A synoptic analysis of the northward displacement of the Mediterranean low-pressure tracks in Iran

Mediterranean low-pressure systems are among the most important rain-producing systems for Middle east and Iran during the cold half of the year. In this study, nearly ۲,۴۰۰ weather-maps at a level of ۱۰۰۰ HPA were downloaded from the NOAA website. The identification of the stages of these low-pressure systems, including their formation, strengthening, and tracking, was carried out over two decades and in four representative months of the seasons, including November, February, May, and August, respectively. The aforementioned identification was divided into two categories: low-pressures were towards Iran (LTI) and low pressures were towards other lands (LTO). Initial results showed that ۴۱۸ low-pressure systems formed and moved over the Mediterranean Sea between ۲۰۰۳ and ۲۰۲۲. Of the ۴۱۸ recovered tracks, ۸۸ ones were LTIs and ۳۳۰ ones were LTOs. Meanwhile, the ۲۱% share of LTIs has been decreasing at a gentle rate over the last two decades. Marking the tracks on the base maps at three scales of months, years, and decades showed that these systems have diverged towards the east on three pathways, from the western and central northern Mediterranean areas. Pathway No. (۱) passed through the southeastern part of the Hijaz in the first decade, but in the second decade it turned northward and crossed the southern provinces of Iran. Pathway No. (۲) passed through the central lands of Iran in the first decade, and in the second decade, it left Iran with a significant northward turn, crossing the middle of the Caspian Sea towards the plains of Turan (Central Asia). Pathway No. (۳) passed over the Black Sea at the highest latitudes during the first decade, but in the second decade, it went out of the map frame north of this sea. Overall, the decadal patterns showed that most of the LTIs and LTOs tracks were extended to higher latitudes during the years ۲۰۱۳ to ۲۰۲۲ (second decade) compared to the years ۲۰۰۳ to ۲۰۱۲ (first decade). Therefore, given the persistent and mild nature of precipitation resulting from Mediterranean systems, it is believed that as more southern systems such as Sudanese low-pressure systems replace them, it will become more difficult for planners to store and manage Iran's water resources.

کلیدواژه ها:

Mediterranean Sea ، low-pressures ، northward displacement ، Iran