一次高原低涡降水过程的特征分析

发布时间：2018-03-25 06:11

本文选题：高原低涡　切入点：地形降水　出处：《中国气象科学研究院》2017年硕士论文

【摘要】：本文利用第三次青藏高原大气科学试验的多种雷达、雨滴谱以及MODIS卫星观测资料、常规气象站地面和高空观测资料,针对2014年7月14日发生在青藏高原中部那曲地区的一次降水过程,研究了降水的时空变化特征,触发不同阶段降水的天气尺度和中尺度环流系统以及相关的云降水物理特征,得到的主要结论如下:(1)从降水演变特征看,这次降水过程包括三个阶段,即发生在下午的强降水阶段和夜间的两个弱降水阶段。(2)从影响系统看,下午的降水过程主要由天气尺度的高原低涡发展引起,此时那曲位于低涡中心前部的中尺度辐合线上,雷达回波呈现出向东北方向传播的特征,随着高原低涡的减弱,那曲第一阶段降水结束;发生在晚上的降水过程主要与高原低涡前部的暖湿东南气流爬越那曲附近的地形有关,东南气流为产生降水提供了有利的水汽、大气不稳定和浅薄的动力抬升条件;随着低层东北气流加强,雷达回波总体上向西南方向传播。(3)从云降水微物理特征看,高原低涡降水初期,低涡前部的上升运动深厚,在地面以上3~(-1)1 km高度之间的上升气流速度超过3 m s~(-1),对流发展明显,而在后期对流性明显减弱,伴随着云顶升高;东南气流爬坡引起的地形降水以层状云降水为主,并且层状云上部有上升气流存在;高原低涡降水的雨滴谱分布较宽(0.3-4.9 mm),而夜间降水过程的雨滴谱分布较窄(0.3-2.1 mm)。(4)对于引起第一个降水阶段的高原低涡来说,该高原低涡的发展主要是由低层辐合的加强引起,而高层涡度平流和散度项则加强了反气旋环流。
[Abstract]:In this paper, the radar, raindrop spectrum and MODIS satellite observation data of the third Qinghai-Xizang Plateau atmospheric science experiment are used, and the surface and upper air observation data of conventional weather stations are used. Based on a precipitation process in Naqu area of the central Qinghai-Tibet Plateau on July 14, 2014, the temporal and spatial variation characteristics of precipitation, the synoptic scale and mesoscale circulation system of triggering precipitation in different stages and the related physical characteristics of cloud precipitation are studied. The main conclusions obtained are as follows: (1) from the point of view of the evolution of precipitation, the precipitation process consists of three stages, that is, the heavy precipitation stage in the afternoon and the two weak precipitation stages in the night) from the perspective of the influence system. The precipitation process in the afternoon is mainly caused by the synoptic scale of the plateau vortex development. At this time, Naqu is located on the mesoscale convergence line in front of the center of the low vortex. The radar echo shows the characteristics of propagation to the northeast, and with the weakening of the plateau low vortex, The precipitation process in the evening is mainly related to the warm and wet southeastern airflow in front of the plateau vortex which climbs over the topography near Naqu, and the southeast air stream provides favorable water vapor for the precipitation. Atmospheric instability and shallow dynamic uplift conditions; with the enhancement of the lower northeast air flow, the radar echo propagates generally to the southwest.) from the microphysical characteristics of cloud precipitation, the rising motion of the front part of the low vortex precipitation in the plateau is deep in the initial stage. The updraft velocity between 3 ~ 1 km above the surface is more than 3 m ~ (-1) m ~ (-1), the convection develops obviously, but in the later stage the convection becomes weaker, accompanied by the rise of the cloud top, and the topographic precipitation caused by the southeasterly flow climbing slope is mainly stratiform cloud precipitation. And there is updraft in the upper part of stratiform cloud, the raindrop spectrum distribution of low vortex precipitation in the plateau is wider 0.3-4.9 mm ~ (-1), while that of rain drop spectrum in the process of night precipitation is narrower (0.3-2.1 mm 路m ~ (4)) for the plateau vortex which causes the first precipitation stage, The development of the low vortex in the plateau is mainly caused by the enhancement of convergence in the lower layer, while the advection and divergence of vorticity in the upper layer strengthen the anticyclonic circulation.
【学位授予单位】：中国气象科学研究院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P458.121

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