Vertical cumulus momentum transport is an important physical process in the tropical atmosphere and plays a key role in the evolution of the tropical atmospheric system. This paper focuses on the impact of the vertica...Vertical cumulus momentum transport is an important physical process in the tropical atmosphere and plays a key role in the evolution of the tropical atmospheric system. This paper focuses on the impact of the vertical cumulus momentum transport on Madden-Julian Oscillation （MJO） simulation in two global climate models （GCMs）. The Tiedtke cumulus parameterization scheme is applied to both GCMs [CAM2 and Spectral Atmospheric general circulation Model of LASG/IAP （SAMIL）]. It is found that the MJO simulation ability might be influenced by the vertical cumulus momentum transport through the cumulus parameterization scheme. However, the use of vertical momentum transport in different models provides different results. In order to improve model＇s MJO simulation ability, we must introduce vertical cumulus momentum transport in a more reasonable way into models. Furthermore, the coherence of the parameterization and the underlying model also need to be considered.展开更多
The Weather Research and Forecasting (WRF) model was used to investigate the role of downward momentum transport in the formation of severe surface winds for a squall line on 3-4 June 2009 across regions of the Henan ...The Weather Research and Forecasting (WRF) model was used to investigate the role of downward momentum transport in the formation of severe surface winds for a squall line on 3-4 June 2009 across regions of the Henan and Shandong Provinces of China. The results show that there was a strong westerly jet belt with a wind speed greater than 30 m s 1 and a thickness of 5 km at an altitude of 11-16 km. The jet belt was accelerated, and it descended while the squall line convective system occurred. It was found that the appearance of strong negative perturbation pressure accompanied by the squall line caused the acceleration of the upper-level westerly jet and increased the horizontal wind speed by a maximum of 18%. Meanwhile, the negative buoyancy due to the loading, melting, and evaporation of cloud hydrometeors induced the downward momentum transport from the upper levels. The downward momentum transport contributed approximately 70% and the surface cold pool 30% to the formation of severe surface winds.展开更多
This paper focuses on the impacts of convective momentum transport(CMT) on simulations of the tropical intraseasonal oscillation(TIO) in SAMIL. Two sets of experiments are performed, which give different reality of th...This paper focuses on the impacts of convective momentum transport(CMT) on simulations of the tropical intraseasonal oscillation(TIO) in SAMIL. Two sets of experiments are performed, which give different reality of the Madden-Julian Oscillation(MJO). The Tiedtke cumulus parameterization scheme is used for all experiments. It is found that simulations of the TIO can be influenced by CMT, and the impacts on the simulated TIO depend on the model capability in simulating the MJO. CMT tends to have large influences to the model that can simulate the eastward propagation of the MJO. CMT can further influence the long-term mean of zonal wind and its vertical shear. Zonal wind suffers from easterlies biases at low level and westerlies biases at upper level when CMT is introduced. Such easterlies biases at low level reduce the reality of the simulated tropical intraseasonal oscillation. When CMT is introduced in the model, MJO signals disappear but the model's mean state improves. Therefore, a more appropriate way is needed to introduce CMT to the model to balance the simulated mean state and TIO signals.展开更多
The classical Navier–Stokes equation(NSE)is the fundamental partial differential equation that describes the flow of fluids,but in certain cases,like high local density and temperature gradient,it is inconsistent wit...The classical Navier–Stokes equation(NSE)is the fundamental partial differential equation that describes the flow of fluids,but in certain cases,like high local density and temperature gradient,it is inconsistent with the experimental results.Some extended Navier–Stokes equations with diffusion terms taken into consideration have been proposed.However,a consensus conclusion on the specific expression of the additional diffusion term has not been reached in the academic circle.The models adopt the form of the generalized Newtonian constitutive relation by substituting the convection velocity with a new term,or by using some analogy.In this study,a new constitutive relation for momentum transport and a momentum balance equation are obtained based on the molecular kinetic theory.The new constitutive relation preserves the symmetry of the deviation stress,and the momentum balance equation satisfies Galilean invariance.The results show that for Poiseuille flow in a circular micro-tube,self-diffusion in micro-flow needs considering even if the local density gradient is very low.展开更多
Ⅰ. INTRODUCTIONIt is very well known from the observations that some atmospheric motions are accompanied by jets in the boundary layer, for example, breezes and circulations in the mountain valleys (Gutman, 1969); no...Ⅰ. INTRODUCTIONIt is very well known from the observations that some atmospheric motions are accompanied by jets in the boundary layer, for example, breezes and circulations in the mountain valleys (Gutman, 1969); nocturnal increasing of wind (Byzova et al., 1989); cross-equatorial flow during the summer Indian monsoon (Das, 1986) and others. One of the important questions concerning a mathematical modelling of such motions is the problem of the turbulent closure of the equations set which describes the jet dynamics. It is still popular to use for the momentum turbulent flow (u＇w＇) a closure, based within the framework of K-theory on the Boussinesq hypothesis展开更多
Based on NCEP reanalysis data,EDAS data and ground observation data,the causes of a strong sandstorm process in Ulanqab City from March 14 to 15,2021 were analyzed.The analysis shows that"3.15"sandstorm,a sa...Based on NCEP reanalysis data,EDAS data and ground observation data,the causes of a strong sandstorm process in Ulanqab City from March 14 to 15,2021 were analyzed.The analysis shows that"3.15"sandstorm,a sandstorm process accompanied by northwest gale behind the front,was caused by strong cold air in the north.In the early stage,the Mongolian cyclone resulted in the increase of temperature and decrease of pressure on the ground.When a strong surface cold high pressure at the rear of the cyclone invaded the city,a strong pressure gradient between high and low pressure provided dynamic conditions for the sandstorm outbreak.The transit of the surface cold front was the sign of the sandstorm outbreak,and the downward transmission of momentum at high altitudes increased the wind speed near the surface.展开更多
The study of large-scale atmospheric turbulence and transport processes is of vital importance in the general circulation of the atmosphere. The governing equations of the power and cross-spectra for the atmospheric m...The study of large-scale atmospheric turbulence and transport processes is of vital importance in the general circulation of the atmosphere. The governing equations of the power and cross-spectra for the atmospheric motion and transports in the domain of wave number frequency space have been derived. The contributions of the nonlinear interactions of the atmospheric waves in velocity and temperature fields to the conversion of kinetic and potential energies and to the meridional transports of angular momentum and sensible heat in the atmosphere have been discussed.展开更多
基金supported by the National Natural Science Foundation of China under (Grant No. 40575027)
文摘Vertical cumulus momentum transport is an important physical process in the tropical atmosphere and plays a key role in the evolution of the tropical atmospheric system. This paper focuses on the impact of the vertical cumulus momentum transport on Madden-Julian Oscillation （MJO） simulation in two global climate models （GCMs）. The Tiedtke cumulus parameterization scheme is applied to both GCMs [CAM2 and Spectral Atmospheric general circulation Model of LASG/IAP （SAMIL）]. It is found that the MJO simulation ability might be influenced by the vertical cumulus momentum transport through the cumulus parameterization scheme. However, the use of vertical momentum transport in different models provides different results. In order to improve model＇s MJO simulation ability, we must introduce vertical cumulus momentum transport in a more reasonable way into models. Furthermore, the coherence of the parameterization and the underlying model also need to be considered.
基金supported by the National Meteorology Public Welfare Industry Research Project(GYHY200806001)the National Science and Technology Support Program (2006BAC12B03)
文摘The Weather Research and Forecasting (WRF) model was used to investigate the role of downward momentum transport in the formation of severe surface winds for a squall line on 3-4 June 2009 across regions of the Henan and Shandong Provinces of China. The results show that there was a strong westerly jet belt with a wind speed greater than 30 m s 1 and a thickness of 5 km at an altitude of 11-16 km. The jet belt was accelerated, and it descended while the squall line convective system occurred. It was found that the appearance of strong negative perturbation pressure accompanied by the squall line caused the acceleration of the upper-level westerly jet and increased the horizontal wind speed by a maximum of 18%. Meanwhile, the negative buoyancy due to the loading, melting, and evaporation of cloud hydrometeors induced the downward momentum transport from the upper levels. The downward momentum transport contributed approximately 70% and the surface cold pool 30% to the formation of severe surface winds.
基金sponsored by the Joint Project of Natural Science Foundation of China and Yunnan Province (U0833602)
文摘This paper focuses on the impacts of convective momentum transport(CMT) on simulations of the tropical intraseasonal oscillation(TIO) in SAMIL. Two sets of experiments are performed, which give different reality of the Madden-Julian Oscillation(MJO). The Tiedtke cumulus parameterization scheme is used for all experiments. It is found that simulations of the TIO can be influenced by CMT, and the impacts on the simulated TIO depend on the model capability in simulating the MJO. CMT tends to have large influences to the model that can simulate the eastward propagation of the MJO. CMT can further influence the long-term mean of zonal wind and its vertical shear. Zonal wind suffers from easterlies biases at low level and westerlies biases at upper level when CMT is introduced. Such easterlies biases at low level reduce the reality of the simulated tropical intraseasonal oscillation. When CMT is introduced in the model, MJO signals disappear but the model's mean state improves. Therefore, a more appropriate way is needed to introduce CMT to the model to balance the simulated mean state and TIO signals.
基金Project supported by the National Natural Science Foundation of China–Outstanding Youth Foundation(Grant No.51522903)the National Natural Science Foundation of China(Grant Nos.11602276 and 51479094)the Fund from the Key Laboratory for Mechanics in Fluid Solid Coupling Systems of the Chinese Academy of Sciences。
文摘The classical Navier–Stokes equation(NSE)is the fundamental partial differential equation that describes the flow of fluids,but in certain cases,like high local density and temperature gradient,it is inconsistent with the experimental results.Some extended Navier–Stokes equations with diffusion terms taken into consideration have been proposed.However,a consensus conclusion on the specific expression of the additional diffusion term has not been reached in the academic circle.The models adopt the form of the generalized Newtonian constitutive relation by substituting the convection velocity with a new term,or by using some analogy.In this study,a new constitutive relation for momentum transport and a momentum balance equation are obtained based on the molecular kinetic theory.The new constitutive relation preserves the symmetry of the deviation stress,and the momentum balance equation satisfies Galilean invariance.The results show that for Poiseuille flow in a circular micro-tube,self-diffusion in micro-flow needs considering even if the local density gradient is very low.
文摘Ⅰ. INTRODUCTIONIt is very well known from the observations that some atmospheric motions are accompanied by jets in the boundary layer, for example, breezes and circulations in the mountain valleys (Gutman, 1969); nocturnal increasing of wind (Byzova et al., 1989); cross-equatorial flow during the summer Indian monsoon (Das, 1986) and others. One of the important questions concerning a mathematical modelling of such motions is the problem of the turbulent closure of the equations set which describes the jet dynamics. It is still popular to use for the momentum turbulent flow (u＇w＇) a closure, based within the framework of K-theory on the Boussinesq hypothesis
文摘Based on NCEP reanalysis data,EDAS data and ground observation data,the causes of a strong sandstorm process in Ulanqab City from March 14 to 15,2021 were analyzed.The analysis shows that"3.15"sandstorm,a sandstorm process accompanied by northwest gale behind the front,was caused by strong cold air in the north.In the early stage,the Mongolian cyclone resulted in the increase of temperature and decrease of pressure on the ground.When a strong surface cold high pressure at the rear of the cyclone invaded the city,a strong pressure gradient between high and low pressure provided dynamic conditions for the sandstorm outbreak.The transit of the surface cold front was the sign of the sandstorm outbreak,and the downward transmission of momentum at high altitudes increased the wind speed near the surface.
文摘The study of large-scale atmospheric turbulence and transport processes is of vital importance in the general circulation of the atmosphere. The governing equations of the power and cross-spectra for the atmospheric motion and transports in the domain of wave number frequency space have been derived. The contributions of the nonlinear interactions of the atmospheric waves in velocity and temperature fields to the conversion of kinetic and potential energies and to the meridional transports of angular momentum and sensible heat in the atmosphere have been discussed.
