ANALYSIS OF CLEAR AIR TURBULENCE DURING SELECTED 5-DAY DATA PERIODS.
WEATHER BUREAU SILVER SPRING MD TECHNIQUES DEVELOPMENT LAB
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Clear air turbulence data were collected from two of the four world-wide reporting periods set up by the International Civil Aviation Organization ICAO. The occurrences and non-occurrences of turbulence were summarized with respect to time periods, altitudes, and geographical locations. These data were analyzed in relation to associated meteorological parameters and large-scale synoptic patterns. Special attention was given to areas with at least 25 percent probability of moderate or greater turbulence. Vertical wind shear appeared to be an important parameter along with 12-hour changes in wind speed, vertical wind shear, and horizontal wind shear. The synoptic patterns on the mean 300-mb charts and the individual 300-mb charts were discussed in relation to the probabilities of moderate or greater turbulence. The following forecast criteria were suggested moderate or greater turbulence will be found 1 within 150 miles of a jet stream with at least a 100-knot maximum wind speed if the vertical wind shear is at least 4 knots per 1000 feet, or 2 within 150 miles of a sharp trough line with a marked horizontal wind shear across the trough line. Author
- Atmospheric Physics