Time-Resolving Model For Gravity Waves In Non-Uniformly Stratified Atmosphere (Formerly Poster 27)

Vertically propagating gravity waves can provide a very fast mechanism for information transfer across the atmosphere, from ground level all the way up to the ionosphere, which raises the possibility of tsunami detection via gravity-wave-induced modulations in the airglow patterns in the ionosphere. However, the current gravity-wave modeling approach developed for wave-drag parametrizations relies on many restrictive assumptions that are simply not satisfied in the real-world complex atmospheric environment.

Specifically, applying the current approach to tsunami-induced gravity waves reduces the problem to the well-known stationary mountain lee waves, where the tsunami plays the role of the mountain.  The simplicity comes at a price: (1) an approximate description by a stationary solution omits many time-dependent quantitative details that would be observable in the middle atmosphere; (2) the wave field in a non-uniform stratified atmosphere cannot be accurately captured, since significant partial back-reflection of waves in the vertical naturally occurs at the tropopause.

Therefore, we are developing a time-resolving model to solve the initial-value problem for the gravity waves by using Laplace transforms in time whilst allowing for jumps in stratification.  The Laplace transform method gives new numerical results in the non-uniformly stratified atmosphere model but no closed form because of the difficulties in analytic inverse Laplace transform.  Also we develop a wave-train approximation including possible reflected and transmitted waves, and obtain a closed form. The wave-train solution approximates the numerical transform solution with a great numerical satisfaction, and we recover the gravity-wave propagation mechanism in the low and middle atmosphere.