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TAO
Sampling
The TAO Project Office provides near-real-time daily-averaged surface and subsurface data from ATLAS moorings as our standard product for climate research. Daily averages are computed starting at 0000GMT and are assigned an observation "time stamp" of 12000GMT. Higher resolution data are recorded onboard the moorings and are made available after mooring recoveries, which are scheduled on an annual basis. High resolution data from older ATLAS moorings prior to 1991 (Mangum et al., 1995) and Current Meter moorings through spring 1999 (Freitag et al., 1991) consisted of a variety of sampling and averaging periods. The
tables below describe the present sampling schemes for Next Generation
and Standard ATLAS moorings. Observation times in data files are assigned
to the center of the averaging interval unless otherwise noted. Basic
measurements on ATLAS moorings are winds, air temperature, relative humidity,
SST, and 10 subsurface temperatures. NextGeneration ATLAS moorings have
the flexibility for additional sensors (rainfall, shortwave and longwave
radiation, barometric pressure, salinity and ocean currents) which are
deployed at selected mooring sites often in collaboration with other research
programs. Basic data from ATLAS moorings are also available on the GTS
network.
[2] To minimize spiking in the salinity record due to sensor response time mismatches, the internally recorded 10-minute conductivity and temperature values are smoothed with a 13-point Hanning filter and subsampled at hourly intervals. Salinities are calculated from the smoothed hourly conductivity and temperature values using the method of Fofonoff and Millard (1983). These hourly data constitute the high-resolution salinity time series in the data base. High-resolution temperatures are offered at their original 10-minute sampling increment. Standard ATLAS Sampling
Data from these moorings
are available only after mooring recoveries, which are scheduled on an
annual basis. The sampling scheme for TAO ADCP moorings maintained by
PMEL are listed below.
ADCP data from moorings maintained by PMEL have been corrected for variations in sound velocity. The ADCP nominal bin width and pulse length were set to 8m, resulting in a velocity measurement that represents a weighted average over a nominal 16m depth, sampled at approximately 8m-depth intervals. The data available here have been remapped by linear interpolation to 5m depth intervals. Daily average data are computed as an average of 0000 to 2300 hr, requiring a minimum of 6 good hourly values. In contrast to the
present upward-looking subsurface moorings, some downward-looking surface
moorings were deployed in the past. ADCP data from these moorings (named
PROTEUS) at 170W, 140W, and 110W were at times significantly biased due
to the presence of fish near the moorings. Corrections to the 140W and
110W ADCP data have been made using coincident mechanical current meter
data (Plimpton et al., 2000). Corrections to the 170W data have
been made by analysis of the ADCP echo intensity (Plimpton et al.,
1997). Corrections were made to daily mean velocity profiles only. Hourly
data have not been corrected, but erroneous hourly values have been edited
out of the original time series. ADCP data from PROTEUS moorings at 0, 156E and 0, 165E did not appear to have significant bias due to fish. PROTEUS moorings were
deployed for the following time periods: May 1991 to August 1995 at 110W;
May 1990 to September 1995 at 140W; April 1993 to March 1994 at 170W;
March 1991 to January 1996 at 165E; August 1991 to March 1993 and April
to December 1994 at 156E. For details on the
JAMSTEC data see Kutsuwada and Inaba (1995). For the USF data see Weisberg
and Hayes (1995), and Plimpton et al. (1997). Sampling schemes
from earlier generation TAO ADCP moorings can be found in Plimpton et
al. (2000). References: Freitag,
H.P., M.J. McPhaden, C.S. Coho, and A.J. Shepherd (1991): Equatorial wind,
current and temperature data: 108°W to 140°W; April 1983 to October 1987.
NOAA Data Report ERL PMEL-35 (PB92-119817), 116 pp. Mangum, L.J., H.P. Freitag, and M.J. McPhaden (1995): TOGA TAO array sampling schemes and sensor evaluations. Proceedings, Oceans '94 OSATES, 13-16 September 1994, Parc de Penfeld, Brest, France, II-402-II-406. Plimpton,
P.E., H.P. Freitag, and M.J. McPhaden (2000): Correcting moored ADCP data
for fish-bias errors at 0°, 110°W and 0°, 140°W from 1993 to 1995. NOAA
Tech. Memo. OAR PMEL-117, 35 pp. Plimpton, P.E., H.P
Freitag, M.J McPhaden, and R.H. Weisberg, (1997): "Using echo intensity
to correct moored ADCP data for fish-bias error at 0, 170W", NOAA Technical
Memorandum ERL PMEL-111, 17pp. Serra, Y.L., P.A'Hearn, H.P. Freitag, and M.J. McPhaden, 2001: ATLAS self-siphoning rain gauge error estimates. J. Atmos. Ocean. Tech., 18, 1989-2002. Weisberg, R.H. and S.P. Hayes (1995): "Upper ocean variability on the equator in the west-central Pacific at 170W", J. Geophys. Res., 100, pp. 20485-20498. |
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