祁连山冬季降雪个例模拟分析(Ⅱ):人工催化试验

Numerical Simulation of Snowfall in Winter of Qilian Mountains. Part(Ⅱ):Seeding Test

利用部分改进了的中尺度模式MM5V3对2006年2月7~8日甘肃北部地区一次冷云降雪过程进行了人工催化的数值试验,研究加入人工冰晶对祁连山北坡地区冷性层云降雪的影响。进行了不同剂量和不同高度的催化试验,详细分析了催化后的微物理过程和动力热力过程的变化。结果表明：累积降雪中心的上风方含有过冷云水的区域为催化潜力区,催化后累积降雪中心雪量增加,增雪区周围出现分散的减雪区。过冷云水最多并且最缺乏冰晶粒子的层次具有很好的催化条件。加入人工冰晶后消耗了水汽和过冷云水,冰晶和雪的量值均有所增加,雪碰并冰晶过程、冰晶转化过程、凝华过程是雪增长的主要过程,相态变化引起的潜热增加导致升温和上升运动加强。这种变化同时使周围的垂直运动和水成物含量发生改变,周围的上升运动减弱,雪的含量减少,产生了减雪区。

A snowfall process in Qilian mountains during 7-8 February 2006 is simulated using the mesoscale model MM5V3. Seeding tests are made in order to study the effects of adding artificial ice particles to the snowfall. Tests of different seeding amounts and seeding heights are conducted. The changes of the microphysical processes and thermal and dynamical processes are analyzed. Results show： The seeding area is in the upwind of snowfall center with the supercooled water. After seeding, the precipitation increases at snowfall center and decreases around the center. It is to increase more snowfall if seeding in the levels of more supercooled water and less ice particles. The vapour and supercooled water are depleted to increase ice and snow. The collection of ice by snow, the conversion of ice to snow and the deposition of snow are the main sources of snow. The changes of microphysical phases release more latent heat which results in warming the atmosphere and strengthening the updraft. At the same time these changes affect the vertical velocity and hydrometers surrounding the snowfall center. The updraft become weaker and snow become less which produces the decrease snowfall area.