用SSM/I微波遥感图像分析海上台风的螺旋云带

文中介绍了美国国防气象卫星专用微波成像仪 (SSM /I)上各通道的特性 ,分析了大气中各种粒子 (尤其是云滴和降水滴 )对各通道辐射的吸收和散射效应。通过对SSM /I图像上台风单通道剖面、双通道散点图的分析 ,揭示了台风在微波图像上表现形式的内在物理原因。在此基础上 ,设计了一个降水指数 ,方法是 :将 85 .5GHz的吸收段对称拉伸到散射段的延长线上 ,然后求归一化后的 19.35 ,37.0GHz和经拉伸处理的 85 .5GHz图像 3者的平均值。 3个通道合成降水指数克服了 37.0GHz对大雨滴不敏感 ,和 85 .5GHz对中等大小雨滴不敏感的缺点 ,比原始单通道微波图像更清楚地显示了台风的螺旋云带结构

ANALYSIS OF TYPHOON SPIRAL CLOUD BAND AT SEA WITH SSM/I IMAGE

The characteristics of DMSP SSM/I 's channels were introduced. The absorbing and scattering effects of the atmospheric particles (especially cloud droplets, rain drops) were analyzed. The physical reason of typhoon pattern's representation on microwave image was revealed. An index of precipitation was then induced as such: Symmetrically inverse channel 85 GHz's absorption segment and put it into the extension of the scattering segment. The precipitation index was formed as the average of three elements: uniformed 19 GHz, uniformed 37 GHz, and inversely uniformed 85 GHz. Three channel composed precipitation index overcame some shortcomings of the single raw channel, e.g., : 37 GHz is not sensitive to large rain drops, 85 GHz is not sensitive to medium-size rain drops. It was shown that the image of precipitation index could reveal typhoon's spiral structure more clearly.