On ‘potential’ well treatment for atmospheric gravity waves

Abstract. During the Airborne Lidar and Observations of Hawaiian Airglow (ALOHA)Campaign on October 10, 1993, a wave structure with a sharp front covering significant parts of the sky was observed to move with a phase velocity of 76 m/s at a period of 4 to 5 min. Simultaneous observations of the Green line and the OH emission brightness showed a 180 ø phase diffeence. We have two objectives. (1) By using a dispersion formula, we first separated the true partial wave guidance for long-period waves from the background effects and showed explicitly that many partial modes previously thought to exist do not in fact exist. In this way, we can show that two very different methods for computing partial modes which previously gave very different results can now be reconciled. We showed that by lowering the period the modes became, first, virtually guided and then fully guided. (2) We then showed that the long-period S2 partial mode eventually became a two-node fully guided mode, which at periods in the range of 4.6 min, had not only phase velocities comparable to the observed result, but also a phase reversal (from the two-node structure) at altitudes in the vicinity of the two airglow emission peaks. At those periods, the dispersion curves were shown to be out of the range of the nearest "kissing" mode and were thus largely unaffected by interference from the stratospheric duct. The results agree well with an analytic model. The wave explanation may in some way complement the other explanations (such as the bore, or soliton) for the same event mentioned in presentations elsewhere.

mentioning

confidence: 99%

Application of the dispersion formula to long‐and short‐period gravity waves: Comparisons with ALOHA‐93 data and an analytical model

Munasinghe¹,

Hur²,

Huang³

et al. 1998

“…Owing to the earth's ground surface which forms a definite lower boundary and an uneven atmospheric structure, gravity waves were also known to propagate in partially guided (leakage) and fully guided modes (see, for example, Yeh and Liu 1-1974-1, Hines 1-1974-1, and Francis 1-1975-1). Later on, it was found that uneven atmospheric dissipation can also produce partially guided modes and that, in particular, the well-known high-speed F region modes associated with the large-scale TID [Thome, 1968-1 are very likely caused by dissipation [Tuan, 1976;Richmond, 1978;Yu et al, 1980]. In the present paper we wish to show that these three types of gravity wave modes can 'interfere' among themselves.…”

mentioning

confidence: 80%

A dispersion formula for analyzing ‘modal interference’ Among guided and free Gravity wave modes and other phenomena in a realistic atmosphere

Tuan¹,

Tadić²

1982

Gravity waves are known to propagate in the continuous as well as the partially and fully guided modes. Through the development of a dispersion formula we will show that these three modes can ‘interfere’ among themselves and that one important consequence of such ‘interference’ is that the guidance of a large number of partially guided modes can be destroyed. The simple formula for the effective attenuation distance, −1/Im kxn for each complex partially guided mode kxn (where kx is the horizontal wave vector), is no longer valid when there is heavy interference or ‘modal overlap.’ A simple criterion will be developed to distinguish those modes which remain observable from those which exist physically only as part of the general background. We will also show that the presence of an explicit gravity wave source can only selectively or simultaneously excite those modes which are observable and that the other modes remain as part of the background, unaffected by the source. The dispersion formula also shows that a discrete mode should be described by two parameters. One is the usual modal position kxn, while the other is the ‘weight’ which varies with different modes. There is also the possible existence of yet another form of guided mode which we will call the virtually guided mode and which possesses characteristics quite different from the other guided modes.

“…In this paper we wish to consider the effect of gravity waves on H and O3 as well as OH emissions using a gravity model [Tuan, 1976;Yu et al, 1980] which satisfies the rigid surface boundary condition at ground level and can provide for guided as well as free modes. The undisturbed hydrogen and ozone profiles are taken from Good [1976] and T. J. Keneshea and S. P. Zimmerman (private communication, 1979).…”

Section: Omentioning

confidence: 99%

“…The model we use [Tuan, 1976;Yu et al, 1980] Zimmerman (private communication, 1979). In Figures 3 and 4 we show the 'unperturbed' variations in the ozone and hydrogen number density as a function of altitude.…”

Section: Theoretical Formulationmentioning

confidence: 99%

On the effects of atmospheric gravity waves on profiles of H, O₃, and OH emission

Hatfield¹,

Tuan²,

Silverman³

1981

The effect of gravity waves on H and O3 profiles is investigated using a gravity wave model, valid for an inhomogeneous atmosphere. The consequent effect on OH emission is also considered using Good's data for the ‘undisturbed’ profiles. The results show that (1) the magnitude of the response depends on the relative magnitudes and signatures of the vertical and horizontal wave‐induced flux. Since in some regions the horizontal velocity field of the gravity wave can increase much more rapidly with height than the vertical field, horizontal flux can in some instances overcome the vertical even when there is a relatively sharp layer gradient. (2) The structures in the OH profile produced by the gravity wave are in general, but not always, more pronounced below the intensity peak than above. The observed dark areas on OH emission can be produced by gravity waves with vertical wavelength small compared with the half width of the intensity profile.