Abstract The present study investigates the annual displacement of ITCZ and its role in forming and strengthening the precipitation systems in the southern part of Iran. To this end, the daily precipitation data of 71 meteorological stations were received. Then, the precipitation systems throughout cold seasons (October to May) were extracted. Next, the systems with maximum precipitation average were selected using the Deciles method. The ERA Interim data from the ECMWF (1997–2017) were used to determine the location and displacement of the ITCZ belt for the selected rainy days. In order to assess the position of ITCZ in each selected system, various indicators commonly used in global studies were evaluated. The results indicated that wind velocity and specific humidity of 700 hPa were the most appropriate indicators to determine the position/location of ITCZ in relation to rainfalls in the southern half of Iran. Finally, the average ITCZ position was determined by drawing the location of ITCZ on the date of occurrence of each system and the overlay of the maps. The findings revealed that, in all pervasive precipitation cases, an ITCZ branch was separated from Sudan and Western Ethiopia and extended to the south of the Red Sea through southwest-northeast. This phenomenon was noticeable in both the specific humidity and wind velocity indexes. Accordingly, in all rainy days in the region, the ITCZ belt was significantly orientated at the north expansion. Thus, this tongue extended to the center of Saudi Arabia. To conclude, strengthening low-pressure Sudanese systems is related to the north-oriented ITCZ expansion and tropical moisture advection into the system, especially in the middle levels. Therefore, heavy rains in the southern half of Iran and the Countries of the Arabian Peninsula are associated with the expansion to the north of a branch in the ITCZ. Further, the ITCZ settlement occurs mainly in the south of the equator from October to March, the northern boundary of which rarely reaches 5° north. However, its northward movement has increased since March, which is about 5°.

中文翻译：

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伊朗南半部热带辐合带扩张与降水关系研究

摘要 本研究调查了 ITCZ 的年位移及其在伊朗南部形成和加强降水系统中的作用。为此，收到了71个气象站的日降水数据。然后，提取整个寒冷季节（10 月至 5 月）的降水系统。接下来，使用Deciles 方法选择具有最大降水平均值的系统。来自 ECMWF（1997-2017 年）的 ERA 临时数据用于确定 ITCZ 带在选定雨天的位置和位移。为了评估 ITCZ 在每个选定系统中的位置，对全球研究中常用的各种指标进行了评估。结果表明，700 hPa 的风速和比湿度是确定 ITCZ 与伊朗南半部降雨相关的位置/位置的最合适的指标。最后，通过绘制每个系统发生日期的ITCZ位置和地图叠加来确定平均ITCZ位置。研究结果表明，在所有普遍降水案例中，ITCZ 分支与苏丹和埃塞俄比亚西部分开，并通过西南-东北延伸到红海以南。这种现象在比湿度和风速指标中都很明显。因此，在该地区所有的雨天，ITCZ 带都明显地向北扩展。于是，这个舌头延伸到了沙特阿拉伯的中心。总结一下，加强低压苏丹系统与北向的 ITCZ 扩张和热带湿气平流进入系统有关，尤其是在中层。因此，伊朗南半部和阿拉伯半岛国家的大雨与 ITCZ 分支向北的扩张有关。此外，ITCZ 定居点主要发生在 10 月至 3 月的赤道以南，其北部边界很少达到北纬 5°。然而，自3月以来，它的北向运动有所增加，约为5°。伊朗南半部和阿拉伯半岛国家的暴雨与 ITCZ 的一个分支向北扩张有关。此外，ITCZ 定居点主要发生在 10 月至 3 月的赤道以南，其北部边界很少达到北纬 5°。然而，自3月以来，它的北向运动有所增加，约为5°。伊朗南半部和阿拉伯半岛国家的暴雨与 ITCZ 的一个分支向北扩张有关。此外，ITCZ 定居点主要发生在 10 月至 3 月的赤道以南，其北部边界很少达到北纬 5°。然而，自3月以来，它的北向运动有所增加，约为5°。