双月刊

ISSN 1006-9895

CN 11-1768/O4

一个基于Eta垂直坐标的新WRF动力框架及山脉波数值试验
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1.地理信息工程国家重点实验室;2.中国气象局;3.中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室LASG

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A New Eta-Coordinate Based-WRF Dynamic Core and its Numerical Experiments
Author:
Affiliation:

1.Chinese Meteorological Administration;2.State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics LASG,Institute of Atmospheric Physics,Chinese Academy of Sciences

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    摘要:

    针对我国陡峭地形数值预报难题,本文在国际先进WRF(Weather Research and Forecasting)模式动力框架中引入阶梯地形垂直坐标,以期为改进复杂地形区域数值天气预报提供模式发展可选方案。我们首先设计一种变换方法,可以实现两种垂直坐标下动力方程组的形式一致,从而简化方程组离散及程序实现的复杂过程。本文推导的Eta坐标,与原Sigma坐标下WRF模式相比,主要差别在于模式参考面与模式顶之间空气质量的表达形式。在Eta坐标下的WRF动力框架搭建完成后,采用2D山脉波理想试验对新动力框架进行了检验,结果表明:由于阶梯地形固有的孤立分布特征,可造成不同台阶处气流的分离,从而使得阶梯地形在较粗垂直分辨率情形下,不能很好模拟山脉波;但如果垂直分层足够精细,或模拟时间足够长,可通过减弱气流分离现象或调整气流分布状态,对地形波进行有效刻画。

    Abstract:

    This paper mainly focuses on numerical weather prediction problem in the steep orographic region of China. The step terrain vertical coordinate (known as Eta) is introduced into the dynamic core of Weather Research and Forecasting model (WRF) to improve numerical forecasting in the complex orographic region. We firstly design a mathematic transformation scheme and give the Eta-coordinate WRF core the same formulation of model equation system as the Sigma WRF core, which can facilitate discretization and programming of the numerical model. The comparison between two dynamic frames shows that the difference just lies in representation of the column mass of atmosphere between the reference level and the top level of the model. We carry out 2D mountain wave simulation experiment and it is indicated that the inherent isolation of the step topography can result in the airflow separation, which accounts for inadequate simulation of the mountain wave with coarse vertical layering using the new Eta-coordinate WRF core. Fortunately, the mountain wave simulation will be improved using the new dynamic frame either with fine vertical resolution or with long simulation time, which is believed as alleviation on the airflow isolation of the step mountain.

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历史
  • 收稿日期:2020-06-23
  • 最后修改日期:2021-02-04
  • 录用日期:2021-03-02
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