For more than one century, the penetration of the Mediterranean Sea Breeze into the Jordan Valley has been studied. At times, the associated downslope westerlies in the Dead Sea area exhibit foehn characteristics, leading to a warming and drying upon arrival and therefore contradicting the typical characteristics of a sea breeze. In this paper, a particular summer day (16 August 2014) is analyzed using a kilometre-scale model simulation. For the first time, the Mediterranean Sea Breeze penetration is investigated with Lagrangian backward trajectories and its characterization is extended to the entire Jordan Valley. Along the western slopes of the valley, two well-distinguishable layers are detected in the afternoon: a moist and cold sea breeze layer, and a dry and warm foehn layer above. While the air parcels of both layers cover similar pathways in the hours before reaching the Jordan Valley, they originate from strikingly different altitudes. For this reason, significant differences in their temperature evolution and humidity content are detected. In the evening, the Mediterranean Sea Breeze layer is eroded, enabling the foehn layer to reach the surface. The arrival of foehn retards the afternoon cooling and leads to a decrease in relative humidity. This unique imprint of foehn breakthrough is confirmed by in situ measurements. Therefore, the two-layered flow pattern is found to be a key element in understanding the mesoscale wind system and the surface signals in the Dead Sea area. The foehn layer is spatially confined to the Dead Sea area since the locally elevated upstream Judean Mountains cause a major disturbance of the westerly flow. This work extends the knowledge on summer mesoscale flows in the Jordan Valley and on different types of foehn-breeze interactions.

中文翻译：

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是焚风还是海风？约旦河谷水流的欧拉和拉格朗日分析

一个多世纪以来，人们一直在研究地中海微风侵入约旦河谷的情况。有时，死海地区相关的下坡西风表现出焚风特征，导致抵达后变暖和干燥，因此与海风的典型特征相矛盾。在本文中，使用公里级模型模拟对特定的夏日（2014 年 8 月 16 日）进行了分析。首次利用拉格朗日后向轨迹研究地中海微风的穿透力，并将其特征扩展到整个约旦河谷。沿着山谷的西坡，下午检测到两个明显可区分的层：潮湿而寒冷的海风层，上面是干燥而温暖的焚风层。虽然这两层气团在到达约旦河谷前的几个小时内覆盖了相似的路径，但它们的起源高度却截然不同。因此，检测到它们的温度演变和湿度含量存在显着差异。晚上，地中海海风层被侵蚀，使得焚风层到达地表。焚风的到来延缓了下午的降温，导致相对湿度下降。现场测量证实了焚风突破的独特印记。因此，两层流型被认为是理解死海地区中尺度风系统和表面信号的关键要素。焚风层在空间上仅限于死海地区，因为上游朱迪亚山脉局部升高对西风流造成了重大扰动。这项工作扩展了有关约旦河谷夏季中尺度流动以及不同类型的焚风与微风相互作用的知识。