对2004年6月中下旬郑州地区3次比较典型的强对流天气的高低空形势、物理量场及雷达资料的对比分析结果表明:1)500 h Pa冷涡的位置在42°N以南,郑州上游有较强冷平流侵入,并且700 h Pa和850 h Pa也有对应低值系统存在,是郑州地区强...对2004年6月中下旬郑州地区3次比较典型的强对流天气的高低空形势、物理量场及雷达资料的对比分析结果表明:1)500 h Pa冷涡的位置在42°N以南,郑州上游有较强冷平流侵入,并且700 h Pa和850 h Pa也有对应低值系统存在,是郑州地区强对流天气发生发展的大尺度环流背景。2)地面中尺度辐合线的存在是强对流天气的主要触发机制。3)动力因子的差异造成了不同类型的强对流天气。4)雷暴云中强下沉冷空气在近地层强烈辐散能够引起地面大风。5)水汽因子的差异决定了雷雨能否发生。上下层均为干冷空气时一般仅伴有大风天气;低层暖湿、中高层干冷时能增加大气的对流性不稳定,有利于强降水和局地冰雹的产生。展开更多
In general,a mesoscale cyclonic(anticyclonic)eddy has a colder(warmer)core,and it is considered as a cold(warm)eddy.However,recently research found that there are a number of"abnormal"mesoscale cyclonic(anti...In general,a mesoscale cyclonic(anticyclonic)eddy has a colder(warmer)core,and it is considered as a cold(warm)eddy.However,recently research found that there are a number of"abnormal"mesoscale cyclonic(anticyclonic)eddies associated with warm(cold)cores in the South China Sea(SCS).These"abnormal"eddies pose a challenge to previous works on eddy detection,characteristic analysis,eddy-induced heat and salt transports,and even on mesoscale eddy dynamics.Based on a 9-year(2000–2008)numerical modelling data,the cyclonic warm-core eddies(CWEs)and anticyclonic cold-core eddies(ACEs)in the SCS are analyzed.This study found that the highest incidence area of the"abnormal"eddies is the northwest of Luzon Strait.In terms of the eddy snapshot counting method,8620 CWEs and 9879 ACEs are detected,accounting for 14.6%and 15.8%of the total eddy number,respectively.The size of the"abnormal"eddies is usually smaller than that of the"normal"eddies,with the radius only around 50 km.In the generation time aspect,they usually appear within the 0.1–0.3 interval in the normalized eddy lifespan.The survival time of CWEs(ACEs)occupies 16.3%(17.1%)of the total eddy lifespan.Based on two case studies,the intrusion of Kuroshio warm water is considered as a key mechanism for the generation of these"abnormal"eddies near the northeastern SCS.展开更多
The variations of the frontogenetic trend of a cold filament induced by the cross-filament wind and wave fields are studied by a non-hydrostatic large eddy simulation. Five cases with different strengths of wind and w...The variations of the frontogenetic trend of a cold filament induced by the cross-filament wind and wave fields are studied by a non-hydrostatic large eddy simulation. Five cases with different strengths of wind and wave fields are studied.The results show that the intense wind and wave fields further break the symmetries of submesoscale flow fields and suppress the levels of filament frontogenesis. The changes of secondary circulation directions—that is, the conversion between the convergence and divergence of the surface cross-filament currents with the downwelling and upwelling jets in the filament center—are associated with the inertial oscillation. The filament frontogenesis and frontolysis caused by the changes of secondary circulation directions may periodically sharpen and smooth the gradient of submesoscale flow fields.The lifecycle of the cold filament may include multiple stages of filament frontogenesis and frontolysis.展开更多
In this study,an improved delayed detached eddy simulation(IDDES)method based on the shear-stress transport(SST)k-ωturbulence model has been used to investigate the underbody flow characteristics of a high-speed trai...In this study,an improved delayed detached eddy simulation(IDDES)method based on the shear-stress transport(SST)k-ωturbulence model has been used to investigate the underbody flow characteristics of a high-speed train operating at lower temperatures with Reynolds number Re=1.85×10^(6).The accuracy of the numerical method has been validated by wind tunnel tests.The aerodynamic drag of the train,pressure distribution on the surface of the train,the flow around the vehicle,and the wake flow are compared for four temperature values:+15℃,0℃,−15℃,and−30℃.It was found that lower operating t emperatures significantly increased the aerodynamic drag force of the train.The drag overall at low temperatures increased by 5.3%(0℃),11.0%(−15℃),and 17.4%(−30℃),respectively,relative to the drag at+15℃.In addition,the low temperature e nhances the positive and negative pressures around and on the surface of the car body,raising the peak positive and negative pressure values in areas susceptible to impingement flow and to rapid changes in flow velocity.The range of train-induced winds around the car body is significantly reduced,the distribution area of vorticity moves backwards,and the airflow velocity in the bogie cavity is significantly increased.At the same time,the temperature causes a significant velocity reduction in the wake flow.It can be seen that the temperature reduction can seriously disturb the normal operation of the train while increasing the aerodynamic drag and energy consumption,and significantly interfering with the airflow characteristics around the car body.展开更多
Using observational data from multiple satellites,we studied seasonal variations of the shape and location of the Luzon cold eddy(LCE)northwest of Luzon Island.The shape and location of the LCE have obvious seasonal v...Using observational data from multiple satellites,we studied seasonal variations of the shape and location of the Luzon cold eddy(LCE)northwest of Luzon Island.The shape and location of the LCE have obvious seasonal variations.The LCE occurs,develops,and disappears from December to April of the next year.During this period,the shape of the LCE changed from a flat ellipse to a circular ellipse,and the change in shape can be reflected by the increase of the ellipticity of the LCE from 0.16 to 0.82.The latitude of center location of the LCE changes from 17.4°N to 19°N,and the change in latitude can reach 1.6°.Further study showed that seasonal variation of the northeast monsoon intensity leads to the change in the shape and location of the LCE.The seasonal variation of the LCE shape can significantly alter the spatial distribution of the thermal front and chlorophyll a northwest of the Luzon Island by geostrophic advection.展开更多
Based on observed temperature data since the 1950s, long-term variability of the summer sharp thermocline in the Yellow Sea Cold Water Mass （YSCWM） and East China Sea Cold Eddy （ECSCE） areas is examined. Relations...Based on observed temperature data since the 1950s, long-term variability of the summer sharp thermocline in the Yellow Sea Cold Water Mass （YSCWM） and East China Sea Cold Eddy （ECSCE） areas is examined. Relationships between the thermocline and atmospheric and oceanic forcing were investigated using multiyear wind, Kuroshio discharge and air temperature data. Results show that： 1） In the YSCWM area, thermocline strength shows about 4-year and 16-year period oscillations. There is high correlation between summer thermocline strength and local atmospheric temperature in summer and the previous winter; 2） In the ECSCE area, interannual oscillation of thermocline strength with about a 4-year period （stronger in El Nifio years） is strongly correlated with that of local wind stress. A transition from weak to strong thermocline during the mid 1970s is consistent with a 1976/1977 climate shift and Kuroshio volume transport; 3） Long-term changes of the thermocline in both regions are mainly determined by deep layer water, especially on the decadal timescale. However, surface water can modify the thermocline on an interannual timescale in the YSCWM area.展开更多
文摘对2004年6月中下旬郑州地区3次比较典型的强对流天气的高低空形势、物理量场及雷达资料的对比分析结果表明:1)500 h Pa冷涡的位置在42°N以南,郑州上游有较强冷平流侵入,并且700 h Pa和850 h Pa也有对应低值系统存在,是郑州地区强对流天气发生发展的大尺度环流背景。2)地面中尺度辐合线的存在是强对流天气的主要触发机制。3)动力因子的差异造成了不同类型的强对流天气。4)雷暴云中强下沉冷空气在近地层强烈辐散能够引起地面大风。5)水汽因子的差异决定了雷雨能否发生。上下层均为干冷空气时一般仅伴有大风天气;低层暖湿、中高层干冷时能增加大气的对流性不稳定,有利于强降水和局地冰雹的产生。
基金The National Natural Science Foundation of China under contract Nos 41906008,41806039,41806030,42076021,41676010 and 41706205the State Key Laboratory of Tropical Oceanography,South China Sea Institute of Oceanology,Chinese Academy of Sciences under contract Nos LTO1902 and LTO1807+9 种基金the Strategic Priority Research Program of Chinese Academy of Sciences under contract No.XDB42000000the Youth Innovation Promotion Association CAS under contract No.2017397the Pearl River S&T Nova Program of Guangzhou under contract No.201806010105the Open Fund of State Key Laboratory of Satellite Ocean Environment Dynamics,Second Institute of OceanographyMNR under contract No.QNHX2022the Startup Foundation for Introducing Talent of Nanjing University of Information Science&Technology under contract No.2019r049the Startup Foundation for Introducing Talent of Zhejiang Ocean Universitythe National Key Research Programs of China under contract Nos2016YFC1401407 and 2017YFA0604100the National Programme on Global Change and Air-Sea Interaction under contract Nos GASIIPOVAI-03 and GASI-IPOVAI-05the Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)under contract No.311020004。
文摘In general,a mesoscale cyclonic(anticyclonic)eddy has a colder(warmer)core,and it is considered as a cold(warm)eddy.However,recently research found that there are a number of"abnormal"mesoscale cyclonic(anticyclonic)eddies associated with warm(cold)cores in the South China Sea(SCS).These"abnormal"eddies pose a challenge to previous works on eddy detection,characteristic analysis,eddy-induced heat and salt transports,and even on mesoscale eddy dynamics.Based on a 9-year(2000–2008)numerical modelling data,the cyclonic warm-core eddies(CWEs)and anticyclonic cold-core eddies(ACEs)in the SCS are analyzed.This study found that the highest incidence area of the"abnormal"eddies is the northwest of Luzon Strait.In terms of the eddy snapshot counting method,8620 CWEs and 9879 ACEs are detected,accounting for 14.6%and 15.8%of the total eddy number,respectively.The size of the"abnormal"eddies is usually smaller than that of the"normal"eddies,with the radius only around 50 km.In the generation time aspect,they usually appear within the 0.1–0.3 interval in the normalized eddy lifespan.The survival time of CWEs(ACEs)occupies 16.3%(17.1%)of the total eddy lifespan.Based on two case studies,the intrusion of Kuroshio warm water is considered as a key mechanism for the generation of these"abnormal"eddies near the northeastern SCS.
基金supported by the National Natural Science Foundation of China (Grant Nos. 92158204, 41506001 and 42076019)a Project supported by the Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) (Grant No. 311021005)。
文摘The variations of the frontogenetic trend of a cold filament induced by the cross-filament wind and wave fields are studied by a non-hydrostatic large eddy simulation. Five cases with different strengths of wind and wave fields are studied.The results show that the intense wind and wave fields further break the symmetries of submesoscale flow fields and suppress the levels of filament frontogenesis. The changes of secondary circulation directions—that is, the conversion between the convergence and divergence of the surface cross-filament currents with the downwelling and upwelling jets in the filament center—are associated with the inertial oscillation. The filament frontogenesis and frontolysis caused by the changes of secondary circulation directions may periodically sharpen and smooth the gradient of submesoscale flow fields.The lifecycle of the cold filament may include multiple stages of filament frontogenesis and frontolysis.
基金supported by the National Natural Science Foundation of China(Nos.52172363 and 52202429)the National Key Research and Development Program of China(No.2020YFF0304103-03)the Independent Exploration of Graduate Students of Central South University(No.2019zzts268),China.
文摘In this study,an improved delayed detached eddy simulation(IDDES)method based on the shear-stress transport(SST)k-ωturbulence model has been used to investigate the underbody flow characteristics of a high-speed train operating at lower temperatures with Reynolds number Re=1.85×10^(6).The accuracy of the numerical method has been validated by wind tunnel tests.The aerodynamic drag of the train,pressure distribution on the surface of the train,the flow around the vehicle,and the wake flow are compared for four temperature values:+15℃,0℃,−15℃,and−30℃.It was found that lower operating t emperatures significantly increased the aerodynamic drag force of the train.The drag overall at low temperatures increased by 5.3%(0℃),11.0%(−15℃),and 17.4%(−30℃),respectively,relative to the drag at+15℃.In addition,the low temperature e nhances the positive and negative pressures around and on the surface of the car body,raising the peak positive and negative pressure values in areas susceptible to impingement flow and to rapid changes in flow velocity.The range of train-induced winds around the car body is significantly reduced,the distribution area of vorticity moves backwards,and the airflow velocity in the bogie cavity is significantly increased.At the same time,the temperature causes a significant velocity reduction in the wake flow.It can be seen that the temperature reduction can seriously disturb the normal operation of the train while increasing the aerodynamic drag and energy consumption,and significantly interfering with the airflow characteristics around the car body.
基金The 2022 Research Program of Sanya Yazhou Bay Science and Technology City under contract No.SKJC-2022-01-001the Project of Sanya Yazhou Bay Science and Technology City under contract No.SCKJ-JYRC-2022-47+4 种基金the National Natural Science Foundation of China under contract No.41806019the Natural Science Foundation of Hainan Province under contract No.121MS062the National Natural Science Foundation of China under contract Nos 42006008 and 41876031the National Key Research and Development Plan of China under contract No.2016YFC1401603the Research Startup Funding from Hainan Institute of Zhejiang University under contract No.HZY20210801。
文摘Using observational data from multiple satellites,we studied seasonal variations of the shape and location of the Luzon cold eddy(LCE)northwest of Luzon Island.The shape and location of the LCE have obvious seasonal variations.The LCE occurs,develops,and disappears from December to April of the next year.During this period,the shape of the LCE changed from a flat ellipse to a circular ellipse,and the change in shape can be reflected by the increase of the ellipticity of the LCE from 0.16 to 0.82.The latitude of center location of the LCE changes from 17.4°N to 19°N,and the change in latitude can reach 1.6°.Further study showed that seasonal variation of the northeast monsoon intensity leads to the change in the shape and location of the LCE.The seasonal variation of the LCE shape can significantly alter the spatial distribution of the thermal front and chlorophyll a northwest of the Luzon Island by geostrophic advection.
基金Supported by the Knowledge Innovation Program of Chinese Academy of Sciences (No. KZCX2-YW-Q11-02)the Strategic Priority Research Program of Chinese Academy of Sciences (No. XDA05090404)the National Natural Science Foundation of China (No. 41106026)
文摘Based on observed temperature data since the 1950s, long-term variability of the summer sharp thermocline in the Yellow Sea Cold Water Mass （YSCWM） and East China Sea Cold Eddy （ECSCE） areas is examined. Relationships between the thermocline and atmospheric and oceanic forcing were investigated using multiyear wind, Kuroshio discharge and air temperature data. Results show that： 1） In the YSCWM area, thermocline strength shows about 4-year and 16-year period oscillations. There is high correlation between summer thermocline strength and local atmospheric temperature in summer and the previous winter; 2） In the ECSCE area, interannual oscillation of thermocline strength with about a 4-year period （stronger in El Nifio years） is strongly correlated with that of local wind stress. A transition from weak to strong thermocline during the mid 1970s is consistent with a 1976/1977 climate shift and Kuroshio volume transport; 3） Long-term changes of the thermocline in both regions are mainly determined by deep layer water, especially on the decadal timescale. However, surface water can modify the thermocline on an interannual timescale in the YSCWM area.
