An Analysis of the Vertical Velocity at the Leading Edge of a Density Current during PECAN

The maximum upward vertical velocity at the leading edge of a density current is commonly between 8-10 m/s. However, while the propagation speed and height of a density current have been the subject of past studies, research describing the vertical velocity at the leading edge of a density current is limited. This lack of research can partly be attributed to the dearth of high spatiotemporal observations of density currents. Vertical velocity is important because it may be strong and sustained enough to trigger convection. During the Plains Elevated Convection at Night (PECAN) field project, a mobile Doppler lidar measured a maximum vertical velocity of ~13 m/s at the leading edge of a density current created by an MCS during the night of 15 July 2015. This study describes the structure of this density current and attempts to estimate the maximum vertical velocity at the leading edge of this density current using properties of the density current including its height, the system-relative wind speed, and the slope of the density current head. This estimate is compared to the lidar-observation estimates. The method will then be applied to estimate the vertical velocity at the leading edge of other density currents during PECAN where observations of vertical velocity are available as well as estimating the vertical velocity of density currents using idealized numerical simulations. These numerical simulations will be conducted in neutral and stable atmospheres to study the effects of stable stratification on the vertical velocity at the leading edge of a density current. Studies of what happens in a stable environment are especially important for nocturnal convective systems.