Tropical Cyclone

4. Discussion and Summary The downscaling technique of Emanuel et al. ( 2008 ) has been applied to the output of a high resolution global climate model for the months of June-October, 2004, and again for the same 5 months of an experiment meant to simulate the effects of global warming. Various metrics of downscaled tropical cyclone activity have been compared to the activity of storms explicitly simulated using the model’s 14 km grid mesh. For the current climate, there is reasonable agreement in the spatial distribution of the explicitly simu- lated and downscaled storms, but the intensity distribution of the explicit events is truncated at around 102 knots, probably owing to the horizontal resolution, which is still too coarse to capture high intensity events. But for the warmer climate there are notable discrepancies between the explicit and downscaled tropical cyclone activity. The down- scaled storms show impressive activity poleward of 30 degrees in the GW simulation, especially in the North Atlantic and North Pacific basins, but also in the Mediterranean, and storms appear in this simulation (but not in CTL) in the Persian Gulf and Caspian Sea.

generally too short and inaccurate for direct use in risk assessment and so contemporary methods of risk assessment rely either on bootstrapping historical storm records or on physics-based approaches. For example, the leading industry risk models are based on large sets of synthetic storm tracks generated from the statistics of historical tracks (Vickery et al. 2000 ; Yonekura and Hall 2011 ) and with intensity evolutions that are based on observed intensities and their relationships to environmental predictors such as sea surface temperature. Such models are heavily empirical and thus largely constrained to tropical cyclone climatology over the period of the historical tropical cyclone record. Thus, it is difficult to account for the effects of climate change, whether natural or anthropogenic, on time scales too long to have been well sampled in the historical tropical cyclone record. To circumvent these limitations of historically based risk assessment, efforts have been made in recent years to simulate tropical cyclones using physics-based models driven by the large-scale climate conditions provided by global reanalysis data and/or by global climate models. For example, Emanuel et al. ( 2006 ) generated synthetic hurricane tracks using a beta-and-advection model (Marks 1992 ) driven by large-scale environmental flow synthesized from global climate reanalysis data, comparing the results to a Markov-chain approach based on historical storm tracks. Genesis points in both cases were drawn from probability density analyses based on historical genesis locations, and intensities were calculated using a simple coupled ocean–atmosphere tropical cyclone model (CHIPS; Emanuel et al. 2004 ). Likewise, Colbert et al. ( 2013 ) used a beta-and-advection model to synthesize tropical cyclone tracks from large-scale flow statistics, though they did not try to predict intensity. Emanuel et al. ( 2008 ) developed a synthetic event generator entirely free from historical storm data. They generated storms by randomly seeding large-scale climate states and then using the CHIPS intensity model to determine which seeds survive, tracking the events using the beta-and-advection model driven by the large-scale environmental flow, as before. Because such a method is based purely on physics applied to large-scale environmental conditions, it can be driven by climate model output as well as by global reanalysis data, allowing for quantification of the effects of climate variability and trends on tropical cyclone genesis, tracks, and intensity.

because of the weak wind speeds of their storms (cf. Table 3 ). Table 3 also presents a crucial variable for studying tropical cyclones, the lifetime maximum intensity. In observations, the lifetime maximum intensity (LMI; Elsner et al. 2008 ) has bimodal characteristics. For de- riving the LMI, we used the 10-m wind speed or surface wind speed depending on the availability of the data. 1 The bimodal distribution arises from differences in LMI and lifetime duration between the northernmost and southernmost tropical cyclones. The southernmost trop- ical cyclones tend to reach higher intensities, because they stay longer over warm tropical waters with clima- tologically low vertical wind shear ( Kossin et al. 2010 ). The first peak in LMI appears for the northernmost tropical cyclones, which achieve an average of 34 m s 21 associated with shorter tracks and colder SSTs. The sec- ond peak appears for the southernmost tropical cyclones, which reach a higher LMI with a mean intensity of 44 m s 21 , associated with longer tracks and warmer SSTs. The explicit tropical cyclone simulations do not simulate the bimodality of LMI of the northernmost and south- ernmost tropical cyclones, the mean LMI is nearly the same for all clusters and all the simulations. Furthermore, the intensity of the tropical cyclones is underestimated by most the models (CMCC_E, GISS_E, FSU_E, GFS_E, GSFC_E, HG3A, and WRF_E). This is a common bias of climate models (e.g., Yoshimura et al. 2006 ; Knutson et al. 2007 ; LaRow et al. 2008 ; Walsh et al. 2013 ), because of low model horizontal resolution and convective pa- rameterization. Even WRF_E ( Table 3 ), with the highest resolution (around 0.25 8), has a mean LMI weaker than the observed LMI despite realistic peak intensities. The two other models (CAM5_E and GFDL_E) tend to overestimate the LMI, which could be due to their higher horizontal resolution.

temperature and moisture in the modeling of the wind field in the tropical cyclone boundary layer.. 21.[r]

Key words: Height-resolving wind-field model, Boundary layer, Scale analysis, Tropical cyclone... Introduction.[r]

2. Watershed years: 1943–68 On 27 July 1943, Army Air Corps Colonel Joseph B. Duckworth, with navigator Lieutenant Ralph O’Hair, took an Air Force AT-6 trainer from an airfield in Texas and became among the first aviators to penetrate the eye of a hurricane. By the late 1940s, airborne re- connaissance of hurricanes and typhoons had become routine. This marked the beginning of a highly pro- ductive era of direct measurements of tropical cyclones above the surface; before this time what few measure- ments were made came from chance passages of storms over ships, islands, and coastal regions. While these earlier encounters sufficed to establish a general clima- tology of tropical cyclones as well as the structure of their surface wind, rain, and pressure fields, almost nothing was known about their three-dimensional structure. An important advance was, however, made by Bernhard Haurwitz ( Haurwitz 1935 ), who inferred that the per- turbation pressure could not vanish at altitudes much below 10 km, based on application of the hydrostatic equation to temperature measurements in typhoon eyes as they passed over high mountains. Further advances would await the advent of aircraft-based measurements. The rapid implementation of routine airborne re- connaissance was largely motivated by a series of wartime U.S. naval disasters involving violent storms. Among these were the sinking of the destroyer USS Warrington in the Great Atlantic Hurricane of September 1944, with the loss of 248 mariners. Although too late for the Warrington, that hurricane was the first to be surveyed by meteorological ra- dar as the storm later passed east of the U.S. Naval Air Station at Lakehurst, New Jersey. Scarcely three months later, Admiral William Halsey unwittingly sailed Task Force 38 of the U.S. Third Fleet directly into the center of vicious Typhoon Cobra, which sank three destroyers and took the lives of 790 sailors. Some of the ships were outfitted with radar, and thus Cobra became the second tropical cyclone recorded on radar. An image from such a radar, reproduced in Fig. 15-1 , shows an unmistakable rain-free eye, an eyewall, and spiral rainbands, but radar operators of that era had no training to interpret images like these. 3

Edited by Kerry A. Emanuel, Massachusetts Institute of Technology, Cambridge, MA, and approved February 28, 2019 (received for review January 15, 2019) Volcanic eruptions can affect global climate through changes in atmospheric and ocean circulation, and therefore could impact tropical cyclone (TC) activity. Here, we use ensemble simulations performed with an Earth System Model to investigate the impact of strong volcanic eruptions occurring in the tropical Northern (NH) and Southern (SH) Hemisphere on the large-scale environ- mental factors that affect TCs. Such eruptions cause a strong asymmetrical hemispheric cooling, either in the NH or SH, which shifts the Intertropical Convergence Zone (ITCZ) southward or northward, respectively. The ITCZ shift and the associated surface temperature anomalies then cause changes to the genesis poten- tial indices and TC potential intensity. The effect of the volcanic eruptions on the ITCZ and hence on TC activity lasts for at least 4 years. Finally, our analysis suggests that volcanic eruptions do not lead to an overall global reduction in TC activity but rather a redistribution following the ITCZ movement. On the other hand, the volcanically induced changes in El Niño-Southern Oscillation (ENSO) or sea-surface temperature do not seem to have a signifi- cant impact on TC activity as previously suggested.

central American mountains increased, which is most notable at the 925 mb level... Note that the southerly winds to the south of the region has increased in magnitude, indica[r]

The study used a single-column radiative convective model and an aerosol-cloud parameterization scheme to demonstrate that sulfate aerosols have a significant effect on [r]

Keywords: tropical cyclone; south-west Indian ocean; cloud-resolving model; ocean–wave–atmosphere coupling; climate modeling 1. Introduction Due to the possible devastating combination of extreme winds, torrential precipitation, storm surge, and high waves, tropical cyclones (TC) are a major threat for impacted territories. This is particularly true in the South-West Indian Ocean (SWIO) that represents 10–12% of the global TC activity [ 1 , 2 ] and includes several countries with precarious economies and fragile infrastructures, making them highly vulnerable to cyclonic risks. Madagascar, which ranks among the poorest countries in the world, is regularly affected by TCs. Between 1999 and 2016, 34 systems directly hit Madagascar, 10 of which as a TC at the time of landfall [ 3 ]. In March 2004, TC Gafilo—the most intense TC ever observed in the SWIO at this date—made landfall in the north-east of Madagascar, leaving more than 200,000 victims, 400 deaths, and damages estimated at USD 250 million. In 2017, TC Enawo hit almost the same region of Madagascar at the peak of its intensity (maximum wind speed of 57 m s −1 ). The associated storm surge, high winds and heavy rains led to 81 deaths, 300,000 victims, heavily damaged structures, and severe losses in rice fields (damages estimated at ∼ USD 137 million). Mozambique is also frequently hit by tropical depressions with 16 direct hits between 1999 and 2016 [ 3 ]. In 2019, TC Idai made landfall in the region of Beira. Wind gusts and torrential rainfall devastated the crops, destroyed more than 29,500 houses, and damaged tens of thousands of others, leading to a major humanitarian crisis. More than 1000 people died and 2.6 million victims were reported. The damages were estimated at USD 2 billion in the impacted region (Mozambique, Malawi, Zimbabwe, Madagascar). Six weeks later, TC Kenneth, after devastating the Comoros archipelago, hit the north of Mozambique, in the region of Pemba, worsening the humanitarian, sanitary, and economic situation of the country. This high exposure to natural disaster adds to the dependence on agriculture and natural resources and leads to severe humanitarian crises, which are most of the time under-reported in the media.

Figures 1 to 4 present the total number – worldwide – of storms recorded in the IBTrACS database, and the numbers by category over 1970-2014. Focusing on the period 1990-2014, trends are difficult to identify. We detect no significant trend over 4. As explained on the IBTrACS website (on May 24, 2018): “The intent of the IBTrACS project is to over- come data availability issues. This was achieved by working directly with all the Regional Specialized Meteorological Centers and other international centers and individuals to create a global best track dataset, merging storm information from multiple centers into one product and archiving the data for public use. One of the goals of the project is for the data processing methods to remain open, such that desired user feedback on data quality is more easily collected. Also, data provenance is completely recorded so all observations and corrections, either through rigorous quality control or user feedback, may be tracked. Data are then provided in various formats given the diversity of the tropical cyclone (TC) data user community. The World Meteorological Organization non-gonvernment domain Tropical Cyclone Programme has endorsed IBTrACS as an official archiving and distribution resource for tropical cyclone best track data. The IBTrACS project: Contains the most complete global set of historical tropical cyclones available; Combines information from numerous tropical cyclone datasets; Simplifies inter-agency comparisons by providing storm data from multiple sources in one place; Provides data in popular formats to facilitate analysis; Checks the quality of storm inventories, positions, pressures, and wind speeds, passing the information on to the user.

déterminer l’anticipation du phénomène à partir des connaissances des cyclones, des consignes de vigilance et de l’expérience (vécue ou transmise). La temporalité de l’avant crise couvre surtout les jours et heures avant le cyclone Irma, mais s’étend également à toute la période cyclonique. Les résultats des entretiens ont montré une population qui déclare s’informer dès le début de la saison cyclonique avec un suivi régulier des vigilances météorologiques plusieurs fois par jour à l’approche du cyclone. Les sources d’informations consultées proviennent des différents médias (illustration 5) que les populations consultent durant les périodes cycloniques (avant Irma). Parmi les sources les plus consultées, les interrogés se sont principalement tournés vers des sites internet qu’ils qualifient de sites spécialisés (SXM cyclone ou Weather Channel) ainsi que les réseaux sociaux. Le réseau social Facebook permet notamment de faire le lien avec les institutions : par exemple les populations se sont largement renseignées sur la page Facebook de la préfecture. De plus, les échanges par SMS avec les proches, la famille et les amis alimentent les informations. Celles-ci ont circulé à l’échelle de Saint-Martin et Saint-Barthélemy, des Antilles, mais aussi avec la métropole. « C’est ma famille de métropole qui m’a prévenu, là j’ai su que ce serait important » (X., quartier Hope Estate). L’île est empreinte de culture américaine, les interrogés se sont donc également tournés vers les chaînes de télévision et sites internet américains. Quelques personnes férues de navigation ont par ailleurs consulté des sites spécifiques de météo marine donnant des précisions sur les vitesses et directions des vents (Windy ou Windguru par exemple). La radio et la télévision représentent les sources privilégiées (respectivement 27 et 24 personnes) puis suivent les sites internet (17 personnes), Facebook (11 réponses) et la presse locale (6 réponses).

0 , 0). 2. Motivations from static analysis, discrete event systems, and mean pay- off games Tropical polyhedra have been recently involved in static analysis by abstract interpreta- tion [AGG08]. It has been shown that they allow to automatically compute complex invari- ants involving the operators min and max which hold over the variables of a program. Such invariants are disjunctive, while most existing techniques in abstract interpretation are only able to express conjunctions of affine constraints, see in particular [CC77, CH78, Min01].

Além das frutas tradicionais que o mundo comercializa em grande escala, o Brasil tem potencial para ampliar a sua participação no comercio de frutas tropicais e [r]

A citricultura pode também vir a ser uma ótima opção para os pequenos produtores, como ocorre na região do Recôncavo baiano (Cruz das Almas e outros municípios da região) e no estado d[r]

Winter extratropical cyclone influence on seabird survival: variation between and within common eider populations Loreleï Guéry, Sébastien Descamps, K. Hodges, Roger Pradel, B Moe, S. Hanssen, K. Erikstad, G. Gabrielsen, H. Gilchrist, Stéphanie Jenouvrier, et al.

Over the last years, many research works covered the different architectures for implementing TDCs in FPGA. Most of these works focused on the improvements that could be made to the TDCs in terms of resolution and linearity [1]-[4], but they did not cover the different timing issues that should be taken in consideration when implementing a TDC on FPGA. This work aims to introduce a full design methodology of a TDC on a low cost Intel FPGA Cyclone V development kit, covering the most important timing considerations when integrating this TDC in a global system.

L’archipel du Vanuatu Post-cyclone Pam. Identifier les vulnérabilités et les capacités de résilience sociétale et environnementale par un RETEX sur le long terme Benjamin Pradel, Tony Rey, Stéphanie Defossez, Monique Gherardi, Loic Le Dé, Frédéric Leone

Honduras, 2 millions de personnes sur 6 au total vivraient directement ou indirectement de la caféiculture. Elles seraient 10 millions en Éthiopie [Wirren 2002-2003]. Ces exemples ne sont pas exceptionnels. La valeur du café par rapport à son poids lui permet de supporter, sans réel problème, des coûts de transport, même élevés, d’autant que le produit conserve durablement toutes ses qualités gustatives après les divers traitements transformant la « cerise », qui a été cueillie, en café « parche » (le parche est une fine pellicule entourant tou- jours le grain de café lorsqu’il a été dépulpé et démucillé), puis en café « vert » lorsqu’il est « déparché » au moment de l’exportation. Ces traitements ne demandent que des moyens techniques accessibles aux plus modestes des producteurs. Grâce à tous ces avantages, le café a pu se diffuser dans une large part du monde tropical, y compris dans les régions les plus reculées des massifs montagneux. UNE NOUVELLE HIÉRARCHIE DES GRANDS PAYS PRODUCTEURS

3. The Workshops [ 9 ] To address the science underlying the TAV, and in a effort to expand and coordinate international observational programs in the tropical Atlantic towards a sustained observ- ing system a meeting was held in Miami, May 4 through 7, 1999 (http://www.aoml.noaa.gov/phod/COSTA/). As a fol- low up to this meeting and following one of its recommen- dations, the CLIVAR Workshop on Tropical Atlantic Variability took place at UNESCO, Paris, September 3 through 6, 2001. The main objectives of the Paris workshop were to review advances in science since the Miami work- shop, and to coordinate international efforts toward a sus- tained observing system in support of understanding, modeling and predicting TAV. The Paris workshop was sponsored by the International CLIVAR Project Office and was attended by 120 scientists from 10 different countries. During the first three days of the workshop, keynote presentations were made during the morning hours directed at the role of local air-sea interaction in TAV, the influence of the tropical Atlantic atmosphere/ocean circulation on climate variability over the Americas and Africa, and the interaction between TAV and the large-scale atmosphere/ ocean circulation. A discussion of its relation to the NAO and the MOC was followed by a discussion on the shallow overturning cells and cross-gyre exchange in the region, and by a presentation of potential links to decadal, secular variability and climate change. The third morning was dedicated to the observing system and to discuss observa- tional needs for prediction. Interactive poster sessions were held in the afternoons. At the end of the day, the attendants met in a plenary session, in which rapporteurs lead a discussion of the oral and poster presentations that took place during that day. Following the oral and poster pre- sentations, three working groups were created. The respon- sibility of the Working Groups was to summarize the science and the observational needs based on the workshop discussions, and to make recommendations towards an implementation plan. At the conclusion of the workshop, a summary of the activities as well as the working group recommendations were presented to the international CLI- VAR Atlantic Implementation Panel (http://www.clivar.org/ publications/wg_reports/atlantic/3rdmeet.pdf.) for consider- ation in the formulation of an implementation plan for tropical Atlantic research. In this volume, a compilation of papers presented during the poster sessions of the work- shop, and published by GRL, are presented. These papers provide the foundation for the recommendations forwarded to CLIVAR.