Mixing eddies

The pattern of eddy mixing in the mesosphere apparently may be highly nonisotropic, similar to that indicated for the lower thermosphere. The upper limit of vertical eddy diffusion coefficients for the mesosphere... 

The pattern and rate of exchange of stratospheric air with the mesosphere, with the troposphere, and between hemispheres is still poorly known. Within the stratosphere a complex pattern of eddy mixing and mean motions governs the redistribution of trace constituents. In the lower stratosphere the adsorption or attachment of trace constituents to natural sulfate particles influences their subsequent transport. Some main features in stratospheric transport processes based on tracer studies are reviewed here. 

It was pointed out above that the 18r W tracer observations, the excess 210Pb in the tropical stratosphere, and the radiochemical evidence from fallout samples collected by balloon can be reconciled with the slow mean motion of air upward across the equatorial tropopause and within the tropical stratosphere and outward toward higher latitudes at stratospheric levels up to about 35 km. Above 23 km. altitude, such mean motions poleward can explain the lack of significant equatorwards transport of fallout debris from Novaya Zemlya. In the stratosphere, below 23 km., meridional eddy mixing obscures the pattern of slow mean motions. However, even in this layer, little Soviet test debris mixes south of about 30 °N, suggesting that poleward mean motions restrict equator-wards transport by eddy mixing within the lower stratosphere between the equator and 30 °N. 

The tungsten tracer observations and the excess -1(,Pb in the tropical atmosphere are explained by the competing influence of sedimentation, slow mean motions, and eddy mixing. Radioactive aerosols in the lower stratosphere become attached to the natural sulfate particles which are of sufficient size and density to oppose upward transport to levels much above 20-25 km. (30). The coefficient of meridional eddy mixing appears to increase with latitude near the equator (29), with little seasonal change (33). At higher latitudes the rate of poleward transport exhibits large seasonal variations, with a maximum in winter (33). 

Not only may mass diffusion occur on a molecular basis, but also in turbulent-flow systems accelerated diffusion rates will occur as a result of the rapid-eddy mixing processes, just as these mixing processes created increased heat transfer and viscous action in turbulent flow. 

Grand Canaria Islands coastal eddies Mixed mesozooplankton 8 Hernandez-Leon et al. (2001)... 

In the absence of atmospheric motion and removal by precipitation, Be and Pb would remain where they originated—the upper troposphere and stratosphere and the lowermost meter of the atmosphere over continents and islands, respectively. In the real atmosphere, Be is mixed downward and Pb is mixed upwards and both are removed by precipitation. They are distributed through the atmosphere by eddy mixing. The residence time of aerosols is short compared to... 

The examples above illustrate the importance of understanding the transport and transformation of particulate matter in the ocean. Vertical transport processes are primarily considered when examining the fate of biogenic particles formed in surface waters. Lateral transport processes influence the dispersion into the ocean interior of particulate material eroded from continents. Much of this dispersion occurs by eddy mixing, but advection by ocean currents plays an important role in transport of marine particles as well. A complete understanding of the cycling of material within the oceans relies on an accurate knowledge of particle transport. 

Stull, R.B. (1984) Transilient turbulence theory. Part 1 The concept of eddy mixing across finite distances, J. Atmospheric Science 41, 3351-3367. 

Consider the packed distillation tower shown in Figure 16-1. Only binary distillation with constant molal overflow (CMO) will be considered. Let A be the more volatile conponent and B the less volatile component. In addition to making L/V constant and satisfying the energy balances, CMO automatically requires equimolal counterdiffusion, = -Ng. Thus, CMO sinplifies the mass balances, eliminates the need to solve the energy balances, and simplifies the mass transfer equations. We will also assume perfect plug flow of the liquid and vapor. This means that there is no eddy mixing to reduce the separation. 

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