EFFECT OF CLUSTERING UPON A 500-MB. HORIZONTAL SOUNDING SYSTEM

Abstract

Stream functions and velocity potentials derived from historical tapes of the National Meteorological Center are utilized to provide an estimate of the degree of clustering to be expected from a 500-mb. horizontal-sounding system. From a basically symmetric distribution of particles (balloons) over the Northern Hemisphere north of 15° N., it is found that the clustering tendency increases for 25 days after trajectory initiation and then remains essentially invariant. Under the latter condition the particle density is twice the initial density over 5 percent of the Northern Hemisphere, and is less than one-quarter the initial density over a similar area. Comparison with synoptic maps shows that clustering tends to be associated with ridges in the 500-mb. flow pattern and as a result, in the mean, clustering is most pronounced over western North America and western Europe. Clustering also tends to occur in areas of weak pressure gradient. Dispersion statistics derived from the particle trajectories imply a lateral standard deviation proportional to approximately the 0.5 power of the downwind distance and a value of about 2 ? 1010 cm.2 sec.?1 for the (lateral) eddy diffusivity. The data coverage to be anticipated from constant volume balloon launch sites in Japan is discussed briefly.