عنوان مقاله [English]
Flood is one of the most damaging natural disasters that is always accompanied by economic losses and in some cases human casualties and with the highest relative frequency of natural disasters in the world (around 40%) causing extensive and even homelessness, and there have been a lot of migration. Compared to other countries in the world due to environmental diversity, Iran has a high rank in the crisis caused by natural disasters, of the 40 natural disasters in the world, 31 have occurred in Iran. According to the FAO report, Iran ranks 10th in the world in terms of talent and potential for natural disasters. Statistics show that not only has the number and severity of floods been increasing in recent years, but economic, social and environmental damage is also increasing. Population growth is the occupation of floodplains and inappropriate land use, including causes of flooding. Therefore, damage reduction and flood control are important priorities and require more attention and resource management to ensure sustainable development. In addition, severe climate change in the form of global warming has led to changes in temperature and precipitation patterns and climate change in most parts of the world. In this regard, human activities such as deforestation and grazing by livestock have destroyed the vegetation of forests, rangelands, and reduced the appearance of water intake in these areas, with little rainfall and large amounts of runoff. In order to prevent or reduce flood damage in one area, it is necessary to anticipate severe rainfall by taking specific measures and establishing a local flood alert and risk management system. The area reduced the severity of floods and their damages. In this regard, using synoptic analysis on meteorological maps, it is possible to identify the patterns leading to floods and to predict them before they occur and to minimize the damages. Therefore, in this study, the statistical and synoptic analysis of the flood system in the south and south east of Iran in January, 2020 was investigated. This study focuses on environmental circulation analysis method, so that synoptic patterns of this phenomenon are identified based on flood event. For the purpose of statistical and synoptical analysis of precipitation system in the south and south east of Iran on January 11-13, 2020, statistical data of precipitation were first obtained during the activity of this system. Then to investigate atmospheric patterns and their behavior, synoptic maps of sea level pressure, geopotential of 500 hPa, relative humidity of surface and level of 500 hPa, wind velocity at 850hPa, 700 hPa and 300 hPa,Omega and columnar precipitable water were analyzed from two days before the flood to one day after the flood. In this way, the synoptic pattern of the flood system was analyzed for four consecutive days at different levels of the atmosphere. Statistical analysis of the rainfall received from 11 to 13 January shows that during this period there was a wave of precipitation throughout the country which resulted in floods and floods in many areas, especially southern and southeastern areas of the country. According to the statistics analysis, the average rainfall in the mentioned period was recorded at 8.4 mm, which is an increase of about 4 mm compared to the same period (4.5 mm) Give. The highest rainfall occurred in Sistan and Baluchestan province in the period of 31.5 mm which is approximately 15 times its long-term average. After that, Gilan and South Khorasan province had the second and third highest rainfall with 20.7 and 15.9 mm, respectively. Also, the average rainfall during the operation of the system was 8.4 mm. The zoning of the percentage of precipitation deviation received in the system compared to the similar long-term average also shows that most of the changes are in the eastern regions of the country, especially in the southeast of the Iran, reaching more than 500%. According to recorded rainfall data in the south and southeast synoptic stations of the country, the highest cumulative precipitation within 24 hours was related to the two Qeshm (coastal) and Rudan stations in Hormozgan province with 176 and 222.8 mm, respectively. Precipitation is the highest 24-hour record during this system. These two stations had an increase in precipitation of 167.7 and 82.8 mm, respectively. Synoptic analysis also showed that on the day of precipitation (January 11st) a deep trough with north-south direction continued from the Caspian Sea to the southern part of the Arabian Sea, extending southward into the south and south-east areas of the trough region. The country should be positioned at the front of the trough and below the positive horizontal rotation zone, providing for the extreme instability and flooding in the area. Also on this day, the rule of a low-pressure center in south and south-east of Iran and two high-pressure centers on Afghanistan and eastern Turkey caused a strong pressure gradient in east and northwest of Iran. Due to the geopotential elevation map of Level 500 hPa this day, the low-pressure area and lower-level convergence deployments, especially the low-pressure convergence located in southeastern Iran and the high-pressure over Afghanistan and Pakistan in front of the deep middle slope and slope High pressure between low pressure and high pressure stations located in the region causes large volumes of moisture and heat to be transmitted to the lower surfaces, especially from the Indian Ocean and Oman Sea to poison.