In this study, the frequency of effective jet streams was analyzed in extreme and widespread precipitations in the west of Iran. For this purpose, the daily precipitation of 69 synoptic and climatic stations over 18,624 days (1961–2010) were selected. Then, 119 days of extreme and widespread precipitation in the study area were chosen based on generalized distribution for conducting related reviews and analyses. The frequency of jet streams in the geographical location from 0° to 120°E and −10° to 80°N were reviewed at four levels (250, 300, 400 and 500 hPa). Due to the large volume of information, only the highest and lowest levels (250 and 500 hPa) in relation to the surface were considered. According to the results, the highest frequency of jet stream was observed at 250 hPa. The second quarter of the jet stream core lay over the west of Iran (which is associated with increasing positive vorticity as well as upper-level divergence and lower-level convergence of the atmosphere). In general, the extension of jet stream up to 500 hPa indicated an unstable layer thickness, which can cause extreme and widespread precipitation in the west of Iran. The results of selected days based on cluster analysis and Lund correlation revealed that in rainy days, the wind speed was more than 50 m/s and the subtropical jet stream speed was over 40 m/s, leading to extreme precipitation in the west of Iran.

在这项研究中，分析了伊朗西部极端和广泛降水中有效射流的频率。为了这个目的，选择了69个天气和气候站在1961-2010年期间的每日降水量。然后，根据广义分布选择了研究区119天的极端和普遍降水，以进行相关的回顾和分析。在四个级别（250、300、400和500 hPa）下，对地理位置从0°E至120°E和-10°至80°N的喷射流频率进行了评估。由于信息量很大，因此只考虑了相对于表面的最高和最低水平（250和500 hPa）。根据结果​​，在250 hPa观察到喷射流的最高频率。射流核心的第二部分位于伊朗西部（这与正涡度的增加以及大气的高层分流和高层交汇有关）。通常，射流扩展到500 hPa表示层厚不稳定，这可能会在伊朗西部引起极端广泛的降水。基于聚类分析和隆德相关性的选定天数结果表明，在雨天，风速超过50 m / s，副热带急流速度超过40 m / s，导致伊朗西部出现极端降水。这可能会在伊朗西部造成极端和广泛的降水。基于聚类分析和隆德相关性的选定天数结果表明，在雨天，风速超过50 m / s，副热带急流速度超过40 m / s，导致伊朗西部出现极端降水。这可能会在伊朗西部造成极端和广泛的降水。基于聚类分析和隆德相关性的选定天数结果表明，在雨天，风速超过50 m / s，副热带急流速度超过40 m / s，导致伊朗西部出现极端降水。