Direct evidence of "sheets' in the atmospheric temperature field

Abstract

This paper presents experimental evidence showing the ubiquitous presence in the lower atmosphere (at least up to 25 km) of very strong (positive) temperature gradients within very thin layers. The presence of such "sheets' in the temperature field of the free atmosphere was frequently hypothesized in order to account for the aspect sensitivity of VHF radar measurements. Owing to their high vertical resolution (20 cm) and to the fast-response thermometers used, the in situ balloon measurements discussed in this paper constitute the first direct evidence of their true existence. Statistical study of the properties of the sheets results in the following typical values: thickness 3-20 m, temperature increase 0.2-0.8 K, gradient 30-100 K/km. The sheets are frequently observed in groups, associated with and taking part in regions of high static stability. -from Authors