中文摘要：

如何更好地模拟水物质的空间分布和小尺度变化,对于数值天气预报效果的改进,特别是对于更好地模拟降水过程,具有重要的意义。计算机的飞速发展使数值模式的分辨率不断提高,云的显式计算成为可能,这样就要求水物质在平流的过程中必须要做到高精度、守恒、保形。水物质场是正定标量的场,具有空间和时间变化幅度大、存在强梯度甚至不连续的特点,水物质场的合理模拟一直是数值预报中的一个难题。GRAPES模式中的标量平流方案采用PRM分段有理函数方法,比较好地解决了该半拉格朗日模式中水物质平流的高精度、守恒、保形问题,但是当有凝结潜热发生时,由于半拉格朗日平流方案求解上游点时的插值,在云边缘区域会造成虚假的云水,进而导致不合理的相变过程。为了解决以上问题,本研究在GRAPES模式中PRM平流方案的基础上,加入了非线性半拉格朗日相变潜热的修正方案,旨在改进GRAPES模式对水物质平流问题的模拟,提高降水的预报效果。该研究通过理想试验,验证了非线性半拉格朗日相变修正方案可以有效地限制云边缘由于半拉格朗日平流方案插值产生的虚假相变;然后将该方案加入GRAPES模式的PRM水物质平流方案中,通过实际个例模拟验证了加入非线性半拉格朗日方案以后,模式可以更好地模拟水物质的平流过程,且对云中热力场及水物质分布地模拟更加合理,同时预报出的雨带中心区与实况更加符合。

英文摘要：

To better simulate the spatial characteristics and small-scale variations of water substances in numerical models is of crucial importance for improving the numerical weather prediction models,especially for precipitation forecast.With the rapid development of work-station,the resolution of numerical model is increasingly sophisticated,it is possible to calculate the cloud explicitly,so it bring forward a higher request for the computation of water substance advection,it must be high-order accuracy,conservation,and shape preserving.The water substance field is positive definite scalar field,with the characteristics of large variations in space and time,strong gradients and not even continuous,the simulation of water substance is always a problem in numerical prediction.The piece-wise rational method is adopted as the scalar advection scheme in the GRAPES model,and this advection scheme is of high-order accuracy,conservation,and shape preserving in solving the water substance advection.However,unphysical phase change may occured over the computational areas of cloud boundary when coupling the advection scheme with precipitation processes.Such unreasonable features result from the semi-Lagrangian interpolation of cloud water around the cloud boundary and the consequent nonlinear interaction with physical processes.To mitigate this problem,a physical limitation method NLSL scheme in PRM scalar advection scheme in the GRAPES model was introduced,and tries to improve the simulation of cloud substances and precipitation forecast. Through one and two dimensional idealized experiments,the feasibility and effect of the physical limitation method in scalar advection scheme are verified.Furthermore,by implementing this scheme into PRM advection scheme of high-resolution GRAPES meso-scale model,both case study and continuous forecast experiment show that the simulated distribution of cloud water and thermal structures around the cloud boundary and within the cloud is improved to a certain extent.And,the forecast location of