Can there be a relationship with blocking systems and atmospheric rivers in the important atmospheric phenomena of middle latitudes such as torrential and heavy rains in the tropics?

Blocking systems and atmospheric rivers are important atmospheric phenomena in mid-latitudes. Occurrence of blocking can cause climatic anomalies such as extreme cold, dry and wet periods and heavy rains. Considering the damage caused by heavy rains, it is very important to know the mechanisms governing this phenomenon. Due to its mountainous topography and being in the path of western winds and atmospheric rivers, Iran's plateau is prone to heavy rainfall and dangerous floods. Mediterranean systems in the subtropical region could not produce heavy rainfall in southwest and west of Iran. If the Mediterranean and Sudan systems, which are known as the Mediterranean-Sudanese pattern, merge in the eastern Mediterranean or Iraq and operate simultaneously, they can cause extensive rainfall from the northwest to the southwest of Iran. Another example is the dynamic interaction between Iran's low-pressure monsoon fleet and the western wind system in summer, which leads to summer rainfall in the southeast. Investigating the role of blockings and atmospheric river in the occurrence of heavy rains in different regions of Iran can play an important role in predicting and managing this phenomenon.

The formation of atmospheric rivers (ARs) is directly related to extratropical-tropical interactions and the occurrence of heavy precipitation. In the extratropics, AR is responsible for transporting nearly 90% of atmospheric water vapor to higher latitudes (Ralph 2017). AR plays an important role in the global water cycle and can lead to natural events such as hurricanes and storms (Akbari et al. 2019; Salimi et al. 2020). Kerr (2006) believes that only 20–40% of AR water vapor reaches the Earth's surface and can lead to hurricanes and storms. The arrival of Rossby waves in the subtropical region can transfer moisture from the subtropical regions to the extratropical regions and cause the formation of AR. The horizontal circulation associated with midlatitude storms may lead to poleward transport of tropical moisture as well as AR formation in the warm part of a storm (Sodemann et al. 2020). AR is a key factor in the study of water vapor in the subtropics (Ejimenu 2014), which can lead to heavy precipitation due to high water vapor and static stability, especially when it is directed toward topographic barriers and forced to rise (Zhu and Newell). 1998; Ralph et al. 2017, 2018;) There are seven important regions in the world, which include the western part of the United States of America, the western part of the southern cape of South America, northwestern Europe, the northeastern route of the Arabian Peninsula to Iran, Australia, and the distance between Japan and the eastern coast. Russia is where AR has the greatest impact on precipitation occurrence. Southwest Asia is one of the most important regions where AR plays an important role in its precipitation. Approximately 90% of ARs that go into the oceans are longer than other ARs (Salimi et al. 2020). The subtropical jet stream is considered an important synoptic factor in the formation, path and direction of ARs (Salimi and Saleha 2016; Lashkari and Esfandiari, 2020, 2021; Salimi, et al., 2020; Akbari et al., 2019). In addition, the presence of high and low pressure centers, especially subtropical high pressure centers (STHP), are the main factors (Salimi et al. 2020). Special attention should be paid to the role of the western storm in the monthly pattern of the displacement of the AR axis and heavy rainfall, whose movement to the west and east along the Mediterranean Sea trough plays an important role in the path of the arrival of the AR to Iran (Lashkari and Esfandiari 2021). Investigating specific moisture maps of the interactions between extratropical low circulation systems (COL) and subtropical Arabian subtropical anticyclone at the lower level, as well as the Arabian anticyclone in the southern branch of the mid-level westerly winds, which led to the formation of AR with tropical origin. AR originates from the Intertropical Convergence Zone (ITCZ) between 0 and 10°N. In two points of the synoptic maps, moisture transfer from the subtropical to the subtropical region can be seen in the meridian direction (southwest-northeast) in high latitudes. that both COLs outside the tropics have deeply penetrated into the tropical region up to 15°N. This factor can be the reason for the dynamic rise of the extratropical region, which has led to the transfer of moisture from the subtropical region to the extratropical region by entering the subtropical region. . The first point is in the eastern Atlantic Ocean. The outer curve of a closed storm that has completely separated from its main flow, the deep Iceland storm, enters the Atlantic Ocean at 15°N. A divergence zone that along the COL divergence transports the temperature and humidity of the ITCZ of the Atlantic Ocean and western North Africa to the subtropical latitudes up to 25°N over western North Africa. The second point is located in the west of the Middle East. The COL in eastern Turkey reaches eastern North Africa, the Red Sea, and the Arabian Peninsula up to 15°N, causing suction and increasing ITCZ moisture to the extratropical region. It extends along the COL divergence zone and the Arabian anticyclone up to 38°N over Iran. In eastern Turkey, the Arabian subtropical anticyclone plays an important role in the transport of the Jo river. In addition, several atmospheric sources in the subtropical region inject moisture into the atmospheric river with its anticyclonic circulation. Atmospheric rivers in East Africa are fed and strengthened by crossing the Red Sea and the Persian Gulf. The Arabian anticyclonic system and the Turkish COL system transport their moisture to the atmospheric river by passing through several atmospheric sources through cyclonic and anticyclonic gyres. The sources of moisture that feed the atmospheric river are located in three regions: tropical, subtropical and subtropical. Sources of moisture in tropical regions include the Arabian Sea and the Indian Ocean. Moisture sources in the subtropical region include the northern and central Red Sea and the Persian Gulf. The moisture of these sources is injected into the atmospheric river from the south, southeast and east through Arabi. Moisture sources in the extratropical regions (Black and Central and Eastern Seas), Mediterranean Sea regions) and subtropical (Northern and Central Red Sea) enter the atmospheric river from the west and northwest with the cyclonic circulation of COL. Considering that the Atmospheric River is fed by several moisture sources, its humidity has not decreased along the way even in the Arabian Peninsula.