نشریه جغرافیا و مخاطرات محیطی
پیاپی 13 (بهار 1394)

Identification and analysis of time-series behavior of the climatic elements and processes upon them are the basic factors of climatology science and has an important role in management and environmental planning. In general، the behavior of climatic elements are observed in 3 form: Trend، Oscillation and Fluctuation. These behaviors will help us to identify more the climate change. Today by changing more the trend of climatic elements، climate change has become more important than previous years. But in between the climatic elements، it has been noticed less than the other elements such as water vapor pressure. The importance of water vapor is that this climatic parameter is has an important role in explaining the climate change، because of 1) It is the main source of rainfall in all weather systems، 2) It supplies the latent heat in this process and controls the heat in the troposphere and 3) It is the intensify severe storms. Given the significant role of atmospheric moisture in the Earth''s energy equilibrium، it can be helpful in explaining climate change. Therefore، this article tries to survey two time series behaviors of climate data; the trends and fluctuations in water vapor pressure. The Mann-Kendall test is one of the popular nonparametric techniques for explaining the trend analyzing in hydrological and climatic data. The spectrum analysis is one of the best methods for extracting and analyzing visible and invisible climatic oscillations with different wavelength. In fact، spectrum show the distribution of variance along the entire range of wavelengths in time series. So in this article، we want to analyze the trend by using the Mann-Kendall test and detect and identify the fluctuations and cycles of water vapor pressure time series by using the spectrum analysis. Study area: The study area، with about 360،200 km2 area، is located in the south and southwest of Iran and approximately between 25° 00''N and 34° 25''N latitudes and between 45° 38''E and 59° 17''E longitudes. Southern and southwestern parts of the study area is located in sides of two massive sources of moisture، Persian Gulf and Oman Sea.

In this study، water vapor pressure data from 28 synoptic stations، during a period of more than 20 years in south and southwest of Iran were used that were collected by the Iranian Meteorological data website (http: //www. weather. ir). It should be noted that to survey the Mann-Kendall test and Spectral analysis، the stations with 44-years period (2010-1967) and stations that have data since their establishment were used، respectively. The methodology of this study is detecting trends and oscillation of water vapor pressure in south and southwest of Iran by Mann-Kendal test and Spectral analysis، respectively based on ground station. Tests for the detection of significant trends in climatological time series can be classified as parametric and non-parametric methods. Parametric trend tests require data to be independent and normally distributed، while non-parametric trend tests require only that the data be independent. In this study، a non-parametric method، Mann-Kendal، was used to detect trends. To analyze the Oscillation of water vapor pressure، the spectral analysis has been applied. In this function، frequency and cycles indicate the time scale and amount of variance in the time scale، respectively. After extracting all waves، in second step the proportion of each waves in explaining the total variance are specified and Finally، the significance of each waves are tested. For performing the Mann-Kendall test and spectrum analysis technique، the capability of programming in MATLAB software was used.

The results showed significant trend in most of the stations. As the results of this article، the downward significant trend in the stations of Ahwaz، Bandarabas، Shahrekord، Boroujen، Abadeh and Khorramabad، the upward significant trend in Lengeh، Bushehr، Dezful and non-significant trend in Abadan، Fasa and Shiraz was seen. By applying the spectrum analyzing in 95% confidence level on the water vapor pressure data، the multiple cycles were obtained; So that the significant sinusoidal cycles 3-2، 4 and 15-7 years were more common. Results show that the cycles of 3-2 years was most repeated in the water vapor pressure time series. 4-year cycle was the other cycle of events occurred in the study area that researchers have attributed this cycle to ENSO. The survey showed that more cycles are traceable in the southern part of the Zagros. Another cycle in the region was 15-7 year cycle that most scientists have attributed this cycle to sunspot activity. The final survey showed that the plurality of cycles in the West and South West of the study area.

In general it can be concluded that the downward significant trend of water vapor pressure was observed in the Zagros and the upward significant trend was observed in nearby the Persian Gulf. By applying the spectrum analyzing on the water vapor pressure data، the multiple cycles were obtained. Results of spectral analysis showed that the cycles of 3-2 years was most repeated in the water vapor pressure time series. The spatial distribution of this cycle was observed in the near of Persian Gulf coasts. Most scientists have attributed this cycle as a result of El Niño - Southern Oscillation (ENSO) and Quasi-biennial oscillation (QBO).

Traditional knowledge (TK)، indigenous knowledge (IK)، traditional ecological knowledge (TEK) and local knowledge generally refer to knowledge systems embedded in the cultural traditions of regional، indigenous، or local communities. Traditional knowledge includes types of knowledge about traditional technologies of subsistence (e. g. tools and techniques for hunting or agriculture)، midwifery، ethno botany and ecological knowledge، celestial navigation، ethno astronomy، the climate etc. These kinds of knowledge are crucial for the subsistence and survival and are generally based on accumulations of empirical observation and interaction with the environment. In many cases، traditional knowledge has been orally passed for generations from person to person. Some forms of traditional knowledge are expressed through stories، legends، folklore، rituals، songs، and even laws. Other forms of traditional knowledge are expressed through different means. A natural hazard is a threat of a naturally occurring event that will have a negative effect on people or the environment. Many natural hazards are interrelated، e. g. earthquakes can cause tsunamis and drought can lead directly to famine or population displacement. It is possible that some natural hazards are inter-temporally correlated، as well. A concrete example of the division between a natural hazard and a natural disaster is that the 1906 San Francisco earthquake was a disaster، whereas living on a fault line is a hazard. Natural hazard is an important challenge in rural development. It is important that we control it for decreasing harm. Domestic method is a good method in rural development especially hazard control. Study of literature of natural hazards management show that today approach of action to hazard with imperative-control and technology structure change to new approach that it calls social management. It focuses on culture، capacity، and local society knowledge. In this paper we study this question: • How is role of local and modern Knowledge in decreasing of environmental harm in studied region? Study area: Harsinis city of Kermanshah province that has both the Central and Biston. Harsin city in the 2005 census has a population of over 91،300 people، 53،731 of whom are urban and 37،569 rural people، where almost two-thirds of its population is urban population. This paper did in Shirz rural district. This place is in Harsin County in Kermanshah province. Harsin is a city in and the capital of Harsin County، Kermanshah Province، Iran. At the 2006 census، its population was 51،562، in 12،001 families. Harsin is situated 44 km east of Kermanshah، and lies 1،570 meters (5،150 ft) above sea level. The rural county has 13 villages and its crowd equal with 10992. Shizr rural district has 13 villages and a population of over 10،992 people according to the 2006 census. Villages in the region naturally into three groups in terms of the plains، foothills، and mountains are. Most villages in the district of which are plain wheat، horticulture and animal husbandry are the main activities of the villagers in this area

Investigative method was descriptive-analysis and survey method. We used from questionnaire، interview with people، seeing for collecting data. This paper studies this assumption: domestic knowledge have larger slice than new knowledge about natural damage (cold، glacial and dry) in Shirz County. In this paper we used from SPSS software and Fisher test. For study of local knowledge we used from investigative methods for example، seeing، speaking with people and older people and for new knowledge we used from questionnaire and interview. A survey of the rural population in the sample villages are 50 years or older. According to ID Villages in 1385 the total number of villages in this part of the 13 villages، of which nine villages were randomly selected using random sampling and Cochran is 95% and the accuracy of probability of 0. 09، sample size n = 90 is calculated، all the age group 50 years and above were selected. The number of samples obtained for each village with the appropriatenessSocial statistic was 90 people that selected by Cochran method. We used from random sampling.

The first we study variety of hazard for example، drought، flood and cold. In local method، source teaching was rural chief، family and important people but in mother method school and education method were important. Help source in local method were important people but in modern method were government institute for example Basij. In assumption test we understand that total of modern and local method is better from mother method. The effectiveness of local knowledge، modern and a combination of both new knowledge to reduce vulnerability to cold and freezing in three components: environmental، economic and social impacts were assessed. As is evident from the paper that the average difference between the effectiveness of local knowledge in reducing the damaging affect of cold and frost in combination of three components: environmental، economic and social there. Effectiveness of local knowledge in each of the environmental components، the average efficiency of new knowledge in the social and economic dimensions of environmental، economic، social and greater knowledge of the effect of the combination of the two. The effectiveness of a combination of the two knowledge in each of the three components of environmental، social and economic effectiveness of new knowledge is higher than average. Therefore، the effectiveness of local knowledge with modern knowledge to reduces the effects of cold Confirmed. Results say that there are different between domestic knowledge and new knowledge in decreasing natural hazard damage and domestic knowledge have larger slice than new knowledge in natural hazard management in rural area. This paper says that we cannot dope economic، cultural and social phenomenon. For controlling natural hazard present some modern tools. But we believe that local methods are profit and better those modern tools. In this study، comparison of indigenous knowledge، new and evaluated the combination of the two. In the case of floods and droughts and cold، as well as more rural indigenous knowledge of two other statuses (new، combined) are.

The results show that indigenous knowledge in many cases is better to deal with natural disasters. However، modern science''s role in reducing risks cannot be ignored. Local communities use from the different procedures for managing the risk of natural hazards. Government uses from modern procedures. Because each has unique characteristics and they can together have a better performance. Therefore we recommended that modern and local procedures merge together for better function

Temperature effects on human activities and natural processes are undeniable. Temperature increase، in particular، in the form of heat waves affects all facets of life including architecture، welfare، transport، agriculture and industry. When the intensity and frequency of the waves are high، they can produce major problems. In recent years، the number and intensity of these heat waves has been increased in the world، so that it is one of the major causes of atmosphere related mortality in many countries. The aim of this study is to analyze the temperatures above 40°C and specify their synoptic patterns in the west of Iran using statistical-synoptic method. Study area: Study area in this paper consists of five western provinces of Iran، including Kermanshah، Kurdistan، Hamedan، Lorestan and Ilam. From the climatic point of view، southern and western parts of the region including Khorramabad and Ilam stations are placed in the outer foothills climatic zone، and the other parts of this region are placed in the mountainous zone. Western low altitude strip has a warmer climate; But the other parts because of having different altitudes and latitudes، have colder climate. To achieve the statistical-synoptic analysis of heat waves، the daily maximum temperature data of six synoptic stations of the region within a 32-year period (1976-2007)، and the relevant synoptic maps were used in this study. Different criteria have been proposed for selecting a numerical threshold for defining the superhot temperatures and the occurrence of heat waves. In the present study، reaching a maximum daily temperature of 40°C and higher has been the basis for defining the heat wave based on the region''s temperature characteristics. Accordingly in each of these stations the dates in which the maximum temperature had reached 40°C and above during all those years were extracted. Then، based on the January 1st، each calendar date was converted to Julian date، and after that، the different characteristics of these superhot days like start date، duration and frequency were analyzed. Next، heat waves were derived based on two criteria: incidence of 40°C temperature and above at least in three stations، and three consecutive day occurrence of the above mentioned conditions. The beginning day of each wave was defined as the day when the temperature has reached 40°C or higher at the desired stations for the first time in compliance with the above conditions، and، the end day was defined as the day when the temperature reached the mentioned threshold for the last time. To calculate the mean temperature of a specific wave، maximum temperatures equal to 40°C and above at the all stations on all days of the occurrence of heat wave were used. To study the synoptic occurrence of heat waves، various data including geopotential height، sea level pressure، surface temperature، 1000-500 hPa thickness and meridional wind component at 200-hPa level were taken from NOAA''s Website. In the next step، different maps comprising mean sea level pressure and anomaly، 500-hPa geopotential height، warm air advection and 1000-500 hPa thickness were drawn using GrADS software. The assessment of maximum temperatures in the region resulted in the extraction of 27 heat waves. The usual date for the start of heat waves and rising the temperatures to 40°C or higher in the west of country is July 23. The highest frequency of heat waves in 1977 with 4 waves، the longest wave in 1995، continuing for 28 days، and the most severe wave in 1998 with an average temperature of 42. 4°C has occurred. The average length of waves in the region was 10 days، with the range of 3 to 28 days. In the mentioned period، Khorramabad and Kermanshah stations with respectively an annual average of 22. 5 and 13. 4 days had the highest amounts of 40°C temperatures and above، and in terms of duration and severity were among the hottest points of the region. Kermanshah station had the maximum number of superhot days after Khorramabad due to the high altitude and thin atmosphere. In contrast، duration and intensity of heat waves in Hamedan station was the least in the region. The results obtained from the synoptic analysis of heat waves in the west of Iran showed that during the heat wave occurrences، warm and dry air from deserts of Saudi Arabia and northern Iraq has been drawn to the western half of Iran through low pressure air masses located over these two countries، and consequently، this influence is more sensible in the western and southern stations like Khorramabad and Kermanshah than other stations، such as Hamedan، Sanandaj and Saghez. In most of the studied hot waves، Azores subtropical high pressure extends as a belt from North Africa to Iran. 1000-500 hPa thickness maps showed that a warm air core is extended from Iraq to Egypt with southwest-northeast direction، and covers western half of the country. All in all، two synoptic patterns، one related to the strongest waves and the other near-normal waves were extracted. In the first pattern (near-normal waves) Azores subtropical high pressure creates a secondary high pressure over Saudi Arabia، and the deep trough which has been created in the West Urals، weakens the Saudi Arabian High. Thus subtropical systems move to more southern latitudes and consequently have less impact on the western half of the Iran. In the second pattern (strongest waves)، Azores subtropical high pressure advances and expands over northern latitudes، up to about 35°N. In this pattern Azores high pressure belt covers the area from North Africa to Iran، and this way the stronger heat waves affect western half of Iran. Warm air advection maps too verify this status. So that the warm air advection amounts at 200-hPa over the Middle East are positive، which indicates the greater thickness of atmosphere compared to the usual state. As expected، from synoptic point of view، the occurrence of heat waves in the region has been simultaneous with thermal low pressure formation at the ground level and subtropical high pressure at the upper levels. The number of superhot days in the stations has increased on average at the rate of 2. 06 days in the study period، which can be indicative of warming trend in the region. This warming trend is consistent with results of studies in Greece (Maheras et al، 2006:161)، United States of America (Bumbaco et al، 2013:1618)، Europe (Twardosz and Kossowska، 2013:627)، and Iran (Esmailnejad، 2014:39; Darand، 2014:167). Comparing the results of this study with other studies in the future will reveal the similarities or differences of statistical characteristics and synoptic patterns of heat waves in different parts of the country.

Kermanshah station as station coordinates 34 degrees 21 minutes north latitude and 47 degrees9 minutes east longitude has been extreme temperature fluctuations and predict for the analysis of Kermanshah and their relationship with the NAO is considered to carry out this study، data relating to the maximum annual absolute maximum temperature.. رnowadays one of the most important discussions in the scientific circle is the discussion about climatic changes’ increase in the average temperature of the globe and its consequence that more or less has been paid attention to in our country as well. In this research the attempt was to pay attention to the survey of increase data in the maximum temperature of Kermanshah. Farin make the temperature effect on natural and human ecosystems And directly associated with the human condition and comfort climate And their role in natural processes and human activities is undeniable The temperature in the precipitation of the most important climatic factors considered in determining the distribution of roles and other elements that affect climate. Thus the annual absolute maximums of date in the specific station during a 50- year period (1961-2010) have been used. The correlation method (logarithmic’ poly nominal) and Mann- Kendall statistical test have been used for testing the meaningfulness of fluctuation direction of series temperature and its diagram has been drawn by using the MATLAB software. The results show that the temperatures of two decades of 1970 and 1980 have been lower and three decades of 1990 and 2000 have been higher than the long- term average and the decade of 1980 has been the coldest of the decades. The general result of this research shows that there are seasonal fluctuations in maximum temperature of Kermanshah which are not meaningful. The model of halt winter has been recognized as the best model for predicating the temperature of maximum extreme of Kermanshah which the diagram in a Minitab was drawn and the results of this predication shows that there is an abnormal increase in the temperature of 2014 and 2019. the temperature of the elements which are directly related to climatic conditions and welfare of human life and its role in human activities and natural processes is undeniable. The precipitation temperature is considered the most important elements in determining the role of climate and climate affect the distribution of other elements (Alijani and Ghavidel Rahimi، 1384). The sharp changes in temperature adversely impacts to biological lifeforms. Among the adverse effects of temperature changes is (hot and cold wave) loss of organisms in the ecological conditions of low and high temperature range. Similarly the effects of this phenomenon on the climate construction of facilities and buildings is very high and the occurrence of such phenomena losses will be very large. Increase in energy consumption during the occurrence of this phenomenon is including their adverse effects. Nowadays، climate change science and its application to a large extent، is considerable importance And understand the causes and nature of these changes، the most important objectives is data collection weather and climate monitoring and climate phenomena (khorshiddost and colleague، 1388 and 1389). Increase in average global temperature profile and changes of climate change is The whole idea to consider climate change. the situation of Kermanshah is 34 degrees 21 minutes north latitude and 47 degrees 9 minutes east longitude minutes. The results show that the distribution of the probability of recurrence given extreme maximum temperature wasnot normal in the Kermanshah Instead of the normal logs will follow. In fact، the show is log normal Linear methods have limitations due to non linear part (Plynvmyal) can be used Due to the extreme temperatures of maximum long-term average and the results were compared with the temperature during the 5 1960، 1990 and 2000، higher And the 1970 and 1980 to be below average are 50 years. In this regard، the coldest 1980s and 2000s warmest decade of Kermanshah. Comparison of long-term period of 2010 - 1961 and 2010 - 1990 show The increase in 0/42 ° C maximum temperature during the last 21 years. None of the studied extreme temperature changes in the peak intensity changes of Kermanshah not linear and parabolic regression will follow decade long trend in the 1980s and 1990s when the trend is much stronger than the other. The general trend of the maximum temperature change is gradual upward climb However، the extreme maximum temperature Kermanshah gradual changes when using the six degrees Plynvmyal shown In mid-2000 Series (2005) show a sharp decline. Extreme maximum temperatures in the normal range located in Kermanshah more years Only in 1964، 1969، 1973، 1981، 1994 and 1997 is strongly positive anomalies in the range Using the Mann - Kendall found The maximum extreme temperature changes when Kermanshah despite showing no significant trend of increasing The maximum extreme temperature changes، although the changes in long-term averages will show. But the extreme maximum temperature changes in the Kermanshah is no mean Meanwhile، the 21-year Kermanshah station from 1990 to 2010 despite a linear increase of about 3%، no significant changes during the 21 years. The results of the model Holt - Winters it was obtained during 2011، 2012، 2014 and 2019 is higher than the upper threshold،. Years 2013، 2015، 2016،، 2017 and 2020 the normal threshold and only2018 was lower than normal threshold The years 2014 and 2019، with temperatures 3/44 ° C warmest years Between the actual temperature and the pre projected to be Kermanshah. Measures the accuracy of the model prediction Holt - Winters and the normal distribution and histogram frequency data showed and The validity of the method was applied to predict the acceptable level And quantities been projected with the distance High reliability Printable the occurrence Using Pearson correlation coefficients associated with the NAO index and the heat wave was determined. The highest correlation between the North Atlantic Oscillation and the cold seasons and temperatures ranged from one month to find a negative، While the correlation coefficient for the three-month lag in the warm seasons and the relationship is positive.

The Siberian high (SH) is a quasi-stationary and semi-permanent surface high pressure system residing over the Eurasian continent during winter with its climatological–mean central pressure exceeding 1030 hPa. This most important atmospheric center of action controls the climate of a wide area of this continent. The SH forms generally in October mainly in response to strong radiative cooling over the snow covered Eurasian continent in the lower troposphere and persists until around the end of April in 90-110 °E and 40-55° N (Shahgedanova; 2002، 70.، Takaya and Nakamura; 2005، 4423.، Gong and Ho; 2002، 2،. Shahgedanova، 2002). The Asia climate is mainly affected by the SHI activity at winter. Despite the prominence and large spatial extent of SH in northern hemisphere، its spatial and temporal variations are not comprehensively known (Panagiotopoulos et al.، 2005، 2005، p. 1411). The global warming has been intensified in middle of 1970s and significant changes of mean sea level pressure (MSLP) in northern hemisphere and changes of atmospheric circulation on many regions (Trenberth and Hurrell; 1994، 303.، Nakamura et al; 1997، 2215.، Wang et al; 2007، 12) have been reported. A variation in temperature results in sea level pressure decrease according to barometric relation. In other words، the SH is expected to be weakened by the global warming as has been occurred after the 1976/1977 (Panagiotopoulos et al.; 2005، 1411). The obtained findings by Hori and Ueda (2006، 4) and Romanić et al (2014)، verify the same relation between global warming and SH weakening. Panagiotopoulos et al. (2005، 1411) have shown that the SH has experienced a negative trend of -2. 5 hPa in each decade during 1978-2001 while a slighter rate has been reported during the later decades (Jeong et al; 2011، 8). A plenty of studies have considered the temporal variability of SHI while the spatial variability and also the simultaneous spatial and temporal variability of SHI during global warming period have been often neglected. Thus، the present research aims to study the spatial and temporal variation of SHI during global warming period. Matarials and

2. 1. Data The present research has used the sea level pressure (SLP) data (Kalnay et al.، 1996) are obtained from the NCEP/NCAR Reanalysis 1 (NOAA National Center for Environmental Prediction). These data are gridded at 2. 5º latitude by 2. 5º longitude meshes، and cover 65 years (1948-2013). The SHI index is defined as the maximum pressure in SH spatial domain and the spatial and temporal variations have been considered during the global warming through the analysis of this index. The annual global land temperature anomalies data was also extracted from national climatic data center to consider the intensified global warming. Having collected the needed data and using regression method، the studied period (1948-2013) was divided into two parts presenting two discrete periods having different global warming intensities. Two mentioned periods were named intensified and slight global warming. The significance of spatial and temporal variability of SHI during two mentioned global warming periods were discussed through the compare means tests. 2. 2. Siberian High IntensityIn this research، the SHI is defined as maximum of December to February mean SLP over northern Mongolia between 40 and 65°N and 80–120°E. The same or similar definitions of the SHI have been utilized in many previous studies. 2. 3. Slight and intensified global warmingThe time series of data during 1880-2013 were used to consider the annual global land temperature anomalies data using regression method. The obtained results indicated that the pattern of mentioned data during 133 years can be divided into three smaller periods. Three periods of 1880-1933، 1934-1973، and 1974-2013 have the negative، near zero، and greater upper zero anomalies، respectively. The recent period (1974-2013)، having higher slope and increasing rate، was considered as intensified global warming while the 1934-1973 was considered as the slight global warming period having the slope near zero. Result and discussion3. 1. Temporal variabilityThe SHI were obtained during DJF through gridded. The weakening of SHI and its intensification recovery are evident during 1970-1980 and recent decades، respectively. The SHI decreased during intensified global warming (1974-2013) compared to slight global warming (1948-1973). The remarkable point is the noticeable reduction of variance during intensified global warming indicating a great change in annual SHI during intensified global warming. Regarding the maximum and minimum of SHI during two studied periods، it can be concluded that the variance decrease is due to decreasing maximum، meaning that the SHI variation range is decreased because of a decrease in SHI maximum3. 2. Spatial variabilityThe SHI centers location during intensified global warming shows that the centers have been focused toward zone 1 and 94. 17% of them are in zone 1 while only 5 and less than 1% of them are located in zone 2 and other zones respectively. The longitude and altitude time series of SHI also show a decrease of SHI centers distribution that more SHI centers have been formed in 50°N and 90°E since 1974. After the specification of SHI centers displacement، it is expected that their range is changed. Thus، two 1020/5 (reported as SH boundary in many references، for example IPCC; 2013، 224) and 1034 (more than 95% of SHI centers have a pressure higher than 1034 hPa and contour has been noticed as a area in which most SHI centers are formed) contours were plotted during two studied periods. Having extracted the mentioned contours during DJF at 1948-2013، the average of each contour was calculated and plotted during two global warming periods.

Starting the average sea level pressure changes in northern hemisphere from 1970 a noticeable change was observed in spatial and temporal of SHI resulting a dramatic change in average Earth''s temperature. The SHI has been weakened as the intensified global warming started (1974-2013) and the annual variation range has shown a considerable decrease compared to the period before (1948-1973). This annual variation decrease is due to a decrease in maximum and an increase in a minimum of SHI. It''s noteworthy that the decrease in maximum SHI has had a more dominant effect. The spatial SHI variations during intensified global warming (which is significant in error level lower than 0. 01) has been resulted in a reduction in spatial distribution of SHI centers in such a way that the SHI centers have been shifted toward 50°N and 90°E as the average global temperature increases. Additionally، the isobar 1020. 5 hPa (as maximum SH distribution) and 1034 hPa (as an area in which most SHI centers are formed) have been shifted toward west. A remarkable area decrease has been observed in 1034 hPa isobar during intensified global warming which is justified regarding the reduction of maximum SHI. Regarding the point that a significant change of atmospheric circulation has been occurred at mid-1970 in many areas of the world، it seems that the spatial variability of SHI have been due to noticeable changes in atmospheric circulation in such a way that the Aleutian low shifting toward west during 1977-1988 winters and variabilities of ocean temperatures during last 1970s have resulted in a long-term NAM/NAO and have led to SHI shifting consequently. Meanwhile، the important issue is that all of the mentioned changes have been coincident with a noticeable change in land temperature. Thus، it can be concluded that the global temperature increase have resulted in changes in atmospheric circulation and reorganizing the climate system. A scrutinized understanding of details، physical mechanisms، and real dynamics resulted in such changes necessitates a more comprehensive study and more data.

Jet stream is strong narrow current concentrated by strong vertical and lateral wind shears (Vasantha et al، 2002). According to World Meteorological Organization nomenclature، jet stream formed when the speed of wind greater than 60 knots or 30 m/s. The major characteristics of the troposphere and lower stratosphere in the vicinity of jet streams were pointed out by a group of meteorologist at the University of Chicago (Rossby et al،1974; Rossby، 1974). These characteristics are the tropopause discontinuities، the intense horizontal temperature gradients considerably below the jet stream core، and the associated frontal systems (Endlich،1953). Jet streams possess a considerable amount of kinetic energy with velocities comparable to horizontal phase velocities of atmospheric waves (Vasantha et al.، 2002). Study Area: The study area is the Kurdistan Province in the west of Iran. The land area of the Province is approximately 29،600 km2. The topographical elevation varies between 712 m in the southwest and northwest and 3219 m in western and central parts of the study area. The differences in elevation and mountains configuration resulted in differences in precipitation reception. The long-term mean annual precipitation of the study area varies between 300 mm in the east and over 900 mm in the west with decreasing trend from west to east. The aim of this study is the analysis of jet streams frequency occurrence during heavy precipitation over Kurdistan province during 1/1/1961 to 31/12/2010 (18263days). To doing this study daily precipitation data of 8 synoptic stations have been extracted from Iranian meteorological organization. The frame of 10° to 100° eastern longitude and 0° to 70° northern latitude has been selected to recognition of jet streams frequency occurrence. Figure1. The spatial distribution of synoptic stations (black dots) and elevation (color background) over Kurdistan ProvinceData and In this study، environment to circulation approach has been selected. By using two thresholds of extensively and intensity of precipitation occurrence، 107 days had been recognized. In temporal view، the selected days occurrence in wet seasons of year، start from October to the June. The u and v wind components data on the 2. 5×2. 5 pixels in 10° to 100° eastern longitude and from 0° to 70° northern latitude frame from National Oceanic and Atmospheric Administration has been extracted. One matrix with dimension 107×1073 created that days located on the rows and pixels on the columns. The heavy precipitation in Kurdistan province not only observed in the wet season but also occur in the arid season. These kind of the precipitation occurred in the arid season with lower intensity and frequency. In order to recognize heavy precipitation، the area mean precipitation for the province had been calculated. According to the 99 percentile threshold and extensively of precipitation the heavy precipitation recognized. By two thresholds 32 days selected and same as to the wet season precipitation، u and v wind components data from NOAA extracted. Figure2. The selected frame in order to analysis of jet stream frequency The results of this study showed that in the wet season، during the occurrence of heavy precipitation، the jet streams descend to the 700 hPa level (about 3 km above earth). The highest frequency of jet streams are located on the north and northeastern parts of Arabian. The highest frequency and speed of jet streams observed in the 18 UTC. The Kurdistan province located on the left output part of jet streams where atmospheric divergence and instability occurred in the whole of observations. The output axis of jet stream is toward to semi western parts of Iran. The heavy precipitation during arid season is accompany with jet streams in the upper levels. The formation location of the maximum frequency core of jet stream is same as jet streams in wet season but the frequency of jet streams is lower and don’t observed in the levels below 500 hPa.. According to the results of this study we can say that jet streams have important role in amplification and intensification of air instabilities and prone to occurrence of the heavy precipitation in Kurdistan province. This circumstances are present during heavy precipitations both in the wet season and arid season. Jet streams frequency occurrence in the wet season are more frequent and their speed are faster. Also in comparison to the arid season، jet streams are shown in the low levels.

Thunderstorms of the most important، most abundant of the most severe weather hazard that each year، in addition to large quantities of crops and infrastructure development، causing human casualties are also around the globe. Between 1953 and 1957 the financial losses caused by the hurricanes in America has over 3. 6 million dollars (Changnon; 2003،1231). Storms of varying intensities have been identified. The average horizontal range of a few tens of kilometers of the storm، the vertical range of about 10/000 m and has a lifetime of 30 minutes (Henderson، 2006). These storms often clouds Rick، Rick rain and are shaped tower along. Thunder usually high or heated air masses in the ground or in the air fronts، especially in the cold front، caused، so the Thunder or the origin of air masses or the front. Thunderstorm climate risk as part of the nature of Iran''s North West Province، socio-economic and environmental damages each year to the people، especially farmers and ranchers are (Khoshhaldastjerdi، J. GhavidelRahimi، Yousef; 2007،101). (Sari Sarraf et al.; 2007،123) of rainfall in the southern basin of Aras River barrage to approach and came to the conclusion that the main causes of showers barrage in the area are two regional instability (in summer) and in front cold (in winter) is. Meteorologists to study the atmosphere of the period of the formation of storms، the following factors have the appropriate factors or lack of conditions for hurricane formation and climate instability or the possibility of convection as well as show. High levels of cold weather hot weather، low levels and the abundance of moisture، all of unstable atmosphere. Accordingly، since the dynamic atmosphere of instability factors، the most important scientific method to the study of atmospheric instabilities is a storm. The study area: Hamedan province with an area of approximately 19545/82 kilometers، the circuit (33 degrees 33 minutes) to (35 degrees and 38 minutes) north latitude and between the meridians (47 degrees and 45 minutes) to (49 degrees and 36 minutes.) is located east longitude. Hamedan province to the north is limited province zanjan and ghazvin،and to the south is limited province lorestan،and to the east is limited province markazi،to the West is limited provinces Kermanshah and Kurdistan. According to the latest administrative divisions، including 8 of the city، 21 cities، 20 districts، 71 rural districts and 1120 villages. The average height of about 1،800 meters of surface water. Alvand peak with an altitude of 3584 meters the highest point of Hamedan province and the lowest point is 1،600 meters with a height of land amrabad. These stations are given in Table View. Name of station longitude latitude altitudeHamadan Airport 48. 32 34. 52 1741. 5Nojeh Kaboudarahang 48. 71 35. 20 1679. 71Author: 09183177169 E-mail: fa. iranpour@gmail. com

To determine the incidence of storms synoptic data from two stations Nojeh Hamadan airport and the period of 15 years (1992،2006) were used. In this study، the initial data from the Meteorological Research Center of Hamadan in the period 1992 to 2006 was obtained، After controlling the data، initial tests have been done and data on the present and past weather the storm of the code were specified time scale. Were determined by surveys conducted during the period of 15 years، 270 thunderstorms occurred in the region. Continue to identify synoptic patterns cause storms in the region، a cluster analysis was performed on 270 days with thunderstorms and storms occurred in this province were clustered. And hours were significant in terms of duration and intensity of storms and showers barrage studied were synoptic، To analyze the thunderstorm occurred during the period، first by synoptic weather map at 500 hPa surface is determined daily and thermodynamic methods، To draw them، raw data and the level of 500 hPa surface of obtaining environmental predictions Center and then by using the Grads were plotted on a map. Thermodynamics diagrams also known as April 10، 2005 and October 31، 2006، due to the occurrence of severe thunderstorms in these days، for example، the website of the University of Wyoming to study، and have been used. Thermodynamic charts (upper) and mean monthly، seasonal and yearly for both stations was calculated، Atmospheric instability to volatility indices were studied. These indicators reflect the high probability of instability and، in particular، storms in the days mentioned.

Analysis of circulation patterns storm and showery precipitation In order to identify patterns cause storms Showers and identify the days of the index، a cluster analysis on 270 days with thunderstorms in the area. And these days were divided into six clusters. Then in each cluster on a day which was more unstable، was elected as a representative day. Synoptic pattern of the day، for example، were studied. Study maps of the surface and 500 hPa long-term patterns show that during storms Showers several successive systems of the North West and from Iraq into Iran، causing storms and rain showers in the area is. At ground level from the South West of Iran and the Arabian Peninsula، low pressure Sudan to Iran. ISO time to draw maps and contour maps of the Earth''s surface and the level of 500 hPa،The raw data of the Earth''s surface and the level of 500 hPa، the environmental prediction America Center was received، And then by using the Grads were plotted on a map. Assessment of changes in storm studied stations Change the hours of thunderstorms in the airport station is shown in Fig. Most storm at the station between the hours of 15 and 18 respectively and 12 and 21 synoptic hours after they have had the greatest storm. Monthly changes in Days of Thunder in the airport station is such that the most frequent occurrence in April and May and the lowest frequency of its occurrence is in December In between seasons، spring is the most frequently Days of Thunder. And winter، the lowest frequency is allocated. Over half of storms reported in the spring، then fall، most of it is dedicated to، as well as the annual changes in the region studied storm، nearly has a growing trend، in 1993، the lowest of the In the entire region، and 2004 as the most prominent in terms of frequency of occurrence of this phenomenon has been reported. Nojeh station thunderstorms are most frequent occurrence is between 15 and 18 hours. Synoptic hours، followed by 12 and 21 accounted for most of it. During the months of the year، the April moon and may have the highest frequency and December and February have the lowest frequency of thunderstorms. In the between seasons، spring represents the highest frequency. Over half of storms have been reported in the spring، then fall، most of it is allocated، as well as the annual changes in the region studied storm، nearly has a growing trend، in 1993، the lowest of the In the entire region، and 2004 as the most prominent in terms of frequency of occurrence of this phenomenon has been reported.

Analysis and output maps and weather patterns show that the most important indicators of large-scale storms could be severe pressure gradient at the surface، atmosphere and clouds pile a dry layer of more or less similar pluvial instabilies atmospheric noted. Therefore، large-scale patterns useful in detecting not only the exact occurrence of these phenomena can be qualitatively predict the weather. However، volatility indices such as Ki، Si، Sweat and numerical thresholds for these indicators help predict storms in the area. Maximum storm event Nojeh station 534 times and Airport Station 312 time (over 15 years) experienced the lowest incidence of hurricanes. Most of these storms nature front and Synoptic and because the systems climax to the region، because the airport station number of event storms، 81 percent of the station Nojeh 71 percent of the synoptic and the front of the storm، stations، airports، 19 percent of stations Nojeh 29 percent of the local thermodynamic nature. Most storms at both stations during spring and in the afternoon and early evening of April happened، this phenomenon occurs when the active area of low pressure over southern and south with hot، humid currents، their the higher latitudes can be seen in the spring and take a combination of these conditions in parts of West، North West of active centers and the high-pressure cold latitudes of both the lower moves of different weather، significant influence on the northern regions of atmospheric fronts، West and South West of the country has been producing cumulus clouds and cumulonimbus. Which is usually accompanied by torrential rainfall has been observed on these areas. At the time of the storms at the level of 500 hPa، a deeply unstable trough is formed on the Black Sea.

Long-term annual extreme climate events، especially temperature and precipitation، have generally been used as indicators for the assessment of climate change. One of the most changeable climatic variables in time and space is precipitation. There are great number of research papers focusing on extreme precipitation on global، regional and national scales have been written. The results of these studies of precipitation and extremes indicate that there are changes in intensity، amount، duration، timing، rate of precipitation and change on trend of extreme precipitation events (IPCC، 2007) and these precipitation irregularities and extremes are impact of climate change. Change on trend of extreme precipitation events have been caused change on severity، permanence، temporal distribution and rate of precipitation in many regions and can be cause drought and floods or other hazards. Generally، Study of extreme precipitations and their frequency is very important in order to understand why they happen and if there are some signs or particular periodicities. Moreover this kind of researches are fundamental in order، first of all، to save human beings، but also to avert or to limit damages done by these extreme events (Boccolari and Malmusi، 2013). Studies of variability in precipitation can be classified into two categories: long-term changes (trends) and short term (oscillation) (Asakereh & Razmi، 2012). Many studies show that there are a change on trend of extreme precipitation events in Iran، but since the change in this events are associated with indexes and factors that influencing the precipitation of Iran، so this study focus to reveal the extreme precipitation variability in the West and North West of Iran and the relationship of theirs with the effective index of precipitation in Iran. Study Area: Iran is located in the west of Asia، and in the arid and semi-arid belts. The study province is West and Northwester of Iran، that’s includes six state of Kermanshah، Kurdistan، Hamadan، Zanjan، East and West Azerbaijan (from 44. 03 to 52. 49 E and 33. 37 to 39. 46 N). These areas are located near the Iranian border with Iraq، Turkey، Armenia and Azerbaijan in western and Northwestern Iran.

The aim of this study is analysis of variability of extreme precipitation events on West and North West of Iran and theirs relationship with teleconnection patterns include ENSO، MEI، NAO and AO and also pressure centers includes Mediterranean center (MLP)، Sudan low (SLP)، Siberian high pressure (SHP) and Black Sea low pressure (BSLP) center and finally with Sunspots. The extreme precipitation indices that we used are Maximum 1-day precipitation (Rx1day)، Maximum consecutive 5-day precipitation (Rx5day)، Simple precipitation intensity index (SDII)، Number of days with precipitation equal to or greater than 10 and 20 (R10mm abd R20mm)، Maximum number of consecutive dry and wet days (CDD and CWD)، Total precipitation when daily amounts are greater than 95th and 99th percentile of wet days (R95 p and R99 p)، and Total precipitation in wet days (PRCPTOT). Our used data were limited to daily precipitation data from only 8 of Iranian synoptic stations، includes Tabriz، Oroomieh، Khoy، Saghez، Sanandaj، Hamedan، Kermanshah and Zanjan، that have reliable data and covering period 1961-2010. For time series studies and trend analysis in climatological variables، various statistical methods have been used. In this study the non-parametric Mann–Kendall test، which is frequently used to evaluate statistically significant trends in climatological variables time series was used. Studies exploring short-term oscillations in precipitation are based on a different group of methods، including autocorrelation functions، harmonics analysis، spectral analysis and wavelet analysis. One of the most common methods used in climate studies is spectral، which was employed in this study. The short term oscillation of macro scale factors influencing variability in precipitation for the middle Zagros includes El-Nino Southern Oscillation (ENSO)، Multivariate ENSO Index (MEI)، North Atlantic Oscillation (NAO) and Arctic oscillation (AO)، pressure variability from the MLP، SLP، SHP and BSLP pressure center، and potentially sunspots، in relationship with extreme precipitation in the north west of Iran have been analyzed.

About the main factors that affecting the precipitation of West and North West of Iran، Negative phases of the ENSO index has increased and this factor can reduce of winter precipitation in study area. In AO and NAO، trend in positive phases is increased and by this condition can be caused reduce in annual precipitation. Z-statistic in pressure centers indicates in a way the pressure of those centers over the past 50 years has increased. Change in pressure of these centers probably can affect the pattern of precipitation in the study area and cause change of precipitation rate in study area. The Z statistic of the 10 extreme precipitation indices shows the trends in all the extreme precipitation indices in more stations have been decreased. Rx1day in Tabriz، Khoy، Kermanshah and Znjan were negative trend and in others are positive. By using spectral analyses technique on Rx1day، significant oscillations 2-3 and 3-5 years have been discovered. This oscillation is related to ENSO، MEI، AO and NAO and also is related to MLP، SLP، SHP and BSLP oscillation. Rx5day only in Hamedan and Sanandaj are positive and the significant oscillations 2-3 is related to ENSO، MEI، AO and NAO، MLP، SLP and BSLP oscillation. SDII trend in Oroomieh، Kermanshah and Zanjan were negative. The 2-3 years oscillation in Hamedan is related to Sudan low oscillation and 3-5 years in oroomieh is related to ENSO. R10mm in all stations، except in Sanandaj، were negative trend and the 2-3 years oscillation in this index in Hamedan is related to NAO and the 3-5 years oscillation in Kermanshah and Zanjan is related to MLP and also in oroomieh is related to ENSO. As R10mm index، except in Sanandaj، the R20mm and CWD indices the trends in all stations were decreased. R20mm in Kermanshah and oroomieh stations 2-3 years oscillation consequently is related to MLP and ENSO. The CDD trend in Hamedan، Zanjan and Sanandaj were negative and in others station were positive. The 2-3 years oscillation in Zanjan and Hamedan is related to NAO، ENSO or MEI oscillation. The 12 years oscillation of this index in Khoy and Oroomieh is related to 12 years oscillation in Sunspots. The R95p trend in Sanandaj and Saghez were positive and in the others were negative. This trend indicates indicate that number of heavy rainfall in more stations have been decreased. Finally the PRCPTOT in all station، except in Sanandaj، were negative that’s show the trend of precipitation in study area have been decreased. The 2-3 years oscillation in this index in Oroomieh، Hamedan، Kermanshah and Khoy consequently are related to ENSO، NAO and MLP and also in Zanjan is related to ENSO and MLP and in Tabriz is related to NAO، AO، ENSO، MLP and BSLP.

Typically the trend of precipitation in the study area was negative that’s show trend of precipitation has been decreased. Only the precipitation trend in Sanandaj station was positive. The trend of teleconnection patterns in a way that justifies the decrease in precipitation and also this condition applies to pressure centers. Spectral analyses showed significant oscillations in 2-3، 3-5، 5-8 and 12 years. Major area experienced 2-2 and 3-5 years oscillations. These oscillations periods are due to macro-scales circulations; mainly include the oscillation in ENSO، NAO and AO and also Mediterranean Low Pressure.