ATLAS/TOPEX POSEIDON MOORING - BOTTOM PRESSURE RECORDER DATA

F. Gonzalez (NOAA/PMEL, USA)

Announced availability: 1 July 1994

Data Access

EP 42 Bottom Pressure Recorder (BPR) data are available upon request from NOAA's National Oceanographic Data Center (NODC) in Silver Spring, MD (http://www.nodc.noaa.gov) and from the National Center for Atmospheric Research (NCAR) in Boulder, CO (http://dss.ucar.edu/pub/toga_coare/).

Background

During the verification phase of the TOPEX/POSEIDON radar altimeter mission a rigorous open-ocean validation experiment was conducted in the western equatorial Pacific ocean. From August/September 1992 to February/March 1993, two TOGA-TAO moorings at 2S 156E (1739m depth) and 2S, 164.4E (4400 m depth) were enhanced with additional temperature, conductivity and pressure sensors to measure precisely the dynamic height from the surface to the bottom at 5 min intervals directly beneath two TOPEX/POSEIDON crossovers.

Enhanced instrumentation on the Atlas mooring at 2S 156E included 16 Seacats (SB-16, two with pressure sensors), 5 MTRs, and 1 Aanderaa recorder (pressure and temperature). At 2S 164.4E, 11 Seacats (two with pressure sensors), 12 MTRs, and 2 Aanderaa recorders were added.

Enhanced bottom measurements were made within one mile of each Atlas. O ne Bottom Pressure Recorder (BPR) and two IES were located near 2S 156E and one BPR and one IES near 2S 164.4E.

The BPR was positioned at 2 00.37 S, 164 25.08 E from 26 August 1992 through 24 March 1993 and recorded pressure and temperature data at a depth of 4430 m (determined by density of standard seawater).

Data File Information

Number of data files: 4

File EP42-2HRLP.DAT
Edited pressure [psia] and temperature [C] data having a sampling interval of 15 seconds were two-hour low-pass filtered (2HRLP) with a Lanczos square filter. At the two-hour cutoff period, the amplitude is reduced by half. After filtering, data are decimated to one-hour intervals.
Start/End of 2HRLP data: 26 August 92 17:00:00/23 March 93 21:00:00

File EP42-40HRLP.DAT
A 40HRLP filter (amplitude reduced by half at 40-hour period) was applied to the 2HRLP data.
Start/End of 40HRLP data: 30 August 92 17:00:00/19 March 93 21:00:00

File EP42-TID-CONST.DAT
A harmonic tidal analysis using the formulation of Foreman (1) is performed on the 2HRLP data. Constituent name, frequency, amplitude [psia], and phase [Greenwich] appear in this file.

File EP42-STATS.DAT
Statistics from EDITED, 2HRLP, 2-40HRBP, and 40HRLP pressure [psia] and temperature [C] data.

**NOTE: 1 psia = 68.947 mb

Dataset format: ASCII
Dataset volume: 491,252 bytes

Data Example 

EP42 (50465; 13; 21)    FILTERED DATA
    Series Start/End time:  8/26/92 17: 0: 0.00    3/23/93 21: 0: 0.00
 Subseries Start/End time:  8/26/92 17: 0: 0.00    3/23/93 21: 0: 0.00
 Time listed below corresponds with the center of the "original" sampling period
 MO/DA/YR HR:MN:SE       2HRLP P [psia]   2HRLP T [C]
  8/26/92 17: 0: 7.50     6472.2573       1.3590
  8/26/92 18: 0: 7.50     6471.7681       1.3593
  8/26/92 19: 0: 7.50     6471.0898       1.3593
  8/26/92 20: 0: 7.50     6470.3760       1.3588
  8/26/92 21: 0: 7.50     6469.7959       1.3591
  8/26/92 22: 0: 7.50     6469.4941       1.3591

Data Processing and Analysis

Data were recorded on hard disk, transferred to a PC and then to PMEL's VAX for processing. The recorded pressure and temperature crystal frequencies were converted to pressure [psia] and temperature [C] using calibration coefficients supplied by Paroscientific, Inc. The data were then edited to remove "outliers", if present, replacing them with data linearly interpolated from adjacent good values. Fifty-eight pressure and 35 temperature values (out of a total of 1208701 values in each series) were flagged as outliers and replaced. Pre-deployment and post-recovery segments have been removed from this record. Also note that filtered time series are shorter due to data loss on each end corresponding to half the filter length.

A temperature offset of -1.03 degrees C has been added to all temperature data. This offset was determined by a post-deployment calibration and examination of a Mini Temperature Recorder (MTR) deployed near EP42 at 1 59.4S, 164 29.0E.

Start/End of edited data: 26 August 92 09:00:00/24 March 93 05:15:00

For more information, please contact:

Marie Eble
NOAA/PMEL
7600 Sand Point Way NE
Seattle, WA 98115
USA

email: eble@pmel.noaa.gov

or

Frank Gonzalez
NOAA/PMEL
7600 Sand Point Way NE
Seattle, WA 98115
USA

email: gonzalez@pmel.noaa.gov

References

Foreman, M.G.G., 1977: Manual for tidal heights analysis and prediction. Pacific Marine Science Report 77-10, Institute of Ocean Sciences, Patricia Bay, Victoria, B.C., 70 pp.

Gourdeau, L., J. Picaut, M.J. Langlade, A. Busalacchi, E. Hackert, M. McPhaden, P. Freitag, F. Gonzalez, M. Eble, R. Weller, 1995: Traitements des donnees pour la validation en plein ocean du niveau de la mer de POPEX/POSEIDON dans le Pacifique equatorial ouest. Notes Techniques, Sciences de la Mer, Oceanographie Physique, No 12, ORSTOM, Centre de Noumea, 43 pp.

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