Attachment 6 - Odour Impact Assessment - Katestone · 132005.638.06

very unstable atmospheric conditions that may typically occur on a sunny day, to F Class, which represents very
stable atmospheric conditions that typically occur during light wind conditions at night. Unstable conditions (Classes
A to C) are characterised by strong solar heating of the ground that induces turbulent mixing in the atmosphere
close to the ground. This turbulent mixing is the main driver of dispersion during unstable conditions. Dispersion
processes for Class D conditions are dominated by mechanical turbulence generated as the wind passes over
irregularities in the local surface. During the night, the atmospheric conditions are generally stable (often Classes
E and F).

Figure A8 shows the distribution of stability classes extracted from the TAPM/CALMET dataset at the development
site, where Class A represents the most unstable conditions and Class F represents the most stable. Neutral (D
class) conditions are present throughout the day, comprising 54% of total time. Stable (E class) and very stable (F
class) conditions are the next most frequent, comprising 28% of total time, and only occur between 5 pm and 7 am.




Figure A8      Frequency distribution of atmospheric stability conditions predicted by TAPM/CALMET

A1.5.3 Mixing height

The mixing height defines the height of the mixed atmosphere above the ground (mixed layer), which varies
diurnally. Air pollutants released at or near the ground will become dispersed within the mixed layer. During stable
atmospheric conditions, the mixing height is often quite low, and dispersion is limited to within this layer. During the
day, solar radiation heats the ground and causes the air above it to warm, resulting in convection and an increase
to the mixing height. The growth of the mixing height is dependent on how well the warmer air from the ground can
mix with the cooler upper-level air and, therefore, depends on meteorological factors such as the intensity of solar
radiation and wind speed. Strong winds cause the air to be well mixed, resulting in a high mixing height.

Mixing height information extracted from the TAPM/CALMET at the development site dataset are presented as a
diurnal frequency (box and whisker) plot in Figure A9. The plot shows that, on average, the mixing height begins
to increase around 6am and peaks around 3pm before descending rapidly into the evening.




 Katestone Environmental Australia Pty Ltd                                                        17 September 2026
 D25072-8 Noosa Council - Noosa Composting Odour Assessment - Final                                        Page 33