Showing 47 results for Iran
A. Taghavi, Gh. Tahmasbi, A. A. Talebi, A. Zarnegar, A. Monfared, H. Nazarian,
Volume 12, Issue 45 (10-2008)
Abstract
The species diversity of bumblebees was investigated in two provinces, Tehran (Fasham, Zayegan) and Qazvin (Alamut, Wikan) in central Alborz during 2005-2006. Three casts of queen, worker and male bumblebees were collected during spring and summer in six dates in the two mentioned regions. Sampling of adult bees in Wikan was done from 26 July 2006 until 19 September 2006, and in Zayegan from 24 May 2006 to 17 September 2006. In sum, eleven species were collected of which eight species were common in the two regions. Data of different species casts at two regions were analyzed by Excel ver. 6 and Ecological Methodology ver. 6. 1. 2 soft wares. Species diversity of two regions was determined and compared with three indices of Simpson, Shannon-Weiner and Brillion, and evenness was calculated with indices of Simpson, Camargo and Esmit-Willson. Species richness of two regions was compared in research. The obtained results showed species diversity, evenness and species richness were more observable in Wikan compared with Zayegan. Consequently, Wikan in comparison with Zayegan was more sustainable. Similarity of two regions was 0/46, showing many differences in terms of the kinds. Also, there were 8 similar species in the two areas.
A Vaezi, H Bahrami, H Sadeghi, M Mahdian,
Volume 13, Issue 49 (10-2009)
Abstract
Proper evaluation of soil erodibility factor is very important in assessment of soil erosion. In this study, soil erodibility factor (K) was assessed in a zone, 900 km2 in area in Hashtrood, located in a semi-arid region in north west of Iran. Soil erodibility factor was measured at the unit plots under natural rainfall events in 36 different lands in the study area from March 2005 to March 2007. Results indicated that the measured soil erodibility factor K is on average 8.77 times lower than the nomograph-based values in the study area. To achieve a new nomograph, correlation between measured soil erodibility and soil physicochemical properties was studied. Based on the results, soil erodibility factor negatively correlated with coarse sand, clay, organic matter, lime, aggregate stability and permeability, while its correlation with very fine sand and silt was positive. Results of principal component analysis of soil properties and multi-regression analysis showed that the soil erodibility factor is significantly (R2 = 0.92, P < 0.001) related to soil permeability, aggregate stability, lime and coarse sand. A new nomograph with a R2 of 92% was developed based on these properties to easily estimate soil erodibility factor in the study area. The soil erodibility factor can be reliably estimated using the nomograph in all regions with the soil and rain properties similar to those in the study area.
Sh Ghergherechi, F Khormali, Sh Ayoubi,
Volume 14, Issue 51 (4-2010)
Abstract
Gypsum is the most common sulfate mineral in soils of arid and semi-arid regions. Two hundred million hectares of the earth’s surface and about 28 million hectares of Iranian arid soils are covered by gypsiferous soils. The studied soils consist of alluvial plane and eolian plains in northern Iran. Soils were classified as Haplocambids, Aquisalids and Endoaquepts. In this study, genesis, formation and development of gypsum in soils were investigated. Study area includes different geomorphic surfaces from the upper watershed to alluvial plains. Gypsum crystals without considering their size, shape, arrangement are determined as pedogenic. In the weakly-developed horizons, in aridic moisture regimes, formation of euhedral pedogenic gypsum crystals and incomplete infilling of voids was dominant. In the well-developed soils, in xeric moisture regime, gypsum crystals are oriented and the perpendicular in arrangement of crystals along pores is dominants. Gypsum crystals occur in different shapes such as lenticular, tabular, and rosette-like and fan arrangement. Origin of gypsum in weakly-developed soils was weathered gypsiferous marls in upper Atrak basin. The source of gypsum in the soils with shallow ground water is high content of sulfate dissolved in soil solutions. In horizons affected by fluctuation of ground water contaning sulphur, euhedral tabular shape is dominant. In well-developed soils, based on Snowball morphology, gypsum is classified as stage II nodule. Results showed that there is no relationship between formation of the snowball morphology, b-fabric and kind of diagnostic horizons (A, B and C).
M Bashiri Seghale, S.h.r Sadeghi, A.s Rangavar ,
Volume 14, Issue 52 (7-2010)
Abstract
Erosion plots are basically used for studying erosion processes and many related problems. However, the possibility to extend the results of experimental plots to surrounding watersheds is rarely taken into account. In the present study, an attempt was made to study on the accuracy of soil erosion plots in estimation of runoff and sediment yield from small watersheds. Towards this attempt, 12 experimental plots with length of 2, 5, 10, 15, 20 and 25 meter were installed on two north and south facing slopes in Sanganeh watershed, northeastern Razavi Khorasan Province with an area of ca. 1 ha. The performance of the plots in estimation of runoff and sediment was controlled by data collected at the main outlet associated with 12 storm events occurred during November 2006 to June 2007. The results showed that the accuracy of plot estimates on sediment and runoff improved while the plot length increased. The optimal length for estimation of sediment and runoff parameters was found to be equal to average slope length and more than 20m.
A. H. Gharehsheikhloo , M. R. Vahabi , H. R. Karimzadeh ,
Volume 14, Issue 53 (10-2010)
Abstract
In order to classify and determine the plant communities in Karkas mountainsides, central Iran, quantitative data of 46 environmental characteristics including climate (12 characteristics), soil (26 characteristics), geology and physiology (8 characteristics), were analyzed based on partial Euclidean distance indicator using minimum variation method. The results showed the clustered separation of studied sites at 68% similarity level with three different growth places. Of these 46 factors, 24 factors (8 climate characteristics and 16 soil characteristics) were effective in this classification at 95% certainty level. Only 24 of these 46 factors were effective in this classification at 95% certainty level. These 24 effective factors were divided into 8 climate and 16 soil characteristics. In another classification, combinational percentage index of 17 plant species were investigated as an effective factor in separating growth place and determining the plant communities. Result of cluster classification indicated that the studied sites cold be classified to 3 habitats.
M. J. Nazemosadat, H. Ghaedamini Asadabadi,
Volume 15, Issue 55 (4-2011)
Abstract
The Madden Julian oscillation (MJO) is known as the primary mode of large-scale inter-seasonal variability in tropical regions, affectimg equatorial and sub-tropical climates. This study investigated the effects of the MJO on the occurrence of wet and dry spells in Fars province, central southern part of Iran, during November-April. Monthly precipitation data of nine stations spread over various parts of the province was analyzed during 1979-2005. Using two well-known MJO indices: MK and WH, the positive and negative phases of the MJO phases (enhanced and suppressed convective activity over the equatorial Indonesian region, respectively) were identified for monthly and seasonal scales. Precipitation-MJO composites were then constructed for the opposite phases. It was shown that for all the considered stations, seasonal precipitation during negative MJO phase was significantly greater (from about 2.5 to 6.0 folds) than the corresponding values during the positive phase. Moreover, the applied statistical tests proved that the frequency of wet or dry events was related to the prevalence of negative or positive MJO phase, respectively. As the positive MJO phase was engulfed, the probability of dry events varied from 60% to 84%. On the other hand, the probability of wet events was found to vary from 60% to 76% during the MJO negative phase.
M. R. Shoaibi Nobariyan, H. Torabi Golsefidi, Sabereh Darbandi,
Volume 18, Issue 70 (3-2015)
Abstract
CEC of the soil is the exchange sites of organic and inorganic soil colloids. Modeling and Estimation of CEC is a useful indicator for fertility. The new alternative approaches for estimating CEC are indirect methods based on intelligent models. In this research in order to estimate CEC, 485 soil samples were prepared from two regions, chaparsar (Mazandaran in northern Iran) and Bostanabad (North of West Azarbaijan, Iran).In this paper introduces the application of genetic programming. Input parameters that are percent Clay, Organic Carbon and Silt, evaluate using genetic programming, neural network and Neural Inference Systems-Fuzzy models. The results indicate a good ability to intelligent models for CEC Estimation According to indices used in this study. Genetic programming model with a root mean square error of 1.78 and coefficient of determination 0.95 compared to other models have been more efficient and is able to provide satisfactory results, Also are the explicit solutions that reflect the relationship between input an output variable, was presented based on genetic programming. This preferred the genetic programming model adds the other models. Stepwise regression analysis to determine the contribution of each of the parameters indicated in the CEC that organic materials having Most coefficient of variation of 84% is justified CEC and clay and silt, respectively, with a correlation coefficient of 10% and 6% respectively.
S. Azadi, S. Soltani Kopaei, M. Faramarzi, A. Soltani Tudeshki, S. Pourmanafi,
Volume 19, Issue 72 (8-2015)
Abstract
The Palmer Drought Severity Index (PDSI), which uses hydrometeorological variables to solve a simple water balance equation in the soil and considers the drought or wet conditions as dynamic phenomena, is used for the assessment of drought conditions in many parts of the world. The main goal of this study was to assess the PDSI based on its original assumptions, its regionalized status, using the outputs of already calibrated and validated SWAT model in central regions of Iran. The PDSI was assessed through five methods: 1) original Palmer Index without calibration in which the climate coefficients and the severity equation were derived for Kansas and central Iowa 2) original Palmer Index in which the coefficients of severity equations were adjusted 3) the Palmer Index with the calibration of equations in central areas of Iran 4) the Palmer Index using the soil moisture and potential evapotranspiration from SWAT model and 5) the Palmer Index using the soil moisture, potential evapotranspiration and runoff from SWAT model. The evaluation was conducted for 17 major basins covering the entire country with a monthly time step for the period 1990-2002. Then, using all five methods, the severity of the drought for 160 sub basins located in central Iran was calculated and evaluated. The results of this study indicated that method 4 provides more acceptable results. Also, the results of this research showed these methods clearly demonstrated (1992) as the wettest year and (2001) as the driest year. The approach used in this study is applicable to regional calibration of Palmer Index and the outputs of other hydrological models.
. A. A. Sabziparvar1, S. Ebrahimzadeh2, M. Khodamoradpour3,
Volume 21, Issue 4 (2-2018)
Abstract
The most important factor in determining crop water requirement is estimation of evapotranspiration (ET). Majority of the methodsestimate ET apply series of relatively complex formula,which is then used to determine crop evapotranspiration (ETc). The parameters used in aforesaid methods are: Solar radiation, wind speed, humidity, etc. Unfortunately, in Iran and many countries, long-term records of these parameters are not readily available. The purpose of this study is to calculate the Selianinov Hydrothermic Index that merely requires daily temperature and precipitation data in order to determine correlation coefficients (r) versus ET and Crop Water Requirement (CWR) of some agricultural crops of Iran. First, the Selianinov index is calculated from daily precipitation and temperature during the growth season. Further, the results are correlated against both ETc and CWR. The model results indicate inverse (negative) strong exponential and polynomial relations between the dependent and independent variables. Coefficient of determination (R2) for polynomial equations (on average 0.84) in all crops was better than exponential equations (on average 0.72). Correlation between Selianinov index and CWR indicates that coefficient of determination in both equations was close together (0.83 for polynomial equations and 0.82 for exponential equations).
A. Vali, F. Roustaei,
Volume 21, Issue 4 (2-2018)
Abstract
Wind erosion is the most important geomorphic process and the main cause of the landscape change in arid and semi-arid areas. This paper focuses on the Dust Storm Index (DSI) with the aim of monitoring wind erosion in Central Iran using meteorology data. The trend of standardized DSI and its three factors which are sever dust storm, moderate dust storm and local dust events were studied using Man-Kendal non-parametric test. It was found that wind erosion is accelerating in recent years. Compared to primary 20 years (1965-1985) DSI rate has been three times more than 30 years ago (1985-2014). The central and southern parts of Central Iran show the highest severity of wind erosion and the severity of DSI decreases by approaching the north. Therefore, considering the sensitivity of these areas, in addition to taking into account prevention programs, they should also be considered in regeneration and control programs.
F. Amiri, T. Tabatabaie, S. Valipour,
Volume 22, Issue 1 (6-2018)
Abstract
The purpose of this paper was to assess the groundwater quality near Qaemshahr landfill site using the Iran Water Quality Index for Groundwater Resources-Conventional Parameters (IRWQIGC). In this study, samples were taken from 11 wells with three replications in February 2015 and water quality was assessed by evaluating nitrate, fecal coliform, electrical conductivity (EC), pH, total hardness, sodium absorption ratio, biological oxygen demand, phosphate, chemical oxygen demand, and dissolved oxygen parameters with the standard measuring methods; also, the quality of ground water was determined using the IRWQIGC. Statistical description of the parameters was performed using the SPSS software. Spatial extension mapping parameters were drawn using geostatistics extension with the ArcGIS software. The results of water quality assessment revealed that 0.15% of the area was classified as bad, 98.85% as relatively poor, and 1% as middle in terms of quality. The results of spatial dispersion also revealed that water quality from the South to the North and North East was reduced. Evaluating the changes in water quality near landfill sites showed that 2149.56 square meters of total area had a relatively poor potential for the region’s groundwater recharge.
S. Pourhossein, S. Soltani,
Volume 22, Issue 2 (9-2018)
Abstract
Bhalme & Mooley Drought index is one of common indices used in drought studies. Due to the fact that drought indices can have different sensitivities to different region conditions and the length of data recorded, 62 synoptic and climatological stations were selected within a homogonous region to study this index advantages and to assess the effect of climate, precipitation regime, and data record on the index. The best results were found for the humid climate. Also, this index had acceptable results for semi- mediterranean regimes regarding all different time scales,; however the situation was different for Mediterranean regimes, showing the best results for the time scales simultaneous with the precipitation period. From the data record point of view, the best results were estimated during the first 31- years of the common period which has correspondence with the results of the 36-year period.
S. Jahanbakhsh Asl, B. Sari Saraf, T. Raziei, A. Parandeh Khouzani,
Volume 23, Issue 4 (12-2019)
Abstract
In this study, the temporal and spatial variation of snow depth over the mountainous region of Zagros, in the western Iran, for the period 1979–2010 was investigated for the cold season when the probability of snow occurrences was high. For this purpose, daily gridded snow depth data relative to Era-Interim/land were retrieved from the European Centre for Medium-Range Weather Forecasts (ECMWF) and used for spatiotemporal analysis of snow in the region. Furthermore, monthly maximum, minimum and mean air temperature relative to the weather stations distributed over the region were also used to investigate the relationship between snow depth and air temperature variability in the region. In each grid point, the rate of temporal changes in the snow depth was estimated using the Sen’s slope estimator, while the modified Mann-Kendall Test was applied to assess if the change identified was statistically significant. The results showed that in almost all of the studied months, especially February and March, the snow depth was significantly reduced in the region, which was statistically significant at 5% significant level. Unlike the observed statistically significant decreasing trend in the depth snow in the region, a significant increase in the maximum, minimum and average temperature was observed for all the studied months and the stations. The result suggested that the observed decrease in the snow depth in the region was related to the increasing trend in the temperature during the study period, which could be attributed to the global warming and climate change.
H. Fathizad, M. Tavakoli, M. A. Hakimzadeh Ardakani, R. Taghizadehmehrjardi, H. Sodaiezadeh,
Volume 24, Issue 4 (2-2021)
Abstract
The purpose of this research was to investigate the trend of annual changes in Yazd station's meteorological parameters including minimum and maximum average daily temperature and average daily precipitation (1961-2005), as well as the predicted annual mean of these parameters in the three upcoming thirty years of the 2040s, 2070s and 2100s, by the SDSM model, under RCP2.6, RCP4.5, RCP8.5, A2, and B2 scenarios. Accordingly, by using the coefficient of determination and the MAE, R2, RMSE indicators, we evaluated the data generated by the SDSM model in comparison with the observed data in the base period. The lowest value of R2 based on the calibration and validation of the mean values of observed and simulated SRES was obtained for precipitation (86 and 80%). In terms of the R2 evaluation index, the accuracy of the small-scaled results of the minimum and maximum average temperature values was more than that of the average precipitation; however, in terms of the MAE and RMSE evaluation indicators, the accuracy of the small-scaled results of the average precipitation was higher than that of the minimum and maximum average temperature values. Subsequently, HadCM3 large-scale climatological data was used to predict the future periods (2010-2100). The results indicated that the temperature was raised in all months and seasons and the precipitation was decreasing in most of them, thereby confirming that the climate was changing in the studied region.
F. Soroush, F. Fathian,
Volume 25, Issue 1 (5-2021)
Abstract
In the present study, the spatial and temporal changes of climate variables such as pan evaporation (Ep), temperature (T), relative humidity (RH), sunshine duration (SD), wind speed (W) and precipitation (P), as well as their relationship with altitude, were investigated. For this purpose, 68 meteorological stations with 30 years of data (1987-2016) throughout Iran on both seasonal and annual time scales were selected. Trend analysis of climate variables showed that over the past 30 years, most areas of Iran have become warmer and drier although all trends have not been significant. Investigation of the relationship between the trend slope of climate variables and altitude illustrated that there was no significant relationship between them during the study period on the annual time scale (p>0.1). However, in winter, the rate of increase in T (minimum, maximum and mean temperatures) and SD (p<0.1), as well as the rate of decrease in P (p<0.01), was significantly enhanced by increasing the altitude. The increase in mean and maximum T (p<0.1) and SD rates (p<0.001) in summer were significantly lower in the highlands than in the lowlands. In autumn, the trend slopes of minimum and mean T (p<0.05) were negatively correlated with altitude; in addition, the rates of increase in P and RH (p<0.05) in the highlands demonstrated a sharper increase. It seems, therefore, that most changes in climate variables have occurred in both autumn and winter. The results also showed that in winter, the highest rates of increase in Ts were related to the altitude of 1500-2000 m; however, the highest decrease in P belonged to the altitude of 2000-2500 m. In autumn, the highest rates of decrease in minimum and mean Ts had occurred in the altitude of 2000-2500 m; as well, he highest rate of increase in P was observed in the altitudes of both 0-500 m and 2000-2500 m.
M. Motavallizadeh Naeini, R. Modarres,
Volume 25, Issue 4 (3-2022)
Abstract
Dust storms in arid and semi-arid regions have harmful impacts on the environment, the economy, and the health of local and global communities. In this study, the frequency of annual dust events in twenty-five stations and five climatic variables including rainfall, maximum annual wind speed, average annual wind speed, maximum annual temperature, and average annual temperature in arid regions of Iran up to 2014 were used to show the effects of climatic change on dust storms. Annual correlation coefficient time series between climatic variables and dust storms were first calculated based on monthly observations. Then, the trend in climatic variables, dust storm frequency, and their correlation were assessed using the Mann-Kendal method. Results indicated that the correlation coefficients had fluctuations in time and are both significant and insignificant in different years that reach from 0.6 to 0.9 for wind speed and temperature and -0.2 to -0.6 for precipitation. This trend in correlation has the same direction with climatic variables and shows co-movement between climatic change and dust storm fluctuations in central Iran. Results also showed that wind speed and temperature have a high impact on dust storm fluctuations and rainfall reduction has an increasing effect on dust storms.
A. Shahbaee Kotenaee, H. Asakereh,
Volume 26, Issue 4 (3-2023)
Abstract
Precipitation is one of the most significant climatic parameters; its distribution and values in different areas is the result of complex linear and nonlinear relationships between atmospheric elements-climatic processes and the spatial structure of the earth's surface environment. Classification of data and placing them in small and homogeneous zones can be effective in improving the understanding of these complex relationships and their results. In the present study, zoning and analyzing the distribution of rainfall in Iran concerning environmental factors was performed using the annual precipitation data of 3423 synoptic, climatological, and gauge stations in the country during the period from 1961 to 2015 and the altitude, slope, aspect, and station density data. After standardization and preparation of the data matrix, the optimal number of clusters was determined and the data set was entered into the neural-fuzzy network model (ANFIS-FCM). The results showed that the values of R2 and MAE indices were 0.76 and 0.23, respectively which indicate the appropriate accuracy of the model. It was also found that in the four output zones of the model, environmental factors have a high impact on the spatial distribution of precipitation. In the first and third zones, the combination of high altitude and slope factors along with geographical proximity to precipitation systems has caused the average annual rainfall in these zones to be 318 and 181 mm, respectively. The mean annual rainfall has decreased to about 100 mm by the weakening of the role of environmental factors in the second and fourth clusters.
F. Fathian, M. Ghadami, Z. Dehghan,
Volume 26, Issue 4 (3-2023)
Abstract
In this research, the trend of spatial changes in extreme indices of temperature related to the health and agriculture sectors such as the number of frost days, number of summer days, number of icing days, number of tropical nights, growing season length, diurnal temperature range, cold spell duration index, and warm spell duration index were investigated for 54 synoptic stations throughout Iran for observational (1976-2005) and future (2025-2054) periods. Daily maximum and minimum temperature data of three regional climate models namely, CCSM4, MPI-ESM-MR, and NORESM1-ME from the CORDEX project under RCP4.5 and RCP8.5 scenarios were downscaled for each station using a developed multiscale bias correction method. Then, trends and changes of extreme temperature indices were investigated using Mann-Kendall and Sen’s trend line slope methods. The results indicated that the warm indices such as the number of summer days and tropical nights indices have had a positive trend at most stations in both observational and future periods. In contrast, cold indices like the number of frost days have had a decreasing trend in most stations. The results of cold and warm spell duration indices showed that most stations have had no trend for both periods. The growing season length has increased in more than 60% of stations (45% having a significant trend) mainly located in the northern, northwestern, and western regions of the country. Based on the results, it can be concluded that without considering thoughtful climate adaptation measures, some parts of the country may face health risks and limited habitability and agriculture in the future.
A. Shahbaee Kotenaee, H. Asakereh,
Volume 27, Issue 1 (5-2023)
Abstract
Precipitation is one of the main elements of the Earth's hydro-climatic cycle and its variability depends on the complex and non-linear relationships between the climate system and environmental factors. Understanding these relationships and doing environmental planning based on them is difficult. Therefore, classifying data and dividing information into homogeneous and small categories can be helpful in this regard. In the present study, an attempt was made to prepare precipitation, altitude, slope, slope direction, and station density data for 3423 synoptic, climatological, and gauge stations in Iran in the 1961-2015 years’ period. These data were entered into fuzzy (FCM), self-organizing map neural network (SOM-ANN) models and precipitation-spatial zoning. The outputs of the two models were compared in terms of accuracy and efficiency. The results obtained from the output of the models have divided the rainfall conditions of Iran into four zones concerning environmental factors. Evaluations also showed that both models had high accuracy in classifying precipitation parameters; However, the fuzzy model has a relative advantage over the neural network model in the accuracy of results.
H. Asakereh, A. Shahbaee Kotenaee,
Volume 27, Issue 2 (9-2023)
Abstract
Identifying the behavior of precipitation is one of the most important planning principles related to water resources. In this research, an attempt was made to analyze the trend of time changes in extreme rainfall profiles of the country by using the daily rainfall data of 3423 synoptic, climatology, and rain gauge stations for the period from 1970 to 2016 and by performing interpolation using the kriging method. Then, using percentile profiles (percentile less than 10, less than 25, 25 to 75, 75 to 90, and above 90) and regression analysis, changes in the frequency of member days of each of the percentile methods over time were calculated and mapped. The results showed that during the studied period, 86.6% of cells associated with days with the tenth percentile or less in the country had an increasing trend. On the other hand, the pixels associated with days with the 90th percentile and more have shown an increasing trend. Considering that the pixels with the 25th, 25th-75th percentiles (normal), and 75th percentile have shown a decreasing trend in terms of the number of days in their group, it can be concluded that the country's rainfall conditions and the days with rainfall are towards the limit values has moved and the possibility of drought or destructive floods has increased in the country.
