Simulations of Gravity Wave-induced Turbulence at Cruise Altitudes Near Observed Thunderstorms

Recent research that combines observations and high-resolution numerical simulations has illustrated the frequent important role of organized deep convection on the occurrence of turbulence at commercial aviation cruising altitudes. Such turbulence can be difficult to avoid because it sometimes occur either above or at significant horizontal distances from the storm and is therefore not easily anticipated using onboard hazard identification (e.g., radar). In these cases, atmospheric gravity waves initiated by the remote deep convection often have a prominent role in the development of the turbulence. The turbulence can arise in a variety of ways, including directly from wave breaking or from subtle modifications to the environment in the vicinity of the waves. These environmental variations influence the gradient Richardson number, making the atmosphere more susceptible to turbulence.

On 4 June 2015, eastward propagating gravity waves are evident in the cirrus anvil of a large isolated thunderstorm (Fig. 1) that occurred during the Plains Elevated Convection at Night (PECAN) field experiment conducted from 1 June-15 July over the central and southern Plains of the United States. Special sounding observations from PECAN (not shown) combined with high-resolution (1-km) visible satellite data indicated conditions in the upper-level outflow that favored wave trapping. This allowed the waves to maintain their coherence and extend over 100 km downstream (SE) of a triggering updraft on the west side of the storm (Fig. 1), which penetrated a layer of high static stability near the tropopause. Both three-dimensional high-resolution simulations with the ARW-WRF model and initially horizontally homogeneous idealized simulations are conducted to better understand the mechanism of the waves and how they could influence turbulence. More detailed observations from this case and results from these simulations will be presented at the conference.

Figure 1. 1-km GOES visible satellite image at 0115 UTC 4 June. The storm referred to in the text is located in southwest to southcentral Kansas. State geographical borders are indicated by the yellow lines, and the white rectangular regions comprise 1° LAT by 1° LON regions.

This research is in response to requirements and funding by the Federal Aviation Administration (FAA).  The views expressed are those of the authors and do not necessarily represent the official policy or position of the FAA