The impact of ground‐based glaciogenic seeding on clouds and precipitation over mountains: A case study of a shallow orographic cloud with large supercooled droplets
The impact of ground‐based glaciogenic seeding on clouds and precipitation over mountains: A case study of a shallow orographic cloud with large supercooled droplets
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DOI：
10.1002/2014jd022693
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发表时间：
2015-06
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影响因子：
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通讯作者：
B. Pokharel;B. Geerts;Xiaoqin Jing
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文献类型：
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作者：
B. Pokharel;B. Geerts;Xiaoqin Jing
本文研究了地面冰川催化对浅，轻微降水的地形云与相当大的（~35 µm）过冷液滴的影响。2012年2月22日，怀俄明州的碘化银（AgI，银）播种云影响调查（AgI Seeding Cloud Impact Investigation）实验观测到这场风暴。云底（顶部）温度约为−5°C（−12°C）。来自机载多普勒W波段（3 mm）剖面怀俄明州云雷达（WCR）的垂直速度数据表明，由于强风（20 m s-1）撞击地形和小袋强烈上升气流，云有很大的上升空间。大的水滴，低的水滴和冰粒浓度，以及强烈的上升气流导致自然降雪的增长主要是通过堆积（霜）。将处理（接种）期与之前的未处理期进行比较。根据对降雪的微量化学分析，位于山口的主要目标地点受到碘化银播种的影响。来自三个雷达系统的数据被用于分析播种对雪生长的影响：WCR，两个Ka波段（1.2厘米）剖面微雨雷达和一个X波段（3厘米）扫描偏振多普勒雷达。这种情况有点复杂，云液态水的自然增加和雪的增长，在播种期间开始中途，并在播种结束后继续。来自厘米波雷达系统的复合数据表明，即使考虑到在逆风控制区观察到的自然趋势，在播种期间低层反射率也会增加。在主要目标地点的降水粒子探测器显示，小型和大型水凝物的浓度都有所增加。
This paper examines the impact of ground‐based glaciogenic seeding on a shallow, lightly precipitating orographic cloud with rather large (~35 µm) supercooled droplets. The storm was observed on 22 February 2012 as part of the AgI (silver iodide) Seeding Cloud Impact Investigation experiment in Wyoming. The cloud base (top) temperature was about −5°C (−12°C). Vertical velocity data from an airborne Doppler W‐band (3 mm) profiling Wyoming Cloud Radar (WCR) indicate broad ascent due to the strong wind (20 m s‐1) impinging on the terrain and small pockets of intense updrafts. The large droplets, low droplet and ice particle concentrations, and strong updrafts lead to natural snow growth mainly by accretion (riming). The treated (seeded) period is compared with the preceding untreated period. The main target site, located on a mountain pass, was impacted by AgI seeding, according to a trace chemistry analysis of the falling snow. Data from three radar systems were used in the analysis of the impact of seeding on snow growth: the WCR, two Ka‐band (1.2 cm) profiling Micro Rain Radars , and an X‐band (3 cm) scanning polarization Doppler‐on‐Wheels radar. This case is complicated somewhat by a natural increase in cloud liquid water and in snow growth by riming, starting halfway during the seeding period, and continuing after seeding ended. Composite data from the centimeter‐wave radar systems indicate an increase in low‐level reflectivity during seeding, even after accounting for the natural trend observed in the upwind control region. A precipitation particle probe at the main target site shows an increase in concentration of both small and large hydrometeors.