The fine structure of wind in the free air

✍ Scribed by C. S. Durst

• Publisher: John Wiley and Sons
• Year: 1948
• Tongue: English
• Weight: 587 KB
• Volume: 74
• Category: Article
• ISSN: 0035-9009
• DOI: 10.1002/qj.49707432108

✦ Synopsis

Abstract

The fine structure of wind at heights of about 5,000 feet and 20,000 feet is examined by means of smoke puffs released at the appropriate height and followed in a camera obscura. These puffs are released over the camera at short intervals during a period of an hour.

It is found that there are fluctuations in the wind of the free air, the periods of which are 5 to 15 minutes. In the cases considered the vector standard deviations of the fluctuations range from 0·5 knots to 3·5 knots. On making similar calculations from five‐minute mean winds measured from surface anemograms, fluctuations of the same order of magnitude are found. The fluctuations at 5,000 feet are found to be correlated with similar fluctuations at 7,000 and 10,000 feet.

The observations are of necessity made in clear air. It is believed the fluctuations would be greater in some types of cloud.

No obvious connection has as yet been found between the magnitudes of the fluctuations and the wind speed or the source of the air or the temperature structure.