分别利用weather research and forecasting（WRF）中尺度模式中的bulk和bin微物理参数化方案,对2014年7月12日发生在华东地区的一次飑线过程进行了数值模拟。结果表明：bulk方案基本模拟出了飑线初生、发展、成熟和消亡的生命史,但与...分别利用weather research and forecasting（WRF）中尺度模式中的bulk和bin微物理参数化方案,对2014年7月12日发生在华东地区的一次飑线过程进行了数值模拟。结果表明：bulk方案基本模拟出了飑线初生、发展、成熟和消亡的生命史,但与实况存在1~2 h的延迟,且强度偏弱;而bin方案模拟的雷达回波结构松散,组织化程度较低,更类似于现状对流。从模拟的地面降水看,bin方案模拟的雨带偏窄,且强降水区偏北;而bulk方案则基本模拟出了强降水区的位置。在此基础上进一步分析了两种方案模拟的各水凝物的垂直分布,结果表明bulk方案在高层产生了大量云冰,而bin方案中雪和霰粒子数量较多。展开更多
观测和分档方案的数值模拟都证明气溶胶的谱分布特征对云滴谱的演变有直接影响继而作用于降水的发展。目前广泛使用的总体双参数云滴谱方案因为表征云滴谱的预报量不足,在凝结过程中云滴谱呈不正常的拓宽现象。因此在参数化方案中,气溶...观测和分档方案的数值模拟都证明气溶胶的谱分布特征对云滴谱的演变有直接影响继而作用于降水的发展。目前广泛使用的总体双参数云滴谱方案因为表征云滴谱的预报量不足,在凝结过程中云滴谱呈不正常的拓宽现象。因此在参数化方案中,气溶胶谱对云滴谱的影响未有明确结论。中科学院大气物理研究所(IAP)云降水物理与强风暴重点实验室(LACS)新研发的三参数方案(IAP-LACS)通过增加的预报量克服了云滴谱的拓宽问题,提高了云滴谱模拟的准确性。为了研究在参数化方案中气溶胶谱分布特征对云滴谱的影响,本文采用新方案进行WRF(Weather Research and Forecasting mode)大涡理想性试验,验证了新方案中气溶胶对数正态谱函数中数浓度、几何半径和标准差3个参量对云滴谱演变的影响。针对3个参量的敏感性试验表明新的气溶胶活化方案和三参数云滴凝结增长方案能够描述气溶胶谱对云滴谱演变的影响规律:气溶胶数浓度对云滴谱影响最显著,数浓度越高活化生成的云滴数量越多,云滴半径越小,云滴谱趋向窄谱,气溶胶数浓度低时,云滴数量少、半径大。较大的几何半径使气溶胶谱向大粒径移动,导致大云滴生成,标准差对云滴谱的影响最不显著。展开更多
Are extensions to continuum formulations for solving fluid dynamic problems in the transition-to-rarefied regimes viable alternatives to particle methods?It is well known that for increasingly rarefied flow fields,the...Are extensions to continuum formulations for solving fluid dynamic problems in the transition-to-rarefied regimes viable alternatives to particle methods?It is well known that for increasingly rarefied flow fields,the predictions from continuum formulation,such as the Navier-Stokes equations lose accuracy.These inaccuracies are attributed primarily to the linear approximations of the stress and heat flux terms in the Navier-Stokes equations.The inclusion of higher-order terms,such as Burnett or highorder moment equations,could improve the predictive capabilities of such continuum formulations,but there has been limited success in the shock structure calculations,especially for the high Mach number case.Here,after reformulating the viscosity and heat conduction coefficients appropriate for the rarefied flow regime,we will show that the Navier-Stokes-type continuum formulation may still be properly used.The equations with generalization of the dissipative coefficients based on the closed solution of the Bhatnagar-Gross-Krook(BGK)model of the Boltzmann equation,are solved using the gas-kinetic numerical scheme.This paper concentrates on the non-equilibrium shock structure calculations for both monatomic and diatomic gases.The Landau-Teller-Jeans relaxation model for the rotational energy is used to evaluate the quantitative difference between the translational and rotational temperatures inside the shock layer.Variations of shear stress,heat flux,temperatures,and densities in the internal structure of the shock waves are compared with,(a)existing theoretical solutions of the Boltzmann solution,(b)existing numerical predictions of the direct simulation Monte Carlo(DSMC)method,and(c)available experimental measurements.The present continuum formulation for calculating the shock structures for monatomic and diatomic gases in the Mach number range of 1.2 to 12.9 is found to be satisfactory.展开更多
基金supported by the National Basic Research Program of China(973 Program)[Grant 2014CB441403]the National Natural Science Foundation of China [Grants41275147]+1 种基金the National Key Research and Development Program of China [2016YFC0209000]Ningxia scientific supporting program [Grants 2015KJHM31]
文摘分别利用weather research and forecasting（WRF）中尺度模式中的bulk和bin微物理参数化方案,对2014年7月12日发生在华东地区的一次飑线过程进行了数值模拟。结果表明：bulk方案基本模拟出了飑线初生、发展、成熟和消亡的生命史,但与实况存在1~2 h的延迟,且强度偏弱;而bin方案模拟的雷达回波结构松散,组织化程度较低,更类似于现状对流。从模拟的地面降水看,bin方案模拟的雨带偏窄,且强降水区偏北;而bulk方案则基本模拟出了强降水区的位置。在此基础上进一步分析了两种方案模拟的各水凝物的垂直分布,结果表明bulk方案在高层产生了大量云冰,而bin方案中雪和霰粒子数量较多。
文摘观测和分档方案的数值模拟都证明气溶胶的谱分布特征对云滴谱的演变有直接影响继而作用于降水的发展。目前广泛使用的总体双参数云滴谱方案因为表征云滴谱的预报量不足,在凝结过程中云滴谱呈不正常的拓宽现象。因此在参数化方案中,气溶胶谱对云滴谱的影响未有明确结论。中科学院大气物理研究所(IAP)云降水物理与强风暴重点实验室(LACS)新研发的三参数方案(IAP-LACS)通过增加的预报量克服了云滴谱的拓宽问题,提高了云滴谱模拟的准确性。为了研究在参数化方案中气溶胶谱分布特征对云滴谱的影响,本文采用新方案进行WRF(Weather Research and Forecasting mode)大涡理想性试验,验证了新方案中气溶胶对数正态谱函数中数浓度、几何半径和标准差3个参量对云滴谱演变的影响。针对3个参量的敏感性试验表明新的气溶胶活化方案和三参数云滴凝结增长方案能够描述气溶胶谱对云滴谱演变的影响规律:气溶胶数浓度对云滴谱影响最显著,数浓度越高活化生成的云滴数量越多,云滴半径越小,云滴谱趋向窄谱,气溶胶数浓度低时,云滴数量少、半径大。较大的几何半径使气溶胶谱向大粒径移动,导致大云滴生成,标准差对云滴谱的影响最不显著。
文摘Are extensions to continuum formulations for solving fluid dynamic problems in the transition-to-rarefied regimes viable alternatives to particle methods?It is well known that for increasingly rarefied flow fields,the predictions from continuum formulation,such as the Navier-Stokes equations lose accuracy.These inaccuracies are attributed primarily to the linear approximations of the stress and heat flux terms in the Navier-Stokes equations.The inclusion of higher-order terms,such as Burnett or highorder moment equations,could improve the predictive capabilities of such continuum formulations,but there has been limited success in the shock structure calculations,especially for the high Mach number case.Here,after reformulating the viscosity and heat conduction coefficients appropriate for the rarefied flow regime,we will show that the Navier-Stokes-type continuum formulation may still be properly used.The equations with generalization of the dissipative coefficients based on the closed solution of the Bhatnagar-Gross-Krook(BGK)model of the Boltzmann equation,are solved using the gas-kinetic numerical scheme.This paper concentrates on the non-equilibrium shock structure calculations for both monatomic and diatomic gases.The Landau-Teller-Jeans relaxation model for the rotational energy is used to evaluate the quantitative difference between the translational and rotational temperatures inside the shock layer.Variations of shear stress,heat flux,temperatures,and densities in the internal structure of the shock waves are compared with,(a)existing theoretical solutions of the Boltzmann solution,(b)existing numerical predictions of the direct simulation Monte Carlo(DSMC)method,and(c)available experimental measurements.The present continuum formulation for calculating the shock structures for monatomic and diatomic gases in the Mach number range of 1.2 to 12.9 is found to be satisfactory.
