Numerical Simulations of the Impacts of Land-Cover Change on a Southern Sea Breeze in South-West Western Australia

A sea-breeze event in south-west Western Australia is simulated using the Regional Atmospheric Modelling System (RAMS) version 6.0. The model is evaluated against high resolution soundings as well as station observations and is shown to reproduce the qualitative features of the sea breeze well. Sensitivity tests are carried out to investigate the effects of historical land-cover change and changes in soil moisture on the dynamics of the sea breeze. It is found that land-cover change alone, i.e., a change from wooded grasslands to bare soil, with no change in soil moisture initialisation, does not significantly alter the overall structure of the sea breeze but results in higher surface winds due to the reduced vegetation roughness length, which leads to enhanced surface moisture advection inland. On the other hand, land-cover change in conjunction with increased soil moisture results in a considerably weaker, shallower, and less penetrative sea breeze, and delays its onset and duration. A sea-breeze scaling analysis highlights the impact of increasing soil moisture on reducing the sea-breeze volume flux scale.