The Iranian plateau formed by the active tectonics of the Alpine-Himalayan belt, is situated between the Eurasian and Arabian plates. The plateau is considered as one of the most seismically active regions in the world and is faced with different earthquakes each year. Active tectonic conditions, different faults and seismic sources and a large population in earthquake-prone areas makes it necessary to perform more considerations and scientific studies in order to analyze the seismic hazards and risks.
In this paper, different aspects and effects of the Iranian seismicity has been determined. In order to review the status of seismicity and distribution of earthquakes in Iran, we need first to consider the tectonic setting, structural environment and the active faults of the country. To date, there have been some different studies to divide the the seismotectonic setting of Iran into different seismic zones which are explained in this paper briefly. Moreover, the seismicity and most destructive past earthquakes in the Iranian plateau and distribution of earthquakes are shown.
One of the most important tools in studying earthquakes is to perform continuous recording and monitoring of the seismic event and ground motions which is implemented using seismic and strong motion networks. The systematic networks have been set up within the country and are working and responsible for data collection and monitoring of seismic events permanently. These networks including the Iranian Seismological Center (IRSC), broadband seismic network of the International Institute of Earthquake Engineering and Seismology (IIEES) and strong motion network of the Road and Housing and Urban Development Research Center (BHRC) are also introduced in the current study.
Given the high seismicity rate in Iran and rapid development and growing of the populated cities and buildings on seismic hazard prone areas, attention to seismic hazard and risk assessments has been become as a particular issue that should be addressed carefully. Therefore, seismic hazard analysis and estimation for the constructions of human structures has become an enforcement for which several seismic regulations and codes have been defined. In this regard, deterministic and probabilistic seismic hazard methods have been developed as the two most important techniques. The deterministic method is a conservative approach that is mostly used to determine the highest level of strong ground motion (acceleration) for a special site (such as dams and power plants). On the other hand, the probabilistic method provides probabilities of different strong ground motion levels considering different uncertainties and the useful life of a structure.
In addition, considering the level of seismic hazard in a region and its population can lead to risk assessment, vulnerability and resiliency of the human societies. Thus, parallel to seismic hazard and risk analysis, it is so important to conduct crisis management, reduce efforts and a continuing assessment of the situation in the country. In the present study, problems and challenges facing the crisis management, as well as urban distressed areas are mentioned.
Regarding the existence of constant threat of natural disasters, especially high risk of earthquakes, there is a serious need to conduct more scientific researches in various fields, including detailed research on various aspects of seismology in Iran, retrofitting of constructions, crisis management and disaster risk reduction. To achieve this purpose, we need a scientific network in Iran. There sould be several experts and organizations as the members of this network who are able to understand and control the earthquake effects on the society. Necessity of such a scientific network is due to that it is impossible to take efforts in order to reduce the earthquake risks without a holistic perspective and earthquake data completion.
In this regard, we need significant infrastructures in terms of human resources and technical cooperation to motivate a set of organizations, universities and research institutes. The responsible organizations such as geological survey of Iran, National Cartographic Center of Iran, meteorological organization, Institute of Geophysics of the University of Tehran, International Institute of Earthquake Engineering and Seismology, Road and Housing and Urban Development Research Center, National Disaster Management Organization, Red Crescent Society of the Islamic Republic of Iran, as well as universities and NGOs must work together to make it possible to review and integrate the existence potentials and to share the information and data of the earthquakes in Iran and define various response scenarios faceing natural disasters, especially earthquakes.
We can identify the flood not only considering circulation pattern in occurring day but also by studying circulation pattern a few days before fresh event. This subject has mutual approach. In one hand, it indicates that circulation patterns which were before flood event have important role in determining the conditions and moisture content of studied area and playing the fundamental role in few coefficient of region because it determines the previous moisture. On the other hand, it indicates that we should tracking the rain-genesis synoptic systems from source to end place of their activity for studying floods and their meteorology factors which have created them. By this way, we can acquire more comprehensive recognition about the relationship between circulation pattern and floods. In the other words, the identification of synoptic patterns that have created the flood reveals not only the mechanism of their emergence but also is useful for prognosis and encountering with them. The extensive researches have been accomplished about Inundation in the world and Iran, but Iran haven’t much antiquity about synoptic researches. For foreign researches, we can name researchers such as Hireschboeck (1987), Kutiel et al(1996), Komusce and et al (1998), Krichak and et al (2000), Rohli and et al (2001), Kahana (2002), Teruyuki Kato(2004), Ziv and et al (2005), Carlalima and et al (2009). The numerous researchers have studied the Inundation climatology in internal of country such as Bagheri (1373), Ghayour (1373), Kaviani and Hojatizadeh (1380), Moradi (1380), moradi (1383), Mofidy (1383), Masoodian (1384), Masoodian (1384), Hejazizadeh et al(1386), Parandeh Khozani and Lashkari (1389). In this research, we considered the heavy precipitation of Azar 1391 in southwestern of Iran that resulted in flood phenomenon in the cause and effect manner so that can do necessary prevention actions before occurring the flood for preventing the probable damages and optimal use of precipitations by forecasting the patterns that have created the flood.
In this synoptic study, we need to two database: one group is variables and atmospheric data consisting of geopotential height of 500 hpa level (in meter geopotential), zonal wind and meridional wind (in m/s) and special humidity (in gr/kg) during this times 00:00, 06:00, 12:00 and 18:00 Greenwich in 0-80° northern and 0-120° eastern with local resolution of 2.5*2.5 Arc that have been borrowed from database of (NCEP/NCAR) dependent to National Atmosphere and Oceanography Institute of USA, and other group is daily precipitation data of region rain gauge stations during 4-8th Azar of 1391 (24th November – 28th November 2012). In continuation. By applying the environment- circulation approach, we took action to drawing circulation pattern maps of 500 hpa level, thickness of atmosphere patterns of 500-1000 hpa and moisture flux convergence function from 4-8th Azar of 1391 (that for calendar, conform with 48 hours before beginning the showery precipitation until ending the storm activity) by using data which obtained from database of NCEP/NCAR and the synoptic conditions of above flood have been studied and interpreted in the region.
Flood is one of the most destructive natural hazards that have imposed and impose many damages to people during the history. Hence, the final aim of this research is to explain the key interactions between atmosphere and surface environment and in other words exploration of the relationship between circulation patterns leading to the flood generating precipitation in the southwestern of Iran for forecasting the time and intensity of showers occurrence that lead to flood. For this purpose, by applying environmental-circulation approach, the circulation patterns identified and studied which resulted in flood generating precipitation. The result of this research indicated that torrential precipitations in the region have formed the deep trough in days 4-8 of Azar on the east of Mediterranean and the studied region placed in the east half of this trough that is the location of atmosphere instability. At same time, thickness patterns, indicate the flux of cold air from northern Europe to lower latitudes and spreading the warm air of north of Africa to latitude 50° northern. As a result we expected the frontal discontinuity in the encountering place of these two air mass. Analysis of the moisture flux convergence patterns also indicated that torrential precipitations were the result of moisture flux from Mediterranean and Persian Gulf; and Red Sea and Arab Sea taken into account as reinforced sources.
Due to the growth of industries and factories, deforestation and other environmental degradation as well as greenhouse gases have been increasing on the Earth's surface in recent decades. This increase disturbs the climate of the Earth and is called climate change. An Increase in greenhouse gases in the future could exacerbate the climate change phenomenon and have several negative consequences on different systems, including water resources, agriculture, environment, health and industry. On the other hand to evaluate the destructive effects of climate change on different systems, it is necessary to initially study the area affected by climate change phenomena. One of the most important effects of climate change on water resource is Drought. On the other hand, one of the most serious consequences of climate change is how it will affect droughts and water resources.
Drought along with warmer temperature and less precipitation will threaten the water supplies for the crop irrigation, which will directly reduce the production of crops.The climate of the 21st century will very likely be quite different from the climate we observed in the past. The changes will continue to be large in the future period with increasing carbon dioxide emissions. Analyzing and quantifying the signal of climate change will be much in demand considering the above sectors, which are highly relating to the sustainability and human living.
In the past several decades, global climate models have been used to estimate future projections of precipitation [Intergovernmental Panel on Climate Change (IPCC), 2007], and have led to future estimation of drought, to quantify the impact of climate change and comparing the duration and intensity of droughts under future climate conditions with current climate by using Atmospheric-Ocean General Circulation Models AOGCMs to predict future Precipitation. Global circulation models namely, coupled Atmosphere-Ocean Global Climate Models (AOGCMs) are current state of the art in climate change research. in This study aims at investigating the impact of climate change on droughts conditions in Iran using the Standard Precipitation Index (SPI).
The precipitation time series have been used for the estimation of Standardized Precipitation Index
(SPI) for three timescales, 3, 12 and 24 months, for the region. The outputs of HadCM3-A2 and A1B were applied for the assessment of climate change impact on droughts. One of the major problems in using the output of AOGCMs , is their low degree of resolution compared to the study area so to make them appropriate for use, downscaling methods are required. In this study we have used lars WG for downscaling monthly average of rainfall of AOGCM-HadCM3, and The HadCM3 outputs were downscaled statistically to the study area for a future period 2011-2040.then, was evaluated by the coefficient of determination (R2) between observed and downscaled data. A method has been used for the estimation of annual cumulative drought severity-time scale-frequency curves. According to the rainfall results, in the 2011- 2040 period rainfall would decrease to compared to baseline period in the study area.
The SPI time series were estimated (2011-2040) and compared with the respective time series of the historical period 1961-1990. Results revealed that there are decreases in the frequency of severe and mild droughts for the three examined SPI time series while there are increases in the duration of moderate droughts. This implies that droughts will be a concern in the future during the growing season (for the dominant crop) which should be considered in water resources management. specially in the west station of Iran.
Also, these frequency ratios were mapped by GIS on study area. Results showed that generally in the future periods, frequency of droughts ratio of three months drought time- scale will be increase in the North, North West and some parts of the south Alborz mountains and, The Ratio of long ( 24 months) drought for scenario A2 compare to the current climate shows increasing drought in the parts of the North khorasn, sistan and baluchestan and kerman provinces and parts of South West of Iran. scenario A1B shows increasing drought in the parts of the East of Mazandaran , Tehran , Horozgan and parts of Fars and Yazd provinces.
Finally ,further more analysis of drought, AWCDS-Timescale-Return Periods computed. These curves integrate the drought severity and frequency for various types of drought. The AWCDS time series were estimated
for basic period and 2011-2040 under scenarios A2 and A1B. The comparison indicated the three types of drought intensity increases for the three examined SPI time series in the South East of Iran.
Identification and synoptic analysis of the highest precipitation linked to ARs in Iran
Abstract
Atmospheric rivers (ARs) are long-narrow, concentrated structures of water vapour flux associated with extreme rainfall and floods. Accordingly, the arid and semi-arid regions are more vulnerable to this phenomenon. Therefore, this study identifies and introduces the highest precipitation occurred during the presence of ARs from November to April (2007-2018). The study also attempted to demonstrate the importance of ARs in extreme precipitation, influenced areas and identifies the effective synoptic factors. To this end, integrated water vapour transport data were used to identify ARs, and documented thresholds applied. AR event dates were investigated by their daily precipitation, and eventually, ten of the highest precipitation events (equivalent to the 95th percentile of maximum precipitation) associated with ARs were introduced and analyzed. The results showed that most ARs associated with extreme precipitation directly or indirectly originated from the southern warm seas. So the Red Sea, the Gulf of Aden and the Horn of Africa were the major source of ARs at the time of maximum IVT occurred. Synoptically, seven AR events formed from the low-pressure Sudanese system and three events from integration systems. The subtropical jet was the dominant dynamic of the upper troposphere, which helped to develop and constant of ARs. Moreover, the predominant structure of jets had a meridional tendency in Sudanese systems, while it was a zonal orientation in integration systems. The intense convective flows have caused extreme precipitation due to the dominance of strong upstream flow besides having the highest moisture flux. The station had the highest precipitation has been located in the eastern and northwestern region of the negative omega field or upstream flows.
Keywords: Identification and synoptic analysis, highest precipitation, Ars, Iran.
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