Tropical cyclone tracks in CMIP5 models : statistical assessment and future projections
- Authors: Bell, Samuel
- Date: 2019
- Type: Text , Thesis , PhD
- Full Text:
- Description: Tropical cyclones (TCs) can have devastating social and economic impacts on coastal communities situated all around the globe. The impact of anthropogenic induced climate change on TC activity has attracted widespread scientific interest over the past decade, resulting in the development of a variety of approaches for TC projection in climate models. However, many uncertainties remain, including those associated with the TC detection algorithm and climate model inter-dependencies that impact projection results. This thesis seeks to address these uncertainties, as well as filling several knowledge gaps in the literature such as limited TC projection studies in the Southern Hemisphere and a global need for regional-scale TC track density projections. The independent TC detection and tracking algorithm utilised in this thesis is first evaluated to determine if it can simulate a realistic TC track climatology in reanalysis data. By way of cluster analysis, model-detected and observed TC tracks are compared and objective criteria for a consistent “TC track” definition are established. Regional-scale TC track projections are then examined in each TC basin around the globe. The exact methodology of cluster analysis in each basin is slightly modified to accommodate basin-scale differences in track climatology but generally follows a cluster assessment of TC tracks in observations, historical climate simulations and future climate projections using results from the Coupled Model Intercomparison Project Phase 5 (CMIP5) models. Regional impacts of the El Niño Southern Oscillation (ENSO) on TC tracks are also examined in current- and future-climates. Projection results are found to be supportive of existing studies, especially in the North Pacific and the Southern Hemisphere. Isolation of TC tracks into clusters indicated that the regional dominance of ENSO is well simulated by the CMIP5 models. Several regional changes in TC activity are noted and attributed to projected changes in the large-scale environment, and changes in ENSO-specific conditions.
- Description: Doctor of Philosophy
- Authors: Bell, Samuel
- Date: 2019
- Type: Text , Thesis , PhD
- Full Text:
- Description: Tropical cyclones (TCs) can have devastating social and economic impacts on coastal communities situated all around the globe. The impact of anthropogenic induced climate change on TC activity has attracted widespread scientific interest over the past decade, resulting in the development of a variety of approaches for TC projection in climate models. However, many uncertainties remain, including those associated with the TC detection algorithm and climate model inter-dependencies that impact projection results. This thesis seeks to address these uncertainties, as well as filling several knowledge gaps in the literature such as limited TC projection studies in the Southern Hemisphere and a global need for regional-scale TC track density projections. The independent TC detection and tracking algorithm utilised in this thesis is first evaluated to determine if it can simulate a realistic TC track climatology in reanalysis data. By way of cluster analysis, model-detected and observed TC tracks are compared and objective criteria for a consistent “TC track” definition are established. Regional-scale TC track projections are then examined in each TC basin around the globe. The exact methodology of cluster analysis in each basin is slightly modified to accommodate basin-scale differences in track climatology but generally follows a cluster assessment of TC tracks in observations, historical climate simulations and future climate projections using results from the Coupled Model Intercomparison Project Phase 5 (CMIP5) models. Regional impacts of the El Niño Southern Oscillation (ENSO) on TC tracks are also examined in current- and future-climates. Projection results are found to be supportive of existing studies, especially in the North Pacific and the Southern Hemisphere. Isolation of TC tracks into clusters indicated that the regional dominance of ENSO is well simulated by the CMIP5 models. Several regional changes in TC activity are noted and attributed to projected changes in the large-scale environment, and changes in ENSO-specific conditions.
- Description: Doctor of Philosophy
Review of tropical cyclones in the Australian region : Climatology, variability, predictability, and trends
- Chand, Savin, Dowdy, Andrew, Ramsay, Hamish, Walsh, Kevin, Tory, Kevin, Power, Scott, Bell, Samuel, Lavender, Sally, Ye, Hua, Kuleshov, Yuri
- Authors: Chand, Savin , Dowdy, Andrew , Ramsay, Hamish , Walsh, Kevin , Tory, Kevin , Power, Scott , Bell, Samuel , Lavender, Sally , Ye, Hua , Kuleshov, Yuri
- Date: 2019
- Type: Text , Journal article , Review
- Relation: Wiley Interdisciplinary Reviews: Climate Change Vol. 10, no. 5 (2019), p. 1-17
- Full Text:
- Reviewed:
- Description: Tropical cyclones (TCs) can have severe impacts on Australia. These include extreme rainfall and winds, and coastal hazards such as destructive waves, storm surges, estuarine flooding, and coastal erosion. Various aspects of TCs in the Australian region have been documented over the past several decades. In recent years, increasing emphasis has been placed on human-induced climate change effects on TCs in the Australian region and elsewhere around the globe. However, large natural variability and the lack of consistent long-term TC observations have often complicated the detection and attribution of TC trends. Efforts have been made to improve TC records for Australia over the past decades, but it is still unclear whether such records are sufficient to provide better understanding of the impacts of natural climate variability and climate change. It is important to note that the damage costs associated with tropical cyclones in Australia have increased in recent decades and will continue to increase due to growing coastal settlement and infrastructure development. Therefore, it is critical that any coastal infrastructure planning and engineering decisions, as well as disaster management decisions, strongly consider future risks from tropical cyclones. A better understanding of tropical cyclones in a changing climate will provide key insights that can help mitigate impacts of tropical cyclones on vulnerable communities. An objective assessment of the Australian TCs at regional scale and its link with climate variability and change using improved and up-to-date data records is more imperative now than before. This article is categorized under: Paleoclimates and Current Trends > Modern Climate Change.
- Authors: Chand, Savin , Dowdy, Andrew , Ramsay, Hamish , Walsh, Kevin , Tory, Kevin , Power, Scott , Bell, Samuel , Lavender, Sally , Ye, Hua , Kuleshov, Yuri
- Date: 2019
- Type: Text , Journal article , Review
- Relation: Wiley Interdisciplinary Reviews: Climate Change Vol. 10, no. 5 (2019), p. 1-17
- Full Text:
- Reviewed:
- Description: Tropical cyclones (TCs) can have severe impacts on Australia. These include extreme rainfall and winds, and coastal hazards such as destructive waves, storm surges, estuarine flooding, and coastal erosion. Various aspects of TCs in the Australian region have been documented over the past several decades. In recent years, increasing emphasis has been placed on human-induced climate change effects on TCs in the Australian region and elsewhere around the globe. However, large natural variability and the lack of consistent long-term TC observations have often complicated the detection and attribution of TC trends. Efforts have been made to improve TC records for Australia over the past decades, but it is still unclear whether such records are sufficient to provide better understanding of the impacts of natural climate variability and climate change. It is important to note that the damage costs associated with tropical cyclones in Australia have increased in recent decades and will continue to increase due to growing coastal settlement and infrastructure development. Therefore, it is critical that any coastal infrastructure planning and engineering decisions, as well as disaster management decisions, strongly consider future risks from tropical cyclones. A better understanding of tropical cyclones in a changing climate will provide key insights that can help mitigate impacts of tropical cyclones on vulnerable communities. An objective assessment of the Australian TCs at regional scale and its link with climate variability and change using improved and up-to-date data records is more imperative now than before. This article is categorized under: Paleoclimates and Current Trends > Modern Climate Change.
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**
Severe tropical cyclones over southwest Pacific Islands : economic impacts and implications for disaster risk management
- Deo, Anil, Chand, Savin, McIntosh, R. Duncan, Prakash, Bipen, Holbrook, Neil, Magee, Andrew, Haruhiru, Alick, Malsale, Philip
- Authors: Deo, Anil , Chand, Savin , McIntosh, R. Duncan , Prakash, Bipen , Holbrook, Neil , Magee, Andrew , Haruhiru, Alick , Malsale, Philip
- Date: 2022
- Type: Text , Journal article
- Relation: Climatic Change Vol. 172, no. 3-4 (2022), p.
- Full Text:
- Reviewed:
- Description: Tropical cyclones (TCs) are amongst the costliest natural hazards for southwest Pacific (SWP) Island nations. Extreme winds coupled with heavy rainfall and related coastal hazards, such as large waves and high seas, can have devastating consequences for life and property. Effects of anthropogenic climate change are likely to make TCs even more destructive in the SWP (as that observed particularly over Fiji) and elsewhere around the globe, yet TCs may occur less often. However, the underpinning science of quantifying future TC projections amid multiple uncertainties can be complex. The challenge for scientists is how to turn such technical knowledge framed around uncertainties into tangible products to inform decision-making in the disaster risk management (DRM) and disaster risk reduction (DRR) sector. Drawing on experiences from past TC events as analogies to what may happen in a warming climate can be useful. The role of science-based climate services tailored to the needs of the DRM and DRR sector is critical in this context. In the first part of this paper, we examine cases of historically severe TCs in the SWP and quantify their socio-economic impacts. The second part of this paper discusses a decision-support framework developed in collaboration with a number of agencies in the SWP, featuring science-based climate services that inform different stages of planning in national-level risk management strategies. © 2022, The Author(s).
- Authors: Deo, Anil , Chand, Savin , McIntosh, R. Duncan , Prakash, Bipen , Holbrook, Neil , Magee, Andrew , Haruhiru, Alick , Malsale, Philip
- Date: 2022
- Type: Text , Journal article
- Relation: Climatic Change Vol. 172, no. 3-4 (2022), p.
- Full Text:
- Reviewed:
- Description: Tropical cyclones (TCs) are amongst the costliest natural hazards for southwest Pacific (SWP) Island nations. Extreme winds coupled with heavy rainfall and related coastal hazards, such as large waves and high seas, can have devastating consequences for life and property. Effects of anthropogenic climate change are likely to make TCs even more destructive in the SWP (as that observed particularly over Fiji) and elsewhere around the globe, yet TCs may occur less often. However, the underpinning science of quantifying future TC projections amid multiple uncertainties can be complex. The challenge for scientists is how to turn such technical knowledge framed around uncertainties into tangible products to inform decision-making in the disaster risk management (DRM) and disaster risk reduction (DRR) sector. Drawing on experiences from past TC events as analogies to what may happen in a warming climate can be useful. The role of science-based climate services tailored to the needs of the DRM and DRR sector is critical in this context. In the first part of this paper, we examine cases of historically severe TCs in the SWP and quantify their socio-economic impacts. The second part of this paper discusses a decision-support framework developed in collaboration with a number of agencies in the SWP, featuring science-based climate services that inform different stages of planning in national-level risk management strategies. © 2022, The Author(s).
Tropical cyclone climatology, variability, and trends in the Tonga region, Southwest Pacific
- Tu'uholoaki, Moleni, Singh, Awnesh, Espejo, Antonio, Chand, Savin, Damlamian, Herve
- Authors: Tu'uholoaki, Moleni , Singh, Awnesh , Espejo, Antonio , Chand, Savin , Damlamian, Herve
- Date: 2022
- Type: Text , Journal article
- Relation: Weather and Climate Extremes Vol. 37, no. (2022), p.
- Full Text:
- Reviewed:
- Description: The focus of several past tropical cyclone (TC) studies in the Southwest Pacific (SWP) had been primarily at the regional scale, with little or no attention to the local-scale TC activity (i.e., at the country level). With the growing coastal population in the South Pacific Island countries, as well as increasing threats from and exposure to climate extremes mostly affecting vulnerable communities, examining TC-related risks at the country level is more imperative now than before. This study catalogues for the first time the climatology, variability and trends of TCs affecting Nuku'alofa, the capital of Tonga using the Southwest Pacific Enhanced Archived for Tropical Cyclone (SPEArTC) dataset for the period between 1970 and 2019. The variability is examined in relation to the El Niño–Southern Oscillation (ENSO) phenomenon, which is the major driver of the year-to-year variability of TC activity in the SWP. A total of 128 TC tracks affected the Tonga region over the study period, with a seasonal average of
- Authors: Tu'uholoaki, Moleni , Singh, Awnesh , Espejo, Antonio , Chand, Savin , Damlamian, Herve
- Date: 2022
- Type: Text , Journal article
- Relation: Weather and Climate Extremes Vol. 37, no. (2022), p.
- Full Text:
- Reviewed:
- Description: The focus of several past tropical cyclone (TC) studies in the Southwest Pacific (SWP) had been primarily at the regional scale, with little or no attention to the local-scale TC activity (i.e., at the country level). With the growing coastal population in the South Pacific Island countries, as well as increasing threats from and exposure to climate extremes mostly affecting vulnerable communities, examining TC-related risks at the country level is more imperative now than before. This study catalogues for the first time the climatology, variability and trends of TCs affecting Nuku'alofa, the capital of Tonga using the Southwest Pacific Enhanced Archived for Tropical Cyclone (SPEArTC) dataset for the period between 1970 and 2019. The variability is examined in relation to the El Niño–Southern Oscillation (ENSO) phenomenon, which is the major driver of the year-to-year variability of TC activity in the SWP. A total of 128 TC tracks affected the Tonga region over the study period, with a seasonal average of
Subseasonal prediction framework for tropical cyclone activity in the Solomon Islands region
- Haruhiru, Alick, Chand, Savin, Sultanova, Nargiz, Ramsay, Hamish, Sharma, Krishneel, Tahani, Lloyd
- Authors: Haruhiru, Alick , Chand, Savin , Sultanova, Nargiz , Ramsay, Hamish , Sharma, Krishneel , Tahani, Lloyd
- Date: 2023
- Type: Text , Journal article
- Relation: International Journal of Climatology Vol. 43, no. 12 (2023), p. 5763-5777
- Full Text:
- Reviewed:
- Description: Recently, we developed seasonal prediction schemes with improved skill to predict tropical cyclone (TC) activity up to 3 months in advance for the Solomon Islands (SI) region (5°–15°S, 155°–170°E) using sophisticated Bayesian regression techniques. However, TC prediction at subseasonal timescale (i.e., 1–4 weeks in advance) is not being researched for that region despite growing demands from decision makers at sectoral level. In this paper, we first assess the feasibility of developing subseasonal prediction frameworks for the SI region using a pool of predictors that are known to affect TC activity in the region. We then evaluate multiple predictor combinations to develop the most appropriate models using a statistical approach to forecast weekly TC activity up to 4 weeks in advance. Predictors used include indices of various natural climate variability modes, namely the Madden–Julian Oscillation (MJO), the El Niño–Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD) and the Interdecadal Pacific Oscillation (IPO). These modes often have robust physical and statistical relationships with TC occurrences in the SI region and the broader southwest Pacific territory as shown by preceding studies. Additionally, we incorporate TC seasonality as a potential predictor given the persistence of TCs occurring more in certain months than others. Note that a model with seasonality predictor alone (hereafter called the “climatology” model) forms a baseline for comparisons. The hindcast verifications of the forecasts using leave-one-out cross-validation procedure over the study period 1975–2019 indicate considerable improvements in prediction skill of our logistic regression models over climatology, even up to 4 weeks in advance. This study sets the foundation for introducing subseasonal prediction services, which is a national priority for improved decision making in sectors like agriculture and food security, water, health and disaster risk mitigation in the Solomon Islands. © 2023 The Authors. International Journal of Climatology published by John Wiley & Sons Ltd on behalf of Royal Meteorological Society.
- Authors: Haruhiru, Alick , Chand, Savin , Sultanova, Nargiz , Ramsay, Hamish , Sharma, Krishneel , Tahani, Lloyd
- Date: 2023
- Type: Text , Journal article
- Relation: International Journal of Climatology Vol. 43, no. 12 (2023), p. 5763-5777
- Full Text:
- Reviewed:
- Description: Recently, we developed seasonal prediction schemes with improved skill to predict tropical cyclone (TC) activity up to 3 months in advance for the Solomon Islands (SI) region (5°–15°S, 155°–170°E) using sophisticated Bayesian regression techniques. However, TC prediction at subseasonal timescale (i.e., 1–4 weeks in advance) is not being researched for that region despite growing demands from decision makers at sectoral level. In this paper, we first assess the feasibility of developing subseasonal prediction frameworks for the SI region using a pool of predictors that are known to affect TC activity in the region. We then evaluate multiple predictor combinations to develop the most appropriate models using a statistical approach to forecast weekly TC activity up to 4 weeks in advance. Predictors used include indices of various natural climate variability modes, namely the Madden–Julian Oscillation (MJO), the El Niño–Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD) and the Interdecadal Pacific Oscillation (IPO). These modes often have robust physical and statistical relationships with TC occurrences in the SI region and the broader southwest Pacific territory as shown by preceding studies. Additionally, we incorporate TC seasonality as a potential predictor given the persistence of TCs occurring more in certain months than others. Note that a model with seasonality predictor alone (hereafter called the “climatology” model) forms a baseline for comparisons. The hindcast verifications of the forecasts using leave-one-out cross-validation procedure over the study period 1975–2019 indicate considerable improvements in prediction skill of our logistic regression models over climatology, even up to 4 weeks in advance. This study sets the foundation for introducing subseasonal prediction services, which is a national priority for improved decision making in sectors like agriculture and food security, water, health and disaster risk mitigation in the Solomon Islands. © 2023 The Authors. International Journal of Climatology published by John Wiley & Sons Ltd on behalf of Royal Meteorological Society.
Tropical cyclones and depressions over the South Pacific Ocean since the late 19th century : assessing synergistic relationship between the El Niño Southern Oscillation and Interdecadal Pacific Oscillation
- Yeasmin, Alea, Chand, Savin, Sultanova, Nargiz
- Authors: Yeasmin, Alea , Chand, Savin , Sultanova, Nargiz
- Date: 2023
- Type: Text , Journal article
- Relation: International Journal of Climatology Vol. 43, no. 12 (2023), p. 5422-5443
- Full Text:
- Reviewed:
- Description: Tropical cyclones (TCs) and tropical depressions (TDs), hereafter collectively referred to as tropical storms, often exhibit large year-to-year variability in the South Pacific Ocean basin. Many past studies have examined this variability in relation to the El Niño Southern Oscillation (ENSO) phenomenon, particularly using observational data from the post-satellite era (i.e., after the 1970s when TC observations became more consistent). However, less emphasis is placed on how tropical storms are modulated at interdecadal and decadal time scales such as due to Interdecadal Pacific Oscillation (IPO). This is because post-satellite data are available for relatively short time period (i.e., post-1970s), limiting our understanding of the IPO–TC relationship in the South Pacific. Here, using NOAA-CIRES 20th Century Reanalysis (20CR) dataset, we reconstruct historical records (1871–2014) of TC and depression proxies for the South Pacific Ocean basin, and then utilize these reconstructed proxies to first understand the connections between TC–ENSO and TC–IPO over the 20th century, and then investigate the combined effects of ENSO–IPO effects on TCs and depressions. Results show that La Niña (El Niño) is more dominant on TC activity than El Niño (La Niña) over the western subregion 140–170° E (eastern sub-region, 170–220° E) as expected. We also show that TC numbers are strongly modulated by the IPO phenomenon with, on average, more TCs occurring during the positive phase than during the negative phase of the IPO in both western and eastern sub-regions. We show for the first time (using a long-term reconstructed TC dataset) that the combined phases of El Niño and + IPO account for increased TC activity, as opposed to the combined phase of La Niña and
- Authors: Yeasmin, Alea , Chand, Savin , Sultanova, Nargiz
- Date: 2023
- Type: Text , Journal article
- Relation: International Journal of Climatology Vol. 43, no. 12 (2023), p. 5422-5443
- Full Text:
- Reviewed:
- Description: Tropical cyclones (TCs) and tropical depressions (TDs), hereafter collectively referred to as tropical storms, often exhibit large year-to-year variability in the South Pacific Ocean basin. Many past studies have examined this variability in relation to the El Niño Southern Oscillation (ENSO) phenomenon, particularly using observational data from the post-satellite era (i.e., after the 1970s when TC observations became more consistent). However, less emphasis is placed on how tropical storms are modulated at interdecadal and decadal time scales such as due to Interdecadal Pacific Oscillation (IPO). This is because post-satellite data are available for relatively short time period (i.e., post-1970s), limiting our understanding of the IPO–TC relationship in the South Pacific. Here, using NOAA-CIRES 20th Century Reanalysis (20CR) dataset, we reconstruct historical records (1871–2014) of TC and depression proxies for the South Pacific Ocean basin, and then utilize these reconstructed proxies to first understand the connections between TC–ENSO and TC–IPO over the 20th century, and then investigate the combined effects of ENSO–IPO effects on TCs and depressions. Results show that La Niña (El Niño) is more dominant on TC activity than El Niño (La Niña) over the western subregion 140–170° E (eastern sub-region, 170–220° E) as expected. We also show that TC numbers are strongly modulated by the IPO phenomenon with, on average, more TCs occurring during the positive phase than during the negative phase of the IPO in both western and eastern sub-regions. We show for the first time (using a long-term reconstructed TC dataset) that the combined phases of El Niño and + IPO account for increased TC activity, as opposed to the combined phase of La Niña and
Influence of the Madden–Julian Oscillation (MJO) on tropical cyclones affecting Tonga in the Southwest Pacific
- Tu’uholoaki, Moleni, Espejo, Antonio, Sharma, Krishneel, Singh, Awnesh, Wandres, Moritz, Damlamian, Herve, Chand, Savin
- Authors: Tu’uholoaki, Moleni , Espejo, Antonio , Sharma, Krishneel , Singh, Awnesh , Wandres, Moritz , Damlamian, Herve , Chand, Savin
- Date: 2023
- Type: Text , Journal article
- Relation: Atmosphere Vol. 14, no. 7 (2023), p.
- Full Text:
- Reviewed:
- Description: The modulating influence of the Madden–Julian oscillation (MJO) on tropical cyclones (TCs) has been examined globally, regionally, and subregionally, but its impact on the island scale remains unclear. This study investigates how TC activity affecting the Tonga region is being modulated by the MJO, using the Southwest Pacific Enhanced Archive of Tropical Cyclones (SPEArTC) and the MJO index. In particular, this study investigates how the MJO modulates the frequency and intensity of TCs affecting the Tonga region relative to the entire study period (1970–2019; hereafter referred to as all years), as well as to different phases of the El Niño southern oscillation (ENSO) phenomenon. Results suggest that the MJO strongly modulates TC activity affecting the Tonga region. The frequency and intensity of TCs is enhanced during the active phases (phases six to eight) in all years, including El Niño and ENSO-neutral years. The MJO also strongly influences the climatological pattern of genesis of TCs affecting the Tonga region, where more (fewer) cyclones form in the active (inactive) phases of the MJO and more genesis points are clustered (scattered) near (away from) the Tonga region. There were three regression curves that best described the movement of TCs in the region matching the dominant steering mechanisms in the Southwest Pacific region. The findings of this study can provide climatological information for the Tonga Meteorological Service (TMS) and disaster managers to better understand the TC risk associated with the impact of the MJO on TCs affecting the Tonga region and support its TC early warning system. © 2023 by the authors.
- Authors: Tu’uholoaki, Moleni , Espejo, Antonio , Sharma, Krishneel , Singh, Awnesh , Wandres, Moritz , Damlamian, Herve , Chand, Savin
- Date: 2023
- Type: Text , Journal article
- Relation: Atmosphere Vol. 14, no. 7 (2023), p.
- Full Text:
- Reviewed:
- Description: The modulating influence of the Madden–Julian oscillation (MJO) on tropical cyclones (TCs) has been examined globally, regionally, and subregionally, but its impact on the island scale remains unclear. This study investigates how TC activity affecting the Tonga region is being modulated by the MJO, using the Southwest Pacific Enhanced Archive of Tropical Cyclones (SPEArTC) and the MJO index. In particular, this study investigates how the MJO modulates the frequency and intensity of TCs affecting the Tonga region relative to the entire study period (1970–2019; hereafter referred to as all years), as well as to different phases of the El Niño southern oscillation (ENSO) phenomenon. Results suggest that the MJO strongly modulates TC activity affecting the Tonga region. The frequency and intensity of TCs is enhanced during the active phases (phases six to eight) in all years, including El Niño and ENSO-neutral years. The MJO also strongly influences the climatological pattern of genesis of TCs affecting the Tonga region, where more (fewer) cyclones form in the active (inactive) phases of the MJO and more genesis points are clustered (scattered) near (away from) the Tonga region. There were three regression curves that best described the movement of TCs in the region matching the dominant steering mechanisms in the Southwest Pacific region. The findings of this study can provide climatological information for the Tonga Meteorological Service (TMS) and disaster managers to better understand the TC risk associated with the impact of the MJO on TCs affecting the Tonga region and support its TC early warning system. © 2023 by the authors.
Reconstruction of tropical cyclone and depression proxies for the South Pacific since the 1850s
- Yeasmin, Alea, Chand, Savin, Sultanova, Nargiz
- Authors: Yeasmin, Alea , Chand, Savin , Sultanova, Nargiz
- Date: 2023
- Type: Text , Journal article
- Relation: Weather and Climate Extremes Vol. 39, no. (2023), p.
- Full Text:
- Reviewed:
- Description: Southwest Pacific nations are highly vulnerable to extreme weather and climate events, particularly those associated with synoptic-scale systems such as tropical cyclones (TCs) and depressions (TDs). This study utilises the Okubo–Weiss–Zeta parameter (OWZP) method to reconstruct historical records of both TCs and TDs for the South Pacific basin using state-of-the-art NOAA-CIRES Twentieth Century Reanalysis (20CR) product. Extensive statistical assessments of these reconstructions are carried out using observational records for the satellite period (i.e., 1979–2014) as ‘ground-truths’. Results show that 20CR-derived TCs and TDs resemble several key characteristics of the observational records, including spatial distribution of genesis locations and track shapes. This gives us confidence that the 20CR-derived long-term records of TCs and TDs can serve as an effective tool for examining historical changes in various characteristics of TCs and TDs, particularly in the context of anthropogenic climate change. © 2022
- Authors: Yeasmin, Alea , Chand, Savin , Sultanova, Nargiz
- Date: 2023
- Type: Text , Journal article
- Relation: Weather and Climate Extremes Vol. 39, no. (2023), p.
- Full Text:
- Reviewed:
- Description: Southwest Pacific nations are highly vulnerable to extreme weather and climate events, particularly those associated with synoptic-scale systems such as tropical cyclones (TCs) and depressions (TDs). This study utilises the Okubo–Weiss–Zeta parameter (OWZP) method to reconstruct historical records of both TCs and TDs for the South Pacific basin using state-of-the-art NOAA-CIRES Twentieth Century Reanalysis (20CR) product. Extensive statistical assessments of these reconstructions are carried out using observational records for the satellite period (i.e., 1979–2014) as ‘ground-truths’. Results show that 20CR-derived TCs and TDs resemble several key characteristics of the observational records, including spatial distribution of genesis locations and track shapes. This gives us confidence that the 20CR-derived long-term records of TCs and TDs can serve as an effective tool for examining historical changes in various characteristics of TCs and TDs, particularly in the context of anthropogenic climate change. © 2022
Tropical cyclone prediction for the Solomon Islands region
- Authors: Haruhiru, Alick
- Date: 2023
- Type: Text , Thesis , PhD
- Full Text:
- Description: Tropical cyclones (TCs) are among the costliest natural disasters impacting the Solomon Islands in the southwest Pacific due to its high vulnerability and low adaptive capacity to the hazard. Strong winds coupled with heavy rainfall often have devastating consequences on life and property. Occurrence of TCs in the Solomon Islands region – defined here as 5°–15°S and 155°–170°E – have large year-to-year variability over the period 1970-2019, ranging from TC numbers as low as zero to up to eight in some years. Geographically, the region spans the spatial phase change of the major climatic driver in the South Pacific, the El Niño Southern Oscillation (ENSO), and so the year-to-year variability of TCs here do not have any defined pattern. This creates a ‘predictability barrier’ for seasonal (and even sub-seasonal) prediction of TCs in the region. To circumvent the issue of TC predictability in the Solomon Islands region, I first objectively defined the total observed TCs into three specific clusters. Cluster-specific TCs showed improved patterns of variability with respect to natural modes of climate variability such as ENSO, the Madden Julian Oscillations (MJO) and Interdecadal Pacific Oscillations (IPO). I then developed sophisticated statistical prediction models for TCs in each cluster at seasonal and sub-seasonal timescales using ENSO, the MJO and IPO as main predictors. Overall, the results showed enhanced predictability skills of TCs up to several months in advance compared with methods that are currently being used by the Solomon Islands Meteorological Service. It is anticipated that improved seasonal and sub-seasonal predictions of TCs at various timescales can help disaster management agencies in the Solomon Islands with appropriate plannings and decision-making to lessen risks associated with TC events.
- Description: Doctor of Philosophy
- Authors: Haruhiru, Alick
- Date: 2023
- Type: Text , Thesis , PhD
- Full Text:
- Description: Tropical cyclones (TCs) are among the costliest natural disasters impacting the Solomon Islands in the southwest Pacific due to its high vulnerability and low adaptive capacity to the hazard. Strong winds coupled with heavy rainfall often have devastating consequences on life and property. Occurrence of TCs in the Solomon Islands region – defined here as 5°–15°S and 155°–170°E – have large year-to-year variability over the period 1970-2019, ranging from TC numbers as low as zero to up to eight in some years. Geographically, the region spans the spatial phase change of the major climatic driver in the South Pacific, the El Niño Southern Oscillation (ENSO), and so the year-to-year variability of TCs here do not have any defined pattern. This creates a ‘predictability barrier’ for seasonal (and even sub-seasonal) prediction of TCs in the region. To circumvent the issue of TC predictability in the Solomon Islands region, I first objectively defined the total observed TCs into three specific clusters. Cluster-specific TCs showed improved patterns of variability with respect to natural modes of climate variability such as ENSO, the Madden Julian Oscillations (MJO) and Interdecadal Pacific Oscillations (IPO). I then developed sophisticated statistical prediction models for TCs in each cluster at seasonal and sub-seasonal timescales using ENSO, the MJO and IPO as main predictors. Overall, the results showed enhanced predictability skills of TCs up to several months in advance compared with methods that are currently being used by the Solomon Islands Meteorological Service. It is anticipated that improved seasonal and sub-seasonal predictions of TCs at various timescales can help disaster management agencies in the Solomon Islands with appropriate plannings and decision-making to lessen risks associated with TC events.
- Description: Doctor of Philosophy
Clustering tropical cyclone genesis on ENSO timescales in the southwest Pacific
- Tu’uholoaki, Moleni, Espejo, Antonio, Singh, Awnesh, Damlamian, Herve, Wandres, Moritz, Chand, Savin, Mendez, Fernando, Fa’anunu, Ofa
- Authors: Tu’uholoaki, Moleni , Espejo, Antonio , Singh, Awnesh , Damlamian, Herve , Wandres, Moritz , Chand, Savin , Mendez, Fernando , Fa’anunu, Ofa
- Date: 2023
- Type: Text , Journal article
- Relation: Climate Dynamics Vol. 60, no. 11-12 (2023), p. 3353-3368
- Full Text:
- Reviewed:
- Description: Tropical cyclones (TCs) as a natural hazard pose a major threat and risk to the human population globally. This threat is expected to increase in a warming climate as the frequency of severe TCs is expected to increase. In this study, the influence of different monthly sea surface temperature (SST) patterns on the locations and frequency of tropical cyclone genesis (TCG) in the Southwest Pacific (SWP) region is investigated. Using principal component analysis and k-means clustering of monthly SST between 1970 and 2019, nine statistically different SST patterns are identified. Our findings show that the more prominent ENSO patterns such as the Modoki El Niño (i.e., Modoki I and Modoki II) and Eastern Pacific (EP) El Niño impact the frequency and location of TCG significantly. Our results enhance the overall understanding of the TCG variability and the relationship between TCG and SST configurations in the SWP region. The results of this study may support early warning system in SWP by improving seasonal outlooks and quantification of the level of TC-related risks for the vulnerable Pacific Island communities. © 2022, The Author(s).
- Authors: Tu’uholoaki, Moleni , Espejo, Antonio , Singh, Awnesh , Damlamian, Herve , Wandres, Moritz , Chand, Savin , Mendez, Fernando , Fa’anunu, Ofa
- Date: 2023
- Type: Text , Journal article
- Relation: Climate Dynamics Vol. 60, no. 11-12 (2023), p. 3353-3368
- Full Text:
- Reviewed:
- Description: Tropical cyclones (TCs) as a natural hazard pose a major threat and risk to the human population globally. This threat is expected to increase in a warming climate as the frequency of severe TCs is expected to increase. In this study, the influence of different monthly sea surface temperature (SST) patterns on the locations and frequency of tropical cyclone genesis (TCG) in the Southwest Pacific (SWP) region is investigated. Using principal component analysis and k-means clustering of monthly SST between 1970 and 2019, nine statistically different SST patterns are identified. Our findings show that the more prominent ENSO patterns such as the Modoki El Niño (i.e., Modoki I and Modoki II) and Eastern Pacific (EP) El Niño impact the frequency and location of TCG significantly. Our results enhance the overall understanding of the TCG variability and the relationship between TCG and SST configurations in the SWP region. The results of this study may support early warning system in SWP by improving seasonal outlooks and quantification of the level of TC-related risks for the vulnerable Pacific Island communities. © 2022, The Author(s).
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