فصلنامه پژوهش های جغرافیای طبیعی
پیاپی 73 (پاییز 1389)

Introduction Extreme temperature events can impose serious impacts on environments and societies. Frost is one of the most severe weather conditions that affect human activities in many parts of Iran. The first fall and the last spring frosts usually cause damages to plants. Occurrence of the first fall frost, at the beginning of freezing period, damages crops that are still in the field. The last spring frost at the end of freezing period, which occurs at the beginning of growing season, causes damages to seedlings and young plants and to those that are already in the flowering stage. In addition to these characteristics, one of the other most important characteristics of frost is its persistence in a region.

Introduction Active faults are the ones that at the post-Quaterner and especially the Holocen epoch have had movements and it expects that in the future they also exposure to a relative movement because of their renewed activity and generate a shear on any structures locality on them. To identify these faults, seismogram and historical record information, direct and indirect paleosismology studies are utilized. The indirect paleosismology has been based on geomorphologyic studies. Its advantage is that it studies a wide scope with a high speed and the attained to interpret the changes of thousands years ago. Geomorphologyic indices used to study drainage system condition are influenced by the earth material and region climate as well as tectonic. Since Iran is the sixth country of the earthquake hazard and the earthquake belt has surrounded 90% lands of this country, location of the cities and development facilities and installations need to be considered precisely to minimize the dangers. In this regard, identifying the regions and active faults are very important. Rudbar river basin, a upstreams of Dez, located in the middle domain of zagros mountain on eastern 49? 12? 31? to 50? 17? 45? longitude and northern 32? 34? 56? to 33? 19? 40? latitude and its area is 2256 km2 in the upstream of Rudbar dam. Wide central and north eastern areas have thrust structures while in south western the folded and faulted structures are in close relationship with each other. However, special professional studies are needed in relation to the spam seismologic. It was identified in an estimation that there are more earthquakes in south western areas. Materials and Methods In this paper, Rudbar basin has been divided to seven sub-basins with average length more than 20kms and using the Relative tectonic activity (lat) index that is a combination of hypsometric integral(Hi),drainage basin shape (BS), drainage basin asymmetry(AF), ratio of valley –floor width to valley height(Vf),stream length-gradient indices(SL). Rudbar basin situation was analyzed to minimize the effects of litology and climate factors. Thus, a digital elevation model related to SRTM topographic data at the accuracy of 90 meter was provided. Then, subbasin divisions, indices measurements, geology maps digitation, and data integration were conducted by using ARCMAP,ARC INFO, and GLOBALMAPER Softwares. To increase the work accuracy and to provide necessary evidence, field studies also were formed. Results and Discussion According to Relative Tectonic Activity (lat)index, three class active(lat=1.5-1.99),1256 km2, semi-active (lat=2-2.49), 414km2 and low-active (lat=2.5-3),585 km2 were identified. Since a main part of Anooj and Gholyans subbasin has alluvium sediments and old terrace, it may be considered more active than the resulted condition. Conclusion The obtained general result shows that instability presents in this district has been the resuit of two types of fault performances: the thrust faults located in the west and east of basin such as Dehsur, Vahdat Abad and Zardkuh which had a progress and caused the elevation of district and Main Recent Fault with strike-slip that caused a crushed surface and sensitive to erosion by its right-side movement and the drop of its level surface and then caused the renewed erosion cycle. Since the desired location for constructing Rudbar dam is located in very active region and in Main Recent Fault direction and different as well as severe earthquakes have taken place on two sides of this domain, there is the possibility of tectonic instability in the domain of this dam. Hence, it is suggested that this issue needs to be considered carefully and seriously by the administrators of this project

Introduction Road accidents are among the major causes of death, injuries and financial problems of Iran. The important climatic causes of road accidents in Iran are such as slippery of road surfaces due to frost, snow, rainfall, occurrence of fog, avalanches, etc. The object of this study is to analysis the effect of weather conditions on road accidents and rating of the studied areas based on road accidents in relation to weather conditions. This study analyzed the influence of hazardous climate factors on road accidents on the road between Karaj and Chalus axis, one of important relational roads in Iran. Materials and Methods The Karaj - Chalus road axis has 70 km. long and is one of the most important roads passing through the Alborz range mountain and connecting Tehran region to the northern regions of Iran (Caspian Sea). In this study a spatial database of the road created accoding to different data collected including climate data, the locations of accident occurance points, asociated with the attribute data of each accicidents separatley on 1:250000 scale topographic basemap. In order to analysis of climatic conditions, two weather station data including Karaj and Siahbisheh weather stations have been used. The Karaj weather station is used as a representative of first part of the axis and Siahbisheh weather sation as representative of mountainous areas. The created spatial database used to evalute the sensitive points for the occurrence of road accidents in relation to various climatic factors specially sunny, cloudy, fogy conditions etc. Results and Discussion The characteristics of occurred accidents in studied area showed that about 54 percent of accident occurred in summer and spring seasons in relation to high traphic conditions. Also about 80 pecent of all accidents occurred in sunny conditions as a result of high traphic conditions. The results indicate that in all uncomfortable meterologial conditions, the frequency of accidents is equal, but in the cloudy weather is higher than other conditions. Aanalysis of road accidents showed that several accidents happened under the following climatic conditions and locations. In sunny days, at kilometers 17, 20, 41, during cloudy days at 62, in rainy days at 40, 70, during snowy days, 40, 60, 62 and during foggy days at 60, 62, 65 km. from Karaj city occurred respectivly. These roads’ positions can be considered as dangerous hot points that need spectial attention to decrease the number of accidents. Spatial distribution of accidents showed that there are positive relations between altitude and the number of acccidets. Correlation coefficent between these two parameters is 0.6390 that is significant in ststistical cosideration. In other words, in mountainous areas of studdied area, with increasing the alititude, the rate of accident increaesd, the importartat factor for this condition is changing of climatic conditiions in mountaionus regions of Karaj-Chalous road. Therefore it can be said that the weather change caused from changes in toppography, have essential role in creating the accidents. Finally the zoning map provided using GIS ability indicates that the range of 10 to 30, 30 to 40 and 50 to 60 show the least accident, in bad weather conditions, while the remains of sections face with medium accident hazards because of weather and topographic conditions. The prepared map can be used to manage the road accidents consideration and it is clear that the areas with high hazards potential can be considered to accurate study. Conclusion In order to comparing the relations between climate and accidents, the entire studied axis classified into two categories: first from 1 to 35 km. from Karaj based on Karaj weather station and the second from 35 to 70 km. based on Siah Bisheh weathers station. The comparing results showed in the second section of axis (from 35 to 70) the rate of accident increased according to Climatic changes. Comparing the weather in two classified sections showed all unconformable weather conditions in second section are very intensive. The studied axis showed that the mentioned axis is one of the hazardous roads in Iran that faces with high number of accidents that climate factors have intensive effects on it. Hence to decrease the accident caused with uncomfortable climate conditions presents some solves such as establishing warning systems and, considering road climatic sensors are among necessary factors

Introduction A natural disaster is the effect of a natural hazard (e.g. flood, earthquake, or landslide) that affects the environment, and leads to financial, environmental and/or human losses. The resulting loss depends on the capacity of population to support or resist the disaster, and their resilience. This understanding is concentrated in the formulation: "disasters occur when hazards meet vulnerability". A natural hazard will hence never result in a natural disaster in areas without vulnerability, e.g. strong earthquakes in uninhabited areas. Evidence indicates are continuously increased all types of natural crises, from frequency and severity. Natural factors always impose dangers throughout history and around the world to natural environments and built ones. Materials and Methods West of Fars region located in the Zagros Mountain Ranges zone, including areas that due to natural and geographical features such special geological structure and earthquake belt placement on active faults and major mountain features with variable climatic conditions and the existence of numerous torrential rivers and etc, there have Potential occurrence of natural hazards, especially earthquakes, floods, mass movements and erosion. West region of Fars province is situated in the Southwest of the Iranian mountain ranges known as Zagros. The area covers 10703 km2, spanning latitude 29 to 30° 41'N., and longitude 50o34' to 52° 8’E. In this study it was attempt to use data obtained from modeling criteria and effective environmental layers using Analytic Hierarchy Process (AHP) and fuzzy classification method with high spatial analysis and modeling capabilities of Geographic Information Systems (GIS), severity of environmental vulnerability of area was considered and were zoning. So the main data and materials are including data layers related to features of effective natural environment in vulnerability of humanity environments such Topography and hydrology of surface water (1:25000), Geology (1:100000), Pedology and vegetation (1:250000) and landuse (1:25000) maps, and Meteorology data and variables like precipitation, as well as satellite images of Ikonos and Quick birds were used in perform corrections on the various maps. Methodology of research is based on expert choice of criteria and their priorities (Delphi questionnaire), normalizing methods (Fuzzy logic classification) and Multivariate models combining layers (AHP). So first Delphi questionnaire was prepared and then were completed by eight experts in specialized fields related to regional planning. Then using software expert choice were calculated coefficients of criteria and subcriteria according to Delphi questionarie. Also, all the subcriteria coefficients with Fuzzy method were classified and they took fuzzy membership. At last coefficients obtained in the previous step were transferred to attribute of GIS information layers. In GIS all layers were Geo Refrenced by UTM WGS84 coordinate system. and after entering AHP coefficients to attribute of information layers, all maps were converted to Raster format. So all related layers with EarthQuick, WaterFlood,Mass Movements and Erosion once separately overlaied and thus their integration was calculated environmental vulnerability map of the area. Results and Discussion According to results of calculations performed in the research process and Features of the area's natural and human environment, Earthquake, Flood and Mass movement, respectively are the highest risks and threats. Also, based on modeling results and risk zoning in West of Fars region are recognized more than 34% of study area with a range of relative to very high vulnerability features that mainly includes mountainous regions and their foothills in NE, East, Dra’ mountain and the central strip. So in these areas, accumulation and overlaies of risk factors provides hazardous conditions. Also according to the risk zoning map, flat plains, have a low level of vulnerability. In areas with high risk and vulnerability, attention to concentration of residence with severe agglomeration of population and activity in middle axis, as well as having great ecological values of forests and their especial ecosystems, make increasing the value of considering to these studies. Conclustion Considering that so far, hasn’t been done comprehensive and accurate studies about the sensitivity and vulnerability of study area, there is no detailed information about flood status, Landslide or landslip and or about the destruction and potential vulnerability of region to earthquake. It is necessary to studyed vulnerability and various human and natural risks and or their combinations using detailed and accurate data and information layers.

Introduction Climate change is expected to affect agriculture very differently in various parts of the world. The resulting effects depend on current climatic and soil conditions, the direction of change and the availability of resources and infrastructure to cope with change. Biological systems are based primarily upon photosynthesis and are thus dependent on incoming radiation. However, the potential for production set by the radiation is greatly modified by temperature and rainfall. The main effect of temperature is to control the duration of the period when growth is possible in each year. Using statistical downscaling models in climate change studies provides possibility to generate the weather data on time and place appropriate scales. Increasing of Publication and human activities increase green house gases and carbon dioxide. This situation leads to the temperature increased to 0.6 Centigrade. Scientists believe that the extreme phenomenon is the main climatic index. This possibility is an important help in the climate change studying in local and regional scale. Intensity of extreme phenomenon must know as climate changes main branch. Materials and methods Extreme meteorological events, such as spells of high temperature, heavy storms, or droughts, can severely disrupt crop production. Recent studies have considered possible changes in the variability, as well as in the mean values of climatic variables. Where certain varieties of crops are grown near their limits of maximum temperature tolerance, heat spells can be particularly. In this research, growth season and freezing season length have been investigated as climate changes indices. Using statistical data for each station, the daily data bank including minimum and maximum temperature were marked in the Access software. Then these data in the various years using growth season length and freezing period length were extracted in the past and future period in the LARS-WG software. In the next step, Spirman’s correlation coefficient has been used for testing the hypothesis of the research. In definition, the first six daily period after latest freezing is as the starting of season period that means temperature is above of and the final six daily period is as the end of season period that the average temperature is below of. The interval between the first freezing in autumn and the final freezing in the spring is as freezing period. The changes assessment of indices have been done during two climate periods including the past (1976-2005) and the future (2010-2039) in three synoptically stations: Mashad, Torbat Heydarieh and Sabzevar in Khorasan Razavi province, in Iran. Results and Discussion Results showed that growth season length increases in Mashad and Sabzevar stations Results also showed that growth season length decreases in Torbat Heydarieh station. These changes in freezing season length indices are greater than the others. In three stations. We will observe that freezing season length decreases between 15-16 days as a result of global warming. Results of hypothesis test showed that there is no correlation between observed growth season length and estimated growth season length and also observed freezing season length and estimated freezing season length using Spearman’s correlation coefficient. Conclusion In this paper, with regarding to phenomenon including growth season length and freezing period length, the climatic fluctuations were estimated. The comparative of the past and future periods shows that growth season period will be increased and freezing period length will be decreased in the area under study. According to table 2, grow season length would have been increased in Mashad and Sabzevar stations. Also freezing period length would have been decresed in Torbat-e Heydarieh station. In the other words, premature freezing and late freezing would have been decreased in the area under study. The obtain results of this research emphasis the results of the other researches such as Sedaghat Kerdar and Rahimzadeh (2006), Hino et al (1999) and Bonsal (2000).

Introduction The base of analysis of applicative geomorphology is according to systemic stand point. Systemic geomorphology is based on recognition of geomorphic forms and processes and relationships between them. Efficiency of this stand point, when there are linear and non linear reciprocal relationships between parts and elements of system, is very important. The studied feature in this research is Barchan dunes in the south of playa Chah Jam. In studied field, hundreds of barchans can be found; generally all of them have same size and shape. These landscapes are mobile dunes which constitute a considerable threat to infrastructure in study field with their mobile sands. They move over communication ways of region, phone lines and even in to Damghan city, and also disturb agricultural fields and intensify desertification problems in study area. Barchan dunes are open and natural systems and are capable of being modelled in different levels. These dunes are observed where sand availability is low and prevailing wind direction is quite constant. In this paper we have tried to describe morphologic characterizes of the Barchan dune using mathematical and statistical modelling process via morphometric parameters and parabola characterizes. The obtained results from this study can be helpful in the systemic management of desert regions and also can be benefit in the plans of stabiles of trombone sands and recognition of critical regions from view point of windy erosion. Materials and Methods The studied area (Chah Jam erg) is located in the south of playa Haj Aligholi, in central part of Semnan province, Iran. Studied field is bounded between latitudes 350, 45َ to 35َ0, 50َ N and between longitudes 540, 40َ to 550, 10َ E. For measurement of morphological parameters, at first, we have been defended a model, and Barchan morphometric characterize are measured along 10 transects in nature that these transects were covering entire extent of Chah Jam erg. Mathematical modelling of the Barchan shape is performed via its simulation in the coordinate system and using non linear equations of the parabola that it has been gotten two equations for windward side parabola and slip face parabola. Then for recognition of type and intensity of relationships between them, we have studied and reexamined these relationships, using SPSS software and regression analysis techniques. For this achievement, at start, we have reexamined linear and nonlinear, simple and multiple variable regressive analysis technique such as linear, power, exponential, cubic, logarithmic, multiplier and etc, and then we have been selected the most important and the most suitable of relationships. Totally, in this study, the most important and the most suitable of relationships are following from power relationships. Results and Discussion Using Statistical modelling, relationships between mathematical and morphological parameters of Barchan dunes has been determined, that these relationships show a significant power relation with maximum of determination index and minimum of estimation error. One of the most important results of this study is the statistical and mathematical modelling of Barchan dunes and converting of mathematical method to statistical method and vice versa. One of the main characteristics of morphology of Barchan dune is its parabolic shape, that this characteristic is influenced by morphology of crescent and aircraft of Barchan. Therefore for mathematical modelling of Barchan shape can be used parabola equations. On the other words, two-dimensional modelling of Barchan surfaces (regardless from its spatial characteristics) is possible through parabola equations. The recognition of morphologic characteristics of Barchan can act as an index in order to determine the condition of Barchan system and also shed light on its trends. Furthermore, the investigation and exact estimation of these parameters is a consequence from rate of threat, destruction and annual movement that their assessment determines different region from the view point of environmental management and prioritize them. Therefore, obtained results from these methods can be very important for investigation of shape and recognition of behavior of Barchan dunes in nature. Conclusion In this paper we have used statistical and mathematical modeling methods and have represented models that using them, can easily account morphological parameters of Barchan dunes. Therefore the results of this study provide possible of exact and rapid estimation of Barchan morphometric and morphologic parameters. The combination of two methods of statistical and mathematical modelling is a fundamental infrastructure for simulation of Barchan dunes geomorphologic characteristics in the laboratory and imaginary circumferences. Focal distance is one of the important parameters of the parabolas of Barchan dunes that shows its different situations with each other. Results show that if the focal distance of the Barchan dune decreases, its spout becomes closer and the divergent state of Barchan horns decreases, too. Barchan dunes that have farther focal distance are wider and have extensive dimensions and more volume.

Introduction Most of Iran areas have been located in arid and semi arid climates. Water resource scarcity is one of the problems that has been attended by experts, decision makers and managers of the country. With respect to occurring droughts in recent years, proper management of existing water resources and also achieving to the better solution for their usage are essential. One of the ways that a large volume of water can be losses through the land surface is evapotranspiration (ET) as it has an important role in water resource management. ET of each region is generally affected by different climatic parameters as well as its geographical attributes. To have a proper management of the ET, as a great water losing way, it seems to be necessary to know and study the ET and its effective parameters in each region. Sensitivity analysis is always known as one of these approaches. This approach seeks to attribute uncertain output to specific input parameters. The input parameters are varied in turn and their effects on the model output are quantified. Materials and Methods In this study, a sensitivity analysis procedure was accomplished on data of three meteorological stations in Yazd province, central part of Iran. Yazd, Tabas and Marvast have been these studied stations. Appropriate spatial distribution, as well as having extreme values for one (or more) climatic parameter(s) were the major reasons for selection of these stations. Yazd province also was selected due to the importance of its evapotranspiration as a major way for wasting the surface and subsurface water resources. This sensitivity analysis was focused on maximum temperature (Tmax), minimum temperature (Tmin), relative humidity (RH) and wind speed (W), as four input parameters that influence ET, dominantly. For this purpose, successive increase and decrease of these parameters were accomplished in three 10% change intervals. Therefore, ±10%, ±20% and ±30% of the input parameters were calculated and inserted in the ET model to yield different evapotranspiration outputs. Employed ET model was CROPWAT, as a most frequently used approach for determination of reference ET. This model calculates reference evapotranspiration based on the FAO-Penman-Monteith equation. Via the procedure, six different ET values were obtained for successive changes of each input parameter. This sensitivity analysis was separately accomplished for four representative months in all the selected meteorological stations. May, August, November and February were representative months of spring, summer, autumn and winter seasons, respectively. Finally, relative importance and adequacy of different ET input parameters were investigated at different seasons and different stations, independently. Results and Discussion The results of this study indicate that maximum reference evapotranspiration belongs to August with 10, 8.5 and 7.5 mm per day for Yazd, Tabas and Marvast stations, respectively. After successive changes of input parameters and consequently, yield of different ET values, relative importance of each input parameter was distinguished. As a preliminary result, order of importance in each season was similar for almost all the independent stations. For example, Tmax, W and Tmin were main three parameters that influence reference ET of spring season, decreasingly. This order was also changed to W, Tmax and Tmin in summer and RH, Tmax and W in winter. Order of importance in autumn was slightly different for Yazd and Marvast stations compared with Tabas. This order was W, Tmax and RH for Yazd and Marvast, while it was W, Tmax and Tmin in Tabas station. Results of the study can also be considered as a different view; main important input parameter that influenced ET was different for each season compared with other ones. For example, main important parameter in spring was Tmax, while in summer was wind speed. Similarly, wind speed and relative humidity were distinguished as the most important parameters in autumn and winter seasons, respectively. Considering importance of relative humidity as the main parameter in winter season, it seems that precipitation has significantly influenced the reference ET, adversely. Sensitivity analysis on annual changes of reference ET also showed that Tmax and wind speed were the main input parameters for calculation of ET. For instance, after increasing the Tmax and W until 30% (as input parameters), reference ET was also increased until 1.3, 0.6 and 0.5 mm per day in Yazd, Marvast and Tabas stations, respectively. Relative humidity also was found as a negligible input parameter in this annual basis sensitivity analysis. Conclusion Considering the results for sensitivity analysis of the FAO-Penman-Monteith equation inputs, relative importance of different climatic parameters seems to be more significant compared with other input parameters such as geographical attributes of the studied region.

Introduction Generally there are two ways for frost protection: active methods and passive ones. Passive methods should be carried out much earlier than the frost occurrence, for these methods are not the direct ways of frost protection but are the ways of avoiding and escaping from the frost. Active methods are the ways of frost protection that are carried out right before the frost or at the time of its occurrence. These methods include garden heaters, spray irrigation, wind machines, etc. In the present study, 3 ways of frost protection namely fogger, heater and fogger-heater were compared with the control treatment. Fogger can play a protective role by creating artificial fog, against the emission of the garden heat especially at the nights when there is inversion. These machines have a powerful pressure pump that directs the water into the pipes and with a lot of pressure pumps it out of the pipes and in this way makes small drops of water (fog). These particle's absorb the infra-red (rays) that are emitted from the garden and reflex them back to the ground and maintain much garden's heat in comparison with the condition in which there is no cloud. Materials and Methods The present study was carried out randomly in a garden of 20 hectares in a farm located in the north- west of Isfahan (Alavijeh region) in the fall and spring of 2007. In order to investigate the function of the fogger machine, 4 plots were considered. One of these plots which was considered as a control plot was allocated 1000 meters away from the other three plots and it dimension were 50×50cm. Three other plots of the same size were considered as the treatments of the forger, heater and heater- fogger. A 50-meter distance was considered between the treatments (plots). All plots had same conditions regarding the numbers, the soil characteristics and geographically they had the same angle of slope. In each of these plots a wooden cottage of standard Stevenson, which is currently in use in the national weather forecasting stations, was installed. In each of these cottages, there was weather forecasting equipments including minimum and maximum thermometer and a thermograph. After installing this equipment in each plot, the person who was in charge of reading the climatic parameters was trained. Reading the parameters was regularly done every six hours, for the parameters of minimum and maximum temperature as well as the dry temperature data from for casting stations were daily recorded in special tables. Watching the parameters was continued during March, April and May of 2007. It is worth mentioning that the data taken from thermometer were used along with the aforementioned data. The person who was in charge of watching the data used to change the graph paper of the thermometer every Monday. Results and Discussion The results obtained from ANOVA showed that there is a significant difference of 5 percent among the averages of treatments (frost protection method). And this depicts that there is a difference at least between two treatments. Based on this, and in order to find out that between which treatments there is a difference Duncan's multiple test was used to compare each treatment with the control treatment. Since the fogger maintains the heat and prevents its emission particularly in inversion coldness, it cannot alone play an important role in the prevention of frost. For this reason, the heater was used in a separate block along with the fogger machine. In the way the treatment could produce heat and have an extra role in addition to the protective role that the fogger played. The results showed that the increase of temperature by applying these two methods could show a significant difference of 5% level in their comparison with the control treatment. The increase of temperature in the best condition reached 1.8 (°C) and the average increase was 0.9 (°C). Conclusion Spring coldness often causes a loss in the new blooms and fruits on the trees of Isfahan. Often these coldnesses are radative types and their continuation can result in the loss of all the crops. Although predicting the inversion is not easy to do, but probably, farmers prepare to protect their crops against the sudden fall of the temperature and frost by being informed before the frost starts. The result of this study shows that the application of foggers accompanied by heaters can have effective results in frost protection. For the heater generates the heat and the fogger keeps the heat in the garden. In the studied farm, case temperature increased 1.8 (°C) in the best condition.