不同侧边界条件下水平有限降水云的微波辐射模式研究

Model Study of Microwave Radiances Emerging from Horizontally Finite Precipitating Clouds with Different Lateral Boundary Conditions

从空间微波遥感降水定量分布的目标出发，本文研究在非对称侧边界条件下水平有限降水云的微波辐射率的计算公式。由普适性三维辐射传输方程出发，推导出非对称横向边界条件下的微波辐射率解析表达式．用热带降水云典型参数所作初步数值试验表明，相对于对称侧边界条件非对称侧边界条件对于上行（卫星所测）辐射率具有不可忽略的作用，且这种作用对于不同的微波频率具有不同的强度，甚至有符号的差别。云的不均匀尺度越小，这种作用越强。由于热带降水大多具有高度非均匀对流云带状或云团结构，本文所发展的模式将对微波遥感这类降雨定量分布发挥重要作用。

In order to compute microwave radiances emerging from horizontally finite clouds of hydrometeors under non-symmetric lateral boundary conditions, the method of solving three-dimensional radiahve transfer eqhahon under non-symmetric lateral boundary conditions was discussed. A radiative transfer model was developedaccording to the theory. The results of preliminary computations indicate that the smaller the cloud size, the greater the lateral boundary effect.In order to depict the non-uniform structure of clouds, the parameter of cloud size must be small enough, and then the fat6ral boundary condition must be correctly given. when the- precipitating cloud is horizontally non--uniform and not an isolated structure, computing microwave brightness temperatures by means of symmetric lateral boundary model may introduce error. The higher the channel frequency, the greater the error.