Physical Geography Research
Year:2020 | Volume:52 | Issue:2|Papers Count:10

Introduction: Weather conditions have always affected the man’ s life; so he is used to adopt his life with Weather conditions, one of which is the condition of Cold waves. Cold days and cold waves are examples of extreme-temperature that include unusual notable amount of minimum temperature. Reduction of minimum temperature depends on heating degree and wind speed. Cold waves can be considered as a natural disaster or a provider of ideal weather in summer. Thus, present paper tries to analyze cold wave that mitigates weather in the warm period of year, besides cold waves of cold period in ten years. Materials and methods: To pattern the cold waves of Iran in a ten-year period of time (2004-2013) three-hour minimum data of European Centre for Medium-Range Weather Forecasts (ECMWF) with distance of 1 * 1 degree latitude and Longitude has been used. In present study, a cold day due to relative notion of Coldness in different time and places, is defined as a day in which standard score of minimum temperature is below-1. For this reason, minimum data of all days was separated by MATLAB software; then by using the standard score those day with Anomalies below-1 known as cold days were diagnosed. In the next step all the days (569 days) that had this characteristic by MATLAB and based on sea level pressure patterns correlation were divided into five different classes includes Spring, Summer, Autumn, late Autumn, early winter and winter And interpreted them synoptic patterns. In the next step wind speed and also minimum and maximum temperature difference thresholds was used to distinction between the Radiative cool waves from the advective cool waves, so that minimum and maximum temperature difference below 8 ° C and wind speed more than Breeze threshold was used as advective cool waves criteria. Results and Discussion: By extracting 569 days of negative anomalies between 2004 and 2013 it became clear that 2013 with 124 days and 2006 with 20 days (with negative anomalies below-1) have the most and the least negative anomalies respectively, in the mentioned research period. August, which have 83 days of negative anomalies, also contained the highest anomaly in selected 10 years. Analyzing level pressure patterns correlation between five presented patterns showed that interclass correlation of late autumn and early winter was 0. 94 and more than all other groups. The highest correlation between groups was also between fourth (late autumn and early winter pattern) and fifth classes (winter pattern). In the days which cold waves entered the country, wind speed never reached to high-speed level and never exceed of the average wind speed. This speed never reached the average wind speed in summer but the frequency of light wind was higher than other seasons. While the frequency of breeze flow in the second and cold half of year is more than the first or warm half of the year; low speed of waves produce more intensive and continues cold wave when it’ s accompanied by cold weather. Cold waves of Iran are usually advection and enter country from north and through west flows. In spring pattern (first pattern) west systems cause reduction of temperature and mitigation of Iran weather especially in western and northern regions of country. Minimum and maximum temperature difference in northwest of Iran was lower than 5 ° C in this pattern, while it was observed in water areas only in the other patterns. The highest difference between daily minimum and maximum temperature has been recorded in the second class (summer pattern). Conclusion: Flows from the high altitude subtropical East lead to cold advection air of higher altitudes toward east and north east of Iran. But withdrawal of subtropical high pressure was the main factor of cool waves in this pattern. Siberian high pressure has caused low difference of daily minimum and maximum temperature in northeast of Iran and Alborz mountains in the autumn pattern (third pattern). Wind speed in North of Iran was more than the other region. And also stability conditions was the most in this pattern. There was low differences between minimum and maximum in south of Zagros mountains that was due to advection of cold air by African high pressure. In late autumn and early winter pattern (forth pattern) a complete advective Pattern is ruling over country. The fifth class (winter pattern) is advective-Radiative.

river erosion is always one of the main factors in the risk of energy transmission lines and oil and gas pipelines. In this paper, using the Pipeline Risk Screening Matrix (PRSM) and the ANP model, stream pipelines in the Iran gas trunk – line 9 (IGAT 9), in the province of Khuzestan with a length of 170 km were investigated. For this purpose, using the ANP model, four main categories of criteria were included: the criteria "pipeline situation to the streams", "Hydrogeomorphology", "geomorphology" and "other environmental factors", with 36 sub-criteria, then using the PRSM model and the questionnaire were sub-criteria scoring in the Super decision software, as well as a pipeline hazard risk classification map. The results showed that the "pipeline situation to the streams" criterion has the highest risk and response to pipeline hazards among the four criteria. The most important sub-criteria with the highest risk profile are construction method, mountain, drainage and geology. Risk map is also in the range of Shushtar and km 150+ to 170+ in east of Dezful. The 9th gas pipeline has the highest risk situation and increased stream and rivers response in mountain geomorphology unit.

Introduction: Phenomenologists believe that in nature there is a dual structure that depends on each other intrinsically, one is a structure that is objectively visible to any observer, and second the complex and interconnected structures that are not exposed to tangible objectivity. Geomorphology, based on the phenomenological view, also tries to understand non-tangible structures. Damavand Peak is a Quaternary volcanic phenomenon with an altitude of 5671 meters in the middle of Alborz sedimentary ridge. This phenomenon has changed the overall structure of the region and imposed certain changes on the whole Alborz region. Damavand has a different structure compared to other volcanoes, such as Sahand, Bazman and Kilimanjaro, and does not follow the radial form. It has the shape of the Owl's Eye. The main goal in this paper, is to clear the effects of structure on the behavior of the Haraz River and emphasize to spatial memory, energy distribution pattern and the changes of river flow. Materials and Methods: The variables used in this research are mostly those of defining the structural pattern of the region. These variables are classified into three groups, linear, point and superficial, often defining-geometric patterns are considered in geomorphology. The variables analyzed here are i) the linear variables comprising fault lines, drainage networks, ii) the surface variables including the erosional surfaces along the Hazard River and iii) the points variables constituting the villages and peaks. All analyzes are based on satellite images and 30-meter DEM of Iran and the accuracy of these analyzes has been checked with field visiting (15 times). All of these information is presented in the framework of the phenomenological method, relying on the chaos theory, and the concepts of behavior geomorphology. Discussion and results: The special structure of Damavand and its activity, have been reflected on structure of region, behavior of Haraz River, capture river, and defined a new space identity. How Damavand has changed the structure of region. A: Changes in the fault systemsGenerally, structural patterns in the Alborz region have been influenced by fault activity. Damavand volcano as a new plutonic activity has changed the tectonic structure and plays a decisive role in structure of this region. Comparing the tectonic structure of region (without volcano's activity) with the current structure (after volcano's activity) revealed the new structure created by Damavand is considered as a turbulence in the general structure. B: Expand area of Haraz River basin. As shown in figure (3), there are three fault systems in the area. By evaluating and measuring the northern fault systems, the length of all this fault was 15 to 45 km, except that of Haraz with length reaching to 104 Km. This indicates that Damavand's activities have caused such a change in the area of draining basin. In other words, the Haraz River basin was much smaller, and after the volcanic activity its basin has increased sharply and all branches of the river that have already flown south (Tehran) have been redirected to the north. C: change the pattern of draining system. Investigating the drainage network in the area shows that the structure of the drainage network in Damavand has different patterns with other adjoining areas. As you can see, there are two distinct patterns in this area, one dendritic pattern and another spiral pattern. Changing draining patterns with Damavand volcanic activity is routine, but the Damavan rotational form is a special feature that separates it from other volcanoes such as Kilimanjaro, Bazman and Sahand. Because almost all of them have a radial form and Damavand has a structure Owl's eye model with a clockwise movement. This form has caused many processes to change and has had important effects on the distribution of energy and matter, especially in the Haraz River. D: How Damavand have changed behavior of Haraz River. The sediments of these lakes now are at higher elevation than the current level of rivers in the areas of Nandel, Baijan, Gazeneh, Lasem and Lar. The excavation started in the Lagos valley from mid-December 2017, confirming the depth of sediment, more than 100 meters, and this indicating the depth of the lakes. This process has made the river function as a continuous and normal flow is converted into a cascade stream. E: change the space identity. After overflow and breaking the lakes, along the banks of the rivers, sedimentary beds have been leftover and created numerous villages on them. This phenomenon in Iran means the change of space identity, because in the mountains of Iran, villages take their space identity from the Water-Ice Equilibrium line (WIEL). Conclusion: If we call geomorphology as a knowledge of land forms and analysis of patterns, we can claim that the Damavand volcano is different from the other volcanoes like Kilimanjaro, Sahand, Sabalan, and Bazman, and this difference is related to its chaotic structure. Damavand volcano have been affected on the environmental processes, such as the distribution of energy, matter and Haraz river behavior, and the main aim of this paper is to explain this. Although the patterns of the formal structure in Albourz Mountain are more influenced by the faults, the structure of the Damavand formative have completely confused the tectonic structures and changed the rule of formative system and behavior of Haraz River. The influence of structure in a variety of dimensions, such as the distribution of energy and matter on the region, river capture and river behavior, river basin expanding and sequences sediment has been able to create general space identity of this region. This article is the result of a studying in sabbatical leave at the University of Wurzburg based on the principles of phenomenology and the results is obtained show that: *The Damavand form has followed the structure of the Owl's eye model and created a land-cyclone. *Damavand has changed the patterns of distribution of energy and matter in this region, created a river capture and expanded the Haraz river network. *The structure of the owl's eye of Damavand Has been created a special space identity in this region.

Introduction: Climate change related issues increasingly received significant attentions in recent years due to its consequences in different viewpoints of economic, social and environment. In this regard, drawing guidance from vulnerability assessment as a process for characterization of watersheds against climatic components could provide strategic implications of climate change. Generally, vulnerability is considered as an ecosystem susceptibility state against to harm from exposure to stressors and from the lack of capability to adapt. Watersheds are greatly different in terms of their supporting values, exposure to climatic changes, and sensitivity. Therefore, understanding these differences could be helpful for the set priorities and selection of management attitudes. Depth understanding of climatic vulnerability changes in different environments is emphasized by the Intergovernmental Panel on Climate Change (IPCC). Not all parts of the specific watershed are equally vulnerable to climatic components. It is expected some parts are supported by more water resources, and some are inherently more sensitive to climate change. Moreover, ascertaining the magnitude of vulnerability in areas undergoing such changes is highly important for land managers and decision makers. The vulnerability assessments provide managerial recommendations to appropriately predict and respond to projected climate-hydrologic-land cover changes. Towards this important, the present study was planned as a case study to assess the climatic vulnerability of the Samian Watershed in Ardabil Province based on some important climatic and physiographic indices. Materials and methods: The present study was conducted in the Samian Watershed (ca. 4235 sq. km) with 27 sub-watersheds located in central of Ardabil Province, Iran. The mean annual precipitation in the study watershed is about 312. 25 mm, with temperature of 8. 2 ° C. A key component to implement a successful indicator-based approach is selecting the most reliable and suitable indicators for vulnerability assessment. Based on reviewing of the literature, to assess the climatic vulnerability of Samian Watershed, eight important indicators from climatic and physiographic aspects including dry and wet seasons, cold and warm periods, maximal wind speed, altitude above sea level and standardized precipitation index (SPI) were used. Thence, the Kolmogorov-Smirnov test was applied to determine the appropriate thresholds to distinguish the different classes of each used indicators. To determine the indicators related to rainfall, temperature and wind, the data of 16 stations which distributed through whole study watershed for the period of 1989– 2014 were provided and analyzed. In addition, the digital elevation model (DEM) and Drought Indices Package (DIP) were applied for indicators of altitude above sea level and standardized precipitation index (SPI), respectively. In overall, all indicators was classified between one to five scales based on the vulnerability intensity. Thereafter, the overall vulnerability point (OVP) were obtained for whole study watershed. Totally, all study climatic and physiographic indicators as well as overall vulnerability point (OVP) were mapped and interpreted through sub-watersheds under consideration. The interpolations were made using the Inverse Distance Weighted (IDW) and Thiessen processes in the ArcGIS 10. 6. Results and discussion: The results showed that the mean vulnerability of Samian Watershed based on climatic variations of dry season, wet season, cold period, warm period, maximal wind speed, altitude above sea level and SPI index were 65. 36 mm, 194. 86 mm, 0. 51 ° C, 15. 71 ° C, 55. 66 Km h-1, 1707 m and 0. 0026. The standard deviation of these indicators in that respect were obtained 9. 69, 34. 02, 1. 57, 0. 83, 15. 23, 304 and 0. 0020. The dry season index in the Samian Watershed area was varied in the range of 48. 05 (sub-watershed 21) to 86. 63 (sub-watershed 12) mm and the wet season index was within the range of 254. 99 (sub-watershed 16) to 130. 83 (sub-watershed 3) mm. The cold season index also ranged between-5. 87 (sub-watershed 8) to 2. 07 (sub-watershed 3) ° C and the warm season index fall in the range of 13. 03 (sub-watershed 8) to 16. 96 (sub-watershed 3) ° C. Furthermore, the maximum wind speed index varied between the ranges of 34. 20 (Sub-watershed 8) to 78. 48 (sub-watershed 1) Km h-1, altitude above sea level was between 1326 (sub-watershed 21) to 2596 (sub-watershed 14) and SPI index within the range of 0. 0006 (sub-watershed 16) up to 0. 0111 (sub-watershed 8). In addition, the results showed that among 27 sub-watersheds, sub-watersheds 15, 16 and 17 were grouped in high class and the sub-watersheds 20, 21 and 24 were grouped in resilient class in terms of overall vulnerability point (OVP). Besides, the variation of spatial distribution in the climatic vulnerability was clearly observed for Samian Watershed. However, main parts of the watershed is distinguished vulnerable. This findings confirmed the dynamics of the used indicators in evaluation of Samian Watershed vulnerability. In addition, the results showed the road maps for policy managers to provide meaningful management solutions for each sub-watershed based on every study indicators. The results of the research, while highlighting the importance of the effects of climate change, are necessary for their application in applying appropriate management and adaptation to climate change in the future policies of the watershed management. Therefore, the results can be used more as inputs for developing a comprehensive and integrated framework for climate change mitigation and adaptation solutions. In addition, the results of this study could be used to reduce or control the climate change risks in the Samian Watershed area. Conclusion: In the present research, the climatic vulnerability of Samian Watershed, Iran were assessed in terms of some significant climate and physical indicators. The results verified the spatial variations of vulnerability in terms of each study indicators and overall vulnerability through 27 sub-watersheds. This paper includes powerful tools and example of watershed-scale vulnerability assessments that could be a basis for jurisdictions around other places of Iran and the world. The results of the research, while highlighting the importance of the effects of climate change, are applicable to develop appropriate managerial and adaptation strategies in terms of climate change. Along with vulnerability increasing in different conditions, it is suggested to adjust and use more indicators with the addition of socioeconomic considerations and non-climatic factors. The findings also inform the associated organizations to give more attention to collect comprehensive data bank and facilitate equipping the watersheds for collecting high resolutions information related to vulnerability assessment in future studies.

Introduction: The urban heat island (UHI) effect is one of the main consequences of a changing nature in the cities. The heat island effect is the rise of the temperature in urban areas compared to the surrounding rural areas and today has become a very important issue in urban climatology. Rapid growth and insufficient attention to natural elements affecting the planning and implementation of urban plans has many environmental consequences, including the phenomenon of heat island that results from the concentration of human activities and land use/cover changes. Many studies established the correlation between expansion of urban green spaces and reduction in UHI intensity. However, higher economic values and lack of urban lands due to high density, population growth and etc. are the main limitation of green space expansion in horizontal scale in urban areas. In this regard, improvement in the surface cover of buildings and constructions that have been covered with cement and asphalt concrete is examined as one of the measures to mitigate the urban heat island phenomenon. Roofs constitute about 20– 25% of the urban surface. Conversion of traditional roofs into planted roofs or green roofs can give rise to many benefits such as mitigation of UHI effect, increase air quality, urban flood management, energy consumption management and etc. Tehran, as the capital of Iran, has a relatively irregular and unplanned urban design pattern. On the other hand, the per capita green space in this city is less than standard at global scale. Furthermore, the distribution of green space across the city is heterogeneous. Lack of green space across the city led to formation of UHI with multiple cores. Hence, the main objective of the present research is to explain and evaluate the effect of development of green roofs as a way to reduce the intensity of Tehran Heat Islands and regarding to lack of space in horizontal scale in Tehran. Materials and Methods: After reviewing library resources and previous studies, statistical combination method and numerical modeling of climate micro scale were used to study the effect of green roofs on the intensity adjustment of Heat islands of the city. In this study, the data obtained from field survey as well as the outputs of the Envi-met micro-scale model in the spring, summer and autumn periods, were used to extract the temperature difference between the two green roofs and the reference roof in 17 district of the Tehran’ s municipality. To collect field data two air temperature and relative humidity were installed both on the studied roofs (one meter above the selected green roof and reference roof located in 17 district of the Tehran’ s municipality). The time intervals for data recording was considered in 15 minutes. Then, the studied area was design using Envi-met micro-scale model to determine the ability of the model in simulation of the roof’ s materials impact on urban microclimate. Finally, the correlation between actual and simulated data were determined. Results and Discussion: Results demonstrated that, temperature difference between the hours of afternoon and night-time was greater than in the morning during the all studied seasons. Also, the maximum temperature difference between the two green roof and the reference one in this season was occurred at 00: 00 and 06: 00 A. M. while the maximum temperature differences was observed at 22: 00 P. M. Furthermore, the comparison of temperature in both studied roofs during the four seasons of the year illustrated the maximum differences between seasons was occurred in the autumn in comparison with other seasons. By examining the outputs of the model in terms of the actual situation in the area, it became clear that the amount of difference between the two studied roofs decrease as we approach the early morning hours. But in the afternoon there was an increase in the range that continues until night, and with numerical and graphical data analysis, it is determined that the maximum temperature difference between the two green roofs and the reference occurred at night. That is exactly when the heat island reaches its peak. Therefore, green roofs are one of the most important ways to adjust the intensity of the heat islands. On the other hand, to evaluate the accuracy of the Envi-met model for simulation of the reality, the simulated data were correlated with actual and measure data. Based on the results, simulated and actual data in spring and summer are moderately correlated (R=0. 53). While the correlation between simulated and actual data in autumn is low. Conclusion: Increasing the proportion of green spaces in urban areas has been recommended as one of the key UHI mitigation strategies in several research studies. Green infrastructure, including green roofs and green walls, is important for future urban forms. These infrastructure components have the potential to reduce temperatures in urban areas, particularly in the summer time and on individual hot days. in this regard, a methodology to test the resilience of the most commonly used UHI mitigation strategies in city of Tehran, Iran, was presented with assistance of simulation results using a prognostic three-dimensional microclimate model simulation (Envi-met). In addition, this research highlights the positive effects that vegetation has on the UHI mitigation, and at building scale. Indeed, green roofs are capable of decreasing the use of energy for cooling and heating and as a consequence, the peaks of energy use. Based on the results, the urban-wide conversion of the black roofs into white or green roofs can have positive effects not only on micro-scale, but also on urban scale. In conclusion, the microclimate study proved that a green roof retrofit will have significant impact on the rooftop microclimate. However, the expansion of vertical green spaces in the city of Tehran needs special incentive policies. Also, the function or the performance of a green roof needs to continue over time in order for the benefits to be realized. Therefore, the green roof must be properly maintained and reorganized at least each 2 years.

Introduction: The amount of agricultural production has a high correlation with atmospheric precipitations and the suitability of climatic conditions Knowing the factors that affect the plant developmental stages and the plant's sensitivity to the fluctuations of these factors makes it possible to make an appropriate decision for cultivation Provides. Plant tolerance thresholds are limited in relation to each meteorological parameter and any abnormality in these parameters can have a significant direct and indirect impact on agricultural production. Considering the important effects of climate factors on the yield of agricultural products, the introduction of indicators and agricultural variables that have the most impact in this regard seems necessary. Therefore, the present study aimed to investigate the effect of meteorological parameters on almond yield in West Azarbaijan province. Materials and methods: For this research, the weather data of 6 synoptic stations of Azarbayjan province during 2014-1985 period have been used. First, based on the growth degree day, almond growth season was calculated for each station, then the seasonal and temperature indices of temperature and precipitation, and the trends of each of them were extracted using the MK test and the slope of the senses. Finally, the amount of water needed for each phases of the product was estimated. The method used to estimate the reference evapotranspiration has been based on the FAO-Penman-Monteith method. Results and discussion: The results indicated that the average temperature of the growing season in the range of 0. 5 to 1 ° C in the year has an increasing trend. This is due to the increase of the maximum indexes of the growth season, the number of days with a maximum temperature of 90 ° , the average number of days with The maximum temperature is related to the 10th percentile (Tmax <10) and the number of days with a minimum temperature of less than 10k percentile (Tmin <10). Significant decrease in rainfall indices (rainfall rainfall season, maximum daily rainfall, number of rainy days and annual rainfall recorded on very wet days) was observed at all stations. Due to the increase in the temperature of the growing season and the reduction of rainfall, the product's water requirement ETC) has grown in the second and third stages. Conclusion: Climatic recognition and study of climatological needs of plants are the most important factors in production. The output of the index of growth-dgree day indicates that almond flowering at Mahabad station is earlier and starts at Takab station due to having higher altitudes and distances from the sea later than other regions. The shortest growth season for almond phenology is Takab with 207 days and the longest period of Mahabad with 250 days. Based on the Climatic recognition and study of climatological needs of plants are the most important factors in production. Based on the results of the study of temperature indices in West Azarbaijan province, it is possible to obtain a favorable climate for the cultivation of almond in the studied stations of Mahabad, Khoy and Piranshahr. It should be noted that including the limitations of the Piranshahr station, having a number of days with a minimum temperature of less than 2 degrees Celsius at flowering stage, due to the presence of the Mediterranean and its high mountain range, which should be taken to prevent spring frost to the late flowering cultivar. Also, Takab and Mako have the lowest temperature indices (the minimum freezing period, the number of days with a minimum temperature of less than 2 ° C at the flowering stage and the highest number of days with a minimum temperature of less than 0 ° ); hence, with regard to early flowering This product is not a good place to produce almonds in comparison with other fruits and are susceptible to late spring frost. The results of precipitation indices indicate a significant reduction of this parameter at all stations during the second and third stages of almond growth. Since this time coincides with the warm period and the increase in the number of days with maximum temperature, this dehydration during the main stages of growth has increased the moisture stress and this disrupted the growth process and led to a change in the size of the brain and decrease in efficiency The fruit is. Evapotranspiration analysis also shows that demand for water, especially in the second and third stages, has increased, hence, according to the stated content, the water needs of the product should be managed through water control and other environmental studies. Based on the results of the study of temperature indices in West Azarbaijan province, it is possible to obtain a favorable climate for the cultivation of almond in the studied stations of Mahabad, Khoy and Piranshahr. It should be noted that including the limitations of the Piranshahr station, having a number of days with a minimum temperature of less than 2 degrees Celsius at flowering stage, due to the presence of the Mediterranean and its high mountain range, which should be taken to prevent spring frost to the late flowering cultivar. Also, Takab and Mako have the lowest temperature indices (the minimum freezing period, the number of days with a minimum temperature of less than 2 ° C at the flowering stage and the highest number of days with a minimum temperature of less than 0 ° ); hence, with regard to early flowering This product is not a good place to produce almonds in comparison with other fruits and are susceptible to late spring frost. The results of precipitation indices indicate a significant reduction of this parameter at all stations during the second and third stages of almond growth. Since this time coincides with the warm period and the increase in the number of days with maximum temperature, this dehydration during the main stages of growth has increased the moisture stress and this disrupted the growth process and led to a change in the size of the brain and decrease in efficiency The fruit is. Evapotranspiration analysis also shows that demand for water, especially in the second and third stages, has increased, hence, according to the stated content, the water needs of the product should be managed through water control and other environmental studies.

Terrain morphology, provides a lot information for researchers in the field of environmental science. One of the goals in geomorphology is identification, and analyzing terrain landforms. In the past, the identification of landforms was performing field-based or using topographical maps. Manually, which was time-consuming and difficult, and in vast areas, it was facing many problems. In this article we had attempted to identify glacial and sub glacial landforms including: glacial cirque, glacial sinkhole (Tarn Lake), summit, saddle, ridgeline, drainage line, and sedimentary fans. For recognizing these landforms, two modelling approaches have followed. First is a conceptual modeling, which uses kernel pattern modeling. This modeling level, provides the condition in which, terrain morphology compares to the reference pattern. Second is an object-based modeling, which uses reference object to recognize landforms. Above mentioned landforms, considered in this research, recognizes, using both modeling approaches, and the results represents in the form of maps. Some typical landforms considered to make accuracy assessment and performance control, for each model output possible. To automate modeling procedures, Python programming language used widely. Eventually, all codes and scripts prepared in the build-in Graphical User Interface (GUI) programming environment of python (Tkinter), and the software, named: Landform Detector V. 1 prepared. Accuracy assessment, shows that landform recognition process had performed with 60% in average, which respect to the landform complexity, is acceptable. Average accuracy of the considered models are equal to 51. 58 % and 50. 60 % for conceptual and object-based approaches, respectively. In result, object-based approach had a better performance overall.

Introduction: Frost and freezing are important and risk generating factor in the agricultural sector of the country. Frost is a phenomenon that at low temperatures which could damage or destruct the plant organs. Various studies by researchers show that last spring frost (LSF) and first autumn frost (FAF) along with gradual global warming have significant impacts on agriculture and natural resources. Teleconnection patterns represent large changes which can periodically alter other atmospheric patterns such as temperature, wind, humidity and precipitation in regional and global scales. The purpose of this study was to investigate the effect of different teleconnection indices on variability of FAF and LSF events during the last 31 years at 12 Synoptic stations of Iran. Materials and Methods: To detect the relationships between frost events and teleconnection patterns we used two different data sources. As the first source, the screen daily minimum air temperature (Tmin) were used as the frost indicator. We also applied 10 different teleconnection indices in daily and monthly scales. Daily minimum air temperature were obtained from the Iran Meteorological Organization (IRIMO) for the historical period of 1985-2015. The teleconnection indices were also utilized for the same period (http: //www. cdo. noaa. gov). After the data quality control, the outlier data were removed from the analysis. Normality of data was evaluated by Kolmogorov-Smirnov test. For time series with normal distribution (P <0. 05), the Pearson’ s significance test was performed. For other time series, when the normal distribution was not the case, Spearman's nonparametric test was applied. Results and Discussion: In case of lag-free correlations in the monthly time scale the strongest correlation between teleconnection indices and minimum temperature was observed for NAO-(-0. 76), in February for Isfehan Station, which can cause a delay in occurrence of last spring frost. By applying the time lag to the correlation, the strongest correlation was found for AMO+ with time lag of 11 month. In seasonal time scale, the strongest lag-free correlations were found for AO-during the last spring frost (LSF). By applying time lag-correlation, the strongest correlation was evident between Tmin temperature and AMO+, indicating that this index was the most influencing teleconnections (with 3 seasons lag). In comparison with the normal phase, the occurrence of El Niñ o causes earlier autumn and spring frost events. In contrast, La Niñ a event will postpone the dates of autumn and spring frosts. This means that if La Niñ a occurs in winter, the strongest effect will be appeared in the autumn of the following year. The correlation between the El Niñ o, La Niñ a and Normal phases with minimum temperature showed that the La Niñ a phase has the highest effect on shifting the dates of the minimum temperature event. The strongest correlation between the minimum temperature of autumn and teleconnection patterns (correlation coefficient of 0. 382) was observed for AO-, highlighting the fact that the occurrence of the Negative phase of this phenomenon leads to the cause a delay in occurrence of first autumn frost (FAF). For the last spring frost (LSF), the strongest correlation was found for SOI-index (correlation coefficient of 0. 665) for Hamedan station, leading to early spring cold in the region. The correlation between the phases of the El Niñ o, La Niñ a and Normal with minimum temperatures showed that the La Niñ a phase has the most effective phase affecting the minimum temperature. The results of this research can be used for wise managing of risk factors and arranging appropriate time of planting agricultural products, as well as insurance for agricultural products. Conclusions: This study highlighted the impact of teleconnection phenomena on shifting the dates of autumn and spring frost. It was shown, that the occurrence of teleconnection can significantly shift the date of first and last frost in the study region. For some teleconnections cause the advance, but for others may postpone (up to 50 days) the frost event. We found different results for lag-free correlations compared to lag-correlations. For instance, for monthly analysis of lag-free correlations, the strongest correlation between teleconnection indices and minimum temperature was found for NAO-(-0. 76), but for lag correlations, the strongest correlation was found for AMO+. In comparison with the normal phase, the occurrence of El Niñ o causes earlier autumn and spring frost events. The results showed that Shifting the Date of First )Autumn( and Last )Spring( Frost Events at the stations were related to a number of teleconnection patterns such as AMO, SOI, NAO, AO and MEI. In contrast, La Niñ a event will postpone the dates of autumn and spring frosts. Further works are required to better understanding of the impacts of teleconnection events on other meteorological parameters such as humidity which was not investigated in this research.

Introduction: One of the important dimensions of human life is its interaction with nature. Establishment in ancient sites in each region indicates the close connection of humans to the natural environment. The geographic environment, especially its natural background, is the area of all actions and reactions from ground-based phenomena. Natural environment is the most important factor in the formation of human habitats, especially in different periods. Locating and distributing human settlements has a lot of natural phenomena, which means that the structure of the establishment, while influencing human foundations (culture, economics, etc. ), has formed in relation to natural foundations. Environmental powers provide the establishment of human settlements in a geographic space, and the spatial structure of each location also manifests the interaction between man and his surroundings. Environmental powers are referred to as the set of abilities, talents and environmental capabilities that exist in the natural-environment, social and economic. These powers include altitude, slope degree, slope direction, geological structure, fault, water resources, soil, vegetation and land use, each of which is a natural platform, which their influence on the distribution of human settlements, has an important role. According to the principle that humans are not habitually settled by accident, but the settled based on the type of resources and resources available, residential areas are chosen that have more primary resources and provide long-term productivity opportunities; Therefore, the ancient people in their choice of place of residence have considered environmental factors such as easy access to water and suitable land for agriculture, natural nutrients and minerals. Geographical locationSarafirozabad plain is one of the small Zagros plains that is located in the eastern and southeastern parts of Mahidasht and extends along it. This plain is located 38 kilometers south east of Kermanshah, and in terms of the natural position one of the marginal plains, but from the point of view of its adjacency to Mahidasht and finding of different past period, is important. This plain along with Mahidasht plain in Kermanshah due to its climatic features, special geographic location and strategic, resources and rich soil for agriculture and its location along the high road or high road of Khorasan in the area has long been attracted by human groups. In fact, this plain is a synclinal that is drained by the Merek River, and there are also large and small cones. In addition to that, there are two mountains southwest and northeast of the plain. In general, the Northeastern mountains is called the White or Sefid Mountain ( Kohe sefid), and has several peaks including the Comajar Peak (Kame Jar), Zangalian, Khora Taw and White Mountains. The southwest mountains are Less height and are known as the Nesar And includes the peaks of Nasar, Kellamol, Lal-Abad (Laleh-van), Sivolex, Shirnarmy, Bariqa and Ghale Qazi (Qela qazi). As we know, due to their favorable conditions in many parts of the world, cones have provided a good position for settle and human settlements since prehistoric times, and this has caused the area to be selected for this research. Materials and methods: The purpose of this study was to study of the role of environmental factors and their impact on the locating of the Neolithic sites of Sarfirouz Abad Plain, which was selected in 17 Neolithic sites of this region. To achieve the research objectives, 11 natural factors were considered including altitude, slope, direction of slope, distance from the river, streams and springs, distance from main roads and adjacent roads, type of vegetation, type of soil and distance from today's villages as environmental or Independent variable and area of ancient sites were considered as dependent variable. ArcGIS software was used to investigate these factors and generate and analyze maps. During this process base maps were first provided and then analyzed the settlements in relation to each layer. Finally, SPSS software and quantitative analysis method especially Pearson correlation was used to determine the correlation between natural factors and spatial distribution of settlements. In addition, multiple linear regressions were used to examine the effect of independent variables on the dependent variable. Discussion and results: In the distribution of settlements of the Neolithic period of Sarfirouzabad plain, the distance from seasonal sources of water such as streams and seasonal rivers with a correlation coefficient of /665 and distance from subordinate or dirt-road with the significant level of 0/01 have the most effect. The degree of slope of the area around the sites with a correlation coefficient of /546 with a significant level of 0/05. Is in the next position Other factors, such as distance from the river and main sources of water, vegetation type and altitude, have been effective, but their degree of influence is moderate and low. It is noteworthy that the intensity of these factors in relation to the Neolithic sites with using multiple linear regression analysis is equal to 0. 920. This number is extremely high correlation between environmental factors and the extent of sites and the results of the regression indicate that the distribution of Neolithic settlements in relation to ecological and environmental constraints have discipline. The Neolithic settlements in this area indicate easy access to pastures and water and express the dependence of the people of this period on animal husbandry. In the newer period, most of the Neolithic sites in the central Zagros have been scattered on fertile lands and within low distance from the seasonal sources of water or springs. In fact, these types of sites are located close to the foothills of the mountains and the hills, and it also reveals the theory of exploiting the foothills resources., in addition to the resettlement of new fertile areas in the late Neolithic period in the region, has been exploited more intensively due to the development of agricultural activities, the fertile and water-rich areas that were previously inhabited. Proximity to fertile lands and focusing on near-meadows and habitats on low sloping is likely to be a sign of relying on agriculture, as well as relying on livestock farming and exploitation of mountainous natural resources.

Introduction: Monitoring the tropopause features over a geographic area is important for a number of interrelated reasons. From a climatological point of view, it is important to investigate the behaviour of the tropopause charactreristics for a long term, so that to detect any increased or decreased trends. From a dynamic point of view, it is essential to define the tropopause hieght, in order to explore the stratosphere— troposphere exchange taking place over a geographic area that may be responsible for changes in the chemical composition of the atmosphere. Over the past two decades, there has been growing interest in the tropopause charactreristics among the atmospheric scientific community. It is now broadly accepted that the tropopause plays a key role in a variety of atmospheric and climatic phenomena. Materials and methods: Compared to studies performed globally, in Iran a limited number of studies concerning the tropopause have been conducted. Moreover, the methods have been used and the length of the dataset were often inadequate. Therefore, in the present study, for the detection of tropopause, the daily data of Temperature, and Geopotential Height from the European Centre for Medium-Range Weather Forecasts (ECMWF) for 700 to 50 hpa with a spatial resolution of 0. 25 × 0. 25 longitude/latitude from 1979 to 2018 was adopted. Accordingly, 2491 cells have been covered across Iran. The LRT was used to detect tropopause. the tropopause is defined as ‘ ‘ the lowest level at which the lapse-rate decreases to 2 /km or less, provided that the average lapse-rate between this level and all higher levels within 2 km does not exceed 2C/km. In this study, in addition to the tropopause pressure level, the tropopause height (m) was also evaluated during this period. To obtain better cognitive knowledge about tropopause, the factors that were likely to be related to the spatial changes in height of tropopause were investigated. To achieve this goal, the relationship between tropopause pressure and spatial variables (e. g. longitude, latitude, and elevation) was assessed by general and partial linear correlation ceofeicents. In addition to the characteristics of temperature at the lower and upper levels of the tropopause, the difference in temperature between these two levels on the atmosphere of Iran and the characteristics of the minimum, maximum, average, as well as the temperature range of the earth's surface were evaluated and their relationship with tropopause pressure levels and height levels was assessed. Results and discussion: Investigating the characteristics of tropopause on the atmosphere of the studied area in the under investigation period (1979 to 2018) and its related factors in the autumn and spring months showed that in the months of these two seasons, various factors affecting height and pressure levels of tropopause are diffrnt and in both seasons have different characteristics. In all spring and autumn except for September, the height of the tropopause is decreasing as the latitude increases, but in October and November, the rate of change was greater than in the other months. In all the months of these two seasons (except September), the highest level of the tropopause taking place in the south-east of the country, whilst the lowest level of pressure occured in the north-west of the country. Investigating the changes in tropopause height and tropopause pressure levels also showed that they were not consistent in the under investigation seasons, so that in places with similar pressure levels, observed elevations were different. the tropopause pressure levels have a strong relation with the latitude, but changes in the tropopause height did not show a regular relationship with latitude. Tropopause height changes are mostly irregular in spring and autumn, and in parts of the country, it is almost dependent on longitude. In the spring and autumn periods, the high and low tropopause levels are among the most influential factors on tropopause. Among the cases that were related to the tropopause were surface temperatures and their characteristics in the spring and autumn seasons. During these two seasons, it was found that the potantial relationship of surface temperatures with tropopause pressure and elevation levels, especially at high latitudes, is low, but in lower latitudes, due to limited variation in the surface temperature, the potantial connection of tropopause and surface temperatures are higher than other parts of the country. In the months of the spring and October and November, it was revealed that the potantial correlation between tropopause pressure and elevation levels with local factors was low, but in September in parts of the country, the effects of surface elevations on the levels of tropopause pressure is much more significent. Conclusion: The results of the study of the tropopause and its related factors showed that the trend of tropopause pressure changes in the vicinity of latitude is decreasing with increasing the latitude. But the tropopause height is not aligned with its pressure levels, and in most areas, it is in the vicinity of Longitude. Among the studied factors, the low and high levels of tropopause have the highest impact on the tropopause, and the effects of surface temperature and other examined cases have not a noticable impact. he results of the study of the tropopause and its related factors showed that the trend of tropopause pressure changes in the vicinity of latitude is decreasing with increasing the latitude. But the tropopause height is not aligned with its pressure levels, and in most areas, it is in the vicinity of Longitude. Among the studied factors, the low and high levels of tropopause have the highest impact on the tropopause, and the effects of surface temperature and other examined cases have not a noticable impact. he results of the study of the tropopause and its related factors showed that the trend of tropopause pressure changes in the vicinity of latitude is decreasing with increasing the latitude. But the tropopause height is not aligned with its pressure levels, and in most areas, it is in the vicinity of Longitude. Among the studied factors, the low and high levels of tropopause have the highest impact on the tropopause, and the effects of surface temperature and other examined cases have not a noticable impact.