Empirical Relationships Between Gust Intensity in Clear-Air Turbulence and Certain Meteorological Quantities

Abstract

Due to a lack of observational data, little information exists in the literature concerning quantitative relationships between turbulent gust intensity in the free atmosphere and commonly measured meteorological quantities. Measurements of turbulence, wind, and temperature made by a B-47 research aircraft are used to investigate such relationships in order to satisfy several practical needs. It is found that a quantity that is the product of wind speed and turning of the wind with height is more closely related to turbulent gust intensity than vertical wind shear or Richardson's number. Variations in the frequency of occurrence of turbulence are determined as the quantities mentioned above increase in magnitude. Moderate or severe turbulence has a frequency of occurrence greater than 50 per cent when the product of wind speed and vertical change of direction exceeds 0.8 deg sec?1, when vertical shear exceeds 0.027 sec?1, or when Richardson's number is less than 0.4 (for calculations made over 2000-ft layers). The writers believe that the results are representative of winter condition in mid-latitudes.