PARSIVEL Snow Observations: A Critical Assessment
PARSIVEL Snow Observations: A Critical Assessment
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DOI：
10.1175/2009jtecha1332.1
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发表时间：
2010-02
影响因子：
2.2
通讯作者：
A. Battaglia;E. Rustemeier;A. Tokay;U. Blahak;C. Simmer
中科院分区：
文献类型：
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作者：
A. Battaglia;E. Rustemeier;A. Tokay;U. Blahak;C. Simmer
为了确定降雪的特征，对激光光学颗粒大小测速仪(PARSIVEL)的性能进行了评估。重新审查了PARSIVEL的测量原理，以检测其在应用于固体降水时的局限性和缺陷。这项研究使用了在加拿大Cloudsat/Cloud-Aerosol Lidar和红外探路者卫星观测(CALIPSO)验证项目(C3VP)活动期间进行的降雪观测，当时两台PARSIVEL仪器与一台单台二维散射仪(2-DVD)配置在一起，可以对雪花进行更详细的观测。在表征雪花大小时，PARSIVEL仪器本质上只检索一个大小参数，该参数大约等于最宽的水平尺寸(对于大的雪花更准确)，并且没有微观物理意义。与雨滴不同，等体积PARSIVEL直径-PARSIVEL输出变量-没有与雪花对应的物理参数。PARSIVEL对单个雪花粒子的下落速度测量可能并不准确。这是由于内部假设的水平和垂直雪粒尺寸之间的关系。不确定性源于与形状相关的因素，随着雪花尺寸的增加，形状相关因素往往越来越偏离统一，并可能产生较大的误差。当对大量雪花平均时，修正系数取决于大小，系统倾向于低估下落速度(但永远不会超过20%)。与用于长期活动的并置2-DVD相比，PARSIVEL似乎高估了小雪花和大颗粒的数量。PARSIVEL和2-DVD积雪测量之间的不一致只能部分归因于PARSIVEL的内在局限性(边界效应和尺寸问题)，但它必须解决这两种仪器在充分表征积雪特性方面的困难和缺陷。
The performance of the laser-optical Particle Size Velocity (PARSIVEL) disdrometer is evaluated to determine the characteristics of falling snow. PARSIVEL’s measuring principle is reexamined to detect its limitations and pitfalls when applied to solid precipitation. This study uses snow observations taken during the Canadian Cloudsat/Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) Validation Project (C3VP) campaign, when two PARSIVEL instruments were collocated with a single twodimensional disdrometer (2-DVD), which allows more detailed observation of snowflakes. When characterizing the snowflake size, PARSIVEL instruments inherently retrieve only one size parameter, which is approximately equal to the widest horizontal dimension (more accurately with large snowflakes) and that has no microphysical meaning. Unlike for raindrops, the equivolume PARSIVEL diameter—the PARSIVEL output variable—has no physical counterpart for snowflakes. PARSIVEL’s fall velocity measurement may not be accurate for a single snowflake particle. This is due to the internally assumed relationship between horizontal and vertical snow particle dimensions. The uncertainty originates from the shape-related factor, which tends to depart more and more from unity with increasing snowflake sizes and can produce large errors. When averaging over a large number of snowflakes, the correction factor is size dependent with a systematic tendency to an underestimation of the fall speed (but never exceeding 20%). Compared to a collocated 2-DVD for long-lasting events, PARSIVEL seems to overestimate the number of small snowflakes and large particles. The disagreement between PARSIVEL and 2-DVD snow measurements can only be partly ascribed to PARSIVEL intrinsic limitations (border effects and sizing problems), but it has to deal with the difficulties and drawbacks of both instruments in fully characterizing snow properties.