Kerguelen/Heard Island Simulation

This page describes a numerical simulation of gravity waves over Kerguelen/Heard Islands on December 11, 2023 for comparison with AWE swath 306.

Computational Domain

The layout of the of the simulation is shown in the figure below. The origin is located at (49.3° S, 69.2° E).

surface


The mesh is clustered in the horizontal direction over the islands Kerguelen/Heard with spacings of 500m/800m respectively. Stretching of ~2% is used between the uniform regions and to the boundaries. A uniform vertical spacing of 500m is used to 102 km where the sponge layer is imposed to the top of the domain at 112 km. Inviscid wall boundary conditions are used at the surface whereas characteristic (radiative) conditions are used in combination with a sponge layer at the lateral and top boundaries.

Wind Profiles

The background winds and temperature are fixed in space and time. The plots below show representative profiles for point located at 49.5°S, 69.5°E. Winds taken by combining ERA5 and JAWARA data.

winds

Forcing

In order to minimize starting transients, the mean winds are damped to zero between the surface and 30 km. Forcing terms are then used to increase the near-surface winds over a period of four hours. The forcing terms follow a hyperbolic tangent function in time, which results in very gentle accelerations near the beginning and end of the forcing period. The maximum forcing rate is equivalent to that of a linear ramp with a duration of one hour.

Results