I. J. Foster

Land-Atmosphere Interaction in a Semiarid Region: The Bunny Fence Experiment

Southwestern Australia, with a semiarid Mediterranean climate, has been extensively cleared of native vegetation for winter-growing agricultural species. The resultant reduction in evapotranspiration has increased land salinisation. Through detailed meteorological and vegetation measurements over both agricultural and native vegetation, the bunny fence experiment is addressing the impact on the climate of replacing native perennial vegetation with winter-growing annual species. Such measurements will give a better understanding of the interaction between the land surface and the atmosphere and are important for improved parameterization of the boundary layer in climate models.

Sensitivity of WRF to driving data and physics options on a seasonal time-scale for the southwest of Western Australia

AbstractRegional climate models are sensitive to the forcing data used, as well as different model physics options. Additionally, the behaviour of physics parameterisations may vary depending on the location of the domain due to different climatic regimes. In this study, we carry out a sensitivity analysis of the weather research and forecasting model to different driving data and model physics options over a 10-km resolution domain in the southwest of Western Australia, a region with Mediterranean climate. Simulations are carried out on a seasonal time-scale, in order to better inform future long-term regional climate simulations for this region. We show that the choice of radiation scheme had a strong influence on both temperature and precipitation; the choice of planetary boundary layer scheme has a particularly large influence on minimum temperatures; and, the choice of cumulus scheme or more complex micro-physics did not strongly influence precipitation simulations. More importantly, we show that the same radiation scheme, when used with different driving data, can lead to different results.

Validation of a Simple Steady-State Forecast of Minimum Nocturnal Temperatures

A two-layer steady-state resistance model is compared with routine meteorological data collected from the Western Australian wheat belt during 2000-06. Major difficulties in implementing such a model are the correct parameterization for the incoming longwave radiation and estimation of daily soil moisture, neither of which are routinely measured. These difficulties are addressed by testing parameterizations for incoming longwave radiation calibrated to local conditions and incorporating a soil-water balance model based on routine weather data. The modified model has RMSE and biases ranging from 2.4° to 3.1°C and -0.2° to 0.8°C, respectively, across the wheat belt when comparing all minimum nocturnal temperatures. The model is shown to predict frost events approximately 55% of the time and illustrates that frost damage to foliage may occur when screen temperatures are < 2°C.