72 Assessing Potential Climate Change Impacts on Local Air …
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hypothetical facility. The most representative surface and upper air stations (best to
our knowledge) were used for AERMET. Modelled sources cover a wide arrange of
source types in real practices, from point sources with different releasing height and
exiting temperature/velocity, to area and volume sources usually releasing at/near
surface level. Special source types like capped stacks and buoyant line sources were
also included in this assessment. Receptors are allocated only along and outside of
the property line out to a distance of 5 km from the dominant sources with spacing
recommended by the MOECC [2]. Deposition was not considered in this study.
72.2.3 Future Climate Projections for 2051–2055
The 50th percentile projection of hourly wind speed and temperature [3] was used
as potential future climate to produce the future 5-year (2051–2055) meteorological
dataset; other variables (i.e. wind direction, cloud cover) are from the latest historical
5 years (2012–2016) and assumed not to change. As shown in Fig. 72.1, the projected
5-year average wind speeds and temperature are expected to increase by about 11%
(3~15% year to year) and 2.8 °C (1~4.4 °C year to year), respectively, over those
during 1996–2000, at the study location. It should be noted that future climate projections are subject to various uncertainties, especially surface wind speeds which
are significantly influenced by small scale topographic conditions.
72.3 Results and Discussions
Along with the changes in average wind speeds (~10% increase starting from 1998–
2002, with the maximum increase in 2051–2055), Figs. 72.2 and 72.3 respectively
show the relative changes in the modelled maximum 1 and 24 h concentrations for
different 5-year periods in comparison with the 1996–2000 model results, before
meteorological anomaly removal. Figures 72.4 and 72.5 show the relative changes
after meteorological anomaly removal.
Before meteorological anomaly removal, as much as 17% increases are observed
in the modelled 1-hour maximum concentrations from low level releases (i.e. the two
area sources, the central volume source), and up to ~33% increase from stacks with
less plume rise (i.e. the non-buoyant stack 2) during the historical period. For these
source types, maximum concentrations usually occur on or close to property line,
increases of modelled concentration may have been caused by low winds at individual hours coinciding with other factors; whereas the modelled 24 h concentrations
reduced from almost all sources, with most significant reductions (up to ~27%) for
the two area sources; these reductions in 24 h concentrations are most possibly caused
by the increased wind speed for most hours of the day, in other words, the average
wind speed. The greatest reductions are found in the future (2051–2055), up to 45%
453
hypothetical facility. The most representative surface and upper air stations (best to
our knowledge) were used for AERMET. Modelled sources cover a wide arrange of
source types in real practices, from point sources with different releasing height and
exiting temperature/velocity, to area and volume sources usually releasing at/near
surface level. Special source types like capped stacks and buoyant line sources were
also included in this assessment. Receptors are allocated only along and outside of
the property line out to a distance of 5 km from the dominant sources with spacing
recommended by the MOECC [2]. Deposition was not considered in this study.
72.2.3 Future Climate Projections for 2051–2055
The 50th percentile projection of hourly wind speed and temperature [3] was used
as potential future climate to produce the future 5-year (2051–2055) meteorological
dataset; other variables (i.e. wind direction, cloud cover) are from the latest historical
5 years (2012–2016) and assumed not to change. As shown in Fig. 72.1, the projected
5-year average wind speeds and temperature are expected to increase by about 11%
(3~15% year to year) and 2.8 °C (1~4.4 °C year to year), respectively, over those
during 1996–2000, at the study location. It should be noted that future climate projections are subject to various uncertainties, especially surface wind speeds which
are significantly influenced by small scale topographic conditions.
72.3 Results and Discussions
Along with the changes in average wind speeds (~10% increase starting from 1998–
2002, with the maximum increase in 2051–2055), Figs. 72.2 and 72.3 respectively
show the relative changes in the modelled maximum 1 and 24 h concentrations for
different 5-year periods in comparison with the 1996–2000 model results, before
meteorological anomaly removal. Figures 72.4 and 72.5 show the relative changes
after meteorological anomaly removal.
Before meteorological anomaly removal, as much as 17% increases are observed
in the modelled 1-hour maximum concentrations from low level releases (i.e. the two
area sources, the central volume source), and up to ~33% increase from stacks with
less plume rise (i.e. the non-buoyant stack 2) during the historical period. For these
source types, maximum concentrations usually occur on or close to property line,
increases of modelled concentration may have been caused by low winds at individual hours coinciding with other factors; whereas the modelled 24 h concentrations
reduced from almost all sources, with most significant reductions (up to ~27%) for
the two area sources; these reductions in 24 h concentrations are most possibly caused
by the increased wind speed for most hours of the day, in other words, the average
wind speed. The greatest reductions are found in the future (2051–2055), up to 45%