Change in Destructiveness of Landfalling Tropical Cyclones over China in Recent Decades

This study investigates changes in the destructiveness of landfalling tropical cyclones (TCs) over China during 1975–2014. Using four different TC datasets, it is found that TCs making landfall over east China (TCEC) have tended to be more destructive in recent decades, with a significant increase in the power dissipation index (PDI) after landfall. Both time series analysis and diagnostic analysis reveal that such an increase in the PDI of TCEC is associated with concomitant enhancement in landfall frequency as well as landfall intensity over east China. In contrast, changes in the PDI of TCs making landfall over south China (TCSC) are less apparent. Examination of different TC-related parameters shows no obvious changes in terms of landfall frequency, duration, and maximum intensity of TCSC. Diagnostic analysis further suggests that the reduction in TC occurrence over south China offsets considerably the positive effects of the intensity and the nonlinear term. Further examination of the environmental parameters reveals significant changes in the large-scale steering flow in recent decades, which is characterized by a prominent cyclonic circulation centered over southeast China. The southeasterly flows on the eastern flank of the cyclonic circulation tend to favor subsequent landfall of TCs over east China, resulting in an increase in landfall frequency, which contributes in part to the enhanced PDI of TCs over this region. Meanwhile, the slowing down of the mean translation speed of TCEC and the weakening of vertical wind shear coupled with warmer SSTs in the WNP tend to favor the intensification of TCEC, leading to an increase in intensity and hence the PDI of TCs over east China.

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Observed Rainfall Asymmetry in Tropical Cyclones Making Landfall over China

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-13-0359.1 ◽

2015 ◽

Vol 54 (1) ◽

pp. 117-136 ◽

Cited By ~ 19

Author(s):

Zifeng Yu ◽

Yuqing Wang ◽

Haiming Xu

Keyword(s):

Tropical Cyclones ◽

South China ◽

Wind Shear ◽

Large Scale ◽

Mainland China ◽

Vertical Wind Shear ◽

Vertical Wind ◽

East China ◽

Rainfall Estimates

AbstractIn this study, the rainfall asymmetries in tropical cyclones (TCs) that made landfall in the Hainan (HN), Guangdong (GD), Fujian (FJ), and Zhejiang (ZJ) provinces of mainland China and Taiwan (TW) from 2001 to 2009 were analyzed on the basis of TRMM satellite 3B42 rainfall estimates. The results reveal that in landfalling TCs, the wavenumber 1 rainfall asymmetry shows the downshear to downshear-left maximum in environmental vertical wind shear (VWS), which is consistent with previous studies for TCs over the open oceans. A cyclonic rotation from south China to east China in the location of the rainfall maximum has been identified. Before landfall, the location of the rainfall maximum rotated from southwest to southeast of the TC center for TCs making landfall in the regions from HN to GD, TW, FJ, and ZJ. After landfall, the rotation became from southwest to northeast of the TC center from south China to east China. It is shown that this cyclonic rotation in the location of the rainfall maximum is well correlated with a cyclonic rotation from south China to east China in the environmental VWS between 200 and 850 hPa, indicating that the rainfall asymmetry in TCs that made landfall over China is predominantly controlled by the large-scale VWS. The cyclonic rotation of VWS is found to be related to different interactions between the midlatitude westerlies and the landfalling TCs in different regions. The results also indicate that the axisymmetric (wavenumber 0) component of rainfall generally decreased rapidly after landfall in most studied regions.

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Observational Analysis of Tropical Cyclone Formation Associated with Monsoon Gyres

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-12-0117.1 ◽

2013 ◽

Vol 70 (4) ◽

pp. 1023-1034 ◽

Cited By ~ 38

Author(s):

Liguang Wu ◽

Huijun Zong ◽

Jia Liang

Keyword(s):

Tropical Cyclone ◽

Tropical Cyclones ◽

Western North Pacific ◽

Large Scale ◽

Vertical Wind Shear ◽

Relative Vorticity ◽

Monsoon Trough ◽

Cyclonic Circulation ◽

Tropical Cyclone Formation ◽

Monsoon Gyre

Abstract Large-scale monsoon gyres and the involved tropical cyclone formation over the western North Pacific have been documented in previous studies. The aim of this study is to understand how monsoon gyres affect tropical cyclone formation. An observational study is conducted on monsoon gyres during the period 2000–10, with a focus on their structures and the associated tropical cyclone formation. A total of 37 monsoon gyres are identified in May–October during 2000–10, among which 31 monsoon gyres are accompanied with the formation of 42 tropical cyclones, accounting for 19.8% of the total tropical cyclone formation. Monsoon gyres are generally located on the poleward side of the composited monsoon trough with a peak occurrence in August–October. Extending about 1000 km outward from the center at lower levels, the cyclonic circulation of the composited monsoon gyre shrinks with height and is replaced with negative relative vorticity above 200 hPa. The maximum winds of the composited monsoon gyre appear 500–800 km away from the gyre center with a magnitude of 6–10 m s−1 at 850 hPa. In agreement with previous studies, the composited monsoon gyre shows enhanced southwesterly flow and convection on the south-southeastern side. Most of the tropical cyclones associated with monsoon gyres are found to form near the centers of monsoon gyres and the northeastern end of the enhanced southwesterly flows, accompanying relatively weak vertical wind shear.

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Key Environmental Factors for Rapid Intensification of the South China Sea Tropical Cyclones

Frontiers in Earth Science ◽

10.3389/feart.2020.609727 ◽

2021 ◽

Vol 8 ◽

Author(s):

Yao Chen ◽

Si Gao ◽

Xun Li ◽

Xinyong Shen

Keyword(s):

South China Sea ◽

Tropical Cyclones ◽

South China ◽

Vertical Wind Shear ◽

Onset Time ◽

The South China Sea ◽

Rapid Intensification ◽

The South ◽

Translation Speed ◽

China Sea

Forecasting rapid intensification (RI) of the South China Sea (SCS) tropical cyclones (TCs) remains an operational challenge, mainly owing to the incomplete understanding of its physical mechanisms. Based on TC best-track data, atmospheric analysis data, and sea surface temperature data, this study compares temporal evolution characteristics of environmental conditions from the previous 24 h to the onset time for RI and non-RI TCs in the SCS during 2000–2018, and then identifies key factors for RI of the SCS TCs using the box difference index and stepwise regression. A combination of strong divergence in the upper troposphere and strong convergence in the boundary layer, weak deep-layer vertical wind shear, fast storm translation speed, and high TC intensification potential (i.e., maximum potential intensity minus current intensity) north of the storm center at the previous 24 h are favorable for RI of the SCS TCs, and their importance for RI is in descending order. The results may shed light on operational forecasting of rapid intensification of the SCS TCs.

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Impact of Different Types of ENSO Years on Intensity Changes of Landfalling Tropical Cyclones over China

Atmosphere ◽

10.3390/atmos10030161 ◽

2019 ◽

Vol 10 (3) ◽

pp. 161

Author(s):

Lu Liu

Keyword(s):

Tropical Cyclones ◽

South China ◽

Southern China ◽

Eastern China ◽

Broad Band ◽

Relative Vorticity ◽

Central Pacific ◽

Translation Speed ◽

Easterly Wind ◽

Landfalling Tropical Cyclones

This study examines whether there are significant differences in intensity and destructiveness of landfalling tropical cyclones (TCs) over China in central Pacific warm (CPW), eastern Pacific warm (EPW) and La Niña (LA) years. By analyzing different seasons and locations of TCs making landfall over China, it was found that TCs in LA years generally had a larger power dissipation index (PDI) and may cause more disasters in China, while TCs in EPW years had a larger PDI over South China in autumn. A larger PDI of TCSC (landing location in Southern China) usually occurred in EPW years and a larger PDI of TCEC (landing location in Eastern China) occurred in LA years, compared with CPW years. The TCs in LA years were generally stronger, more frequent, and of longer duration over China, because of the positive relative humidity (RH) anomalies, the significant anomalous cyclone that occupied the South China Sea (SCS), and the easterly wind anomalies providing a beneficial steering flow for TCs making landfall. In EPW years, although TCs were less frequent, they had stronger intensity when making landfall and a longer lifetime over land which was mainly caused by a broad band of anomalous westerlies over the SCS giving rise to a belt of positive relative vorticity anomalies, as well as the slow translation speed of TCs before landfall supplying more energy for TCs to survive over land. Overall, we conclude that greater caution is warranted when TCs occur in LA and EPW years, as they may result in more serious disasters in China.

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Increasing Destructive Potential of Landfalling Tropical Cyclones over China

Journal of Climate ◽

10.1175/jcli-d-19-0451.1 ◽

2020 ◽

Vol 33 (9) ◽

pp. 3731-3743 ◽

Cited By ~ 1

Author(s):

Lu Liu ◽

Yuqing Wang ◽

Ruifen Zhan ◽

Jing Xu ◽

Yihong Duan

Keyword(s):

Surface Temperature ◽

Tropical Cyclones ◽

Land Surface ◽

Large Scale ◽

Mainland China ◽

Vertical Wind Shear ◽

Coastal Sea ◽

Landfalling Tropical Cyclones ◽

Increasing Trends ◽

Destructive Potential

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.

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A 7-Year Climatology of Warm-Sector Heavy Rainfall over South China during the Pre-Summer Months

Atmosphere ◽

10.3390/atmos12070914 ◽

2021 ◽

Vol 12 (7) ◽

pp. 914

Author(s):

Tao Chen ◽

Da-Lin Zhang

Keyword(s):

South China ◽

Heavy Rainfall ◽

Large Scale ◽

Convective Available Potential Energy ◽

Potential Temperature ◽

Vertical Wind Shear ◽

Precipitable Water ◽

Atmospheric Parameter ◽

Low Level ◽

Warm Sector

In view of the limited predictability of heavy rainfall (HR) events and the limited understanding of the physical mechanisms governing the initiation and organization of the associated mesoscale convective systems (MCSs), a composite analysis of 58 HR events over the warm sector (i.e., far ahead of the surface cold front), referred to as WSHR events, over South China during the months of April to June 2008~2014 is performed in terms of precipitation, large-scale circulations, pre-storm environmental conditions, and MCS types. Results show that the large-scale circulations of the WSHR events can be categorized into pre-frontal, southwesterly warm and moist ascending airflow, and low-level vortex types, with higher frequency occurrences of the former two types. Their pre-storm environments are characterized by a deep moist layer with >50 mm column-integrated precipitable water, high convective available potential energy with the equivalent potential temperature of ≥340 K at 850 hPa, weak vertical wind shear below 400 hPa, and a low-level jet near 925 hPa with weak warm advection, based on atmospheric parameter composite. Three classes of the corresponding MCSs, exhibiting peak convective activity in the afternoon and the early morning hours, can be identified as linear-shaped, a leading convective line adjoined with trailing stratiform rainfall, and comma-shaped, respectively. It is found that many linear-shaped MCSs in coastal regions are triggered by local topography, enhanced by sea breezes, whereas the latter two classes of MCSs experience isentropic lifting in the southwesterly warm and moist flows. They all develop in large-scale environments with favorable quasi-geostrophic forcing, albeit weak. Conceptual models are finally developed to facilitate our understanding and prediction of the WSHR events over South China.

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Rainfall Mechanisms for One of the Wettest Tropical Cyclones on Record in Australia—Oswald (2013)

Monthly Weather Review ◽

10.1175/mwr-d-19-0168.1 ◽

2020 ◽

Vol 148 (6) ◽

pp. 2503-2525

Author(s):

Difei Deng ◽

Elizabeth A. Ritchie

Keyword(s):

Tropical Cyclones ◽

Wind Shear ◽

Heavy Rainfall ◽

Large Scale ◽

Vertical Wind Shear ◽

Monsoon Trough ◽

Vertical Wind ◽

Lower Latitude ◽

Cape York ◽

Frictional Convergence

Abstract Tropical Cyclone Oswald (2013) is considered to be one of the highest-impact storms to make landfall in northern Australia even though it only reached a maximum category 1 intensity on the Australian category scale. After making landfall on the west coast of Cape York Peninsula, Oswald turned southward, and persisted for more than 7 days moving parallel to the coastline as far south as 30°S. As one of the wettest tropical cyclones (TCs) in Australian history, the favorable configurations of a lower-latitude active monsoon trough and two consecutive midlatitude trough–jet systems generally contributed to the maintenance of the Oswald circulation over land and prolonged rainfall. As a result, Oswald produced widespread heavy rainfall along the east coast with three maximum centers near Weipa, Townsville, and Rockhampton, respectively. Using high-resolution WRF simulations, the mechanisms associated with TC Oswald’s rainfall are analyzed. The results show that the rainfall involved different rainfall mechanisms at each stage. The land–sea surface friction contrast, the vertical wind shear, and monsoon trough were mostly responsible for the intensity and location for the first heavy rainfall center on the Cape York Peninsula. The second torrential rainfall near Townsville was primarily a result of the local topography and land–sea frictional convergence in a conditionally unstable monsoonal environment with frictional convergence due to TC motion modulating some offshore rainfall. The third rainfall area was largely dominated by persistent high vertical wind shear forcing, favorable large-scale quasigeostrophic dynamic lifting from two midlatitude trough–jet systems, and mesoscale frontogenesis lifting.

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Modulation of North Pacific and North Atlantic tropical cyclones by tropical trans-basin variability and ENSO during May-October

Journal of Climate ◽

10.1175/jcli-d-19-0866.1 ◽

2020 ◽

pp. 1

Author(s):

Shaohua Chen ◽

Haikun Zhao ◽

Graciela B. Raga ◽

Philip J. Klotzbach

Keyword(s):

Tropical Cyclones ◽

North Atlantic ◽

North Pacific ◽

Large Scale ◽

Vertical Wind Shear ◽

Relative Vorticity ◽

Low Level ◽

Scale Factors ◽

Frequency Changes ◽

Dipole Modulation

AbstractThis study highlights the distinct modulation of May-October tropical cyclones (TCs) in the western North Pacific (WNP), eastern North Pacific (ENP) and North Atlantic (NATL) basins by tropical trans-basin variability (TBV) and ENSO. The pure TBV significantly modulates total TC counts in all three basins, with more TCs in the WNP and ENP and fewer TCs in the NATL during warm TBV years and fewer TCs in the WNP and ENP and more TCs in the NATL during cold TBV years. By contrast, the pure ENSO signal shows no impact on total TC count over any of the three basins. These results are consistent with changes in large scale factors associated with TBV and ENSO. Low-level relative vorticity (VOR) is an important driver of WNP TC genesis frequency, with broad agreement between the observed spatial distribution of TC genesis and TBV/ENSO-associated VOR anomalies. TBV significantly affects ENP TC frequency due to changes in basin wide vertical wind shear and sea surface temperatures, while the modulation in TC frequency by ENSO is primarily caused by a north-south dipole modulation of large-scale atmospheric and oceanic factors. The pure TBV-related low-level VOR changes appear to be the most important factor modulating NATL TC frequency. Changes in large-scale factors compare well with the budget of synoptic-scale eddy kinetic energy. Possible physical processes associated with pure TBV and pure ENSO that modulate TC frequency are further discussed. This study contributes to the understanding of TC inter-annual variability and could thus be helpful for seasonal TC forecasting.

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Diurnal Variation of the Convective Area and Eye Size Associated with the Rapid Intensification of Tropical Cyclones

Monthly Weather Review ◽

10.1175/mwr-d-19-0345.1 ◽

2020 ◽

Vol 148 (10) ◽

pp. 4061-4082

Author(s):

Jae-Deok Lee ◽

Chun-Chieh Wu ◽

Kosuke Ito

Keyword(s):

Diurnal Variation ◽

Tropical Cyclones ◽

Satellite Imagery ◽

Large Scale ◽

Linear Regression Analysis ◽

Heat Content ◽

Vertical Wind Shear ◽

Mixed Phase ◽

Eye Size ◽

The Impact

AbstractThis study examines the diurnal variation of the convective area and eye size of 30 rapidly intensifying tropical cyclones (RI TCs) that occurred in the western North Pacific from 2015 to 2017 utilizing Himawari-8 satellite imagery. The convective area can be divided into the active convective area (ACA), mixed phase, and inactive convective area (IACA) based on specific thresholds of brightness temperature. In general, ACA tends to develop vigorously from late afternoon to early the next morning, while mixed phase and IACA develop during the day. This diurnal pattern indicates the potential for ACA to evolve into mixed phase or IACA over time. From the 30 samples, RI TCs tend to have at least a single-completed diurnal signal of ACA inside the radius of maximum wind (RMW) during the rapidly intensifying period. In the same period, the RMW also contracts significantly. Meanwhile, more intense storms such as those of category 4 or 5 hurricane intensity are apt to have continuous ACA inside the RMW and maintain eyewall convective clouds. These diurnal patterns of the ACA could vary depending on the impact of large-scale environments such as vertical wind shear, ocean heat content, environmental mesoscale convection, and terrain. The linear regression analysis shows that from the tropical storm stage, RI commences after a slow intensification period, which enhances both the primary circulation and eyewall convective cloud. Finally, after the eye structure appears in satellite imagery, its size changes inversely to the diurnal variation of the convective activity (e.g., the eye size becomes larger during the daytime).

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