Landfall Activity Research Articles

Projections of future tropical cyclone landfalling activity in the East Asia region

This study reveals the possible future changes in tropical cyclone (TC) landfalling activity along the East Asian coast under different climate change scenarios based on global circulation model (GCM) simulations. We first identify those GCMs that have the “best” performance in simulating the TC activity over the western North Pacific (WNP) during the current climate (1979–2014) by examining the simulated TCs in each of the GCMs and then compare these simulated TCs with the observed TC climatological features of annual frequency, track densities and genesis locations. Based on such comparisons, we have identified five (TaiESM1, EC-Earth3, ACCESS-CM2, ACCESS-ESM1-5 and HadGEM3-GC31-LL) models among all the available GCMs. A multi-model ensemble gives a further improvement when compared with observations.Future projections from some of these models are then used to identify the frequency of TC activity over the entire WNP as well as landfalling TCs in six East Asia coastal regions under two climate change scenarios (SSP2-4.5 and SSP5-8.5) for two periods, 2041-70 and 2071-2100. A bias-correction method is also applied to the projected intensity of these landfalling TCs to estimate the landfall intensity.In general, these GCMs project a possible decrease in TC genesis frequency over the entire WNP, consistent with the results of most of the other studies. At mid-century, decreases in TC genesis frequency are projected to be around 10% for both scenarios. Towards the end of the century, the decreases will be more significant, with the percentage changes of 14.9% (SSP2-4.5) and 22.4% (SSP5-8.5). For landfalling TCs, the northern part of the East Asian coast will likely have an increase in frequency, ranging from 17 to 60% but a decrease of 14–27% in the southern part. In general, the average intensity of landfalling TCs will likely increase although the percentages are not large, ranging from 2 to 14%.

Tropical Cyclone Exposure in the North Indian Ocean

The North Indian Ocean is a region with a high coastal population and a low-lying delta, making it a high-risk region for tropical cyclone impacts. A 30-year period from 1989–2018 has been used to examine the TC landfalling exposure in the North Indian Ocean and its changes by considering 30 years of IBTrACs data, ERA5 atmospheric data, and 20 years of TRMM and DAV data. A total of 185 TCs made landfall in the NIO during the 30-year period with the majority of the TCs making landfall during the pre- and post-monsoon seasons. Rainfall associated with landfalling TCs decreased in the last 10 years of analysis (2009–2018) compared to the first 10 years of available data from 1999–2008. During the monsoon, TC activity is relatively lower compared to the post-monsoon periods, even though higher accumulated TC-associated rainfall typically occurs during the monsoon period, particularly along the eastern coastlines of the Arabian Sea and the Bay of Bengal. The TC winds impact most of the Bay of Bengal coastline, including Sri Lanka. The spatial distribution of landfalling TCs changes with the season, with most of the landfalling activity occurring during the pre- and post-monsoon periods. Interestingly, more recent TC activity has shifted to the northeast India and Bangladesh coasts, suggesting that these regions may be more vulnerable to TC impacts in the future.

Uncertainties in Atmospheric River Lifecycles by Detection Algorithms: Climatology and Variability

AbstractAtmospheric rivers (ARs) are long and narrow filaments of vapor transport that are responsible for most poleward moisture transport outside of the tropics. Many AR detection algorithms have been developed to automatically identify ARs in climate data. The diversity of these algorithms has introduced appreciable uncertainties in quantitative measures of AR properties and thereby impedes the construction of a unified and internally consistent climatology of ARs. This paper compares nine global AR detection algorithms from the perspective of AR lifecycles following the propagation of ARs from origin to termination in the MERRA2 reanalysis over the period 1980–2017. Uncertainties in AR lifecycle characteristics, including event number, lifetime, intensity, and frequency distribution are discussed. Notably, the number of AR events per year in the Northern Hemisphere can vary by a factor of 5 with different algorithms. Although all algorithms show that the maximum AR origin (termination) frequency is located over the western (eastern) portion of ocean basins, significant disagreements appear in regional distribution. Spreads are large in AR lifetime and intensity. The number of landfalling AR events produced by the algorithms can vary from 16 to 80 events per year, although the agreement improves for stronger ARs. By examining the ARs' connections with the Madden‐Julian Oscillation and El Niño Southern Oscillation, we find that the overall responses of ARs (such as changes in AR frequency, origin, and landfall activity) to climate variability are consistent among algorithms.

Variability in landfalling trends of cyclonic disturbances over North Indian Ocean region during current and pre-warming climate

Cyclonic disturbances (CDs) are one of the deadliest systems formed over ocean basins in the world. Impact of warming climate over these basins including that of North Indian Ocean (NIO) is quite prominent in terms of enhanced intensity and re-curvature of the cyclonic systems. However, the impact of warming climate on landfall activity is not yet studied for the NIO basin. Therefore, the current study is performed by dividing the climate into current and pre-warming periods based on sea surface temperature (SST) anomaly variation. The study reveals that Bangladesh, Andhra Pradesh (AP), and Tamil Nadu (TN) are more vulnerable to severe cyclones formed over Bay of Bengal (BOB) during the current warming climate. Gujrat is prone to severe cyclones and Arabian Peninsula countries are vulnerable to cyclonic storms formed over the Arabian Sea during the current warming climate as well. During CWP, Bangladesh and Arakan are more vulnerable to CD landfall in pre-monsoon season, whereas in post-monsoon months, AP, TN and Bangladesh are more prone coastal areas of BOB. Gujrat and IAA are more vulnerable coastal areas of AS irrespective of seasons considered. The enhanced genesis over southern and middle sector of BOB is mainly responsible for more landfall over AP, TN and Bangladesh. In addition, change in wind direction from NW to N-NW and increased meridional SST over BOB are found to be encouraging the landfall activity near AP and TN coasts. The W-SW and zonally distributed SST supports landfall over Gujrat. There is less impact of change in genesis location over AS landfalling CDs. Over AS near to 12° N, a well-organised wind circulation is observed enhancing the dissipation of the cyclonic systems over the basin during current warming period.

Potential impact of the Pacific Decadal Oscillation and sea surface temperature in the tropical Indian Ocean\u2013Western Pacific on the variability of typhoon landfall on the China coast

The landfall activity of typhoons (TYs) along the coast of China during July–August–September (JAS) shows significant interdecadal variation during 1965–2010. We identify three sub-periods of TY landfall activity in JAS along the China coast in this period, with more TY landfall during 1965–1978 (Period I) and 1998–2010 (Period III), and less during 1982–1995 (Period II). We find that the interdecadal variation might be related to the combined effects of Pacific Decadal Oscillation (PDO) phase changes and sea surface temperature (SST) variation in the tropical Indian Ocean and Western Pacific (IO–WP). During the negative PDO phase in Periods I and III, a cyclonic anomaly is located in the western North Pacific (WNP), inducing easterly flow in its northern part, which favors TY landfall along the eastern China coast. Warm SST anomalies over the tropical IO–WP during Period III induce an anomalous anticyclonic circulation in the WNP through both the Gill-pattern response to the warm SST in the tropical IO and the anomalous meridional circulation induced by the warm SST in the tropical WNP. As a result, the northern South China Sea and WNP (10°–20° N) are dominated by southeasterly flow, which favors TYs making landfall on both the southern and eastern China coast. With both landfalling-favorable conditions satisfied, there are significantly more TYs making landfall along the China coast during Period III than during Period I, which shows cool SST anomalies in the tropical IO–WP.

An Energetic Perspective on United States Tropical Cyclone Landfall Droughts

AbstractThe extremely active 2017 Atlantic hurricane season concluded an extended period of quiescent continental United States tropical cyclone landfall activity that began in 2006, commonly referred to as the landfall drought. We introduce an extended climatology of U.S. tropical cyclone activity based on accumulated cyclone energy (ACE) and use this data set to investigate variability and trends in landfall activity. The drought years between 2006 and 2016 recorded an average value of total annual ACE over the U.S. that was less than 60% of the 1900–2017 average. Scaling this landfall activity metric by basin‐wide activity reveals a statistically significant downward trend since 1950, with the percentage of total Atlantic ACE expended over the continental U.S. at a series minimum during the recent drought period.

Changing relationship between La Niña and tropical cyclone landfalling activity in South China (La Niña and TC landfalling activity in South China)

ABSTRACTThis study investigates the effect of El Niño–Southern Oscillation and Indo‐Pacific warm pool sea‐surface temperature (SST) on tropical cyclone (TC) landfalling activity along the South China coast and develops a scheme for predicting this activity. In general, landfalling activity tends to be suppressed in El Niño years but a large uncertainty is found for La Niña years. Landfalling activity is generally enhanced in La Niña years before 1997 but suppressed in those after 1997, which may be related to the changes in TC frequency and track pattern over the western North Pacific (WNP) as well as the northward shift in genesis locations. The Indo‐Pacific warm pool SST is found to be related to the TC activity over the WNP and an SST index, defined as the average SST anomalies over the North Indian Ocean and the sea near the Philippines, is used to represent this anomaly. A significant warming of the Indo‐Pacific warm pool is found in the recent decade. The temperature change of this warm pool appears to modulate the TC activity over the WNP and TC landfalling activity in South China in a La Niña year, with an enhancement (a suppression) of TC activity if a cooling (warming) is found. This difference is related to the changes in the strength of monsoon trough, vertical wind shear and steering flow pattern. Based on these results, a schematic prediction scheme of landfalling activity in South China is proposed. Landfalling activity is likely to be normal or below normal if an El Niño event is expected to develop during the TC season. If a La Niña event is expected, and the predicted state of the Indo‐Pacific warm pool (obtained using the persistence forecast) shows a warming (cooling), landfalling activity is likely to be normal or below normal (above normal).

Impacts of the Pacific Meridional Mode on Landfalling North Atlantic tropical cyclones

This study examines the impacts of the Pacific Meridional Mode (PMM) on North Atlantic tropical cyclones (TCs) making landfall along the coastal US, Caribbean Islands and Mexico, and provides insights on the underlying physical mechanisms using observations and model simulations. There is a statistically significant time-lagged association between spring PMM and the August–October US and Caribbean landfalling TCs. Specifically, the positive (negative) spring PMM events tend to be followed by fewer (more) TCs affecting the coastal US (especially over the Gulf of Mexico and Florida) and the Caribbean Islands. This lagged association is mainly caused by the lagged impacts of PMM on the El Nino Southern Oscillation (ENSO), and the subsequent impacts of ENSO on TC frequency and landfalls. Positive (negative) PMM events are largely followed by El Nino (La Nina) events, which lead to less (more) TC geneses close to the US coast (i.e., the Gulf of Mexico and the Caribbean Sea); this also leads to easterly (westerly) steering flow in the vicinity of the US and Caribbean coast, which is unfavorable (favorable) to TC landfall across the Gulf of Mexico, Florida and Caribbean Islands. Perturbation simulations with the state-of-the-art Geophysical Fluid Dynamics Laboratory Forecast-oriented Low Ocean Resolution Version of CM2.5 (FLOR) support the linkage between PMM and TC landfall activity. The time-lagged impacts of spring PMM on TC landfalling activity results in a new predictor to forecast seasonal TC landfall activity along the US (especially over the Gulf of Mexico and Florida) and Caribbean coastal regions.

Statistical–Dynamical Seasonal Forecast of North Atlantic and U.S. Landfalling Tropical Cyclones Using the High-Resolution GFDL FLOR Coupled Model

Abstract Retrospective seasonal forecasts of North Atlantic tropical cyclone (TC) activity over the period 1980–2014 are conducted using a GFDL high-resolution coupled climate model [Forecast-Oriented Low Ocean Resolution (FLOR)]. The focus is on basin-total TC and U.S. landfall frequency. The correlations between observed and model predicted basin-total TC counts range from 0.4 to 0.6 depending on the month of the initial forecast. The correlation values for U.S. landfalling activity based on individual TCs tracked from the model are smaller and between 0.1 and 0.4. Given the limited skill from the model, statistical methods are used to complement the dynamical seasonal TC prediction from the FLOR model. Observed and predicted TC tracks were classified into four groups using fuzzy c-mean clustering to evaluate the model’s predictability in observed classification of TC tracks. Analyses revealed that the FLOR model has the highest skill in predicting TC frequency for the cluster of TCs that tracks through the Caribbean and the Gulf of Mexico. New hybrid models are developed to improve the prediction of observed basin-total TC and landfall TC frequencies. These models use large-scale climate predictors from the FLOR model as predictors for generalized linear models. The hybrid models show considerable improvements in the skill in predicting the basin-total TC frequencies relative to the dynamical model. The new hybrid model shows correlation coefficients as high as 0.75 for basinwide TC counts from the first two lead months and retains values around 0.50 even at the 6-month lead forecast. The hybrid model also shows comparable or higher skill in forecasting U.S. landfalling TCs relative to the dynamical predictions. The correlation coefficient is about 0.5 for the 2–5-month lead times.

Tropical Cyclone Impacts on Coastal Regions: the Case of the Yucatán and the Baja California Peninsulas, Mexico

Tropical cyclones (TCs) are large-scale natural disturbances that generate strong winds and heavy rainfall, impacting coastal and inland environments. TCs also influence biogeochemical and hydrological cycles controlling aquatic primary productivity in tropical and subtropical coastal ecosystems. We assessed TC landfall activity and identified sites along the Mexican east and west coasts with high frequency in the period 1970–2010 and evaluated TCs with significant precipitation. Changes in chlorophyll-a (Chl-a) concentrations before and after storm impacts were estimated using remotely sensed ocean color. There were 1,065 named TCs with a wide diversity in tracks. Three states with the highest number of landfalls were identified: Baja California Sur and Sinaloa on the west coast and Quintana Roo on the east coast. While a relative increase in Chl-a values following TC landfalls in the Baja California and Yucatan Peninsula regions appeared to be strongly linked to TC strength, the intensity of precipitation, the spatial scales of the two peninsulas, and the relative movement of TCs appeared to have contributed to Chl-a variability. Satellite estimates of Chl-a in the nearshore coastal waters following TC passage were likely enhanced by coastal morphology and water discharge along with constituents such as suspended particulate, colored dissolved organic matter and nutrients from rivers, tributaries, and groundwater.

Different impacts of various El Niño events on the Indian Ocean Dipole

Our early work (Wang and Wang in J Clim 26:1322-1338, 2013) separates El Nio Modoki events into El Nio Modoki I and II because they show different impacts on rainfall in southern China and typhoon landfall activity. The warm SST anomalies originate in the equatorial central Pacific and subtropical northeastern Pacific for El Nio Modoki I and II, respectively. El Nio Modoki I features a symmetric SST anomaly distribution about the equator with the maximum warming in the equatorial central Pacific, whereas El Nio Modoki II shows an asymmetric distribution with the warm SST anomalies extending from the northeastern Pacific to the equatorial central Pacific. The present paper investigates the influence of the various groups of El Nio events on the Indian Ocean Dipole (IOD). Similar to canonical El Nio, El Nio Modoki I is associated with a weakening of the Walker circulation in the Indo-Pacific region which decreases precipitation in the eastern tropical Indian Ocean and maritime continent and thus results in the surface easterly wind anomalies off Java-Sumatra. Under the Bjerknes feedback, the easterly wind anomalies induce cold SST anomalies off Java- Sumatra, and thus a positive IOD tends to occur in the Indian Ocean during canonical El Nio and El Nio Modoki I. However, El Nio Modoki II has an opposite impact on the Walker circulation, resulting in more precipitation and surface westerly wind anomalies off Java-Sumatra. Thus, El Nio Modoki II is favorable for the onset and development of a negative IOD on the frame of the Bjerknes feedback.

Impact of the Atlantic warm pool on United States landfalling hurricanes

[1] The 2010 Atlantic hurricane season was extremely active, but no hurricanes made landfall in the United States, raising a question of what dictated the hurricane track. Here we use observations from 1970–2010 (also extending back to 1950) and numerical model experiments to show that the Atlantic warm pool (AWP) – a large body of warm water comprised of the Gulf of Mexico, the Caribbean Sea and the western tropical North Atlantic – plays an important role in the hurricane track. An eastward expansion of the AWP shifts the hurricane genesis location eastward, decreasing the possibility for a hurricane to make landfall. A large AWP also induces barotropic stationary wave patterns that weaken the North Atlantic subtropical high and produce the eastward steering flow anomalies along the eastern seaboard of the United States. Due to these two mechanisms, hurricanes are steered toward the northeast without making landfall in the United States. Although the La Nina event in the Pacific may be associated with the increased number of Atlantic hurricanes, its relationship with landfalling activity has been offset in 2010 by the effect of the extremely large AWP.

Tropical cyclones in China: County-based analysis of landfalls and economic losses in Fujian Province

Most of China’s coastline is economically developing, densely populated, and frequently hit by landfalling Tropical Cyclones (TCs). Economic losses below province level have not been systematically analyzed due to lack of data. The objective of this paper is to conduct a TC loss assessment on county level in Fujian Province, coastal SE China, and to break down economic losses from province-scale to smaller administrative units. A unique loss database established by the China Meteorological Administration (CMA) and National Climate Center is used, and four entries at county-level are derived: location of losses due to TC, total economic losses per TC, start time of TC, and end time of TC. Tracks and intensities of TCs from 1949–2008 are derived from the CMA and Shanghai Typhoon Center annual typhoon yearbooks. Physical and economic data are overlaid in a Geographical information System. The landfall spots of TCs on China’s mainland coastline from 1949–2008 are determined by generating segments of 1° length. The result shows that Guangdong Province (South China) and Fujian Province (South-East China) host distinct hot spots where TCs make frequent landfall. All TCs making landfall in Central-North Fujian originated from the West North Pacific and none from the South China Sea. Direct economic losses in 25 counties along Fujian’s coastline due to TCs from 1984–2007 are analyzed and corrected with the Consumer Price Index. Some counties report losses frequently at low magnitude but seldom at high magnitude. Others like urban Fuzhou experience losses above 10 million CNY per TC, the most costly one 70 times higher. Other rural counties might experience economic losses far below 10 million CNY when being hit. Landfalling TCs in average cause economic losses of minimum 10 million CNY in 21 of 25 counties. In roughly one third of the counties, economic losses account for more than 30 million CNY when a TC has impact. The average economic losses per TC are 0.2–0.5% of the counties’ GDP (South and North of Fujian’s coastline) and even more than 0.5% of the GDP in North-East Fujian. The economic impacts of TCs are higher along the southern and northern coastline of Fujian Province where TC landfall activity is higher, but higher economic losses are triggered by higher GDP in these counties. The most costly TCs in Fujian had intensities of Severe Tropical Storm or Typhoon and occurred mostly in the 2000’s after making landfall in July.

On the Relationship between North Atlantic Sea Surface Temperatures and U.S. Hurricane Landfall Risk

AbstractIn the recent literature, considerable attention has been paid to the relationship between climate signals and tropical cyclone activity. Much of the research has focused on Atlantic Ocean basin activity while less attention has been given to landfall frequency and the geographic distribution of risk to life and property. However, recent active seasons like 2004 and 2005 and the resulting damage and economic loss have generated significant interest in the relationship between climate and landfall risk. This study focuses on sea surface temperatures (SST) and examines modulation of landfall activity occurring in anomalously warm-SST seasons. The objective of the study is to evaluate the effect of warmer ocean conditions on U.S. landfall risk. The study is broken into two parts–—statistical and physical. The statistical analysis categorizes historical hurricane seasons as either warm or cool and then estimates shifts in landfall frequency under these two climate modes. The analysis is carried out for overall U.S. landfall risk and then for logical subregions along the U.S. coastline. The climatological behavior for warm-SST conditions is developed across the intensity spectrum, from weak tropical storms to major hurricanes, using wind speed as an intensity measure. The analysis suggests that landfall risk is sensitive to SST conditions but that sensitivity varies by region and intensity. The uncertainty associated with these estimates is discussed. The physical analysis is carried out to understand better why landfall risk is not affected uniformly along the U.S. coastline and to reinforce the reasonability of the statistical results. The study involves a detailed examination of the complete life cycle of historical storms. Results indicate that storms making landfall along the East Coast have different genesis and intensification characteristics relative to storms making landfall along the Gulf Coast. As SSTs warm, the genesis pattern shifts, greatly influencing regional landfall risk. Further, hurricane landfalls may react not only to warm-SST conditions, but also to the effect of ocean temperature anomalies on the atmosphere’s general circulation. There are implications that complex feedback mechanisms play a role in modulating the probability of landfall, especially from certain parts of the Atlantic basin. Such physical theories provide added confidence in statistical estimates of elevated risk for certain breeds of tropical cyclones.

Atlantic basin, U.S. and Caribbean landfall activity rates over the 2006–2010 period: an insurance industry perspective

Atlantic basin, U.S. and Caribbean landfall activity rates over the 2006–2010 period: an insurance industry perspective

Effect of ENSO on Queensland seasonal landfalling tropical cyclone activity

AbstractA statistical model for predicting seasonal tropical cyclone landfalls in Queensland, Australia using an index of the El Niño‐Southern Oscillation (ENSO) is presented. The approach uses a generalised linear model (GLM) to relate seasonal counts to the Southern Oscillation Index (SOI). A Bayesian methodology is employed to estimate parameters of the model. The available tropical cyclone record is first separated into historical (1910/1911–1959/1960) and instrumental (1960/1961–2004/2005) eras. Historical counts, which are considered to be less reliable observational sources, are used to specify informative prior distributions when fitting the GLM to instrumental counts with the Bayesian approach. The inclusion of historical information is found to lead to increased certainty in parameter estimates when compared to a model where historical counts are excluded and a non‐informative prior model used. Predictive distributions are given, which allow inferences on seasonal landfall activity, given pre‐seasonal values of the SOI. A cross‐validation procedure shows that the model incorporating historical information outperforms, in terms of mean‐squared prediction error, both the non‐informative prior model and a model without the SOI‐predictor (climatology). A trend analysis highlights possible decadal variability in the relationship between ENSO and seasonal tropical cyclone activity. Copyright © 2007 Royal Meteorological Society

Atlantic basin, U.S. and Caribbean landfall activity rates over the 2006–2010 period: an insurance industry perspective

Atlantic hurricane activity has been particularly high since 1995, with nine seasons recording more hurricanes than the long-term average. The recognition that current activity is not the same as the long-term historical average means that, for the purpose of catastrophe risk assessment, we need to be explicit as to the time period over which expected activity is evaluated.We have chosen to explore activities over a 5-yr forward looking time window, which bounds the range of business applications for which catastrophe loss models are employed. This time horizon is also shorter than the pattern of past multidecadal periods of high and low activity.The methodology used to assess activity rates for the next 5 yr contains a blend of statistical analyses and an expert elicitation. A panel of experts was convened to discuss expected levels of activity for the next 5 yr across the Atlantic, along the U.S. and Caribbean coasts. The results indicate hurricane activities along the U.S. coast are expected to be between 20 and 35% higher than the long-term average, depending on storm intensity. The implementation of these findings has included work to determine how increases are distributed by track type and by region, and the impacts on expected losses.

Comparison of Hindcasts Anticipating the 2004 Florida Hurricane Season

Abstract Advances in hurricane climate science allow forecasts of seasonal landfall activity to be made. The authors begin with a review of the forecast methods available in the literature. They then reformulate the methods using a Bayesian probabilistic approach. This allows a direct comparison to be made while focusing on a single hindcast of the 2004 season over Florida. The models, including climatology, are estimated using Gibbs sampling. Diagnostic checks verify convergence and efficient mixing of the samples from each of the models. A below average sea level pressure gradient over the eastern North Atlantic Ocean during May and June in combination with an above average tropospheric-averaged wind index associated, in part, with a strengthening of the Bermuda high pressure during July resulted in an above average probability of at least one Florida hurricane. The relatively high hindcast probabilities for 2004 were in marked contrast to the most recent 50-yr empirical probabilities for Florida, but fell short in anticipating the unprecedented level of activity that ensued. Similar results are obtained from hindcasts of total U.S. hurricane activity for 2004.