The sting at the end of the tail: Model diagnostics of fine‐scale three‐dimensional structure of the cloud head
The sting at the end of the tail: Model diagnostics of fine‐scale three‐dimensional structure of the cloud head
复制标题
尾端的刺：云头精细三维结构的模型诊断
DOI：
10.1256/qj.04.36
复制
发表时间：
2005
影响因子：
8.9
通讯作者：
C.‐G. Wang
中科院分区：
文献类型：
--
作者：
P. Clark;K. Browning;C.‐G. Wang
这是关于“尾端刺痛”系列论文中的第二篇，“尾端刺痛”是一种具有潜在破坏性的地面风的中尺度区域，可能发生在靠近被温带气旋弯曲后前端包裹的云头蒸发尖端的地方。在第一篇论文中，刺痛现象是通过对1987年10月大风暴的纯粹观测研究确定的。本文利用高分辨率数值天气预报模式的观测验证预报来研究刺痛现象的三维结构演变。结果表明，1987年10月风暴中破坏性的地面风是由一个明确定义的中尺度“刺状急流”（SJ）造成的，该急流可识别为起源于约650 hPa的多云空气的连续轨迹集合。有证据表明存在多个中尺度倾斜环流，而SJ似乎形成于这些环流的下降部分。SJ内的空气在大约4小时的时间内下降到900 hPa的水平，在此期间它从小于20 m s - 1加速到超过45 m s - 1，极值大于50 m s - 1。尽管SJ空气的湿球势温在下降到900 hPa的过程中保持不变，但蒸发导致喷气机某些部分的干球势温下降高达5 K或更多。SJ位于初级冷锋后面，与相关的暖输送带低空急流不同；它也不同于冷传送带低空急流，当SJ绕着弯曲的后锋面时，它仍然在它的下方和后面。©皇冠版权所有，2005。
This is the second in a series of papers on ‘the sting at the end of the tail’—a mesoscale region of potentially damaging surface winds that can occur close to the evaporating tip of a cloud head wrapped around the bent‐back front of an extratropical cyclone. In the first paper the sting phenomenon was identified from a purely observational study of the great storm of October 1987. In the present paper an observationally validated forecast run from a high‐resolution numerical weather prediction model is used to examine the evolving three‐dimensional structure of the sting phenomenon. It is shown that the damaging surface winds in the October 1987 storm were due to a well‐defined mesoscale ‘sting jet’ (SJ), identifiable as a coherent ensemble of trajectories originating in cloudy air at about 650 hPa. There is evidence of multiple mesoscale slantwise circulations, and the SJ appears to form within the descending part of these circulations. Air within the SJ descends to the 900 hPa level over a period of about 4 h, during which time it accelerates from less than 20 to above 45 m s−1 with extremes greater than 50 m s−1. Although the wet‐bulb potential temperature of air in the SJ remains constant during its descent to 900 hPa, evaporation leads to a reduction of up to 5 K or more in dry‐bulb potential temperature in some parts of the jet. The SJ is situated behind the primary cold front, and is distinct from the associated warm‐conveyor‐belt low‐level jet; it is also distinct from the cold‐conveyor‐belt low‐level jet which remains below and behind it as the SJ skirts the bent‐back front. © Crown copyright, 2005.