Tropospheric Relative Diffusion Observations

Abstract

Data on relative on relative atmospheric diffusion, that is, the spreading by diffusion of puffs or particle pairs (e.g., of balloons) relative to their mutual center of mass, are reexamined. Richardson (1926) proposed his well-known law, K = 0.2σ4/3;, on the basis of an early collection of such data. More recently, much more extensive data sets have been studied which include relative diffusion data over far greater range of σ values. Further relative diffusion data sources are combined with these and, by classifying these data in various ways, it is shown that they suggest the relation σ?l3/2;, in agreement with previous results including Richardson's, over the range 2 ≤ t ≤ 103 s. There is good evidence of slower diffusion in the range generally corresponding to the spectral ?gap.? For still greater values of t the data are not inconsistent with a second accelerated diffusion regime, displaced by approximately one order of magnitude in σ.