Some observed properties of medium-scale diffusion in the atmosphere

✍ Scribed by F. Pasquill

• Publisher: John Wiley and Sons
• Year: 1962
• Tongue: English
• Weight: 731 KB
• Volume: 88
• Category: Article
• ISSN: 0035-9009
• DOI: 10.1002/qj.49708837507

✦ Synopsis

Abstract

Diffusion experiments using fluorescent particles are described and data on travel and horizontal spread over distances 10 to 80 miles are summarized.

Good vertical mixing evidently counteracts the tendency for a cloud of particles to be sheared according to the wind profile. The effective velocity of the cloud is then close to the mean velocity through the layer of mixing, but some unexplained discrepancies in direction have been encountered. The shearing which can occur in the absence of vertical mixing will become effective as a horizontal spread through the action of subsequent vertical mixing.

The data are insufficient to allow any general conclusion to be reached about the relative importance of horizontal turbulence and vertical shear in promoting horizontal spread.