جستجوی مقالات مرتبط با کلیدواژه « climate hazards » در نشریات گروه « جغرافیا »

The existence of climate variability (especially temperature) and more importantly its fluctuations and changes in different regions of the country can have different effects on its railway lines. Fluctuations and temperature changes can affect many different aspects of the rail transportation system, especially rail instabilities; Therefore, evaluating the effect of climatic conditions, especially fluctuations and temperature changes on railway instabilities, requires a more accurate analysis of the relationship between these two variables, which is the goal of this research. In this research, the General Circulation Model has been used in order to predict long-term temperature and analyze its effects on railway lines. For local and regional forecasts SDSM statistical microscale exponential method was used. The data used in this research includes the monthly average data of the synoptic stations of Kerman, Bam and Zahedan with the base period of 1961-1990 and Hadcm3 model data (data of the third generation of the global climate model under scenario A2 and B2). The temperature was predicted for three periods of 2011-2040, 2041-2070 and 2071-2099 and compared with the base period. The SDSM model works correctly in the microscale rotation of HadCM3 model output temperature in all three stations with a small difference and has acceptable accuracy for temperature prediction. Except in Zahedan area in some cold months of the year, we see an increase in temperature in all months of the year in the stations and this increase in temperature will reach its peak in 2099.

The tourism industry is one of the most important economic activities that plays an important role in the development of cities and has grown significantly in recent years. This industry is sensitive to weather changes and any change in weather affects the quantity and quality of this industry. Isfahan is considered one of the important tourist destinations and has always been threatened by weather hazards; Therefore, the present study was conducted with the aim of investigating the impact of weather hazards on the number of Iranian tourists in Isfahan city. In this regard, from the total precipitation data, the absolute minimum temperature, the absolute maximum temperature, the maximum 24-hour precipitation, the number of days with dust, the number of days with frost, the air quality index and the statistics of the number of tourists in Isfahan city during the statistical period of 2008-2019 in the scale Used monthly. First, using linear regression and Pearson's correlation, the relationship between the studied hazards and the number of tourists was investigated. In the following, their relationship was done with one-month, two-month and one-year delays. The results of the conducted studies indicate that dust, extreme heat, drought and air quality index in hot months and extreme cold, heavy rain and dust in cold months have an effect on the number of tourists. On an annual scale, Farin colds, Farin heats and freezing days have affected the number of tourists in almost all the studied years. The study of the studied time series also indicates the effect of freezing days, freezing temperatures, freezing temperatures, dust and air quality index on the number of tourists.

Developing countries are severely vulnerable to climate hazards. Global changes in climate patterns and events alter the quality and access to natural resources which leads to a widespread impact on their social and economic systems which is a kind of threat to today's societies and future generations. Rural communities are among the areas most affected by climate hazards and fluctuations, which require adaptive action to protect their livelihoods from the effects of climate hazards, which requires understanding and adaptation measures. The purpose of this study was to investigate the adaptation capacity and its components to climate hazards in two villages of Sefidbarg and Bivandsofla using a combined descriptive-analytic approach based on questionnaire data. The variables included in this study include individual characteristics and adaptation indices to climate hazards including economic, social, infrastructure, personal knowledge, and government. Effectiveness of each component and analysis of data collected were analyzed using statistical techniques. The results showed that the local communities of Bivandsofla village with average of 2.33 and Sefidbarg village with average of 2.88 have low adaptation capacity in the face of climate hazards phenomenon, and low adaptation capacity of these two villages directly related with economic, social, infrastructure, individual knowledge and the government. The infrastructure component also has the highest adaptation capacity and the economic, social, individual knowledge and government components have the lowest adaptability capacity. It is therefore necessary to pay special attention to improving the capacity of societies to adapt to the economic, social, individual and governmental components. Prior knowledge of the factors affecting adaptation capacity and the provision of supportive policies by related organizations may allow for increased adaptive capacity in planning change management strategies.

The occurrence of climatic hazards is one of the main characteristics of the climate of Iran, which it always has economic, social, and financial losses. Undoubtedly, the first step in reducing the climate impact of the country is to identify the causes of these hazards. Sea level pressure is one of the most important climatic elements that can affect important climatic factors such as temperature, rainfall and wind that cause climate hazards. Increase or decrease severity and the expansion of the eastern and northern levels of sea level pressure centers is one of major determinants of dry and humid periods in Iran. The study of published works and resources shows that a comprehensive study is required on changes in Iranian sea surface pressure in different seasons. Therefore, the purpose of this study is to reveal the trend of sea level pressure changes in different seasons. For this purpose, sea level data with NC format at 12 GMT Obtained from the NCEP / NCAR database from 1948 to 2016. Afterward, to obtain the seasonal categorization and mapping, the next steps were converted to TXT, Matlab, EXCEL, and GIS formats. Then, long-term changes in sea surface pressure were revealed. Study of time series trend diagram as well as values of mean, average, minimum, and average of maximum sea level pressure with the Mann Kendall test in different seasons showed that the level of significance level in all cases is smaller than 0.05, and the average annual pressure level of the Iranian sea has a significant upward trend, which is increasing by 0.047 hpa per year. The average 10-year map of Iran's surface pressure was similar in different seasons, and the average pressure dropped from the north of Iran to the south. Anomalous maps of the mean of ten years of sea-surface pressure showed that anomalous amounts have reached their highest positive levels in recent decades. Considering the importance of the issue and the vulnerability of the country to environmental hazards, it is clear that climate risk management will have a higher chance of success and credibility with increasing sea-level pressure.

Tehran, in the south of Alborz Mountains, is faced with three types of weather risk, weather risk caused by geography, climatic risks caused by air resistance and weather risk due to global warming. The aim of this study is to examine the three types of risk in Tehran. The method of this study was to evaluate the changes of synoptic factors that affect global warming and urban development. In order to detect the height changes of 500 hPa two 5-year periods including 1948 to 1952 and 2010 to 2014, were studied. The results showed that changes in heights of 500 geopotential, there was an increased risk in the city of Tehran. The effect of climate change in recent decades, increased the stability of air in Tehran. Human factors in the formation of heat islands, increase LCL height and density of the air balance is transferred to a higher altitude. Changing urban wind field, atmospheric turbulence intensified, exacerbated thermodynamic gradient, fat and refugee cyclones, heat island effect of the city.
Thermal stability in the warm period will appear. The thermal stability of all levels of lower, middle and upper troposphere was intensified. Thermal stability couraged the development of subtropical high pressure in the area. With the arrival of the atmospheric pressure during calm and humid days the stability and pollution were increased. Negative vorticity from early June developed the intensive high pressure over the region. Compare the conditions of the two study periods showed that : the height of the high pressure was 100 meters higher than the second period. The number of days of intensified subtropical high increased during the second period. The high pressure has moved to the northern areas during the second period. This change in the subtropical high pressure increased the dry periods motivating the loss of vegetation. Heat island effect was increased as well. More than 90% of the temperature inversions occurred at an altitude of less than 500 meters in both warm and cold periods of year. Wind direction at both stations has shown that the establishment of any pollutant source in the West of Tehran will increase the pollution.

Thunderstorms pose a significant threat to modern societies and their assets. Despite their local-scale characteristics، severe thunderstorms and associated extreme events like heavy rainfall، hail، gusts، or tornadoes، cause considerable damage to agriculture، buildings، or infrastructure facilities. Thunderstorms are highly localized and largely stationary weather systems affecting a limited area of about 20–50 km2، depending on the size of the cumulus tower. They are associated with shower clouds in which electrical discharges can be seen as lightning and heard as thunder on the ground، and they represent an advanced stage in the development of convection in moist air. The importance of rainfall generated by thunderstorms lies in the fact that it is largely torrential and of high intensity، and as a result much is lost as runoff which causes flooding. Basically thunderstorms occur more frequently above land areas in the warm season، while they are more frequent in the cold season over oceans. A lot of factors impact on their occurrence. Among them the most important are the thermodynamic and kinematic states of the atmosphere، topography، land cover، and its coastal configuration and atmospheric circulation issues. Ardabil is located in the northwest of the country، for this reason it has always been under the influence of the thunderstorms. Due to the geographic location and specific local conditions in this region، every year numerous thunderstorms happen in this area and cause severe damages in the agriculture، utilities and in restructure sectors. From this point of view، studying this phenomenon in detail and identifying the synoptic patterns of the ground surface and upper levels in which lead to the occurrence of thunderstorms in Ardebil are vital and important for the region. For this study، firstly the related data of Ardabil thunderstorms had been received from the Meteorological Agency of Ardabil. Within the related codes with the thunderstorms، codes from 90 to 99 during the period of 20 years (from 1992 to 2012) were used. After the initial Ardabil thunderstorm’s data analyzing، the 88 observational days that thunderstorm occurred in it were identified، and out of the 88 days، 43 days، that were compatible with the observational hours of4 for the NOAA data (3:30، 9:30، 15، 30، 21، 30) were used، for the patterning، so that the done research not to have any time contradiction with the upper atmosphere data and to be justified with the interpretation and analysis. Then، for the patterning and extraction of patterns in the upper atmosphere and ground surface، the related data to the pressure of the ground surface and geo potential height were obtained from the site which belongs to the National Center for Environmental Prediction (NCEP). So as to do this research the environmental to circulation method was used. In this case، first based on the recorded data in the Ardabil station، the occurred thunderstorms were identified and then by using the clustering، extraction and identification of the patterns for the ground surface and upper atmosphere launched، that leading to the occurrence of this phenomenon. For the classification and extraction of the ground surface pressure patterns and geo-potential height with the level of 500 hpa، the diverse kinds of hierarchical clustering methods tested، and finally based on the results، the clustering method into the Euclidean distance was known as the best method and the results of that were reflected in the following research. Result and Discuss: According to the results of hierarchical clustering، 4 patterns on the ground surface and in the level of 500 hpa were identified that the extracted patterns could justify beautifully the Ardabil thunderstorm occurrence. The ground surface patterns that lead to the occurrence of thunderstorms include pattern 1: the formation of low pressure on India، Siberia and high pressure on northern Europe and west of China، pattern 2: the formation of low pressure on the Ganges Valley، Persian Gulf and North Europe and high pressure on Siberia and west of China، pattern 3: the formation of low pressure on India and Persian Gulf and high pressure on Siberia and west of China، pattern 4: the formation of high-pressure on the central Asia and front occurring in the northwest of Iran. Also the patterns of geo-potential height with the level of500 hpa that lead to the occurrence of thunderstorms include pattern 1: the formation of the trough on the east Mediterranean and the placement of Ardabil in east of trough، pattern 2: the formation of the omega blocking on the northern parts of the Caspian sea and placement of Ardabil in southwest of that، pattern 3: the occurring of the cut-off blocking with low pressure on the central and east of the Turkey and placement of the Ardabil in east of the trough made by that، and pattern 4: the occurring split flow blocking in central Europe and placement of the Ardabil in east of trough. Different patterns according to the results of hierarchical clustering in the ground surface and in upper atmosphere are impressive on Ardabil thunderstorm precipitation. In the ground surface، the formation of low pressure on the Ganges valley، southwest of Persian Gulf، Siberia and northern Europe، also high pressure on the northern Europe، Siberia، west of China and the Central Asia played a significant role in the thunder precipitation occurrence. On the other hand in upper atmosphere، the study area in the east of trough and the formation of different patterns of blocking (omega، Split flow and cut-off low pressure) provided the condition so the thunder precipitation in Ardabil to be occurred.

Hail is one of the destructive atmospheric phenomenons that are caused wide destruction in different section economic including agriculture. The target of this research is recognition the synoptic patterns and determine the quantitative dynamic thresholds such as relative vorticity، divergence and convergence of humidity، vertical motion and also thermodynamic quantities such as specific humidity and streamline from 48 hours before the storm begin to start until it reaches to peak.. For synoptic analysis of hailstorm the daily map of 4 may 1997 were drawn from 48 hours before storm generation.

Annually, climate hazard in Iran leave financial and man loss. According to this, acquaintance and asses this hazards include high importance in order to reduce its effects. Regarding to the vast geographical extension of Iran and unsuitable dispense of land sensing stations, access and gathering land hazards data had encountered many problems and difficulties. Today, developing technology of remote sensing, there have been made great opportunities in gathering and assess hazards. In this research, dust storms hazard in July 1, 2nd 2008 in Khuzestan, flood in Feb 11, 2005 in Chabahar and Gono in 6 Jon 2007 have chosen for consideration and study. Assess this hazard have been made by AVHRR, MODIS, SEAWIFS, VISSR sensors and also TM and MSS, in some cases.
In the current research, visual observation method has been used for hazard recognition in images. In this method, for hazard recognition, we use features such as: tone, color,shape, size and tissue that each one are as an appear characteristics. Besides, color composite images (RGB) has been used for detect hazards with special color, in this research. Ultimately geometrical correction did on images for assess the cover surface. The study results show that for hazard tracing, high temporal resolution sensors and for inform of details and source of spatial resolution hazards, are practical and useful. For detection dust storms, the SEAWIFS, MODIS and also MODIS sensor has been introduced more useful than other sensor also for flood detection. METEOSAT satellite sensor has been introduced as the best sensor for assess the heavy rainfall because of super temporal resolution (each 15 – 30 min).