Four dimensional variational data assimilation technology is an important method to enhance the effect of numerical whether forecast Tangent mode and adjoint mode are the key technology of assimilation system .

四维变分同化技术是提高数值天气预报时效的重要方法， 切 线性模式和伴随模式是同化系统的 关键技术。

The diameter of actual tangent circle is an important parameter for safety of boiler the residual rotation is the key factor of flue gas temperature deviation at furnace exit .

实际 切圆直径是锅炉稳定安全运行的一个重要参数，炉膛出口残余旋转是造成烟温偏差的 主要原因。