曲率修正线性平衡方程及其在变分同化风压约束中的应用

THE CURVATURE-MODIFICATION LINEAR BALANCE EQUATION AND ITS APPLICATION TO THE BALANCE BETWEEN WIND AND PRESSURE IN VARIATIONAL DATA ASSIMILATION

针对强涡旋系统(热带气旋、一些中尺度系统)变分同化分析中风压平衡约束关系的特点,提出了一个新的风压平衡约束关系——曲率修正线性平衡方程,它具有形式与线性平衡方程相同,并清晰地包含了曲率的作用,同时,当曲率较小时可退化成线性平衡方程。曲率修正线性平衡方程能方便地应用于中国数值预报研究中心开发的三维变分同化分析系统Grapes3DV中,试验结果证明其具有较好的效果和较理想的特性,提高了分析质量,并改善预报水平。

In view of the problem related to the balance between wind and pressure in the variational data assimilation of intensity-vortex system （such as tropical cyclones and some mesoscale systems）, a new relation of balance between wind and pressure, the curvature-modification linear balance equation, is suggested. It is like the linear balance equation in form and clearly contains the curvature＇s function. It retrogresses to the linear balance equation when the curvature-vortex becomes small. The curvature-modification linear balance equation is conveniently used within the 3-dimension variational data assimilation system Grapes3DV developed by Chinese Academy of meteorological Sciences. Experiments show that the scheme is effective, because it improves the analysis quantity and is beneficial to the forecast.