Practical Assessment of the CALMET Meteorological Processor in Generating 3-Dimensional Meteorology in Complex Terrain
A unique study location exists in the Southern Tablelands of NSW. The site in question has relatively complex terrain features, is prone to complex wind flows, and is unusual in that it is surrounded by five automatic weather stations within a five kilometre radius. The weather stations provide long-term, reliable meteorological observations at varying heights above ground level and therefore provide an excellent resource for investigating the ability of the CALMET meteorological processor.
The objective of this study is therefore to conduct a performance assessment of CALMET, the meteorological component of the CALPUFF atmospheric dispersion model, in generating a 3-Dimensional meteorological field for a defined small-scale area with complex local terrain.
The performance as assessed by comparing the 3-Dimensional meteorological fields generated from hourly meteorological data sourced from a series of weather stations within the study area, a dataset externally generated using the MM5 meteorological model and a combination of the two datasets. The topography of the study area was included in these models and assisted in the assessment of CALMET, particularly its ability in replicating terrain-influenced flow.
Wind vector fields were coupled with predicted sensible heat flux, frictional velocities, Monin-Obukhov lengths and mixing heights to compare the performance of CALMET under the influence of the two meteorological datasets. Additionally, the sensitivity of the CALMET model to the adjustment of key parameters, such as the terrain radius of influence values (TERRAD) was assessed.
The use of surface observational datasets as input into CALMET was found to be most proficient in accurately predicting local-scale conditions, while the combination of surface observational with a regional-scale MM5 dataset for upper air produces a desirable balance of both accurate local and regional scale meteorological conditions.
Keywords: CALMET, Boundary Layer Meteorology, MM5, modelling, valley winds,