We study the long-time, large scale transport in a three-parameter family of isotropic, incompressible velocity fields with power-law spectra. Scaling law for transport is characterized by the scaling exponent q and the Hurst exponent H , as functions of the parameters. The parameter space is divided into regimes of scaling laws of different functional forms of the scaling exponent and the Hurs...

We have developed a high-precision code which solves the kinematic dynamo problem both for given rotation law and meridional flow in the case of a low eddy diffusivity of the order of 10 11 cm 2 /s known from the sunspot decay. All our models work with an α-effect which is positive (negative) in the northern (southern) hemisphere. It is concentrated in radial layers located either at the top or...

A set of experiments was carried out to determine what effects periphyton communities could have on near-bed hydraulic fields. We analysed velocity distribution, skewness and kurtosis coefficients, Reynolds stresses, relative turbulence intensity, coefficient of eddy diffusivity, velocity spectra, and turbulence scales at two flows with, and without, diatom-dominated periphyton on the bed. We f...

Abstract In numerical simulations of deep convection at kilometer-scale horizontal resolutions, in-cloud subgrid-scale (SGS) turbulence plays an important role in the transport heat, moisture, and other scalars. By coarse graining a 50 m high-resolution large-eddy simulation (LES) idealized supercell storm to grid spacings ranging from 250 4 km, SGS fluxes cloud, precipitating water contents ar...

Eddy covariance data collected over a horizontal surface on the largest ice body on Kilimanjaro, Tanzania, over 26–29 July 2005 were used to assess the uncertainty of calculating sublimation with a surface energy balance (SEB) model. Data required for input to the SEB model were obtained from an existing automatic weather station. Surface temperatures that were solved iteratively by the SEB mod...

Cross-magnetic-field heat transport in a quiescent pure ion plasma is found to be diffusive and to be dominated by long-range collisions with impact parameters up to a Debye length. The measured thermal diffusivity x agrees within a factor of 2 with the long-range prediction xL ­ 0.49nȳb2l 2 D over a range of 103 in temperature, 50 in density, and 4 in magnetic field. This thermal diffusivity i...

We introduce a general purpose penetrator, fitted with a heater, for measuring temperature and thermal diffusivity. Due to its simplicity of deployment and operation the penetrator is well suited for remote deployment by spacecraft into a planetary regolith. Thermal measurements in planetary regoliths are required to determine the surface energy balance and to measure their thermal properties. ...

Understanding and improving the predictive skill of imperfect models for complex systems in their response to external forcing is a crucial issue in diverse applications such as for example climate change science. Equilibrium statistical fidelity of the imperfect model on suitable coarse-grained variables is a necessary but not sufficient condition for this predictive skill, and elementary exam...

We have developed a high-precision code which solves the kinematic dynamo problem both for given rotation law and meridional flow in the case of a low eddy diffusivity of the order of 10 11 cm 2 /s known from the sunspot decay. All our models work with an α-effect which is positive (negative) in the northern (southern) hemisphere. It is concentrated in radial layers located either at the top or...

We consider the passive scalar transport in an incompressible random flow. Our basic result is a proof of the converge of a certain numerical scheme for the computation of the eddy diffusivity tensor. The scheme leads to the formula for the diffusivity expressed in terms of an infinite series. We give a rigorous proof of the geometric bounds on the magnitude of the terms of the series, provided...