Boundary layer model, typical transport time

Typical options for turbulent transport in the boundary layer include a level 2.5 Mellor-Yamada closure parametrization (Mellor and Yamada 1982), or a non-local approach implemented by scientists from the Yong-Sei University (YSU scheme, Hong and Pan, 1996). Transport in non-resolved convection is handled by an ensemble scheme developed by Grell and Devenyi (2002). This scheme takes time-averaged rainfall rates from any of the convective parametrizations from the meteorological model to derive the convective fluxes of tracers. This scheme also parameterizes the wet deposition of the chemical constituents. 

The escape of Rn from soils is the source of 99% of the Rn in the atmosphere. Typical radon escape rates are on the order of 1 atomcm s from the land surface, which result in a radon inventory of the global atmosphere of 1.5Xl0 Bq. Atmospheric radon itself is a chemically inert and unscavenged, i.e., not removed from the atmosphere by physical or chemical means. Because its half-life is much less than the mixing time of the atmosphere, it is a tracer of atmospheric transport and can be used in a synoptic approach to identify air masses derived from continental boundary layers or in a climatological manner to verify the predictions of numerical models of transport. 

There is another usuai set of boundary conditions which emerge when, for example, forced convection is imposed within a system. This applies to a small electrolyser with an RDE in anaiyticai chemistry, or in the case of industrial electrolysers when a system is instaiied which imposes forced circulation of the electrolyte or of the electrode. It can be shown in simpie cases that the diffusion layer has a time-independent thickness This thickness is a function of the stirring conditions and of the transport properties of the mobiie species, and is typically about 10 pm. At this point, the Nernst layer model described in section 2.2.1.1 is then used. 

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