The variations of the frontogenetic activity of cold filament driven by the different angle(θ=0°,22.5°,45°,67.5°,and 90°)of the wind and wave fields and the filament axis are studied by non h...The variations of the frontogenetic activity of cold filament driven by the different angle(θ=0°,22.5°,45°,67.5°,and 90°)of the wind and wave fields and the filament axis are studied by non hydrostatic large eddy simulation.Conversion between the frontogenesis and frontolysis of cold filament were created by the chang in the direction of secondary circulations.The changes in the direction of secondary circulation are induced by the Coriolis Effect regardless of wind direction and wave fields.The destructive action of the wind and wave fields on symmetry of the submesoscale flow fields becomes weak as the angle increases.The secondary downwelling jet induced by Stokes shear force is gradually close to that associated with secondary circulations as the angle changes fromθ=0°to 45°and then the downwelling jet is only created by secondary circulations forθ=67.5°and 90°.The frontogenetic intensity of cold filament may be impacted by the angle of the wind and wave fields and the filament axis.The reason is that firstly the odd-symmetry of secondary circulations enhances with the angle increasing,and secondary the secondary downwelling jet created the Stokes shear force gradually weakens and then disappears with the angle increasing.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
The frontogenetic processes of a submesoscale cold filament driven by the thermal convection turbulence are studied by a non-hydrostatic large eddy simulation.The results show that the periodic changes in the directio...The frontogenetic processes of a submesoscale cold filament driven by the thermal convection turbulence are studied by a non-hydrostatic large eddy simulation.The results show that the periodic changes in the direction of the cross-filament secondary circulations are induced by the inertial oscillation.The change in the direction of the secondary circulations induces the enhancement and reduction of the horizontal temperature gradient during the former and later inertial period,which indicates that the frontogenetical processes of the cold filament include both of frontogenesis and frontolysis.The structure of the cold filament may be broken and restored by frontogenesis and frontolysis,respectively.The magnitude of the down-filament currents has a periodic variation,while its direction is unchanged with time.The coupling effect of the turbulent mixing and the frontogenesis and frontolysis gradually weakens the temperature gradient of the cold filament with time,which reduces frontogenetical intensity and enlarges the width of cold filament.展开更多
Based on the four-times-daily ERA-Interim data with the resolution of 0.75°×0.75°,the structure and evolution characteristics of a transverse shear line(TSL)over the Qinghai-Tibet Plateau in April 2017 ...Based on the four-times-daily ERA-Interim data with the resolution of 0.75°×0.75°,the structure and evolution characteristics of a transverse shear line(TSL)over the Qinghai-Tibet Plateau in April 2017 were analyzed,and the influence mechanism of the frontogenesis and frontolysis caused by the upper-level jet on its evolution was also investigated.The results show that the TSL was mainly located near the axis of the positive vorticity zone,which was a low-value area of the wind speed.It was a shallow baroclinic system with weak ascending motion.In the vertical direction,the TSL extended to the lowest height at 00:00 and the highest at 18:00.In the horizontal direction,the length of the TSL in the east-west direction was relatively shorter during 00:00-06:00 and relatively longer during 12:00-18:00.Besides,the position of the TSL was slightly northward at 06:00 and slightly southward at 18:00.The moving direction of the TSL was generally consistent with that of the upper-level jet.In addition,the vertical stretching height of the TSL and the near-surface wind speed were positively correlated with the intensity of the upper-level jet.The calculation by frontogenesis function indicates that the frontogenesis(frontolysis)was conducive to the formation(weakening)and strengthening(dissipation)of the TSL.The horizontal deformation-induced and diabatic heating-induced frontogenesis were favorable for the formation of the TSL,while the middle-level horizontal convergence-induced and diabatic heating-induced frontogenesis were beneficial to its maintenance.Besides,the moving direction and baroclinicity of the TSL over the Qinghai-Tibet Plateau were determined by the horizontal deformation-induced frontogenesis.In the frontogenesis function,the terms of horizontal deformation and horizontal convergence together determined the position of the TSL,and the diabatic heating term was conducive to the upward extension of the TSL.展开更多
Geostrophic adjustment and frontogenesis are examined by means of the 2-D ARPS model. The simulation shows that.without the large-scale forcing,both the frontogenesis and frontolysis are observed during the geostrophi...Geostrophic adjustment and frontogenesis are examined by means of the 2-D ARPS model. The simulation shows that.without the large-scale forcing,both the frontogenesis and frontolysis are observed during the geostrophic adjustment process and the intensity of the front oscillates in the case of no discontinuity.The convergence (divergence) induced by the secondary circulation is the most important factor for frontogenesis (frontolysis) at the top and bottom boundaries.The amplitude and period of oscillation are dependent on the initial atmospheric stratification and the Coriolis frequency,and they are related to the inertio-gravity wave.展开更多
基金Supported by the National Natural Science Foundation of China (Nos.92158204,42176027,41876017,42076026)the project supported by Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(No.SML2023SP240)+1 种基金the Open Research Project Program of the State Key Laboratory of Internet of Things for Smart City (University of Macao)(No.SKL-IoTSC (UM)-2021-2023/ORPF/A20/2022)the Postdoctoral Innovation Practice Base of Hezhu University and the Guangxi Yuchai New Energy Co.,Ltd.。
文摘The variations of the frontogenetic activity of cold filament driven by the different angle(θ=0°,22.5°,45°,67.5°,and 90°)of the wind and wave fields and the filament axis are studied by non hydrostatic large eddy simulation.Conversion between the frontogenesis and frontolysis of cold filament were created by the chang in the direction of secondary circulations.The changes in the direction of secondary circulation are induced by the Coriolis Effect regardless of wind direction and wave fields.The destructive action of the wind and wave fields on symmetry of the submesoscale flow fields becomes weak as the angle increases.The secondary downwelling jet induced by Stokes shear force is gradually close to that associated with secondary circulations as the angle changes fromθ=0°to 45°and then the downwelling jet is only created by secondary circulations forθ=67.5°and 90°.The frontogenetic intensity of cold filament may be impacted by the angle of the wind and wave fields and the filament axis.The reason is that firstly the odd-symmetry of secondary circulations enhances with the angle increasing,and secondary the secondary downwelling jet created the Stokes shear force gradually weakens and then disappears with the angle increasing.
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The National Key Research and Development Program of China under contract No.2022YFC3103400the National Natural Science Foundation of China under contract Nos 42076019 and 42076026the Project supported by Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)under contract No.SML2023SP240.
文摘The frontogenetic processes of a submesoscale cold filament driven by the thermal convection turbulence are studied by a non-hydrostatic large eddy simulation.The results show that the periodic changes in the direction of the cross-filament secondary circulations are induced by the inertial oscillation.The change in the direction of the secondary circulations induces the enhancement and reduction of the horizontal temperature gradient during the former and later inertial period,which indicates that the frontogenetical processes of the cold filament include both of frontogenesis and frontolysis.The structure of the cold filament may be broken and restored by frontogenesis and frontolysis,respectively.The magnitude of the down-filament currents has a periodic variation,while its direction is unchanged with time.The coupling effect of the turbulent mixing and the frontogenesis and frontolysis gradually weakens the temperature gradient of the cold filament with time,which reduces frontogenetical intensity and enlarges the width of cold filament.
基金Supported by Project of Qinghai Science and Technology Department(2020-ZJ-739)Project of Key Laboratory for Disaster Prevention and Mitigation of Qinghai Province(QFZ-2021-Z04)Key Project of Qinghai Provincial Meteorological Bureau(QXZ2020-03)
文摘Based on the four-times-daily ERA-Interim data with the resolution of 0.75°×0.75°,the structure and evolution characteristics of a transverse shear line(TSL)over the Qinghai-Tibet Plateau in April 2017 were analyzed,and the influence mechanism of the frontogenesis and frontolysis caused by the upper-level jet on its evolution was also investigated.The results show that the TSL was mainly located near the axis of the positive vorticity zone,which was a low-value area of the wind speed.It was a shallow baroclinic system with weak ascending motion.In the vertical direction,the TSL extended to the lowest height at 00:00 and the highest at 18:00.In the horizontal direction,the length of the TSL in the east-west direction was relatively shorter during 00:00-06:00 and relatively longer during 12:00-18:00.Besides,the position of the TSL was slightly northward at 06:00 and slightly southward at 18:00.The moving direction of the TSL was generally consistent with that of the upper-level jet.In addition,the vertical stretching height of the TSL and the near-surface wind speed were positively correlated with the intensity of the upper-level jet.The calculation by frontogenesis function indicates that the frontogenesis(frontolysis)was conducive to the formation(weakening)and strengthening(dissipation)of the TSL.The horizontal deformation-induced and diabatic heating-induced frontogenesis were favorable for the formation of the TSL,while the middle-level horizontal convergence-induced and diabatic heating-induced frontogenesis were beneficial to its maintenance.Besides,the moving direction and baroclinicity of the TSL over the Qinghai-Tibet Plateau were determined by the horizontal deformation-induced frontogenesis.In the frontogenesis function,the terms of horizontal deformation and horizontal convergence together determined the position of the TSL,and the diabatic heating term was conducive to the upward extension of the TSL.
基金This research was supported by the National Natural Science Foundation of China under Grants:49675259 and 49735180The National Key Basic Research Development Program:CHERES
文摘Geostrophic adjustment and frontogenesis are examined by means of the 2-D ARPS model. The simulation shows that.without the large-scale forcing,both the frontogenesis and frontolysis are observed during the geostrophic adjustment process and the intensity of the front oscillates in the case of no discontinuity.The convergence (divergence) induced by the secondary circulation is the most important factor for frontogenesis (frontolysis) at the top and bottom boundaries.The amplitude and period of oscillation are dependent on the initial atmospheric stratification and the Coriolis frequency,and they are related to the inertio-gravity wave.
