Violent tropical cyclones (TCs) continue to inflict serious impacts on national economies and welfare, but how they are responding to global warming has not been fully clarified. Here I construct an empirical framework that shows the observations supporting a strong link between rising global ocean warmth and increasing trade-off between TC intensity and frequency in the western North Pacific. Thermodynamic structure of the tropical western North Pacific with high global ocean warmth is characterized by convectively more unstable lower troposphere with greater heat and moisture, but this instability is simultaneously accompanied by anomalous high pressure in the middle and upper troposphere over the same region. Increasing trade-off level between TC intensity and frequency in a warmer year proves that this environment further inhibits the TC occurrences over the region, but TCs that form tend to discharge stored energy to upper troposphere with stronger intensities. By increasing the intensity threshold at higher levels we confirmed that the TC climate connection with global ocean warmth occurs throughout the strongest portion of TCs, and the environmental connection of the TC climate is more conspicuous in the extreme portion of TCs. Intensities at the strongest 10~% of the western North Pacific TCs are comparable to super typhoons on average, the increasing trade-off magnitude clearly suggests that super typhoons in a warmer year gets stronger. Conclusively, the negative collinear feature of the thermodynamics influences the portion of TCs at the highest intensities, and super typhoons are likely to become stronger at the expense of overall TC frequencies in a warmer world. The consequence of this finding is that record-breaking TC intensities occur at the expense of overall TC frequencies under global warming. TC activity is understood as a variation which is independent of global warming, and could be assumed to be an internal variability having no trend. Frequency variation and super typhoon intensity variation are regarded as the addition of global warming influence on TC activity variation. The structure depicts how a previous intensity record is overtaken and frequency falls continuously in the global warming environment in a linear perspective. A peak TC activity year when global ocean warmth is the highest ever is likely to experience a record-breaking intensity. In the same way, the least number of annual TCs may appear when a lull of TC activity occurs in the warmest year. / A Dissertation submitted to the Geophysical Fluid Dynamics Institute in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Fall Semester, 2014. / August 25, 2014. / efficiency of intensity, global warming, super typhoon, Tropical cyclone climate / Includes bibliographical references. / James B. Elsner, Professor Directing Dissertation; Robert Hart, University Representative; Kevin Speer, Committee Member; Mark Bourassa, Committee Member.

Elevated and prolonged exposure to extreme heat is an important cause of excess summertime mortality and morbidity. To protect people from health threats, some governments are currently operating syndromic surveillance systems. However, a lack of resources to support time- and labor- intensive diagnostic and reporting processes make it difficult establishing region-specific surveillance systems. Big data created by social media and web search may improve upon the current syndromic surveillance systems by directly capturing people’s individual and subjective thoughts and feelings during heat waves. The primary objectives of the dissertation are to improve existing heat wave and health surveillance systems by testing current heat exposure metrics, checking system improvements with social media/web search data, and studying differential vulnerability to extreme heat exposure. In order to conduct the research, this dissertation employed two popular statistical techniques: time series and case-crossover analysis. Chapter 2 examines the relationship between the count of heat-related tweets and heat exposure. For this, I collected Twitter data focusing on six different heat-related themes (air conditioning, cooling center, dehydration, electrical outage, energy assistance, and heat) for 182 days from May 7 to November 3, 2014. First, exploratory linear regression associated outdoor heat exposure to the theme-specific tweet counts for five study cities (Los Angeles, New York, Chicago, Houston, and Atlanta). Next, autoregressive integrated moving average (ARIMA) time series models formally associated heat exposure to the combined count of heat and air conditioning tweets while controlling for temporal autocorrelation. Finally, I examined the spatial and temporal distribution of energy assistance and cooling center tweets. The result indicates that the number of tweets in most themes exhibited a significant positive relationship with maximum temperature. The ARIMA model results suggest that each city shows a slightly different relationship between heat exposure and the tweet count. A one-degree change in the temperature correspondingly increased the Box-Cox transformed tweets by 0.09 for Atlanta, 0.07 for Los Angeles, and 0.01 for New York City. The energy assistance and cooling center theme tweets suggest that only a few municipalities used Twitter for public service announcements. The timing of the energy assistance tweets also indicates that most jurisdictions provide heating instead of cooling energy assistance. Chapter 3 aims to investigate the relationship between heat-related web searches, social media messages, and heat-related health outcomes. I collected Twitter messages that mentioned “air conditioning (AC)” and “heat” and Google search data that included weather, medical, recreational, and adaptation information from May 7 to November 3, 2014, focusing on the state of Florida, U.S. I separately associated web data against two different sources of health outcomes (emergency department (ED) and hospital admissions) and five disease categories (cardiovascular disease, dehydration, heat-related illness, renal disease, and respiratory disease). Seasonal and subseasonal temporal cycles were controlled using autoregressive moving average-generalized autoregressive conditional heteroscedasticity (ARMA-GARCH) and generalized linear model (GLM). The results show that the number of heat-related illness and dehydration cases exhibited a significant positive relationship with web data. Specifically, heat-related illness cases showed positive associations with messages (heat, AC) and web searches (drink, heat stroke, park, swim, and tired). In addition, terms such as park, pool, swim, and water tended to show a consistent positive relationship with dehydration cases. However, I found inconsistent relationships between renal illness and web data. Web data also did not improve the models for cardiovascular and respiratory illness cases. These findings suggest web data created by social medias and search engines could improve the current syndromic surveillance systems. In particular, heat-related illness and dehydration cases were positively related with web data. This study also shows that activity patterns for reducing heat stress are associated with several health outcomes. Chapter 2 and chapter 3 suggest that web data could benefit both regions without the systems and persistently hot and humid climates where excess heat early warning systems may be less effective. Chapter 4 investigates whether there is a difference between five different types of heat sensitive health outcomes (cardiovascular disease, dehydration, heat-related illness, renal disease, and respiratory disease) between undocumented immigrants and US citizens. This study also examines if the impact of heat exposure on health by citizenship status is further modified by sex, age, or race/ethnicity. I conducted a case-crossover analysis to assess different heat-related health impact by citizenships, focusing on the warm season (May through September) from 2008 to 2012 in Florida. I reported separate case-crossover models for each health outcome and type of healthcare visit (emergency department, hospitalization). I stratified the data by immigration status and then added interaction terms to understand the impact of sex, age, or race/ethnicity. For both groups, higher temperature raised the risk of all heat-related health outcomes and healthcare visits. This analysis suggest undocumented people (ED: 1.127, 95 % CI: 1.056 ~ 1.204; hospitalization: 1.061, 95 % CI: 1.046 ~ 1.076) have moderately higher renal disease ORs than US citizens (ED: 1.069, 95 % CI: 1.059 ~ 1.078; hospitalization: 1.051, 95 % CI: 1.049 ~ 1.053). In addition, male US citizens had significantly higher ORs than female citizens for both ED (male: 1.080, 95 % CI: 1.076 ~ 1.085; female: 1.060, 95 % CI: 1.056 ~ 1.064) and hospitalization (male: 1.063, 95 % CI: 1.060 ~ 1.066; female: 1.054, 95 % CI: 1.052 ~ 1.057). This study documents some heat and health inequalities between US citizens and undocumented immigrants. / A Dissertation submitted to the Department of Geography in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / 2019 / November 1, 2019. / Google search, Health, Heat wave, Surveillance system, Twitter, Undocumented immigrants / Includes bibliographical references. / Christopher K. Uejio, Professor Directing Dissertation; Yiyuan She, University Representative; James B. Elsner, Committee Member; Sandy Wong, Committee Member.

Thesis (M.A.)--University of Canterbury, 2008. / Typescript (photocopy). Includes bibliographical references (leaves 79-91). Also available via the World Wide Web.

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona, 1984. / Includes bibliographical references (leaves 71-75).

Assessing and managing risks posed by climate variability and change is challenging in the tropics, from both a scientific and a socio-economic perspective. While our understanding of the tropical land rainfall variability and its future projection is highly uncertain, most of the vulnerable countries with a limited adaptation capability are within the tropical band. This dissertation combines a process-based physical understanding with observational analysis to characterize the spatio-temporal changes in the tropical land rainfall during a transient El Niño evolution, with an emphasis on the risk management of the dry and wet extremes. The broad objectives are two-fold: 1) To make better sense of the higher uncertainty in the tropical rainfall response to warming and 2) to improve climate risk management strategies in the tropical developing countries. An ENSO teleconnection mechanism, referred to as the tropical tropospheric temperature or TTT mechanism provides a theoretical framework to study the remote tropical land rainfall behavior during a transient El Niño warming. The TTT mechanism postulates that the tropic-wide free tropospheric warming interacts locally with the deep convection to modulate remote tropical climate. During the growth phase, anomalous free tropospheric temperature causes direct and fast atmospheric adjustments leading to tropospheric stability to deep moist convection and a drier response. Subsequently, during mature phase, a recovery of the initial rainfall deficit follows due to indirect and slower adjustments in surface temperature and humidity fields. In chapter 2 and 3 of this dissertation, the changes in the observed tropical land rainfall characteristics and other climate fields conditional on the growth and mature phase of El Niño warming are investigated and the role of dynamical and thermodynamic mechanisms as hypothesized by the TTT mechanism are elucidated. In chapter 4, an El Niño forecast based early action investment strategy is developed to reduce the socio-economic impacts of rainfall extremes at sub-seasonal to inter-annual lead time scales. In the part I (chapter 2), the analysis is conducted at a regional scale over the tropical Africa. Using the TTT mechanism, a physical explanation is provided for the contrasting rainfall response over the Western Sahel and tropical Eastern Africa during an El Niño. The study finds that the Western Sahel’s main rainy season (July-September) is affected by the growth phase of El Niño through (i) a lack of neighboring North Atlantic sea surface warming, (ii) an absence of an atmospheric column water vapor anomaly over the North Atlantic and Western Sahel, and (iii) higher atmospheric vertical stability over the Western Sahel, resulting in the suppression of mean seasonal rainfall as well as number of wet days. In contrast, the short rainy season (October-December) of tropical Eastern Africa is impacted by the mature phase of El Niño through (i) neighboring Indian Ocean sea surface warming, (ii) positive column water vapor anomalies over the Indian Ocean and tropical Eastern Africa, and (iii) higher atmospheric vertical instability over tropical Eastern Africa, leading to an increase in mean seasonal rainfall as well as in the number of wet days. While the modulation of the frequency of wet days and seasonal mean accumulation is statistically significant, daily rainfall intensity (for days with rainfall >1 mm/day), whether mean, median, or extreme, does not show a significant response in either region. Hence, the variability in seasonal mean rainfall that can be attributed to the El Niño–Southern Oscillation phenomenon in both regions is likely due to changes in the frequency of rainfall. These observed changes agree with the predictions of the TTT mechanism. In the part II (chapter 3), a global scale analysis is performed to more generally characterize the spatio-temporal differences in remote tropical land rainfall response to El Niño warming. The principal conclusions are: 1) during the El Niño growth phase relative to the neutral phase, rainfall decreases. A significant decrease in mean accumulation can be attributed to a significant increase in proportion of dry days and decrease in median and extreme intensity. A significant descent anomaly confirms the vertical stabilization and dominance of dynamical processes. 2) During the mature phase relative to the growth phase, rainfall increases, signifying a recovery from the suppression of deep moist convection. A significant increase in mean accumulation is accompanied by a decrease in proportion of dry days and by an increase in median and extreme intensity characteristics. The significant rise in the moisture field corroborates the dominance of thermodynamic processes. These findings are expected from the TTT mechanism and generalizes the findings of part I to the global scale. In the part III (chapter 4), an El Niño forecast based index insurance policy is developed that can be used as an early action investment instrument. The forecast insurance (FI) design framework is illustrated with an application to El Niño associated flood hazard during the January-February-March-April (JFMA) season over Piura region of Peru. In order to determine the economic utility of the system, a simple cost-loss decision model, incorporating the insurance cost, is developed. The main conclusion is that the proposed El Niño forecast insurance policy with the pre-event Niño1.2 index based trigger has significant reliability and substantial utility for a wide range of policy parameters considered. Relative to a no early action strategy, the advantage of the system generally increases with i) shortening in the lead time from 9 to 1 month, ii) increase in El Niño severity level from 10 to 50 year return period and iii) increase in avoidable loss to cost ratio (LCR) ratio from 1 to 1000. These results and the forecast insurance modeling and utility evaluation frameworks have implications for designing optimal contingent financial instruments for disaster risk reduction and climate change adaptation.

Ph.D., Faculty of Science, University of the Witwatersrand, 2011 / In this study, the linkages between sustainable development, disaster-risk reduction and governance are explored, with reference to climate change adaptation. The purpose of the assessment is to ascertain the effectiveness, or lack thereof, of these inter-linkages with regard to climate change adaptation in South Africa. First, a brief review of theoretical debates on sustainable development, disaster-risk reduction, governance and climate change adaptation is given. Currently, it seems, sustainable development, disaster-risk reduction and governance are viewed exclusively from each other and from climate change adaptation. Some theoretical debates suggest that successful, long-term climate change adaptation can only be accomplished if linkages between these concepts, and practices, where relevant, are recognized in development policies. There is thus, a need to understand the relationships between climate change adaptation and development policy AND their linkages and tradeoffs. Coupled to this understanding, there is also a need to assess the role of institutions as well as institutional barriers that may retard or pose a threat to long-term sustainable adaptation. For this case study, the focus is on the 2004/05 drought that occurred in the Eastern Cape. The drought of 2004/05 was particularly severe. Some parts of the Eastern Cape were declared disaster areas. This declaration prompted responses from the various spheres of government, e.g. national, provincial and local. The intention therefore is, firstly, to gain clarity on the linkages between development/sustainable development policies, disaster-risk reduction and governance in the Province that operated during this period and in the periods following this drought. Secondly, the intention is to understand how the spheres of governance work together in responding to climate-related disasters. Responses from the community reveal that coupled to poor development planning; there is also limited and poor institutional capacity to respond to the direct and indirect impacts of climate variability and change. This poor institutional capacity is further complicated by a lack of coordination between the three spheres of government, i.e. national, provincial and local, as well as across national government departments. It is suggested that first, a good structure of cooperative governance and disaster-risk reduction is needed in South Africa. This structure should allow for multi-faceted and holistic development planning that focuses on saving lives, protecting livelihoods and assets. A good structure of governance should provide an environment that is sustainable and conducive to long-term climate change adaptation. What this case study also reveals is that monetary relief and assistance alone is not an effective response to climate variability and change. What is thus also needed is more vigilant monitoring of development projects and relief-funds as well as coordinated governance of development activities between national, provincial and local governments. Such an organized structure of governance could aid the country in gearing up for climate change adaptation.

Government policy development and implementation is often designed to address different sectors of society in isolation, so social, economic and environmental issues are considered as being distinct from one other. Recently it has been acknowledged that 'working in silos' is not conducive for good governance and so efforts have been made for better co-ordination between different government departments and different spheres of government. Our research findings show the knock on effects of one problem into other areas of people's lives, highlighting why it is vital for policies and programmes to be far better co-ordinated. The different challenges and stresses that people face in their lives interact with one another in complex ways, undermining their capacity to cope with and adapt to future changes, such as those expected under climate change.

Two of the main challenges facing communities and governments in developing countries are the reduction of risks of hydro-meteorological hazards and adaptation to climate change. As climate variability and change impacts are becoming more visible in the form of disasters, and are negatively affecting climate sensitive livelihoods and eroding communities' ability to fully recover, leading to increased vulnerability to subsequent climate risks. The unpredictability of current weather systems, therefore, makes it very difficult for poor governments and households to deal with adverse impacts of climate change. Furthermore, the fragmented approach to DRR and CCA with regards to practice, policy and organisational frameworks for dealing with climate risks is resulting in coordination challenges for the government departments. This study aimed to explore how local households and communities perceive and are experiencing and coping with climate change and drought, and what that means for integrating hydro-meteorological disaster risk reduction and climate change adaptation. The study was carried out in Chirumhanzu district and the methods used for data collection included: 217 household surveys; six focus group discussions; participatory learning actions methods; key informant's interviews and document review. The majority of households owned low value material assets and had low levels of livelihood capitals and this exposed them to the impacts of climate variability and successive droughts. This low adaptive capacity largely affected their ability to engage effective drought risk reduction and adaptation strategies for their livelihood activities in small-scale farming and livestock rearing. Vulnerability to climate risks was exacerbated by seasonal weather forecasts, which were deemed by some households to be unreliable, inaccurate and not easily understood, while others used of indigenous knowledge. Successive droughts affected households' access to food and cash income for other household demands. Other non-climatic factors that contributed to adverse drought impacts at the household level were an emphasis on reactive humanitarian aid approach and the poor economy in Zimbabwe. Additionally, the policy framework for dealing with climate change and drought hazards is fragmented and weak; and is housed in different government departments making it difficult to coordinate and implement. To improve climate risk management, there is need for the government to appreciate that drought risk reduction and climate change adaptation are all about reducing vulnerability. Understanding this, might assist in improving government focus on addressing the underlying causes of vulnerability and mainstreaming DRR and CCA into development processes through addressing specific and generic adaptive capacities. The thesis argues that as long as rural households are involved in climate sensitive livelihood activities and not getting meaningful intervention to diversity and/or better intensify their livelihood activities, they will continue to be vulnerable to successive climate risks. This fragmented approach to dealing with climate risks, is not yielding any successful results with regards to building resilience, risk reduction or adaptation of rural households.

No description available.

No description available.