This special issue of Global Environmental Research with a sub-title “Wind Disaster Risk and Global Environment Change” is planned as one of the important activities of the Global COE Program of Tokyo Polytechnic University (TPU) to contribute to society facing these problems by observing and analyzing wind-related disaster risk from this point of view. The idea of publishing this special issue was discussed by the co-editors at the Fourth International Symposium on Wind Effects on Buildings and Urban Environment held in Tokyo, March 4-6, 2009. This international symposium, focusing on Cooperative Actions for Disaster Risk Reduction, was co-hosted by the International Association for Wind Engineering, the United Nations University, the United Nations International Strategy for Disaster Reduction Secretariat, the Asian Disaster Reduction Center and the Global COE Program of Tokyo Polytechnic University. This symposium provided a stimulating and constructive forum for researchers from various disciplines related to natural disasters, engineers, educators, government officers and citizens specializing in disaster risk reduction, giving them the opportunity to exchange and share the latest scientific and technical information. The co-editors of this special issue reached the consensus that a part of the important output of this symposium, i.e. wind-related disaster risk reduction, should be widely disseminated to the public via an authorized international journal focusing on the increasing social significance of wind-related disaster risk reduction activities together with discussions on climate change and global warming phenomena.

 The purpose of this special issue is to overview the current status and recent trends of extreme wind events in various places around the world, related disaster risk reduction activities, and climate change effects on extreme wind events in order to identify future activities that we should undertake. It first discusses the trends of extreme wind events and climate change from the meteorological viewpoint. It then discusses extreme wind events and damage assessment in Japan and the US from the wind engineering viewpoint. Climate change and wind-related disaster risk reduction activities in China and India are introduced, because the situations and actions taken in these countries with the world largest populations are very important for human society. It also discusses floods and storm surges accompanying extreme wind events and recent trends in estimating the combined effects of wind and water. The lifetimes of buildings and structures can be 50 years, 100 years or more, and the effects of future trends of strong wind events should be considered in estimation of the design wind load level. Then, climate change and its effects on the design wind speed estimation method for buildings and structures are also discussed. Climate change effects are also important in the assessment of air quality and heat environment in densely built city areas, which have a severe impact on daily human life. These environmental problems are also discussed with reference to typical examples of the high-density cities of Hong Kong and Tokyo. Since these disaster risk reduction problems and urban environmental problems cannot be independent of central and local government policies or social systems, steps taken by the building and insurance industries and government organizations for extreme wind related disasters in the US, Japan, and Europe are introduced. Finally, a recent innovative trial to establish an engineering virtual organization (EVO) using cyber-infrastructures to offer a sophisticated platform available for education, research and practice of structural design of infrastructures and world-wide disaster risk reduction activities is introduced.

 This article first describes winds at regional, local and micro-scales, with special reference to methods of observation and analysis according to the order of the scales. It shows that in studies at the regional scale, data derived from detailed observations under the network of second-order observation stations and AMeDAS arranged by the Japan Meteorological Agency are utilized, with the main study method being synoptic climatology. These were established in Japan in 1960s and 1970s. Mesh data were used mainly in the 1980s and 1990s, presenting air flow in accordance with directions of prevailing upper winds, geostrophic winds, etc.

 Regarding local-scale winds, the main topic of concern has been winds occurring under certain topographical conditions such as in V-shaped or U-shaped valleys, on mountain ridges and along valley side slopes. Observations are carried out by temporally organized groups using instruments and indicators such as wind-shaped trees. These studies started in Europe in the early 20th century, but have been undertaken intensively since the 1950s. For agricultural land use, wind power stations, air pollution, city planning and construction of structures such as bridges, tall buildings, highways, etc., knowledge of local wind conditions has been an essential requirement in recent years. It has been pointed out that these conditions should be elucidated not only by model simulation or wind tunnel experiments, but also by field observations. This article also considers changes in winds on the local scale under the influence of global warming, taking an example of Santa Ana in the U.S.A. It discusses risk problems based on recent studies. The last part deals with risk management and insurance, based on statistics available.

 This paper reviews assessments of possible changes in tropical cyclone frequency and intensity due to global warming, based on climate change projection experiments using atmospheric general circulation models (AGCMs). Recent experiments with relatively high-resolution (mesh size of about 100 km or less) models consistently indicate that the global frequency of tropical cyclones is likely to decrease due to global warming. In contrast to the global frequency, the regional tropical cyclone frequencies projected by various models significantly differ from each other. On the other hand, high-resolution (mesh size of about 50 km or less) models consistently indicate that future tropical cyclone intensity (wind and precipitation) is likely to increase. As a result, the number of intense tropical cyclones may increase, even if the total number of tropical cyclones decreases. The reduction in tropical cyclone frequency and the increase in tropical cyclone intensity are likely to be qualitative. However, it should be noted that there are enormous quantitative uncertainties in these projections of possible changes in tropical cyclone frequency and intensity, particularly among the regional changes. The large uncertainties in the projections of regional changes in tropical cyclone frequency and intensity make it difficult to use the information effectively in planning measures to mitigate the future wind disaster risk associated with tropical cyclones in particular regions. Reducing the uncertainty in climate change projections, particularly regarding regional changes, is the most demanding task for climate change research.

 The focus of this paper is on severe windstorm events, including severe thunderstorms, tornadoes and tropical cyclones affecting the United States. Recent trends in hurricane and tornado activity in the U.S., and some scientific controversy regarding secular changes and possible connections to global warming are examined. Even though damages due to windstorms continue to rise, fatalities in the U.S. have generally declined, with the exception of major hurricane impacts like KATRINA, 2005. I attribute this dichotomy to movement of the population to areas more prone to windstorms, while the accuracy of warnings has improved. The history of scientific post-storm damage surveys in the U.S. is summarized, and the importance of such surveys for future assessments of windstorm phenomena vs. global climate change is highlighted. Finally, I examine the various windstorm disaster risks across the U.S., and find that those risks are increasingly dependent on construction practices (including manufactured housing) and the development of adequate shelters.

 In Japan, natural disasters that threaten the living environment of developed urban areas include typhoons and tornadoes, as well as earthquakes. The change of urban form that has occurred with the vertical development of buildings for the past 30 years has brought about new wind damage situations, and the damage caused by Typhoon Mireille in 1991 highlighted the need for new wind-resistant measures. In addition, there is growing concern about the destructive damage caused by recent extreme winds accompanying tornadoes in residential areas and around public facilities. Even if the area damaged is not so large, the sudden occurrence of tornadoes has sometimes caused serious destruction and many casualties within some districts. The wind-induced damage which occurred from 2005 to 2006 as the result of tornadoes led to operation of a new tornado advisory system. Some measures have recently been taken to reduce damage caused by wind-borne debris, which is continuously generated under extreme winds. This report describes recent extreme wind-induced damage in Japan and discusses some features of the damage. Although the damaged objects were mainly buildings and structures, an accident involving a railcar and another involving temporary construction are also noted.

 Extreme winds are one of the most severe natural disasters, causing massive losses of human life and possessions in China. This paper gives an overview on wind disasters in China, covering extreme-wind climates, affected areas, hazard phenomena and losses. It is clear that, though almost all kinds of extreme-wind climates have existed in China, the main wind hazard is typhoons. The paper analyzes and predicts trends in wind disasters and losses occurring in China. It provides a rough discussion of the relationship between global warming and tropical cyclones landing in China as an attempt to present what information is available, though it is hard to form any conclusion. It also briefly introduces some significant activities and major research plans on wind engineering and hazard mitigation initiated and supported by the Chinese government and Natural Science National Foundation. It is encouraging to note that the trends in losses of life caused by severe wind disasters in mainland China appear to have declined over the recent decade thanks to the efforts of the Chinese government and authorities.

 Global warming due to concentration of greenhouse gases is a reality. Consequent changes are likely in the ocean and earth-atmosphere systems. This raises the apprehension of future increases in the frequency of high-velocity winds generated by weather systems, like tropical cyclones, and their destructive potentials.

 Our present knowledge on the subject is inadequate and incomplete. The projections available through different climate models are at variance. Nevertheless, if past behaviour is an indication of the future, then it should be possible to project likely changes in high-velocity winds generated by tropical cyclones through the analysis of past data.

 With this in view, we analyzed historical data on tropical cyclones, which are one of the sources of high velocity winds in the tropics, for the period of 1891 to 2008 along with recent sea-surface temperature data of the North Indian Ocean region (the Bay of Bengal and Arabian Sea). It has been observed that though the sea-surface temperature in the North Indian Ocean region (NIO) is increasing (as projected by global circulation models), the frequency of tropical cyclones, including intense ones, is decreasing. Analysis of estimated/observed highest maximum winds associated with TCs of very severe intensity (winds with 64 knots or more) observed every year during 1965 to 2008 in the NIO region also do not show any increasing trend. This result, though tentative (short data series), led us to conclude that there may not be any significant increase in high velocity winds and consequent coastal impact due to global warming in the NIO region. However, this does not exclude the occurrence of some individual cyclones of catastrophic nature that has been observed also in the past.

 Despite concentrated global efforts, flood losses worldwide are increasing. This trend is expected to escalate further due to climate change. The fourth IPCC report has explicitly warned against increase of flood disasters and recent studies show increased rainfall intensities and intensification of typhoons will contribute to further increases in flood losses. Estimation of potential flood losses can play an important role in investing for prevention as well as for developing financial instruments to reduce flood risks. However only a few flood loss estimation models consider damages caused by wind effects during flooding. The main objective of this paper is to review and discuss the possibility of incorporating wind induced damage in urban flood loss estimation. First, an overview of the flooding loss and damage models is presented. Then, the applicability of flood loss estimation with inundation using loss function and inundation modeling is introduced as an example in the Ichinomiya River basin, Japan. Finally, an approach to estimate wind damage loss on urban buildings during flooding events is introduced. The flood damage case study is then analyzed to assess wind related damage.

 Any analysis of extreme values of wind climates with the aim of estimating design wind speeds suffers from statistical uncertainties induced by short observation periods. As can be shown by simulations, the identification of the ‘true’ parameters of a wind climate is virtually impossible. The situation is even worse if trends have to be evaluated in regard to their statistical significance. These trends may result from a global climate change which can also affect the wind climate. Particularly, trends in the number and intensity of storms seem to be of basic interest. The corresponding probability distributions are the Poisson distribution with describing parameter λ (average number of storms per year) and the Generalized Pareto distribution with describing parameters s and k (scale parameter and shape factor). The new approach is based on the idea that the observed parameters λ_obs, s_obs, k_obs and the corresponding linear trends a_λ, _obs and a_s, _obs may be obtained from a large range of combinations of λ, s, k, a_λ and a_s. In a first step, the probabilities are calculated that the observed parameters will be obtained for each combination λ, s, k, a_λ and a_s. Then, for each combination, the design wind speed is calculated (for different target probabilities and different design working lives). Sorting the obtained design wind speeds and integrating their corresponding probabilities gives the non-exceedance probability curve of the probable design wind speed. The ‘best estimate’ is obtained by applying a target confidence interval of 75% which has previously been introduced as a basis for estimating design values for the resistance side when dealing with statistical uncertainties from confined ensembles. Based on the findings for the wind climate at Düsseldorf, it is strongly recommended to consider non-stationary features when specifying design wind speeds. The assumption of a stationary wind climate may lead to considerable underestimations of design wind speeds.

 Global environmental changes, especially global warming, are becoming an issue for urban designers. Coupled with that are the issues of life in mega- and high-density cities and the urban heat island effect. Hong Kong is one of the world’s highest-density cities, with over sixty thousand persons per square kilometre in its urban areas. High-rise, bulky and closely packed buildings are the norm; and this increases the urban heat island intensity and reduces urban air ventilation. Given Hong Kong’s hot, humid tropical summers, high heat stress can be expected in the urban environment. Since 2003, the Hong Kong Government has commissioned studies on this issue. An air ventilation assessment (AVA) study was carried out. In addition, an urban climatic map was drafted based on an evaluation of human thermal comfort. A study of intra-urban temperature variations is underway and their possible implications to localised hot days and hot spells is being investigated. The criticality of rising intra-urban temperature and decreased wind speed can be established. This has provided objective input for planning actions in the form of urban climatic recommendation maps. This work is on-going in Hong Kong. The present paper summarises some of these projects and documents the study process and rationale.

 This article introduces the current status of outdoor environmental issues in Japan. The outdoor environment is greatly affected by various wind conditions, commonly classified as strong winds and weak winds. Strong winds around high-rise buildings have been a social issue for over 30 years in Japan. Wind tunnel experiments have been conducted to assess the environmental impact of strong winds at the pedestrian level and are regarded as the most reliable prediction method. In recent years, the application of computational fluid dynamics (CFD) to this problem has been rapidly gaining popularity and acceptance. To ensure the reliability of CFD simulations, " AIJ guidelines for practical applications of CFD to pedestrian wind environments around buildings " was published in 2007.

 On the other hand, weak wind conditions can also cause problems. Air pollution and the heat island phenomenon intensify when winds are weak. Owing to the restrictions on the emission of harmful substances from both facilities and automobiles, Japan’s outdoor air quality has been gradually improving. The annual averages of NO₂, SO₂, CO, and SPM concentrations have remained steady or gradually declined in recent years, but the compliance rates with the Environmental Quality Standards have been extremely low for photochemical oxidants. Heat island phenomenon currently occurs in most cities in Japan due to anthropogenic heating, poor urban ventilation and oversized artificial ground coverage areas. Several countermeasures have been taken by governmental authorities. Recent researches on urban heat islands in Japan are reviewed in the latter part of this article.

 Worldwide property losses due to extreme wind events are escalating. While a large portion of the increases in loss can be attributed to population growth and concentration of property value in vulnerable areas, global climate change could exacerbate losses in vulnerable areas and make buildings and infrastructure in relatively safe areas more vulnerable. Advances in forecasting and warning systems can provide residents with time to seek shelter from natural perils; in some cases (e.g., hurricanes), advanced warning can enable property owners to take steps to reduce losses. However, last–minute property protection measures are usually limited to activating pre-established systems. The best overall building protection system remains passive strength and mitigation measures that are built into a structure.

 This paper explores steps taken by the building and insurance industries that clearly indicate that losses can be reduced and risks managed in ways that provides greater individual and community security and economic stability. It is also clear that efforts to reduce or reverse the rapid escalation of property losses as the result of natural perils face significant technical, systemic and public policy challenges. This paper identifies weaknesses in current extreme wind loss reduction efforts and offers suggestions for enhancing these efforts. It also identifies steps that are being taken by the building and insurance industries that will mitigate future damage to existing buildings and structures and help society adapt to existing risks and changes in risk due global climate change.

 The paper discusses the implications of natural disasters due to extreme wind events on urban habitat construction and introduces Action-C26, a joint effort among European academic institutions under the European Cooperation in Science and Technology (COST) program. With several activities, Action-C26 aims at assessing the risk for catastrophic events in urban areas. In this context, a proposed framework for risk-based decision making is presented and used to physically model the case of a typhoon. Furthermore, critical components of such models are discussed in detail, including particularly the case of a full-scale study that involves wind and structural monitoring of a low building. Typical results from this study are presented and their integration with the risk assessment model is discussed.