MST radar observations of turbulent altocumulus layers

Abstract

Radar studies of turbulent layers have focused on Kelvin-Helmholtz instabilities caused by vertical shear of horizontal wind, also breaking gravity waves. This study examines another type of turbulent layer, common but rarely studied. Aberystwyth Meso-Strato-Troposphere (MST) radar shows layers of turbulence where there is no unusual wind shear or breaking gravity waves. In three case studies, these layers have a common characteristic of saturated air, reducing the stability to cause possible convective or shear instability. The associated cloud may be already well-known altocumulus. Another case study using the MU radar shows how three-dimensional convective structure can be revealed using a 64-beam method.

Statistical Analysis of Turbulence Characteristics over the Tropical Western Pacific Based on Radiosonde Data

“…This phenomenon is also consistent with the result of [50], which shows that the low-frequency gravity wave easily induces Kelvin-Helmholtz instability. In other words, the gravity wave activity can reduce the static stability, so small vertical shear is also prone to dynamic instability [51]. The vertical scale of turbulence is considerably larger than that in other regions; this is referred to as the "strongest turbulent mixing band" in this article.…”