Introduction

Most of the Middle East is made up of deserts with little rainfall, but here the mountains particularly the Zagros mountain range, have produced areas with sufficient and even high rainfall. On the western slopes of the Zagros mountain range, in the northwest, is one of these high rainfall regions. According to the research, this area is known as the northwest Zagros wet region and includes a part of the mountainous border strip in northwestern Iran and it also includes the mountains of northeastern and northern Iraq. Therefore, considering the importance of precipitation in this region, identifying the main sources of moisture supply of precipitation systems will provide new information on the knowledge of climatology in the region.

Methodology

The data from Baneh synoptic station has been used in this study as a sample of the area in order to identify the systems with significant rainfall in the winter season (2001-2020). Dynamic computations of moisture flow divergence/convergence were carried out after determining the necessary rainy days, and matching humidity maps were created. Following that, these values were numerically calculated in the vicinity of the Arabian Sea and the Mediterranean Sea.

Results

Three humidity patterns related to the research areas were discovered.

The Arabian Sea's humidity pattern.

The Arabian Sea is the primary supply of humidity for the rainfall systems over this pattern (14 days), and the Mediterranean Sea has a very minor influence. The Arabian Sea plays a major role in humidity transfer, as evidenced by the average of humidity flux divergence on this pattern being -6.79*(10^-5g.kg.s¹) in the Arabian Sea region and -0.3*(10^-5g.kg.s¹) in the Mediterranean Sea region (Table 1).

The Arabian/Mediterranean Sea humidity pattern

Nine days were discovered in this pattern. In contrast, the Mediterranean Sea's contribution to the region's rainfall has increased, even though the Arabian Sea still contributes more moisture to the region than the Mediterranean Sea does. Average of Humidity flux divergence on this pattern in the Arabian Sea region is -5.74*(10^-5g.kg.s¹), whereas it is -1.78*(10^-5g.kg.s¹) in the Mediterranean region, clearly demonstrating the Mediterranean Sea's expanding importance in moisture transport (Table 2).

The Mediterranean Sea's pattern

Six days in this pattern were found. The Mediterranean Sea is the primary
 supply of moisture for the rainfall systems over this pattern and the Arabian Sea has a very low influence.
 
4.Discussion
Results analysis reveals that when western winds wave enter the research location, the north of Iraq and the northwest of Iran are where the east of trough is situated. The Arabian Sea (during an anticyclonic circulation) and the Mediterranean Sea (during a cyclonic circulation) both frequently transmit humidity to the front of the trough in the low levels of the atmospher, and receives heavy rainfall. Three humidity patterns were found in this area. In the Arabian Sea's humidity pattern. Strong cores of humidity flux divergence are created in the lower layers of the atmosphere above the Arabian Sea; The majority of the rain's humidity comes from this precipitation, which is initially transported to the Arabian Peninsula's core regions before traveling south-north to northern Iraq and the western edge of northwestern Iran. And just a very little amount of humidity from the Mediterranean Sea is involved in this pattern. In a combined pattern over the Mediterranean and Arabian Sea. Strong cores of humidity flux divergence over the Arabian Sea, just like in the previous pattern, propel the humidity transport flow in front of the trough. And the primary source of moisture for rainfall is Arabian Sea, Additionally, over the eastern and central parts of the Mediterranean Sea, humidity flux divergence cores have developed. This outperforms the first model in strength. And during the cyclonic wind circulation, this humidity is moved to the front of the trough. They also produce rainfall in the area, following the pattern of the Mediterranean Sea, with the assistance of the Arabian Sea's moisture. Nevertheless, throughout the Arabian Sea, there are still significant and powerful centers of moisture flux divergence. However, this moisture does not get to the northwest, humid Zagros region. And the Mediterranean Sea is the primary source of moisture for heavy precipitations.

Conclusion

Lastly, the wet northwest part of Zagros receives considerable rainfall due to the Arabian Sea's substantially greater transfer of moisture from the Mediterranean Sea. and three patterns of humidity were found to be responsible for the region's excessive rainfall: a) the Arabian Sea; b) the Arabic/Mediterranean Sea; and c) the Mediterranean Sea.