The TAO project: Sensors

			Sensor specifications

Last updated: Monday August 25, 2008 (PDT)

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This table identifies the types of sensors used on TAO moorings and lists their accuracies. Most instrumental accuracies listed are based on pre-deployment and post-recovery calibrations and are the root mean square drift of a group of sensors. Mechanical current meters and current profilers accuracies are based on intercomparisons between co-located instruments. References where available are indicated by [#] in the comments column and listed at the end of the tables. Accuracies of sensors which are new to TAO moorings (longwave radiation, barometric pressure) or which have not yet been evaluated by TAO (water pressure) are those specified by the manufacturer and are indicated by [M].

In cases where sensors are paired with PMEL supplied electronics (e.g., analog to digital boards) calibrations include both the sensor and PMEL electronics. Accuracies listed here (with the exception of currents) do not include environmental factors such as wind (on rainfall) or buoy motion(on radiation). Measurement ranges listed are generally those over which the sensors are calibrated. The ranges over which a sensor will operate (determined by the sensor and/or PMEL electronics) are listed in parenthesis if they significantly exceed the calibration range.

The array is presently maintained with Next Generation ATLAS moorings, sensors for which are shown in the top (blue shaded) table. Sensor specifications for standard ATLAS and early current meter moorings (both of which are no longer in use) are shown in the bottom table.

A comparison of ATLAS, TRITON, and IMET mooring meteorological sensors from a land-based intercomparison study at the Woods Hole Oceanographic Institution in May-June 2000 shows that in general the three systems measure to equivalent standards of accuracy. The full report of this intercomparison is contained in footnote [13] below.

Next Generation ATLAS Mooring Sensors

Measurement	Sensor type	Manufacturer: Model #	Resolution	Range	Accuracy	Comments
Wind speed	Propeller	R. M. Young: 05103	0.2 m s^-1	1-20 m s^-1 (0.4 - 36 m s^-1)	±0.3 m s^-1 or 3%	[7]
Wind direction	Vane	R. M. Young: 05103	1.4°	0-355°	5° - 7.8°	[7] See also footnote to [7]
Wind direction	Fluxgate compass	E.G.and G. 63764 or KVH LP101-5	1.4°	0-359°	5° - 7.8°	[7] See also footnote to [7]
Air temperature	Pt-100 RTD (Resistance Temperature Recorder)	Rotronic Instrument Corp.: MP-100	0.01°C	14-32°C (0-40°C)	±0.2°C	[12]
Relative humidity	Capacitance	Rotronic Instrument Corp.: MP-100	0.4 %RH realtime 0.02 %RH delay mode	55-95 %RH (0-100 %RH)	±2.7 %RH	[12]
Rainfall	Capacitance	R. M. Young: 50203-34	0.2 mm hr^-1	0-50 mm	±0.4 mm hr^-1on 10 min filtered data	[6]
Downwelling shortwave radiation	Pyranometer	Eppley Laboratory: PSP-TAO, Delrin case	0.4 W m^-2	200-1000 W m^-2 (0-1600 W m^-2)	±2%	[15]
Downwelling longwave radiation	Pyrgeometer	Eppley Laboratory: PIR-TAO, Delrin case, 3-output (1)	0.1 W m^-2 0.03°C	200 W m^-2 @ 20°C (thermopile only)	±1%	[M] Nominal calibration values used for case and dome thermistors
Barometric pressure	Pressure transducer	Paroscientific: MET1-2	0.1 hPa	800-1100 hPa	±0.01% of reading	[M]
Sea surface and subsurface temperature	Thermistor	PMEL electronics using YSI (Yellow Springs Instruments) thermistor 46006	0.001°C	6-32°C (0-40°C)	±0.02°C	[14], [9]
Sea surface and subsurface temperature	Thermistor	Sea Bird Electronics: SBE16, SBE37	0.001°C	1-31°C (-5-35°C)	±0.003°C	[3]
Salinity	Internal field conductivity cell	Sea Bird Electronics: SBE16 (Seacat)	0.0001 S m^-1	3-6 S m^-1 (0-6 S m^-1)	±0.02 psu	[3] Based on SBE16 only. SBE37 assumed comparable. Accuracy of PMEL module under evaluation
		SBE37 (Microcat)	0.0001 S m^-1
		Sea Bird cell with PMEL electronics	0.002 S m^-1
Water pressure	Transducer	Paine: 211-30-660-01	0.03 psi	400-800 psi (0-1000 psi)	±1.4 psi	[14]
Ocean current (profile)	Acoustic Doppler Current Profiler	RD Instruments: Narrow band, 150 kHz	0.1 cm s^-1 0.006	(0-256 cm s^-1)	±5 cm s^-1, ±2.5°	[5] [11]
Ocean current (single point)	Dopper Current Meter	SonTek: Argonaut	0.1 cm s^-1 0.1°	(0-600 cm s^-1)	±5 cm s^-1, ±5°	[10]

Standard ATLAS and Early Current Meter Mooring Sensors

Measurement	Sensor type	Manufacturer: Model #	Resolution	Range	Accuracy	Comments
Wind speed	Propeller	R. M. Young: 05103	0.2 m s^-1	1-20 m s^-1 (0.4 - 36 m s^-1)	±0.3 m s^-1 or 3%	[7]
Wind direction	Vane	R. M. Young: 05103	1.4°	0-355°	5° - 7.8°	[7] See also footnote to [7]
Wind direction	Fluxgate compass	E.G.and G. or KVH: 63764 or LP101-5	1.4°	0-359°	5° - 7.8°	[7] See also footnote to [7]
Air temperature	Pt-100 RTD (Resistance Temperature Detector)	Rotronic Instrument Corp.: MP-100	0.04°C	14-32°C (0-40°C)	±0.2°C	[2]
Relative humidity	Capacitance	Rotronic Instrument Corp.: MP-100	0.4 %RH realtime 0.02 %RH delay mode	55-95 %RH (0-100 %RH)	±2.7 %RH	[2]
Downwelling shortwave radiation (Current Meter Moorings)	Pyranometer	Eppley Laboratory: PSP	1.3 W m^-2	700 W m^-2 (0-1600 W m^-2)	±2%	[2]
Sea surface temperature	Thermistor	PMEL: Standard ATLAS SST sensor using YSI (Yellow Springs Instruments) thermistor 46006	0.001°C	14-32°C	±0.03°C	[2]
Sea surface temperature	Thermistor	PMEL: Current meter mooring SST sensor using YSI thermistor 46006	0.001°C	14-32°C	±0.01°C	[2]
Subsurface temperature	Thermistor	PMEL: Standard ATLAS sensor using YSI thermistor 46006	0.001°C	6-32°C (2-35°C)	±0.09°C	[2]
Subsurface temperature	Thermistor	PMEL: Mini Temperature Recorder (MTR) using YSI thermistor 46006	0.001°C	6-29°C (-2-34°C)	±0.01°C	Accuracy based on unpublished PMEL calibrations
Subsurface temperature	Thermistor	EG&G VACM	0.001°C	1-31°C	±0.05°C	[8]
Subsurface temperature	Thermistor	EG&G VMCM	0.006°C	1-31°C	±0.05°C	[8]
Subsurface temperature	Thermistor	Sea Data TR-2, TDR-2	0.01°C	1-31°C (-5-35°C)	±0.05°C	[8]
Sea surface and subsurface temperature	Thermistor	Sea Bird Electronics: SBE16, SBE37	0.001°C	1-31°C (-5-35°C)	±0.003°C	[3]
Salinity	Internal field conductivity cell	Sea Bird Electronics: SBE16 (Seacat)	0.0001 S m^-1	3-6 S m^-1 (0-6 S m^-1)	±0.02 psu	[3]
Water pressure	Transducer	Paine: 211-30-660-01	0.03 psi	400-800 psi (0-1000 psi)	±0.25% full scale (1000psi)	[M]
Ocean current (single point)	Savonious rotor and vane	EG&G VACM	0.005 cm s^-1 2.8°	(2-300 cm s^-1)	±3-7 cm s^-1, ±5.6°	[4]
Ocean current (single point)	Orthogonal Propellers	EG&G VMCM	0.01 cm s^-1 1.4°	(0.9 - 340 cm s^-1)	±3-7 cm s^-1, ±2.5°	[4]
Ocean current (profile)	Acoustic Doppler Current Profiler	RD Instruments: Narrow band, 150 kHz	0.1 cm s^-1 0.006	(0-256 cm s^-1)	±5 cm s^-1, ±2.5°	[5]

References:

[1] Fairall, C. W., P. O. G. Persson, E.F. Bradley, R. E. Payne and S. P. Anderson, 1998: A new look at calibration and use of Eppley Precision Radiometers. Part I: Theory and Application. J. Atmos. Ocean. Tech., 15, 1229-1242.

[2] Freitag, H.P., Y. Feng, L.J. Mangum, M.P. McPhaden, J. Neander, and L.D. Stratton, 1994: Calibration procedures and instrumental accuracy estimates of TAO temperature, relative humidity and radiation measurements. NOAA Tech. Memo. ERL PMEL-104, 32 pp.

[3] Freitag, H.P., M.E. McCarty, C. Nosse, R. Lukas, M.J. McPhaden, and M.F. Cronin, 1999: COARE Seacat data: Calibrations and quality control procedures. NOAA Tech. Memo. ERL PMEL-115, 89 pp.

[4] Halpern, D., 1987: Comparison of upper ocean VACM and VMCM observations in the equatorial Pacific. J. Atmos. Ocean. Tech., 4, 84-93.

[5] Plimpton, P.E., H.P. Freitag, and M.J. McPhaden, 1995: Correcting moored ADCP data for fish-bias errors at 0°,110°W and 0°,140°W from 1990 to 1993. NOAA Tech. Memo. ERL PMEL-107, 49 pp.

[6] 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.

[7] Freitag, H.P., M. O'Haleck, G.C. Thomas, and M.J. McPhaden, 2001: Calibration procedures and instrumental accuracies for ATLAS wind measurements. NOAA. Tech. Memo. OAR PMEL-119, NOAA/Pacific Marine Environmental Laboratory, Seattle, Washington, 20 pp.

Footnote: This study discovered a systematic error in standard and NextGeneration ATLAS wind directions of approximately 6.8° in the counterclockwise direction. This error was present possibly as far back as 1984. Modifications were made to the NextGeneration ATLAS system in 2000 to correct this error in subsequent deployments, and archived NextGeneration ATLAS wind directions were corrected (both daily averages and high resolution datasets) on 28 March 2002. See /tao/proj_over/vane_correct.html. Standard ATLAS wind directions have not been corrected in the archives since the exact time when the error began to affect the measurements is unknown. Standard ATLAS were used exclusively between 1984 and 1996 when NextGeneration ATLAS moorings began to replace them. By November 2001, the standard ATLAS had been phased out and the array was comprised entirely of NextGeneration systems. Expected RMS error for standard ATLAS wind direction is 7.8° (of which 6.8° is a bias) while expected RMS error for NextGeneration ATLAS wind directions is about ±5° with no appreciable bias.

[8] McCarty, M.E., and M.J. McPhaden, 1993: Mean seasonal cycles and interannual variations at 0, 165E during 1986-1992. NOAA Tech. Memo. ERL PMEL-98, 64pp.

[9] A'Hearn, P.N., H.P. Freitag, and M.J. McPhaden, 2002: ATLAS module temperature bias due to solar heating. NOAA Tech. Memo OAR PMEL-121, NOAA/Pacific Marine Environmental Laboratory, Seattle, WA, 24 pp.

[10] Freitag, H.P., M.J. McPhaden, C.Meinig, and P.Plimpton, 2003: Mooring motion bias of point Doppler current meter measurements. In: Proceedings of the IEEE Seventh Working Conference on Current Measurement Technology, San Diego, CA, 13-15 March 2003, IEEE, Piscataway, NJ, 155-160.

[11] Plimpton, P.E., H.P. Freitag, and M.J. McPhaden, 2004: Processing of subsurface ADCP data in the equatorial Pacific. NOAA Tech. Memo OAR PMEL-125, NOAA/Pacific Marine Environmental Laboratory, Seattle, WA. 41pp.

[12] Lake, B.J., S.M. Noor, H.P. Freitag, and M.J. McPhaden, 2003: Calibration procedures and instrumental accuracy estimates of ATLAS air temperature and relative humidity measurements. NOAA Tech. Memo. OAR PMEL-123, NOAA/Pacific Marine Environmental Laboratory, Seattle, WA, 23 pp.

[13] Payne, R.E., K. Huang, R.A. Weller, H.P. Freitag, M.F. Cronin, M.J. McPhaden, C. Meinig, Y. Kuroda, N. Ushijima, R.M. Reynolds, 2002: A comparison of buoy meteorological systems. WHOI Technical Report
WHOI-2002-10. Woods Hole Oceanographic Institution, 67 pp.

[14] Freitag, H.P., T.A. Sawatzky, K.B. Ronnholm, and M.J. McPhaden, 2005: Calibration procedures and instrumental accuracy estimates of next generation ATLAS water temperature and pressure measurements. NOAA Tech. Memo. OAR PMEL-128, NTIS: PB2008-101764, NOAA/Pacific Marine Environmental Laboratory, Seattle, WA, 22 pp.

[15] Cronin, M.F. and M.J. McPhaden, 1997: The upper ocean heat balance in the western equatorial Pacific warm pool during September-December 1992. J. Geophys. Res., 102, 8533-8553.

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