The Kwinana Coastal Fumigation Study: III - Meteorological and turbulence modelling on selected days

The Kwinana Coastal Fumigation Study took place in early 1995 at Kwinana ne ar Perth in Western Australia. The study involved surface and elevated mete orological and plume fumigation measurements in sea-breeze flows near the c oast, and has yielded a comprehensive data set that is suitable for assessi ng meteorological and plume dispersion models. In this paper, we simulate t he meteorology and turbulence on four case study days, and compare model re sults with the detailed surface and aircraft measurements taken during the study. These days had surface synoptic winds ranging from southerly to nort heasterly, with either stable or near-neutral temperature profiles over the sea. The model used was based on that developed by Hurley ( Boundary-Layer Meteo rol. 83, 43-73, 1997), but extended here to allow domain nesting, optional non-hydrostatic simulations, and a vegetative canopy at the surface. The mo del was forced by standard weather service synoptic data, and the simulatio ns have captured the essential features of the strong sea-breeze circulatio n observed on these days. The boundary-layer structure over the sea was pre dicted to be near-neutral or stable in agreement with the observations on t he particular day. The wind speed and direction in the sea-breeze flow were generally predicted well, although the predicted maximum inflow speed over the land was a little too high. The potential temperature was generally ov er-predicted, but temperature gradients agreed well. Predicted turbulence l evels in the bottom-half of the thermal internal boundary layer compared we ll to the observations, but under-estimated the observations in the in the upper half of this layer. Near-surface measurements of meteorological varia bles were predicted well over the entire diurnal cycle, although the predic ted sea-breeze onset was generally too early. A quantitative model evaluati on for the near-surface sites showed the model performance to be better tha n that from other studies, with Index of Agreement (IOA) values of 0.8 (win d speed) and 0.96 (temperature), compared with values of 0.5-0.6 (wind spee d) and 0.33 (temperature) obtained from other studies. The availability of new higher resolution synoptic analyses should obviate the lack of spatial and temporal resolution in synoptic inputs. The incorpo ration of these higher resolution synoptic inputs and new parameterisation schemes should improve future model performance.