The Evolution of Temperature and Velocity Profiles During Breakdown of a Nocturnal Inversion and a Low-Level jet

Abstract

The evolution of the low-level temperature and velocity profiles observed at the Cedar Hill tower during the breakdown of a nocturnal inversion and the dissipation of a low-level jet on the morning of 15 March 1961 is presented and discussed. From past studies of low-level temperature variations, the observed evolution of the temperature profile appears to represent a common phenomenon. Its principal characteristics are warming at the upper levels of the tower before sunrise, increased warming at the upper levels immediately after sunrise, cooling in the middle between upper and lower layers of warming after sunrise, and subsequent lifting of the elevated inversion. Subsidence is suggested as the explanation for the upper-level warming. Turbulent mixing appears to play a major role in the breakdown of the inversion and in the dissipation of the low-level jet.