Scavenging of radioactive soluble gases from inhomogeneous atmosphere by evaporating rain droplets.

We analyze effects of inhomogeneous concentration and temperature distributions in the atmosphere, rain droplet evaporation and radioactive decay of soluble gases on the rate of trace gas scavenging by rain. We employ a one-dimensional model of precipitation scavenging of radioactive soluble gaseous pollutants that is valid for small gradients and non-uniform initial altitudinal distributions of temperature and concentration in the atmosphere. We assume that conditions of equilibrium evaporation of rain droplets are fulfilled.

Large-scale instability in a sheared nonhelical turbulence: Formation of vortical structures.

We study a large-scale instability in a sheared nonhelical turbulence that causes generation of large-scale vorticity. Three types of the background large-scale flows are considered, i.e.

Excitation of large-scale inertial waves in a rotating inhomogeneous turbulence.

A mechanism of excitation of the large-scale inertial waves in a rotating inhomogeneous turbulence due to an excitation of a large-scale instability is found. This instability is caused by a combined effect of the inhomogeneity of the turbulence and the uniform mean rotation. The source of the large-scale instability is the energy of the small-scale turbulence.

Generation of large-scale vorticity in a homogeneous turbulence with a mean velocity shear.

An effect of a mean velocity shear on a turbulence and on the effective force which is determined by the gradient of the Reynolds stresses is studied. Generation of a mean vorticity in a homogeneous incompressible nonhelical turbulent flow with an imposed mean velocity shear due to an excitation of a large-scale instability is found. The instability is caused by a combined effect of the large-scale shear motions ("skew-induced" deflection of equilibrium mean vorticity) and "Reynolds stress-induced" generation of perturbations of mean vorticity.

Formation of large-scale semiorganized structures in turbulent convection.

A new mean-field theory of turbulent convection is developed by considering only the small-scale part of spectra as "turbulence" and the large-scale part, as a "mean flow," which includes both regular and semiorganized motions. The developed theory predicts the convective wind instability in a shear-free turbulent convection. This instability causes formation of large-scale semiorganized fluid motions in the form of cells.

Clustering instability of the spatial distribution of inertial particles in turbulent flows.

A theory of clustering of inertial particles advected by a turbulent velocity field caused by an instability of their spatial distribution is suggested. The reason for the clustering instability is a combined effect of the particles inertia and a finite correlation time of the velocity field. The crucial parameter for the clustering instability is the size of the particles.