一种新型高度地形追随坐标在GRAPES区域模式中的实现:理想试验与比较研究

Implementation of the Klemp height-based terrain-following coordinate in the GRAPES regional model: Idealized tests and inter-comparison

  • 摘要: 将一种新的高度地形追随坐标(Klemp坐标)引入了GRAPES区域模式,并与传统追随坐标(Gal-Chen坐标)和平缓地形追随坐标(SLEVE,Smooth Level Vertical coordinate)进行了比较。对不同坐标下气压梯度力的计算误差通过理想静止大气试验进行了评估,结果表明:与Gal-Chen坐标和SLEVE坐标相比,Klemp坐标有效地减小了气压梯度力的计算误差。理想重力波模拟试验表明,Klemp坐标下对重力波的模拟相比其他两种坐标也更接近于解析解。模式进一步采用了Mahrer气压梯度计算方案减少了计算误差,并提高了模式的精度和稳定性。实际个例试验与理想试验的结论相似。

     

    Abstract: A height-based terrain-following coordinate (Klemp coordinate) has been implemented into the GRAPES regional model and compared with the traditional Gal-Chen coordinate and smooth level vertical coordinate (SLEVE coordinate). Idealized tests of the resting-atmosphere and the gravity wave were designed and carried out to assess the model's performance. The results show that the computational errors of pressure gradient force under the Klemp coordinate were mostly reduced in comparison with the other two coordinates. For the gravity wave test, the simulation by using the Klemp coordinate significantly outperformed the others. Moreover, implementation of a generalized Mahrer's approach can further improve the accuracy of the horizontal pressure gradient force.The results of a real case experiment show similar conclusions.

     

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