| Dispersion Modelling Methodology | WNP Processing Plant Air Discharge Assessment | 4397169-66885702-113 | 16/06/2022 | 16 Sensitivity: General can be used by the dispersion model. For this assessment, a 1-year meteorological modelling input file for CALPUFF was developed using the associated meteorological model CALMET (v6.5.0)21. CALMET was used to generate a three-dimensional time-varying meteorological input file. The model prediction takes into consideration the influence that topography and land use have on wind flows and the meteorological parameters that influence the dispersion of pollutants. The meteorological grid point was defined every 100 m in the north-south and east-west directions in an 8km x 8 km (E/W x N/S) meteorological model domain. The Processing Plant was located at approximately the centre of the meteorological grid (UTM 60S coordinate (399542, 5861087)). The modelling domain incorporated the proposed nearby sensitive receptors. CALMET requires both surface and upper air meteorological data inputs. The surface meteorological input requirements for CALMET were obtained from the observations at the Waihi Mine meteorological monitoring station. One-hour average meteorological data from the monitoring station for the simulated year of 2016 was incorporated into the CALMET model22. Although there will be some variation from year to year, the construction of the CALMET file for the year 2016 is representative of typical dispersion conditions at the site. The wind flows observed in 2016 are comparable to those observed between 2013 and 201923. The year 2016 also had the highest percentage of valid observation meteorological data which would be incorporated into the model. CALMET’s upper air input data requirements were derived using the TAPM v4 (‘The Air Pollution Model’) prognostic meteorological model. TAPM predictions were also used to supplement the surface input requirements (i.e air pressure and cloud cover24). TAPM, developed by CSIRO, is a sophisticated computer model that consists of coupled diagnostic meteorological and air pollution components that predict the air flows important to local scale air pollution, such as sea breezes, against a background of larger scale synoptic meteorological patterns. One of the primary functions of the TAPM model’s design is the provision of high-quality meteorological data for dispersion models where suitable onsite information is not available. Using historical synoptic scale meteorological analyses in conjunction with local land use and terrain information, TAPM can produce realistic and high-quality meteorological inputs for air pollutant dispersion modelling systems including CALMET. Validation studies show that TAPM can accurately predict localised meteorological conditions. In this instance, TAPM was used to generate three-dimensional wind flows for every hour of the simulation period. Meteorological grid points were defined every 1 km in the 27km x 27km modelling domain. These predictions were assimilated into CALMET as the “initial guess” of domain wind flows, which are subsequently changed by terrain effects and observations. This approach is expected to improve the accuracy of the final wind flows predicted by CALMET. The predicted hourly average wind speed and wind direction distribution extracted from the CALMET meteorological input file at the approximate location of the proposed the Processing Plant is shown in Figure 21 CALMET was configured and run using the proprietary software “CALPUFF View” (v8.6.1) developed by Lakes Environmental. 22 Hourly wind speed, wind direction, ambient temperature, relative humidity, and rainfall are recorded at the site. 23 Refer to Figure 5-3 of the Waihi North Project – Air Discharge Assessment – Waihi Facilities 24 Cloud cover was derived using by CALMET from TAPM’s three dimensional meteorological inputs
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