Truncation Effects on Estimated Parameters of Tracer Distributions Sampled on Finite Domains

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  • 1 Department of Meteorology. University of Maryland, College Park Maryland
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Abstract

Methods are presented and demonstrated for compensating for the apparent effect of truncation of the sampled crosswind distribution of a tracer, at either or both boundaries of a surface sampling grid downwind from the point of release. Errors and correction on estimates of the apparent vertical mixing depth, h, the location of the centroid of the crosswind distribution , and the crosswind dispersion parameter, σy are those which would apply to a truncated Gaussian distribution having the observed moments (zeroth, first and second). For truncation on only one side of the tracer cloud, a linear relationship between certain measurable quantities based on moments of partial distributions is used to derive the parameters of a best-fit truncated Gaussian distribution by linear regression. The methods are illustrated by an example from the Cross Appalachian Tracer Experiment and by a Gaussian simulation.

Abstract

Methods are presented and demonstrated for compensating for the apparent effect of truncation of the sampled crosswind distribution of a tracer, at either or both boundaries of a surface sampling grid downwind from the point of release. Errors and correction on estimates of the apparent vertical mixing depth, h, the location of the centroid of the crosswind distribution , and the crosswind dispersion parameter, σy are those which would apply to a truncated Gaussian distribution having the observed moments (zeroth, first and second). For truncation on only one side of the tracer cloud, a linear relationship between certain measurable quantities based on moments of partial distributions is used to derive the parameters of a best-fit truncated Gaussian distribution by linear regression. The methods are illustrated by an example from the Cross Appalachian Tracer Experiment and by a Gaussian simulation.

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