Rodney Potts - Academia.edu (original) (raw)

Papers by Rodney Potts

Low altitude wind shear and its potential impact on aircraft during landing and takeoff is well u... more Low altitude wind shear and its potential impact on aircraft during landing and takeoff is well understood. In general, the wind shear events that present the greatest risk to aircraft are those

Determining the geometric path to the runway threshold is critical to perform an efficient and pr... more Determining the geometric path to the runway threshold is critical to perform an efficient and predictable Continuous Descent Arrival (CDA). To build the geometric arrival path, the aircraft's Flight Management System needs to be aware of the forecast winds during the descent. Inaccuracies in these forecast winds will lead to a geometric path that cannot be flown as a true CDA; (manual) energy management is required to maintain the path at the cost of loss in efficiency - fuel burn - and predictability - accuracy of trajectory predictions. Design constraints of the FMS restrict it to limited wind data to define the wind profile for the complete descent trajectory. Airservices Australia has developed a tool that dynamically tailors the wind forecast for a specific arrival trajectory using an improved resolution forecast provided by the Australian Bureau of Meteorology. Results indicated that the tailored descent forecasts did provide a better representation of the wind profile on...

In order to perform an efficient and predictable Continuous Descent Arrival (CDA), it is critical... more In order to perform an efficient and predictable Continuous Descent Arrival (CDA), it is critical to accurately determine the geometric descent path that can be flown with idle thrust for the selected Cost Index. To build the geometric descent path, the aircraft's Flight Management System (FMS) needs to be aware of the forecast winds during the descent. Inaccuracies in these forecast winds can lead to a geometric path that cannot be flown as an idle-thrust CDA; (manual) energy management is required to maintain the path at the cost of loss in efficiency (fuel burn). Secondly, inaccurate forecast winds impact on predictability as they reduce the accuracy of trajectory predictions made by the FMS. This inaccuracy is caused by both the error in the forecast wind, and the deviations from the target descent speed as result of maintaining the inaccurately built geometric path at idle thrust (either too steep or too shallow). Design constraints of current FMSs restrict the number of fl...

ANZIAM Journal, 2016

We present a new inverse modelling approach for integrating satellite detections of volcanic ash ... more We present a new inverse modelling approach for integrating satellite detections of volcanic ash with dispersion models. We demonstrate the utility of this approach in estimating the ash column height in the February 2014 eruption of Mount Kelut in Java, Indonesia. We show that the inferred height is consistent with estimates obtained by other remote sensing techniques. This method may be used to obtain estimates of model parameters such as ash column height in cases where no such information is available or is subject to significant uncertainty.

Remote Sensing of Environment, 2004

We examined recent volcanic cloud events in the Western Pacific and Indonesian area, to validate ... more We examined recent volcanic cloud events in the Western Pacific and Indonesian area, to validate the performance of remote sensing techniques used to support the International Airways Volcano Watch (IAVW). Five events were considered, during which eruptions from eight volcanoes injected ash into the upper troposphere or lower stratosphere. For one of the eruptions, at Miyakejima, Japan, at least five aircraft encountered volcanic ash clouds, and the cost to three operators alone exceeded US $12,000,000 in aircraft repairs, diversions, and lost operating time. We performed 'reverse' absorption and 'pattern analysis' using GMS-5/VISSR, MODIS and AVHRR data, and we examined TOMS SO 2 and Aerosol Index data, surface-based observations, pilot reports, and dispersion model output. Our results verify that the introduction of 'reverse' absorption using the geostationary GMS-5 platform significantly enhanced our capacity to monitor volcanic ash clouds in the region. In one case, we tracked an eruption cloud for approximately 80 hours. The primary impediment to remote monitoring is the presence of overlying cloud, or substantial amounts of ice within the volcanic clouds. TOMS data showed success in identifying volcanic clouds during these conditions, but was limited by the infrequency of observations. More effective future operation of the IAVW relies on developing complementary methods of volcanic cloud remote sensing, and greatly increasing the amount and quality of available surface and air observations, including observations of precursor activity. An understanding of the likely future limitations of remote sensing techniques will aid in the refining of IAVW procedures.

We briefly describe current operational remote sensing at the Darwin Volcanic Ash Advisory Centre... more We briefly describe current operational remote sensing at the Darwin Volcanic Ash Advisory Centre. The region has been particularly active during the second part of 2002, and we show GMS-5, NOAA/AVHRR-16, and Aqua/MODIS data from eruptions of Raung (Java, Indonesia), and Ruang (Sangihe Islands, Indonesia). We also show a possible 'volcanic thunderstorm' from Rabaul, Papua New Guinea, in 1999. The

The Darwin VAAC provides advice on volcanic ash for the aviation industry in accordance with arra... more The Darwin VAAC provides advice on volcanic ash for the aviation industry in accordance with arrangements established as part of the ICAO International Airways Volcano Watch. The Advisory information is based on an initial report or detection of a volcanic eruption or ash cloud, an analysis of satellite data to identify and track the ash cloud, and a forecast of the movement of the ash derived from upper level winds and an atmospheric dispersion model. When preparing required advice on volcanic ash for the aviation industry, uncertainties in the satellite analysis and output from the ash dispersion model make it essential for the forecaster to directly interact with interim products to generate the output products. This process is manually intensive and it does not take advantage of modern techniques for better integration and automation. We describe a person-machine user interface that is being developed to streamline preparation of the VAA text product, automatically generate a corresponding graphical product, and enables satellite data and dispersion model outputs to be used in more integrated way to delineate analyzed and forecast threat areas.

Weather and Forecasting, 1990

Two studies of microbunt forecasting were conducted in order to demonstrate the utility of applyi... more Two studies of microbunt forecasting were conducted in order to demonstrate the utility of applying theoretical and methodological concepts from judgment and decision making to meteorology. A hierarchical model of the judgment process is outlined in which a precursor identification phase is separated from the prediction phase. In the first study, forecasters were provided with specific, unambiguous precursor values and were asked to provide judgments regarding the probability of a microburst. Results indicated that the meteorologists' forecasts were adequately predicted by a linear model. Modest agreement was observed among the forecasters' judgments. In the second study, forecasters viewed storms under dynamic conditions representative of their usual operational setting. They made judgments regarding precursor values, as well as of the probability ofa microburst occurring. The forecasters' agreement regarding microbunt predictions was found to be lower than in the first study. Surprisingly, agreement regarding the (subjectively) most important precursor value was near zero. These results indicate that there are indeed practical advantages to be gained from a better understanding of the precursor identification and prediction phases of the forecasting process.

Monthly Weather Review, 2000

The characteristics of radar echoes for 12 thunderstorm days in the vicinity of Sydney, Australia... more The characteristics of radar echoes for 12 thunderstorm days in the vicinity of Sydney, Australia, in the summer of 1995/96 have been examined using an objective methodology for storm identification and tracking. The spatial distribution of identified storms shows a maximum in frequency and intensity along the east side of the mountains that lie inland from the coast. Characteristics such as storm volume, area, and height are shown to have a lognormal frequency distribution. Reflectivity also has a skewed frequency distribution with a prevalence of lower reflectivity storms. Both the maximum reflectivity and storm height are shown to be correlated with the logarithm of storm volume. Although small storms predominate, the bulk of precipitation flux comes from the relatively few large-scale storms. It is also shown that storms generally move or propagate in a direction slightly to the left of the mass-weighted mean wind for the surface-to-300-hPa layer at a speed slightly less than the mean speed. Furthermore the deviation of the storm to the left of the mean layer wind increases and the standard deviation decreases as the storm size increases.

Bulletin of the American Meteorological Society, 2003

The first World Weather Research Programme (WWRP) Forecast Demonstration Project (FDP), with a fo... more The first World Weather Research Programme (WWRP) Forecast Demonstration Project (FDP), with a focus on nowcasting, was conducted in Sydney, Australia, from 4 September to 21 November 2000 during a period associated with the Sydney 2000 Olympic Games. Through international collaboration, nine nowcasting systems from the United States, United Kingdom, Canada, and Australia were deployed at the Sydney Office of the Bureau of Meteorology (BOM) to demonstrate the capability of modern forecast systems and to quantify the associated benefits in the delivery of a real-time nowcast service. On-going verification and impact studies supported by international committees assisted by the WWRP formed an integral part of this project. A description is given of the project, including component systems, the weather, and initial outcomes. Initial results show that the nowcasting systems tested were transferable and able to provide valuable information enhancing BOM nowcasts. The project provided for...

ABSTRACT Fog at Melbourne Airport, Australia, occurs around 12 times each year, of which about 2 ... more ABSTRACT Fog at Melbourne Airport, Australia, occurs around 12 times each year, of which about 2 fog events had been unforecast per year prior to 2005. Unforecast fogs are costly to the aviation industry, cause disruption and affect safety. Thus there is a need to improve on the existing operational forecasting. Hence we developed a Bayesian Objective Fog Forecast Information Network (BOFFIN), which combines several fog predictors and a previously used guidance source (Stern-Parkyn method). The resulting fog probability and suggested fog forecasts proved to have greater skill than previously available guidance and operational forecasts. The skill of BOFFIN increased during a subsequent 3 year operational trial. During this period all 38 fog events were correctly forecast operationally, a significant improvement compared to previous performance. BOFFIN has been accepted by forecasters, who appreciate the ability of the system to visually and probabilistically explain the forecasts produced, and to provide soundly based forecasts for alternative scenarios including where a predictor is judged unrepresentative.

We discuss recent eruptions from Ruang, Semeru and Rabaul, and some mysterious aircraft encounter... more We discuss recent eruptions from Ruang, Semeru and Rabaul, and some mysterious aircraft encounters over Micronesia, in the context of current Darwin VAAC operations. Ruang was generally monitored successfully, with some qualifications such as a high level, eastward moving SO 2 cloud that was only clear in post-analysis, and the complete lack of aviation 'SIGMETs'. Rabaul and Semeru are both long running, generally low level eruptions where little can be seen on satellite imagery. Three aircraft encounters occurred over Micronesia without the source of the volcanic cloud being identified. While International Airways Volcano Watch performance is steadily improving, there are still significant scientific and procedural concerns highlighted by the above cases.

Thunderstorms and the associated weather have a range of impacts on operations at airports that i... more Thunderstorms and the associated weather have a range of impacts on operations at airports that include disruption to air traffic and also to ground operations. Lightning in particular presents a hazard to ground staff and procedures have been developed to ensure safe operations. This includes the provision of alerts when thunderstorms and associated lightning are present in the vicinity of designated airports. Various ground operations cease for the duration of the alert with the result that aircraft docking and associated procedures effectively cease. The flow-on disruption can last for many hours and extend around the country as aircraft cannot be unloaded and refuelled, they cannot leave parking bays and arriving aircraft have no place to park. Manual thunderstorm alerts were prepared in the past but the efficacy was limited because they tended to be conservative and did not provide real-time information on the shortterm variations that can occur during periods of thunderstorms....

SAE International Journal of Aerospace

Journal of Geophysical Research: Atmospheres

Bulletin of the American Meteorological Society

In the past two decades, more than 150 jet engine power-loss and damage events have been attribut... more In the past two decades, more than 150 jet engine power-loss and damage events have been attributed to a phenomenon known as ice crystal icing (ICI). Ingestion of large numbers of ice particles into the engine core are thought to be responsible for these events, which typically occur at high altitudes near large convective systems in tropical air masses. In recent years, scientists, engineers, aviation regulators, and airlines from around the world have collaborated to better understand the relevant meteorological processes associated with ICI events, solve critical engineering problems, develop new certification standards, and devise mitigation strategies for the aviation industry. One area of research is the development of nowcasting techniques based on available remote sensing technology and numerical weather prediction (NWP) models to identify areas of high ice water content (IWC) and enable the provision of alerts to the aviation industry. Multiple techniques have been develope...

Journal of Geophysical Research: Atmospheres

Low altitude wind shear and its potential impact on aircraft during landing and takeoff is well u... more Low altitude wind shear and its potential impact on aircraft during landing and takeoff is well understood. In general, the wind shear events that present the greatest risk to aircraft are those

Determining the geometric path to the runway threshold is critical to perform an efficient and pr... more Determining the geometric path to the runway threshold is critical to perform an efficient and predictable Continuous Descent Arrival (CDA). To build the geometric arrival path, the aircraft's Flight Management System needs to be aware of the forecast winds during the descent. Inaccuracies in these forecast winds will lead to a geometric path that cannot be flown as a true CDA; (manual) energy management is required to maintain the path at the cost of loss in efficiency - fuel burn - and predictability - accuracy of trajectory predictions. Design constraints of the FMS restrict it to limited wind data to define the wind profile for the complete descent trajectory. Airservices Australia has developed a tool that dynamically tailors the wind forecast for a specific arrival trajectory using an improved resolution forecast provided by the Australian Bureau of Meteorology. Results indicated that the tailored descent forecasts did provide a better representation of the wind profile on...

In order to perform an efficient and predictable Continuous Descent Arrival (CDA), it is critical... more In order to perform an efficient and predictable Continuous Descent Arrival (CDA), it is critical to accurately determine the geometric descent path that can be flown with idle thrust for the selected Cost Index. To build the geometric descent path, the aircraft's Flight Management System (FMS) needs to be aware of the forecast winds during the descent. Inaccuracies in these forecast winds can lead to a geometric path that cannot be flown as an idle-thrust CDA; (manual) energy management is required to maintain the path at the cost of loss in efficiency (fuel burn). Secondly, inaccurate forecast winds impact on predictability as they reduce the accuracy of trajectory predictions made by the FMS. This inaccuracy is caused by both the error in the forecast wind, and the deviations from the target descent speed as result of maintaining the inaccurately built geometric path at idle thrust (either too steep or too shallow). Design constraints of current FMSs restrict the number of fl...

ANZIAM Journal, 2016

We present a new inverse modelling approach for integrating satellite detections of volcanic ash ... more We present a new inverse modelling approach for integrating satellite detections of volcanic ash with dispersion models. We demonstrate the utility of this approach in estimating the ash column height in the February 2014 eruption of Mount Kelut in Java, Indonesia. We show that the inferred height is consistent with estimates obtained by other remote sensing techniques. This method may be used to obtain estimates of model parameters such as ash column height in cases where no such information is available or is subject to significant uncertainty.

Remote Sensing of Environment, 2004

We examined recent volcanic cloud events in the Western Pacific and Indonesian area, to validate ... more We examined recent volcanic cloud events in the Western Pacific and Indonesian area, to validate the performance of remote sensing techniques used to support the International Airways Volcano Watch (IAVW). Five events were considered, during which eruptions from eight volcanoes injected ash into the upper troposphere or lower stratosphere. For one of the eruptions, at Miyakejima, Japan, at least five aircraft encountered volcanic ash clouds, and the cost to three operators alone exceeded US $12,000,000 in aircraft repairs, diversions, and lost operating time. We performed 'reverse' absorption and 'pattern analysis' using GMS-5/VISSR, MODIS and AVHRR data, and we examined TOMS SO 2 and Aerosol Index data, surface-based observations, pilot reports, and dispersion model output. Our results verify that the introduction of 'reverse' absorption using the geostationary GMS-5 platform significantly enhanced our capacity to monitor volcanic ash clouds in the region. In one case, we tracked an eruption cloud for approximately 80 hours. The primary impediment to remote monitoring is the presence of overlying cloud, or substantial amounts of ice within the volcanic clouds. TOMS data showed success in identifying volcanic clouds during these conditions, but was limited by the infrequency of observations. More effective future operation of the IAVW relies on developing complementary methods of volcanic cloud remote sensing, and greatly increasing the amount and quality of available surface and air observations, including observations of precursor activity. An understanding of the likely future limitations of remote sensing techniques will aid in the refining of IAVW procedures.

We briefly describe current operational remote sensing at the Darwin Volcanic Ash Advisory Centre... more We briefly describe current operational remote sensing at the Darwin Volcanic Ash Advisory Centre. The region has been particularly active during the second part of 2002, and we show GMS-5, NOAA/AVHRR-16, and Aqua/MODIS data from eruptions of Raung (Java, Indonesia), and Ruang (Sangihe Islands, Indonesia). We also show a possible 'volcanic thunderstorm' from Rabaul, Papua New Guinea, in 1999. The

The Darwin VAAC provides advice on volcanic ash for the aviation industry in accordance with arra... more The Darwin VAAC provides advice on volcanic ash for the aviation industry in accordance with arrangements established as part of the ICAO International Airways Volcano Watch. The Advisory information is based on an initial report or detection of a volcanic eruption or ash cloud, an analysis of satellite data to identify and track the ash cloud, and a forecast of the movement of the ash derived from upper level winds and an atmospheric dispersion model. When preparing required advice on volcanic ash for the aviation industry, uncertainties in the satellite analysis and output from the ash dispersion model make it essential for the forecaster to directly interact with interim products to generate the output products. This process is manually intensive and it does not take advantage of modern techniques for better integration and automation. We describe a person-machine user interface that is being developed to streamline preparation of the VAA text product, automatically generate a corresponding graphical product, and enables satellite data and dispersion model outputs to be used in more integrated way to delineate analyzed and forecast threat areas.

Weather and Forecasting, 1990

Two studies of microbunt forecasting were conducted in order to demonstrate the utility of applyi... more Two studies of microbunt forecasting were conducted in order to demonstrate the utility of applying theoretical and methodological concepts from judgment and decision making to meteorology. A hierarchical model of the judgment process is outlined in which a precursor identification phase is separated from the prediction phase. In the first study, forecasters were provided with specific, unambiguous precursor values and were asked to provide judgments regarding the probability of a microburst. Results indicated that the meteorologists' forecasts were adequately predicted by a linear model. Modest agreement was observed among the forecasters' judgments. In the second study, forecasters viewed storms under dynamic conditions representative of their usual operational setting. They made judgments regarding precursor values, as well as of the probability ofa microburst occurring. The forecasters' agreement regarding microbunt predictions was found to be lower than in the first study. Surprisingly, agreement regarding the (subjectively) most important precursor value was near zero. These results indicate that there are indeed practical advantages to be gained from a better understanding of the precursor identification and prediction phases of the forecasting process.

Monthly Weather Review, 2000

The characteristics of radar echoes for 12 thunderstorm days in the vicinity of Sydney, Australia... more The characteristics of radar echoes for 12 thunderstorm days in the vicinity of Sydney, Australia, in the summer of 1995/96 have been examined using an objective methodology for storm identification and tracking. The spatial distribution of identified storms shows a maximum in frequency and intensity along the east side of the mountains that lie inland from the coast. Characteristics such as storm volume, area, and height are shown to have a lognormal frequency distribution. Reflectivity also has a skewed frequency distribution with a prevalence of lower reflectivity storms. Both the maximum reflectivity and storm height are shown to be correlated with the logarithm of storm volume. Although small storms predominate, the bulk of precipitation flux comes from the relatively few large-scale storms. It is also shown that storms generally move or propagate in a direction slightly to the left of the mass-weighted mean wind for the surface-to-300-hPa layer at a speed slightly less than the mean speed. Furthermore the deviation of the storm to the left of the mean layer wind increases and the standard deviation decreases as the storm size increases.

Bulletin of the American Meteorological Society, 2003

The first World Weather Research Programme (WWRP) Forecast Demonstration Project (FDP), with a fo... more The first World Weather Research Programme (WWRP) Forecast Demonstration Project (FDP), with a focus on nowcasting, was conducted in Sydney, Australia, from 4 September to 21 November 2000 during a period associated with the Sydney 2000 Olympic Games. Through international collaboration, nine nowcasting systems from the United States, United Kingdom, Canada, and Australia were deployed at the Sydney Office of the Bureau of Meteorology (BOM) to demonstrate the capability of modern forecast systems and to quantify the associated benefits in the delivery of a real-time nowcast service. On-going verification and impact studies supported by international committees assisted by the WWRP formed an integral part of this project. A description is given of the project, including component systems, the weather, and initial outcomes. Initial results show that the nowcasting systems tested were transferable and able to provide valuable information enhancing BOM nowcasts. The project provided for...

ABSTRACT Fog at Melbourne Airport, Australia, occurs around 12 times each year, of which about 2 ... more ABSTRACT Fog at Melbourne Airport, Australia, occurs around 12 times each year, of which about 2 fog events had been unforecast per year prior to 2005. Unforecast fogs are costly to the aviation industry, cause disruption and affect safety. Thus there is a need to improve on the existing operational forecasting. Hence we developed a Bayesian Objective Fog Forecast Information Network (BOFFIN), which combines several fog predictors and a previously used guidance source (Stern-Parkyn method). The resulting fog probability and suggested fog forecasts proved to have greater skill than previously available guidance and operational forecasts. The skill of BOFFIN increased during a subsequent 3 year operational trial. During this period all 38 fog events were correctly forecast operationally, a significant improvement compared to previous performance. BOFFIN has been accepted by forecasters, who appreciate the ability of the system to visually and probabilistically explain the forecasts produced, and to provide soundly based forecasts for alternative scenarios including where a predictor is judged unrepresentative.

We discuss recent eruptions from Ruang, Semeru and Rabaul, and some mysterious aircraft encounter... more We discuss recent eruptions from Ruang, Semeru and Rabaul, and some mysterious aircraft encounters over Micronesia, in the context of current Darwin VAAC operations. Ruang was generally monitored successfully, with some qualifications such as a high level, eastward moving SO 2 cloud that was only clear in post-analysis, and the complete lack of aviation 'SIGMETs'. Rabaul and Semeru are both long running, generally low level eruptions where little can be seen on satellite imagery. Three aircraft encounters occurred over Micronesia without the source of the volcanic cloud being identified. While International Airways Volcano Watch performance is steadily improving, there are still significant scientific and procedural concerns highlighted by the above cases.

Thunderstorms and the associated weather have a range of impacts on operations at airports that i... more Thunderstorms and the associated weather have a range of impacts on operations at airports that include disruption to air traffic and also to ground operations. Lightning in particular presents a hazard to ground staff and procedures have been developed to ensure safe operations. This includes the provision of alerts when thunderstorms and associated lightning are present in the vicinity of designated airports. Various ground operations cease for the duration of the alert with the result that aircraft docking and associated procedures effectively cease. The flow-on disruption can last for many hours and extend around the country as aircraft cannot be unloaded and refuelled, they cannot leave parking bays and arriving aircraft have no place to park. Manual thunderstorm alerts were prepared in the past but the efficacy was limited because they tended to be conservative and did not provide real-time information on the shortterm variations that can occur during periods of thunderstorms....

SAE International Journal of Aerospace

Journal of Geophysical Research: Atmospheres

Bulletin of the American Meteorological Society

In the past two decades, more than 150 jet engine power-loss and damage events have been attribut... more In the past two decades, more than 150 jet engine power-loss and damage events have been attributed to a phenomenon known as ice crystal icing (ICI). Ingestion of large numbers of ice particles into the engine core are thought to be responsible for these events, which typically occur at high altitudes near large convective systems in tropical air masses. In recent years, scientists, engineers, aviation regulators, and airlines from around the world have collaborated to better understand the relevant meteorological processes associated with ICI events, solve critical engineering problems, develop new certification standards, and devise mitigation strategies for the aviation industry. One area of research is the development of nowcasting techniques based on available remote sensing technology and numerical weather prediction (NWP) models to identify areas of high ice water content (IWC) and enable the provision of alerts to the aviation industry. Multiple techniques have been develope...

Journal of Geophysical Research: Atmospheres