Wavelength Dependence of Eddy Dissipation and Coriolis Force in the Dynamics of Gravity Wave Driven Fluctuations in the OH Nightglow

The theory of Walterscheid et al. (1987) to explain internal gravity wave induced oscillations in the emission intensity I and rotational temperature T of the OH nightglow was modified by Hickey (1988) to include the effects of eddy dissipation and Coriolis force. In the theory of Walterscheid et al. (1987) the ratio η = (δ I / I 0)/(δ T / T 0) (δ refers to a perturbation quantity, and a zero subscript refers to an average) was found to be independent of horizontal wavelength at long periods, while in the extended theory of Hickey (1988) some such dependence was inferred. In the present paper the horizontal wavelength dependence of η is examined. It is found that values of η will be dependent on both wave period and horizontal wavelength, meaning that in order to compare measurement with theory, horizontal wavelengths will need to be measured in conjunction with the OH nightglow measurements. At long periods the modifications to η by the inclusion of eddy dissipation are much larger for the shorter horizontal wavelength waves, although such modifications may be more observable for some of the longer horizontal wavelength waves. The Coriolis force is important only for waves of very large horizontal wavelength.