Applying Automated Underway Ship Observations to Numerical Model Evaluation

2016 ◽  
Vol 33 (3) ◽  
pp. 409-428 ◽  
Author(s):  
Shawn R. Smith ◽  
Kristen Briggs ◽  
Nicolas Lopez ◽  
Vassiliki Kourafalou
Keyword(s):  
Numerical Model ◽  
Model Evaluation ◽  
Numerical Models ◽  
Sampling Rate ◽  
Ocean Model ◽  
Near Surface ◽  
Atmospheric Sciences ◽  
High Sampling Rate ◽  
In Situ Observations

AbstractNumerical models are used widely in the oceanic and atmospheric sciences to estimate and forecast conditions in the marine environment. Herein the application of in situ observations collected by automated instrumentation on ships at sampling rates ≤5 min is demonstrated as a means to evaluate numerical model analyses. Specific case studies use near-surface ocean observations collected by a merchant vessel, an ocean racing yacht, and select research vessels to evaluate various ocean analyses from the Hybrid Coordinate Ocean Model (HYCOM). Although some specific differences are identified between the observations and numerical model analyses, the purpose of these comparisons is to demonstrate the value of high-sampling-rate in situ observations collected on ships for numerical model evaluation.

scholarly journals High sampling rate thermistor string observations at the slope of Great Meteor Seamount

Ocean Science ◽  
2005 ◽  
Vol 1 (1) ◽  
pp. 17-28 ◽  
Author(s):  
H. van Haren ◽  
R. Groenewegen ◽  
M. Laan ◽  
B. Koster
Keyword(s):  
High Frequency ◽  
North Atlantic Ocean ◽  
Sampling Rate ◽  
Very High Frequency ◽  
High Sampling ◽  
High Sampling Rate ◽  
In Situ Calibration ◽  
Great Meteor Seamount ◽  
Very High

Abstract. A high sampling rate (1 Hz) thermistor string has been built to accommodate the scientific need to accurately monitor high-frequency and vigorous internal wave and overturning processes in the ocean. The thermistors and their custom designed electronics can register temperature at an estimated precision of about 0.001° C with a response time faster than 0.25 s down to depths of 6000 m. With a quick in situ calibration using SBE 911 CTD an absolute accuracy of 0.005° C is obtained. The present string holds 128 sensors at 0.5 m intervals, which are all read-out within 0.5 s. When sampling at 1 Hz, the batteries and the memory capacity of the recorder allow for deployments of up to 2 weeks. In this paper, the instrument is described in some detail. Its performance is illustrated with examples from the first moored observations, which show Kelvin-Helmholtz overturning and very high-frequency (Doppler-shifted) internal waves besides occasionally large turbulent bores moving up the sloping side of Great Meteor Seamount, Canary Basin, North-Atlantic Ocean.

scholarly journals The impact of near-surface soil moisture assimilation at subseasonal, seasonal, and inter-annual timescales

2015 ◽  
Vol 19 (12) ◽  
pp. 4831-4844 ◽  
Author(s):  
C. Draper ◽  
R. Reichle
Keyword(s):  
Soil Moisture ◽  
Data Assimilation ◽  
Surface Soil ◽  
Root Zone ◽  
Surface Model ◽  
Surface Soil Moisture ◽  
Near Surface ◽  
In Situ Observations ◽  
The Impact

Abstract. A 9 year record of Advanced Microwave Scanning Radiometer – Earth Observing System (AMSR-E) soil moisture retrievals are assimilated into the Catchment land surface model at four locations in the US. The assimilation is evaluated using the unbiased mean square error (ubMSE) relative to watershed-scale in situ observations, with the ubMSE separated into contributions from the subseasonal (SMshort), mean seasonal (SMseas), and inter-annual (SMlong) soil moisture dynamics. For near-surface soil moisture, the average ubMSE for Catchment without assimilation was (1.8 × 10−3 m3 m−3)2, of which 19 % was in SMlong, 26 % in SMseas, and 55 % in SMshort. The AMSR-E assimilation significantly reduced the total ubMSE at every site, with an average reduction of 33 %. Of this ubMSE reduction, 37 % occurred in SMlong, 24 % in SMseas, and 38 % in SMshort. For root-zone soil moisture, in situ observations were available at one site only, and the near-surface and root-zone results were very similar at this site. These results suggest that, in addition to the well-reported improvements in SMshort, assimilating a sufficiently long soil moisture data record can also improve the model representation of important long-term events, such as droughts. The improved agreement between the modeled and in situ SMseas is harder to interpret, given that mean seasonal cycle errors are systematic, and systematic errors are not typically targeted by (bias-blind) data assimilation. Finally, the use of 1-year subsets of the AMSR-E and Catchment soil moisture for estimating the observation-bias correction (rescaling) parameters is investigated. It is concluded that when only 1 year of data are available, the associated uncertainty in the rescaling parameters should not greatly reduce the average benefit gained from data assimilation, although locally and in extreme years there is a risk of increased errors.

scholarly journals Investigating tool engagement in groundwood pulping: finite element modelling and in-situ observations at the microscale

Holzforschung ◽  
2020 ◽  
Vol 74 (5) ◽  
pp. 477-487 ◽  
Author(s):  
Jenny Carlsson ◽  
Magnus Heldin ◽  
Per Isaksson ◽  
Urban Wiklund
Keyword(s):  
Finite Element ◽  
Numerical Models ◽  
X Ray ◽  
Tool Geometries ◽  
Commercial Use ◽  
X Ray Computed ◽  
In Situ Observations ◽  
Underlying Mechanisms

AbstractWith industrial groundwood pulping processes relying on carefully designed grit surfaces being developed for commercial use, it is increasingly important to understand the mechanisms occurring in the contact between wood and tool. We present a methodology to experimentally and numerically analyse the effect of different tool geometries on the groundwood pulping defibration process. Using a combination of high-resolution experimental and numerical methods, including finite element (FE) models, digital volume correlation (DVC) of synchrotron radiation-based X-ray computed tomography (CT) of initial grinding and lab-scale grinding experiments, this paper aims to study such mechanisms. Three different asperity geometries were studied in FE simulations and in grinding of wood from Norway spruce. We found a good correlation between strains obtained from FE models and strains calculated using DVC from stacks of CT images of initial grinding. We also correlate the strains obtained from numerical models to the integrity of the separated fibres in lab-scale grinding experiments. In conclusion, we found that, by modifying the asperity geometries, it is, to some extent, possible to control the underlying mechanisms, enabling development of better tools in terms of efficiency, quality of the fibres and stability of the groundwood pulping process.

scholarly journals A Novel Capacitance-Based In-Situ Pressure Sensor for Wearable Compression Garments

Micromachines ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 743
Author(s):  
Steven Lao ◽  
Hamza Edher ◽  
Utkarsh Saini ◽  
Jeffrey Sixt ◽  
Armaghan Salehian
Keyword(s):  
Pressure Sensor ◽  
Sampling Rate ◽  
Pressure Sensors ◽  
Average Error ◽  
Compression Garments ◽  
High Sampling Rate ◽  
Measurement Surface ◽  
Static Conditions ◽  
Static Form

This paper pertains to the development & evaluation of a dielectric electroactive polymer-based tactile pressure sensor and its circuitry. The evaluations conceived target the sensor’s use case as an in-situ measurement device assessing load conditions imposed by compression garments in either static form or dynamic pulsations. Several testing protocols are described to evaluate and characterize the sensor’s effectiveness for static and dynamic response such as repeatability, linearity, dynamic effectiveness, hysteresis effects of the sensor under static conditions, sensitivity to measurement surface curvature and temperature and humidity effects. Compared to pneumatic sensors in similar physiological applications, this sensor presents several significant advantages including better spatial resolution, compact packaging, manufacturability for smaller footprints and overall simplicity for use in array configurations. The sampling rates and sensitivity are also less prone to variability compared to pneumatic pressure sensors. The presented sensor has a high sampling rate of 285 Hz that can further assist with the physiological applications targeted for improved cardiac performance. An average error of ± 5.0 mmHg with a frequency of 1–2 Hz over a range of 0 to 120 mmHg was achieved when tested cyclically.

scholarly journals Lagrangian Perspective on the Origins of Denmark Strait Overflow

2020 ◽  
Vol 50 (8) ◽  
pp. 2393-2414
Author(s):  
Atousa Saberi ◽  
Thomas W. N. Haine ◽  
Renske Gelderloos ◽  
M. Femke de Jong ◽  
Heather Furey ◽  
...  
Keyword(s):  
North Atlantic ◽  
Meridional Overturning Circulation ◽  
Near Surface ◽  
The North ◽  
East Greenland Current ◽  
Nao Index ◽  
Denmark Strait ◽  
Meridional Overturning ◽  
In Situ Observations

AbstractThe Denmark Strait Overflow (DSO) is an important contributor to the lower limb of the Atlantic meridional overturning circulation (AMOC). Determining DSO formation and its pathways is not only important for local oceanography but also critical to estimating the state and variability of the AMOC. Despite prior attempts to understand the DSO sources, its upstream pathways and circulation remain uncertain due to short-term (3–5 days) variability. This makes it challenging to study the DSO from observations. Given this complexity, this study maps the upstream pathways and along-pathway changes in its water properties, using Lagrangian backtracking of the DSO sources in a realistic numerical ocean simulation. The Lagrangian pathways confirm that several branches contribute to the DSO from the north such as the East Greenland Current (EGC), the separated EGC (sEGC), and the North Icelandic Jet (NIJ). Moreover, the model results reveal additional pathways from south of Iceland, which supplied over 16% of the DSO annually and over 25% of the DSO during winter of 2008, when the NAO index was positive. The southern contribution is about 34% by the end of March. The southern pathways mark a more direct route from the near-surface subpolar North Atlantic to the North Atlantic Deep Water (NADW), and needs to be explored further, with in situ observations.

Observations of the Tasman Sea Internal Tide Beam

2018 ◽  
Vol 48 (6) ◽  
pp. 1283-1297 ◽  
Author(s):  
Amy F. Waterhouse ◽  
Samuel M. Kelly ◽  
Zhongxiang Zhao ◽  
Jennifer A. MacKinnon ◽  
Jonathan D. Nash ◽  
...  
Keyword(s):  
Plane Wave ◽  
Energy Flux ◽  
Internal Tide ◽  
Surface Displacement ◽  
Internal Tides ◽  
Near Surface ◽  
Tasman Sea ◽  
Stationary Energy ◽  
In Situ Observations

AbstractLow-mode internal tides, a dominant part of the internal wave spectrum, carry energy over large distances, yet the ultimate fate of this energy is unknown. Internal tides in the Tasman Sea are generated at Macquarie Ridge, south of New Zealand, and propagate northwest as a focused beam before impinging on the Tasmanian continental slope. In situ observations from the Tasman Sea capture synoptic measurements of the incident semidiurnal mode-1 internal-tide, which has an observed wavelength of 183 km and surface displacement of approximately 1 cm. Plane-wave fits to in situ and altimetric estimates of surface displacement agree to within a measurement uncertainty of 0.3 cm, which is the same order of magnitude as the nonstationary (not phase locked) mode-1 tide observed over a 40-day mooring deployment. Stationary energy flux, estimated from a plane-wave fit to the in situ observations, is directed toward Tasmania with a magnitude of 3.4 ± 1.4 kW m−1, consistent with a satellite estimate of 3.9 ± 2.2 kW m−1. Approximately 90% of the time-mean energy flux is due to the stationary tide. However, nonstationary velocity and pressure, which are typically 1/4 the amplitude of the stationary components, sometimes lead to instantaneous energy fluxes that are double or half of the stationary energy flux, overwhelming any spring–neap variability. Despite strong winds and intermittent near-inertial currents, the parameterized turbulent-kinetic-energy dissipation rate is small (i.e., 10−10 W kg−1) below the near surface and observations of mode-1 internal tide energy-flux convergence are indistinguishable from zero (i.e., the confidence intervals include zero), indicating little decay of the mode-1 internal tide within the Tasman Sea.

scholarly journals Sensitivity of Subsurface Ocean Temperature Variability to Specification of Surface Observations in the Context of ENSO

2017 ◽  
Vol 145 (4) ◽  
pp. 1437-1446 ◽  
Author(s):  
Arun Kumar ◽  
Caihong Wen ◽  
Yan Xue ◽  
Hui Wang
Keyword(s):  
Southern Oscillation ◽  
Numerical Models ◽  
Surface Wind ◽  
Ocean Model ◽  
Ocean Temperature ◽  
Subsurface Ocean ◽  
Atmospheric Forcings ◽  
Ocean Measurements

Abstract To estimate the state of the ocean in the context of monitoring and prediction, ocean analysis products combine observed information from various sources that include both in situ ocean measurements and estimates of atmospheric forcings derived either from numerical models or from objective analysis methods. In the context of El Niño–Southern Oscillation (ENSO) variability in the equatorial tropical Pacific, this study discusses two questions: 1) the role of surface forcings in resolving the observed variability of subsurface ocean temperatures, and 2) which component of surface forcings plays a more important role. The analysis approach is based on ocean model simulations where specification of surface forcings is controlled and the resulting ocean state is either compared among various simulations or is compared with an independent ocean analysis (where information from in situ ocean temperature measurements is included). The results highlight the importance of the contribution of observed sea surface temperature (via its influence on surface winds due to coupled air–sea interactions) and the observed surface wind forcing in determining the evolution of subsurface ocean temperatures. Implications for assessing the feasibility of extending ocean analysis and forecasts back in time when in situ observations were limited are also discussed.

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