Using Numerical Models to Understand Linkages between Deep Convection and Aviation Turbulence (Invited Presentation)

Deep convection has long been recognized as a significant hazard to commercial
aviation. Fortunately, ongoing deep convection can often be identified and
avoided using both onboard and ground-based hazard identification technologies
(e.g., radar, satellite, and lightning detection systems). However, turbulence
hazards related to deep convection can also occur at substantial horizontal and
vertical distances from the regions identified by these hazard identification
technologies. This more difficult to avoid convectively-induced turbulence
(CIT) that is spatially (and sometimes temporally) remote from active deep
convection is sometimes mistaken for the classical clear-air turbulence often
found in the vicinity of jet streams. Much of the recent understanding of the
different mechanisms responsible for CIT has come from analysis of
high-resolution numerical simulations. These simulations have historically been
produced using both idealized models and NWP models representing actual cases
of observed turbulence. The NWP case-study simulations typically use grid
nesting with highest-resolution domains that are unable to resolve the
turbulence itself, but are sometimes sufficient to resolve mechanisms that are
directly responsible for the onset of turbulence. In this talk we discuss some
of these mechanisms, which are typically related to gravity waves produced by
the deep convection, or larger-scale upper-tropospheric/lower-stratospheric
(UTLS) outflows associated with the deep convection, and sometimes a
combination of the two. Advances to computing technology has recently enabled
simulations that can resolve the largest turbulent eddies (L < 100-1000 m) that
affect aviation turbulence. These LES-type simulations are valuable both from
the standpoint of understanding mechanisms responsible for the onset and
characteristics of the turbulence, and to evaluate the realism of NWP
simulations in which the turbulence is most often parameterized. These
higher-resolution research simulations will be increasingly relied upon in the
future to advance understanding of aviation turbulence, and will be briefly
discussed at the conclusion of the talk.