机载光阵探头探测期间云粒子的破碎

机载光阵探头探测时,云粒子(液态和固态)进入二维光阵探头的采样区前,会因与探头探测臂发生机械碰撞,或者与探头外壳产生的湍流和风切变相互作用而破碎。破碎程度与粒子类型、大小、粒子密度、探头入口设计以及飞行空速等有关。利用2008年7~9月探测飞机(Y-12)在山西省太原地区的航测资料并对飞机采样期间的云粒子破碎现象进行介绍和分析,分析结果表明,粒子到达时间间隔分布具有双模态特征:长时间模态是粒子空间分布的真实结构,短时间模态则是云粒子破碎的结果。提出用粒子到达时间间隔阈值作为粒子破碎的判定标准,给出适用于2008年太原地区航测资料的粒子破碎识别阈值,其中适合于探头云粒子成像仪(CIP)的阈值是2×10-5 s,而探头降水粒子成像仪(PIP)的阈值是1×10-4 s。所提的阈值对于以Y-12为机载探测平台,以CIP和PIP探头为探测仪器所获取的其它航次云微物理图像资料的粒子破碎处理也是有一定的参考使用价值。

Cloud Particle Shattering during Sampling by Airborne Optical Array Probes

During sampling by airborne optical array probes, cloud particles (droplets or ice crystals) will shatter before entering into the sampling area, either by mechanical impaction with the instrument arms or by interaction with turbulence and wind shear generated by the probe housing. The shattering efficiency depends on the habit, size, and density of particles, as well as the probe inlet design, and airspeed. The phenomenon of cloud particle shattering during airborne sampling is presented in this paper. The data analyzed were from the flights of the Shanxi Y-12 research plane in the Taiyuan area from July to September 2008. It is shown that the distribution characteristics of inter-arrival times of particles can be bimodal:the long-term mode reflects the true structure of cloud particles distributed in space, and the short-term mode is the result of cloud particle shattering. An inter-arrival time threshold is proposed as a criterion for particle shattering identification. For the data analyzed in this study, the value was 2×10^-5 s and 10^-4 s for Cloud Imaging Probe (CIP) and Precipitation Imaging Probe (PIP), respectively. These values might also serve as reference thresholds for data from other Y-12 research plane flights.