Design of subsea cables/umbilicals for in-service abrasion - part 1 : case studies
- Reda, Ahmed, Thiedeman, James, Elgazzar, Mohamed, Shahin, Mohamed, Sultan, Ibrahim, McKee, Kristoffer
- Authors: Reda, Ahmed , Thiedeman, James , Elgazzar, Mohamed , Shahin, Mohamed , Sultan, Ibrahim , McKee, Kristoffer
- Date: 2021
- Type: Text , Journal article
- Relation: Ocean Engineering Vol. 234, no. (2021), p.
- Full Text:
- Reviewed:
- Description: Submarine cables play a vital role in a myriad of industries around the globe, including power transmission and communication. Failure of submarine cables can have significant economic and technical implications worldwide. Current design methods for submarine cables focus on the ultimate limit states that address the cables structural integrity and on-bottom stability. However, abrasion of the outer protective layers (i.e. yarn and extruded sheaths) can progressively lead to damage and failure of submarine cables when the integrity of the armour sheathing is compromised. This paper documents several case studies of severe abrasion of submarine cables/umbilicals and undertaken corrective measures. The paper also presents some guidelines to be considered in the design process of submarine cables concerning abrasion. The findings of this paper suggest that abrasion should be considered a limit state that must be addressed in the design process of submarine cables and umbilicals. A detailed analysis of the underlying abrasion failure mechanisms is presented and explained in a companion paper (i.e., Part II: Mechanisms). © 2021 Elsevier Ltd
- Authors: Reda, Ahmed , Thiedeman, James , Elgazzar, Mohamed , Shahin, Mohamed , Sultan, Ibrahim , McKee, Kristoffer
- Date: 2021
- Type: Text , Journal article
- Relation: Ocean Engineering Vol. 234, no. (2021), p.
- Full Text:
- Reviewed:
- Description: Submarine cables play a vital role in a myriad of industries around the globe, including power transmission and communication. Failure of submarine cables can have significant economic and technical implications worldwide. Current design methods for submarine cables focus on the ultimate limit states that address the cables structural integrity and on-bottom stability. However, abrasion of the outer protective layers (i.e. yarn and extruded sheaths) can progressively lead to damage and failure of submarine cables when the integrity of the armour sheathing is compromised. This paper documents several case studies of severe abrasion of submarine cables/umbilicals and undertaken corrective measures. The paper also presents some guidelines to be considered in the design process of submarine cables concerning abrasion. The findings of this paper suggest that abrasion should be considered a limit state that must be addressed in the design process of submarine cables and umbilicals. A detailed analysis of the underlying abrasion failure mechanisms is presented and explained in a companion paper (i.e., Part II: Mechanisms). © 2021 Elsevier Ltd
Design of subsea cables/umbilicals for in-service abrasion - part 2 : mechanisms
- Reda, Ahmed, Elgazzar, Mohamed, Thiedeman, James, McKee, Kristoffer, Sultan, Ibrahim, Shahin, Mohamed
- Authors: Reda, Ahmed , Elgazzar, Mohamed , Thiedeman, James , McKee, Kristoffer , Sultan, Ibrahim , Shahin, Mohamed
- Date: 2021
- Type: Text , Journal article
- Relation: Ocean Engineering Vol. 234, no. (2021), p.
- Full Text:
- Reviewed:
- Description: This paper is the second of two companion papers about the design of subsea cables/umbilicals for in-service abrasion. Several case studies of severe abrasion of submarine cables/umbilicals and corrective measures undertaken have been documented and presented in the first paper (Part I: Case Studies). The mechanisms of failure due to abrasion are explained in this paper. The effect of repeated lateral movement on LLDPE (linear low-density polyethylene) extruded outer sheaths of two cable samples was investigated. In the first test, a cable sample was displaced the equivalent of 12 km over a crushed mineral aggregate while in the second test, a cable was subjected to 3 km of displacement under conditions that replicated the touchdown point of a dynamic cable. The results of the first test indicated that the overall abrasion was low and acceptable. In the second test however, the outer sheath was completely worn through. The authors recommend the thickness of the outer sheath be increased for cables where uniform abrasion is expected, and high abrasion protection units be employed where localized abrasion is expected. Empirical data is provided to support these recommendations. © 2021 Elsevier Ltd
- Authors: Reda, Ahmed , Elgazzar, Mohamed , Thiedeman, James , McKee, Kristoffer , Sultan, Ibrahim , Shahin, Mohamed
- Date: 2021
- Type: Text , Journal article
- Relation: Ocean Engineering Vol. 234, no. (2021), p.
- Full Text:
- Reviewed:
- Description: This paper is the second of two companion papers about the design of subsea cables/umbilicals for in-service abrasion. Several case studies of severe abrasion of submarine cables/umbilicals and corrective measures undertaken have been documented and presented in the first paper (Part I: Case Studies). The mechanisms of failure due to abrasion are explained in this paper. The effect of repeated lateral movement on LLDPE (linear low-density polyethylene) extruded outer sheaths of two cable samples was investigated. In the first test, a cable sample was displaced the equivalent of 12 km over a crushed mineral aggregate while in the second test, a cable was subjected to 3 km of displacement under conditions that replicated the touchdown point of a dynamic cable. The results of the first test indicated that the overall abrasion was low and acceptable. In the second test however, the outer sheath was completely worn through. The authors recommend the thickness of the outer sheath be increased for cables where uniform abrasion is expected, and high abrasion protection units be employed where localized abrasion is expected. Empirical data is provided to support these recommendations. © 2021 Elsevier Ltd
- Reda, Ahmed, Elgazzar, Mohamed, Sultan, Ibrahim, Shahin, Mohamed, McKee, Kristoffer
- Authors: Reda, Ahmed , Elgazzar, Mohamed , Sultan, Ibrahim , Shahin, Mohamed , McKee, Kristoffer
- Date: 2021
- Type: Text , Journal article
- Relation: Applied Ocean Research Vol. 115, no. (2021), p.
- Full Text: false
- Reviewed:
- Description: While subsea crossings are undesirable for many reasons, they are unavoidable due to the sheer density of subsea assets. The use of articulated paddings is a cost-effective and practical method to achieve the required vertical separation between the crossing and the crossed pipelines or cables, though, not without limitations. In this paper, the failure of articulated padding at several points along a subsea cable in operation was investigated. The articulated padding has experienced partial fractures at numerous crossing locations and in some places has fallen off the cable completely. A complete failure mode analysis was conducted where several possible modes of failure were considered in detail. In-place finite element (FE) analyses of the articulated padding components and the corresponding environment were also performed. The FE modelling concluded that the original design loads were significantly lower than the expected worst-case load scenarios. To replicate the failure mode, two abrasion tests were also conducted and the results of which were studied. It was concluded that the predominant failure mode (partial fracture to the articulated padding discs) was likely a combination of the increased dynamic loads, excessive lateral movement causing unexpected levels of fretting, unbalanced free span causing unexpected stress concentration factors and reduction in material mechanical properties. All above factors have contributed to the root cause of the system failure and instigated the predominant mode of failure “partial fracture”. © 2021
Tropical cyclone contribution to extreme rainfall over southwest Pacific Island nations
- Deo, Anil, Chand, Savin, Ramsay, Hamish, Holbrook, Neil, McGree, Simon
- Authors: Deo, Anil , Chand, Savin , Ramsay, Hamish , Holbrook, Neil , McGree, Simon
- Date: 2021
- Type: Text , Journal article
- Relation: Climate Dynamics Vol. 56, no. 11-12 (2021), p. 3967-3993
- Full Text:
- Reviewed:
- Description: Southwest Pacific nations are among some of the worst impacted and most vulnerable globally in terms of tropical cyclone (TC)-induced flooding and accompanying risks. This study objectively quantifies the fractional contribution of TCs to extreme rainfall (hereafter, TC contributions) in the context of climate variability and change. We show that TC contributions to extreme rainfall are substantially enhanced during active phases of the Madden–Julian Oscillation and by El Niño conditions (particularly over the eastern southwest Pacific region); this enhancement is primarily attributed to increased TC activity during these event periods. There are also indications of increasing intensities of TC-induced extreme rainfall events over the past few decades. A key part of this work involves development of sophisticated Bayesian regression models for individual island nations in order to better understand the synergistic relationships between TC-induced extreme rainfall and combinations of various climatic drivers that modulate the relationship. Such models are found to be very useful for not only assessing probabilities of TC- and non-TC induced extreme rainfall events but also evaluating probabilities of extreme rainfall for cases with different underlying climatic conditions. For example, TC-induced extreme rainfall probability over Samoa can vary from ~ 95 to ~ 75% during a La Niña period, if it coincides with an active or inactive phase of the MJO, and can be reduced to ~ 30% during a combination of El Niño period and inactive phase of the MJO. Several other such cases have been assessed for different island nations, providing information that have potentially important implications for planning and preparing for TC risks in vulnerable Pacific Island nations. © 2021, The Author(s). *Please note that there are multiple authors for this article therefore only the name of the first 5 including Federation University Australia affiliate “Anil Deo and Savin Chand” is provided in this record**
- Authors: Deo, Anil , Chand, Savin , Ramsay, Hamish , Holbrook, Neil , McGree, Simon
- Date: 2021
- Type: Text , Journal article
- Relation: Climate Dynamics Vol. 56, no. 11-12 (2021), p. 3967-3993
- Full Text:
- Reviewed:
- Description: Southwest Pacific nations are among some of the worst impacted and most vulnerable globally in terms of tropical cyclone (TC)-induced flooding and accompanying risks. This study objectively quantifies the fractional contribution of TCs to extreme rainfall (hereafter, TC contributions) in the context of climate variability and change. We show that TC contributions to extreme rainfall are substantially enhanced during active phases of the Madden–Julian Oscillation and by El Niño conditions (particularly over the eastern southwest Pacific region); this enhancement is primarily attributed to increased TC activity during these event periods. There are also indications of increasing intensities of TC-induced extreme rainfall events over the past few decades. A key part of this work involves development of sophisticated Bayesian regression models for individual island nations in order to better understand the synergistic relationships between TC-induced extreme rainfall and combinations of various climatic drivers that modulate the relationship. Such models are found to be very useful for not only assessing probabilities of TC- and non-TC induced extreme rainfall events but also evaluating probabilities of extreme rainfall for cases with different underlying climatic conditions. For example, TC-induced extreme rainfall probability over Samoa can vary from ~ 95 to ~ 75% during a La Niña period, if it coincides with an active or inactive phase of the MJO, and can be reduced to ~ 30% during a combination of El Niño period and inactive phase of the MJO. Several other such cases have been assessed for different island nations, providing information that have potentially important implications for planning and preparing for TC risks in vulnerable Pacific Island nations. © 2021, The Author(s). *Please note that there are multiple authors for this article therefore only the name of the first 5 including Federation University Australia affiliate “Anil Deo and Savin Chand” is provided in this record**
Guidelines for safe cable crossing over a pipeline
- Reda, Ahmed, Rawlinson, Andrew, Sultan, Ibrahim, Elgazzar, Mohammed, Howard, Ian
- Authors: Reda, Ahmed , Rawlinson, Andrew , Sultan, Ibrahim , Elgazzar, Mohammed , Howard, Ian
- Date: 2020
- Type: Text , Journal article
- Relation: Applied Ocean Research Vol. 102, no. (2020), p.
- Full Text:
- Reviewed:
- Description: High voltage submarine cables are increasingly being installed in existing and new offshore oil and gas fields for power supply and control purposes. These power cables are both large and with a high submerged weight, which poses a challenge when designing a safe, maintenance free (economical), and fit-for-purpose crossing over a pipeline. Damage to subsea pipeline crossings caused by deterioration of a crossing support, field joint materials and cover components is well known in the industry, particularly with old pipelines. Crossing cables over an existing pipeline should be avoided whenever economical and practical. However, it is inevitable in some situations to use the existing pipeline (unburied) as the crossing support to a new cable/umbilical. In these situations, crossing the cable/umbilical over the existing pipeline may be a cost-effective and worthy consideration. However, there are no explicit guidelines or criteria in the industry concerning the acceptable practice of design and construction of crossings. The only clear recommendation is relating to pipeline separation distances. This paper documents a recent case study of damage of a field joint coating at a crossing of an existing pipeline by a 132 kV subsea cable of 191 mm outside diameter. Investigation of the damage on site revealed that it was caused by lateral movement of the cable under the influence of hydrodynamic forces. Further to investigation and assessment of the damage of the case study presented here, the paper proposes some guidelines for the safe design and construction of cable crossing. Another objective of this paper is to invite further evaluation of the proposed guidelines so that appropriate crossing design requirements can be further developed and standardised. © 2020 Elsevier Ltd
- Authors: Reda, Ahmed , Rawlinson, Andrew , Sultan, Ibrahim , Elgazzar, Mohammed , Howard, Ian
- Date: 2020
- Type: Text , Journal article
- Relation: Applied Ocean Research Vol. 102, no. (2020), p.
- Full Text:
- Reviewed:
- Description: High voltage submarine cables are increasingly being installed in existing and new offshore oil and gas fields for power supply and control purposes. These power cables are both large and with a high submerged weight, which poses a challenge when designing a safe, maintenance free (economical), and fit-for-purpose crossing over a pipeline. Damage to subsea pipeline crossings caused by deterioration of a crossing support, field joint materials and cover components is well known in the industry, particularly with old pipelines. Crossing cables over an existing pipeline should be avoided whenever economical and practical. However, it is inevitable in some situations to use the existing pipeline (unburied) as the crossing support to a new cable/umbilical. In these situations, crossing the cable/umbilical over the existing pipeline may be a cost-effective and worthy consideration. However, there are no explicit guidelines or criteria in the industry concerning the acceptable practice of design and construction of crossings. The only clear recommendation is relating to pipeline separation distances. This paper documents a recent case study of damage of a field joint coating at a crossing of an existing pipeline by a 132 kV subsea cable of 191 mm outside diameter. Investigation of the damage on site revealed that it was caused by lateral movement of the cable under the influence of hydrodynamic forces. Further to investigation and assessment of the damage of the case study presented here, the paper proposes some guidelines for the safe design and construction of cable crossing. Another objective of this paper is to invite further evaluation of the proposed guidelines so that appropriate crossing design requirements can be further developed and standardised. © 2020 Elsevier Ltd
Projected changes in ENSO-driven regional tropical cyclone tracks
- Bell, Samuel, Chand, Savin, Turville, Christopher
- Authors: Bell, Samuel , Chand, Savin , Turville, Christopher
- Date: 2020
- Type: Text , Journal article
- Relation: Climate Dynamics Vol. 54, no. 3-4 (Feb 2020), p. 2533-2559
- Full Text:
- Reviewed:
- Description: Simulations and projections of the El Nino Southern Oscillation's (ENSO's) influence on TC track variability was analysed globally using Coupled Model Intercomparison project Phase 5 (CMIP5) models. The ability of these models to simulate the historical (1970-2000) ENSO-TC track relationship and inform us of the likely projected changes resulting from high carbon emissions (RCP8.5) in a climate projection (2070-2100) was determined through cluster analysis. The number of seasonal TC occurrences during traditional ENSO events ("El Nino" and "La Nina") in each cluster were used to determine whether each cluster was "El Nino dominant", "La Nina dominant" or "neither". Only seven out of a combined total of 28 clusters across all basins were found to disagree in terms of "ENSO dominance" between the observed records and historical model simulations. This suggests that models can simulate the ENSO and TC track relationship reasonably well. Under sustained high carbon emissions, La Nina TCs were projected to become dominant over El Nino TCs in the central South Indian Ocean ( 60-100 degrees E), the southern Bay of Bengal and over straight-moving TCs in the South China Sea. El Nino TCs were projected to increase and become dominant over La Nina TCs in a larger area of the western South Pacific ( 160 degrees E-165 degrees W) and central North Pacific ( 160 degrees E-145 degrees W) Oceans. Projections of track directions and lifetimes, while less robust, indicated that El Nino TCs would track westward more often in the Coral Sea (150-165 degrees E), while El Nino TCs that took an eastward track here would have longer lifetimes ( 3 days).
- Authors: Bell, Samuel , Chand, Savin , Turville, Christopher
- Date: 2020
- Type: Text , Journal article
- Relation: Climate Dynamics Vol. 54, no. 3-4 (Feb 2020), p. 2533-2559
- Full Text:
- Reviewed:
- Description: Simulations and projections of the El Nino Southern Oscillation's (ENSO's) influence on TC track variability was analysed globally using Coupled Model Intercomparison project Phase 5 (CMIP5) models. The ability of these models to simulate the historical (1970-2000) ENSO-TC track relationship and inform us of the likely projected changes resulting from high carbon emissions (RCP8.5) in a climate projection (2070-2100) was determined through cluster analysis. The number of seasonal TC occurrences during traditional ENSO events ("El Nino" and "La Nina") in each cluster were used to determine whether each cluster was "El Nino dominant", "La Nina dominant" or "neither". Only seven out of a combined total of 28 clusters across all basins were found to disagree in terms of "ENSO dominance" between the observed records and historical model simulations. This suggests that models can simulate the ENSO and TC track relationship reasonably well. Under sustained high carbon emissions, La Nina TCs were projected to become dominant over El Nino TCs in the central South Indian Ocean ( 60-100 degrees E), the southern Bay of Bengal and over straight-moving TCs in the South China Sea. El Nino TCs were projected to increase and become dominant over La Nina TCs in a larger area of the western South Pacific ( 160 degrees E-165 degrees W) and central North Pacific ( 160 degrees E-145 degrees W) Oceans. Projections of track directions and lifetimes, while less robust, indicated that El Nino TCs would track westward more often in the Coral Sea (150-165 degrees E), while El Nino TCs that took an eastward track here would have longer lifetimes ( 3 days).
- Bell, Samuel, Chand, Savin, Tory, Kevin, Turville, Christopher, Ye, Harvey
- Authors: Bell, Samuel , Chand, Savin , Tory, Kevin , Turville, Christopher , Ye, Harvey
- Date: 2019
- Type: Text , Journal article
- Relation: Climate Dynamics Vol. 53, no. 7-8 (2019), p. 4841-4855
- Full Text: false
- Reviewed:
- Description: The sensitivity of tropical cyclone (TC) projection results to different models and the detection and tracking scheme used is well established in the literature. Here, future climate projections of TC activity in the Eastern North Pacific basin (ENP, defined from 0 degrees to 40 degrees N and 180 degrees to similar to 75 degrees W) are assessed with a model- and basin-independent detection and tracking scheme that was trained in reanalysis data. The scheme is applied to models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) experiments forced under the historical and Representative Concentration Pathway 8.5 (RCP8.5) conditions. TC tracks from the observed records and models are analysed simultaneously with a curve-clustering algorithm, allowing observed and model tracks to be projected onto the same set of clusters. The ENP is divided into three clusters, one in the Central North Pacific (CNP) and two off the Mexican coast, as in prior studies. After accounting for model biases and auto-correlation, projection results under RCP8.5 indicated TC genesis to be significantly suppressed east of 125 degrees W, and significantly enhanced west of 145 degrees W by the end of the twenty-first century. Regional TC track exposure was found to significantly increase around Hawaii (similar to 86%), as shown in earlier studies, owing to increased TC genesis, particularly to the south-east of the island nation. TC exposure to Southern Mexico was shown to decrease (similar to 4%), owing to a south-westward displacement of TCs and overall suppression of genesis near the Mexican coastline. The large-scale environmental conditions most consistent with these projected changes were vertical wind shear and relative humidity.
Happy feet in a hostile world? The future of penguins depends on proactive management of current and expected threats
- Ropert-Coudert, Yan, Chiaradia, Andre, Ainley, David, Barbosa, Andres, Boersma, Dee, Brasso, Rebecka, Dewar, Meagan, Ellenberg, Ursula, García-Borboroglu, Pablo, Emmerson, Loulse, Hickcox, Rachel, Jenouvrier, Stephanie, Kato, Akiko, McIntosh, Rebecca, Lewis, Phoebe, Ramírez, Francisco, Ruoppolo, Valeria, Ryan, Peter, Seddon, Philip, Sherley, Richard, Vanstreels, Ralph, Waller, Lauren, Woehler, Eric, Trathan, Phil
- Authors: Ropert-Coudert, Yan , Chiaradia, Andre , Ainley, David , Barbosa, Andres , Boersma, Dee , Brasso, Rebecka , Dewar, Meagan , Ellenberg, Ursula , García-Borboroglu, Pablo , Emmerson, Loulse , Hickcox, Rachel , Jenouvrier, Stephanie , Kato, Akiko , McIntosh, Rebecca , Lewis, Phoebe , Ramírez, Francisco , Ruoppolo, Valeria , Ryan, Peter , Seddon, Philip , Sherley, Richard , Vanstreels, Ralph , Waller, Lauren , Woehler, Eric , Trathan, Phil
- Date: 2019
- Type: Text , Journal article
- Relation: Frontiers in Marine Science Vol. 6, no. May (2019), p. 1-23
- Full Text:
- Reviewed:
- Description: Penguins face a wide range of threats. Most observed population changes have been negative and have happened over the last 60 years. Today, populations of 11 penguin species are decreasing. Here we present a review that synthesizes details of threats faced by the world's 18 species of penguins. We discuss alterations to their environment at both breeding sites on land and at sea where they forage. The major drivers of change appear to be climate, and food web alterations by marine fisheries. In addition, we also consider other critical and/or emerging threats, namely human disturbance near nesting sites, pollution due to oil, plastics and chemicals such as mercury and persistent organic compounds. Finally, we assess the importance of emerging pathogens and diseases on the health of penguins. We suggest that in the context of climate change, habitat degradation, introduced exotic species and resource competition with fisheries, successful conservation outcomes will require new and unprecedented levels of science and advocacy. Successful conservation stories of penguin species across their geographical range have occurred where there has been concerted effort across local, national and international boundaries to implement effective conservation planning.
- Authors: Ropert-Coudert, Yan , Chiaradia, Andre , Ainley, David , Barbosa, Andres , Boersma, Dee , Brasso, Rebecka , Dewar, Meagan , Ellenberg, Ursula , García-Borboroglu, Pablo , Emmerson, Loulse , Hickcox, Rachel , Jenouvrier, Stephanie , Kato, Akiko , McIntosh, Rebecca , Lewis, Phoebe , Ramírez, Francisco , Ruoppolo, Valeria , Ryan, Peter , Seddon, Philip , Sherley, Richard , Vanstreels, Ralph , Waller, Lauren , Woehler, Eric , Trathan, Phil
- Date: 2019
- Type: Text , Journal article
- Relation: Frontiers in Marine Science Vol. 6, no. May (2019), p. 1-23
- Full Text:
- Reviewed:
- Description: Penguins face a wide range of threats. Most observed population changes have been negative and have happened over the last 60 years. Today, populations of 11 penguin species are decreasing. Here we present a review that synthesizes details of threats faced by the world's 18 species of penguins. We discuss alterations to their environment at both breeding sites on land and at sea where they forage. The major drivers of change appear to be climate, and food web alterations by marine fisheries. In addition, we also consider other critical and/or emerging threats, namely human disturbance near nesting sites, pollution due to oil, plastics and chemicals such as mercury and persistent organic compounds. Finally, we assess the importance of emerging pathogens and diseases on the health of penguins. We suggest that in the context of climate change, habitat degradation, introduced exotic species and resource competition with fisheries, successful conservation outcomes will require new and unprecedented levels of science and advocacy. Successful conservation stories of penguin species across their geographical range have occurred where there has been concerted effort across local, national and international boundaries to implement effective conservation planning.
Projections of southern hemisphere tropical cyclone track density using CMIP5 models
- Bell, Samuel, Chand, Savin, Tory, Kevin, Dowdy, Andrew, Turville, Christopher, Ye, Harvey
- Authors: Bell, Samuel , Chand, Savin , Tory, Kevin , Dowdy, Andrew , Turville, Christopher , Ye, Harvey
- Date: 2019
- Type: Text , Journal article
- Relation: Climate Dynamics Vol. 52, no. 9-10 (2019), p. 6065-6079
- Full Text:
- Reviewed:
- Description: A recently validated algorithm for detecting and tracking tropical cyclones (TCs) in coarse resolution climate models was applied to a selected group of 12 models from the Coupled Model Intercomparison Project (CMIP5) to assess potential changes in TC track characteristics in the Southern Hemisphere (SH) due to greenhouse warming. Current-climate simulations over the period 1970–2000 are first evaluated against observations using measures of TC genesis location and frequency, as well as track trajectory and lifetime in seven objectively defined genesis regions. The 12-model (12-M) ensemble showed substantial skill in reproducing a realistic TC climatology over the evaluation period. To address potential biases associated with model interdependency, analyses were repeated with an ensemble of five independent models (5-M). Results from both the 12-M and 5-M ensembles were very similar, instilling confidence in the models for climate projections if the current TC-climate relationship is to remain stationary. Projected changes in TC track density between the current- and future-climate (2070–2100) simulations under the Representatives Concentration 8.5 Pathways (RCP8.5) are also assessed. Overall, projection results showed a substantial decrease (~ 1–3 per decade) in track density over most parts of the SH by the end of the twenty-first century. This decrease is attributed to a significant reduction in TC numbers (~ 15–42%) consistent with changes in large-scale environmental parameters such as relative vorticity, environmental vertical wind shear and relative humidity. This study may assist with adaption pathways and implications for regional-scale climate change for vulnerable regions in the SH.
- Authors: Bell, Samuel , Chand, Savin , Tory, Kevin , Dowdy, Andrew , Turville, Christopher , Ye, Harvey
- Date: 2019
- Type: Text , Journal article
- Relation: Climate Dynamics Vol. 52, no. 9-10 (2019), p. 6065-6079
- Full Text:
- Reviewed:
- Description: A recently validated algorithm for detecting and tracking tropical cyclones (TCs) in coarse resolution climate models was applied to a selected group of 12 models from the Coupled Model Intercomparison Project (CMIP5) to assess potential changes in TC track characteristics in the Southern Hemisphere (SH) due to greenhouse warming. Current-climate simulations over the period 1970–2000 are first evaluated against observations using measures of TC genesis location and frequency, as well as track trajectory and lifetime in seven objectively defined genesis regions. The 12-model (12-M) ensemble showed substantial skill in reproducing a realistic TC climatology over the evaluation period. To address potential biases associated with model interdependency, analyses were repeated with an ensemble of five independent models (5-M). Results from both the 12-M and 5-M ensembles were very similar, instilling confidence in the models for climate projections if the current TC-climate relationship is to remain stationary. Projected changes in TC track density between the current- and future-climate (2070–2100) simulations under the Representatives Concentration 8.5 Pathways (RCP8.5) are also assessed. Overall, projection results showed a substantial decrease (~ 1–3 per decade) in track density over most parts of the SH by the end of the twenty-first century. This decrease is attributed to a significant reduction in TC numbers (~ 15–42%) consistent with changes in large-scale environmental parameters such as relative vorticity, environmental vertical wind shear and relative humidity. This study may assist with adaption pathways and implications for regional-scale climate change for vulnerable regions in the SH.
Variation in growing season water balance in central Victoria, Australia, in relation to large-scale climate drivers
- Authors: Marshall, Adam
- Date: 2019
- Type: Text , Journal article
- Relation: Journal of Southern Hemisphere Earth Systems Science Vol. 69, no. 1 (2019), p. 131-145
- Full Text:
- Reviewed:
- Description: The precipitation and evaporation records from 1972 to 2013 were analysed at five stations in central Victoria, Australia. The stations formed a north-south transect of sites across a distinct climatic gradient spanning the dry inland plains, the Great Dividing Range and the southern coastal zone. The focus was on the March November 'Growing Season' when typically higher available moisture is critical for a variety of agricultural practices and water management across the region. Growing season rainfall trends were fairly consistent across all stations with ongoing declines generally observed in all months with the exception of November, with the most notable declines in April, May and October. Pan evaporation recorded display greater variation between stations with both significant positive and negative trends evident within the season across the station network. The influence of El Nino Southern Oscillation and Indian Ocean Dipole on rainfall and pan evaporation was statistically significant, increasing through winter and peaking in spring at all stations. The Southern Annular Mode displayed marked intraseasonal influence which appeared to be highly location dependent. Interestingly, the tropical climate drivers displayed a stronger relationship with pan evaporation than rainfall over the analysis period. This highlighted the potential benefits of taking a broader terrestrial water balance (TWB) perspective of both pan evaporation and rainfall, a concept previously termed 'Effective Rainfall'. Critically, this study shows the importance of understanding regional variation in TWB elements with respect to local topography and geographic location, as well as intraseasonal variations within the overall growing season.
- Authors: Marshall, Adam
- Date: 2019
- Type: Text , Journal article
- Relation: Journal of Southern Hemisphere Earth Systems Science Vol. 69, no. 1 (2019), p. 131-145
- Full Text:
- Reviewed:
- Description: The precipitation and evaporation records from 1972 to 2013 were analysed at five stations in central Victoria, Australia. The stations formed a north-south transect of sites across a distinct climatic gradient spanning the dry inland plains, the Great Dividing Range and the southern coastal zone. The focus was on the March November 'Growing Season' when typically higher available moisture is critical for a variety of agricultural practices and water management across the region. Growing season rainfall trends were fairly consistent across all stations with ongoing declines generally observed in all months with the exception of November, with the most notable declines in April, May and October. Pan evaporation recorded display greater variation between stations with both significant positive and negative trends evident within the season across the station network. The influence of El Nino Southern Oscillation and Indian Ocean Dipole on rainfall and pan evaporation was statistically significant, increasing through winter and peaking in spring at all stations. The Southern Annular Mode displayed marked intraseasonal influence which appeared to be highly location dependent. Interestingly, the tropical climate drivers displayed a stronger relationship with pan evaporation than rainfall over the analysis period. This highlighted the potential benefits of taking a broader terrestrial water balance (TWB) perspective of both pan evaporation and rainfall, a concept previously termed 'Effective Rainfall'. Critically, this study shows the importance of understanding regional variation in TWB elements with respect to local topography and geographic location, as well as intraseasonal variations within the overall growing season.
Western north pacific tropical cyclone tracks in cmip5 models : statistical assessment using a model-independent detection and tracking scheme
- Bell, Samuel, Chand, Savin, Camargo, Suzana, Tory, Kevin, Turville, Chris, Ye, Harvey
- Authors: Bell, Samuel , Chand, Savin , Camargo, Suzana , Tory, Kevin , Turville, Chris , Ye, Harvey
- Date: 2019
- Type: Text , Journal article
- Relation: Journal of Climate Vol. 32, no. 21 (2019), p. 7191-7208
- Full Text:
- Reviewed:
- Description: Past studies have shown that tropical cyclone (TC) projection results can be sensitive to different types of TC tracking schemes, and that the relative adjustments of detection criteria to accommodate different models may not necessarily provide a consistent platform for comparison of projection results. Here, future climate projections of TC activity in the western North Pacific basin (WNP, defined from 0°-50°NAND 100°E-180°) are assessed with a model-independent detection and tracking scheme. This scheme is applied to models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) forced under the historical and representative concentration pathway 8.5 (RCP8.5) conditions. TC tracks from the observed records and independent models are analyzed simultaneously with a curve-clustering algorithm, allowing observed and model tracks to be projected onto the same set of clusters (k =9). Four of the nine clusters were projected to undergo significant changes in TC frequency. Straight-moving TCs in the South China Sea were projected to significantly decrease. Projected increases in TC frequency were found poleward of 20°N and east of 160°E, consistent with changes in ascending motion, as well as vertical wind shear and relative humidity respectively. Projections of TC track exposure indicated significant reductions for southern China and the Philippines and significant increases for the Korean peninsula and Japan, although very few model TCs reached the latter subtropical regions in comparison to the observations. The use of a fundamentally different detection methodology that overcomes the detector/tracker bias gives increased certainty to projections as best as lowresolution simulations can offer. © 2019 American Meteorological Society.
- Authors: Bell, Samuel , Chand, Savin , Camargo, Suzana , Tory, Kevin , Turville, Chris , Ye, Harvey
- Date: 2019
- Type: Text , Journal article
- Relation: Journal of Climate Vol. 32, no. 21 (2019), p. 7191-7208
- Full Text:
- Reviewed:
- Description: Past studies have shown that tropical cyclone (TC) projection results can be sensitive to different types of TC tracking schemes, and that the relative adjustments of detection criteria to accommodate different models may not necessarily provide a consistent platform for comparison of projection results. Here, future climate projections of TC activity in the western North Pacific basin (WNP, defined from 0°-50°NAND 100°E-180°) are assessed with a model-independent detection and tracking scheme. This scheme is applied to models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) forced under the historical and representative concentration pathway 8.5 (RCP8.5) conditions. TC tracks from the observed records and independent models are analyzed simultaneously with a curve-clustering algorithm, allowing observed and model tracks to be projected onto the same set of clusters (k =9). Four of the nine clusters were projected to undergo significant changes in TC frequency. Straight-moving TCs in the South China Sea were projected to significantly decrease. Projected increases in TC frequency were found poleward of 20°N and east of 160°E, consistent with changes in ascending motion, as well as vertical wind shear and relative humidity respectively. Projections of TC track exposure indicated significant reductions for southern China and the Philippines and significant increases for the Korean peninsula and Japan, although very few model TCs reached the latter subtropical regions in comparison to the observations. The use of a fundamentally different detection methodology that overcomes the detector/tracker bias gives increased certainty to projections as best as lowresolution simulations can offer. © 2019 American Meteorological Society.
A statistical assessment of Southern Hemisphere tropical cyclone tracks in climate models
- Ramsay, Hamish, Chand, Savin, Camargo, Suzana
- Authors: Ramsay, Hamish , Chand, Savin , Camargo, Suzana
- Date: 2018
- Type: Text , Journal article
- Relation: Journal of Climate Vol. 31, no. 24 (2018), p. 10081-10104
- Full Text:
- Reviewed:
- Description: Reliable projections of future changes in tropical cyclone (TC) characteristics are highly dependent on the ability of global climate models (GCMs) to simulate the observed characteristics of TCs (i.e., their frequency, genesis locations, movement, and intensity). Here, we investigate the performance of a suite of GCMs from the U.S. CLIVAR Working Group on Hurricanes in simulating observed climatological features of TCs in the Southern Hemisphere. A subset of these GCMs is also explored under three idealized warming scenarios. Two types of simulated TC tracks are evaluated on the basis of a commonly applied cluster analysis: 1) explicitly simulated tracks, and 2) downscaled tracks, derived from a statistical-dynamical technique that depends on the models' large-scale environmental fields. Climatological TC properties such as genesis locations, annual frequency, lifetime maximum intensity (LMI), and seasonality are evaluated for both track types. Future changes to annual frequency, LMI, and the latitude of LMI are evaluated using the downscaled tracks where large sample sizes allow for statistically robust results. An ensemble approach is used to assess future changes of explicit tracks owing to their small number of realizations. We show that the downscaled tracks generally outperform the explicit tracks in relation to many of the climatological features of Southern Hemisphere TCs, despite a few notable biases. Future changes to the frequency and intensity of TCs in the downscaled simulations are found to be highly dependent on the warming scenario and model, with the most robust result being an increase in the LMI under a uniform 2°C surface warming.
- Authors: Ramsay, Hamish , Chand, Savin , Camargo, Suzana
- Date: 2018
- Type: Text , Journal article
- Relation: Journal of Climate Vol. 31, no. 24 (2018), p. 10081-10104
- Full Text:
- Reviewed:
- Description: Reliable projections of future changes in tropical cyclone (TC) characteristics are highly dependent on the ability of global climate models (GCMs) to simulate the observed characteristics of TCs (i.e., their frequency, genesis locations, movement, and intensity). Here, we investigate the performance of a suite of GCMs from the U.S. CLIVAR Working Group on Hurricanes in simulating observed climatological features of TCs in the Southern Hemisphere. A subset of these GCMs is also explored under three idealized warming scenarios. Two types of simulated TC tracks are evaluated on the basis of a commonly applied cluster analysis: 1) explicitly simulated tracks, and 2) downscaled tracks, derived from a statistical-dynamical technique that depends on the models' large-scale environmental fields. Climatological TC properties such as genesis locations, annual frequency, lifetime maximum intensity (LMI), and seasonality are evaluated for both track types. Future changes to annual frequency, LMI, and the latitude of LMI are evaluated using the downscaled tracks where large sample sizes allow for statistically robust results. An ensemble approach is used to assess future changes of explicit tracks owing to their small number of realizations. We show that the downscaled tracks generally outperform the explicit tracks in relation to many of the climatological features of Southern Hemisphere TCs, despite a few notable biases. Future changes to the frequency and intensity of TCs in the downscaled simulations are found to be highly dependent on the warming scenario and model, with the most robust result being an increase in the LMI under a uniform 2°C surface warming.
Long-term dynamic behaviour of Coode Island Silt (CIS) containing different sand content
- Jamali, Hassan, Tolooiyan, Ali, Dehghani, Masoud, Asakereh, Adel, Kalantari, Behzad
- Authors: Jamali, Hassan , Tolooiyan, Ali , Dehghani, Masoud , Asakereh, Adel , Kalantari, Behzad
- Date: 2018
- Type: Text , Journal article
- Relation: Applied Ocean Research Vol. 73, no. (2018), p. 59-69
- Full Text: false
- Reviewed:
- Description: The foundations of nearshore and offshore structures are always subjected to long-term cyclic loading which is often a one-way, with low amplitude and a large number of cycles. Hence, the long-term dynamic behaviour of shoreline soils and sediments should be understood to avoid excessive deformation and liquefaction. As one of the most problematic soft soils in Melbourne, Coode Island Silt (CIS) at the northern shoreline of Port Phillip Bay contains a considerable but variable amount of sand. This paper explores the dynamic response of CIS containing different sand content subjected to a large number of cycles. To determine the liquefaction potential, and the effect of sand content on the resilient modulus and permanent strain of CIS, a series of long-term cyclic triaxial tests at a sinusoidal loading frequency of 1 Hz is performed. Based on the test results, it is found that CIS with varying sand content up to 30%, does not liquefy under the cyclic stress ratios and frequency applied in this study. Also, a sand content of 10% causes CIS to degrade more under cyclic loading. In the end, an empirical model to predict the permanent strain of CIS with a variable sand content is calibrated.
Post-long-term cyclic behaviour of Coode Island Silt (CIS) containing different sand content
- Jamali, Hassan, Tolooiyan, Ali, Dehghani, Masoud, Asakereh, Adel, Kalantari, Behzad
- Authors: Jamali, Hassan , Tolooiyan, Ali , Dehghani, Masoud , Asakereh, Adel , Kalantari, Behzad
- Date: 2018
- Type: Text , Journal article
- Relation: Applied Ocean Research Vol. 80, no. (2018), p. 11-23
- Full Text: false
- Reviewed:
- Description: It is widely accepted that the post-cyclic stiffness and shear strength of marine clays may alter as a consequence of experiencing a large number of deviatoric load cycles. Most marine clays in bay areas are already undergoing long-term one-way and low amplitude ocean and wind waves either because of the seabed topography or existing infrastructures. For the engineering of such clays, particular attention should be given to the post-cyclic behaviour of the material when investigating the effect of alteration in loading regimes exerted by human-made or natural phenomena such installation of new infrastructure, earthquake, tsunami and port upgrade construction, in which the magnitude of the applied load changes. As one of the most sensitive soft soils in Melbourne, Coode Island Silt (CIS) at the northern shoreline of Port Phillip Bay comprises a considerable and variable amount of sand. This paper explores the post-cyclic constitutive behaviour of CIS containing variable sand content. To investigate the stiffness and shear strength of CIS subsequent to experiencing a large number of low amplitude cycles, a series of post-cyclic triaxial tests are performed on CIS specimens with varying sand content ratio up to 30%, immediately after applying 30,000 semi-sinusoidal load cycles. Based on the test results, it is found that the undrained shear strength of CIS, does not alter considerably as the results of long-term cyclic loading. However, a significant increase in the secant stiffness of CIS followed by very brittle yielding is observed. In the end, it is intended that results be summarised in a form applicable by industry. Hence, the possible effects of such alterations in the constitutive behaviour of CIS on the design of monopile foundations are discussed.
Statistical assessment of the OWZ Tropical Cyclone Tracking Scheme in ERA-Interim
- Bell, Samuel, Chand, Savin, Tory, Kevin, Turville, Christopher
- Authors: Bell, Samuel , Chand, Savin , Tory, Kevin , Turville, Christopher
- Date: 2018
- Type: Text , Journal article
- Relation: Journal of Climate Vol. 31, no. 6 (2018), p. 2217-2232
- Full Text:
- Reviewed:
- Description: The Okubo–Weiss–Zeta (OWZ) tropical cyclone (TC) detection scheme, which has been used to detect TCs in climate, seasonal prediction, and weather forecast models, is assessed on its ability to produce a realistic TC track climatology in the ERA-Interim product over the 25-yr period 1989 to 2013. The analysis focuses on TCs that achieve gale-force (17ms21) sustained winds. Objective criteria were established to define TC tracks once they reach gale force for both observed and detected TCs. A lack of consistency between storm tracks preceding this level of intensity led these track segments to be removed from the analysis.Asubtropical jet (STJ) diagnostic is used to terminate transitioning TCs and is found to be preferable to a fixed latitude cutoff point. TC tracks were analyzed across seven TC basins, using a probabilistic clustering technique that is based on regression mixture models. The technique grouped TC tracks together based on their geographical location and shape of trajectory in five separate ‘‘cluster regions’’ around the globe. A mean trajectory was then regressed for each cluster that showed good agreement between the detected and observed tracks. Other track measures such as interannual TC days and translational speeds were also replicated to a satisfactory level, with TC days showing limited sensitivity to different latitude cutoff points. Successful validation in reanalysis data allows this model- and grid-resolution-independent TC tracking scheme to be applied to climate models with confidence in its ability to identify TC tracks in coarse-resolution climate models.
- Authors: Bell, Samuel , Chand, Savin , Tory, Kevin , Turville, Christopher
- Date: 2018
- Type: Text , Journal article
- Relation: Journal of Climate Vol. 31, no. 6 (2018), p. 2217-2232
- Full Text:
- Reviewed:
- Description: The Okubo–Weiss–Zeta (OWZ) tropical cyclone (TC) detection scheme, which has been used to detect TCs in climate, seasonal prediction, and weather forecast models, is assessed on its ability to produce a realistic TC track climatology in the ERA-Interim product over the 25-yr period 1989 to 2013. The analysis focuses on TCs that achieve gale-force (17ms21) sustained winds. Objective criteria were established to define TC tracks once they reach gale force for both observed and detected TCs. A lack of consistency between storm tracks preceding this level of intensity led these track segments to be removed from the analysis.Asubtropical jet (STJ) diagnostic is used to terminate transitioning TCs and is found to be preferable to a fixed latitude cutoff point. TC tracks were analyzed across seven TC basins, using a probabilistic clustering technique that is based on regression mixture models. The technique grouped TC tracks together based on their geographical location and shape of trajectory in five separate ‘‘cluster regions’’ around the globe. A mean trajectory was then regressed for each cluster that showed good agreement between the detected and observed tracks. Other track measures such as interannual TC days and translational speeds were also replicated to a satisfactory level, with TC days showing limited sensitivity to different latitude cutoff points. Successful validation in reanalysis data allows this model- and grid-resolution-independent TC tracking scheme to be applied to climate models with confidence in its ability to identify TC tracks in coarse-resolution climate models.
Compression limit state of HVAC submarine cables
- Reda, Ahmed, Forbes, Gareth, Al-Mahmoud, Faisal, Howard, Ian, McKee, Kristoffer, Sultan, Ibrahim
- Authors: Reda, Ahmed , Forbes, Gareth , Al-Mahmoud, Faisal , Howard, Ian , McKee, Kristoffer , Sultan, Ibrahim
- Date: 2016
- Type: Text , Journal article
- Relation: Applied Ocean Research Vol. 56, no. (2016), p. 12-34
- Full Text: false
- Reviewed:
- Description: An industry accepted standard does not currently exist for determination of compression limits in a subsea cable. This has resulted in most manufacturers specifying that subsea cables are not permitted to be axially loaded in compression.Additionally industry guidance does not exist regarding the consequences of inducing compression forces within subsea cables and the resulting effect on cable integrity. Industry recommended practice and guidance also does not have any information regarding experimental test arrangements to determine allowable compression levels within a subsea cable. This lack of modelling/testing guidance along with manufacturer recommendations of zero compressive loads within subsea cables results in overly conservative and restrictive design parameters for subsea cable installation and use.Due to the complex interaction within a subsea cable structure, such as contact interaction and friction between cable strands, theoretical modelling has been unable to provide reliable stress predictions and therefore an experimental testing regime is required if compression limits within the cable are to be appropriately determined. This paper describes combined axial and bending test arrangements that can be used as a guideline for determination of allowable compression limits for subsea cables. © 2016 Elsevier Ltd.
- Liu, Peng, Wang, Zhongtao, Li, Xinzhong, Chan, Andrew
- Authors: Liu, Peng , Wang, Zhongtao , Li, Xinzhong , Chan, Andrew
- Date: 2015
- Type: Text , Journal article
- Relation: Acta Oceanologica Sinica Vol. 34, no. 7 (2015), p. 105-115
- Full Text: false
- Reviewed:
- Description: Principal stress axes rotation influences the stress-strain behavior of sand under wave loading. A constitutive model for sand, which considers principal stress orientation and is based on generalized plasticity theory, is proposed. The new model, which employs stress invariants and a discrete memory factor during reloading, is original because it quantifies model parameters using experimental data. Four sets of hollow torsion experiments were conducted to calibrate the parameters and predict the capability of the proposed model, which describes the effects of principal stress orientation on the behavior of sand. The results prove the effectiveness of the proposed calibration method. © 2015, The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg.
An assessment of a model-, grid-, and basin-independent tropical cyclone detection scheme in selected CMIP3 global climate models
- Tory, Kevin, Chand, Savin, Dare, Richard, McBride, John
- Authors: Tory, Kevin , Chand, Savin , Dare, Richard , McBride, John
- Date: 2013
- Type: Text , Journal article
- Relation: Journal of Climate Vol. 26, no. 15 (2013), p. 5508-5522
- Full Text:
- Reviewed:
- Description: A novel tropical cyclone (TC) detection technique designed for coarse-resolution models is tested and evaluated. The detector, based on the Okubo-Weiss-Zeta parameter (OWZP), is applied to a selection of Coupled Model Intercomparison Project, phase 3 (CMIP3), models [Commonwealth Scientific and Industrial Research Organisation Mark, version 3.5 (CSIRO-Mk3.5); Max Planck Institute ECHAM5 (MPI-ECHAM5); and Geophysical Fluid Dynamics Laboratory Climate Model, versions 2.0 (GFDL CM2.0) and 2.1 (GFDL CM2.1)], and the combined performance of the model and detector is assessed by comparison with observed TC climatology for the period 1970-2000. Preliminary TC frequency projections are made using the three better-performing models by comparing the detected TC climatologies between the late twentieth and late twenty-first centuries. Very reasonable TC formation climatologies were detected in CSIRO-Mk3.5, MPI-ECHAM5, and GFDL CM2.1 for most basins, with the exception of the North Atlantic, where a large un-derdetection was present in all models. The GFDL CM2.0 model was excluded from the projection study because of a systematic underdetection in all basins. The above detection problems have been reported in other published studies, which suggests model rather than detector limitations are mostly responsible. This study demonstrates that coarse-resolution climate models do in general produce TC-like circulations with realistic geographical and seasonal distributions detectable by the OWZP TC detector. The preliminary projection results are consistent with the published literature, based on higher-resolution studies, of a global reductionofTCs between about6%and 20%, withamuch larger spread of results (about 120% to 250%) in individual basins. © 2013 American Meteorological Society.
- Authors: Tory, Kevin , Chand, Savin , Dare, Richard , McBride, John
- Date: 2013
- Type: Text , Journal article
- Relation: Journal of Climate Vol. 26, no. 15 (2013), p. 5508-5522
- Full Text:
- Reviewed:
- Description: A novel tropical cyclone (TC) detection technique designed for coarse-resolution models is tested and evaluated. The detector, based on the Okubo-Weiss-Zeta parameter (OWZP), is applied to a selection of Coupled Model Intercomparison Project, phase 3 (CMIP3), models [Commonwealth Scientific and Industrial Research Organisation Mark, version 3.5 (CSIRO-Mk3.5); Max Planck Institute ECHAM5 (MPI-ECHAM5); and Geophysical Fluid Dynamics Laboratory Climate Model, versions 2.0 (GFDL CM2.0) and 2.1 (GFDL CM2.1)], and the combined performance of the model and detector is assessed by comparison with observed TC climatology for the period 1970-2000. Preliminary TC frequency projections are made using the three better-performing models by comparing the detected TC climatologies between the late twentieth and late twenty-first centuries. Very reasonable TC formation climatologies were detected in CSIRO-Mk3.5, MPI-ECHAM5, and GFDL CM2.1 for most basins, with the exception of the North Atlantic, where a large un-derdetection was present in all models. The GFDL CM2.0 model was excluded from the projection study because of a systematic underdetection in all basins. The above detection problems have been reported in other published studies, which suggests model rather than detector limitations are mostly responsible. This study demonstrates that coarse-resolution climate models do in general produce TC-like circulations with realistic geographical and seasonal distributions detectable by the OWZP TC detector. The preliminary projection results are consistent with the published literature, based on higher-resolution studies, of a global reductionofTCs between about6%and 20%, withamuch larger spread of results (about 120% to 250%) in individual basins. © 2013 American Meteorological Society.
Impact of different ENSO regimes on southwest pacific tropical cyclones
- Chand, Savin, McBride, John, Tory, Kevin, Wheeler, Matthew, Walsh, Kevin
- Authors: Chand, Savin , McBride, John , Tory, Kevin , Wheeler, Matthew , Walsh, Kevin
- Date: 2013
- Type: Text , Journal article
- Relation: Journal of Climate Vol. 26, no. 2 (2013), p. 600-608
- Full Text: false
- Reviewed:
- Description: The influence of different types of ENSO on tropical cyclone (TC) interannual variability in the central southwest Pacific region (58-258S, 1708E-1708W) is investigated. Using empirical orthogonal function analysis and an agglomerative hierarchical clustering of early tropical cyclone season Pacific sea surface temperature, years are classified into four separate regimes (i.e., canonical El Niño, canonical La Niña, positive-neutral, and negative-neutral) for the period between 1970 and 2009.These regimes are found to have a large impact on TC genesis over the central southwest Pacific region. Both the canonical El Niño and the positive-neutral years have increased numbers of cyclones, with an average of 4.3 yr-1 for positive-neutral and 4 yr-1 for canonical El Niño. In contrast, during a La Niña and negative-neutral events, substantially fewer TCs (averages of ;2.2 and 2.4 yr-1, respectively) are observed in the central southwest Pacific. The enhancement of TC numbers in both canonical El Niño and positive-neutral years is associated with the extension of favorable low-level cyclonic relative vorticity, and low vertical wind shear eastward across the date line. Relative humidity and SST are also very conducive forgenesis in this region during canonical El Niño and positiveneutral events. The patterns are quite different, however, with the favorable conditions concentrated in the date line region for the positive-neutral, as compared with conditions farther eastward for the canonical El Niño regime. A significant result of the study is the demonstration that ENSO-neutralevents can be objectively clustered into two separate regimes, each with very different impacts on TCgenesis. © 2013 American Meteorological Society.
- Authors: Chand, Savin , McBride, John , Tory, Kevin , Wheeler, Matthew , Walsh, Kevin
- Date: 2013
- Type: Text , Journal article
- Relation: Journal of Climate Vol. 26, no. 2 (2013), p. 600-608
- Full Text: false
- Reviewed:
- Description: The influence of different types of ENSO on tropical cyclone (TC) interannual variability in the central southwest Pacific region (58-258S, 1708E-1708W) is investigated. Using empirical orthogonal function analysis and an agglomerative hierarchical clustering of early tropical cyclone season Pacific sea surface temperature, years are classified into four separate regimes (i.e., canonical El Niño, canonical La Niña, positive-neutral, and negative-neutral) for the period between 1970 and 2009.These regimes are found to have a large impact on TC genesis over the central southwest Pacific region. Both the canonical El Niño and the positive-neutral years have increased numbers of cyclones, with an average of 4.3 yr-1 for positive-neutral and 4 yr-1 for canonical El Niño. In contrast, during a La Niña and negative-neutral events, substantially fewer TCs (averages of ;2.2 and 2.4 yr-1, respectively) are observed in the central southwest Pacific. The enhancement of TC numbers in both canonical El Niño and positive-neutral years is associated with the extension of favorable low-level cyclonic relative vorticity, and low vertical wind shear eastward across the date line. Relative humidity and SST are also very conducive forgenesis in this region during canonical El Niño and positiveneutral events. The patterns are quite different, however, with the favorable conditions concentrated in the date line region for the positive-neutral, as compared with conditions farther eastward for the canonical El Niño regime. A significant result of the study is the demonstration that ENSO-neutralevents can be objectively clustered into two separate regimes, each with very different impacts on TCgenesis. © 2013 American Meteorological Society.
- Sachindra, Dhanapala, Huang, Fuchun, Barton, Andrew, Perera, Bimalka
- Authors: Sachindra, Dhanapala , Huang, Fuchun , Barton, Andrew , Perera, Bimalka
- Date: 2013
- Type: Text , Journal article
- Relation: Quarterly Journal of the Royal Meteorological Society Vol. 140, no. 681 (2013), p. 1161-1178
- Full Text: false
- Reviewed:
- Description: Two statistical downscaling models were developed for downscaling monthly General Circulation Model (GCM) outputs to precipitation at a site in north-western Victoria, Australia. The first downscaling model was calibrated and validated with the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis outputs over the periods of 1950–1989 and 1990–2010 respectively. The projections of precipitation into the future were produced by introducing the outputs of HadCM3, ECHAM5, GFDL2.0 and GFDL2.1, pertaining to A2 and B1 greenhouse gas emission scenarios to this downscaling model. In this model, the input data used in the development and future projections are not homogeneous, as they originate from two different sources. As a solution to this issue, the second downscaling model was developed and precipitation projections into the future were produced with a homogeneous set of inputs. To produce a homogeneous set of inputs to this model, regression relationships were formulated between the NCEP/NCAR reanalysis outputs and the twentieth-century climate experiment outputs corresponding to the variables used in the first downscaling model obtained from the ensemble consisting of HadCM3, ECHAM5 and GFDL2.0. The outputs of these relationships pertaining to the periods of 1950–1989 and 1990–1999 were used for the calibration and validation of this downscaling model respectively. Using the outputs of HadCM3, ECHAM5 and GFDL2.0 pertaining to A2 and B1 emission scenarios on these relationships, inputs for the second downscaling model pertaining to the period of 2000–2099 were generated. The first downscaling model withNCEP/NCARreanalysis outputs showed a highNash–Sutcliffe Efficiency (NSE) of 0.75 over the period 1950–1999. When this downscaling model was run with the twentieth-century climate experiment outputs of HadCM3, ECHAM5, GFDL2.0 and GFDL2.1, it exhibited limited performances over the period 1950–1999, which was indicated by relatively lowNSEs of−0.62,−2.54,−0.40 and−0.48 respectively. The second downscaling model displayed an NSE of 0.35 over the period 1950–1999.