Measuring in-cloud turbulence: the NEXRAD Turbulence Detection Algorithm

The NEXRAD Turbulence Detection Algorithm has been developed to produce routine measurements of in-cloud turbulence (eddy dissipation rate, EDR) that will contribute to aviation safety and may facilitate a deeper understanding of storm dynamics. Since the first version of the NTDA was deployed in 2007, a number of algorithm updates have been made to accommodate changes to the NEXRAD data acquisition system and to improve the coverage and accuracy of the measurements. These include accommodation of super-resolution and phase-coded data; updated conversions of spectrum width to EDR; and improved data quality control using clutter map information, better signal-to-noise ratio computations and dual-polarimetric data. A real-time, 3D mosaic has been developed to combine data from NEXRADs across the CONUS and create a snapshot of in-cloud EDR at 5-minute intervals. These turbulence grids are being incorporated into the Graphical Turbulence Guidance Nowcast product, which is scheduled to be part of the NextGen Initial Operating Capability, allowing it to identify turbulent areas in clouds that may be largely benign. Moreover, the NTDA allows tracking the evolution of turbulence within convective systems, revealing that the most severe turbulence is not always correlated with the strongest reflectivity and that the magnitude and distribution of turbulence both vary over the storm's lifecycle. It also permits the development of an upper-level convective turbulence climatology.

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.