GRAPES_GFS中三维参考大气的研究:参考态构造和实际预报试验

A study on the three-dimensional reference atmosphere in GRAPES_GFS: Constructive reference state and real forecast experiment

  • 摘要: GRAPES_GFS(Global Regional Assimilation and PrEdiction System, Global Forecast System)采用基于等温大气构造的一维参考大气,前期的研究工作已在GRAPES_GFS的动力框架中引入了三维参考大气,并通过一系列理想试验检验了新方法的正确性以及计算精度。本部分研究工作,主要针对实际资料的预报试验,对比分析了不同三维参考态给定方法的优劣,并采用气候平均法,进行夏季两个月的四维变分循环预报试验。检验结果显示,使用三维参考大气后,模式的综合预报性能得到了提升,对流层高度场、温度场的预报偏差有所减小,长期积分过程中模式质量损失较为严重的问题也得到了明显的缓解。另外,通过动能谱的对比也可以看到使用三维参考大气后,模式在高层的能量耗散明显较小,能谱变化与观测更加吻合。

     

    Abstract: In the GRAPES_GFS (Global Regional Assimilation and PrEdiction System, Global Forecast System), a one-dimensional reference profile based on isothermal atmospheric structure is used. Previous research studies have introduced a three-dimensional reference profile into the dynamic core of the GRAPES_GFS, and a series of benchmark experiments have been carried out to verify the correctness and accuracy of the new method. The present study mainly focuses on real-data prediction experiments, comparing and analyzing the advantages and disadvantages of different three-dimensional reference state setting methods. The climatic average method is then used to carry out four-dimensional variational cycle forecasting experiments for two summer months. The results show that after using the three-dimensional reference profile, the comprehensive prediction performance of the model has been improved, the biases in the predicted tropospheric height and temperature have been reduced, and the severe loss of mass in long-term integration process has also been significantly alleviated. In addition, by comparing the kinetic energy spectra, it can be seen that the energy dissipation of the model at upper levels is significantly smaller after using the three-dimensional reference atmosphere, and the changes of the energy spectra are more consistent with observations.

     

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