GEOGRAPHICAL RESEARCH
Year:2012 | Volume:27 | Issue:2 (105)|Papers Count:11

Heavy rains are one of the features of arid and semi arid climates which result in flood. This kind of rainfall originates from environmental and synoptic conditions. Mediterranean cyclones are the major factor in heavy rainfall in Iran, but these cyclones do not happen in some parts of Iran such as Southern and Southeastern areas. In this study, it has been tried to pinpoint the synoptic reasons of heavy rainfall in Isfahan through the analysis of the relationship between this rainfall in Isfahan and atmospheric system over Iran and the areas around it. The findings of this study show that the major factor is the arrival of Sudanese low pressure system in this region from the southwest, of course if the ascent local conditions such as heat occur, the heaviest rains happen in Isfahan. In fact, this kind of rainfall in Isfahan has a Sudanese origin and if it is accompanied by Mediterranean system, heavier rain falls.

Climate is a multivariate system. Every change in every climate variable could result in different changes in climate. Recently, experts have paid extensive attention to frequency distribution sequence of climate elements. Accordingly, many different indices have been defined. Precipitation extremes can exhibit the phase space of climate system. A technique that can be used to analyze climate phase space is multivariate statistics. In order to analyze precipitation extremes simultaneity, 26 indices of daily precipitation of Zanjan city during 1961-2006 had been chosen. Principle Components Analysis has been used to find the most important components in extreme precipitation. Accordingly, 6 components could justify about 86.4% of variation in precipitation extremes indices. Spectral analyses on principle components have shown a 3- year cycle in second components as well as a 4-year cycle in forth component and 2-3 years cycles in the fifth. The second component that shows frequency and spells 95 percentile of precipitation has a significant decreasing trend. Also, there is a dropped jump in first component as the first percentile.

One of the important problems in the urban development process in the world has been land use and planning for urban sustainability. Considering this important issue, this study investigates spatial analysis and urban land use planning in Dogonbadan. This research is applied- analytical and by applying land extension index and Hensen model intends to study and plan urban land use in this city. Urban land extension index was calculated to be 53.12 percentages that shows the extensive physical development of Dogonbadan city. The result of using Hensen model show that maximum development potential belongs to the zone 7 and 5. In the end of 2011 that population of Dogonbadan reaches to 07640(38550 increase in population), we require1315.92 hectare (805.42 in current state and 510.50 hectare in the end of planning year) physical spaces for building various types of uses.

In order to have spatial and temporal analysis of Iran extreme cold days'' trend, the average of daily temperature data from 663 synoptic and climatologic stations of Iran during the period of 1961/21/03 to 2004/19/03 were used. Then, temperature data on 15*15 kilometer pixels were interpolated using Kriging method for Iran. The extreme cold days were identified by Normalized Temperature Difference (NTD) index. According to the index, the days with NTD£-2 were selected as extreme cold days. Then, a trend analysis was applied to the extreme cold days for each month of year. The results showed the negative trend extend of the extreme cold days is further than the positive trend extend. Positive trend located on the high mountains in Shahre Kord, Sannadaj, Zanjan to Ardabil and a thin band on Alborz mountains range. While a negative trend located on central-south of Iran. In January and July extreme cold occurrence is more frequent and least respectively.

There are continuous connections between a city and its periphery and the form of these relations varies. Collection of these relations makes an influential area forming the various relations between the city and periphery. These relations are not the same and do not have unique concentration and density; rather, they hey depend on population, geographic conditions and the role of the city in the special structure of the region. It is assumed that in Eastern Azerbaijan urban network, the civic dwellings are influenced by these different penetrative conditions. This study is descriptive- analytical and the data were collected through library studies, referring to statistic and maps. Therefore, this study attempts to consider the penetration area of Eastern Azerbaijan cities relying on quantitative, statistic (gravity rule) and geographic (analyzing procedures) methods. The results of this study in supra- regional level among the province's central towns contiguous to Tabriz indicates that the penetration areas of Tabriz except Euromieh have advanced toward other central towns (Ardabil, zanjan, sanandaj) and inhibits their development and giving service to their own penetration areas. Marand and Bonab, in intraregional level among the five cities with more than 50 thousand population, have developed their penetration area and the penetration area of Marageh, Mianeh and Ahar has been of benefit to Tabriz and penetration area of 51 cities with less than 50 thousand population is of benefit to Tabriz and to their disadvantage. Also, considering towns with the some potential line, Tabriz, Marageh, Bonab, Marand, Mianeh, Ahar and sarab have the highest penetration and attraction coefficient. The same results are achieved with process analysis method that the penetration area of Tabriz influences the whole region and the district towns of the province (maragch, Marand, Mianeh, Ahar and Bonab) have developed their own penetration area. In general, we can conclude that the results of the theoretical and experimental penetration area are the same.

The weaknesses of the traditional climatic classification methods in presenting the climatic realities of Caspian region and showing the new methods'' merits based on multivariate statistical methods, and geographical information system in presenting the climatic regions of Caspian, are among the most important ideas of conducting this study. To do so, we used the data of synoptic stations of north and north east of the country in a period of 20 years. To analyze 19 climatic elements in “Factor analysis” method; at first the map of each studied climate of the region was traced by “Surfer software” on the bases of Pixel in a 15*15 km measure. And also by “minimum curvature” method, data of each map become interpolated. After that, data of each map were changed to digital data, which a matrix in a 266*19 measure was formed of those digital data. By analyzing the matrix in “Factor analysis” method, it was certificated that 98% data variance of it is of the precipitation and temperature that Data consist: 50% of the primary factor and 48% of the secondary factor. Quantities of precipitation and temperature were analyzed by “agglomerative hierarchical cluster analyzes” in “ward” method that the Caspian region was divided to four regions in the aftermath; moderate and humid, moderate and semi humid, cold and low precipitation, and semi cold and low precipitation. These minor climatic regions are greatly influenced by some climatic factors, as the remoteness and farness from the sea and the elevation increase. Climatic varieties in the eastern parts, especially in the limits of Golestan province, are more evident.

In this study, first we estimated the poverty line of household and poverty indices in rural areas between1999 to 2004. Stochastic dominance test is applied to compare the extent of poverty in the beginning year and the end year of third- socio economic development plan of Iran. The most important feature of this technique is providing comparative comparison of poverty in two years or different period. The results show that during these years the rural poverty line based on reciprocal of engel’s coefficient method has been greater than other relative poverty lines. Poverty lines were increasing in rural areas based on all of measuring poverty methods. Poverty gap and poverty intensity has been alleviated in rural areas. Besides, by using the stochastic dominance test, variation of poverty was tested and the results show the decreasing of poverty in rural areas of Isfahan province during the studied period. This may indicate that the poverty alleviation policies in the third plan have been promising.

Heavy rains are one of the features of arid and semi arid climates which result in flood. This kind of rainfall originates from environmental and synoptic conditions. Mediterranean cyclones are the major factor in heavy rainfall in Iran, but these cyclones do not happen in some parts of Iran such as Southern and Southeastern areas. In this study, it has been tried to pinpoint the synoptic reasons of heavy rainfall in Isfahan through the analysis of the relationship between this rainfall in Isfahan and atmospheric system over Iran and the areas around it. The findings of this study show that the major factor is the arrival of Sudanese low pressure system in this region from the southwest, of course if the ascent local conditions such as heat occur, the heaviest rains happen in Isfahan. In fact, this kind of rainfall in Isfahan has a Sudanese origin and if it is accompanied by Mediterranean system, heavier rain falls.

The environmental problems, in different dimensions, are resulted from the lack of environmental considerations and criteria in locating new cities. The main purpose of this article is to compare different criteria based on library studies and expert opinions and determining suitable criteria in order to evaluate the environmental potential to establish new cities to achieve urban permanent development having the least maleffects at present and in the long term. In this study, multi-criteria assessment approach and Analytical Hierarchical process(AHP) were used in ecological potential assessment of Khuzestan Zard basin for urban development in geological information system (GIS).AHP model and its way of use which are introduced in this article, is one of the most known techniques of multi-purpose decision making for situations which have multiple and opposite scales and the applicability of this method has been proved in environmental planning like Land Capability Assessment. In the AHP method, 13 criteria were used where the proposed criteria were compared in pair, with their weigh being then determined. Final results show that northern part of Zard basin and in the terms of political partitions Ghale Tol village of central part of Baghmalek town is of the most rank in urban development. Results obtained from this study can be used as a pattern to be utilized for urban planner and designers in order to well suite urban location with respect to observing the environmental considerations.

In the current research, wind energy potential at Yazd synoptic stations, which contain wind data with 10 years statistic period and beyond, including Yazd synoptic station (1976-2006), Tabass (1987-2006), Robate Poshte Badam (1992-2006), Bafgh (1993-2006) and Marvast (1997-2006), has been studied. Wind data were obtained from the recorded data at Yazd meteorology organization. The data were recorded at an interval of 3 hrs at 10 m height above the ground level. Using weibull distribution function, discontinuous wind data were substituted. This substitution has been applied through least square feet after computing weibull parameters C & K. Wind date were changed at 10 m height to 50 m by applying one seventh power law (5o m is the most height of turbines axis) and characteristics of both wind speed and wind power in each height has been computed. Due to wind power density equals 222.224 and 444.938 w/m2 at 10 and 50 m height respectively, average wind speed equals 7.78 m/s at 50 m height, wind existence equals 44571.1 h/y, probability of wind blowing in the wind existence hours with speeds between 3 to 25 m/s equals 0.94, most probability of wind speed equals 7.25 m/s and standard deviation of speeds equals 1.95 m/s, the result show that Marvast synoptic station is an ideal place having high wind energy potential. Application of wind energy at Yazd synoptic station with turbines working at the speed of 2.32 m/s at 50 m height axis and above has been economically efficient. Wind energy at Tabass synoptic station is useful in agriculture. In addition to the result obtained a new equation emerged that might be useful in the calculation of the duration of wind existence in an area.

Tehran as the biggest metropolitan of Iran is located in the areas that are at high-risk of earthquake. What increases Tehran's vulnerability toward earthquake is the urban physical expansion in vaious dimensions. Since the analysis of the mentioned expansion is a solution to many urban problems, the effects of Tehran expansion in increasing vulnerability to earthquake has been surveyed in last 200 years. The purposes of this study include: 1) to represent Tehran physical expansion in the last 200 years. 2) To explain the relationship between population increase and Tehran expansion. 3) To analyzed Tehran spatial expansion with regard to earthquake vulnerability. In this study we review the physical expansion of Tehran from the time that it has been a small village to the time that it changed to a metropolitan. The population and surface area data of Tehran are collected in the duration of 1786- 2009 using Holdren model, in order to explain the relationship between urban population growth and its expansion. With regard to the historical earthquake records, earthquake seismicity background and various faults, findings show that Tehran is at high risk of earthquake vulnerability. In the period of study, 91 percent of Tehran expansion was due to population growth and 9 percent of Tehran expansion has been related to sprawl and horizontal growth. Uncoordinated and unprincipled expansion of Tehran, especially in recent decades, construction near active faults show that if a severe earthquake in Tehran happen, it makes loss and damage to this city.