Field Evaluation Of Real-Time XBT Systems

Wright, David J.; Szabados, M.

doi:10.1109/oceans.1989.587130

Cited by 6 publications

(4 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…To assess the potential impact of the XBT measurement errors on weekly to interannual estimates, a comparison is performed on the magnitude of the generated MOC and MHT errors with respect to the natural variability of these quantities. To accomplish this, we generate the XBT error parameters drawn from uniform distributions bounded by the manufacturer's tolerance for the measurement error values [ Wright and Szabados , ]. Thus, the measurement errors are randomly generated using the following range for the parameter settings: Z 0 = ±5 m, Z 1 = ±2% of depth, and T 0 = ± 0.15°C.…”

Section: Resultsmentioning

confidence: 99%

“…FRE errors, stated by the manufacturer as ±5 m or 2% of depth, whichever is greater, generate the largest uncertainty in XBT temperature measurements. In addition, temperature accuracy from XBT thermistors suffers from the influence of several factors, such as wire resistance imbalance, time response to thermal gradients, and static bath calibrations (see Reseghetti et al [2007] for a comprehensive analysis of error sources affecting XBT data accuracy), which produce an accuracy of ±0.15°C [e.g., Wright and Szabados, 1989] in comparison to ±0.001°C for conductivity-temperature-depth (CTD) stations or ±0.005°C for Argo profiling floats. XBT data are increasingly being used in climate research, in which much greater measurement accuracy is required.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The impact of historical biases on the XBT‐derived meridional overturning circulation estimates at 34°S

Góes

Baringer

Goñi

2015

Geophysical Research Letters

View full text Add to dashboard Cite

An observational system based on high-density expendable bathythermograph (XBT) data has provided the longest record of the South Atlantic meridional overturning and heat transport estimates across 34°S. Measurement biases are a point of concern for the capability of an XBT system to capture long-term trends in volume and heat transports, and the impact of such biases on the meridional overturning estimates has never been quantified. In the present study, the sensitivity of the meridional overturning circulation and heat transport to uncertainties in XBT measurements is quantified under the framework of an eddy-resolving model simulation. Results show that XBT measurement biases after 2010 can translate into small meridional overturning errors on the order of 3% or 0.38 Sv (1Sv = 10 6 m 3 s À1), and 0.025 PW (1 PW = 10 15 W) or 8% of the meridional heat transport in the model. Historical XBT-derived trends in transport estimates across 34°S are stronger and statistically significant after the late 1990s, 0.3 Sv decade À1 and 0.02 PW decade À1 . These trends are mostly due to the XBT linear depth bias, with smaller contributions associated with temperature and depth offsets from the historical record. Long-term trends calculated from Simple Ocean Data Assimilation reanalysis, estimated as 0.1 Sv/decade and 0.006 PW/decade, are 3 times smaller than the XBT-derived historical trends. Therefore, an adequate correction of historical XBT data is necessary for an early detection of trends in the meridional overturning circulation and heat transport.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The impact of historical biases on the XBT‐derived meridional overturning circulation estimates at 34°S

Góes

Baringer

Goñi

2015

Geophysical Research Letters

View full text Add to dashboard Cite

show abstract

“…These measurements were collected throughout the world oceans during 1900-92 using a variety of instruments, including expendable bathythermographs (XBT); conductivity, temperature, and depth profilers; salinity, temperature, and depth profilers; bathythermographs; and mechanical bathythermographs. Corrections of the depth error associated with the drop rate problem for several kinds of XBTs (Barnes and Sessions 1984;Hanawa and Yoritaka 1987;Wright and Szabados 1989;Singer 1990;Hallock and Teague 1992) are made at NODC. Levitus and Boyer (1994) checked the profiles for unreasonable ship speed between measurements, temperature or density inversion, data duplication, as well as other unrealistic features in comparison to the climatological field and its seasonal standard deviations.…”

Section: B Observational Datamentioning

confidence: 99%

Ocean Data Assimilation, Initialization, and Predictions of ENSO with a Coupled GCM

Schneider¹,

Huang²,

Zhu³

et al. 1999

Mon. Wea. Rev.

View full text Add to dashboard Cite

A scheme for making seasonal to interannual predictions of El Niño-Southern Oscillation with a coupled atmosphere-ocean general circulation model that incorporates subsurface ocean measurements in the initial conditions is described. Anomaly initial conditions are used in order to reduce initial shock and climate drift. The ocean component of the prediction model has a nearly global domain, and the coupled model does not employ anomaly coupling or empirical statistical corrections. Initial conditions for the ocean were obtained from a near-global ocean analysis produced by an ocean data assimilation system. The assimilation system uses a variationally formulated optimal interpolation method to analyze oceanic fields from temperature observations and a first-guess field provided by integrating a global ocean general circulation model. The period of the analysis was 1986 through 1992. The anomaly initial conditions for the ocean were generated by adding the anomalies of the assimilated fields from the assimilation climatology to the coupled model climatology. A series of 28 1-yr hindcast experiments, four each year for the years 1986-1992, was carried out to test the scheme. The hindcasts show considerable skill in the equatorial Pacific.

show abstract

“…In particular, that of the T-7 was most frequently reviewed because of their popularity (Flierl and Robinson, 1977;Federov et al, 1978;Seaver and Kuleshov, 1982;Heinmiller et al, 1983;Green, 1984;Hanawa and Yoritaka, 1987;Roemmich and Cornuelle, 1987;Wright and Szabados, 1989;Singer, 1990;Hanawa and Yoshikawa, 1991;Biggs, 1992;Hallock and Teague, 1992;Hanawa and Yasuda, 1992;Narayan and Lilly, 1993;Thadathil et al, 1998Thadathil et al, , 2002Reseghetti et al, 2007). Most studies prior to the mid-1990s concluded that the original fall-rate coefficients by the Sippican (a = 6.472 and b = 0.00216) had systematic bias that caused underestimation of depth.…”

Section: Introductionmentioning

confidence: 99%

Comparison of the fall rate and structure of recent T-7 XBT manufactured by Sippican and TSK

2011

View full text Add to dashboard Cite

Abstract. The fall rate of recent T-7 expendable bathythermograph (XBT; 760 m) is evaluated based on a series of concurrent measurement with a calibrated Conductivity Temperature Depth profiler (CTD) in the sea east of Japan. An emphasis is placed on comparing the fall rates of T-7 produced by the two present manufacturers, the Lockheed Martin Sippican Inc., and the Tsurumi Seiki Co. Ltd., which have been believed to be identical but had never been compared directly. It is found that the two manufacturers' T-7 fall at rates different by about 3.5%. The Sippican T-7 falls slower than given by the fall-rate equation (FRE) of Hanawa et al. (1995) by about 2.1%, and the TSK T-7 falls faster by about 1.4%. The fall-rate coefficients estimated based on the sea test by applying the equation of traditional quadratic form, d(t) = at −bt 2 where d is depth in meters and t is the time elapsed, in seconds, are a = 6.553 (m s −1 ) and b = 0.00221 (m s −2 ) for the LMS T-7, and a = 6.803 (m s −1 ) and b = 0.00242 (m s −2 ) for the TSK T-7. By detail examination of the probes, we found that the two companies' T-7 have different total weight and many structural differences. Because the difference in the fall rate is about twice larger than the difference in weight (about 2%), it is inferred that the structural differences give sizable impact to the difference in their fall rates. Our results clearly show that the recent T-7 of the two companies needs to be discriminated.

show abstract

Field Evaluation Of Real-Time XBT Systems

Cited by 6 publications

References 4 publications

The impact of historical biases on the XBT‐derived meridional overturning circulation estimates at 34°S

The impact of historical biases on the XBT‐derived meridional overturning circulation estimates at 34°S

Ocean Data Assimilation, Initialization, and Predictions of ENSO with a Coupled GCM

Comparison of the fall rate and structure of recent T-7 XBT manufactured by Sippican and TSK

Contact Info

Product

Resources

About