PNNL

Abstract

Convectively induced turbulence (CIT) is an aviation hazard that is a forecasting challenge because operational weather models are too coarse to resolve turbulence. Turbulence indices are commonly used to aid pilots in avoiding turbulence through nowcasting and limited forecasting systems, but these indices have been designed and calibrated for midlatitude clear air turbulence prediction. An additional limitation with current CIT prediction is the lack of storm stage dependency. In this study, six high resolution simulations of tropical oceanic and midlatitude continental convection are performed to characterize the turbulent environment near various convective types during the developing and mature stages. Simulated convection adequately represented observed convection including timing, morphology, and location. Second-order structure functions, a diagnostic commonly used to identify turbulence in real-time prediction systems, are used to characterize the probability of turbulence for various convective types. Turbulence likelihood was found to be independent of region (i.e., tropical versus midlatitude) but dependent on convective stage. The probability of turbulence increased signi?cantly near developing convection for all cases highlighting the need for developing convection aviation guidelines. Static stability and vertical wind shear, indicators of turbulence potential, were analyzed near convection. The convective environment near developing convection was more favorable for turbulence production and propagation than mature convection. Near developing convection, static stability decreased and vertical wind shear signi?cantly increased. Vertical wind shear near mature and developing convection was found to be strongly correlated to turbulence intensity in both the tropics and midlatitudes.