Oct. 12: Atmospheric Sciences seminar focuses on aviation turbulence

Stan Trier, National Center for Atmospheric Research, Boulder, Colorado, will present “Influences of Remote Deep Convection on Aviation Turbulence” on Thursday, Oct. 12, at 3 p.m. in Odegard Hall, Room 112. Faculty and students are encouraged to attend.

Abstract
Prediction of aviation turbulence occurring outside of deep convection is an important practical problem because of its difficult detection using standard hazard identification technologies (e.g., onboard or ground-based radars, satellites, and lightning networks), and the difficulty operational numerical weather prediction (NWP) models have in simulating the mechanisms
directly responsible for it. Many studies have attributed clear-air turbulence (CAT) at commercial aviation cruising altitudes (Z=9-12 km MSL) away from significant terrain to shearing instabilities such as Kelvin-Helmholtz instability (KHI). However, recent research simulations of observed turbulence cases with high-resolution NWP models indicate that aviation turbulence may often be influenced by effects of remotely occurring deep convection. In this way, physical mechanisms producing CAT in many cases may differ from those thought to produce more classically defined clear-air turbulence.

In these cases of convectively-induced turbulence (CIT), gravity waves often play a crucial role in connecting the mesoscale forcing from distant organized convection to the smaller-scale turbulence that aircraft experience. These gravity waves may impact aviation turbulence both directly through wave breaking, or sometimes indirectly, by perturbing environments where the
Richardson number is initially small, and thereby allowing KHI or shallow convective instabilities to occur. When moisture is sufficient such instabilities sometimes manifest as banded cirrus clouds, which can mark locations of observed turbulence. In this talk we diagnose different mechanisms for CIT using nested high-resolution simulations of observed turbulence cases in a wide range of meteorological settings.