A case study on the formation and evolution of ice supersaturation in the vicinity of a warm conveyor belt's outflow region
A case study on the formation and evolution of ice supersaturation in the vicinity of a warm conveyor belt's outflow region
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温暖传送带流出区附近冰过饱和度形成与演化的案例研究
DOI：
10.5194/acp-5-973-2005
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发表时间：
2004
影响因子：
6.3
通讯作者：
H. Wernli
中科院分区：
文献类型：
--
作者：
P. Spichtinger;K. Gierens;H. Wernli
抽象。一个案例研究的形成和演变的冰过饱和区（ISSR），发现在东北德国在2000年11月29日06：00 UTC。的ISSR位于附近的流出区域的温暖的传送带与强烈的事件在北大西洋东部的气旋。使用ECMWF分析和轨迹计算，它是确定当空气包变得过饱和，后来又亚饱和。在所考虑的情况下，气团过饱和状态可持续24小时以上。在东北部德国，ISSR的平均垂直延伸长度约为500 m，而在这里调查的ISSR的平均垂直延伸长度达到3km。研究的冰过饱和区域在垂直和水平方向上都与强烈的亚饱和空气接壤。从气象卫星红外图像推断，在无线电探空仪路径附近，ISSR可能没有云。然而，在ISSR的其他位置，很可能有卷云。相对湿度测量得到的林登伯格无线电探空仪被用来纠正的ECMWF湿度的负偏差，并构建二维地图的冰过饱和在欧洲在考虑期间。对这些地图上的ISSRs进行系统的后向轨迹分析表明，在前几天，ISSRs本身只经历了适度的上升运动，而部分ISSRs位于边界层强烈上升的气团上方。这定性地表明，温暖的输送带与中纬度气旋的扰动，可以诱导在对流层上部的ISSR的形成。ISSR图谱也使我们对ISSRs有了新的认识，ISSRs是一个大的动态的过饱和空气区域，卷云可以嵌入在某些位置，而在其他位置则有清晰的空气。
Abstract. A case study is presented on the formation and evolution of an ice-supersaturated region (ISSR) that was detected by a radiosonde in NE Germany at 06:00 UTC 29 November 2000. The ISSR was situated in the vicinity of the outflow region of a warm conveyor belt associated with an intense event of cyclogenesis in the eastern North Atlantic. Using ECMWF analyses and trajectory calculations it is determined when the air parcels became supersaturated and later subsaturated again. In the case considered, the state of air parcel supersaturation can last for longer than 24h. The ISSR was unusually thick: while the mean vertical extension of ISSRs in NE Germany is about 500m, the one investigated here reached 3km. The ice-supersaturated region investigated was bordered both vertically and horizontally by strongly subsaturated air. Near the path of the radiosonde the ISSR was probably cloud free, as inferred from METEOSAT infrared images. However, at other locations within the ISSR it is probable that there were cirrus clouds. Relative humidity measurements obtained by the Lindenberg radiosonde are used to correct the negative bias of the ECMWF humidity and to construct two-dimensional maps of ice supersaturation over Europe during the considered period. A systematic backward trajectory analysis for the ISSRs on these maps shows that the ISSR air masses themselves experienced only a moderate upward motion during the previous days, whereas parts of the ISSRs were located just above strongly ascending air masses from the boundary layer. This indicates qualitatively that warm conveyor belts associated with mid-latitude cyclogenesis are disturbances that can induce the formation of ISSRs in the upper troposphere. The ISSR maps also lead us to a new perception of ISSRs as large dynamic regions of supersaturated air where cirrus clouds can be embedded at some locations while there is clear air at others.