Hurricane Landfall Research Articles

The Price of Extreme Weather Uncertainty: Evidence from Hurricanes

We investigate the uncertainty dynamics surrounding extreme weather events through the lens of option and stock markets by identifying market responses to the uncertainty regarding both potential hurricane landfall and subsequent economic impact. Stock options on firms with establishments exposed to the landfall region exhibit increases in implied volatility of 5-10 percent, reflecting impact uncertainty. Using hurricane forecasts, we show that landfall uncertainty and potential impact uncertainty are reflected in prices before landfall. We find no evidence that markets incorporate better hurricane forecasts than those from NOAA. Improvements to hurricane forecasts could have economically significant effects in financial markets.

Fecal indicator bacteria levels at beaches in the Florida Keys after Hurricane Irma

Hurricanes cause infrastructure failures which can lead to contamination of impacted areas. The objective of the current study was to evaluate whether Hurricane Irma contributed towards sewage contamination of coastal beaches. Through this study we evaluated indicators of fecal pollution (fecal indicator bacteria [FIB], enterococci and fecal coliform) and physico-chemical parameters (salinity, pH, turbidity, and temperature) in coastal waters of the Florida Keys shortly after the hurricane. To augment available county sampling data, two sets of sampling efforts were conducted; one focused on collecting samples spatially throughout the Keys to assess whether areas closer to hurricane landfall were more highly impacted. The second was to collect temporally intensive samples at one location during falling tide to evaluate the hypothesis of groundwater contamination. Samples were analyzed for FIB using a new method called timed appearance of culture signal (TACS), which was subsequently calibrated using traditional membrane filter and chromogenic substrate methods. Results showed that coastal beach waters were characterized by elevated but sporadic levels of fecal indicator bacteria up to two months after the hurricane. Spikes were not correlated with physico-chemical characteristics of the water. Our temporally intensive sampling effort did not support the hypothesis that groundwater was a source of elevated FIB. Competing factors could have played a role in the sporadic nature of the FIB levels after the hurricane. We suggest that beach erosion may have flushed out sediments at beaches closer to the hurricane landfall location thereby improving water quality during dry conditions. We also suggest that during wet conditions a source of FIB could include runoff from debris staging areas. Preemptive beach closures immediately after the hurricane were justified due to the sporadic nature of FIB contamination.

Normalized hurricane damage in the continental United States 1900–2017

Direct economic losses result when a hurricane encounters an exposed, vulnerable society. A normalization estimates direct economic losses from a historical extreme event if that same event was to occur under contemporary societal conditions. Under the global indicator framework of United Nations Sustainable Development Goals, the reduction of direct economic losses as a proportion of total economic activity is identified as a key indicator of progress in the mitigation of disaster impacts. Understanding loss trends in the context of development can therefore aid in assessing sustainable development. This analysis provides a major update to the leading dataset on normalized US hurricane losses in the continental United States from 1900 to 2017. Over this period, 197 hurricanes resulted in 206 landfalls with about US$2 trillion in normalized (2018) damage, or just under US$17 billion annually. Consistent with observed trends in the frequency and intensity of hurricane landfalls along the continental United States since 1900, the updated normalized loss estimates also show no trend. A more detailed comparison of trends in hurricanes and normalized losses over various periods in the twentieth century to 2017 demonstrates a very high degree of consistency. Reducing direct economic losses from disasters is part of mitigating disaster impacts. This study presents an update to the leading dataset on normalized US hurricane losses in the continental United States from 1900 to 2017.

Market anomalies and disaster risk: Evidence from extreme weather events

We document strong abnormal effects due to U.S. landfall hurricanes over the period 1990 to 2017 on stock returns and illiquidity across portfolios of stocks sorted by market equity (ME), book-to-market equity ratio (BE/ME), momentum, return-on-equity (ROE), and investment-to-assets (I/A). ROE- and I/A-related long/short factors are insensitive to hurricanes, while size-, BE/ME-, and momentum-related factors are extremely sensitive to these extreme weather events. Long and short legs react differently and high momentum stocks experience a negative impact on their returns an order of magnitude greater than other stocks. Abnormal illiquidity is only able to account for a small fraction of the observed abnormal returns.

Hurricanes as a Major Driver of Coastal Erosion in the Mississippi River Delta: A Multi-Decadal Analysis of Shoreline Retreat Rates at Bay Champagne, Louisiana (USA)

The Louisiana shoreline is rapidly retreating as a result of factors such as sea-level rise and land subsidence. The northern Gulf of Mexico coast is also a hotspot for hurricane landfalls, and several major storms have impacted this region in the past few decades. A section of the Louisiana (USA) coast that has one of the highest rates of shoreline retreat in North America is the Caminada-Moreau headland, located south of New Orleans. Bay Champagne is a coastal lake within the headland that provides a unique opportunity to investigate shoreline retreat and the coastal effects of hurricanes. In order to examine the influence of hurricanes on the rate of shoreline retreat, 35 years (1983–2018) of Landsat imagery was analyzed. During that period of time, the shoreline has retreated 292 m. The overall rate of shoreline retreat, prior to a beach re-nourishment project completed in 2014, was over 12 m per year. A period of high hurricane frequency (1998–2013) corresponds to an increased average shoreline retreat rate of >21 m per year. Coastal features created by multiple hurricanes that have impacted this site have persisted for several years. Bay Champagne has lost 48% of its surface area over the last 35 years as a result of long-term shoreline retreat. If shoreline retreat continues at the average rate, it is expected that Bay Champagne will disappear completely within the next 40 years.

Tasseled cap transformation for assessing hurricane landfall impact on a coastal watershed

Tasseled cap transformation (TCT) has been used to observe relationships among soil moisture, vegetation cover, and canopy condition. Time series Landsat satellite images of high resolution may provide continuous and accurate observations of the land surface, which can be further analyzed using the TCT for natural hazard events. This study explores the use of a unique dispersion phenomenon of TCT for observing the dynamics of vegetation cover and landscape changes due to a major hurricane landfall in the United States. This is based on the Landsat images taken during the Hurricane Bob event, during which the hurricane made landfall in the highly developed New England area in late August 1991. A unique comparison of the TCT time series plots illustrating the relative TCT dispersion phenomenon, which addresses the landfall’s profound impact on the Mattapoisett River watershed in 1991, reflects the interactions among biosphere, atmosphere, hydrosphere, and lithosphere in hurricane-prone regions. This analysis can be done without the use of ground truth data and can be further supported by the multitemporal and multidimensional change detection of box plots in terms of brightness and greenness to gain more biophysical interpretation. Findings unveil an inherent earth system process via the varying levels of dispersion among brightness, greenness, and wetness over the coastal watershed with environmental sustainability implications.

The Impact of Hurricane Maria on the Vegetation of Dominica and Puerto Rico Using Multispectral Remote Sensing

As the worst natural disaster on record in Dominica and Puerto Rico, Hurricane Maria in September 2017 had a large impact on the vegetation of these islands. In this paper, multitemporal Landsat 8 OLI and Sentinel-2 data are used to investigate vegetation damage on Dominica and Puerto Rico by Hurricane Maria, and related influencing factors are analyzed. Moreover, the changes in the normalized difference vegetation index (NDVI) in the year 2017 are compared to reference years (2015 and 2016). The results show that (1) there is a sudden drop in NDVI values after Hurricane Maria’s landfall (decreased about 0.2) which returns to near normal vegetation after 1.5 months; (2) different land cover types have different sensitivities to Hurricane Maria, whereby forest is the most sensitive type, then followed by wetland, built-up, and natural grassland; and (3) for Puerto Rico, the vegetation damage is highly correlated with distance from the storm center and elevation. For Dominica, where the whole island is within Hurricane Maria’s radius of maximum wind, the vegetation damage has no obvious relationship to elevation or distance. The study provides insight into the sensitivity and recovery of vegetation after a major land-falling hurricane, and may lead to improved vegetation protection strategies.

Storm Tracks Predict Land-To-Sea Sediment Transfer: Erosional Patterns from the Upper Ordovician (Hirnantian) in the Oslo Region, Norway

Recent refinements in nomenclature with an emphasis on member-level organization of Hirnantian strata from Norway’s Oslo region provide a useful way to grasp depositional processes recorded in the last stage of the Ordovician system. Found in outcrops throughout the many small islands of the Oslofjord and the adjacent Bunnefjord, the multifaceted Langøyene Formation is differentiated into older, mostly stratiform deposits of sandstone and oolitic limestone in the Skauern, Høyerholmen, and Pilodden Members and younger cut-and-fill breccias and conglomerates in the Kalvøya Member. Combinations of sandy and calcareous conglomerates derived from erosion of the foregoing Høyerholmen, Pilodden, or older lithologies make up the preponderance of pebble- to boulder-size materials in the basal parts of the Kalvøya Member. As many as three generations of overlapping incisions into fully hardened strata resulted from cyclic changes in sea level during late Hirnantian time. Conditions under which channels were eroded and filled were variable, dependent on position along a preexisting gradient from land to sea. From 50 to 100 m in cross section, proximal streambeds accumulated fill characterized by chaotic debris-flow deposits as well as more normal riverine deposits with imbricated clasts. In a middle-slope position, channels exhibit a more mature organization, with clast-supported deposits that formed as flood jets off river mouths. Most distal in position, true tidal channels are eroded into strata with trace fossils diagnostic of normal marine conditions. Evidence from additional parts of the paleocontinent of Baltica in Norway, Sweden, and Estonia supports the argument that land-to-sea sediment transfer was induced by hurricane-related tropical storms bringing catastrophic rainfall to the Fennoscandian Shield. Similar evidence from other Late Ordovician continents is reviewed in the context of hurricane landfall patterns based on predictable storm tracks.

A unified framework for performance-based wind engineering of tall buildings in hurricane-prone regions based on lifetime intervention-cost estimation

Accurate evaluation of structural performance is necessary in modern tall building design. In wind engineering, the current approach employed by researchers is the Monte-Carlo sampling method. Structural failure probability is calculated by combining structural fragility curves with the random variability of wind speed and direction, depending on local wind climate. In the hurricane-prone regions of the USA, wind climate and its effects on building response require accurate assessment of wind-induced structural performance.This paper proposes a simulation framework for tall buildings that combines fragility analysis with local wind climate information to evaluate structural vulnerability. Hurricane wind climate information directly considers maximum wind speed, wind direction along with their correlation at hurricane landfall. Consequently, structural fragility surfaces will be generated, conditional on these two variables. This result will be used to examine lifetime intervention cost accumulation, associated with nonstructural damage on the building façade, and to determine an “optimal” wind-direction-dependent building orientation.

Examining the Effects of Objective Hurricane Risks and Community Resilience on Risk Perceptions of Hurricanes at the County Level in the U.S. Gulf Coast: An Innovative Approach

Communities' risk perceptions can influence their abilities to cope with coastal hazards such as hurricanes and coastal flooding. Our study presents an initial effort to examine the relationship between community resilience and risk perception at the county level, through innovative construction of aggregate variables. Using the 2012 Gulf Coast Climate Change Survey merged with historical hurricane data and community resilience indicators, we first apply a spatial statistical model to construct a county-level risk perception indicator based on survey responses. Next, we employ regression to reveal the relationship between contextual hurricane risk factors and community resilience on one hand and county-level perceptions of hurricane risks on the other. Results of this study are directly applicable in the policymaking domain as many hazard mitigation plans and adaptation policies are designed and implemented at the county level. Specifically, two major findings stand out. First, the contextual hurricane risks represented by peak height of storm surge associated with the last hurricane landfall and land area exposed to historical storm surge flooding positively affect county-level risk perceptions. This indicates that another threat of hurricanes—wind risks—needs to be clearly communicated with the public and fully incorporated into hazard mitigation plans and adaptation policies. Second, two components of community resilience—higher levels of economic resilience and community capital—are found to lead to heightened perceptions of hurricane risks, which suggests that concerted efforts are needed to raise awareness of hurricane risks among counties with less economic and community capital.

Examining the influence of professional emergency management coordinators driving preparedness and resilience on university campuses.

To characterize the compliance with disaster management recommendations of ensuring a full-time, dedicated professional is responsible for coordinating disaster management programs. This research targets a subset of institutions of higher education (IHEs) in the United States at risk of annual hurricane threats or having experienced an active shooter incident near campus. A comprehensive Web-based assessment was conducted to determine the Web presence of emergency management of 265 IHEs with student enrollment greater than 2,000 in coastal states at risk of annual Atlantic Hurricane landfalls. Results were displayed spatially using ArcGIS. Although the Web sites of 91 percent of IHEs with enrollment greater than 20,000 displayed easily accessible information on a dedicated professional leading emergency management, only 42 percent of the Web sites of those IHEs with enrollment between 10,000 and 20,000 did so. As enrollment declined, the compliance rate declined. Compliance rates for IHEs with different enrollments were as follows: 6,001-9,999, 30 percent; 3,001-6,000, 23 percent; 2,000-3,000, 13 percent. A full-time, dedicated professional coordinating emergency preparedness is a best practice as evidenced by various accrediting bodies, but this practice is not mandated for IHEs. Our results suggest that proximity to significant annual hurricane threats does not influence the adoption of this recommendation. Despite IHEs being core stakeholders in assuring disaster resilience, gaps exist in preparedness practice.

Continental U.S. Hurricane Landfall Frequency and Associated Damage: Observations and Future Risks

AbstractContinental United States (CONUS) hurricane-related inflation-adjusted damage has increased significantly since 1900. However, since 1900 neither observed CONUS landfalling hurricane frequency nor intensity shows significant trends, including the devastating 2017 season.Two large-scale climate modes that have been noted in prior research to significantly impact CONUS landfalling hurricane activity are El Niño–Southern Oscillation on interannual time scales and the Atlantic multidecadal oscillation on multidecadal time scales. La Niña seasons tend to be characterized by more CONUS hurricane landfalls than El Niño seasons, and positive Atlantic multidecadal oscillation phases tend to have more CONUS hurricane landfalls than negative phases.Growth in coastal population and regional wealth are the overwhelming drivers of observed increases in hurricane-related damage. As the population and wealth of the United States has increased in coastal locations, it has invariably led to the growth in exposure and vulnerability of coastal property along the U.S. Gulf and East Coasts. Unfortunately, the risks associated with more people and vulnerable exposure came to fruition in Texas and Florida during the 2017 season following the landfalls of Hurricanes Harvey and Irma. Total economic damage from those two storms exceeded $125 billion. Growth in coastal population and exposure is likely to continue in the future, and when hurricane landfalls do occur, this will likely lead to greater damage costs than previously seen. Such a statement is made recognizing that the vast scope of damage from hurricanes often highlights the effectiveness (or lack thereof) of building codes, flood maps, infrastructure, and insurance in at-risk communities.

Hurricane impact on biogeochemical processes in a tropical dry forest in western Mexico

Extreme climatic events (ECEs), such as hurricanes, significantly affect biogeochemical processes and their intensity is predicted to increase. We documented the immediate and short-term consequences of the impact of Hurricane Jova on such processes in primary undisturbed tropical dry forest at the Estación de Biología Chamela. Data from our long-term study in five contiguous small watersheds were used to provide perspective to the hurricane effects. Carbon (C), nitrogen (N) and phosphorus (P) concentrations and fluxes were measured in runoff, litterfall and surface litter prior to and after the impact of the hurricane. Dissolved organic P (DOP) and C (DOC) concentrations in runoff in October 2011 (hurricane landfall), were 96% and 33% greater than the mean concentrations of previous months (July–September 2011). Nutrient fluxes were 10 (DOC), 3 (DON) and 15 (DOP) times greater than the mean fluxes of previous months. N and P concentrations in litterfall collected a few days after the hurricane were not different from pre-disturbance values, but P concentrations were much greater a few months after disturbance. Nutrient fluxes from vegetation to soil due to Jova represented 42% (N) and 30% (P) of the mean annual N and P litterfall fluxes in the period 2010–2012. Surface litter P concentrations, but not N, were very high at the end of the dry season following Jova. In addition, N and P stocks at this time were about 40% higher than the mean stocks in May of the other years of study. Both, litterfall and surface litter P returned to average values about a year after the hurricane. Litterfall P use efficiency, but not N, decreased after hurricane impact. Mean residence time of organic matter and N were similar and did not respond to hurricane disturbance, whereas P residence time was lower and decreased after the hurricane. Overall, our results indicate that hurricane Jova can be identified as an ECE. The return to pre-disturbance values within a year after the event suggests a high degree of short-term biogeochemical resilience in this forest. Variables related to N were resistant (no change) to the impact of Jova and to rainfall variability, but those related to P were highly responsive, quickly recovering to pre-disturbance and long-term dynamics. The P response to the hurricane and its relevance in the ecosystem are discussed in terms of long-term forest productivity and resilience under a scenario of increasing extreme hydrometeorological events.

A historical analysis of the mature stage of tropical cyclones

ABSTRACTThe characteristics of tropical cyclone intensity and size during the mature stage are presented. Rooted in the classic description by Herbert Riehl, the mature stage is identified as the period from the time of lifetime maximum intensity to the time of lifetime maximum size. This study is the first to analyse the global climatology of the mature stage of tropical cyclones in detail. Three basic features at the mature stage are observed: the reduction of intensity, the outward expansion of the eyewall, and the increase of tangential wind in the outer primary circulation. Globally, about a quarter of tropical cyclones undergo the mature stage. High intensity at the end of the immature stage favours the likelihood of the occurrence of the mature stage. The intensity reduction during the mature stage is considerable with nearly three‐quarters of cyclones decreasing by more than 10%, which makes the conventional ‘steady‐state’ presumption questionable. The increase in the radius of damaging‐force wind is typically about 50 km, while the decrease in maximum wind speed is typically 20% at the mature stage. However, the average integrated kinetic energy and hence destructive potential increases substantially by about 70%. This is consistent with our finding that most of the highly damaging landfalling hurricanes undergo a mature stage. Intensity downgrades during the mature stage may be misinterpreted as they are mostly not accompanied by an overall danger reduction.

Spatial and temporal variations in resilience to tropical cyclones along the United States coastline as determined by the multi-hazard hurricane impact level model

The United States coastline, where over 50% the population lives, is vulnerable to hurricanes along the East and Gulf coasts. However, the question remains as to whether these two areas are equally resilient to a landfalling hurricane. In addition, while it is assumed that improvements in building codes, infrastructure protections, and changing policy over the past century have been effective in reducing the impacts to a community from historically extreme hurricane events, such an assumption is still to be validated. Here, a multi-hazard artificial neural network model is used to address these questions. The Hurricane Impact Level Model is the first prediction model to utilize machine-learning techniques (artificial neural networks) to established complex connections between all meteorological factors (wind, pressure, storm surge, and precipitation resulting in inland flooding) of a tropical cyclone and how those interact with the location of landfall to produce a certain level of economic damage. This model allows for a more all-encompassing assessment of how the impacts of tropical cyclones vary along the coastline. The Hurricane Impact Level Model was trained with historical tropical cyclone events from 1998 to present day, resulting in established locational associations to modern relevant building codes and mitigation practices. Simulating the meteorological factors from historical events allows for a new assessment of economic impact changes due to infrastructure improvements and policy adaptations over time. In essence, if Hurricane Sandy hit Florida instead of New York, it would have a lower economic impact due to lower population density and more stringent building codes, which the artificial neural network has associated with the latitudes and longitudes within the state of Florida. If the Galveston hurricane were to hit today, the seawall would not succeed in lowering the economic impact to the Texas coastline. Over the years, significant effort has been put in to improving the resiliency of the United States coastline, mainly in the southern states, but it has not been enough to counteract the effects of population growth within coastal counties.

Differential resilience to extreme climate events of tree phenology and cavity resources in tropical dry forest: Cascading effects on a threatened species

The influence of climate extremes on tree phenology or cavity resources, and the consequences for threatened species, are poorly understood. We determined flowering and fruiting phenology, and availability of tree-cavities and snags in deciduous and semi-deciduous tropical dry forest from 2009 to 2016, prior-to and following landfall by hurricanes Jova (category 2) in 2011 and Patricia (category 4) in 2015. We also evaluated reproduction of the threatened Lilac-crowned Amazon (Amazona finschi) throughout this period. Flowering and fruiting phenology was reduced during the first year post-hurricanes, but the major Hurricane Patricia had a significantly greater impact on fruit and flower abundance than the minor Hurricane Jova. ARIMA time series modelling indicated that deciduous forest recovered phenological cycles by the second-year post-Hurricane Jova, but semi-deciduous forest demonstrated a level shift in fruiting phenology after landfall by this minor hurricane. Subsequent landfall by the major Hurricane Patricia then also led to a level shift in fruiting phenology of deciduous forest. Tree-cavity and snag resources were reduced by half post-Hurricane Jova, and remaining tree-cavities had significantly wider entrances, while snags were of larger diameters. Hurricane Jova caused the loss of 35.6% of Lilac-crowned Amazon nest-sites, whereas a significantly greater 61.5% of parrot nest-sites were lost after Hurricane Patricia. New nest-cavities used by parrots after Hurricane Jova had significantly wider entrances compared to nest-cavities used prior to hurricane impacts. In the first breeding season post-hurricanes, Lilac-crowned Amazons delayed nest initiation, few pairs nested, and reproductive output was low. Parrot reproduction recovered in subsequent years post-Hurricane Jova, but parrot reproductive output remained among the lowest recorded for the species in the second year post-Hurricane Patricia. Our results suggest that deciduous forest may be resilient to low-level hurricane impacts, such as Hurricane Jova, but semi-deciduous forest did not recover over the five years after hurricane landfall, and is a priority for restoration management. By comparison, the major Hurricane Patricia may be characterized as an extreme climatic event as this was coupled with extreme ecological responses of level-shifts in fruiting phenology, and had severe cascading effects on nest-site availability and reproduction for large-bodied cavity-nesting species, such as the Lilac-crowned Amazon.

A sequential model to link contextual risk, perception and public support for flood adaptation policy

The economic damage from coastal flooding has dramatically increased over the past several decades, owing to rapid development in shoreline areas and possible effects of climate change. To respond to these trends, it is imperative for policy makers to understand individuals' support for flood adaptation policy. Using original survey data for all coastal counties of the United States Gulf Coast merged with contextual data on flood risk, this study investigates coastal residents' support for two adaptation policy measures: incentives for relocation and funding for educational programs on emergency planning and evacuation. Specifically, this study explores the interactive relationships among contextual flood risks, perceived flood risks and policy support for flood adaptation, with the effects of social-demographic variables being controlled. Age, gender, race and partisanship are found to significantly affect individuals' policy support for both adaptation measures. The contextual flooding risks, indicated by distance from the coast, maximum wind speed and peak height of storm surge associated with the last hurricane landfall, and percentage of high-risk flood zone per county, are shown to impact one's perceptions of risk, which in turn influence one's support for both policy measures. The key finding –risk perception mediates the impact of contextual risk conditions on public support for flood management policies – highlights the need to ensure that the public is well informed by the latest scientific, engineering and economic knowledge. To achieve this, more information on current and future flood risks and options available for mitigation as well as risk communication tools are needed.

Effects of Boundary Layer Vertical Mixing on the Evolution of Hurricanes over Land

Abstract After a hurricane makes landfall, its evolution is strongly influenced by its interaction with the planetary boundary layer (PBL) over land. In this study, a series of numerical experiments are performed to examine the effects of boundary layer vertical mixing on hurricane simulations over land using a research version of the NCEP Hurricane Weather Research and Forecasting (HWRF) Model with three landfalling hurricane cases. It is found that vertical mixing in the PBL has a strong influence on the simulated hurricane evolution. Specifically, strong vertical mixing has a positive impact on numerical simulations of hurricanes over land, with better track, intensity, synoptic flow, and precipitation simulations. In contrast, weak vertical mixing leads to the strong hurricanes over land. Diagnoses of the thermodynamic and dynamic structures of hurricane vortices further suggest that the strong vertical mixing in the PBL could cause a decrease in the vertical wind shear and an increase in the vertical gradient of virtual potential temperature. As a consequence, these changes destroy the turbulence kinetic energy in the hurricane boundary layer and thus stabilize the hurricane boundary layer and limit its maintenance over land.

Effects of Vertical Eddy Diffusivity Parameterization on the Evolution of Landfalling Hurricanes

Abstract As a result of rapid changes in surface conditions when a landfalling hurricane moves from ocean to land, interactions between the hurricane and surface heat and moisture fluxes become essential components of its evolution and dissipation. With a research version of the Hurricane Weather Research and Forecasting Model (HWRF), this study examines the effects of the vertical eddy diffusivity in the boundary layer on the evolution of three landfalling hurricanes (Dennis, Katrina, and Rita in 2005). Specifically, the parameterization scheme of eddy diffusivity for momentum Km is adjusted with the modification of the mixed-layer velocity scale in HWRF for both stable and unstable conditions. Results show that the change in the Km parameter leads to improved simulations of hurricane track, intensity, and quantitative precipitation against observations during and after landfall, compared to the simulations with the original Km. Further diagnosis shows that, compared to original Km, the modified Km produces stronger vertical mixing in the hurricane boundary layer over land, which tends to stabilize the hurricane boundary layer. Consequently, the simulated landfalling hurricanes attenuate effectively with the modified Km, while they mostly inherit their characteristics over the ocean and decay inefficiently with the original Km.

Linking hurricane landfalls, precipitation variability, fires, and vegetation response over the past millennium from analysis of coastal lagoon sediments, southwestern Dominican Republic

We reconstructed the late-Holocene environmental history of a coastal lagoon in semi-arid southwestern Hispaniola through multiproxy analysis of a sediment core, including pollen, macroscopic and microscopic charcoal, loss-on-ignition analysis (LOI), stable isotope analysis, bulk density, and magnetic susceptibility. Four chronological accelerator mass spectrometry radiocarbon dates indicated that our core represents the past ~1000 years. We interpreted ten hurricanes events over the past millennium from high-resolution geological proxies, LOI data, and ostracod valve stable oxygen isotope data, thus producing the first long record of hurricanes from the Dominican Republic. Geological proxies indicated a high-energy event abruptly changed the ecosystem state of our core site from a shallow mangrove wetland to a lacustrine environment ~330 cal yr BP. We interpret the driver of that event to be the landfall of a strong hurricane that initiated lowland flooding, mangrove mortality, and subsequent peat collapse at the core site. Pollen data indicated that during the relatively moist Medieval Warm Period (MWP), hurricanes led to temporary declines in tropical dry forest taxa that recovered within several decades following disturbance. By comparison, during the relatively arid Little Ice Age (LIA), when precipitation was highly variable in the circum-Caribbean, closely spaced hurricanes seemed to delay forest recovery. Sedimentary charcoal concentrations revealed increased fire activity after inferred hurricane landfalls in the MWP, providing evidence of a link between enhanced biomass and fuel availability during moister periods and burning in recently disturbed dry forests and scrub of our semi-arid study region. Our interpretations of increased aridity and precipitation variability, indicated by alternating thin layers of microbial mats with evaporite layers, along with more frequent hurricanes from ~330 cal yr BP to present, generally agree with other sedimentary records from the circum-Caribbean, and may be linked to a more southerly position of the Intertropical Convergence Zone during the LIA.