نشریه پژوهش های اقلیم شناسی
پیاپی 7-8 (پاییز و زمستان 1390)

IntroductionThe largest growth in GHG emissions has come from energy supply, transport and industry, while residential and commercial buildings, forestry (including deforestation) and agriculture sectors have been growing at a lower rate (IPCC,2007). Aviation’s contribution to climate change is now a topic of considerable interest. Aviation is a comparatively small contributor – a few per cent – to Greenhouse Gas (GHG) emissions, but its growth is rapid (Broker, 2008). Emissions of carbon dioxide by aircraft is about 2% of total anthropogenic carbon dioxide emissions in 1992 or about 13% of carbon dioxide emissions from all transportation sources (IPCC, 2007). Therefore, it seems that fuel management in aviation has important role to CO2 emission. This paper focuses on the estimation of consumed amounts of fuel and CO2 emitted to the atmosphere in a case with incorrect fuel management.Material and MethodsAll information about the number of flights to Abadan and Ahwaz airports, including QRF and Diverted flights are received from Tehran Area Control Center (ACC). Meteorological data are provided by Iran meteorological organization (IRIMO) including the number of dusty days and is compared with long time (20 years) average number. Distance of a specified flight rout from departure aerodrome to the over head of the destination aerodrome, is measured according to Tehran FIR map which is the flight distance in going route. Then, the distance is doubled for QRF flights to include return to departure airport. In divert flights, the distance of a specified flight rout from destination overhead to alternate airport is marked and measured using Tehran FIR map. All flights to Ahwaz and Abadan destinations considered in this paper are T154 and F100 aircrafts with speeds of about 840km/h (420knot). Their air speed can cover a distance of 14 km (7 nm) per minute. So, flight timing in cruising phase can be easily computed using flight speed and distance. On the other hand, times for take-off and landing should be determined to compute the real total flight timing. With an optimistic view, 8 minutes are considered for takeoff and landing time in each flight. The amount of consumed fuel is 33 liter/ minute for a 2 engined F100. It is clear that this amount should be more for T154 with 3 engines and is about 83 liter/minute.. The consumed fuel after starting up for taxi and take off and also after landing and taxi to apron is not considered.Several studies have been done to calculate CO2 emissions considering consumed fuel, load factor, aircraft speed and so on. One way to calculate CO2 emissions is using fuel consumption per flight. The CO2 emissions takes values of about 250 kg (i.e. 1/4 tone) per hour of flying. In order to have a comparison between atmospheric conditions effective on flights in summer of 2009 compared to similar atmospheric conditions in earlier past years and the number of all days with low visibility due to dust is compared with long term (20 years) average number. The same comparison has been done for the number of days with visibility less than minimum visibility required for Ahwaz and Abadan airports, considering aircraft type.Discussion and resultsDuring June and July 2009, 22 flights had been QRF (Quick Return Flight) or diverted due to poor visibility in Abadan and Ahwaz airports. In this matter, not only financial losses are inflicted relevant airlines due to futile consumed fuel, but also lots of CO2 were pushed into the atmosphere which is considered a pollution threat to the environmental.Minimum visibility required for landing in the Ahvaz airport is 1200 meters. This parameter is 2400 and 2700 meters for T154 and F100 respectively in the Abadan airport.A climatology survey shows that the dusty days number are more than 20 and 25 respectively in June and July 2009 in the Khuzestan province(including Ahwaz and Abadan airports). Focusing on the days with minimum visibility in Ahwaz and Abadan airports during June and July 2009, relevant maps shows strong deviations from long term mean values. Indeed, dusty days are 8, 12 and 15 days more than mean long term (20 years) in June and July 2009 with visibility less than 1200, 2400 and 2700 meters respectively. The calculated values show that 134,500 liters of aircraft fuel has been consumed futile where its financial value cant be omitted. Besides that property loss, the amount of emitted CO2 into the atmosphere is about 8,000 kg reminding that the time for landing and takeoff is considered 8 minutes which is very optimistic. Although the amount of consumed fuel and emitted CO2 is not comparable with global scales but it is noticeable that the energy, time and money were used pointlessly and with a suitable management it could be prevented.ConclusionsThis paper is dealing with transportation and environment related subjects from two viewpoints. First, resources of energy can be conducted in a correct manner under a skillful management system. In this regards, financial savings can be satisfactory revenues. Second, adaptation to climate change is acquired which is an available solution to deal with natural events that are not in human control. Results of this study, shows that with more conscious consideration of issued meteorological warnings for in order to cancel flights or change the time of departure (based on meteorological warnings, financial loss can almost be prevented. In addition, emission of CO2 and as a result, environmental pollutions is controlled.Climate change is an obvious and unavoidable phenomena and its occurrence is approximately uncontrollable. Adaptation to climate change is a solution to reduce losses. If flight time is transferred from early morning to midday, the landing would take place because of improved visibility due to the surface heating. On the other hand, if the low visibility conditions (dusty days) continue in future years, it is necessary to equip the airports with those instruments which have more capabilities for aircraft landing in low visibility conditions. In this case, there wouldn’t be any QRF, divert or even cancelled flight due to poor visibility. Of course, it needs more study and is not considered in this paper.

IntroductionAtmospheric conditions are one of the most important and effective variables in agricultural crops production. Being aware of atmospheric conditions and agroclimatic potentialities of different areas, we can make use of resources efficiently and develop the regions. One way for agricultural development is to use lands corresponding with ecological and environmental conditions. Papadakis classification method emphasizes on the agricultural potentialities, crops climatic requirements, and geographic distribution of climates in different regions. Knowledge on the agroclimatic potentialities is very important in optimal crop cultivation, design and management of agricultural system. In this research, Papadakis method is used to investigate the agroclimatic potentialities in three selected stations. Materials and methodsIn this paper, meteorological data of three selected stations in Ilam province has been processed and analyzed through papadakis method. Indices Used in this research are: winter severity, summer heat, nonfrost season length, potential evapotranspiration, water balance and seasonal distribution. Crops’ categories, based on the winter severity and the crops’ sensitivity to cold, are: equatorial, tropical, citrus, avena, triticum and primavera (spring crops). Crops’ categories, based on the summer type and the crops’ heat requirement, are: gossypium (cotton), coffe, oryza (rice), maize, triticum (wheat), polar (tundra), polar (taiga), frigid, andine-alpine. At first, winter type determined by average of the lowest of the coldest month, coldest month average daily minimum and coldest month average daily maximum. Then summer type determined by length of frost free season, average of daily minimum and maximum of the warmest month. Temperature regime defined based on summer and winter types. The next step humidity regime determine with use of such indexes include: annual humidity, potential evapotranspiration, rainfall, leaching.Results and discussionThis research shows that from the viewpoint of winter temperature conditions the above-mentioned stations have more diversity, as synoptic station of Ilam and Ivan are in avena category and Dehloran station is in Citrus category. From the viewpoint of summer temperature conditions, all of the stations of the region are in cotton category (warm and dry condition). Generally, above stations from the viewpoint of thermal regime are in subtropical and continental group and from the viewpoint of moisture regime are in Mediterranean and desert–Mediterranean group. All studied stations go under two climatic groups: Continental Mediterranean (north region) and hot subtropical desert (south region). ConclusionsThis paper shows that in high and moderate lands (in Ilam and Ivan stations), there are agroclimatic potentialities for winter grains crops specially (wheat and barley). Winter climatic conditions are appropriate for olive and cotton cultivation based on summer climatic conditions. Dehloran station that is indicator of tropical areas of the province has suitable climatic potentialities for cultivation of agricultural crops such as citrus considering winter severity degree and cotton considering summer heat conditions. The researcher concludes that in low lands of the province (Dehloran station) there are potentialities for cane and rice cultivation if enough water exists.

Drought has significantly affected the environmental and socio-economic conditions in Iran. Three drought indices were used for monitoring drought intensity and duration in Kashafrood basin (northeast of Iran). The standardized precipitation Index (SPI), Precipitation Index Percent of Normal (PNPI) and Agricultural Rainfall Index (ARI) were calculated for the base period (1961-1990). All these indices were used to assess future drought in Kashafrood basin under climate change attributed to low and high greenhouse gas emission scenarios (SRES B2 and A2, respectively) for 3 periods (2010-2039, 2040-2069 and 2070-2100). Projected changes in precipitation, temperature and potential evaporation were simulated by statistical downscaling of HadCM3 outputs. Main results showed: (i) slight increase in precipitation means, around 2.2% to 5.4% under A2 scenario and 6.8% and 8.6% under B2 scenario. (ii) Slight increase in maximum temperature, around 4.6 oC to 5.6 oC for A2 scenario and 4.25 oC and 4.6 oC under B2 scenario. (iii) Slight increase in minimum temperature, around 1.6oC to 1.9 oC under A2 scenario and 1oC and 2.23oC under B2 scenario. (iv) Higher drought frequency associated with global warming was demonstrated by all indices for both scenarios. Such an increase in drought frequency would have major implications for natural resources management, water security planning, water demand management strategies, and drought relief payments.IntroductionDrought is a prolonged, abnormally dry period of shortage of water for normal needs. Generally, this occurs when a region receives consistently below average precipitation (Oliver, 2005). Drought is predominantly controlled by air temperature and precipitation (Loukas et al. 2008). The recent GCM-based projections suggest significant changes in temperature and precipitation. Changing of these climate variables under global warming will cause changes in severity and frequency of drought (Li et al., 2009; Kebat et al., 2002). The severity of drought is quantified as drought index. A drought index defines comprehensive information on drought conditions for decision making at water resources and agricultural sector (Hisdal and Tallaksen, 2005). Loukas et al. (2008) evaluated climate change affects drought severity using SPI at multiple time scales such as 1, 3, 6, 9 and 12 months in the region of Thessaly, Greece. They used outputs of CGCM model under two scenarios of emission (A2 and B2) for the assessment of climate change impact on drought for two future time periods of 2020-2050 and 2070-2100. Their results showed that the annual drought severity has increased and A2 scenario showed the most extreme condition. In water-scarce areas such as Iran, agriculture demands the highest portion of available water. Irrigated agriculture provides a large portion of the world’s food supply including Iran’s (FAO, 2003). Global warming will highly affect water resources availability by increasing variability of precipitation, increasing air temperature, and frequency and severity of drought in arid and semiarid regions (Kebat et al., 2002). Therefore, understanding and predicting drought trends are a continuous effort to meet current and future challenges in many regions of the world. This study aims to find the drought trend under climate change conditions using drought indices of SPI, PNPI, and ARI in Kashafrood basin.

This study was conducted in Kashafrood basin, which is located in the northeast of Iran. This basin is located between 35o 40' and 36o 3' north latitude and 58o 2'-60o 8' east longitude. Mean annual temperature is 13.6oC and the total average annual precipitation is 220 mm. To assess the impact of climate change on drought conditions in this basin, we used outputs from the HadCM3 model simulations. The HadCM3 model outputs were downscaled by ASD model (Hessami et al., 2008) which is a statistical downscaling method. We employed:i) Simulations made using A2 and B2 emission scenarios which assume the highest and lowest CO2 emissions when compared to the other scenarios, respectively.ii) HadCM3 model outputs are for the period from 1961-2099. This model is a coupled model incorporating ocean circulation. The resolution of this model is 2.5º latitude3.5º longitude.iii) Calculation of drought conditions and drought trends by employing selected drought indices at future periods of 2010-2039, 2040-2069 and 2070-2099.Results and DiscussionThe results of calibration and validation of the ASD model shows that this model fairly reproduced monthly maximum and minimum temperature. Simulated precipitation was not exactly similar to observed data and the differences between them were relatively large and could thus show basically regional biases. Projected temperature (maximum and minimum) under A2 and B2 scenarios showed a rising trend for all three time periods. Results showed that range of increase of maximum temperature under A2 scenario (2070-2099) for spring is 5.4°C to 5.8°C. This range for summer time is 5.1°C to 5°C, for fall is 4.4°C to 5.8°C and finally for winter time is 5.6°C to 4°C. These ranges for B2 scenario are 4.3°C to 4.6°C, 4.8°C to 4.9°C, 4.1°C to 4.9°C and 4°C to 3.8°C for the same seasons, respectively. Highest values of minimum temperature under A2 scenario (2070-2099) were 2°C to 1.7°C, 1.8°C to 4.1°C, 3.3°C to 1.8°C and 1.8°C to 1.1°C, which will occur in spring, summer, fall and winter, respectively. These values under B2 scenario were 1.9°C to 1.4°C, 1.5°C to 3.7°C, 2.3°C to 0.5°C and 0.3°C to 1°C in spring, summer, and fall and winter times, respectively. The percentage of variation for mean annual precipitation under B2 scenario would be 6.7%, 6.3%, and 4% for 2010-2039, 2040-2069, and 207-2099 in comparison with the base period. These values for A2 scenario were 5%, 3%, and 1.5% for the same time periods, respectively. Analysis of the 1-month SPI and 3-month SPI time series showed that the record minimum SPI observed in third month of 1966. Visual inspection of 6-month and 12-month SPI time series showed that droughts were quite frequent during the 1965-1966, 1970, 1971 and 1962-1967, 1970-1971, and 1989-1990. However, several severe dry periods were revealed, considering only the annual minimum spatially averaged SPI value (during 1970-1971, 1966-1967, 1983-1984 and 1989-1990). The precipitation value when expressed as a percentage of potential evapotranspiration is the ARI. The results of this study demonstrate that, dry months occurred quite frequently up to 40% in the base period (1961-1990). However, these dry months were quite irregular during the year. The longest duration of dry period was observed in 1965 and 1980 (April to December). For drought trend assessment, outputs of HadCM3 model and two scenarios emission (A2 and B2) were used. Annual drought severity increase over the historical years was marginal and statistically insignificant (P > 0.5) for the 2055s, 2085s period under SRES B2 scenario. The results indicated that the drought severity and duration (SPI<0) will increase under A2 and B2 scenarios for 2025s but for 2055s and 2085s, the number of dry months will decrease compared to the base period under both scenarios. ARI trends in the three periods are projected to fall. The extreme drought corresponds to 1966 when about 75% months of year experienced droughts with PNPI less than -0.25. In 1972, most months of this year were in normal class (more than 75%). Under A2 scenario, PNPI values were highest, due to higher temperature and precipitation than B2 scenario; thus A2 scenario resulted the lowest increa of drought periods. ConclusionThis study suggests the increase of temperature and precipitation in Kashafrood basin as a result of increasing carbon dioxide (A2 and B2 emission scenarios) in the atmosphere. The projected annual mean precipitation of Kashafrood exhibited an increasing trend for the study periods. Temperature also will increase about 5.8ºC and 4.9ºC under A2 and B2 scenarios for 2070-2099 periods, respectively. The analysis of the drought indices indicated that meteorological drought frequency will increase in Kashafrood basin.Results for ARI differ from the SPI projections because temperature contributes in calculation of ARI and higher temperatures increase evapotranspiration. The results of PNPI were similar to SPI for historical and future periods. The results indicated that climate change would largely affect drought duration and subsequently the design of future water resources projects. Thus, sustainable water management measures should be planned to mitigate future impacts of droughts on Kashafrood basin.

IntroductionClimate is one of the important factors in human life. Now, The human for development of farming, urban and industrial central, increasing of nutrition resource and increasing of information about different climatic regional. Geographer and climatologist determining regional of climatic equal. The study about climate classification shown that climate classification have many method such as experimental, desciptional and classification quantity methods. But now, the application of statistical methods that really puts a lot of climatic factors, which are widely accepted. Khorasan province with an area of approximately 129 000 square kilometers, and it is the fourth of vast provinc of Iran that is have diverse topography and therefore the climate is diverse. Since, about of climatic classification on Khorasan by using multivariate statistical study has been done, therefore in this study has identified areas and also climatically isoelectric significant elements that have shaped the face of climate, are identified.Materials and MethodsFor climatic mapping in the area under study the 20 number variables from the 14 number stations inside and outside of the area under study have been used in the period between 1986-2005. In the next step, Kriging method has been done for interpolation using ArcGIS software in the 1515 kilometer pixels in dimension. We have used from 52120 produced matrix in dimension as input for statistical analysis. By using factor analysis, the 4 number factors have been identified that explain 91 total percents of climatic behavior in the area under study.DiscussionThe use factor analysis with principle component method and varimax shown that 20 climate element of province can whith its aoutcorolation to 4 factor. By using factor analysis, the 4 number factors have been identified that explain 91 total percents of climatic behavior in the area under study. These factors are given by thermal factor, atmospheric moisture, pressure and wind. Factor shows that the thermal loads operating variables, the average maximum temperature, mean annual temperature, mean minimum temperature, mean annual evaporation, and the number of sunny hours positive correlation with rainfall and humidity elements show an inverse relationship. Local dispersion of these factors shows that thermal factor is the main factor in the south, eastern and western edges of area under study. Investigation of variable moisture content shows that the dew point temperature, vapor pressure, mixing ratio, days of Thunder Days of cloud and moisture factors have the greatest weight on humidity factor. The second factor is dominant in the northern half of the study area. The third factor, with sea level pressure, humidity, days of Thunder and the family, solidarity with the families directly and inversely related to temperature shows. The pressure as a third factor affects the climate of province. The fourth factor represents the average wind speed and the number of operating days of thunder and wind and dust to dust is the medium that has been called windy-dusty factor. The third factor is dominant in the western north of the area under study and the fourth factor is dominant in the north and south. The most obvious climatic feature is the wind speed in this area.Results showed that the climate of province, make from four main factors that explain 92% of the climate condition. These factors in order of importance are: the heat, humidity, pressure and wind. Spatial distribution of these factors indicate that the thermal operating margin in the south and east and west of the province is effective. The second factor is dominated in the northern half of province. Spatial distribution of the third factor mainly prevails in North West. Finally, the fourth factor in the Top End of northern and southern study area is the dominant climatic phenomena. Finally, Ward approach is used for climatic mapping in the 5 homogeneous classes as follow: 1 warm and Arid. 2) Semi Arid and warm. 3) Semi Arid and cold. 4) Mountainous and Cold. 5) Moderate Mashhad plain.

IntroductionDust storms are natural events and are common in the dry land areas. The severe droughts can increase the number of dust storms, particularly during the summer months. Dust storms reduce air quality and may have adverse effects on health, particularly for people who already have breathing-related problems. The most common experienced symptoms during a dust storm are irritation to the eyes and upper airways. The most vulnerable people are infants and young children, the elderly and people with respiratory conditions (e.g. asthma, bronchitis and emphysema) and heart diseases. For these people, exposure to a dust storm may, trigger allergic reactions and asthma attacks, cause serious breathing-related problems, contribute to cardiovascular or heart diseases, contribute to reduced life span. Visibility deteriorates very quickly during a dust storm. Low visibility has important effects on transportation. In these days, dust storm is one of the major environmental disasters in the Middle East. Dust storms happen in the Middle East with very high frequency. According to the mentioned dust storm effects, it is vital to study the dust storms in the Middle East. The first step toward the study on of dust storms is to identify the point sources of dust storms. In addition, it is necessary to find the properties and the characteristics of the point sources and to determine the most important regions in Middle East with high density of point sources. Remote sensing is an appropriate tool for these investigations. Many different dust indices have been developed for the dust identification from remotely sensed images. In this study, a new false color composite method is developed for the identification of the point sources of dust storms in the Middle East using the dust indices. Then, the properties of the point sources are determined and finally, the share of different countries in the dust storm generation is investigated.In this study, MODIS images were utilized as remotely sensed images. MODIS images have been used successfully for dust storms detection. 28 MODIS-Level 1b images from 2008 to 2009 were selected and received from the archive of Iranian Space Agency. The software package for the image processing was ILWIS 3.7 (Integrated Land and Water Information System). The digital number of satellite images converted to the radiance and reflectance data. Then the different famous dust indices were developed using the MODIS images. These indices were BTD3132 (Brightness Temperature Difference in band number 31 and 32), BTD2931 (Brightness Temperature Difference in band number 31 and 32), NDDI (Normalized Difference Dust Index) and D (Roskovensky and Liou, 2005). Different false color composite maps were generated using these Indices, bands 3 and band 4 of MODIS images. Then the performance of different color composite map was evaluated using visual interpretation and the best color composite method for dust enhancement was selected. Then using the selected color composite method, the point sources in 28 MODIS images were identified and after that, all of the identified point sources were combined in GIS environment. Then the share of each country in Middle East in dust storms generation was determined according to the number of point sources in their territories. For determination of the characteristics of the point sources, the point sources map was combined with DEM map, Geological map and NDVI map of Middle East in GIS environment. Finally, we tried to determine the regions with high density of point sources and major role in dust storm generation using the point sources map and IDW (Inverse Distance Weighting) interpolation technique.The visual interpretation of the generated False Color Composite maps demonstrated that the best combination for dust identification is the utilization of D, BTD3132 and NDDI indices as the Red, Green and Blue bands of color composite map, respectively. Using this color composite method, about 420 point sources were extracted from 28 MODIS images and point sources map was generated. The point sources map showed that about 39.2, 23, 14.5, 13.8, 5.7 and 3.7 percent of the point sources of dust storms have been located in Iraq, Syria, Saudi Arabia, Iran, Jordan and Turkey territories, respectively. These results mean that more than 60% of dust storms are generated in Iraq and Syria. Combination of NDVI map with point sources showed that the point sources often have been located in the region with low NDVI values (low vegetation covers). Almost all of the point sources have been located in the planes with low altitude (elevation less than 400 meters). In addition, combination of geological map with the point sources map showed that the surface of the point sources regions often have been covered by non-rigorous soil formations. Therefore, the main characteristics of the dust point sources in Middle East have been determined. To determine the density map of the point sources, the gridded point sources map was interpolated by IDW and an indicator map for density of point sources in the Middle East was generated. The indicator map demonstrated that the main regions of dust storm generation are two regions in western Iraq and eastern Syria.MODIS images were very useful for the identification and detection of dust storms. In this study, a new false color composite map was developed for dust storms and point sources detection using the famous dust indices. This color composite was generated by the combination of D, BTD3132 and NDDI indices. The point sources of dust storms in the Middle East have been located in the regions with low altitude, low vegetation cover and non-rigorous soil surface. More than 60% of dust storms are generated in Iraq and Syria (especially in the western Iraq and eastern Syria) and transferred to the other parts of the region by the wind. The share of Iran in dust storm generation is about 13.8 %.

IntroductionAccording to the urban green space development, water resources reduction, and other various factors, it seems necessary to use of sprinkler irrigation in irrigating the urban green space. There is no clear and principled method to determine the sprinkler system layout of green spaces. Sprinkler layout usually has a triangular or square pattern and is estimated automatically. In this paper, using genetic algorithm, the location of Sprinkler system installation is determined. In order to provide the maximum distribution uniformity.Materials and methodsAt first, the spray pattern of Hunter A17 sprinkler on the farm of Islamic Azad University of Ferdows in Iran and the regional environmental conditions were determined, and then the sprinklers location was obtained by genetic algorithm. In this algorithm, the points on the map were elected as index points (sample containers). These points have a one-meter distance from each direction, horizontally and vertically. Genetic Algorithm is a searching method of optimization that has been inspired by human body. Chromosome structure that has been presented in the algorithm is a set of two-dimensional coordinate system of the of sprinkler location on the map. These coordinates are a binary number with eight bits, so chromosome length is 144 bits. The structure contains nine sprinklers that have nine two-dimensional coordinate systems. This plan aims is to achieve high distribution uniformity coefficient for the farm. Therefore, the objective function is a part of distribution uniformity formulation of the farm. Obtained uniformity coefficient depends on the number and spray pattern of a single sprinkler (which is depends on climatic conditions). Considering the spraying radius of sprinklers and preventing he water outgo from the field, coordinate selection is not limited to length and width of the field. Minimum distance of coordinate sprinklers location from the field border must be equal to spray radius. For this reason, border strip has supposed equal to 3, 4 or 5 meter and algorithm run with these strips. This problem was supplied by increase the distribution uniformity. The increase of the distribution uniformity will decrease deep percolation.Results and Discussion The distribution uniformity changes with variation range of border strips. If the range of border strips decreases, the distribution uniformity will increase. Considering the experimental farm, uniformity coefficient obtains 78.9 percent from genetic algorithm method, versus the coefficient for the manual method of sprinkler’s layout obtained 73.3 percent. Conclusion Genetic Algorithm is used less in irrigation science and this research tries to create a new vision to this aim. This research concluded that, Genetic Algorithm is one of the best methods in optimizing this complicated problem.

IntroductionUnderstanding the current climate change conditions and planning for the future requires the knowledge of paleoclimatic conditions which has been studied less in Iran. Although there are diverse methods to detect these changes, to select the proper one, the range of time period, environmental conditions and data access should be taken into account. Materials and methodsOne suitable method of studying paleoclimatic conditions is oxygen isotope analysis. This research aims to identify climate change in Arjan Lake located in the southwest of Iran on the basis of geological proofs. To achieve the aim, a process is carried out. First, 9 cores were taken at depths of 1 to 3 meters in the study area. Second, sediment sections were divided into 5 centimeters for counting the Ostracoda shells. Third, in order to determine the exact age of the sediments, the method of C14 was applied in 3 samples in the different depths of the lake. And finally, the isotope values were measured using 22 samples at different depths of the lake. Results and discussionThe results of the research based on the oxygen analysis represents 12 climatic zones during 11 thousand years ago. Negative isotopic values indicated a cooler and wetter climate compared with the present time. The results also shows that there is a sharp gradient in isotopic extreme values indicating climate fluctuations in the study area.C13& O18 values shows that the lake experienced warmer and drier conditions in 11 thousand years ago. The driest and coldest periods were distinguished in 2020-2213 and 4261 years ago, respectively. ConclusionClimate fluctuations in the study area might be linked with changes in the atmospheric general circulation and regional elements determined temperature based on the isotopic values of calcite. This can offer a clearer picture of the past climatic conditions.

IntroductionPrecipitation regime refers to the distribution of precipitation over time and depicts the number of cycles per year. Most of the economic activities (e.g. agriculture) in every given region are adapted to the precipitation regime. The change in precipitation regime can affect these activities as it affects water resources. Accordingly, it is important to analyze these changes in every geographical region.A change in the precipitation regime as a change in the temporal pattern of precipitation is one of the effects and results of climate change. This phenomenon is has received much attention from climatology experts. They have studied this phenomenon using many techniques. One of the most important features in analyzing the change of precipitation regime is to study the periodicity of different harmonics. The harmonic number shows the number of cycles during the year. For example first harmonic shows one cycle per year while the second harmonic shows two cycles and … in one year.Materials and methods In this research, 7.2 percent of lands in the northwest have been studied. This area is about 118670 square kilometers. This area contains two kinds of topographies: rough mountainous area and the flat areas among it. In order to accomplish this research, time series data of 260 well-scattered synoptic, climatology and rain gauge stations are analyzed. Monthly precipitation maps have been created to obtain an acceptable cover even for lake of data stations. The research has been done on the basis of harmonic analyses. As it has been mentioned before, harmonic analyses show the numbers of cycles during the year.For a given time series Xt, can be written as a combination of different sine signals as follows: Where is the arithmetic average of the original data series, while the rest of the terms represent the first, second. .. n/2th harmonic analysis of the period T. The amplitude can be written as The percentage of the total month to month variations explained by a given harmonic can be determined by forming a ratio of the square of the amplitude of that specific harmonic to the sum of all harmonics; as follow:In other words, the importance of the total month to month variation explained by a given harmonic can be determined by forming a ratio of that harmonic variation to sum of all harmonics. The main objective of this study is to investigate and analyze the first three harmonics of four successive decades (1966-2005) in northwest of Iran (West-Azarbayjan, East-Azerbaijan, Ardabil, and Zanjan). All calculating operations have been done on map cells in order to achieve the harmonic characteristics.Results and discussion Annual precipitation of northwest of Iran increased from northeast to southwest. Tremendous spatial change is dominant on precipitation. Unexpectedly, the maximum precipitation does not occur on the summits of the mountains. Based on the methods used in this paper, it is revealed that both systems, synoptic and local, explain more than 90% of precipitation variations.The first harmonic explains the maximum precipitation variation in southwest from which to northeast the ratio of precipitation is decrease in region that the ratios of synoptic systems are minimized. Therefore, local systems (convective, orographic and local frontally and so on) have greater roles here. However, as annual precipitation increased, the synoptic share in precipitation increased too. So, the southwest experienced more precipitation. This is true for all four decades by oscillate behaviors. Changing the first harmonic ratio, the others have changed too. All changes lead to an increase in annual precipitation concentration and a decrease in its distribution over time.ConclusionAccording to this paper, precipitation regime in northwest of Iran has experienced a big change especially during the last decade. This can be seen in the ratio of every cycle among the data. This change happened in the area with concentrated and non-concentrated precipitation. Accordingly, the areas changed from non-concentrate to concentrated regime and vice versa. So, it seems necessary to recognize these changes for water resources management and planning.