An investigation of clear air versus in cloud turbulence

Forecasting the occurrance of severe atmospheric turbulence remains a difficult problem in aviation meteorology. Part of this difficulty exists because atmospheric turbulence can be caused by a variety of physical mechanisms (e.g. gravity waves, wind shear, convective storms). Previous studies have shown preferred geographical areas of turbulence but since turbulence can have multiple physical causes the reason for these favored areas is not clear.

To shed some light on this issue, we examine the geographical distribution of severe turbulence reports in cloudy and clear areas separately. We use the Real-Time Verification System developed by the Forecast Systems Laboratory to do quality control on pilot reports of turbulence and to quantify the severity of turbulence. We determine cloud cover from ground reports and satellite data. We then comment on how the differences in turbulence distributions under clear and cloud conditions would reflect the physical mechanisms causing the turbulence. We hope to further divide the geographical distribution of turbulence by individual physical mechanisms in the future.