فصلنامه مطالعات جغرافیایی مناطق خشک
پیاپی 30 (زمستان 1386)

One of the most important environmental challenges which exists in the Middle East and Iran in recent years is the phenomenon of dust. As regards the Western half of Iran is in proximity to large deserts and continually effects the country deserts dust and specially that western half and also the unpleasant effects that these dusts have on environment and people health; so the purpose of this study is the use of Combined method (E-synoptic satellite) for exact recognition of this environmental risk. In this study Terra / MODIS satellite images for dust event of 1 July 2008 West of Iran and the data of Nova Organization database includes: Geopotential height. (HGT) 500 HPa level, the condition of Sea Level Pressure (SLP) and the circuit and Meridional wind components from NECP website have been used. Quantitative indicators of dust detection on satellite images includes NDDI, BTD, BTDI and LRDI indicators, visual dust detection indicators includes false and true color combination and false color combination patterns. The results of applying the quantitative indicators to detect dust on MODIS images showed that the dust indicators and creating the false color image so that it can detect the areas covered by dust directly for dust detection of Iran on MODIS images has enough and good ability. Also the review of synoptic weather map for July 1 showed that the establishment of a low pressure system on Iraq and the south of Persian Gulf and the coordinated deep Landing effect on ascendent area at the same time with Azores high pressure weakens provides the perfect background for dust transfer to the area atmosphere.

The dam, as one of the hydrological structures, has imposed to rural areas many debates and problems on population deployment, the type and quality of livelihoods, and how to exploit natural resources such as water and soil. Recognizing and analyzing these effects in describing the unsustainable rural development process and the necessity of its transformation with regard to the dominant position of the villages is very useful. Accordingly, the principles of sustainable development are the theoretical basis of this research. In this study, the Alavian Dam in the Sufi Chai basin of Maragheh city and in the catchment area of Lake Urmia has been considered in line with the overall objective. The main objective of this study is to investigate and analyze the relationship between dams construction with unstable conditions in affected villages, as well as to provide appropriate solutions for managing resources in the Sufi Chay Basin. The type of research in terms of the purpose is an applied research, and is based on the method of the research is a descriptive-analytic research. In order to conduct a real analysis of villages affected by the dam, according to different characteristics, from a total of 59 villages in the basin, 44 villages were selected as samples. The statistical population of the study is 18669 households and 67553 people. The sample was computed using Cochran's formula of 386 households and finally increased to 433 households in order to increase the reliability of the sample. According to the one-sample t-test, the effects of the dam on economic, socio-cultural and environmental-physical variables have been evaluated at an unsustainable level. Based on the results of the structural equation model, the domains that were the most insensitive factor in the three studied areas,
Therefore, the development and implementation of an integrated and complete management plan for Sufi Chay watershed resources has been proposed to moderate the negative impacts of the dam.

Urban sprawl is considered as one of the well-known patterns of urban expansion, which means uncontrolled physical expansion of cities on agricultural land or undeveloped surrounding areas. What today is known as sprawl describes scattered and low-density urban expansion. Patterns of urban sprawl expansion could have adverse consequences, such as increasing share of open spaces and urban fragmentation, reducing population density and social segregation, inefficient use of land and imposing staggering costs on urban infrastructure, eradication of farms and the environment, increasing the demand for cars and consequently increasing air pollution and reduced social interaction. Land use planning is necessary to control and reduce the negative impacts of this type of expansion.
One of the factors affecting the physical expansion of urban sprawl is land and housing policy at national and local level that is applied in the form of assignment of state lands to build residential and industrial estates, policy on agricultural land use change to residential area, determine building density and pattern of urban land fragmentation.The main objective of this study is to evaluate the role of land policies on the urban sprawl expansion in Sabzevar, Iran, in the past few decades.
  In the present descriptive-analytical research, data required were collected mainly through documents from various organizations and analyzed using quantitative models like Holdren and Entropy methods. In addition, maps for physical expansion and growth in different previous periods were prepared to demonstrate the expansion of the city in graphical form using existing maps and aerial photos or satellite images via Arc GIS software.
  The city of Sabzevar in the last half century under the influence of natural population growth and migration of villagers with varying degrees of intensity in different periods has seen dramatic growth of the population, so that the population of Sabzevar has been 7.98 times from 1956 to 2016. In contrast, the area of the city has been growing faster than its population, so that its area has been equal to 18.15 times in the same period. This imbalance between population growth and the area in each period indicates the predominance of horizontal growth and urban sprawl. Comparison of increasing the urban area and the state land assigned areas show that a total of 2959 hectares added to Sabzevar between 1956 and 2016 have been about 31.55% because of the land assignment policy and 19.13% the result of informal settlements and villages annexed to the city. The most important thing about this area is that almost 100% of these lands are in areas that have been assigned directly by the government, or have been prepared by the government, and then assigned to the residents. Thus, the highest rate of urban sprawl can be seen in the directions that the government has had a direct role in its establishment. Therefore, the land assignment policy by allocating around 40% of the area added to the city limits has acted as the most important factor in the physical expansion of the city of Sabzevar.
The results of the calculations of the Holdren model demonstrated that population growth from 1956 to 1986 had a larger share in the urban area changes, so that the share of population changes in the period of 1976 to 1986 was achieved 98% and 0.02  per capita share of changes. However, this trend in the two next periods, i.e. 1986 to 1996 and 1996 to 2016 has been reversed and the share of changes per capita has surpassed the share of population changes. In the period of 1986 to 1996, per capita share was 68% versus 32% population changes and in the period of 1996 to 2016 was 59% versus 41%. This is due to the impact of land attached to the city through the lands vested in the form of land preparation project in Tohidshar and the incorporation of surrounding villages, including Kelate Sifer, Saleh Abad and Ghalee No Dehraz.
  Investigate the process of changes and patterns of urban physical expansion, and identify and analyze the effective factors are important for two reasons. Firstly, urban scattered and uncontrolled horizontal growth leave the inevitable consequences and sometimes undesirable on the economic, social and ecological aspects of the city. Secondly, analysis of the physical expansion process helps to more accurate planning to control and systematic guidance of expansion. Among the factors affecting the horizontal growth of the city of Sabzevar in the past few decades, land and housing policies have had a significant role in the city's physical expansion in certain directions. Thus, about 40% of the area added to the city in the last half century has been caused by the state land assignment policy. Discontinuous tissue formation in Tohid town was one of the obvious consequences of the policy that took place followed by the land assignment in the preparation project.
The assignment of the lands that took place in relatively large segmentations with an area of 250 square meters on average affected the physical expansion and construction of the city in the past two decades in several ways.
Firstly, this policy accelerated the horizontal expansion than the population growth. Secondly, the fact that these lands have been usually fragmented to regular segmentation and with predicted access network, urban expansion on these lands has a regular and chess-like form. Thirdly, the land assignment policies, particularly in the preparation project, led to the establishment of a new pattern of physical expansion in the form of urban discontinuous expansion, which can identify outlines for future expansion of the city.
In addition to the factors mentioned above, the annexation of villages and illegal settlements to the urban area in recent decades has had a significant impact on the direction and extent of physical growth of Sabzevar .

Climate change, as one of the most important global challenges, has focused on the minds of many scholars, scientists, planners and politicians. Indeed, global warming, melting of polar ice masses, rising water levels in the oceans, and its similar phenomena have led climate change to become the special attention focus of scholars and scientists in recent decades. Since temperature is a key element in the formation of the climate, and its changes can alter the climate structure of each region, therefore, studying the trend of temperature in different temporal and spatial scales has a large part to be climatological research. In fact, temperature as one of the most important and determinants of climatic elements is a suitable index for tracking climate change. Recent studies on climate change also highlight the centrality of temperature variations in these studies. In this regard, numerous researches has been carried out on the trend of global and regional average temperature increase, and the identification and analysis of the behavioral patterns of temperature has been considered by different methods in numerous studies. Here, we can be mention researchers such as Willett(1950), Yue & Hashino(2003), Feidas et al(2004), Bani-Domi(2005), Arora et al(2005), Turkes et al(2007), LaDochy et al(2007), Dhorde & Gadgil(2009), Chaouche et al(2010), LukoyeMakokha & Shisanya(2011), Toros(2011), Cordero et al(2011), Nayak & Mandal(2012), Safari(2012) and in Iran, Kaviani & Asakereh(2001(, Azizi et al(2004), Masoudian(2005), Ghayour & Montazeri(2005), Asakereh(2007), Massoudian et al(2008), Akbari & Masoudian(2009), Hejazizadeh & Parvin(2009), Massoudian & Darand(2010) and Montazeri(2011). Since the identification of temperature behavior and its changes is very important for management and planning, this research seeks to evaluate and analyze the variations of maximum and minimum monthly temperatures in Iran plateau. In this regard, statistical methods are considered useful and effective in describing these changes.
  In this research, the data of CRU database with resolution of 0.5°×0.5° geographical longitude and latitude during 64 years during 1951- 2014, have been employed to analyze  the trend of maximum and minimum temperature changes in Iran plateau. This data is available on the site's website at (https://crudata.uea.ac.uk/cru/data/hrg/) in the nc format. For data processing and extraction of this database, internal functions were used in MATLAB software. In order to extract data on Iran, the inpolygon function was used and the ncread command was used to read the data. Then, the mean monthly minimum and maximum temperature matrices, were constructed on Iran plateau. The dimensions of each of these two matrices were 768 × 2400, with rows representing the months and columns, representing spatial pixels. Then, using programming in MATLAB software, each month of the year, they were arranged in separate matrices, and the Mann-Kendall nonparametric test was applied to the data in order to detect the temperature trend.
  The results indicate that in all months of the year, maximum and minimum temperature of Iran plateau have increasing trend, but this trend is more pronounced in the hot months than in the cold months; in summer, more than 90% of the area has a rising trend of minimum temperature. At the same time, in the hot months of the year, 65-85% of the study area is also evident increasing in the maximum temperature. In the hot months of the year, the study area is under the domination of Azores subtropical high pressure, which causes predominance of the dry and warm weather on Iran plateau. In the months of April, May, June and July, there is no decrease trend in any part of the region. The least extent of temperature increasing trend observes in January, February and December.
  The results of this research indicate that in general, the maximum and minimum temperature of the Iran plateau has an incremental trend, and the temperature decreasing trend is negligible. Also, it has been revealed that increasing trend of temperature in hot months have high extent. The least extent of trend areas observes in January, February and December. Totally, the results of this research indicate that increasing trend of temperature observe, not only in Iran but also on all of Iran plateau, that this temperature increasing together decreasing trend of precipitation in recent years can result unpleasant consequences in this region. Thus, the increasing trend of temperature along with the reduction of precipitation in recent years is a serious danger to residents of this important plateau, including Iran. The results of this research appear to have strong evidence of the continental pattern and the prevailing warming of the Iran plateau.

Nebkhas, as one of the Eoelian Landforms in dry and semi-dry areas, have significant influence in controlling aeolian erosion and the environment stability. The main question of this study concerns different morphometry of nebkhas in two neighbor sites in Daranjir playa and the main factors which control these landforms. area special properties, the variety  of  hydrogeology properties, and the locality difference of nebkha morphomrtry introduce the  hypothesis  which hydrogeology properties have direct influence on nebkha morphomrtry. To attain this aim, remote sensing techniques, field data and geochemistry analysis have been used. Therefore, initially two sites which had  nebkha different vegetations were detached. In the next stage, nebkhas morphometry parameters in each site were measured. Thus utilizing hand auger, 8 bores were dug  with an average depth of 2.60 meters and sediment samples were collected.  The dig with hand  auger was achieved to Water table (an average 2.06 m) and was measured Water table for each bore. In addition, in each bore 300 millilitres of water was collected for chemical analysis through water sample collector device. Altogether, 46 sediment samples from the first site, 58 sediment samples from the second site and 8 water samples from eight bores were collected. After transferring the samples to geomorphology laboratory, the chemical analysis of water samples was carried out through a multi parameter device, version HI9811-5. Following that, by taking the saturated paste of sediment samples, the amounts of TDS, EC, pH were measured. The results of examinations on the qualitative nad quantitative features of the groundwater indicated that the average of ground water depth, TDS, and EC are respectively 1.69 m, 18850 ppm, 37750 µS/cm in the first site and 2.44m, 27500 ppm, and 54950 µS/cmin the second site. The chemical analysis of sample sediments indicated that the salinity of the sediments is influenced by the depth and quality of ground water, respectively. Overall, the findings show that the hydrogeology properties of the examined sites are not only the main factor in the formation  of Nebkhas, but also in control of the morphometric properties of Nebkhas.

The territory of central Iran is now affected by the hot and dry climate. But, several evidences, such as the extreme erosion of running waters, huge alluvial fans, wide alluvial terraces, and flood deposits indicate colder and wetter climate in the territory (Ghahroodi Tali, 2011: 3).
The rivers belong to the most important parts of the sedimentary basin. In fact, the rivers are one of the existing elements of the continental perspective. Based on their sizes, the riverine sediments are deposited in different parts of the river (Opreanu et al, 2007: 23). Alluvial landscapes are very complicated because of the discontinuity in vertical sequence that are controlled by various factors (climate, geology, geomorphology, and human), and it may be difficult to interpret sequence sequences. Even, the interpretation of the sequences may become difficult. By studying the particle size distribution of the deposited sediments along the rivers, such as the alluvial basin, we can gain important information about the particle granulation, the shape, size, slope, and elongation of the sediments (Randel et al., 2006:58).
The particle size of the sediments, showing the external and inherent conditions of the environment, which are a reaction to the geomorphological and climatic changes, show the morphodynamical balance of the sedimentary environment (Geupta and et al, 2002: 239). By selective sorting of the particles, due to their different transfers, we can identify the sediment phases (Solis-Castillo, 2013:10). This is especially evident in the mineral characteristics, such as their concentration, and shapes, and the particle sizes. Hence, sorting these characteristics can indicate the paleo-sedimentary environments, and the origin of the sediments (Komar, 2007: 10).
This study aims to rebuild the original environment and the paleo-sedimentary conditions in Meyghan plans by the help from sedimentary basin evidences of Gachalan seasonal River (Northeastern part of the basin). In this study, it has been tried to reconstruct the processes of Meyghan Basin, by using field observations, sampling, and doing granulametrical Morphoscopy, XRD, and XRF tests to analyze the sedimentary samples of alluvial basin Gachalan, in the Southeast of Meyghan plans. To analyze the Paleo conditions of Meyghan basin, firstly, Geochalan River, in the Northeastern part of the basin was selected. Then, by the help from the digital elevation model of the district, the exact pathway of the river was extracted. Next, on field observations, 12 sedimentary samples were gathered from the riverine level. Granola-metric studies and Morphoscopy and XRD, and XRF tests were performed on the samples. According to Folck’s classification, the studied sedimentary samples were put in the groups of slightly gravelly sand to sand gravel. The interpretation of the statistical parameters from the granulation of the sediments showed that: except for samples 7, and 12, which had average sorting (index of coast sediments), all other sediments had poor sorting, which is an attribute of riverine sediments. None of the samples showed their sorting is less than 0.8. This indicates that, the only dominant process of transferring the sediments in the studied layers was an aquatic process (Khanbabaee et al, 2016: 141). Poor sorting, also, indicates that the sediments have different origins. Tilting curves of layers 2, 1 and 5 were toward coarse particles, and other layers inclined to fine particles.
XRD and XRF tests showed that; in A and E sections, quartz mineral had the highest frequency. Also, in 2 and 3 sections, calcite mineral had the most frequency. In 2, 3, 4, and E sections, the amounts of Hematite mineral were observed to be increasing. The presence of these minerals confirms the occurrence of weathering and indicates that the above-mentioned sections of the sediments have been periodically out-of-water. The presence of Magnetite and Hematite in the layers shows the presence of weathering and oxidation more or less in all the sections (except section 1). The presence of some amounts of the heavy mineral of Magnetic in section 2 shows the sedimentary origin of quartz type, especially meta-Quartzite, Biotite, and Mesquite type.
The ratio of Al2o3/SIo2 more than 5 or 6 in the sediment stones is indicative of high sediment maturity (Roster et al, 1996: 14). The ratio in the samples of the studied area is averagely equal to 4.37. It is indicative of medium sedimentary maturity of the studied area. Among them, the sediments of sample A with 3.62, and the sediments of 3 samples with 5.01 have the minimum and maximum maturity, respectively.
By calculating the ratio of aluminum to tantalum, the amounts of the studied samples equaled averagely to 15.2, which we put than in the class of intermediate plutonic stones. To calculate chemical weathering, the Culers Index was used (Cullers, 2000: 150). The closer the index is to 50 and closer to 100, indicating more weathering in the region of origin. The value of this index for the studied region varied from at least 19.6% in sample c to a maximum of 27.54% in sample 1, indicating medium and low weathering in the source region in all periods. formation of volcanic facies in the era of Chromin (the end of the Quaternary end) in the Gachalan river basin and the basaltic andesitic masses caused by the occurrence of the main Pasadena's phase the Sahand-Bazman belt caused the andesitic-basaltic rocks to provide the majority of sediments transported by processes Blue to Peacock Play. On the other hand, in the glacial periods, currents have always been the main process of sedimentation and basin formation in the northwestern part. As in these courses, with the rise of the lake's water level and salinity reduction, the water level was raised in the Gachalan River and the possibility of transfer of the Foraminifera fos sils to the river's environment was provided. Although in all periods, the chemical decomposition of rocks has been low to moderate, but physical degradation has always dominated the formation of stones in the source region as well as the texture of the deposited sediments.