Pollution Transfers at Various Scales of Time and Distance

摘要

It is often assumed that problems involving the transfer of pollution by the atmosphere call for specific treatments which differ according to the circumstances, and particularly according to the considered scales of time and distance. The differences between the treatments most commonly used at present, and their similarities, their complementary features, and their association with a single body of doctrine are described. The scales include: the aerological scale (up to a few tens of km); the intermediate scale or mesoscale (a few tens to a few hundreds of km); and, the synoptic and planetary scale (beyond a few hundred km). To be complete, it is necessary to add to this classification the cases of long transfer times in a restricted region of space (low winds, urban pollution). Whatever the scale of the problem to be solved, the treatment itself generally comprises three basic steps: the primitive equations of conservation of mass and momentum, associated with equations of equilibrium and state; the numerical, analytical, or mixed solutions of the primitive equations; and, the relations between the parameters of the medium (meteorological) and the coefficients of the solutions (models). For each of these steps it is convenient to distinguish: between momentum transfers of the carrier fluid and pollutant transfers by the carrier fluid. After a review of the methods commonly used, illustrated by concrete examples, it is concluded that in the field of atmospheric pollution an apparent diversity and disorder actually hide a rather satisfactory situation and that, for most of the problems posed, there exist acceptable practical solutions which are also coherent. (ERA citation 04:057094)