Spatial, vertical and temporal variations in the subtropical jet stream over Africa and the Middle East were studied from 1958 to 2016 using NCEP/NCAR reanalysis meteorological data. The results of this study showed that the jet stream was located at a pressure level of 200 hPa more than 87% of the time, and it was located in the meridional zone between 20°N and 35°N in more than 83% of these cases. Additionally, the annual winter distribution of the jet stream illustrated two distinct trends: the first trend ended in 1987 and had a high rate of decrease, and the second trend began in 1988 and had a small rate of increase. Furthermore, synoptically, the study showed that the southern shift of the jet stream intensified the low-pressure systems over Africa and the Mediterranean, in addition to producing favorable conditions for the northward extension of the Red Sea Trough. However, the northward shift was related to the intensified Azores high-pressure system over Africa and the southern Mediterranean. Moreover, the temporal variations of the jet stream indicated that the intensification of the high-pressure system (i.e., the Azores and Siberian highs) tended to decrease the number of jet stream cases at 200 hPa or vertically shifted them downward to 250 hPa.

中文翻译：

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与非洲和中东副热带急流冬季变率相关的天气特征

使用 NCEP/NCAR 再分析气象数据研究了 1958 年至 2016 年非洲和中东亚热带急流的空间、垂直和时间变化。本研究结果表明，87%以上的急流位于200 hPa压力水平，83%以上的射流位于20°N和35°N之间的子午带。案件。此外，冬季急流年分布呈现出两个明显的趋势：第一个趋势结束于1987年，下降幅度较大，第二个趋势始于1988年，增幅较小。此外，从天气上看，该研究表明，急流的南移加强了非洲和地中海上空的低压系统，为红海槽向北延伸创造了有利条件。然而，北移与非洲和地中海南部的亚速尔高压系统增强有关。此外，急流的时间变化表明，高压系统（即亚速尔群岛和西伯利亚高压）的增强倾向于减少 200 hPa 时的急流案例数量或将它们垂直向下移动到 250 hPa。