جغرافیا و مخاطرات محیطی
سال:1394 | دوره: | شماره: |تعداد مقالات:8

Introduction: Dust storm is a natural phenomenon that occurs frequently in the arid and semi-arid regions all over the world (Alijani, 1997). Dust can affect soil fertility, forests, rivers, lakes, and marine ecosystems around the world (McTainsh et al., 2007). Therefore, soil erosion can lead to the loss of the minerals and organic matter of topsoil. Some elements of dust have also an indirect effect on absorption of other elements (Reynolds et al.2001). It is estimated that each year 2000 Mt dust is emitted into the atmosphere, 75% of which is deposited to the land and 25% to the ocean (Shao et al., 2011). The morphology and elemental composition of the particles can change alone the transportation in reaction to gasses and other particles in the atmosphere (Wang et al., 2007). Identification of the physical properties and chemical composition of dust aerosols is important to determine aerosol sources, mixing processes and transport pathways (Rashki et al., 2013). Chemical analysis of airborne dust can also characterize major and trace elements of airborne dust which is important for quantitative climate modeling, in understanding possible effects on human health, precipitation, ocean biogeochemistry and weathering phenomena (Goudie & Middleton, 2006)…

Introduction: As strongly accepted among climatologists, climate change is a result of human activities. There is disagreement about how to define climate change, because of tremendous difference of climate changes in scale, intensity and occurrence time in various regions. Recently there have been several observation analyses involving daily and extreme daily temperature trend and variability in regional and global scale. Analyses In global scale (Caesar & Alexander, 2005; Alexander et al., 2006; Brown, 2008) show an increasing trend in the lower end of the maximum and minimum temperature distributions with regional differences. For instance, i n south America, analyses showed a general warming trend in the region (Aguialar et al., 2005) also analysis results indicate no consistent change in the indices based on daily maximum temperature while significant trends were found in the indices based on daily minimum temperature (Vincent et al., 2005). Therefore in this paper, using gridded daily temperature data (Mean, maximum, minimum), we have analyzed the trend of the area which is affected by climate warming in Iran...

Introduction: In recent years, Desert Dust frequency has increased in the Global system. Due to lack of vegetation in the regions prone to dust, the earth’s surface air becomes warm enough in these regions, moves upward and causes a cold downward circular air flow when it collides with upper tropospheric winds. When these winds strongly hit the earth’s surface, they create dust storms (Xuan et al, 2004). Many studies from all around the world have been conducted on the source regions of this environmental phenomenon (Kai & Gao, 2007). The studies on Asian dust storms with sea sources during 2000-2002 showed 64% of storms originate from China seas and become more severe from west to east and carry dust on the land. Wang, Stein, Draxler, Rosa & Zhang (2011) studied sand and dust storms in 2008 and defined North Africa, Middle East, Mongolia, and north-west China with high frequency of dust phenomenon, using HYSPLIT Model. Shamsipour and Safar-Rad (2012), analyzed the July 2009 dust in the west of Iran. In the chosen sample, the Zagros hillsides contain the highest amount of pollutants. Also, the results indicate that the location of Naveh, upper-level divergence of 500 and forming a thermal low-pressure system on earth’s surface play the main role in flowing the dust toward Iran...

In general, Garmesh wind in Rasht province increases the temperature by 9°C and reduces relative humidity by 47%. The direction of prevailing wind during the Garmesh wind is Southern and its average speed increases by 2 m/s to 5 m/s. The highest frequency of Garmesh wind occurs at 09 and 12 UTC in December and January. The occurrence of this phenomenon substantially increases the horizontal visibility, so the sky would be clear in more than 40% of the cases.

Introduction: During the past decade, many efforts for investigating the relationship among air pollution and meteorological factors have been undertaken and some statistical methods have been proposed. Population increase and technological advancement were among the factors affecting creation and extension of air pollution in big cities, forcing large cities all over the world to contemplate measures to curb and prevent the spread of pollutants. Air pollution is emblematic of a wide range of impacts on biological, physical and economic systems. In recent years, air quality has been debated as a pivotal factor in materialization of the quality of life in urban areas, specifically in densely populated and industrial areas. In the present research, in order to evaluate air pollution in the city of Mashhad, eleven air-monitoring stations were used and several parameters for air pollution were studied. The main purpose of the research is to use a model which can establish a link between weather and pollutant factors as well as to identify climate factors affecting air pollution in the city of Mashhad and predict the density of pollutant gases using neural network and linear regression...

Introduction: While human habitation was formed as concentrated and stable communities, air pollution had become perceptible on human life. By passing of time and the improvement of thriving and particularly by the industrial revolution commencement, air pollution gradually has converted into an international issue, principally in the present times (Ghanbari and Azizi, 1388: 16). Whereas air pollution is one of the most significant risks to human; especially in metropolises, the investigation of its impacts is one of the primary priorities in climate researches. Meteorology cannot connive at atmospheric pollution. Nowadays, pollutant concentrations are developed threateningly by the urbanization growth and the improvement of living standards and industrial development. Human adds to the increase in air pollutants by their activities and make survival difficult for themselves and other organisms. Besides, they have applied changes in weather patterns of Planet Earth and environment and cause disorders in them. Meteorological conditions and physical and dynamic features alterations of atmosphere play a critical part on air pollution levels.

Introduction: Early frost in the autumn and late spring frost are the most common disasters related to the huge agricultural damages in West Azerbaijan province. Among 39 natural disasters in the world, 7 dominant disasters occur in this region and the frost has the first rank regarding the damage to the public sector and insurance industry in recent years. Based on several reports, early spring frost damage could reach to 25-100% of total production among orchard trees including almond, apricot and walnut. Considering the irregular and unscientific development of orchards in the past, therefor, determining of suitable sites (low frost risk) for crop production based on GIS is necessary. Probability and the risk of causing damage due to temperature differ depending on the time and year as well as plant sensitivity to temperatures below zero. Numerous studies have been done in the country and abroad to determine the probability of occurrence of frost. However, most of these studies have failed to consider the frost threshold temperature at which the plants are damaged. Determining the most probable occurrence of frost with a hypothetical risk in province of west Azerbaijan, which is also known as an agricultural poles in Iran is economically important by applying of the latest tools and geo-statistical methods and preparing spatial patterns of the frost dominated sites in the region are the main objectives of this paper...

Introduction: Considering the importance of Lake Urmia in the weather of northwest of Iran, the present study, using dynamic modelling and simulation, investigates the consequences of the drying up of Lake Urmia on the climate parameter of downfall…