A variational multiscale method with multifractal subgrid-scale modeling is proposed for large-eddy simulation of turbulent flow. In the multifractal subgrid-scale modeling approach, the subgrid-scale velocity is evaluated from a multifractal description of the subgrid-scale vorticity, which is based on the multifractal scale similarity of gradient fields in turbulent flow. The multifractal sub...

This paper presents the main results of a recent publication (Kwasniok, 2011a). A new approach for data-based stochastic parametrisation of unresolved scales and processes in numerical weather and climate prediction models is introduced. The subgrid-scale model is conditional on the state of the resolved scales, consisting of a collection of local models. A clustering algorithm in the space of ...

Feedbacks between water use, biomass and infiltration capacity in semiarid ecosystems have been shown to lead to the spontaneous formation of vegetation patterns in a simple model. The formation of patterns permits the maintenance of larger overall biomass at low rainfall rates compared with homogeneous vegetation. This results in a bias of models run at larger scales neglecting subgrid-scale v...

This investigation questions the importance of inverse interscale energy fluxes, so-called backscatter, for modelling cascade in large-eddy simulations (LES) turbulent flows. The invariance filtered Navier–Stokes equations to divergence-preserving transformations subgrid-scale (SGS) stress tensor is exploited here explore alternative representations local SGS fluxes. Numerical optimisation proc...

A new approach for data-based stochastic parametrization of unresolved scales and processes in numerical weather and climate prediction models is introduced. The subgrid-scale model is conditional on the state of the resolved scales, consisting of a collection of local models. A clustering algorithm in the space of the resolved variables is combined with statistical modelling of the impact of t...

In many earth science problems, the scales of interest range from centimeters to kilometers. Computer power and time limitations prevent inclusion of all the fine-scale features in most models. However, upscaling methods allow creation of physically realistic and computationally feasible models. Instead of solving the problem completely on the fine scale, upscaling methods produce a coarse-scal...

The modeling of the atmospheric boundary layer during convective conditions has long been a major source of uncertainty in the numerical modeling of meteorological conditions and air quality. Much of the difficulty stems from the large range of turbulent scales that are effective in the convective boundary layer (CBL). Both small-scale turbulence that is subgrid in most mesoscale grid models an...

Modeling air pollutant transport and dispersion in urban environments is especially challenging due to complex ground topography. In this study, we describe a large eddy simulation (LES) tool including a new dynamic subgrid closure and boundary treatment to model urban dispersion problems. The numerical model is developed, validated, and extended to a realistic urban layout. In such application...