Fast-moving squall lines observed in the tropical oceans are treated as a gravity wave generated by the latent heat release associated with deep cumulus convection. A simple two-dimensional diagnostic linear gravity wave model forced by a zonally propagating heat source is presented. The effect of cumulus friction, or momentum exchange due to cumulus convection, is included in the wave momentum...

We investigate the stability of a Helmholtz velocity profile in a stably stratified fluid when a lower boundary is present. In addition to the traditional Kelvin-Helmholtz interfacial instability we find an infinitude of unstable internal gravity waves, the most unstable of which bear a close resemblance to disturbances observed in connection with clear air turbulence. It is shown that the grav...

We study short period gravity waves (20–120 min) in the equatorial Mesosphere and Lower Thermosphere (MLT) using a Medium Frequency (MF) radar at Pameungpeuk (7.4 S, 107.4 E), Indonesia. In particular, we study local time and seasonal variation of the gravity wave variance and its relation to tropical convection. The gravity wave variance at 88 km enhances between 20:00 LT and 07:00 LT, with a ...

As part of the SpreadFEx campaign, coordinated optical and radio measurements were made from Brazil to investigate the occurrence and properties of equatorial Spread F, and to characterize the regional mesospheric gravity wave field. All-sky image measurements were made from two sites: Brasilia and Cariri located ∼10 S of the magnetic equator and separated by ∼1500 km. In particular, the observ...

The propagation of transient gravity waves in a shear flow towards their critical levels is examined using a ray tracing approximation and a higher-degree (quasi-optic) approximation. Because of its transient forcing, the amplitude of transient waves decays to zero in the neighbourhood of the critical region so that it is not clear whether transient gravity waves will reach the convective insta...

balance, breakdown of balance, and generation of inertia–gravity waves in vortical flows are fundamental topics of prime importance in geophysical fluid dynamics. this research aims to find the optimum balance relation as well as the rossby-number variation of the spontaneous generation of inertia–gravity waves in a baroclinic, two-layer, boussinesq model on a doubly-periodic f-plane geometry f...

We experimentally study the role of forcing on gravity-capillary wave turbulence. Previous laboratory experiments using spatially localized forcing (vibrating blades) have shown that the frequency power-law exponent of the gravity wave spectrum depends on the forcing parameters. By horizontally vibrating the whole container, we observe a spectrum exponent that does not depend on the forcing par...

Parasitic ripple generation on short gravity waves (5 cm to 10 cm wavelengths) is examined using fully-nonlinear computations and laboratory experiments. Time-marching simulations show sensitivity of the ripple steepness to initial conditions, in particular to the crest asymmetry. This unique unsteady e ect enhances ripple generation at moderate wave steepness, e.g. ka between 0.15 and 0.20, a ...

the spontaneous generation of inertia–gravity waves (igws) in the idealized simulation of vortical flows is investigated using the isentropic two-layer model on a sphere. the contour-advective semi-lagrangian (casl) algorithm is applied to solve the primitive equations using the potential vorticity (pv), velocity divergence, and acceleration divergence as the prognostic variables. the casl algo...

We provide a method to determine the motion of a classical massive particle in a background geometry of 2-dimensional gravity theories, for which the Birkhoff theorem holds. In particular, we get the particle trajectory in a continuous class of 2-dimensional dilaton gravity theories that includes the Callan-Giddings-HarveyStrominger (CGHS) model, the Jackiw-Teitelboim (JT) model, and the d-dime...