Physical Geography Research
Year:2012 | Volume:44 | Issue:3 (81)|Papers Count:8

Introduction:Erosion is the process by which soil and rocks are removed from the Earth’s surface by natural processes such as wind or water flow, and then transported and deposited in other locations.Human activities have dramatically increased (by 10-40 times) and accelerated the rate of erosion globally. Excessive erosion causes problems such as desertification, decreases in agricultural productivity due to land degradation, sedimentation of waterways, and ecological collapse due to loss of the nutrient rich upper soil layers. Water and wind erosion are now two primary causes of land degradation; combined, they are responsible for 84% of degraded acreage, making excessive erosion as one of the most significant global environmental problems.

Introduction:Growth in our understanding of active tectonics and tectonic geomorphology during the past 25 years has made it clear that tectonic processes happen at a variety of scales relevant to human history. This fact has presented researchers with an important question that what is the impact of active dynamics of earth’s crust in continental region on human societies in both our past and future. A review of published studies shows that there are two viewpoints about the relation between active tectonics and humans. Some of the researchers emphasize the dangers of active tectonics for human beings. The other group of researchers believe that tectonic is an important factor in the evolution of humans, civilization, and the formation of ancient complex cultures.

Introduction:Within a synoptic weather, the classification of ambient weather conditions into categories is a useful tool for numerous climate impact applications.Air mass is a large and homogeneous volume of air which is adequately located over a certain area and captured properties of its below area. In order to form air masses, it is necessary that air remains stable in an area for a long period of time. Ultimately, general flows of air make them move. While moving and passing different regions, characteristics of air masses are changed, modified and also transformed into another air. A location’s climate follows air masses entering to that region and, reflects geographical conditions of that location. One of the objectives of synoptic climatology is to carry out synoptic categorization or to determine dominant air types (climate) in a location in a year. Air masses are generally categorized based on potential temperature and humidity. However, other criteria are considered as bases for their categorization.

Introduction:Some of phenomena have certain relationships which cannot be raised as correlation, but they considered as duality. Concept of duality is regarded when a phenomenon with another phenomenon is dual. Although each of these phenomena are independent in nature, there is a relationship between them. So, we will analyze the behavior of phenomena in relation to other phenomena.

Introduction:In arid and semiarid areas, dust storms occur frequently. When surface winds are strong, large amounts of sand and dust can be lifted from bare, dry soils into the atmosphere and transported downwind affecting regions hundreds to thousands of kilometers away. Dust storms are most commonly caused by strong pressure gradients which cause an increase in wind velocity over a wide area. For countries in and downwind of arid regions, airborne sand and dust presents serious risks to the environment, property and human health. In recent years, systematic research on dust storms has been carried out. Dust storm in the east of Asia, is quite well documented through the analyses of synoptic records over the past 50 years (Sun et al., 2001; Zhou, 2001; Chun et al., 2001; Qian et al., 2002; Natsagdorj et al., 2003; Kurosaki and Mikami, 2003; Shao and Wang, 2003). Sun et al. (2001, 10331) analyzed the synoptic reports over the 40years period between 1960 and 1999 and found that Gobi in Mongolia and north of China are major dust sources. In this paper, we identify the main sources of dust production, test forward trajectory technique and investigate characteristics of pressure patterns of dust events in July 2009 in Western Iran.

Introduction:Air pollution is one of the major anthropogenic related productions which has had direct or indirect impact on environment during past recent century. Tehran metropolitan is one of the polluted cities in the world, in such way that in 2010, 120 days out of 365 days, were much polluted with one or several polluted elements. The major aim of this work is to map air pollution of Tehran metropolitan using new technique and method of magnetometry of tree leaves. Application of magnetic measurement is known as a new advanced method in investigation of the magnetic mineral emitted in to the air in industrial area.

Introduction:The importance of atmospheric precipitation in human life turns it into one of the most common subject of various studies. Minimal changes in the amount and intensity of precipitation would face the communities’ social and economic infrastructures to serious problems. Even though these studies have yielded very precious results but in most cases atmospheric precipitation patterns were analyzed not only at a limited regional scales but also only for heavy precipitation (high intensity precipitation). However, synoptic weather patterns, creating precipitation or other atmospheric phenomena, are formed within hemisphere-scale pattern. Among them, blocking pattern is one of the most important large scale circulations.

Introduction:The Urban Heat Island (UHI) effect refers to the temperature rise of any man-made area. It is a phenomenon in which cities become warmer than the surrounding suburbs. In other words, there is a temperature difference between the cities and the area surrounding them. Generally, the UHI effect could be a result of excessive and unplanned growth of urbanization. The behavior of artificial urban texture in terms of absorption of short-wave and long-wave radiation, transpiration, releasing of anthropogenic heat, and blocking prevalent wind is significantly different from that of the rudimentary nature. Surface geometry on the other hand, decreases wind speed in urban regions which plays a great role in formation of UHI. As the energy balance inside a city alters, UHI intensity varies. This means that UHI intensity is not spatially and temporally similar in different cities.