一次过冷层状云催化云迹微物理特征的卫星遥感分析  

ANALYSIS OF SATELLITE OBSERVED MICROPHYSICAL SIGNATURES OF CLOUD SEEDING TRACKS IN SUPERCOOLED LAYER CLOUDS

作　　者：戴进[1] 余兴[1] Daniel Rosenfeld 徐小红[1] 

机构地区：[1]陕西省气象科学研究所,西安710015 [2]希伯莱大学地球科学学院

出　　处：《气象学报》2006年第5期622-630,共9页Acta Meteorologica Sinica

基　　金：国家自然科学基金(40575004);科技部社会公益研究专项(2005DIB3J099)

摘　　要：利用卫星反演技术,通过卫星观测到的一次人工增雨催化作业后形成的云迹线个例,分析了云迹线与其周围云的光谱特征、亮温、亮温差、云顶粒子有效半径等云微物理特征,比较了它们之间的差异,揭示了这次过冷层状云催化的微物理效应。云迹实际上是持续时间超过80 min、宽和深分别约为14 km和1.5 km的云谷。云迹周围的云顶粒子有效半径为10—15μm,而云沟内的粒子在15—24μm变化。周围云体由过冷滴组成,中间可能夹杂了一些低浓度的冰粒子,云沟内云的主要成分是冰。和周围未被催化的云相比,0.6μm通道的光谱反射率,在云沟处有明显的增加,而3.7μm通道反射率在云沟内是降低的,尽管其绝对变化幅度不大,但其相对变化幅度较大。随着播云时间的增加,云沟深度、宽度逐渐增加,云沟内和周围云体的温差逐渐增加,对通道4和5而言,在最早催化部位,最大分别达到4.2℃和3.9℃,4和5通道之间云沟内的亮温差也是随冰晶化时间的增加而增加,最大为1.4℃,而云沟周围云为0.2—0.4℃。云沟的形成、云沟内云顶温度的增加和4,5通道之间亮温差的增加,都足以说明被播云体变薄,其原因是由于云顶降水使得云内的水流失,云顶下降。云顶冰晶化、冰粒子增长成降水造成云顶下沉,是云沟形成的主要原因。对于本次播云作业,晶化作用在播云22 min后逐渐显现。在播云后38—63 min,有新的水云在云沟的中间部位生成,可能是由于冻结潜热释放引起的上升运动所致。而新生水云在形成较早的云迹中没有出现,这些较早形成的云迹在80多分钟的整个观测期间持续扩散。最终,在周围云从外向云沟内的扩散过程中,云沟开始消散。Based on the satellite retrieval methodology, the spectral characteristics and cloud microphysical properties were analyzed that included brightness temperatures of channel 4 and 5, and the brightness temperature difference （BTD）, the particle effective radius for cloud tracks caused by an operational cloud seeding. The same analyses of the ambient clouds were conducted for comparing the property differences between the cloud tracks and the surrounding clouds, and the microphysical signatures of cloud seeding were revealed. The cloud tracks actually were a cloud valley 1.5 km deep and 14 km wide lasting more than 80 minutes. The particle effective radius of ambient clouds was 10 - 15 μm, while that of cloud tracks ranged from 15 to 24 μm. The ambient clouds were composed of supercooled droplets, possibly with low concentrations of ice particles; the composition of the cloud within the seeding track was ice. Within the cloud tracks, the reflectance at 0.6μm increased obviously, and the reflectance at 3.7μm decreased with rather large relative varying magnitude compared with the unseeded ambient clouds. As cloud seeding advanced, the width and depth were gradually increased, and their maximums covered 14 km and 1.5 km. Simultaneously, the cloud top temperature in the tracks became progressively warmer with respect to the ambient clouds ; the maximum temperature differences reached 4.2 and 3.9 E at the first seeding positions for channel 4 and 5. In addition to, the BTD in the tracks also increased steadily to a maximum of 1.4 E, contrast to 0.2 - 0.4 E of the ambient clouds. The evidence that the seeded cloud became thinner comes from the visible image showing a valley, the warming of the cloud tops in the seeded track and the increase of BTD in the seeded track. The seeded cloud became thinner because the cloud top descended and it lost water to precipitation throughout its depth. For this cloud seeding case, the glaciation became apparent at cloud tops about 22 minutes after seeding. The formation of a cl

关 键 词：过冷层状云 云迹 微物理特征 卫星反演 催化. 

分 类 号：P481[天文地球—大气科学及气象学]