Journal of Geography and Planning
Year:2009 | Volume:14 | Issue:28|Papers Count:10

The solar radiation that reaches to the earth's surface varies in the yearly duration and depends on the weather conditions. To predict the global solar radiation at the earth's surface' the clearness index should be calculated. In this study, the daily clearness index has been calculated using the daily average measured global solar radiation data, which has been reported by IRIMO. The daily average clearness index results have been compared with two available methods (Collares, Duffie). The results show that if global solar radiation is estimated by Collares method, the calculated clearness index will be more close to the measured data.

Rock flows are frequent natural and geomorphic hazards in semi-arid mountainous regions. Among many mass movement hazards occurring in mountainous areas, rock flows are very frequent phenomena which are-characrerized by their suddenness and difficulty to predict. These phenomena can be attributed both to the development of man-made structures and human impacts in mountainous regions, and have been threats to people who live, work and settele in villages or pass in through mountainous regions and routes. Garangoo catchment, as a semi-arid area (located in eastern slope of Sahand mountain, situated from 46o.27'to 47o.42 E, from 36.58' to 37o.44'N), is one of largest catchments of Sahand mountain. Rock flow occurrence is extended to the foothills where generally populated areas are located. The management of it firstly requires, the investigation of mechanism of processes induced in rock flows and then zoning of susceptible areas to the hazard events. The aim of this article is to give an overview of 9 factors in the occurrence of rock flow hazards, susceptibility and assessment elements in risk mapping and finally rock flow vulnerability and risk assessment by the use of geographical information systems. For estimation of spatial and temporal distribution of potential rock flows, we used many data and maps, for example, precipitation data, geological data and digital terrain data in GIS. The empirical approach relies on bivariate statistical correlation between locations of rock flows and factors. The final map, which is produced by ArcView, shows that major parts of the Garangoo catchment consist of volcanic ash, marl and old alluvium, with steep slope at site of 2000 m altitude. The volcanic material (andesite and dasite) especially Miocene volcanic stone, is frequently producing debris and rock segments. These materials are deposited on road surfaces and disturb passengers.

The first step in environmental planning is determining of planning limits and recognition of their elements. In fact the basic distribution and allocation of land uses with standards depend on urban physical planning division. Unsuitable physical limiting of urban areas by any organization has adverse impacts on citizen's time and expense. For these reasons most urban problems in our country are related to physical division. Urban neighborhood planning and familiarity with its criteria and its adaptation in our cities is the best alternative for providing desirable urban life.This article discusses about neighborhood planning and its goals and effective factors in urban planning by using of (local and) foreign experiences in neighborhood planning and adapting their criteria with some suggestion about Iranian cities, especially Tabriz metropolitan. Methodology of this research is documentary with descriptive and analytical methods.

The present study attempts to specify status of Mahabad in urban network of West Azerbaijan Province and urban hierarchy in 1385 has been studied. Regarding the political, economic and cultural aspects, Urmia the center of the Province attracts more immigrants and this fact has made urban hierarchy not to follow the rank-size role. In 1385, the population of Urmia (the most populated city) was 3.47 times more than Bookan and 4.38 times more than Mahabad (the fourth populated city). Studying the economic situation of Mahabad region has been attempted. The sphere of influence of Mahabad at undulation in 1335 had 4 ranks. The urban hierarchy in urban network of West-Azerbaijan has been half balanced. Providing equal opportunities for every city of the Province and also proposing better services could help the optimal spatial hierarchy in this Province.

In this research we have applied the data records of 8 climatic variables (including wet and dry temperature, relative humidity, tropical and Meridian winds) for hours 6:30, 12:30, and 18:30 (local time) along with variables such as precipitation, maximum and minimum temperatures, in Tabriz synoptic station. The aim of this study was to determine various types of synoptic climates and weathers in the area for 23 years from 1981 to 2003. During the research it became clear that there were 8339 complete days showing the whole data range. The matrix (8339*8) then became standardized and the cluster analysis carried out on this matrix. The results showed 7 different types of synoptic climates in Tabriz during the study period.

The frequent occurrence of drought and high evaporation of water resources on one hand the execution of dam projects on the rivers flowing into the lake and exploiting the surface water on the other hand has caused great reduction in the amount of water volume and the area covered by it during recent decades, resulting significant changes in the coastal lines. This has resulted in extra salinity of the water to leave undesired impact on vulnerable ecological system.Regarding the impact of such process, the main aim of this article is to provide a graphical description of different water elevation data through derived indicators of time series.To reach a goal the daily records of water elevation from 1970 to 2004 existing at Golmankhaneh station were used and analysed.To create time series in seasonal and annual scale, Excel software and Mini Tab have been used. For preliminary analysis of time series, firstly the primary indexes like observation smoothed data, moving average and percentage of fluctuation have been illustrated through graphic models. Secondly other factors like observed seasonal and irregular cycle have been calculated and simulated, and thirdly normalized remain mass curve techniques are used to detect the fluctuations in lake water elevation.Final findings indicate magnificent fluctuations in Urmia lake water elevation.

Drought is one of the most important natural disasters that affects sectors with its high frequency particularly in dry and semiarid areas of Iran. Lack of raining will have various effects on agriculture, surface water and underground water resources, humidity of soil and rivers. Regarding the location of Fars Province on dry and semiarid climate areas and the incidence of repeated drought, especially in recent years, necessitates paying attention to drought simulation and forecasting. Quantitative and description of environmental process and the anticipation and estimation of its behavior at the time and situations without observation and sample requires having a pattern and model of that process. One of the methods to access the goal of modelalization in drought incidence is the use of time series model. In the present study, the precipitation data of 90 pluviometry and synoptic stations in Fars province were used with regard for 30 years. To determine the grade of drought severity, the standard precipitation index was also used due to its advantages in local analysis and establishing time relationship between drought incidences. Determination of desirable local model according to drought condition of Fars Province was conducted after drought severity monitoring and evaluation. The suitable model for each area was provided using time series analysis and based on provided local pattern in different areas of Fars Province. The ARIMA method was selected in drought incidence simulation using time series models on the basis of autocorrelation and partial-autocorrelation. All probable models were tested due to stability and parameters and different method evaluation and the most suitable model was determined and presented for drought simulation in each area.

The present paper aims at Studying the changing trends of temperature (mean, maximum, minimum, maximum and minimum absolute, freezing days including) in order to find an easy and effective way to measure the similarity between temperature time series on various stations.The cluster analysis was carried out in all stations of Tehran city, which led to classification: the following.1- Mehrabad Station and Doushan Tappeh.2- Chitgar Station.3- Ahminabad Station.4- Geophysics and Shomal Tehran Station.We recognised changing tempo-spatial patterns of temperature. Tehran city, on a decadal scale, encountered with increasing temperature trends.