Showing 87 results for Ira
Saeed Javizadeh, Zahra Hejazizadeh,
Volume 19, Issue 53 (6-2019)
Abstract
Drought is one of the environmental events and an inseparable part of climatic fluctuations. This phenomenon is one of the main characteristics of the various climates. Awareness of spatiotemporal behavior is effective in land planning. The spatial statistical methods provide the means by which they analyze the spatial patterns of random variables such as precipitation. In this study, using the rainfall data of 84 selected synoptic stations during the period of 30 years (1985 to 2014) in Iran, the spatial analysis of drought has been investigated. Initially, using SPI values (timescales 3, 6, 12, 24 and 48 months), drought and traumatic periods of the area were identified and using the Geostatistic Analyst extension, the drought was zoned by interpolation methods. Moran statistics were used to explain the pattern of drought in Iran. The results of Moran index for drought showed that the values for different years during the statistical period have a positive and close to one, indicating that the SPI drought index data has spatial self-correlation and cluster pattern. Also, the results of Z score and P-value values, clustering of a spatial distribution of drought, were confirmed.
Dr Mahmoud Hooshyar, Dr Behrouz Sobhani, Nader Parvin,
Volume 19, Issue 54 (9-2019)
Abstract
Early heat waves are extreme events that cause heavy losses in plant and animal life and cause many social and economic problems for communities. The purpose of this study was to identify synoptic patterns and statistical analysis of preterm heat waves in northwestern Iran. To do this, the maximum daily temperature data of March 14th was used for fourteen synoptic stations in the northwest of the country during the statistical period (1333-1393) Hijri Shamsi. Then, on the basis of the threshold, the Baldy index was selected for 61 days of heat wave. All statistical characteristics of the data were processed in SPSS software. They were The elevation data of the middle atmosphere of the atmosphere was extracted from a NCEP / NCAR database on a network with an arc 2/5 × 2/5 degree on the 0 to 70 degree eastern longitude and 0 to 60 degrees north latitude. The matrix was made up of 864 columns in 40 rows, with rows of days with thermal waves and elevation data on the columns on the middle of the atmosphere. The analysis of the basic components was performed on the algebraic data matrix matrix And 12 components that account for about 93 of the variations in pressure levels above 500 hp, were identified. To identify the coherent patterns, cluster analysis was performed on the scores of the components by the WARD integration method. Five types of pre-heat generation waveform patterns were identified. The results of this study showed that the premature heat waves in the northwest of Iran are due to high altitude formation in southern Arabia, the Aden valley and the center of Sudan at a level of 500 hpa and the formation of Sudan's low pressure in the sea level and the discharge of its tabs to the north and northeast of the region The case study (Northwest of Iran) also includes events occurring.
Miss Ensie Goharinasab, Dr Hossein Zabihi, Dr Shirin Toghyani,
Volume 19, Issue 54 (9-2019)
Abstract
Today, due to the transformation of the form of life and the proliferation of quantitative, gradually the qualitative and semantic concepts of the spirit of neighborhood in the minds of residents are dimmed. Factors such as immigration, Changes in the social composition of the population, Continuity of residence and persistence in neighborhoods have diminished. With the lack of infrastructure refinement, due to the lack of local community in the process of identifying problems and accurately measuring their needs, has led to a sharp divide between the efficiency of the neighborhoods and the needs of the inhabitants of the establishment and the neighborhoods have led to inefficiencies. While some modern neighborhoods are planned in a short time. On the contrary, the process is moving traditional neighborhoods. The main question is that the standards of a lasting Iranian neighborhood are up to date, from the point of view of the main inhabitants? The purpose of this paper is to answer the question that, What are the criterias of Up-to-date of persistent Iranian neighborhood, from the perspective of the main inhabitants? This analytical-qualitative study uses the Grounded theory method, Purposeful sampling of 5 neighborhoods with the statistical population is 86 people (until theoretical saturation) from the main residents. By means of position analysis, the final criteria were fixed. The parameters of security, sense of place, social status, spirituality and modern technology are one of the most important criteria for the survival of residents. The results show that the neighborhood, from the point of view of the inhabitants, goes beyond the broad concepts of elitist rigidity, more often than not, in simple mental and intriguing indicators, which require the recognition of the social reality of the people and the real needs of their daily lives with the collaborative interactive planning approach The dialectical relationship is between the opinion of experts and the views of residents in order to refine and update the neighborhood. The manifestation of the concept of Persistent Iranian Neighborhood is updated on the basis of principles: efficiency, persistence, dynamism and continuity in the form of conceptual model.
M Masoud Jalali, M Mehdi Doustkamian, A Amin Shiri Karim Vandi,
Volume 19, Issue 55 (12-2019)
Abstract
The aim of this study was to analyze the mechanism is precipitation Comprehensive Iran. For this purpose the daily precipitation data of 483 synoptic and climatology stations arranged. In this study, a comprehensive annual rainfall is said to have a minimum rainfall and above, 50% sequence coverage and have at least two days. Winter surround Iran on the condition of rainy days were extracted and examined. Then, to review and analyze the mechanism of atmospheric precipitation comprehensive synoptic and dynamic parameters such as moisture flux, vortices, ground level pressure, Geopotential, meridional and zonal wind component for the levels of 1000, 850, 700 and 500 HP studied and analyzed was. The results of this study showed that the widespread mechanism of dynamic and synoptic Winter country most affected by the composition of the atmosphere patterns such as the Mediterranean low pressure - low pressure core Persian Gulf, Iran, Central High East Europe closed low pressure, low pressure Urals - the Middle East, high pressure, low pressure Saudi Arabia - High pressure belt Europe and Siberia - Iran's low-pressure center. However most of the winter precipitation of moisture flux feed barley middle-Level interaction, particularly levels of 850 and 700 HP respectively. It was while change 500 hPa atmospheric dynamical mechanism is an important role in Iran's winter inclusive.
Msc. Graduated Student Najmeh Daneshvar-Marvast, Dr Somayeh Soltani-Gerdefaramarzi, Dr Samaneh Poormohammadi,
Volume 19, Issue 55 (12-2019)
Abstract
The phenomenon of evapotranspiration causes water and moisture losses from water, soil and vegetation levels. Due to the small amount of atmospheric precipitation and water resource constraints in Iran, it is important to calculate it through a suitable method. The present research attempts to evaluate the evapotranspiration reference crop (ETo) and present it in the form of zoning map as a basic tool for water management. In this study, the long-term average of seven meteorological stations and evaporation pan data were used to determine the appropriate ETo estimation method. Evapotranspiration of reference crop was calculated to 14 methods the based on climatic information in each station. Computational methods including combinational methods Penman-based, radiation-temperature method, temperature method and radiation method. The most appropriate computational method was selected based on the R2 and Nash -Sutcliffe statistics. The zoning of evapotranspiration of reference crop was carried out based on the geographic information of the meteorological stations and the GIS software. The results of the research indicate that the best method for this region as the cold and moderate climate are FAO radiation and Blaney-Criddle. Also, the zoning result shows that west of the catchment has less evapotranspiration rather than its east. Sunshine hours, maximum temperature and wind speed were the most effective factors for evapotranspiration in this area by sensitivity analysis.
Hossein Naserzadeh, Fariba Sayadi, Meysam Toulabi Nejad,
Volume 19, Issue 55 (12-2019)
Abstract
This research was carried out with the aim of understanding the spatial displacement of rainfall nuclei as an effective factor in the future hydrological conditions in Iran. Two types of databases were used to conduct this research. The first type of data is the monthly precipitation of 86 synoptic stations with the statistical period of 1986-1989 and the second type of predicted data from the output of the CCSM4 model under the three scenarios (RCP2.6, RCP4.5, and RCP6) from 2016 to 2036. After collecting and modeling the data, the maps were mapped to the ARCGIS environment. The results of the study showed that the terrestrial nuclei in the whole of Iran's zone in the four seasons will have changes with a negative trend in the future. The coefficient of rainfall variation in the spring, summer, autumn and winter seasons will be 61.4, 101.4, 58.9 and 55.8 percent, respectively. The results of the triple scenario study showed that the displacement of the spring core from all north north of the country to the northwest of the country is limited to the common borders of Iran, Turkey and Armenia (the Maku and Jolfa region), but in summer, the high core The northern shores and parts of the northwest of the country will be transported to the south of the country (around Khash and Saravan). In the autumn, the high-lying zone, which is located throughout the northern part of the country, will move to two distinct nuclei in the central Zagros (Dena and Zadkouh areas) and southwest Khazars (Anzali and Astara areas), and the core of winter from the central Zagros And the Caspian region will be transferred to the northwest of Kurdistan and southwest of West Azarbaijan, which will be seen in all scenarios. Another point is that, in addition to reducing the boulders, in the future, drought areas will cover more of the country.
Mehdi Asadi, Mokhtar Karami,
Volume 20, Issue 56 (3-2020)
Abstract
The purpose of this study is to determine the evapotranspiration in Fars province that in many studies such as hydrological balance of water, irrigation systems design and management, simulation of product volume and management of water resources is very important. To do this, first, required data such as daily temperature, humidity, precipitation, wind speed, solar radiation pressures, solar radiation, etc. was collected. We used 12 stations with the same statistical interval, for the period 1995-2015. In order to estimate the evapotranspiration of the reference plant in different growth stages, Torent White, Penman-Monteith and Hargreaves-Samani methods were used. Results showed that with decreasing latitude, the evapotranspiration rate increased, and the highest rate of evapotranspiration occurs in the south, southeast and the center of the study area. The correlation coefficient R2 between height and White Penman, Monteith and Hargreaves Samani, are 0.9135, 0.53223 and 0.5286 respectively.
Dr Mohammad Ebrahim Afifi,
Volume 20, Issue 56 (3-2020)
Abstract
Land use maps are considered as the most important sources of information in natural resource management. The purpose of this research is to review, model, and predict landslide changes in the 30-year period by LCM model in Shiraz. In this research, TM Landsat 4, 5 and OLI Landsat 8 images were used for 1985, 2000 and 2015 respectively, as well as topographic maps and area coverage. Subsequent validation and detection of changes were made using the prediction model of variation The use of LCM markov and the model of user change approach. The images were classified into four classes of Bayer, garden, urban lands, and arable land for each of the three periods. According to the results, aquaculture is the most dynamic user in the area, which has led to an upward trend during 1985-2015, so that the amount (4337 ha, 12.7%) has been added to this area. The Bayer user change trend was also a downward trend during 1985 to 2015, reducing the 99.1995 hectares of this class. The results of the change in the 1985 changes with a kappa coefficient of 0.88, in the 2000 period with a CAAP of 0.77, and in the period 2015 with a Kappa coefficient of 0.92. The results of the change detection in 2030 are such that if the current trend continues in the region, 20.33% will be added to the crop category, so that in 2030, agricultural cropping will be 95.60% of the area of the area Gets In the Bayer and Garden uses 21.22% and 0.21% of the total area of each user has been reduced and has been added to the urban area. The prediction map derived from the Markov chain model is very important for providing a general view for better management of natural resources.
Ms Mahboobeh Pouratashi, Dr Mohammad Moradi, Dr Ebrahim Fattahi,
Volume 20, Issue 57 (6-2020)
Abstract
This research aims to study the impact of temperature and wind in the southern low-pressure system and its associated precipitation in the southern regions of Iran. As The southern low pressure system moves eastward, it crosses the southern regions of Iran, causing medium and heavy rainfall in these areas. In this study, two southern low-pressure systems that caused heavy rainfall on March 11, 2015 and January 17, 2000 in southern Iran were selected, analyzed and simulated using the numerical Weather Research and Forecasting (WRF) model. Since the wind and temperature fields play a significant role in the southern low-pressure systems, four experiments were performed for investigating the effects of temperature and wind on the intensification and weakening of the southern system. The simulation results showed that the simulation for the increased (decreased) temperature caused the weakened (intensified) the southern low pressure in the studied area. This result showed that the vertical structure of the southern low-pressure and its physical characteristics are similar to the mid-latitudes cyclones, and these systems were different from the thermal low pressures. The results of wind speed changes showed that the increased (decreased) wind speed simulation caused an increase (decrease) in relative vorticity, thus the southern low pressure was intensified (weakened). In both cases, the rainfall was decreased by the increased temperature simulation, and decreased temperature caused an increase in rainfall. It was also seen that the increase in wind speed caused the special humidity advection to be increased and then the rainfall increased. Also the amount of rainfall decreased when conditions did not provide for the advection of specific humidity or the wind speed reduced.
Mohammad Hossein Nasserzadeh, Zahra Hejazizadeh, Zahra Gholampour, Bohloul Alijani,
Volume 20, Issue 57 (6-2020)
Abstract
The plant community in an area is the most sensitive indicator of climate. A visual comparison of climate and vegetation on a global scale immediately reveals a strong correlation between climatic and vegetation zones and this relationship, of course, are not co-incidental. The main object of this study is to reveal the spatiotemporal association between climatic factors andvegetation Cover (NDVI) incorporate MODIS and TRMM product in Kohkiloyeh O Boirahmad province of Iran. So that the in this paer we use MOD13Q1 of MODIS product as NDVI layer for study area. MOD11A2 as landsurface temperature and 3B43 TRMM as meanmonthly accumulative rainfall for study area during 2002 to 2012 in 0.25° spatial resolution also were used as climatic factors. We use the correlation and cross-correlation analysis in 0.95 confident level(P_value =0.05) to detection the spatial and temporal association between the NDVI and 2 climatic Factor(LST and rainfall). The results indicated that during winter (December to March) the spatial distribution of NDVI is highly correlated with LST spatial distribution. In these months the pixels which have the high value of NDVI are spatiallyassociated with the pixels which have highest value of LST (6 to 14C°).As can be seen in table 1. Season the spatial correlation among NDVI and LST is so high which is statistical significant in 0.99 confident level in winter. In transient months such as May, October and November,(temperate months in study region ) the spatial correlation among NDVI and LST is falling to 0.30 to 0.35 which is not statistical significant in 0.95 confident level. Finally in summer season or warm months including Jun to September, we found the minimum spatial association among the NDVI and LST.. In temporal aspect we found that the maximum correlation between NDVI and LST simultaneously appears and not whit lag time. The spatial correlation of NDVI and TRMM monthly accumulative rainfall was statistical significant in spring season (April to Jun) by 1 month lag time in remain months we don’t find any significant correlation between NDVI and rainfall.
Dr Elahe Kavoosi, Dr Jamal Mohammadi,
Volume 20, Issue 57 (6-2020)
Abstract
The ‘Smart mobility’ has become an increasingly prevalent discussion topic in the past few years, not just in academic literature but also in cities’ policy and strategy. However,in many cities of the world and in our country, Iran has been associated with problems such as lack of citizen participation and inequality (caused by inefficient urban management). The present study has attempted with an innovative perspective to evaluate the existing infrastructure of mobility indicators (including transport infrastructure, public transport, sustainable transport, ICT) and the social dimensions of these infrastructures including the extent of citizen participation in use. Of these infrastructures) in eleven districts of Shiraz.The research method is descriptive-analytical and based on documentary and origin studies. Data gathering was field study by using a questionnaire. The 5-degree Likert spectrum technique was used to measure the value of indicators of the Smart Mobility. The results show that average smart mobility was higher in regions 1 and 6 than in other regions. the average smart mobility indicators are in 11 and 9 the lowest in other regions. The Urban Smart Mobility variable does not have an appropriate position in Shiraz, and this has not only affected its development process in recent decades, but also poses many challenges for its future development. Accordingly, urban planners should Consider the citizen participation and efficient urban management.
Dr Yagob Dinpashoh, Miss Masoumeh Foroughi,
Volume 20, Issue 58 (9-2020)
Abstract
Reference evapotranspiration (ET0) is a climatic parameter and can be computed from weather data. It is one of the most important hydrological parameters for calculating crop water demand, scheduling irrigation systems, preparing input data to hydrological water-balance models, regional water resources assessment, and planning and management for a region and/or a basin. The climatic data from synoptic stations with more than 20 years continues record in West Azarbaijan province was used. The well-known FAO-PM56 method was used to calculate the ET0. Then Multiple linear Regression (MLR) was used to estimate the ET0. The RMSE, MEA, NSH, and R2 were used to evaluate the performance of the MLR model. Then, the correlation coefficient (r) between ET0 and each of the meteorological parameters was obtained. And finally, with using Path analysis method, the influence of direct (P) and indirect effects of the meteorological parameters on ET0 was calculated. In the studied synoptic stations, NSH between 0.91 and 0.99, R2 between 0.91 and 0.99, RMSE between 0.05 and 0.15, and MEA between 0.04 and 0.12 were obtained. Also, it was found that the wind speed at all of stations had a significant correlation (at the 0.01% level) with ET0. The path analysis results showed that the maximum value of P (direct effect of meteorological parameters on ET0) in all of the stations belongs to wind speed. The P value of wind speed in Urmia equal to 0.85, Piranshahr equal to 0.99, Takab equal to 0.97, Khoy equal to 0.90, Sardasht equal to 1.06, and Mahabad equal to 0.78 are obtained.
Dr. Sadegh Karami,
Volume 20, Issue 59 (12-2020)
Abstract
Importance of climate change is global. This issue to some extent has been out of human control. Human beings can only provide security and the community with knowledge and management against its negative consequences. On the basis of this research, the present paper analyzes the impact of climate change on Iran, on a small scale and applied to the central catchment area. The findings of the research indicate that climate change has shown the geographic region of Iran in terms of changing the rainfall pattern, decreasing precipitation and increasing its temperature. In the next step, these cases resulted in excessive withdrawal of groundwater aquifers and it has reduced the quality of underground water. This chain has led to the design of inter-basin water transmission projects, which is at least the result of the cycle of social tensions that has occurred in recent years. Considering the geographical extent of the basin and its belonging to one of the most frequent aspects of Iran's civilization, the set of consequences of climate change in the central catchment area, in addition to its impact on various social, political, economic and environmental layers, also has several scale effects. And its destructive effects go beyond national scale and to an extent beyond the scope of Iranian culture. In this regard, the research findings indicate that climate change in the central watershed is influential in many aspects of society and the country, so that if the current process continues, the current Iranian civilization will face a strategic challenge. To this end, at the end of the research, good water governance, as the best way to confront and control the negative consequences of climate change on the central catchment area, and Iran in general, has been argued.
Mrs. Nasibeh Baharvandi, Dr. Firouz Mojarrad, Dr. Jafar Masompour,
Volume 20, Issue 59 (12-2020)
Abstract
The heat wave is a long period of warm climate, compared to the expected conditions in a region over a certain period of the year. Heat waves cause mortality, disease and various problems in different fields of transportation, agriculture, production and energy. It is very important to study the changes in spatial and temporal patterns of these waves to understand the causes of the incident and confront them. In the present study, using the "Heat Wave Magnitude Index daily" (HWMId), which takes into account both the intensity and the wavelength of heat, the heat waves of Iran between 1985 and 2015 have been analyzed in terms of spatial and temporal distribution. For this purpose, using the maximum daily temperature data of 44 synoptic stations of the country and on the basis of the threshold of the 90th percentile, the heat waves greater than or equal to three days were identified at each station. After applying the HWMId on the days of each heat wave, the magnitude of each wave was calculated. Then, the average number and magnitude of all waves, as well as the most severe ones, were calculated in annual and seasonal scales and the corresponding maps and charts were drawn up. The results of the study showed that the highest number of heat waves occurs in the western part of the Zagros Mountains and then the Kavir Plain; while the maximum magnitude of heat waves belong to the south-east and central parts of the country. Autumn and then winter season have a high share of the most severe heat waves during the study period; while the spring and summer heat waves are relatively weaker, and are more limited in terms of expansion. The most severe heat waves during the study period have occurred in the winters of 2008 and 2010. The number and magnitude of heat waves in the country is increasing significantly. The largest increase in the number belongs to the summer and the magnitude belongs to the winter.
Ms Elahe Kavoosi, Dr Jamal Mohammadi,
Volume 21, Issue 61 (6-2021)
Abstract
Our country Iran is not far from the global changes of cities. One of these changes is the smart mobility that is Undeniable and inevitablein urban management today. Especially in metropolises, which are facing increasing population and various economic, social and environmental problems. In fact, metropolises always have many problems, most importantly transportation. Shiraz, as one of the major cities and one of the major cities of the country, has a special place. This position is of different cultural, historical, political and other aspects. Its population growth rate has also been steadily increasing due to its location. This trend of population growth over the past few decades has created problems and obstacles for sustainable and desirable management, most notably problems in the transportation sector. The same trend illustrates the need to emphasize smart systems in this city. Therefore, in this study, it is attempted to investigate and analyze Smart Urban Mobility and Social Sustainability for Shiraz. The research method is descriptive-analytical and based on documentary and origin studies. The results show that the mobility and displacement variables are in poor condition based on different dimensions of access, sustainable transport as well as ICT. Different indices of each of these dimensions point to the same issue, as its level of evaluation (significance level less than 0.05 and average lower than the criterion) points to their undesirability from the point of view citizens. The study of the impact of smart mobility indicators on Social Sustainability also shows that smart mobility indicators account for 23% of the total variance of Social Sustainability. On this basis, it should be noted that the mobility variable does not have an appropriate position in Shiraz, and this has not only affected its development process in recent decades, but also poses many challenges for its future development. The growing trend of the population and on the other hand the various social and cultural features as well as tourism are evolving in such a way that it requires a major focus on a systematic transportation based on smart city approach.
- Nesa Sepandar, Professor Kamal Omidvar,
Volume 21, Issue 61 (6-2021)
Abstract
In this study, we tried to identify the sources of moisture and its direction of heavy rainfall in south and southwest of Iran by using a new algorithm based on atmospheric rivers. For this purpose, daily rainfall of 17 synoptic stations in the period 1986 to 2015 in south and southwestern Iran that have a common time span and fully cover the study area is used.Also from the data set of the National Center for Environmental Prediction / National Center for Atmospheric Research (NCEP / NCAR) European Mid-Term Forecast Center (ECMWF) and ERA-interim data with spatial resolution of 0.75 It was used at 0.75 latitude and longitude with 6 hour resolution. The variables used are integrated water vapor (IWV), specific humidity (q), and orbital and meridional components (u, v). In this research, an algorithm based on the calculation of Vertical Horizontal Vapor Transfer Integral (IVT) is used to identify and navigate atmospheric rivers. The results show that the main source of rainfall moisture is in south and southwestern Iran, south of Red Sea and Gulf of Aden. Of course, the maps show that the Arabian Sea was not affected by the humidity.The Arabian Peninsula also, due to the high moisture transfer rate, as a transitional route, transmits a large amount of moisture to the study area.Finally, the path of moisture to the study area was mapped and identified, and thus considering the three main conditions for the atmospheric river, it can be said that the path obtained is the same as the atmospheric river.
Farshad Pazhoh, , Mehry Akbary, Mohammad Darand,
Volume 21, Issue 62 (9-2021)
Abstract
The aim of this study is to identify the spatial distribution of Vertically Integrated Moisture Flux Convergence (Vertically Integrated) Moisture Flux Convergence) on Iran’s atmosphere. To achieve this aim, the monthly ECMWF gridded data used during the period from 1/1979-12/2013. First, based on the specific humidity content in the atmosphere, troposphere divided into three layers (850-1000hPa), mid (700-775hPa) and upper (500-600hPa). In order to achieve VIMFC spatial variations on Iran, spatial self-correlation methods of globular moron and hot spots used at 90, 95, 99 and 99/99 percent significance levels. The results of this study showed that the spatial distribution of VIMFC in Iran during the first layer of troposphere and especially during warm months of year has a high cluster pattern and in cold months of the year and in the third layer of troposphere cluster pattern decrease. Based on the hot spots index in the first layer of troposphere low height regions, in the second layer of troposphere the high regions of the Alborz, zagros and central mountains and in the third layer of troposphere alpine regions of central and eastern Iran's mountains has positive spatial self-correlation (hot spots). The results show that in winter and autumn during the second period (1999-2013), the range of hot spots of the VIMFC show a significant reduction compared to the first period (1979-1998) on Iran.
Asal Falak, Reza Boran, Farideh Asadian,
Volume 21, Issue 62 (9-2021)
Abstract
This study aimed to investigate the temporal-spatial and synoptic features of thunderstorms in southwest of Iran (Khuzestan, Chaharmahal & Bakhtiari and Kohkiluyeh & Boyerahmad Provinces) It was compiled using volatility indices during the period 1985-2015. Results of Frequency Analysis of Thunderstorms at Dezful Station with 479 cases the highest frequency and Ramhormes with 252 days had the lowest frequency. In terms of seasonal distribution, spring was the most abundant with 39%. On a monthly basis, April had the lowest frequency with 21% and August with only 2 cases. In terms of thunderstorms the highest frequency of thunderstorms with no thunder was 21 percent. Synoptic analysis: Most of the time there is a nave (at level 500) or low pressure in the west of the region, east of the Mediterranean Sea with its tabs clockwise. From the Red Sea and the Persian Gulf, they entered the south, southwest, and west of Iran On the other hand, the high-pressure system on the Gulf of Aden in the east of the region is round in the clock It has injected moisture, especially at a level of 850 millibars. Interaction between the two systems over the course of the day, It has injected moisture from three sources of the Mediterranean Sea, the Red Sea and then the Persian Gulf into the rising systems of the region. The low-pressure counterclockwise movement of the eastern Mediterranean, Along with the high-altitude clock movement over the Gulf of Aden, it has injected moisture at levels of 850 to 700 degrees.
Mahdi Khazaei,
Volume 21, Issue 63 (12-2021)
Abstract
This study investigates the subtropical anticyclones and summer monsoons of the north hemisphere in the 500 hPa level, effective on Iran in a 38-year period (1975-2012). For this purpose, the data of geopotential heights of 500 hPa at 12 UTC with a spatial resolution of 2 by 2 degrees of the (NCEP/NCAR) were used. Results show that three independent patterns (Azores anticyclone, Saudi anticyclone and North West Africa anticyclone) and four combinatory patterns derived from the independent patterns have controlled the atmosphere of 500 hPa level of Iran. In most cases, the maximum in geopotential heights in above-mentioned anticyclone centers reach to more than 5920 geopotential meters, but often the tongue of these anticyclones control the atmosphere of 500 hPa levels of Iran with the geopotential height of 5880 to 5900 meters. In contrast, at this pressure level, the large-scale monsoon system is very weak and the maximum geopotential height of this system is about 5840 meters. The extent and intensity of the monsoon system has been reduced so that its tongues do not affect the 500 hPa level of Iran at any time. Given that the main factor in the development of large-scale monsoon system is the surface heating (bottom-up formation) and the main factor in the development of subtropical anticyclone is descending of atmospheric dynamics, the main reason for the development of summertime subtropical dynamic anticyclone should be a very strong and unit agent, something other than the summer monsoons.
Seyed Hossein Mir Mousavi, Masoud Jalali, Enayet Asadolahi,
Volume 21, Issue 63 (12-2021)
Abstract
In this research, coding the rainfalls, prepares daily 45 stations with the statistical period of 20 years to zero and one codes to realize the daily dry periods in west and north west of the country and then, by establishing the main condition of occurrence of code one for 30 stations, we extracted the dry 4 to 10-day frequencies. And the results gained of considering the atmospheric weathering, shows that the most clear rotational pattern in sea level is related to Siberia-Europe high-pressure panels and sometimes both of them that increase the rotation on the region and also, the local high-pressure reinforcement and there is a high altitude in atmospheric middle level which is derived from sample patterns and is placed on the studied region and these sample patterns are from omega, bi-polar and rex models that they are on Russia and Scandinavian countries with some changes. The 500 level TAVA and omega shows well that in most regions, the air course, has decreasing case and so, we can result that placement of a high altitude in atmospheric middle and upper level on the high-pressures of the earth, causes the weather stability and lack of rainfall and as a result, the stability and durability of these conditions for several days, is related to sample patterns.
