In this study, the dependence of tropical cyclone （TC） development on the inner-core structure of the parent vortex is examined using a pair of idealized numerical simulations. It is found that the radial profile of...In this study, the dependence of tropical cyclone （TC） development on the inner-core structure of the parent vortex is examined using a pair of idealized numerical simulations. It is found that the radial profile of inner-core relative vorticity may have a great impact on its subsequent development. For a system with a larger inner-core relative vorticity/inertial stability, the conversion ratio of the diabatic heating to kinetic energy is greater. Furthermore, the behavior of the convective vorticity eddies is likely modulated by the system-scale circulation. For a parent vortex with a relatively higher inner-core vorticity and larger negative radial vorticity gradient, convective eddy formation and radially inward propagation is promoted through vorticity segregation. This provides a greater potential for these small-scale convective cells to self-organize into a mesoscale inner-core structure in the TC. In turn, convectively induced diabatic heating that is close to the center, along with higher inertial stability, efficiently enhances system-scale secondary circulation. This study provides a solid basis for further research into how the initial structure of a TC influences storm dynamics and thermodynamics.展开更多
The sensitivity of TC intensification and track to the initial inner-core structure on a β plane is investigated using a numerical model. The results show that the vortex with large inner-core winds（CVEX-EXP） exper...The sensitivity of TC intensification and track to the initial inner-core structure on a β plane is investigated using a numerical model. The results show that the vortex with large inner-core winds（CVEX-EXP） experiences an earlier intensification than that with small inner-core winds（CCAVE-EXP）, but they have nearly the same intensification rate after spin-up. In the early stage, the convective cells associated with surface heat flux are mainly confined within the inner-core region in CVEXEXP, whereas the vortex in CCAVE-EXP exhibits a considerably asymmetric structure with most of the convective vortices being initiated to the northeast in the outer-core region due to the β effect. The large inner-core inertial stability in CVEX-EXP can prompt a high efficiency in the conversion from convective heating to kinetic energy. In addition, much stronger straining deformation and PBL imbalance in the inner-core region outside the primary eyewall ensue during the initial development stage in CVEX-EXP than in CCAVE-EXP, which is conducive to the rapid axisymmetrization and early intensification in CVEX-EXP. The TC track in CVEX-EXP sustains a northwestward displacement throughout the integration, whereas the TC in CCAVE-EXP undergoes a northeastward recurvature when the asymmetric structure is dominant. Due to the enhanced asymmetric convection to the northeast of the TC center in CCAVE-EXP, a pair of secondary gyres embedded within the large-scale primary β gyres forms, which modulates the ventilation flow and thus steers the TC to move northeastward.展开更多
The topography of the inner core is crucial to understand its growth process and interaction with the geodynamo. With the accuracy of teleseismic waveform doublets in determining the travel-time shifts between PKPcd a...The topography of the inner core is crucial to understand its growth process and interaction with the geodynamo. With the accuracy of teleseismic waveform doublets in determining the travel-time shifts between PKPcd and PKPdf inner-core phases, we examined the temporal change of the inner-core boundary sampled by new earthquake doublets that occurred in the Western Pacific and those previously found from the South Sandwich Islands. The receiver stations are those within the distance range of 128°–142° from the hypocenters of the waveform doublets. Our results suggest that temporal changes in PKPcd-PKPdf differential times are very subtle except some isolated regions under central America and Africa. The observations may indicate localized topography of the inner core and/or the inner-core boundary as transient slurry in isolated regions.展开更多
Studies on tropical cyclone(TC)inner-core size have become increasingly active in recent years.However,few studies have investigated the trend of TC inner-core size.Here,we introduce a new index to measure TC inner-co...Studies on tropical cyclone(TC)inner-core size have become increasingly active in recent years.However,few studies have investigated the trend of TC inner-core size.Here,we introduce a new index to measure TC inner-core size and calculate the observed trend.This index can greatly reduce the influence of data heterogeneity and uncertainty.It also considers public concern because the new index is mainly determined by the inner-core size of strong TCs,which attract more public attention than weak TCs.The results show that in the past decades,TC inner-core size has a significant downtrend that is significant above the 99%confidence level when the new index is used.We also show that this trend is probably related to the increase in TC intensity and relatively small inner-core size of strong TCs.Moreover,relative sea surface temperature(SST)is assumed to make contributions to the downtrend of TC inner-core size,which has a significant negative correlation with the new index.展开更多
台风尺度表征了台风低层风场特定风速半径大小,是台风灾害影响范围的重要度量.针对超强台风“舒力基”(2021),对其尺度可预报性进行初步探讨.结果表明,模式可以模拟出台风发展初期台风尺度(内核尺度RMW、外围尺度R17)的演变趋势.基于集...台风尺度表征了台风低层风场特定风速半径大小,是台风灾害影响范围的重要度量.针对超强台风“舒力基”(2021),对其尺度可预报性进行初步探讨.结果表明,模式可以模拟出台风发展初期台风尺度(内核尺度RMW、外围尺度R17)的演变趋势.基于集合预报的模拟试验,具体分析了内核尺度RMW、外围尺度R17演变及其误差增长特征.台风预报总体误差主要出现在对流层下层850 h Pa,距离台风中心50~150 km.从初始环境场看,初始相对湿度是影响台风尺度误差增长的重要因子,初始高湿环境有利于台风发展阶段的台风尺度高离散度,从而限制了台风尺度的可预报性.在一定程度上,外围风圈半径的可预报性要高于内核风圈半径.展开更多
基金sponsored by the National Key Basic Research Program of China (Grant No.2015CB452803)the State Key Laboratory of Severe Weather,Chinese Academy of Meteorological Sciences (Grant No.2014LASW-B08)+1 种基金the "six peaks of high-level talents" funding projectthe Key University Science Research Project of Jiangsu Province (Grant No.14KJA170005)
文摘In this study, the dependence of tropical cyclone （TC） development on the inner-core structure of the parent vortex is examined using a pair of idealized numerical simulations. It is found that the radial profile of inner-core relative vorticity may have a great impact on its subsequent development. For a system with a larger inner-core relative vorticity/inertial stability, the conversion ratio of the diabatic heating to kinetic energy is greater. Furthermore, the behavior of the convective vorticity eddies is likely modulated by the system-scale circulation. For a parent vortex with a relatively higher inner-core vorticity and larger negative radial vorticity gradient, convective eddy formation and radially inward propagation is promoted through vorticity segregation. This provides a greater potential for these small-scale convective cells to self-organize into a mesoscale inner-core structure in the TC. In turn, convectively induced diabatic heating that is close to the center, along with higher inertial stability, efficiently enhances system-scale secondary circulation. This study provides a solid basis for further research into how the initial structure of a TC influences storm dynamics and thermodynamics.
基金supported financially by the National Basic Research Program of China(Grant No.2014CB953902)the National Natural Science Foundation of China(Grant Nos.41275001 and 41475074)
文摘The sensitivity of TC intensification and track to the initial inner-core structure on a β plane is investigated using a numerical model. The results show that the vortex with large inner-core winds（CVEX-EXP） experiences an earlier intensification than that with small inner-core winds（CCAVE-EXP）, but they have nearly the same intensification rate after spin-up. In the early stage, the convective cells associated with surface heat flux are mainly confined within the inner-core region in CVEXEXP, whereas the vortex in CCAVE-EXP exhibits a considerably asymmetric structure with most of the convective vortices being initiated to the northeast in the outer-core region due to the β effect. The large inner-core inertial stability in CVEX-EXP can prompt a high efficiency in the conversion from convective heating to kinetic energy. In addition, much stronger straining deformation and PBL imbalance in the inner-core region outside the primary eyewall ensue during the initial development stage in CVEX-EXP than in CCAVE-EXP, which is conducive to the rapid axisymmetrization and early intensification in CVEX-EXP. The TC track in CVEX-EXP sustains a northwestward displacement throughout the integration, whereas the TC in CCAVE-EXP undergoes a northeastward recurvature when the asymmetric structure is dominant. Due to the enhanced asymmetric convection to the northeast of the TC center in CCAVE-EXP, a pair of secondary gyres embedded within the large-scale primary β gyres forms, which modulates the ventilation flow and thus steers the TC to move northeastward.
基金supported by the Natural Science Foundation of China(41330209)the Ministry of Science and Technology of China(2014CB845901)the China Earthquake Administration
文摘The topography of the inner core is crucial to understand its growth process and interaction with the geodynamo. With the accuracy of teleseismic waveform doublets in determining the travel-time shifts between PKPcd and PKPdf inner-core phases, we examined the temporal change of the inner-core boundary sampled by new earthquake doublets that occurred in the Western Pacific and those previously found from the South Sandwich Islands. The receiver stations are those within the distance range of 128°–142° from the hypocenters of the waveform doublets. Our results suggest that temporal changes in PKPcd-PKPdf differential times are very subtle except some isolated regions under central America and Africa. The observations may indicate localized topography of the inner core and/or the inner-core boundary as transient slurry in isolated regions.
基金Supported by the National Natural Science Foundation of China(42075035 and 41605072)。
文摘Studies on tropical cyclone(TC)inner-core size have become increasingly active in recent years.However,few studies have investigated the trend of TC inner-core size.Here,we introduce a new index to measure TC inner-core size and calculate the observed trend.This index can greatly reduce the influence of data heterogeneity and uncertainty.It also considers public concern because the new index is mainly determined by the inner-core size of strong TCs,which attract more public attention than weak TCs.The results show that in the past decades,TC inner-core size has a significant downtrend that is significant above the 99%confidence level when the new index is used.We also show that this trend is probably related to the increase in TC intensity and relatively small inner-core size of strong TCs.Moreover,relative sea surface temperature(SST)is assumed to make contributions to the downtrend of TC inner-core size,which has a significant negative correlation with the new index.
文摘台风尺度表征了台风低层风场特定风速半径大小,是台风灾害影响范围的重要度量.针对超强台风“舒力基”(2021),对其尺度可预报性进行初步探讨.结果表明,模式可以模拟出台风发展初期台风尺度(内核尺度RMW、外围尺度R17)的演变趋势.基于集合预报的模拟试验,具体分析了内核尺度RMW、外围尺度R17演变及其误差增长特征.台风预报总体误差主要出现在对流层下层850 h Pa,距离台风中心50~150 km.从初始环境场看,初始相对湿度是影响台风尺度误差增长的重要因子,初始高湿环境有利于台风发展阶段的台风尺度高离散度,从而限制了台风尺度的可预报性.在一定程度上,外围风圈半径的可预报性要高于内核风圈半径.
