中文摘要：

地形追随坐标系下的动力学方程组通常都要引入参考大气的概念来减少气压梯度力的计算误差。参考大气的一般取法是满足静止和静力平衡关系，实际大气被看成在参考大气上的偏差。实际大气与参考大气越接近，它们之间的偏差就越小，计算就越精确。参考大气的取法一般有等温大气、定常温度廓线、初始资料进行水平平均的垂直温度廓线等。本文在一个非静力的中尺度模式中选取经过水平平均的初始温度场的垂直廓线构造模式的参考大气廓线。但是初始资料在三维空间是离散的，这里根据三次样条函数的分段连续光滑的性质，构造了随起报时间不同而不同的，只随高度变化的解析形式的参考大气廓线。构造的参考大气廓线完全满足静力平衡关系，方程中的静力平衡部分可以得到最大限度地扣除。试验表明,与等温大气相比,这种根据初始状态选取的参考大气和实际资料更接近，在大地形附近气压梯度力的计算误差更小，500hPa高原附近的24h气压预报更精确。

英文摘要：

Usually, a reference atmosphere is used to deduce the computing error of pressure gradient in the terrain-following dynamical equations. The reference atmosphere is static, satisfied hydrostatic balance. The real atmosphere is a perturbation from the reference atmosphere. The nearer the real atmosphere is from the reference, the smaller is the prediction error. The reference atmosphere can be isothermal atmosphere or a constant vertical temperature profile; this temperature profile can also be set as horizontal average of the initial value. In this paper we chose the last scheme to set the reference atmosphere. In a real 3-dimensional space, the initial value of a model is sparse, distributed on several vertical levels, so we give an analysis express of these sparse points using a cubic-spline function which is continuous and smooth in a section part. The new reference atmosphere is satisfied the hydrostatic balance in a difference formation, so the hydrostatic balance part in the equations can be removed at most. Comparing with the isothermal reference atmosphere. This scheme make the pressure gradient more accurate around the sharp terrain and can reduce the 500 hPa height prediction error.