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1

“Noise” in climatologically driven ocean models with different grid resolution

Tang Shengquan, von Storch Hans, Chen Xueen, Zhang Meng

Oceanologia

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2019

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No. 61 (3)

300--307

EN

The internally generated variability in the climate system, which is unrelated to any external factors, can be conceptualized as “noise”. This noise is a constitutive element of high-dimensional nonlinear models of such systems. In a three-layer nested simulation, which is forced by climatological (periodic) atmospheric forcing and includes an (almost) global model, a West-Pacific model, and South China Sea (SCS) model, we demonstrate that such “noise” builds also ocean models. They generate variability by themselves without an external forcing. The “noise” generation intensifies with higher resolution, which favors macroturbulence.

2

Sensitivity of optimized transient storage model parameters to spatial and temporal resolution

Wallis Steve, Manson Russell

Acta Geophysica

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2019

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Vol. 67, no. 3

951--960

EN

The transient storage model is a popular tool for modelling solute transport along rivers. Its use requires values for the velocity and shear flow dispersion coefficient in the main channel of the river together with two exchange rates between the main channel and transient storage zones, which surround the main channel. Currently, there is insufficient knowledge to enable these parameters to be predicted from the type of hydraulic variables that may typically be available. Hence, recourse is made to tracer experiments, which provide temporal solute concentration profiles that can be used to estimate the parameters by optimizing model output to observations. The paper explores the sensitivity of such parameters to the spatial and temporal resolutions used in the optimization of the model. Data from 25 tracer experiments covering a river flow rate range of 300–2250 L/s in a single reach of the river Brock in north-west England were used. The shear flow dispersion coefficient was found to be the most sensitive parameter; the velocity was found to be the least sensitive parameter. When averaged over all the experiments, mean percentage differences in parameter values between a coarse resolution case and a fine resolution case were of the order of 2% for the velocity, 70% for the shear flow dispersion coefficient and 30% and 20% for the two exchange rates. Since the shear flow dispersion coefficient was found to be small, both in numerical terms and in comparison with an estimate of the total dispersion in the reach, it is suggested that it may be viable to omit the shear flow dispersion term from the model.

3

Dynamical downscaling approach for wintertime seasonal-scale simulation over the Western Himalayas

Tiwari P., Kar S., Mohanty U., Dey S., Sinha P., Raju P., Shekhar M.

Acta Geophysica

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2014

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Vol. 62, no. 4

930--952

EN

The performance of RegCM4 for seasonal-scale simulation of winter circulation and associated precipitation over the Western Himalayas (WH) is examined. The model simulates the circulation features and precipitation in three distinct precipitation years reasonably well. It is found that the RMSE decreases and correlation coefficient increases in the precipitation simulations with the increase of model horizontal resolutions. The ETS and POD for the simulated precipitation also indicate that the performance of model is better at 30 km resolution than at 60 and 90 km resolutions. This improvement comes due to better representation of orography in the high-resolution model in which sharp orography gradient in the domain plays an important role in wintertime precipitation processes. A comparison of model-simulated precipitation with observed precipitation at 17 station locations has been carried out. Overall, the results suggest that 30 km model produced better skill in simulating the precipitation over the WH and this model is a useful tool for further regional downscaling studies.

4

Measurements using three-dimensional product imaging

Sioma A.

Archives of Foundry Engineering

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2010

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Vol. 10, iss. 3 spec.

41--46

EN

This article discusses a method of creating a three-dimensional cast model using vision systems and how that model can be used in the quality assessment process carried out directly on the assembly line. The technology of active vision, consisting in illumination of the object with a laser beam, was used to create the model. Appropriate configuration of camera position geometry and laser light allows the collection of height profiles and construction of a 3D model of the product on their basis. The article discusses problems connected with the resolution of the vision system, resolution of the laser beam analysis, and resolution connected with the application of the successive height profiles on sample cast planes. On the basis of the model, measurements allowing assessment of dimension parameters and surface defects of a given cast are presented. On the basis of tests and analyses of such a three-dimensional cast model, a range of checks which are possible to conduct using 3D vision systems is indicated. Testing casts using that technology allows rapid assessment of selected parameters. Construction of the product’s model and dimensional assessment take a few seconds, which significantly reduces the duration of checks in the technological process. Depending on the product, a few checks may be carried out simultaneously on the product’s model. The possibility of controlling all outgoing products, and creating and modifying the product parameter control program, makes the solution highly flexible, which is confirmed by pilot industrial implementations. The technology will be developed in terms of detection and identification of surface defects. It is important due to the possibility of using such information for the purposes of selecting technological process parameters and observing the effect of changes in selected parameters on the cast parameter controlled in a vision system.