Mountain wave signatures in MODIS 6.7-μm imagery and their relation to pilot reports of turbulence

Abstract

A technique for nowcasting turbulent mountain waves over the Front Range of the state of Colorado is investigated using Moderate Resolution Imaging Spectroradiometer (MODIS) water vapor (6.7 μm) channel imagery. Pilot reports of turbulence were examined to determine the probability of turbulence occurring when wave features were observed in the satellite imagery. Analysis of MODIS water vapor imagery indicated that mountain wave signatures were present for approximately 25% of the days during 2004. Approximately 75% of the severely turbulent days, as indicated by pilot reports, had wave signatures in the water vapor imagery. The wave signatures on the severely turbulent days had different characteristics in the imagery than the signatures on days that were less turbulent. The reports of severe turbulence were associated with complex patterns, the appearance of interference, or crossing wave fronts that extended downwind from the mountain ridge for a significant distance. The days that were less turbulent, as reported by pilots, had wave signatures with a simpler pattern, such as linear features orthogonal to the wind flow oriented parallel to one another. © 2007 American Meteorological Society.