Atmospheric data eddy diffusion

Assuming that these conditions are met and that the eddy diffusivities Kh and Kv are specified as functions of space and time. Equation (7) provides adequate representation of mean concentrations. Because the diffusivities are essentially empirical parameters to be determined from experimental data, the accuracy of (7) depends upon the degree to which atmospheric conditions at a location of interest correspond to the conditions under which the diffusivities were measured. 

Eddy Diffusion Coefficients. The eddy diffusivities, Kh (x,y,z,t) and Kv (x,y,z,t), which depend on the turbulent structure of the atmosphere, are two of the more elusive quantities that must be estimated. They are not established through direct measurement they must be calculated from observed data. Most of the data that have been acquired to determine Kr (or Kh) have been limited to the surface layer (79) few data are available for conditions under which an elevated inversion was present. As a result, relatively little guidance is available in the literature that can be used to estimate these parameters. 

The first global CH4 budgets were compiled by Ehhalt (1974) and Ehhalt and Schmidt (1978), who used available published information to estimate emissions of CH4 to the atmosphere. They considered paddy fields, freshwater sources (lakes, swamps, and marshes), upland fields and forests, tundra, the ocean, and enteric fermentation by animals as biogenic sources. Anthropogenic sources included industrial natural gas losses and emission from coal mining, and were considered to be free. Observations of CH4 placed an upper limit on anthropogenic sources. Oxidation by the OH radical, as well as loss to the stratosphere by eddy diffusion and Hadley circulation, were presumed to be methane sinks. In spite of lack of data, this work correctly identified the major atmospheric sources and did... 

Clark (55) reviewed the laboratory data and concluded that there was no homogeneous gas phase process capable of accounting for the CO and O2 mixing ratio limits at any altitude. More recently, McElroy and McConnell (93) have concluded that vertical transport with high eddy diffusion coefficients may explain the mixing ratios in the Mars upper atmosphere. The same mechanism cannot, however, account for the lower atmosphere. 

Our knowledge of eddy diffusion coefficients derives largely from observations of the spreading of natural or artificial tracers in the atmosphere and an evaluation of these data by eddy diffusion models based on Eqs. (1-12) and (1-13). The two-dimensional representation requires... 

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