Investigation on dynamical structure and moisture sources of heavy precipitation in south and south-west of Iran
- PDF / 1,786,185 Bytes
- 15 Pages / 595.276 x 790.866 pts Page_size
- 15 Downloads / 173 Views
ORIGINAL PAPER
Investigation on dynamical structure and moisture sources of heavy precipitation in south and south-west of Iran Hassan Lashkari 1 & Zainab Mohammadi 1 & Mahnaz Jafari 1 Received: 4 March 2020 / Accepted: 6 October 2020 # Saudi Society for Geosciences 2020
Abstract The purpose of this research is to study the structure and mechanism of heavy precipitation systems on the Arabian Peninsula and Iran and what is role of hot seas on providing moisture to these systems. To this end, precipitation data from 45 stations in the region during the period 1982–2017 were extracted. Based on local indices, the rainfall threshold of 30 mm was selected as the heavy rainfall criterion. By this criterion, 92 single-day systems with heavy rainfall were identified. By visual inspection of different atmospheric levels maps, one sample that comprised more than 80% of the samples were selected as the dominant model. The vertical structure and the moisture flux of this pattern were plotted in three boxes (system motion path). The results of this study showed that high humidity systems are supplied from three regions. In the first box (Sudan), the highest moisture advection in the lower troposphere comes from Intertropical Convergence Zone (ITCZ), the Indian Ocean, and the Arabian Sea; at second box comes from the Red Sea, Arab, and Oman; and the at third box comes from the Persian Gulf. The new finding of this research is the identification of a front line. This front line is caused by cold advection of polar side latitudes by a deep trough in the eastern Mediterranean and warm and humid advection of the southern warm seas, while so far it is thought that convection phenomenon to be the main cause of heavy rainfall and flooding in this region. Keywords Dynamical structure . Moisture sources . Heavy precipitation . South and south-west of Iran . Low-pressure system of Sudan
Introduction The climate of north-east of Africa is generally influenced by a low-pressure system in Sudan region with special features of tropical regions and different surface factors (El-Fandy 1946, 1948, 1950a, b, Johnson 1965). Remarkable results obtained from the previous researches in this region include the formation of low-pressure systems in north-east of Africa and the Red Sea. Prior researches suggested that these low-pressure systems are isolated cells from the Intertropical Convergence Zone (Solot 1950; Johnson 1965). Regarding the low latitude and the absorption of high levels of radiant energy, in some other studies, they have been considered as thermal lowResponsible Editor: Zhihua Zhang * Hassan Lashkari [email protected]; [email protected] 1
Department of Physical Geography, Faculty of Earth Sciences, Shahid Beheshti University (SBU), Room No 327, Tehran, Iran
pressure systems (Krichak et al. 1997). And other researchers believed that the convergent currents created in the region predisposes to the formation of surface low-pressure systems. Convergent currents are classified into two types: the first type includes the sout
Data Loading...
