of Contact |
NOAA National Centers for Environmental Information ncei.info@noaa.gov |
Time Period | 1995-03-01 to 1995-03-22 |
Spatial Bounding Box Coordinates |
West: -155.26
East: 10.48
South: -70.46
North: 35.12
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Data Presentation Form | Digital table - digital representation of facts or figures systematically displayed, especially in columns |
Dataset Progress Status | Complete - production of the data has been completed Historical archive - data has been stored in an offline storage facility |
Data Update Frequency | As needed |
Supplemental Information | DEPTH-AVERAGING A profile is taken on ascent, with T sampled every 3 s while ALACE is ascending at 10-15 cm/s. The data is depth-averaged and compressed for transmission through ARGOS. The degree of averaging increases with depth. For instance, a profile might start out with 5 m resolution from 0-200 m depth, switching to 10 m resolution from 200-800 m, followed by 20 m resolution to 1200 m. SENSOR DESCRIPTION TEMPERATURE: A thermistor bead from YSI (YSI-44016) is used, having a typical drift of <0.01 deg. C over 1 year, increasing to 0.02 deg. C over 8 years. Laboratory calibration of thermistors typically have less than 0.002 deg. C standard deviation. The largest error comes from the 12-bit a/d (Linear Technology's LTC1290) which resolves T to 0.01-0.02 deg C, with better resolution obtained at low temperatures. PRESSURE: A Paines 210-38 with 0-3000 PSI range is used. Quoted accuracy from thermal drift, non-linearity, hysteresis, and repeatability is ~10 dBar. Observations of a few units in laboratory testing suggest an accuracy of ~5 dBar. OTHER PROFILING ALACEs: At this time, there are a few CTD ALACEs. Sampling and data format are the same as the temperature profiler, with the addition of conductivity also being transmitted. The units have not been thoroughly tested for long-term accuracy, and thus their data sets are not ready for release. SUBSURFACE DRIFT RATE The difference in locations between profiles includes the subsurface drift and the 24 hour surface drift in one complete ALACE cycle. Therefore the NODC data set itself could be used to estimate deep currents, but accuracy would be limited by the unknown surface drift. Dr. Davis uses a fairly sophisticated algorithm to extrapolate the surface drift from the set of ARGOS fixes for the 24 hours ALACE is transmitting. I believe Russ Davis's intent is to provide temperature profiles in the same format as the NODC XBT data set, so people can readily use the ALACE data without requiring any further programming. |
Purpose | This dataset is available to the public for a wide variety of uses including scientific research and analysis. |
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NODC DATA TYPES THESAURUS
NODC OBSERVATION TYPES THESAURUS
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Instrument keywords | NODC INSTRUMENT TYPES THESAURUS Global Change Master Directory (GCMD) Instrument Keywords |
Place keywords | NODC SEA AREA NAMES THESAURUS Global Change Master Directory (GCMD) Location Keywords |
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Last Modified: 2023-08-08T18:04:06Z
For questions about the information on this page, please email: ncei.info@noaa.gov
For questions about the information on this page, please email: ncei.info@noaa.gov