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High-resolution climate model simulations and a tropical cyclone damage model are used to simulate the economic damage due to tropical cyclones. The damage model produces reasonable damage estimates compared to observations. The climate model produces realistically intense tropical cyclones over a historical simulation, with significant basin scale correlation of the inter-annual variability of cyclone numbers to observed storm numbers. However, the climate model produces too many moderate tropical cyclones, particularly in the N. Pacific. Annual mean cyclone damage with simulated storms is similar to estimates with the damage model and observed storms, and with actual economic losses. Ensembles of future simulations with different mitigation scenarios and different sea surface temperatures (SSTs), as well as societal changes, are used to assess future projections of cyclone damage. Damage estimates are highly dependent on the internal variability of the coupled system. Using different ensemble members or different SSTs affects damage results by ±40 %. Experiments indicate that despite decreases in storm numbers in the future, strong landfalling storms increase in E. Asia, increasing global storm damage by ∼50 % in 2070 over 2015. Little significant benefit is seen from mitigation, but only one ensemble is available. Projected increases in vulnerable assets increase damage from simulated storms by more than threefold (∼300 %, assuming no adaptation) indicating future growth will swamp potential changes in tropical cyclones.

There are several different estimates of the observed cyclone damage potential of tropical cyclones based on observations of size, intensity and track. For the analysis of climate model data, previous work identified an index, the cyclone damage potential climate index (CDPClimate), based on relative sea surface temperature (SST) and tropical cyclone steering flow to estimate the damage potential in climate models. Using millennia-long climate models, CDPClimate is estimated for the North Atlantic basin and compared against values from reanalyses and the observed damage potential. The peak in SSTs in the cyclone main development region with respect to the tropical mean SSTs is smaller in these models than reanalyses, resulting in smaller variations in CDPClimate. Although the year 1995 had the highest observed cyclone damage potential, the year 2010 is a maximum for CDPClimate in the reanalysis data. The models exceed this 2010 value in less than 1% of model years. Using a model with 100 ensemble members, the variability in CDPClimate is examined further. The interannual variability of the ensemble mean results has a very high correlation (R = 0.95) with reanalyses. The high decadal variability is evident and interannual variability is found to have increased during the 30 years after 1981 relative to those prior. The 2010 ensemble mean value is exceeded in other years by individual ensemble members 1.1% of the time. The results from this study suggest that although it is possible to exceed the observed CDP, this is rare in the current climate. However, this study does not consider changes as we move to future climates.

The potential changes in the characteristics and damage potential of three of the most damaging tropical cyclone (TC) events (Haiyan 2013, Bopha 2012, Mangkhut 2018) in the Philippines have been simulated using the pseudo global warming (PGW) technique. Simulations were performed using the Weather Research and Forecasting model at 5 km resolution with cumulus parameterization (5 kmCU) and 3 km without cumulus parameterization (3 kmNoCU), with PGW deltas derived from a selection of the CMIP6 models. We found that re-forecasting the three TCs under future warming leads to more intense TCs, with changes in maximum wind of 4%, 3%, and 14% for the 5 kmCU runs, and 14%, 4%, and 12% for the 3 kmNoCU runs of Typhoon Haiyan, Bopha, and Mangkhut, respectively. The changes in track, translation speed, and size are relatively small. The TC cases have a higher impact potential in the future, as expressed by the cyclone damage potential index, ranging from ~ 1% to up to 37% under the SSP5-8.5 scenario. Based on the pre-industrial runs, climate change has had, so far, only a weak influence on TC intensity and not much influence on track, translation speed, and size. Simulations without convective parameterization show similar changes in the sign of the projected TC intensity response, but different signals of change in translation speed and size.

Several warm‐core cyclones in the Mediterranean, which were analyzed in the literature, are studied using ERA5 reanalysis, to identify the environment where they develop and distinguish tropical‐like cyclones from non‐tropical warm‐core cyclones. Initially, the cyclone phase space is analyzed to distinguish the cyclones that have a symmetrical deep warm core. Subsequently, the temporal evolution of several parameters is considered, including the distance between the area of maximum tangential wind speed and the cyclone center. Some differences are observed between the cyclones analyzed: one category of cyclones develops in areas of moderate‐low baroclinicity and intense convective processes, as occurs in tropical cyclones. Another group of cyclones develops in a strongly baroclinic environment with weak convective processes and intense vertical wind shear, as occurs in warm seclusions. Two cyclones, showing similarities with polar lows, are also identified. Plain Language Summary Mediterranean tropical‐like cyclones (TLCs) are damaging weather systems, which form over the Mediterranean Sea, resembling tropical cyclones. These cyclones can drive important socio‐economic losses in coastal areas. However, due to their small size and the relatively recent investigation of these cyclones, there is currently no robust categorization of which Mediterranean cyclones can be considered TLC. Therefore, in this work, we propose a method to differentiate cyclones that attain actual tropical‐like characteristics in part of their lifetime, as they develop a warm core through intense convective processes. The main results of this study show that part of the analyzed cyclones have features similar to tropical cyclones. Another group of cyclones has a behavior closer to extratropical cyclones with weak convective processes in an environment with intense vertical wind shear, as occurs in warm seclusions or polar lows. The results of this study propose a key to identify the Mediterranean cyclones that have tropical‐like characteristics. Key Points A new method to detect cyclones with tropical‐like characteristics in the Mediterranean has been developed Part of the cyclones with deep warm core developed in low baroclinicity and with intense convective processes, as tropical cyclones Some cyclones have weak convective processes and intense vertical wind shear environments, such as warm seclusions or polar lows

Tropical cyclones (TCs) that make landfall over India’s east coast are responsible for significant loss of life along affected coastlines. TCs forming over the Bay of Bengal (BoB) region in October, November, and December have, in the past, intensified significantly at the time of landfall. The effects of climate change on TCs of different strengths and their characteristics such as track, intensity, precipitation, and convective available potential energy over the BoB region have not been well studied. This study explores the effects of climate change on two TCs of very severe cyclonic storm (VSCS) category (TC Vardah and TC Madi), and two other TCs of extremely severe cyclonic storm (ESCS) category (TC Hudhud and TC Phailin) formed over BoB, both in the short term (2035) and long term (2075). The high-resolution Weather Research and Forecasting (WRF) model is used to simulate the TCs under current and future climate conditions. The simulated TC track and intensity in the current climate agree well with the observations. To explore the impacts of climate change on TCs, the mean climate change signal, computed from future projections of the Community Climate System Model (CCSM4) in different representative concentration pathway (RCP) scenarios, is added to current climate conditions by using the pseudo global warming method. Results show a climate change-related reduction in TC translation speed, deepening of TC core, increased maximum surface wind, and increased precipitation over land in future RCP (4.5, 6.0, and 8.5) scenarios. The TCs in future RCP scenarios are seen to be more intensified compared to current climate simulations. Results demonstrate that all VSCS and ESCS category TCs considered in this study are likely to further intensify to the next higher category level with respect to their current classification, particularly in the far future RCP 6.0 and in the far future RCP 8.5 scenarios. The cyclone damage potential index of TC Vardah, TC Hudhud, and TC Phailin is projected to increase in a future warming climate.

Typhoon Faxai hit Japan in 2019 and severely damaged the Tokyo metropolitan area. To mitigate such damages, a good track forecast is necessary even before the typhoon formation. To investigate the predictability of the genesis and movement of a precursor vortex and its relationship with the synoptic‐scale flow, 100‐member ensemble simulations of Typhoon Faxai were performed using a 14‐km mesh global nonhydrostatic atmospheric model, which started from 16 different initial days (i.e., 1,600 members in total). The results show that the model could predict an enhanced risk of a Faxai‐like vortex heading toward Japan 2 weeks before landfall, which was up to 70%. The reason for the enhancement was a rapid increase in the members reproducing a precursor vortex from 15 to 12 days before landfall in Japan. In addition, the upper‐tropospheric vortex played an essential role in the track simulation of Faxai. Plain Language Summary Tropical cyclones severely damage coastal regions yearly. Typhoon Faxai hit Japan in 2019 and severely damaged buildings, power grids, and cell phone networks in the Tokyo metropolitan area. To mitigate such damages, better track forecast is necessary even from the timing before typhoon formation. A large ensemble member (1,600‐member in total) and high‐resolution (14‐km) simulation was performed to investigate the genesis and movement of the precursor vortex of Faxai in 2019 and its relationship with the synoptic‐scale environmental flow using a global nonhydrostatic atmospheric model on the Supercomputer Fugaku. The results show the model could predict an enhanced risk of a Faxai‐like vortex heading toward Japan 2 weeks before landfall. A reason for the enhancement was a rapid increase in the members reproducing a precursor vortex from 15 to 12 days before landfall in Japan. In addition, the upper‐tropospheric vortex played an essential role in the movement of the Faxai‐like vortex. Key Points A 1,600‐member ensemble simulation in total for Typhoon Faxai (2019) was performed using a 14‐km mesh nonhydrostatic atmospheric model The model successfully predicts the risk of Faxai's landfall in Japan 2 weeks in advance Reproducibilities of the precursor vortex and upper‐tropospheric vortex yield good prediction of the formation and track of Faxai

Full recovery of coral reefs from tropical cyclone (TC) damage can take decades, making cyclones a major driver of habitat condition where they occur regularly. Since 1985, 44 TCs generated gale force winds (≥17 metres/second) within the Great Barrier Reef Marine Park (GBRMP). Of the hurricane strength TCs (≥H1-Saffir Simpson scale; ≥ category 3 Australian scale), TC Yasi (February, 2011) was the largest. In the weeks after TC Yasi crossed the GBRMP, participating researchers, managers and rangers assessed the extent and severity of reef damage via 841 Reef Health and Impact Surveys at 70 reefs. Records were scaled into five damage levels representing increasingly widespread colony-level damage (1, 2, 3) and reef structural damage (4, 5). Average damage severity was significantly affected by direction (north vs south of the cyclone track), reef shelf position (mid-shelf vs outer-shelf) and habitat type. More outer-shelf reefs suffered structural damage than mid-shelf reefs within 150 km of the track. Structural damage spanned a greater latitudinal range for mid-shelf reefs than outer-shelf reefs (400 vs 300 km). Structural damage was patchily distributed at all distances, but more so as distance from the track increased. Damage extended much further from the track than during other recent intense cyclones that had smaller circulation sizes. Just over 15% (3,834 km2) of the total reef area of the GBRMP is estimated to have sustained some level of coral damage, with ~4% (949 km2) sustaining a degree of structural damage. TC Yasi likely caused the greatest loss of coral cover on the GBR in a 24-hour period since 1985. Severely impacted reefs have started to recover; coral cover increased an average of 4% between 2011 and 2013 at re-surveyed reefs. The in situ assessment of impacts described here is the largest in scale ever conducted on the Great Barrier Reef following a reef health disturbance.

Coastal ecosystems provide a range of services including erosion prevention, clean water provision and carbon sequestration. With climate change, the rapid change in frequency and intensity of tropical cyclones may alter the composition of the ecosystems themselves potentially degrading the services they provide. Here we classify global ecoregions into dependent, resilient and vulnerable and show that a combined 9.4% of the surface of all terrestrial ecosystems is susceptible to transformation due to cyclone pattern changes between 1980–2017 and 2015–2050 under climate scenario SSP5-8.5 using the STORM model. Even for the most resilient ecosystems already experiencing winds >60 m s −1 regularly, the average interval between two storms is projected to decrease from 19 to 12 years which is potentially close to their recovery time. Our study advocates for a shift in the consideration of the tropical cyclone impact from immediate damage to effects on long-term natural recovery cycles. The authors model the impact of changing tropical cyclone activity on coastal ecosystems. Under SSP5-8.5, by 2050 nearly 10% of terrestrial ecosystems will be at risk from changing tropical cyclone frequency, threatening the recovery potential of even the most resilient ecoregions.

Assessing the adverse impacts caused by tropical cyclones has become increasingly important as both climate change and human coastal development increase the damage potential. In order to assess tropical cyclone risk, direct economic damage is frequently modeled based on hazard intensity, asset exposure, and vulnerability, the latter represented by impact functions. In this study, we show that assessing tropical cyclone risk on a global level with one single impact function calibrated for the USA – which is a typical approach in many recent studies – is problematic, biasing the simulated damage by as much as a factor of 36 in the north West Pacific. Thus, tropical cyclone risk assessments should always consider regional differences in vulnerability, too. This study proposes a calibrated model to adequately assess tropical cyclone risk in different regions by fitting regional impact functions based on reported damage data. Applying regional calibrated impact functions within the risk modeling framework CLIMADA (CLIMate ADAptation) at a resolution of 10 km worldwide, we find global annual average direct damage caused by tropical cyclones to range from USD 51 up to USD 121 billion (value in 2014, 1980–2017) with the largest uncertainties in the West Pacific basin where the calibration results are the least robust. To better understand the challenges in the West Pacific and to complement the global perspective of this study, we explore uncertainties and limitations entailed in the modeling setup for the case of the Philippines. While using wind as a proxy for tropical cyclone hazard proves to be a valid approach in general, the case of the Philippines reveals limitations of the model and calibration due to the lack of an explicit representation of sub-perils such as storm surges, torrential rainfall, and landslides. The globally consistent methodology and calibrated regional impact functions are available online as a Python package ready for application in practical contexts like physical risk disclosure and providing more credible information for climate adaptation studies.

Using 42 years of reanalysis data, we investigate regional, storm‐relative characteristics of three groups of Atlantic tropical cyclone intensification: slightly, moderately, and rapidly intensifying. Probability density functions are distinct between these groups for vertical wind shear, sea surface temperature (SST), and radius of maximum winds (RMW), but less so for relative humidity (RH). In the Gulf of Mexico and southern North Atlantic, shear and RMW are good predictors. In the open Atlantic, north of 22°N, shear and SST are the best predictors. In the Caribbean, weaker relationships suggest low statistical predictability in a region where RI cases increased between 1980–2000 and 2001–2021. Of our storm‐relative variables tested, increasing SST appears to be most closely connected to the 36% increase in rapidly intensifying events between the two periods, whereas shear and RH are not significantly more favorable. The variability across regions, periods, and variables motivates further investigation. Plain Language Summary Although many damaging Atlantic tropical cyclones intensify rapidly during their lifetime, forecasting how rapidly they will intensify remains difficult. To address this, we need to better understand whether the conditions in a storm's environment can help identify whether it will intensify rapidly or more slowly, and whether these results change in different regions. Using 42 years of data, we find that wind shear (change in wind speed and direction with height) and ocean temperature are useful to discriminate whether a storm may intensify rapidly versus slowly across the basin, although there is variability in the results. Humidity is less useful. Our results vary by region. The Caribbean shows lower discrimination between intensification rates, highlighting potential difficulties in predicting intensification in this region. This is concerning since the number of rapidly intensifying events has risen sharply in the Caribbean between 1980–2000 and 2001–2021. We also find that the trends in intensifying storms during these 21‐year periods vary by region. The most consistent signal related to the rise in intensifying events is the increasing ocean temperature. Key Points Atlantic basin rapid intensification trends vary by region, with the greatest increases between 1980–2000 and 2001–2021 south of 22°N Wind shear, sea surface temperature, and radius of maximum winds are useful discriminators between intensification rates Storm‐relative environmental variable trends vary by region, with sea surface temperatures often related to regional intensity change trends