ISSN 1006-9895

CN 11-1768/O4

A New Eta-Coordinate Based-WRF Dynamic Core and its Numerical Experiments
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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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    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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History
  • Received:June 23,2020
  • Revised:February 04,2021
  • Adopted:March 02,2021
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