Authors: Fabio Vargas, Gary Swenson, Alan Liu, and Delano Gobbi
Summary by Javier Fuentes
The main idea is to derive amplitude and phase relations among multiple airglow layers in response to gravity waves with various intrinsic parameters and damping rates (b).
The method used to develop the study is a linear, one-dimensional model to describe the temporal and spatial variability of the airglow volume emission rate, intensity and weighted temperature. This model has a number of assumptions to simulate the dynamic response of the O(1S) (green line) night airglow emission to atmospheric gravity wave (AGW) perturbations using a model similar to that described by Liu and Swenson [2003] for OH Meinel and O2(b, 0–1) atmospheric band.
The CF introduced by Swenson and Gardner [1998] is the parameter that quantifies this cancellation effect. CFI (CFTm) is defined as the ratio of the airglow intensity (temperature) perturbation amplitude to the gravity wave amplitude.
The analytical function that describes the Cancellation Factor is:
The fitting coefficients and errors are in Table 1:
Table 1. Coefficients and associated errors of the fitting function for the CFI in the airglow layers.
The CFs for temperature (CFTm) and intensity (CFI) contrast each other, as illustrated in Figure 1:
Figure 1. Cancellation factor of intensity (thick lines) and for weighted temperature (thin lines) of mesospheric airglow layers. Red, dark blue, and green colors represent the OH, O2(b) and O(1S) emissions, respectively.
The results through the simulations show that the vertical profile of the standard deviation of the perturbed green line volume emission rate (VER) has a centroid altitude that is 3 km lower and a full-width-half-maximum 2.1 km smaller than the unperturbed VER profile, similar to findings for the OH and O2(b) band layers. Relative phase differences and amplitudes of vertically propagating waves can be deduced from zenith observations of the layers. Airglow weighted responses to waves are related through a cancellation factor (CF) for both layer intensity and temperature. The vertical wavelength can be deduced from relative phase information of three airglow layers separated in altitude. The vertical flux of horizontal momentum associated with gravity waves is deduced from intrinsic wave parameters. Wave damping versus altitude is used to deduce the flux divergence and local accelerations resulting from dissipative waves.
Why is the study may be useful: The simulations are useful in calculating wave information and wave effects on the atmosphere from multi-wavelength, zenith airglow observations.
Reference: Vargas, F., G. Swenson, A. Liu, and D. Gobbi (2007), O(1S), OH, and O2(b) airglow layer perturbations due to AGWs and
their implied effects on the atmosphere, J. Geophys. Res., 112, D14102, doi:10.1029/2006JD007642.
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