Search Results
You are looking at 1 - 6 of 6 items for :
- Author or Editor: P. C. Manins x
- Article x
- Refine by Access: All Content x
Abstract
The West Australian capital city of Perth is located on a coastal plain between the sea to the west and an escarpment rising to the east. It is isolated from all other cities or sources of pollution. In this study, the meteorological conditions leading to high ozone levels have been classified according to the dominant weather patterns using both synoptic charts and air monitoring data. The data revealed that practically all high-ozone days were associated with recirculation of ozone or its precursors. Meteorological modeling was then performed for the generic conditions leading to high ozone in the Perth region. The modeling predicted that recirculation of surface air over the Perth region was common. Both same-day and next-day recirculation of surface air are features of the model predictions and are conducive to high ozone levels. The modeling predicts day-by-day buildup of smog to be a favored occurrence under these synoptic conditions. Other interesting meteorological features seen in Perth observations on high-ozone days were also predicted by the modeling, including stalling sea breezes under some conditions, hydraulic jump effects over the escarpment, and mesoscale enhancement of the west coast trough.
Abstract
The West Australian capital city of Perth is located on a coastal plain between the sea to the west and an escarpment rising to the east. It is isolated from all other cities or sources of pollution. In this study, the meteorological conditions leading to high ozone levels have been classified according to the dominant weather patterns using both synoptic charts and air monitoring data. The data revealed that practically all high-ozone days were associated with recirculation of ozone or its precursors. Meteorological modeling was then performed for the generic conditions leading to high ozone in the Perth region. The modeling predicted that recirculation of surface air over the Perth region was common. Both same-day and next-day recirculation of surface air are features of the model predictions and are conducive to high ozone levels. The modeling predicts day-by-day buildup of smog to be a favored occurrence under these synoptic conditions. Other interesting meteorological features seen in Perth observations on high-ozone days were also predicted by the modeling, including stalling sea breezes under some conditions, hydraulic jump effects over the escarpment, and mesoscale enhancement of the west coast trough.
Abstract
A new model of katabatic winds is presented. A hydraulic approach is employed in which the detailed vertical structure of the flow is replaced by a quiescent stably stratified environment and an equivalent flowing layer which is subject to sustained layer cooling, surface stress and interfacial entrainment. A scaling which contains most of the parametric behavior is found. It shows that interfacial entrainment is the dominating retardation mechanism of the flow and that surface stress may be relatively unimportant.
Steady solutions are presented to show that katabatic winds are essentially supercritical on all practical slopes (slope angles >0.1°), and are affected by ambient stratification only at large distances. The model is in satisfactory quantitative agreement with the limited field data available.
Abstract
A new model of katabatic winds is presented. A hydraulic approach is employed in which the detailed vertical structure of the flow is replaced by a quiescent stably stratified environment and an equivalent flowing layer which is subject to sustained layer cooling, surface stress and interfacial entrainment. A scaling which contains most of the parametric behavior is found. It shows that interfacial entrainment is the dominating retardation mechanism of the flow and that surface stress may be relatively unimportant.
Steady solutions are presented to show that katabatic winds are essentially supercritical on all practical slopes (slope angles >0.1°), and are affected by ambient stratification only at large distances. The model is in satisfactory quantitative agreement with the limited field data available.
Abstract
A three dimensional diagnostic wind field model is shown to be capable of generating potential flow solutions associated with simple terrain features. This is achieved by modifying an initially uniform background wind to make the flow divergence free. Atmospheric stability effects can be incorporated by considering the relative degree of adjustment that is allowed between the horizontal and vertical components of the wind.
A framework for developing a Froude-number-dependent expression for this ratio is proposed and evaluated by comparing modeled streamline deflections of flow past an ideal hill with results from wind tunnel and tow tank experiments.
Abstract
A three dimensional diagnostic wind field model is shown to be capable of generating potential flow solutions associated with simple terrain features. This is achieved by modifying an initially uniform background wind to make the flow divergence free. Atmospheric stability effects can be incorporated by considering the relative degree of adjustment that is allowed between the horizontal and vertical components of the wind.
A framework for developing a Froude-number-dependent expression for this ratio is proposed and evaluated by comparing modeled streamline deflections of flow past an ideal hill with results from wind tunnel and tow tank experiments.
Abstract
A 4-day photochemical smog event in the Melbourne, Victoria, Australia, region (6–9 March 2001) is examined to assess the performance of the Australian Air Quality Forecasting System (AAQFS). Although peak ozone concentrations measured during this period did not exceed the 1-h national air quality standard of 100 ppb, elevated maximum ozone concentrations in the range of 50–80 ppb were recorded at a number of monitoring stations on all four days. These maximum values were in general very well forecast by the AAQFS. On all but the third day the system predicted the advection of ozone precursors over Port Phillip (the adjacent bay) during the morning, where, later in the day, relatively high ozone concentrations developed. The ozone was advected back inland by bay and sea breezes. On the third day, a southerly component to the background wind direction prevented the precursor drainage over the bay, and the characteristic ozone cycle was disrupted. The success of the system's ability to predict peak ozone at individual monitoring stations was largely dependent on the direction and penetration of the sea and bay breezes, which in turn were dependent on the delicate balance between these winds and the opposing synoptic flow.
Abstract
A 4-day photochemical smog event in the Melbourne, Victoria, Australia, region (6–9 March 2001) is examined to assess the performance of the Australian Air Quality Forecasting System (AAQFS). Although peak ozone concentrations measured during this period did not exceed the 1-h national air quality standard of 100 ppb, elevated maximum ozone concentrations in the range of 50–80 ppb were recorded at a number of monitoring stations on all four days. These maximum values were in general very well forecast by the AAQFS. On all but the third day the system predicted the advection of ozone precursors over Port Phillip (the adjacent bay) during the morning, where, later in the day, relatively high ozone concentrations developed. The ozone was advected back inland by bay and sea breezes. On the third day, a southerly component to the background wind direction prevented the precursor drainage over the bay, and the characteristic ozone cycle was disrupted. The success of the system's ability to predict peak ozone at individual monitoring stations was largely dependent on the direction and penetration of the sea and bay breezes, which in turn were dependent on the delicate balance between these winds and the opposing synoptic flow.
Abstract
The performance of the Australian Air Quality Forecasting System (AAQFS) is examined by means of a case study of a 7-day photochemical smog event in the Sydney region. This was the worst smog event for the 2000/ 01 oxidant season, and, because of its prolonged nature, it provided the opportunity to demonstrate the ability of AAQFS to forecast situations involving recirculation of precursors and remnant ozone, fumigation, and complex meteorological dynamics. The forecasting system was able to successfully predict high values of ozone, although at times the peak concentrations for the inland stations were underestimated. The dynamics for the Sydney region require a sensitive balance between the synoptic and mesoscale flows. Often high concentrations of ozone were advected inland by the sea breeze. On two occasions the system forecast a synoptic flow that was too strong, which blocked the inland advancement of the sea breeze. The peak ozone forecasts were underpredicted at the inland stations on those occasions. An examination of possible factors causing forecast errors has indicated that the AAQFS is more sensitive to errors in the meteorological conditions, rather than in the emissions or chemical mechanism in the Sydney region.
Abstract
The performance of the Australian Air Quality Forecasting System (AAQFS) is examined by means of a case study of a 7-day photochemical smog event in the Sydney region. This was the worst smog event for the 2000/ 01 oxidant season, and, because of its prolonged nature, it provided the opportunity to demonstrate the ability of AAQFS to forecast situations involving recirculation of precursors and remnant ozone, fumigation, and complex meteorological dynamics. The forecasting system was able to successfully predict high values of ozone, although at times the peak concentrations for the inland stations were underestimated. The dynamics for the Sydney region require a sensitive balance between the synoptic and mesoscale flows. Often high concentrations of ozone were advected inland by the sea breeze. On two occasions the system forecast a synoptic flow that was too strong, which blocked the inland advancement of the sea breeze. The peak ozone forecasts were underpredicted at the inland stations on those occasions. An examination of possible factors causing forecast errors has indicated that the AAQFS is more sensitive to errors in the meteorological conditions, rather than in the emissions or chemical mechanism in the Sydney region.
Abstract
The Australian Air Quality Forecasting System (AAQFS) is the culmination of a 3-yr project to develop a numerical primitive equation system for generating high-resolution (1–5 km) short-term (24–36 h) forecasts for the Australian coastal cities of Melbourne and Sydney. Forecasts are generated 2 times per day for a range of primary and secondary air pollutants, including ozone, nitrogen dioxide, carbon monoxide, sulfur dioxide, and particles that are less than 10 μm in diameter (PM10). A preliminary assessment of system performance has been undertaken using forecasts generated over a 3-month demonstration period. For the priority pollutant ozone it was found that AAQFS achieved a coefficient of determination of 0.65 and 0.57 for forecasts of peak daily 1-h concentration in Melbourne and Sydney, respectively. The probability of detection and false-alarm rate were 0.71 and 0.55, respectively, for a 60-ppb forecast threshold in Melbourne. A similar level of skill was achieved for Sydney. System performance is also promising for the primary gaseous pollutants. Further development is required before the system can be used to forecast PM10 confidently, with a systematic overprediction of 24-h PM10 concentration occurring during the winter months.
Abstract
The Australian Air Quality Forecasting System (AAQFS) is the culmination of a 3-yr project to develop a numerical primitive equation system for generating high-resolution (1–5 km) short-term (24–36 h) forecasts for the Australian coastal cities of Melbourne and Sydney. Forecasts are generated 2 times per day for a range of primary and secondary air pollutants, including ozone, nitrogen dioxide, carbon monoxide, sulfur dioxide, and particles that are less than 10 μm in diameter (PM10). A preliminary assessment of system performance has been undertaken using forecasts generated over a 3-month demonstration period. For the priority pollutant ozone it was found that AAQFS achieved a coefficient of determination of 0.65 and 0.57 for forecasts of peak daily 1-h concentration in Melbourne and Sydney, respectively. The probability of detection and false-alarm rate were 0.71 and 0.55, respectively, for a 60-ppb forecast threshold in Melbourne. A similar level of skill was achieved for Sydney. System performance is also promising for the primary gaseous pollutants. Further development is required before the system can be used to forecast PM10 confidently, with a systematic overprediction of 24-h PM10 concentration occurring during the winter months.
