Analysis of Convectively Generated Gravity Waves in the 14–15 July 2015 Mesoscale Convective System during PECAN

Mesoscale convective systems (MCSs) generate a wide variety of gravity waves, from deep, low-frequency waves that can alter the large-scale thermodynamic and kinematic environments in subtle but important ways, to bores that initiate from convective outflows, to waves that propagate into the upper troposphere and lower stratosphere and result in hazardous turbulence for aircraft. Two of the primary goals of the Plains Elevated Convection at Night (PECAN) field campaign in 2015 were to better observe, analyze, and understand nocturnal MCSs, and their generation and interaction with gravity waves.

In this study, we will examine the MCS that occurred on 14-15 July 2015 during PECAN. This MCS initiated in eastern Colorado and moved eastward across Kansas, with a lifetime of over 12 h. The convective line took on a bowing structure for several hours and produced scattered reports of severe winds. The MCS also generated a large, long-lived mesoscale gravity wave, which had characteristics of a bore to the south of the MCS, but a deeper wave structure to the north. Both the northern and southern portions of the wave went on to initiate convection far removed from the MCS itself. Using high-resolution observations collected during PECAN, along with numerical simulations of this event, we will document and analyze the evolution and structure of this wave, its influences on environmental thermodynamic and kinematic profiles, and its role in convection initiation. These results will also be compared with output from idealized simulations of convectively generated gravity waves.