Climatology
Seyed Hossein Mirmousavi; Zahara Taran
Abstract
Introduction
Dust is one of the most common climatic phenomena in arid and semi-arid regions of the world The phenomenon of dust is a natural occurrence and occurs in areas with vast areas of arid and desert areas, Lack vegetation and other surface coatings. Due to its presence in the arid and semi-arid ...
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Introduction
Dust is one of the most common climatic phenomena in arid and semi-arid regions of the world The phenomenon of dust is a natural occurrence and occurs in areas with vast areas of arid and desert areas, Lack vegetation and other surface coatings. Due to its presence in the arid and semi-arid belt of the world, Iran is constantly exposed to local and synoptic dust and dust systems. In recent years, the phenomenon of dust in the Middle East has been increasing, Because it is one of the five regions of the world that has the highest dust production . Long periods of drought and inappropriate interventions in nature can increase the likelihood of this phenomenon.
In recent years, the trend of dust events in the west and south of Iran, especially in the spring and summer, has increased dramatically .This phenomenon is affected by certain atmospheric conditions and its distribution can affect the temperature, temperature, precipitation and atmospheric circulation conditions of the area during the months of the year.
Materials and methods
In this study, data of 56 years old (during 1961-2016) precipitation, temperature and dust on daily scale from 30 synoptic stations in the west and southwest of Iran were obtained from the country's meteorological organization. In line with this study, MATLAB, ArcGIS and SURFER softwares have been used. In order to analyze the information, recognition of fluctuations and the relationship between dust, temperature and precipitation have been used.
Results and discussion
Recognition of fluctuations and the relationship between dust, temperature and precipitation are investigated using regression, spectral analysis and Pearson correlation coefficient. Then it is represented by trend maps, cycles, and correlation tables. The results for the West and Southwest of Iran have been obtained and explained in detail.
Conclusion
The study of the spatial distribution of the trend shows that most of the stations studied in the dust and rainfall have an increasing trend and have been in a decreasing trend temperature. Spectral analysis of dust, dry days, and temperature showed that short-cycle cycles in addition to the most frequent distribution, showed a higher probability of occurrence than long-term periods. In most of the stations studied, the correlation of dust with temperature and dry days has a positive and direct, relationship with the rainfall has a negative and inverse relationship. The local mororan analysis for the spatial autocorrelation of dust with dry days in the western, northwest, northern and parts of the east of the study area has shown a high value cluster pattern (positive spatial autocorrelation). The spatial autocorrelation of dust with precipitation in the northeastern, eastern, and small parts of the southeast and west of the study area has a high cluster pattern (positive spatial autocorrelation). The spatial autocorrelation of dust with temperature in the eastern, western, and small parts of the south of the range has a high cluster pattern (positive spatial autocorrelation).
Climatology
Mohammad Hosein Gholizadeh; Samira Hamidi
Abstract
Introduction The consequences of climate change, changes in precipitation characters, including the amount, time and it’s duration are expected. Considering that the rain provides the water resources on the planet, change in regime, amount and duration of rainfall, caused a disturbance in the ecosystem ...
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Introduction The consequences of climate change, changes in precipitation characters, including the amount, time and it’s duration are expected. Considering that the rain provides the water resources on the planet, change in regime, amount and duration of rainfall, caused a disturbance in the ecosystem of the Earth. It also affects the environmental conditions. Kurdistan province has an agricultural economy, thus variation in the rainfall duration can affect agricultural activity and other activities. To achieve success in the environmental management planning and efficient use of water resources over an area, it is essential to have information about rainfall variation. An important parameter of atmospher is precipitation.It has a lot of changes over the time and space. It is a basic element in the formation of the activities and prospects of the environment. Several studies have done by researchers on the properties of precipitation in the different regions of the world and also in Iran. In general, precipitation showed a negative trend in many regions (Gorgio,2002: 675). For example, an assessment of summer rainfall in eastern China showed a positive and a negative trend in the north (Gemmer et al, 2004: 39; Gong et al, 2004: 771).Annual rainfall has decreased in southern parts of Italy and the decrease in winter precipitation was larger (Marco et al, 2004: 907). An increase in summer rainfall, especially, in June and July has been reported in the Yangtze River basin (Tong et al, 2007: 1016). A decrease in winter rainfall and an increas for other seasons has been showed in Turkey (Kahya and Partal, 2007: 43). Evaluation of maximum daily rainfall at the global scale showed an increasing trend in rainfall (Sethwestra et al. 2013: 3904). Negative anomalies of precipitation was reported for the most stations in southern west Ethiopia (Girma et al. 2016: 3037). Based on Iran's annual rainfall, positive and negative trends in annual rainfall have been showed (Asgari and Rahimzadeh, 2006: 67). A decrease in rainfall, especially in the decade of 1995-2005 revealed in Iran using annual rainfall (Asakereh and Razmi,2012: 159). Assessment of changes in seasonal patterns of rainfall in Hamedan, showed that the beginning of the rain tend to the summer and the end of winter (Movahedi et al.,2013: 23). The results of precipitation extreme indices on Iran showed a positive trend in the west and the south west and a negative trend in the north (Masoodian and Darand, 2013: 239). Methodology For this study, the daily precipitation obseravtions obtained from synoptic stations in Kurdistan province during 01.01.1989 to 31.12.2014 were anlayzed. A database with dimensions of 9526 * 8 was created. The time was set on rows (9526 days) and the rainfall was set on columns. Homogeneous and heterogeneous monthly rainfall data were assessed by apply cumulative deviations test and Vercelli maximum of likness. Mann-Kendall approach was implemented to extraxt the trend at the significant level of 90%, 95%, and 99 %. The significant differences in the mean of time series data before and after a mutation year by Mann-Whitney test were evaluated. The statistical calculations were done in the Matlab software. Results and Discussion The results showed that during the study period, duration of rainfall for autumn, winter and spring, in most of the stations, has been reduced. The results indicated that the rainfall duration for summer showes an increases in rainfall.Which is in line with the result of many previous studies.The reduction in the rainfall in the rainy season and an increase in rainfall in summer were obsorved. As a result the duration rainfall also has been changed. Annual rainfall has decreased in southern Italy and decrease in precipitation in winter is more (Marco et al, 2004: 907). Movahedi et al. 2013, By studying the seasonal rainfall in Hamadan, They found that the rainfall began to ward the winter and their end to the summer have changed. Conclusion Evaluation of duration time series of rainfall over different months of the year showed that in the rainy months of autumn, winter and spring rainfall duration has decreased. For example, Baneh station showed a decline of 0.3 day in December, and Marivan showed a decline of 0.6 day in January. The average rate of decline in rainfall duration in March for the Qorveh station was 0.4 day per decade. In addition, a decline in spring rainfall duration was observed as well. Bijar station showed a decline of 0.2 day in May. However the rainfall duration in summer showed an increase. For example, Zarinah station obtained an increase of 0.2 day per decade in August.
Climatology
Mohammad Reza Azizzadeyya Varzegan; khadijeh javan
Volume 23, Issue 70 , March 2020, , Pages 227-246
Abstract
One of the most important effects of climate change is increasing in extreme climate events. Change in the frequency or intensity of extreme events can have significant impacts on natural environments and human societies so their analysis is very important. The aim of this study is to identify the trend ...
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One of the most important effects of climate change is increasing in extreme climate events. Change in the frequency or intensity of extreme events can have significant impacts on natural environments and human societies so their analysis is very important. The aim of this study is to identify the trend of precipitation extremes in Lake Urmia basin and to investigate their relation with Teleconnection patterns. For this purpose, daily precipitation data of 7 synoptic stations in the basin during 1987-2014 was used. 11 extreme precipitation indices were extracted using the RClimDex and their trends were calculated by non-parametric Mann-Kendall test. Then the relationship between these indices with Teleconnection patterns was determined by the Pearson correlation coefficient. The results of time series analysis showed that all extreme precipitation indices in Lake Urmia basin have decreasing trend exept consecutive dry days (CDD). The spatial distribution of trend in extreme indices showed almost all indices have a significant trend at the 5% significance level in basin. There is no significant trend in consecutive dry days (CDD). The changes in extreme precipitation could be affected by the El Niño-Southern Oscillation (ENSO), Southern Oscillation Index (SOI), East Pacific-North Pacific (EP-NP), Madden and Julian Oscillation (MJO) and Pacific Decadal Oscillation (PDO).
Climatology
Mohama Raheimi; Mohamad Reza Yazdani; Moslem Asadi; Nafise Pegahfar; Mohammd Taleb Haydari
Abstract
Abstract The aim of this study is to investigate possible deviations from normal for Some climatic parameters in the Kurdestan. Calculation and analysis is done based on variables such as temperature, precipitation, humidity and maximum wind speed. Period examined in this study is a 30-year period between ...
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Abstract The aim of this study is to investigate possible deviations from normal for Some climatic parameters in the Kurdestan. Calculation and analysis is done based on variables such as temperature, precipitation, humidity and maximum wind speed. Period examined in this study is a 30-year period between 1983 and 2012 and is included Sanandaj, Saghez, Ghorveh, Marivan, Zarina Stations and Bijar At first, will identify data changes using the Mann-Kendall test. Then Characterized type and time of change. At the end Pearson correlation test was applied between variables. The results of data analysis indicate that start time of more changes is sudden and includes both the trend and fluctuation. Also, the results of the pearson correlation test suggests in most stations, there is positive significant correlation between rainfall and humidity and also negative significant correlation between temperature and humidity parameters.
All other Geographic fields of studies , Interdisciplinary
yagob Dinpazhouh
Abstract
The aim of this study is trend analysis of streamflows of east Azerbaijan using the non-parametric methods. For this purpose the information of consentration of water quality ions (Ca, Mg, Cl, Na, HCo3, pH, So4, TDS, EC, SAR, Total Cations, Total Anions and Na%) of ten hydrometric stations (1983-2008) ...
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The aim of this study is trend analysis of streamflows of east Azerbaijan using the non-parametric methods. For this purpose the information of consentration of water quality ions (Ca, Mg, Cl, Na, HCo3, pH, So4, TDS, EC, SAR, Total Cations, Total Anions and Na%) of ten hydrometric stations (1983-2008) were used. To test trends the Mann-Kendal scheme after removing all significant autocorrelation effects from the data were used. To estimate trend line slope the non-parametric Sen´s estimator method was used. Results showed that trends of positive ions and EC were upward for most of the stations. Those stations which had negative trend in streamflow also exhibited positive trend in concentration of chemical elements of surface water. Furthermore, investigation of streamflow water quality using the Wilcox on method showed that the quality of water declined comparing the last decades. The reason of such declination attributed to the decreasing trend of streamflow and conveying pollutant materials into the rivers.
Climatology
Peyman Mahmoudi; Mahmood Khosravi; Seyed Abolfazl Masoodian; Bahlol Alijani
Volume 19, Issue 54 , February 2016, , Pages 303-327
Abstract
To identify and detect the frequency variation trend of Iran’s pervasive and semi-pervasive frost days in the current research, minimal daily temperature data of 663 Iranian climatology and synoptic stations were acquired from Iran Meteorology Organization during the time interval between 1962 ...
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To identify and detect the frequency variation trend of Iran’s pervasive and semi-pervasive frost days in the current research, minimal daily temperature data of 663 Iranian climatology and synoptic stations were acquired from Iran Meteorology Organization during the time interval between 1962 and 2004 for October to April months. Following data acquisition, Iran’s isothermal maps for each day starting from 1.1.1962 until 31.12.2004 (9116 days) were prepared using Kirging interpolation technique in order to construct the database of the county’s minimal temperature. In the next step, frosts were classified in three types based on a spatial principle: pervasive frosts (simultaneous occurrence in more than 65% of Iran’s surface area), semi-pervasive frosts (simultaneous occurrence in 25% - 65% of Iran’s surface area), and local frosts (simultaneous occurrence in less than 25% of Iran’s surface area). Then, frequency of pervasive and semi-pervasive frost days were analyzed in three scales including monthly, seasonal, and yearly using two estimation techniques of slope SENSE and linear regression.
Results indicated that frequency of pervasive frosts in Iran held a statistically significant decreasing trend in December and January months, during winter, and also, in annual basis. But, for semi-pervasive frost days, it was observed that variation was significant only in January having a positive trend. It signifies that number of days with semi-pervasive frost increased during the 43 years under study. Therefore, number of semi-pervasive frost occurrences increased while number of pervasive frost occurrences decreased in January. The same rule holds for other scales i.e. monthly, seasonal, and yearly basis.
Climatology
nahideh Jahedi; mohammadali Ghorbani
Volume 19, Issue 52 , June 2015, , Pages 63-63
Abstract
Being aware of decreasing or increasing trend of precipitation and discharge in watersheds has very important role in water resources management and the subjects relating to water engineering. In this study, the trend of precipitation and discharge at Qara-su River Basin in Ardebil has been studied in ...
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Being aware of decreasing or increasing trend of precipitation and discharge in watersheds has very important role in water resources management and the subjects relating to water engineering. In this study, the trend of precipitation and discharge at Qara-su River Basin in Ardebil has been studied in monthly, seasonal and annual timescales over the period from 1351 to 1382. For investigation of the existence or absence of a trend, Mann-Kendall test was used by detecting effects of all auto correlations coefficients, and Sen’s estimator was used at different significant level to evaluate the magnitude of the test. The results of the calculated values for precipitation and discharge data set indicated that the trend of the Qara-su River discharge was decreasing for both stations in annual timescale. Also, decreasing trend of discharge dataset was found for seasonal timescale in spring, autumn and winter in which significant trend belonged to winter season. Maximum value of decrease for discharge is for Doustbiglo station in spring (-0.62 m^3/s), and the minimum value of decrease for discharge in summer for this station, too. Furthermore, there was not significant trend for precipitation dataset in monthly, seasonal, and annual timescales.
Climatology
Rasool Mirabbasi Najafabadi; yaghoob Dinpashoh
Volume 19, Issue 52 , June 2015, , Pages 277-301
Abstract
The aim of this study is the analysis of surface wind speed in monthly and annual times scales in Iran using four different versions of the Mann-Kendall method: i) conventional Mann-Kendall method (MK1); ii) Mann-Kendall method following removing the effect of significant lag-1 auto-correlation (MK2); ...
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The aim of this study is the analysis of surface wind speed in monthly and annual times scales in Iran using four different versions of the Mann-Kendall method: i) conventional Mann-Kendall method (MK1); ii) Mann-Kendall method following removing the effect of significant lag-1 auto-correlation (MK2); iii) Mann-Kendall method after the removing the effect of all significant auto-correlation coefficients (MK3); and Mann-Kendall method with considering the Hurst coefficient (MK4). Data used here are wind speed records in both monthly and annual time scales in the period of 1966-2005. For this purpose, 22 stations were selected across Iran’s area. Nonparametric Sen’s method was used for estimation of wind trend line slope. Results showed that although a combination of positive and negative trends observed both in monthly and annual time scales, however, the number of stations having the negative trends were more than that of the positive trends. In the annual time scale, the strongest negative trend line slope was -0.074 ms-1y-1 belonging to Fasa station, and the strongest positive trend line slope was 0.141 ms-1y-1 belonging to Zabol station. In monthly time scale, the strongest negative trend line slope was -0.1 ms-1y-1 observed in Fasa station and the the strongest positive trend line slope was 0.18 ms-1y-1 observed in Zabol station. Results showed that the median of the trend line slopes for all months (except February and November) was negative. Therefore, in general, it can be concluded that in the most of stations in Iran wind speed trend in all months (except February and November) was negative.
Yagoub Dinpazhooh; Faege Niazi; Hamed Mofid
Volume 19, Issue 51 , April 2015, , Pages 145-169
Abstract
The aim of this study is trend analysis of meteorological parameter including mean wind speed, min, max and mean air temperature, difference between the min and max temperature, pan evaporation, average relative humidity, sunshine hours, total precipitation, the number of days with precipitation more ...
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The aim of this study is trend analysis of meteorological parameter including mean wind speed, min, max and mean air temperature, difference between the min and max temperature, pan evaporation, average relative humidity, sunshine hours, total precipitation, the number of days with precipitation more than 1, 5 and 10 mm, the number of days with dust, number of the days with snow and the number of days with visibility less than 2Km, degree days based on 18 and 21 oC at Tabriz station during 1970-2005 in three time scales, monthly, seasonal and annually using the non-parametric Mann-Kendall (MK) method. Trend analysis was conducted using two methods, which are conventional MK (for series having insignificant autocorrelation coefficients) and modified MK (for other series) in three significant levels, 1%, 5% and 10%. Trend slopes were calculated using Sen’s estimator. Results showed that in annual time scale, pan evaporation, min, max and mean temperature and degree days based on 18 and 210C have significant increasing trends at 5% level but precipitation, number of the days with precipitation more than 1 and 5 mm and degree days based on 180C have decreasing trend (at 5% level). Other parameters did not show significant trend in annual time scale. Trend slope of annual precipitation was -2.28 mm/year and trend slopes of all three elements, average, max and min temperature were 0.06 0C/year. Observed trends in studying parameters indicate climate change in Tabriz.
Tahere Jalali Ansaroodi; Aliakbar Rasouli; Fatemeh Sarafrouzeh; Marzieh Esmaeilpour
Volume 19, Issue 51 , April 2015, , Pages 171-191
Abstract
In this paper, Nisan rainfalls of East Azerbaijan Province in the period of 1980 to 2009 were investigated. Initially changes of Nisan rainfalls trend were analyzed using the non-parametric Mann-Kendall test and Sen's estimator slope that are the most common methods of non-parametric tests. In order ...
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In this paper, Nisan rainfalls of East Azerbaijan Province in the period of 1980 to 2009 were investigated. Initially changes of Nisan rainfalls trend were analyzed using the non-parametric Mann-Kendall test and Sen's estimator slope that are the most common methods of non-parametric tests. In order to predict changes of Nisan rainfalls in the next years, ARMA time series model was used. The results indicated that according to non-parametric tests in the study period, time series of Nisan rainfalls have no trend in none of the stations except Azarshahr. After reviewing of different patterns of ARMA model, proportional model for each station was selected based on Akaike information criterion (ACI) and, the Nisan rainfalls in East Azerbaijan Province were predicted for next 10 years. The accuracy of models was confirmed based on normality tests for residuals of the model and RMSE
Hossein Asakareh; Ali Bayat
Volume 17, Issue 45 , November 2013, , Pages 121-142
Abstract
Principal Component Analysis (PCA) is an optimum mathematical method to decrease variables into some limited components in order to justify the highest variance of primary variables. In this study some statistical characteristics of annual precipitation of Zanjan city including sum of annual precipitation, ...
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Principal Component Analysis (PCA) is an optimum mathematical method to decrease variables into some limited components in order to justify the highest variance of primary variables. In this study some statistical characteristics of annual precipitation of Zanjan city including sum of annual precipitation, number of rainy days, extreme daily precipitation in a year, the ratio of extreme precipitation to the sum of annual precipitation and some characteristics such as Standard Deviation (SD), Skewness (Sk), Kurtosis (Ku), Absolute Mean Deviation (AMD) and Mean Absolute Interannual Variability (MAIV) were was calculated from monthly precipitation for each year, and were introduced principal component analysis technique. The results show that 95% percent of annual precipitation variations can be explained through 4 components. The first component which indicates the highest data variance (42.6%), represents annual precipitation and absolute variability indices including SD, AMD and MAIV. The second component represents the shape of frequency distribution indices (Sk, Ku), the third component represents extreme precipitations and finally the fourth component represents the number of rainy days. The analysis of the trend of components scores show that first and fourth components scores have a significant decreasing and increasing trend, respectively. Round a lines show a precipitation decrease during the period under study from one hand and having uniform temporal distribution on the other hand.
Majid Rezayee Banafshe; Fatemeh Sarafroozeh; Tahereh Jalali
Volume 16, Issue 38 , February 2012, , Pages 43-74
Abstract
For investigation of variability of climatic elements of UrmiaLake basin, maximum and minimum daily temperature and daily precipitation data over period of 1984-2006 were analyzed. In this paper, 6 indices for analysis of temperature variability and 8 indices for analysis of precipitation variability ...
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For investigation of variability of climatic elements of UrmiaLake basin, maximum and minimum daily temperature and daily precipitation data over period of 1984-2006 were analyzed. In this paper, 6 indices for analysis of temperature variability and 8 indices for analysis of precipitation variability were used. The trends of these indices were specified using least square approach and for identifying their significance nonparametric, Man-Kendal test was used. Results indicate that over the study period climatic conditions have changed. The number of summer days and warm nights significantly increased with the number of cold days and cold nights reduction. Also total annual precipitation, number of precipitation days (above 2 mm) and number of heavy precipitation days (equal or above 10 mm) have significant reduction. Moreover, in the study period the number of consecutive wet days has significant reduction, but increasing of consecutive dry days is not significant.
