Urban air quality is influenced by the removal of particulate matter through dry deposition, yet this process is often simplified in models, potentially underestimating the role of vertical building surfaces. This study investigates the impact of aerosol deposition on building walls on PM2.5 concentrations and the deposition budget within the urban canopy. We utilized a Large Eddy Simulation model coupled with a Lagrangian Particle Transport module to simulate aerosol dispersion in randomized urban configurations corresponding to Local Climate Zones (LCZs) 4, 5, and 6. The results indicate that under the considered conditions, vertical walls can act as a primary sink for PM2.5, capturing over 70% of deposited particles downwind from sources in high-rise environments. We observed a non-linear sensitivity of airborne concentrations to wall deposition efficiency; a relatively low capture probability (10%) reduced near-surface concentrations by 25-30%. Furthermore, for fine and coarse particles (up to similar to 20 mu m), the uncertainty in wall deposition parameterization appeared to outweigh the influence of particle physical properties on dispersion patterns. These findings suggest that neglecting wall deposition may lead to overestimation of urban pollution levels, highlighting the importance of refining particle-wall interaction parameterizations in air quality models.

Using large eddy simulations (LES), we investigated the flow dynamics in the vegetated urban canopy layer (UCL). A LES model was used in which large objects (buildings) were explicitly specified as solid walls and vegetation (trees) was modeled by introducing additional volumetric drag in momentum equations. Simplified urban canopy geometries with relatively low plan area density were used. We analyzed influence of the foliage drag on the form drag from the buildings, the turbulent length scales and the kinetic energy balances. A new approach for calculating form drag in the presence of vegetation in UCL is proposed.

As urban areas grow, understanding the impact of built environments on aerosol distribution is crucial for accurate monitoring and forecasting of urban air quality and for development of mitigation strategies. In this study we use a modern approach, which combines micro-scale Large Eddy Simulation with Local Climate Zones (LCZ) classification to simulate the transport of Lagrangian aerosol particles in different urban configurations. The study simulates several urban configurations based on LCZ classification, specifically open LCZ types, varying in building height and aspect ratio: LCZ 4 (high-rise), LCZ 5 (mid-rise), LCZ 6 (low-rise). Both regular and randomized urban development configurations were examined to understand the impact of building geometry on particle dispersion. The transport of particulate matter emitted from a linear source within a street canyon has been simulated under neutral atmospheric conditions.The study reveals that the orientation of buildings significantly influences the distribution of particles. Structures parallel to the wind add horizontal dispersion, while those perpendicular promote vertical mixing. Variations in particle concentrations in randomized configurations highlight the role of architectural heterogeneity in turbulence development and aerosol dispersion. In the absence of regular homogeneous structures, the aggregated block- and district-scale geometry of buildings strongly influences aerosol transport. In randomized urban configurations, the large-scale morphological characteristics of different LCZ types have a significantly greater effect on particle dispersion than the local geometrical differences between configurations within the same LCZ.Future research is recommended to take into account diverse meteorological conditions and a wider range of LCZ types to enhance the accuracy and applicability of this approach.The work is supported by RSF grant 24-17-00155.

An Erratum to this paper has been published: https://doi.org/10.1134/S1052618824010151

Urban canopy models (UCMs) are widely used to parameterize surface-atmosphere interaction in weather and climate models. The physical processes described by UCMs include turbulent exchange and wind patterns within the urban canopy. This study compares several parameterizations of the vertical mean wind profile used in UCMs against simulations of the turbulent flow over an inhomogeneous urban-like surfaces with direct numerical simulation (DNS) model. The configurations of urban surface morphology are considered in a simplified form (columns, rows, and blocks) with different height, frontal area index and aspect ratio. The possibility of applying the considered approaches to wind profile parameterizations in single-layer urban canopy models are discussed. Evaluation showed that parameterizations which utilize more accurate turbulent length scales’ description and explicitly involve buildings density metrics are shown to be applicable for a wider range of urban canopy geometries.

The dissipation rates of the basic second-order moments are the key parameters playing a vital role in turbulence modelling and controlling turbulence energetics and spectra and turbulent fluxes of momentum and heat. In this paper, we use the results of direct numerical simulations (DNSs) to evaluate dissipation rates of the basic second-order moments and revise the energy and flux budget (EFB) turbulence closure theory for stably stratified turbulence. We delve into the theoretical implications of this approach and substantiate our closure hypotheses through DNS data. We also show why the concept of down-gradient turbulent transport becomes incomplete when applied to the vertical turbulent flux of potential temperature under stable stratification. We reveal essential feedback between the turbulent kinetic energy (TKE), the vertical turbulent flux of buoyancy, and the turbulent potential energy (TPE), which is responsible for maintaining shear-produced stably stratified turbulence for any Richardson number.

An Erratum to this paper has been published: https://doi.org/10.1134/S1052618824010151

The paper reviews the planetary boundary layer parameterizations in the current generation of the INMCM Earth system model. We discuss some of the challenges and improvements necessary to correctly reproduce the essential non-linear interactions of physical processes common to the boundary-layer physics. Overview of some of the improvements implemented in the PBL single-column version of the INMCM model is presented. These include the hierarchy of turbulence closures of different computational complexity suited for modelling a thin stable boundary layer. The closures are based on a consistent definition of the first-order, single- and two-equation approaches and inclusion of stability functions in the surface layer parameterizations tailored for strong static stability of the atmosphere.

In this work, new devices and tools for minimally invasive endoscopic surgery are considered, which were developed by Mechanical Engineering Research Institute of the Russian Academy of Sciences, together with the Central Clinical Hospital, Russian Academy of Sciences. Experimental samples of the devices and tools are presented.

Large-eddy simulations (LES) of neutrally and stably stratified turbulent flows over urban-type surfaces with relatively low plan area ratios are presented. Numerical experiments were performed for different shapes of streamlined objects and at different static stability. A new method for setting up a numerical experiment aimed at studying the heat and momentum transfer within the roughness layer and investigating the thermal and dynamic interaction between the turbulent flow and the surface as a whole has been proposed. This method enables us to obtain an equilibrium state for values of parameters determining the characteristics of the external turbulent flow chosen beforehand. A strong dependence of the thermal roughness length on stratification was found. We also discuss the physical mechanisms that lead to the maintenance of turbulence above the canopy when the ground surface is strongly cooled. Significance StatementUsing LES, we identify a mechanism that contributes to the maintenance of turbulence in the atmospheric boundary layer under the condition of strong surface cooling. Although these results are obtained for an urban canopy, we believe that the qualitative conclusions should be general for a wide type of surfaces with large-scale roughness elements. We hope that the new results will be useful for improving surface flux schemes in NWP and climate atmospheric models that suffer from attenuated mixing in a very stable boundary layer and the effect of "surface decoupling." The found effect gives a physically justified alternative way to parameterize the air-surface exchange under strong stability compared to the often ad hoc modification of the MOST universal functions.

This paper presents results of development of a numerical model of Lagrangian particle transport, as well as results of application of parallel computation methods to improve the efficiency of the software implementation of this model. The model is a software package that allows the transport and deposition of aerosol particles to be calculated taking into account properties of particles and the input data that describe atmospheric conditions and underlying surface geometry. The dynamic core, physical parameterizations, numerical implementation, and algorithm of the model are described. Results of successful verification of the model on analytical solutions are presented. Initially, the model was used for less computationally intensive problems. In this paper, given the need to use the model in more computationally intensive problems, we optimize the sequential software implementation of the model, as well as develop its software implementations that use parallel computing technologies (OpenMP, MPI, and CUDA). The results of testing different implementations of the model show that the optimization of the most computationally complex blocks in its sequential version can reduce the execution time by 27%. At the same time, the use of parallel computing technologies allows us to achieve acceleration by several orders of magnitude. The use of OpenMP in the dynamic block of the model provides almost 4-fold acceleration of this block; the use of MPI, almost 8-fold acceleration; and the use of CUDA, almost 16-fold acceleration (all other conditions being equal). We also give some recommendations on the choice of a parallel computing technology depending on the properties of a computing system.

A mechanism with a remote center of rotation, intended for use in medicine, and in particular, minimally invasive operations, is discussed. The basic mechanism consists of two parallelograms with common links, which allows the surgical instrument to duplicate the movement of the drive link of the mechanism. To ensure greater rigidity of the mechanism, it is proposed to introduce drive redundancy through the use of an additional RRR dyad with a drive pair. The position problem has been solved for the resulting mechanism. A 3D model and a prototype of the mechanism have been also presented.

Ocean models at intermediate resolution (1/4 degree), which partially resolve mesoscale eddies, can be seen as Large eddy simulations (LES) of the primitive equations, in which the effect of unresolved eddies must be parameterized. In this work, we propose new subgrid models that are consistent with the physics of two-dimensional (2D) flows. We analyze subgrid fluxes in barotropic decaying turbulence using Germano (1986) decomposition. We show that Leonard and Cross stresses are responsible for the enstrophy dissipation, while the Reynolds stress is responsible for additional kinetic energy backscatter. We utilize these findings to propose a new model, consisting of three parts, that is compared to a baseline dynamic Smagorinsky model (DSM). The three-component model accurately simulates the spectral transfer of energy and enstrophy and improves the representation of kinetic energy (KE) spectrum, resolved KE and enstrophy decay in a posteriori experiments. The backscattering component of the new model (Reynolds stress) is implemented both in quasi-geostrophic and primitive equation ocean models and improves statistical characteristics, such as the vertical profile of eddy kinetic energy, meridional overturning circulation and cascades of kinetic and potential energy.

In this study, we utilize a generalization of Monin–Obukhov similarity theory to construct first order turbulent closures for single-column models of the atmospheric boundary layer (ABL). A set of widely used universal functions for dimensionless gradients is evaluated. Two test cases based on Large-Eddy Simulations (LES) experimental setups are considered – weakly stable ABL (GABLS1; Beare et al. in Bound Layer Meteorol 118(2):247–272, 2006), and very strongly stratified ABL (van der Linden et al. in Bound Layer Meteorol 173(2):165–192, 2019). The comparison shows that approximations obtained using a linear dimensionless velocity gradient tend to match the LES data more closely. In particular, the EFB (Energy- and Flux- Budget) closure proposed by Zilitinkevich et al. (Bound Layer Meteorol 146(3):341–373, 2013) has the best performance for the tests considered here. We also test surface layer “bulk formulas” based on these universal functions. The same LES data are utilized for comparison. The setup showcases the behavior of surface scheme, when one assumes that the velocity and temperature profiles in ABL are represented correctly. The advantages and disadvantages of different surface schemes are revealed.

This paper is dedicated to the memory of Vasily Nikolaevich Lykosov, a prominent Russian scientist and a specialist in the field of mathematical modeling of the dynamics of the turbulent boundary layer and its interaction with large-scale atmospheric circulation, global and regional climatic processes, and the active layer of the land. His scientific activities are briefly described in the context of modern research, one characteristic feature of which is attention to the links between local and global physical phenomena and a combination of theoretical models and numerical experiments.

Locally one-dimensional ABL model of the moderately stable and highly stable boundary layer of the atmosphere were evaluated with the data obtained from numerical experiments with eddy-resolving turbulence models. It is shown that the best results are obtained by parametrizations which maintain turbulence at large gradient Richardson numbers. These parametrizations of turbulent diffusion for stable stratification were introduced into the INM RAS Earth System model [1]. Based on a comparison with the reanalysis data, it is shown that an improved model of turbulence in the boundary layer reduces the average error in reproducing the current climate in high latitudes. Authors want to acknowledge partial funding by Russian Foundation for Basic Research (RFBR project 20-05-00776) and support from Russian Science Foundation (RSF grant 20-17-00190). 1. Volodin, E. M., et al. "Simulation of the present-day climate with the climate model INMCM5." Climate dynamics 49.11 (2017): 3715-3734.

Optimal disturbances of a turbulent stably stratified plane Couette flow in a wide range of Reynolds and Richardson numbers are studied. These disturbances are computed based on a simplified system of equations in which turbulent Reynolds stresses and heat fluxes are approximated by isotropic viscosity and diffusivity with the coefficients obtained from results of direct numerical simulation. Three types of disturbances are considered: large-scale streamwise-elongated rolls converting into streamwise streaks; large-scale vortical structures, inclined in the vertical plane, changing the inclination to the opposite in process of their evolution; near-wall rolls converting into streaks. Large-scale rolls and streaks predominate at neutral or weakly stable stratification while the inclined structures begin to dominate at moderately stable stratification. Near-wall rolls and streaks appear at any stratification and their spanwise size in wall length units does not depend on the values of Reynolds and Richardson numbers. It is shown that the development of inclined optimal disturbances is due to the coupled action of the lift-up effect and the inviscid Orr mechanism. The energetics of the optimal disturbances is discussed. It is shown that inclined optimal disturbances dissipate rapidly after reaching maximum energy amplification.

This study presents the results of large-eddy simulation (LES) of the evening transition in the atmospheric boundary layer in the case of free convection and in the presence of geostrophic wind. The turbulent kinetic energy (TKE) balance and its components are analyzed. It is shown that within the transition, periods of fast and slow decay can be distinguished. The differences in TKE anisotropy between these two periods are demonstrated. During the fast decay period, the majority of the energy within the vertical component is consumed due to inertial movement of the thermals after the cease of convection. This is followed by the TKE redistribution into large-scale horizontal components, which leads to the formation of quasi-horizontal turbulence, where the TKE dissipation is significantly slower in comparison to the isotropic state. It is shown that one-dimensional boundary-layer model, in which turbulent fluxes are parameterized by means of a two-equation closure, is not able to reproduce evening transition dynamics observed in LES. In particular, the use of the gradient approximation in the one-dimensional model leads to the preservation of the convective distribution of the heat flux along the vertical during the transition period and additional TKE generation in the boundary layer due to the action of buoyancy forces. The use of the phenomenological equation for the dissipation rate leads to decreased TKE decay rate during the fast decay period and increased TKE decay rate during the slow decay period. Possible approaches toward modification of the Reynolds-averaged Navier–Stokes (RANS) closures in order to correctly reproduce transition periods of the atmospheric boundary layer are discussed.

The current state of robotic-assisted complexes in minimally invasive surgery is considered. Three different manipulators for robotic surgery, which differ from well-known foreign analogues in a number of advantages, as well as a setting device, have been proposed. The prototypes of robots, the solution of the inverse problem of positions, and the problems of dynamics have been given. It has been proposed to use DC electric motors as drives.