【摘要】 <正> 在雷达观测强风暴移动的过程中,屏幕上看到的风暴回波的形态结构是在不断变化着的。这种变化的原因包含有风暴本身结构随时间的演变,以及雷达探测性能中与距离有关的因素。为了单独考察后者的影响,可以计算某些不同距离上固定云模式的回波图象。Atlas等曾给出了二维轴对称降水模式在近距离上的回波图象。他们的计算忽略了波束宽度的影响,但考虑了雨的衰减和距离衰减的影响,得到了蝴蝶形的回波图象模更多还原

【Abstract】 In this paper, the distribution of apparent reflectivity at the attenuation wavelength for the inhomogeneous three dimensional cloud pattern at different distances from the radar station has been calculated. In the calculation several factors are considered: unequal distribution of the transmitted energy in the radar beam, medium extinction and range extinction in the path, the variation of beam elevation with range, and the effect of occultation of beam by the ground. Based on our calculation, the difference between the measured apparent reflectivity value and the original model value is given. The result indicates that for the typical severe convective cloud having high reflectivity core the apparent reflectivity value might be evidently higher than the actual model value for most part of the cloud when it is far from the radar station. This phenomena is mainly due to the beam width effect.更多还原