The air traffic management automation imposes stringent requirements on the weather models,in such a way that they should be able to provide reliable short-time forecasts in digital formats in almost real time.The atm...The air traffic management automation imposes stringent requirements on the weather models,in such a way that they should be able to provide reliable short-time forecasts in digital formats in almost real time.The atmospheric boundary layer is one of the regions where aircraft operation and coordination are critical and therefore atmospheric model performance is also vital.This paper presents conventional and innovative techniques to improve the accuracy in the forecasting of winds in the lower atmospheric layer,proposing mechanisms to develop better models including deterministic and stochastic simulations.Accuracy is improved by optimizing the grid,assimilating observations in cycling simulations and managing a number of ensemble members.An operationdriven post-processing stage helps to incorporate detailed terrain definitions and real-time observations without re-running the model.The improvements are checked against mesoscale weather simulations at different scales and a dedicated flight campaign.The results show good performance of the model without sensitively increasing the required throughput.展开更多
A LES model is proposed to predict the dispersion of particles in the atmosphere in the context of Chemical,Biological,Radiological and Nuclear(CBRN)applications.The code relies on the Finite Element Method(FEM)for bo...A LES model is proposed to predict the dispersion of particles in the atmosphere in the context of Chemical,Biological,Radiological and Nuclear(CBRN)applications.The code relies on the Finite Element Method(FEM)for both the fluid and the dispersed solid phases.Starting from the Navier-Stokes equations and a general description of the FEM strategy,the Streamline Upwind Petrov-Galerkin(SUPG)method is formulated putting some emphasis on the related assembly matrix and stabilization coefficients.Then,the Variational Multiscale Method(VMS)is presented together with a detailed illustration of its algorithm and hierarchy of computational steps.It is demonstrated that the VMS can be considered as a more general version of the SUPG method.The final part of the work is used to assess the reliability of the implemented predictor/multicorrector solution strategy.展开更多
Atmospheric boundary layer(ABL)flow over multiple-hill terrain is studied numerically.The spectral vanishing viscosity(SVV)method is employed for implicit large eddy simulation(ILES).ABL flow over one hill,double hill...Atmospheric boundary layer(ABL)flow over multiple-hill terrain is studied numerically.The spectral vanishing viscosity(SVV)method is employed for implicit large eddy simulation(ILES).ABL flow over one hill,double hills,and three hills are presented in detail.The instantaneous three-dimensional vortex structures,mean velocity,and turbulence intensity in mainstream and vertical directions around the hills are investigated to reveal the main properties of this turbulent flow.During the flow evolution downstream,the Kelvin-Helmholtz vortex,braid vortex,and hairpin vortex are observed sequentially.The turbulence intensity is enhanced around crests and reduced in the recirculation zones.The present results are helpful for understanding the impact of topography on the turbulent flow.The findings can be useful in various fields,such as wind energy,air pollution,and weather forecasting.展开更多
In this paper, the characteristics of the atmospheric boundary layer(ABL) vertical structure over the North China Plain(NCP) during a comprehensive observation experiment conducted during 15–21 December 2018 were inv...In this paper, the characteristics of the atmospheric boundary layer(ABL) vertical structure over the North China Plain(NCP) during a comprehensive observation experiment conducted during 15–21 December 2018 were investigated. Observational data were obtained with a large tethered balloon, Doppler wind lidar, and ground-level instruments. The maximum concentration of PM_(2.5) exceeded 200 μg m^(-3), and the ratio of PM_(2.5)/PM_(10) was approximately 0.4(its maxi-mum was approximately 0.8) during the whole observation period, indicating the explosive growth of dominant fine-mode aerosols in the winter heating season. Elevated concentrations of pollutants decreased the solar irradiance received by the ground, resulting in lower temperature at ground level. Our results illustrate three distinct types of vertical profiles: Type 1(convective state)—the concentration of PM_(2.5) decreased nearly linearly with increase of the height below approximately 600 m;Type 2(stable state)—the PM_(2.5) concentration sharply decreased from the ground to approximately 200 m;and Type 3(multilayer structure)—some pollutants were suspended aloft in the upper air layer. Diurnal evolution of the vertical profiles of PM_(2.5) and their relationship with the changes in meteorological factors were identified. From daytime to nighttime, the vertical profiles evolved from Type 1 to Type 2 or Type 3. All the 33 vertical PM_(2.5) profiles that we obtained showed a strong relationship with elements of the ABL structure, such as the distributions of winds, the inversion layer, and turbulence activities. A light-wind layer and weak turbulence activity, especially within the inversion layer, contributed greatly to the accumulation of pollutants.Vertical PM_(2.5) concentration patterns were also greatly affected by local ground-level emission sources and regional transport processes.展开更多
基金funded by Boeing Research&Technology Europe during 2019。
文摘The air traffic management automation imposes stringent requirements on the weather models,in such a way that they should be able to provide reliable short-time forecasts in digital formats in almost real time.The atmospheric boundary layer is one of the regions where aircraft operation and coordination are critical and therefore atmospheric model performance is also vital.This paper presents conventional and innovative techniques to improve the accuracy in the forecasting of winds in the lower atmospheric layer,proposing mechanisms to develop better models including deterministic and stochastic simulations.Accuracy is improved by optimizing the grid,assimilating observations in cycling simulations and managing a number of ensemble members.An operationdriven post-processing stage helps to incorporate detailed terrain definitions and real-time observations without re-running the model.The improvements are checked against mesoscale weather simulations at different scales and a dedicated flight campaign.The results show good performance of the model without sensitively increasing the required throughput.
基金The authors received the funding of the Royal Higher Institute for Defence(MSP16-06).
文摘A LES model is proposed to predict the dispersion of particles in the atmosphere in the context of Chemical,Biological,Radiological and Nuclear(CBRN)applications.The code relies on the Finite Element Method(FEM)for both the fluid and the dispersed solid phases.Starting from the Navier-Stokes equations and a general description of the FEM strategy,the Streamline Upwind Petrov-Galerkin(SUPG)method is formulated putting some emphasis on the related assembly matrix and stabilization coefficients.Then,the Variational Multiscale Method(VMS)is presented together with a detailed illustration of its algorithm and hierarchy of computational steps.It is demonstrated that the VMS can be considered as a more general version of the SUPG method.The final part of the work is used to assess the reliability of the implemented predictor/multicorrector solution strategy.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12372220,12372219,11972220,12072185,91952102 and 12032016).
文摘Atmospheric boundary layer(ABL)flow over multiple-hill terrain is studied numerically.The spectral vanishing viscosity(SVV)method is employed for implicit large eddy simulation(ILES).ABL flow over one hill,double hills,and three hills are presented in detail.The instantaneous three-dimensional vortex structures,mean velocity,and turbulence intensity in mainstream and vertical directions around the hills are investigated to reveal the main properties of this turbulent flow.During the flow evolution downstream,the Kelvin-Helmholtz vortex,braid vortex,and hairpin vortex are observed sequentially.The turbulence intensity is enhanced around crests and reduced in the recirculation zones.The present results are helpful for understanding the impact of topography on the turbulent flow.The findings can be useful in various fields,such as wind energy,air pollution,and weather forecasting.
基金Supported by the National Key Research and Development Program of China (2017YFC0209605)National Natural Science Foundation of China (41975108)General Financial Grant from the China Postdoctoral Science Foundation (2020M670420)。
文摘In this paper, the characteristics of the atmospheric boundary layer(ABL) vertical structure over the North China Plain(NCP) during a comprehensive observation experiment conducted during 15–21 December 2018 were investigated. Observational data were obtained with a large tethered balloon, Doppler wind lidar, and ground-level instruments. The maximum concentration of PM_(2.5) exceeded 200 μg m^(-3), and the ratio of PM_(2.5)/PM_(10) was approximately 0.4(its maxi-mum was approximately 0.8) during the whole observation period, indicating the explosive growth of dominant fine-mode aerosols in the winter heating season. Elevated concentrations of pollutants decreased the solar irradiance received by the ground, resulting in lower temperature at ground level. Our results illustrate three distinct types of vertical profiles: Type 1(convective state)—the concentration of PM_(2.5) decreased nearly linearly with increase of the height below approximately 600 m;Type 2(stable state)—the PM_(2.5) concentration sharply decreased from the ground to approximately 200 m;and Type 3(multilayer structure)—some pollutants were suspended aloft in the upper air layer. Diurnal evolution of the vertical profiles of PM_(2.5) and their relationship with the changes in meteorological factors were identified. From daytime to nighttime, the vertical profiles evolved from Type 1 to Type 2 or Type 3. All the 33 vertical PM_(2.5) profiles that we obtained showed a strong relationship with elements of the ABL structure, such as the distributions of winds, the inversion layer, and turbulence activities. A light-wind layer and weak turbulence activity, especially within the inversion layer, contributed greatly to the accumulation of pollutants.Vertical PM_(2.5) concentration patterns were also greatly affected by local ground-level emission sources and regional transport processes.
