Tropical Cyclone Track Density Research Articles

A Machine Learning Bias Correction on Large‐Scale Environment of High‐Impact Weather Systems in E3SM Atmosphere Model

AbstractLarge‐scale dynamical and thermodynamical processes are common environmental drivers of high‐impact weather systems causing extreme weather events. However, such large‐scale environmental conditions often display systematic biases in climate simulations, posing challenges to evaluating high‐impact weather systems and extreme weather events. In this paper, a machine learning (ML) approach was employed to bias correct the large‐scale wind, temperature, and humidity simulated by the atmospheric component of the Energy Exascale Earth System Model (E3SM) at ∼1° resolution. The usefulness of the ML approach for extreme weather analysis was demonstrated with a focus on three high‐impact weather systems, including tropical cyclones (TCs), extratropical cyclones (ETCs), and atmospheric rivers (ARs). We show that the ML model can effectively reduce climate bias in large‐scale wind, temperature, and humidity while preserving their responses to imposed climate change perturbations. The bias correction is found to directly improve water vapor transport associated with ARs, and representations of thermodynamical flows associated with ETCs. When the bias‐corrected large‐scale winds are used to drive a synthetic TC track forecast model over the Atlantic basin, the resulting TC track density agrees better with that of the TC track model driven by observed winds. In addition, the ML model insignificantly interferes with the mean climate change signals of large‐scale storm environments as well as the occurrence and intensity of three weather systems. This study suggests that the proposed ML approach can be used to improve the downscaling of extreme weather events by providing more realistic large‐scale storm environments simulated by low‐resolution climate models.

A new and efficient method for tropical cyclone detection and tracking in gridded datasets

Most of existing algorithms for detecting tropical cyclones (TCs) in global climate model employed multiple detectors, and screened the field grid by grid by thresholding, while a quantitative assessment of the performance of these algorithms has been infrequent. A new method based on mathematical morphology for detecting and tracking TC in gridded reanalysis data is proposed and evaluated. The method begins by transforming the field of lower-tropospheric (850 hPa) relative vorticity from the reanalysis data into a binary image using a defined critical vorticity threshold. The images are then processed by connected component labeling and erosion operations until inner cores emerge as the TC seeds. Simple rules for connecting the seeds to form TC tracks are proposed. Twenty years of ERA5 data and the China Meteorological Administration best track data (CMA) in 2002–2021 are used to develop and evaluate the method for the Western North Pacific basin (WNP). The detected TC events are examined track-by-track with the observed ones. The performance of the method is further evaluated in terms of the statistics of TC occurrence, track density, landfall location, and translational speed. It is demonstrated that the proposed method can reproduce the TC tracks for both over ocean and after landfall with good accuracy and efficiency. The source of erroneous tracking and limitation of the proposed method are discussed. Given its satisfactory performance in tracking TCs in the WNP basin, it is promising to be applied to the study of TC changes in a warming climate.

Unraveling the strong covariability of tropical cyclone activity between the Bay of Bengal and the South China Sea

Herein, we report a strong in-phase covariability of tropical cyclone (TC) activity between the Bay of Bengal (BOB) and the South China Sea (SCS) during October–December of 1979–2019, and which is also the dominant mode of BOB–SCS TC activity, accounting for 35% of the total variances in TC track density. This inter-basin TC covariance is closely linked to the anomalies of tropical sea surface temperature, appearing as the intrinsic Indo-Pacific Tripole mode, which significantly affects the atmospheric circulations overlying the BOB–SCS. Interestingly, this mechanism works via modulating the local TC genesis frequency in the BOB–SCS. However, in terms of the migrated TCs among them, the Indo-Pacific Tripole mainly regulates their genesis location but not their frequency. More importantly, such inter-basin TC covariability still exists significantly even when the TC track data migrating from the SCS into the BOB are excluded. After all, only 19 TCs during the 41 years (1979–2019) are observed to migrate from the SCS to the BOB, which can only contribute slightly to increasing the covariability of BOB–SCS TC-track activity, but do not play a dominant role. Further, the numerical simulations suggest that although both the Indian and Pacific Oceans contribute to the atmospheric anomalies that affect the BOB–SCS TC activity, the Pacific-effect is twice as important.

Modulation of Tropical Cyclone Tracks and Rainfall by the North Atlantic Oscillation

AbstractUnderstanding and quantifying the large‐scale environmental control of spatio‐temporal tropical cyclone (TC) variability beyond a few weeks remains a challenge with significant implications for societal impacts. This study focuses on the relationship between the North Atlantic Oscillation (NAO) and year‐to‐year changes in TC activity and rainfall using observational data and reanalysis products. We use Poisson regression models to show that low‐frequency NAO (LF‐NAO) variability is associated with a distinct pattern of TC activity, which extends across the western North Atlantic, the Caribbean Basin, and the Gulf of Mexico. The negative LF‐NAO phase is characterized by enhanced TC activity: an interquartile range decrease in the NAO corresponds to a 30%–40% increase in TC track density. While the NAO is known to affect the weather regimes of the mid‐latitudes, we show that its low‐frequency component has a strong correlation to the large‐scale environment across the Main Development Region of TCs. The negative LF‐NAO phase is associated with two favorable environmental conditions for TCs: significantly higher sea‐surface temperature and weaker deep‐tropospheric wind shear. The LF‐NAO relationship to TC activity is strongest during El Niño Southern Oscillation positive or neutral conditions and during the negative Atlantic Multidecadal Oscillation phase, and it can also be detected in the basin‐scale variations of TC rainfall. By developing annual TC rainfall composites from satellite data and reanalysis products, we show that TC rainfall is strongly enhanced in the Caribbean and in the Gulf of Mexico during the negative LF‐NAO phase.

Influence of Dynamic and Thermal Effects of Asian Topography on Tropical Cyclone Activity as Simulated in a Global Climate Model

Asian topography plays a significant role in regional and global weather and climate change. Based on the dataset of climate system model named CAS FGOALS-f3 participated in Global monsoons Model Inter-comparison (GMMIP), the MIP endorsement of Coupled Model Intercomparison Project Phase 6 (CMIP6), the role of Asian topography to the formation and movement of tropical cyclones (TCs) are discussed in this study. This study provides the first comparative analysis of the dynamic and thermal effects of Asian topography on the regional and global activity of TCs. The results indicate that the Asian topography promotes the generation and development of TCs, especially in the Northwest Pacific (WNP). The contribution of the Asian topography to the number of TCs reached about 50% in WNP. It is worth noting that there are still positive biases of TC track density in the experiment named “AMIP-NS,” which means the thermal effect of Asian topography is also essential for TC formation and development in WNP, which has not received much attention before. Besides, the possible reasons for the modulation of TC activity are given from two aspects: (1) The existence of Asian topography has changed the large-scale factors related to TC activities such as warm core, sea-level pressure, genesis potential index (GPI), which are beneficial to the generation and movement of TC. (2) Asian topography promotes the spread of Madden–Julian oscillation (MJO), which is also beneficial to the generation and movement of TC. It is worthwhile to investigate further the mechanisms by which Asian topography affects the activity of TCs.

Skillful Seasonal Prediction of Typhoon Track Density Using Deep Learning

Tropical cyclones (TCs) seriously threaten the safety of human life and property especially when approaching a coast or making landfall. Robust, long-lead predictions are valuable for managing policy responses. However, despite decades of efforts, seasonal prediction of TCs remains a challenge. Here, we introduce a deep-learning prediction model to make skillful seasonal prediction of TC track density in the Western North Pacific (WNP) during the typhoon season, with a lead time of up to four months. To overcome the limited availability of observational data, we use TC tracks from CMIP5 and CMIP6 climate models as the training data, followed by a transfer-learning method to train a fully convolutional neural network named SeaUnet. Through the deep-learning process (i.e., heat map analysis), SeaUnet identifies physically based precursors. We show that SeaUnet has a good performance for typhoon distribution, outperforming state-of-the-art dynamic systems. The success of SeaUnet indicates its potential for operational use.

Simulation and Projection of Tropical Cyclone Activities over the Western North Pacific by CMIP6 HighResMIP

Abstract This study assesses the relative impacts of model resolutions, tropical cyclone (TC) trackers, and ocean coupling on simulating TC climatology over the western North Pacific (WNP) based on six Coupled Model Intercomparison Project phase 6 (CMIP6) High-Resolution Model Intercomparison Project (HighResMIP) models from 1979 to 2014. The HighResMIP multimodel ensemble (MME) analysis shows that the high resolution has a higher Taylor skill score II (S2) in both temporal and spatial patterns of TC genesis frequency and accumulated cyclone energy (ACE) than the low resolution. In contrast, the TempestExtremes tracker (coupled run) results in a higher S2 in temporal patterns but a lower S2 in spatial patterns than the TRACK tracker (uncoupled run). Among the three factors, increased resolution leads to the greatest improvement in S2 in both temporal and spatial patterns. Furthermore, this study investigates the projections of future TC activity over the WNP by HighResMIP under the SSP5–8.5 scenario. Overall, HighResMIP MMEs project a decrease in the genesis frequency, track density, and ACE of all TCs, with the high-resolution, TRACK tracker, and uncoupled run showing greater magnitude. The high-resolution MMEs, using both trackers, project an increase in the genesis frequency and ACE of intense TCs in the coupled run. Moreover, TC track density and ACE show a larger poleward migration in the coupled run than in the uncoupled run, consistent with the significant surface warming in the northern WNP.

Impacts of tropical cyclones on summertime short-duration precipitation extremes over the middle-lower reaches of the Yangtze River valley

This study investigated variations in summertime short-duration precipitation extremes over the middle-lower reaches of the Yangtze River valley (MLYRV) and the possible impacts of tropical cyclones (TC) on these changes over the 1961–2016 period. Three short-duration precipitation types, including all events and the events in the 75th and 95th percentiles, are defined. At the 75th percentile, both the amount and number of TC-induced extreme short-duration rainfall events exhibit slightly declining trends, and the trends are not pronounced for the 95th-percentile cases. The number and amount of TC-induced 95th-percentile events are approximately one order of magnitude larger than those of the 75th-percentile cases, indicating that TCs play a more significant role on the upper tail of the rainfall distribution over the MLYRV in summer than on the rest of the precipitation distribution. A large number of the defined non-TC precipitation events are mainly distributed over the central-south MLYRV and southeastern regions. The spatial patterns of TC-induced rainfall resemble the contributions of TC-induced precipitation events to the total summer rainfall, with large values located in southeastern regions of the MLYRV. The spatial distribution of 95th-percentile events is principally attributed to the frequency of TC activities and to the TC tracks. Most of the TCs that trigger 95th-percentile events make landfall over the southeast MLYRV, and the corresponding large frequency of TC tracks is mainly situated over the ocean to the east of Taiwan. Both environmental factors and atmospheric circulations modulate the variations in extreme short-duration rainfall events. In particular, equatorward displacement of the western Pacific subtropical high impacts TC track density, resulting in more occurrences of precipitation extremes in 95th-percentile events over the MLYRV.

PDO Modulation on the Relationship between ENSO and Typhoon Tracks

Abstract This study explores the role of the Pacific decadal oscillation (PDO) in modulating the relationship between El Niño–Southern Oscillation (ENSO) and typhoon tracks. Tropical cyclone (TC) trajectories in the western North Pacific (WNP) in 1950–2017 are clustered into seven clusters, including three recurved trajectories and four straight-moving tracks. These clusters are distinguished well by number of TCs, intensity, lifetime, genesis position/month, landing, and track. The sea surface temperature (SST) anomaly in the composite analysis and accumulated cyclone energy (ACE) of each cluster demonstrate that there are four clusters dominated by ENSO. The associated ENSO effects on these clusters are manifested by steering flow and vertical wind shear (VWS) in the composite differences between El Niño and La Niña years. However, such ENSO effects on TC quantity, genesis location, and track of these corresponding clusters are significantly enhanced during the PDO positive phases only for two clusters that are formed in the southeastern part of the WNP and undergo a long lifetime and track, because the PDO explains little local environmental variance where the other two clusters are located in the northern part of the WNP. This conclusion is also supported by TC track density analysis. The two leading modes of empirical orthogonal functions (EOF) analysis of TC track density are significantly correlated with ENSO. The enhancement of ENSO effects during the PDO positive phase exhibits by the second mode through local SST, VWS, and steering flow. Significance Statement Accurate prediction of tropical cyclone (TC) activity can help preparedness and therefore reduce the losses of life and property. Long-term track prediction relies on our understanding how TC tracks are associated with interannual and longer climate variability. This study uses historical data of 1950–2017 in the western North Pacific and reveals that only for two of four track clusters that are affected by El Niño–Southern Oscillation (ENSO), the associated ENSO effects are enhanced during the Pacific decadal oscillation positive phases because the oscillation has significant influence on vertical wind shear and steering flow where these two clusters are located. The findings enrich the mechanisms of TC track variabilities and will help improve long-term prediction of TC tracks.

Opposite Changes in Tropical Cyclone Rain Rate During the Recent El Niño and La Niña Years

AbstractIn this paper, we investigate whether the relationship between the El Niño‐Southern Oscillation and tropical cyclone (TC) rain rate over the western North Pacific (WNP) changes between the global warming slowdown (2001–2012) and resumption (2013–2020) periods. Using high‐resolution satellite rainfall data, we show that the average TC rain rate increases by 9% but decreases by 14% during the recent El Niño and La Niña years (since 2013), respectively. During the El Niño years, the increase is related to higher TC track density at lower latitudes, where more water vapor and stronger convergence are present. On the other hand, the decrease in TC rain rate during the recent La Niña years is mainly related to an increase in track density at higher latitudes and a decrease in TC intensity. These changes in TC track density and intensity are both associated with the strengthening of the subtropical high since 2013.

Resolution dependence of tropical cyclones simulated by a spectral cumulus parameterization

The resolution dependence of tropical cyclones (TCs) simulated by a spectral cumulus parameterization (spectral scheme) was investigated using an atmospheric general circulation model with three ensemble members and atmosphere-only experiments. The focus of the analysis was the cause of resolution dependence of TCs which has not been clarified in previous studies. The results showed that underestimation of the TC track density and TC intensity was improved by an increase in the horizontal resolution as reported in previous studies. A mean state analysis revealed that the mean states were qualitatively similar regardless of model resolution although TC statistics were different; this implies that local differences in the atmospheric condition may have a strong impact on the TC statistics. Analyses of the horizontal structure indicated that the local TC structure better approximated observations as the resolution increased, but this was not due to enhanced atmospheric instability because the TC center location coincided with the highly unstable region only in the early stage of TC development. Influential differences for TC statistics were found in the vertical TC structure. A temperature anomaly with a large radial gradient induced by diabatic heating within the eyewall of a TC first impacted the vertical–radial circulation and then caused strong boundary layer inflow toward the eyewall. If a low resolution was adopted, the radial gradient of the temperature anomaly with strong low-level inflow was not well simulated, resulting in a weaker TC intensity and lower TC genesis frequency. Some TC property changes associated with resolution in the current spectral scheme were found to be similar to those of existing convection scheme, but there were some improvements that were specific to this spectral scheme. The cause of the improvements introduced by the present spectral scheme is briefly discussed.

How Does Pacific Decadal Oscillation Affect Tropical Cyclone Activity Over Far East Asia?

AbstractWe investigated the relationship between tropical cyclones (TCs) and the Pacific Decadal Oscillation (PDO) over the western North Pacific (WNP) during 1982–2018, focusing on an area surrounding the Korean Peninsula and Japan. The frequency of TCs passing through this area (TCm) in the negative PDO phase was approximately 50% higher than that in the positive phase in September. Higher TC track density was observed around the Korean Peninsula and Japan in the negative PDO phase because the large‐scale environments were favorable for TC activity. However, TCm and PDO were not related in August because the location of WNP subtropical high was not significantly different. In addition, large‐scale environments, which were associated with TC activity, provided more favorable conditions in September than in August.

Sensitivity of tropical cyclones to convective parameterization schemes in RegCM4

This study investigates the sensitivity of simulated tropical cyclones (TC) affecting the Philippines to convective parameterization schemes (CPS) in the Regional Climate Model Version 4 (RegCM4). Five ERA-Interim driven RegCM4 simulations at 25-km horizontal resolution were conducted utilizing the CPS of Grell with Arakawa–Schubert closure (GR), Emanuel (EM), Kain–Fritsch (KF), Tiedtke (TE), and a combined Grell scheme over land and Emanuel over the ocean (GR-EM). Comparisons made between the observed and RegCM4-simulated TCs covering a 30-year period (1981–2010) indicate that the EM scheme yields an annual-mean TC frequency that is closest to observations. The GR-EM scheme, on the other hand, closely reproduces the observed seasonal patterns of TC tracks, spatial patterns of TC track density and TC-associated rainfall, and TC lifespan. The KF scheme is the only CPS that was able to simulate intense TCs (maximum wind speed > 40 m s–1) within the domain. In contrast, both GR and TE schemes largely underestimated the TC frequency, and were only able to simulate weak TCs. Such underestimation in the TC frequency and intensity in the GR and TE simulations can be attributed to the dry mid-tropospheric environment and the absence of a large area with positive low-level relative vorticity over the Pacific Ocean inhibiting TC formation and further development over the area. These findings would be helpful in selecting the more appropriate CPS for TC-related model simulations over the Philippines and in further model improvements, given the climate modeling imperfections and associated biases.

Influence of a spectral cumulus parametrization on simulating global tropical cyclone activity in an AGCM

AbstractThe influence of a new spectral cumulus parametrization (the spectral scheme) on simulating global tropical cyclone (TC) activity in an Atmospheric General Circulation Model (AGCM) is investigated. Experiments are performed using AFES (AGCM for the Earth Simulator) and two different convection schemes – the original convection scheme of the AGCM (the Emanuel scheme) and the spectral scheme. The result shows that the both schemes can capture qualitative features of global TC activity in terms of climatology, variability, and intensity. However, the spectral scheme simulates TC genesis and track density better than the original convection scheme by improving the cold bias in the upper troposphere. The spectral scheme also provides better results for TC response to interannual variability (i.e., El Niño Southern Oscillation, ENSO) by suppressing excessive convection response to ENSO. The spectral scheme is capable of simulating the variability of TC genesis related to the Madden–Julian Oscillation (MJO) much better than the original convection scheme. Consequently, the spectral scheme can outperform the original convection scheme in simulating global TC activity from various perspectives, and thus the scheme is expected to be useful for TC prediction and future projections.

Revisiting the interannual impact of the Pacific Meridional Mode on tropical cyclone genesis frequency in the Western North Pacific

Several studies have discussed the interannual influences of the North Pacific Meridional Mode (PMM) on the tropical cyclone (TC) in the western North Pacific (WNP). However, most of them either mixed the contributions of the PMM and Pacific decadal modes or failed to separate the PMM and El Nino-Southern Oscillation (ENSO) impacts. Here, we systematically revisited the year-to-year relationship between the PMM and WNP TC activity, including TC genesis frequency (TCGF) and TC track density (TCTD), by removing decadal variability. The results show that positive (negative) PMM events can induce anomalous basin-uniform cyclonic (anticyclonic) circulation and lead to a significant increase (decrease) in TCGF and TCTD over the WNP. The relationship between TCGF and the PMM is modulated by the ENSO events. When the positive PMM events are synchronized with the El Nino phase, they can enhance southeastern quadrant TC genesis over the WNP and increase TCTD in the whole WNP. However, when the positive PMM events are in phase with La Nina events, it shows an insignificant impact on WNP TCs due to the reverse influence of PMM and ENSO. This study emphasizes the important influence of the PMM on WNP TC activity on interannual time scale, especially during neutral ENSO years.

Linkages Between Tropical Cyclones and Extreme Precipitation over China and the Role of ENSO

This research investigated the linkages between tropical cyclones (TCs) and extreme precipitation, and their associations with El Niño-Southern Oscillation (ENSO) over China. The contribution of TC-induced to total extreme precipitation events along the southeast coast of China was higher than 50%, and the values gradually decreased as TCs moved inland. However, the precipitation extremes (magnitude and frequency) related to TCs did not show statistically significant changes over the most recent 57 years. The impacts of TCs on precipitation extremes are evidently modulated by the ENSO phases. We found less extreme precipitation linked with TCs in southeastern China during El Niño phase, because of the fewer TC tracks over this region and less TC genesis in the western North Pacific (WNP). The small TC track density over southeastern China is due to the prevalent westerly steering flow and abnormal integrated vapor transport from northern to southern China during El Niño years. Additionally, warmer sea surface temperature, more vigorous westerlies, larger vorticity in 250 hPa, and higher divergence in 850 hPa in an El Niño phase jointly displaced the mean genesis of the WNP TCs eastward and this led to fewer TCs passing through southeastern China.

North Indian Ocean tropical cyclone activity inCMIP5experiments: Future projections using a model‐independent detection and tracking scheme

AbstractThe sensitivity of tropical cyclone (TC) projection results to different models and the detection and tracking scheme used is well established. In this study, future climate projections of TC activity in the North Indian Ocean (NIO) are assessed with a model‐ and basin‐independent detection and tracking scheme. The scheme is applied to selected models from the coupled model intercomparison project phase 5 (CMIP5) experiments forced under the historical and representative concentration pathway 8.5 (RCP8.5) conditions. Most models underestimated the frequency of early season (April–June) TCs and contained genesis biases equatorward of ~7.5°N in comparison to the historical records. TC tracks detected in reanalysis and model data were input to a clustering algorithm simultaneously, with two clusters in the Arabian Sea and two in the Bay of Bengal (k= 4). Projection results indicated a slight decrease of overall TC genesis frequency in the NIO, with an increase of TC genesis frequency in the Arabian Sea (30–64%) and a decrease in the Bay of Bengal (22–43%), consistent between clusters in each of these sub‐regions. These changes were largely due to changes in the pre‐monsoon season (April–June) where Bay of Bengal TCs significantly decreased, consistent with changes in vertical ascent. Northern Arabian Sea TCs significantly increased during the pre‐monsoon season, consistent with changes in vertical wind shear and relative humidity. There was a projected increase of TC frequency in the post‐monsoon season (October–December), consistent with changes in relative humidity and vertical ascent, although not all clusters followed this trend; noting a different response in the southern Bay of Bengal. In turn, these projections caused changes to the climate averaged TC track density, including a decrease (up to 2 TCs per decade) affecting the eastern coast of India and a small increase (up to 0.5 TCs per decade) affecting eastern Africa, Oman and Yemen.

Increasing Destructive Potential of Landfalling Tropical Cyclones over China

AbstractThis study investigates the trend in destructive potential of landfalling tropical cyclones (TCs) in terms of power dissipation index (PDI) over mainland China in the period of 1980–2018. Results show that both the accumulated PDI and averaged PDI after landfall show significant increasing trends. The increasing trends are found to be contributed primarily by the increasing mean duration of TCs over land and the increasing TC intensity at landfall. Further analyses indicate that the increase in landfalling TC intensity prior to and at landfall, the decrease in intensity weakening rate after landfall, and the northward shift of landfalling TC track density all contribute to the longer duration of TCs after landfall. Moreover, the conducive large-scale conditions, such as the increases in coastal sea surface temperature and land surface temperature and soil moisture, the decrease in low-level vertical wind shear, and the increase in upper-level divergence, are all favorable for intense landfalling TCs and their survival after landfall, thus contributing to the increasing destructive potential of landfalling TCs over China.

Different Responses of Tropical Cyclone Tracks Over the Western North Pacific and North Atlantic to Two Distinct Sea Surface Temperature Warming Patterns

AbstractHow future tropical cyclone (TC) activity could change under global warming is enormously important to society, which has been widely assessed using state‐of‐the‐art climate models. However, these models were predominantly based on projection of an El Niño‐like warming pattern. Recent studies suggested that a La Niña‐like warming pattern is also possible. Here we compare the responses of TC track density (TCTD) over the western North Pacific and North Atlantic to the two distinct global warming patterns. We find that the La Niña‐like warming pattern reduces western North Pacific TCTD except in the South China Sea and along China coast and increases NA TCTD, while the El Niño‐like warming pattern generally reduces TCTD in both basins. This is due to different responses of large‐scale dynamic/thermodynamic conditions to the distinct zonal sea surface temperature gradients associated with the two warming patterns. These results help better understand potential future change in TC tracks.

Autumn Tropical Cyclones over the Western North Pacific during 1949-2016: A Statistical Study

We used tropical cyclone (TC) best track data for 1949–2016, provided by the Shanghai Typhoon Institute, China Meteorological Administration (CMA-STI), and a TC size dataset (1980-2016) derived from geostationary satellite infrared images to analyze the statistical characteristics of autumn TCs over the western North Pacific (WNP). We investigated TC genesis frequency, location, track density, intensity, outer size, and landfalling features, as well as their temporal and spatial evolution characteristics. On average, the number of autumn TCs accounted for 42.1% of the annual total, slightly less than that of summer TCs (42.7%). However, TCs classified as strong typhoons or super typhoons were more frequent in autumn than in summer. In most years of the 68-yr study period, there was an inverse relationship between the number of autumn TCs and that of summer TCs. The genesis of autumn TCs was concentrated at three centers over the WNP: the first is located near (14°N, 115°E) over the northeastern South China Sea and the other two are located in the vast oceanic area east of the Philippines around (14°N, 135°E) and (14°N, 145°E), respectively. In terms of intensity, the eight strongest TCs during the study period all occurred in autumn. It is revealed that autumn TCs were featured with strong typhoons and super typhoons, with the latter accounting for 28.1% of the total number of autumn TCs. Statistically, the average 34-knot radius (R34) of autumn TCs increased with TC intensity. From 1949 to 2016, 164 autumn TCs made landfall in China, with an average annual number of 2.4. Autumn TCs were most likely to make landfall in Guangdong Province, followed by Hainan Province and Taiwan Island.