Showing 14 results for Trend
Zohreh Maryanji, Fatemeh Sotoudeh, Meysam Toulabi Nejad, Ziba Zarrin,
Volume 0, Issue 0 (3-1921)
Abstract
Understanding and predicting future climatic conditions and characteristics is essential because of their importance in all aspects of life. This study seeks to examine the process of modifying temperatures in the Hamedan region by using Downscaling data to predict the public circulation data and its changes. The Lars Explore Downscaling Model has been used to fine-tune the data of the General Transport Model (HADGEM2-ES) and the paired model (CMIP5) and under the three release scenarios RCP2.5, RCP4.5, and RCP8.5). Estimates of the correlation of simulated data and actual data show values of more than 0.95 for all months. P_value also showed the statistical tests of model output, acceptable values in model performance in production and simulation. As a result, the data were extracted from 2011 to 2050. Data were examined in three intervals to detect trend changes. The results show that in the optimistic scenario (RCP2.5) there is no tangible trend in the mean and minimum temperature, while in the RCP4.5 and RCP8.5 scenario there are significant trends in temperature data and accordingly increase the minimum temperature, according to the increase in the minimum temperature, according to the increase in the minimum temperature, according to the increase 1 degree in the average temperature. It shows severe climate change that, especially in the cold season, changes the type of precipitation. Also, based on the data process, the significant increase in the average annual and monthly scale temperature in all three scenarios under study will indicate the environmental crisis ahead.
Daryosh Yarahmdi, Asadollah Khoshkish, Mustafa Karampour, Ismail Ahmadi,
Volume 16, Issue 40 (6-2016)
Abstract
One of the Siberian high pressure system is the Earth climate system, atmospheric important. The purpose of this study, analysis of core changes Siberian high pressure system in the period mentioned. To identify the core spatial variations in the timeframe mentioned data, daily sea level pressure and temperature of the earth's surface with a resolution of 2.5 degrees within the space of 30 to 65 degrees north latitude and 130 degrees east longitude from the database 45 to NOAA NCEP / NCAR for the cold was extracted. The core of the GIS spatial data analysis system and two separate zones and point to output six decades was ten years old and were analyzed. To study the process of change, determine the direction of the trend, type and timing of changes in temperature and pressure of the core of the system the test of Mann-Kendal is used. Comparison between the first and sixth decades 60-year period showed that the core in January from the East to the West and in October and March from the North East to the South West from the Balkhash Lake to Baikal there has been a significant shift. Results also showed that during the same period the Siberian High central pressure was reduced in January while the land surface temperatures in January showed a significant upward trend. Unlike the months of October and January, in March the central pressure had few mutations but no trend was observed. However, during this month the Earth's surface temperature has increased significantly during thementioned period.
Abasali Arvin, Abdolazim Ghangherme, Davar Hajipour, Mehran Hidari,
Volume 16, Issue 41 (9-2016)
Abstract
In this study, by using the Mann-Kendall nonparametric method and Sen' s Estimator slope test, the trend of some elements including precipitation, average of maximum and minimum temperature and the number of snowy days Chaharmahal and Bakhtiari Province covers part of Zagros and Zardkohe-Bakhtiari highlands, from which three major rivers including Zayandehrud, Dez and Karun originate. in an annual and monthly scale, was evaluated in the stations of the province during a period of 30 years (1986-2015). The output was presented in the form of tables, graphs and iso-trend maps as drawn in the Arc_GIS. The results showed that although changes in rainfall did not follow any specific trend in most months of the year, the amount of precipitation in the stations of Koohrang as the rainiest station in the Province, Lordegan and Yan-Cheshme had a decreasing trend at the significance level of 99%; also, the the number of snowy days during March showed a decreasing trend in Koohrang station. However, the average minimum and maximum temperature in most areas of the province, in both monthly and yearly scales, except for the months of November and December, had a significantly increasing trend.
Dr. Mostafa Karimi, Mis Fatemeh Sotoudeh, Dr. Somayeh Rafati,
Volume 18, Issue 48 (4-2018)
Abstract
Increasing CO2 emissions and consequently, air temperature causes climate anomalies which affects all the aspects of human life. The purpose of this study was to assess the temperature changes and also to predict the extreme temperatures in Gilan and Mazandaran Provinces. To do this, the SDSM statistical and dynamical model was used. As well, it was applied the Mann-Kendal graphical and statistical technique to analyze the temperature changes and its trend. In this regard, the daily temperature was obtained from Rasht, Ramsar and Babolsar synoptic stations during 1961 – 2010, and also the general circulation models data of HadCM3 and NCEP were collected from related databases. The results revealed a significant positive trend in monthly and annual minimum and maximum temperature in all three stations in the first (1961-2010) and third (1961-2040) periods. There is not a significant trend in extreme temperatures in Ramsar and maximum temperature in Rasht in the second period (2011-2040). The Mann-Kendal graphical test was used for the yearly extreme temperatures in all periods. The results showed that it was occurred both increasing trend and suddenly changes or shifts at the 95% confidence level in all stations. It is occurred the highest of changes in monthly and annual of the minimum temperature at forecasted period (2011-2040). It was predicted extreme temperature to increase about 0.1 to 1.7° C. The short time oscillations and significant positive trend occurred in both the maximum and minimum temperature shows the temperature increase and climate changes in the future. Thus it is obvious the decrease in temperature difference in warm and cold seasons.
Sayyed Mohammad Hosseini,
Volume 18, Issue 49 (5-2018)
Abstract
Precipitation is a climatic elements that have temporal - spatial distribution. In this research database of Global Precipitation Climatology Centre (GPCC) with a resolution 0.5×0.5 degree for 50 year is used, that was constituted with dimensions of 12800*600. Temporal data are on the columns and pixels (spatial data) located on the rows. The results show an increasing trend in spring and fall but in summer and winter precipitation trend has been decreased. The most amount of precipitation is located in the northern parts of the Black Sea and Mediterranean Sea, Southeast Asia, southern coast of the Caspian and Central Zagros Mountains. Most of Middle East (about %95) have not trend and only in some parts of Kazakhstan, Afghanistan, Pakistan ,central Iran, and areas in lower-latitude have positive trend and some East and northwest parts of Iran and some parts of Middle East also have decreasing trend of precipitation. The highest percent of area of precipitation trend gradient is 0 to 0.5.
Fatemeh Mohammadyary, Hamidreza Pourkhabbaz, Hossin Aghdar, Morteza Tavakoly,
Volume 18, Issue 50 (6-2018)
Abstract
Land-use change is one of the most important challenges of land-use planning that lies with planners, decision-makers and policymakers and has a direct impact on many issues, such as economic growth and the quality of the environment. The present study examines the land use change trends in Behbahan city for 2014 and 2028 using LCM in the GIS environment. Analysis and visibility of user variations, carried out in two periods of Landsat satellite images of 2000 (ETM + sensor) and 2014 (OLI sensors), and land cover maps for each year. The transmission potential modeling was performed by using the multi-layer perceptron artificial neural network algorithm using six independent variables and the distribution of changes in user usage were calculated by Markov chain method. The results of the prediction showed that the most reduction in the changes is the degradation of the rangelands and the greatest increase in the area of agricultural use. According to the horizontal tabulation results of the 2028 map, it can be stated that from the total area of the area 28336.22 hectares of land were unchanged and 33223.78 hectares of land use change. Also Rangeland and forest degradation during this time period can be a danger to urban planners and natural resources.
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Rahmatollah Shojaei Moghadam, Mostafa Karampoor, Behroz Nasiri, Naser Tahmasebipour,
Volume 18, Issue 51 (7-2018)
Abstract
The purpose of this study is to analyze and analyze Iran's precipitation over the past half-century(1967-2017). For this purpose, the average monthly rainfall of Iran during the statistical period of 50 years was extracted from Esfazari databases (Which is provided using data from 283 stations of Synoptic and Climatology). Regression analysis was used to analyze the trend and to analyze the annual and monthly rainfall cycles of Iran, spectral analysis was used. Investigation and analysis of monthly precipitation trend indicates that except for central Zagros (Lorestan and Chaharmahal va Bakhtiari and Gorgan areas, where rainfall in winter season has increased trend), in other parts of the country and in other seasons, the trend of decline Precipitation is prevalent. The study of Iranian rainfall cycles has been shown that Most of Iran's rainfall cycles are 2 to 4 years old and have a short term course. Meanwhile, there are two middle-cycle 25-year cycles in January-July and two long-term 50-year cycles in March and December, indicating a trend in the March and December rainfall. The two months of February and October lacked a clear cycle. The analysis of the auto-correlation model of rainfall showed that the high spatial auto-correlation model in winter was consistent with the western, southwestern and coastal of the Caspian Sea and covered about 14% of the country's. The low spatial auto-correlation model is found in sparse spots in the southern, central and southeastern regions of the country in winter and spring, and covered about 7.5% of the country's. The results of this study indicate that the overall trend of Iran's rainfall is decreasing trend and only in winter, in the small regions of the country, the increase trend is observed.
Yousef Ghavidel Rahimi, Manouchehr Farajzadeh, Esmaeel Lashani Zand,
Volume 18, Issue 51 (7-2018)
Abstract
In this study, the changes in the Khorramabad storm in the period of 1952 to 2015 have been investigated. For this purpose, data from meteorological codes 06 and 07 were received from the Meteorological Organization of the country, and after identifying the days of winding with dust storms and calculating their monthly frequency, monthly, seasonal and annual time series were analyzed. In this study, descriptive statistics, cluster analysis, linear and polynomial trend analysis, and nonparametric Mann-Kendal test were used to study the frequency variation of dust storms in Khorramabad station. The results of the research showed that the monthly frequency of dust storms in Khorramabad station in the middle of May, July and June is May and July, respectively, and from May to July (May to July), the frequency of storms in the dust and dust Khoramabad station is added that this issue is not related to the district heating and dry season. In the seasonal season other than the autumn, which is not frequent with frequent dust storms, in the rest of the seasons, especially in spring and summer, the seasonal concentration of dust storms in Khoramabad has been intensified. The analysis of the trend of time variation in the occurrence of dust storms in Khorramabad station showed that in most of the months of the year and in the three seasons of spring, summer and autumn, as well as in the annual period, there was a significant change in the frequency of dust storms in Khorramabad station. It is increasing with a relatively steep slope, indicating that in the future, the frequency of dust storms in Khorramabad station will be increased.
Ali Bahri, Younes Khosravi,
Volume 20, Issue 58 (10-2020)
Abstract
Considering the vast application of sea surface temperature in climatic and oceanic investigations, this parameter was studied in Oman Sea from 1986 to 2015. The SST was surveyed using trend analysis and Global and local Moran’s I spatial autocorrelation. In trend analysis, the Mann-Kendall test was used to determine the trend of SST changes and the Sen's Estimator method was used to examine the slope of the changes. Using these methods, it was found that during January, February and December, there was no significant ascending trend in SST values, and only parts of the Strait of Hormuz had a significance descending trend. On the other hand, there was no significant descending trend in March, and the ascending trend in the SST was seen in the southern part of the Oman Sea. Other months of the year had a significant ascending and descending trend in different parts of the Oman Sea, which October had the highest ascending trend. In the annual time scale, it was also found that the southern parts of the Oman Sea had ascending trend in the SST value and Western parts had a descending trend. The occurred changes in the high amounts (positive and negative) were corresponding to the significance ascending and descending trends. The results of Global Moran for the annual time scale indicated an ascending trend of autocorrelation values and cluster patterns of SST data over time, using the local Moran analysis, it was found that warm clusters of SST are increasing in the Oman Sea, and on the other hand, cold clusters of this parameter have been reduced over 30 years. According to the results of trend and spatial autocorrelation analysis, it has been found that SST have been increasing in different parts of the Oman Sea during 30 years, so climate change and global warming may have affected this region.
Dr Hossein Asakereh, Nasrin Varnaseri Ghandali,
Volume 22, Issue 64 (4-2022)
Abstract
Change in precipitation features is one of climate change outcome. Change in precipitation amount, especially in warm season, may influences climato-environmental phenomenon as well as human activity. In current research the decadal changes of monthly precipitation over the Caspian coast of Iran territory was evaluated. Accordingly, a large number of rain gauge stations (385 stations), where rainfall is measured painstakingly, have been used. these stations are under the supervision of Meteorological Organization of the country and Ministry of Energy. Since the original dataset pertaining to the precipitation prior to 1966 had noticeable missing values, and the data after 2016 were not accessible, a continuous time period from January 1966 to December 2016 was selected. From the daily precipitation of aforementioned stations contour maps were created using an ordinary Kriging method. The spatial resolution of these precipitation maps was 3 km * 3 km. Our finding showed that during the under investigation period the maximum gradient of precipitation moved from coastal parts toward mountainous area. Decrease in the area with high precipitation and increase in the low precipitation area is an other prominent decadal characteristics. According to the previous study, these changes might attributed to changes in systems which effect precipitation in the Caspian coast of Iran (northward movement in polar vortex, sub-tropical high pressure and cyclone truck). In addition, increasing temperature trends in the summer tend to decrease temperature spatial differences. Therefore, the convectional precipitation during summer has been decreased.
Dr Behzad Amraei,
Volume 22, Issue 64 (4-2022)
Abstract
Climate change is one of the most important challenges facing water resources management, including surface water and groundwater. The main purpose of this research is to detect the effect of droughts caused by the change in groundwater resources in Birjand plain. In this regard, using two nonparametric trend tests, the SENS and MAN-Kendal gradient estimates to detect the process of underground water level in Birjand city during the statistical period of 1370-1395 according to the statistics of the field of 47 areas of observation area (census water resources) Wentified. Using Pearson correlation matrix, correlation between climatic elements (Birjand station) temperature, precipitation and evapotranspiration and potential transpiration were calculated with the level of local city of Birjand, and based on a multivariate regression model for modeling the annual time series at the level of confidence level of 95 / 0 was developed. Climatic factors of 2080-2065 using the Output of the HADGEM2-ES model through the LARS-WG exponential model for the position of the Birjand station under two scenarios RCP8.5 and RCP2.6 were simulated and based on the regression model, the surface of the water Birjand city was simulated. The results indicated that firstly, in the base period (1370-1395), the surface of water in the area with an annual gradient of 47 centimeters per year was reduced. The correlation analysis indicated that three elements of rainfall, temperature and evapotranspiration were modeled in a linear composition of 75% of the annual changes in groundwater. The results of the microsterge model implemented on HADGEM2-ES data indicate that during the period 2035-2065 under both the scenario, groundwater level between 10 and 13 meters lower than the base period, which resulted from an increase in evapotranspiration And consequently, rainfall will be effective.
Hossin Asakereh, Piero Lionello, Hossein Mirmousavi, Sahar Sadrafshari,
Volume 22, Issue 66 (10-2022)
Abstract
The purpose of this research is to identify changes in the temperature trend in the western half of Iran. For this purpose, monthly temperature data of 15 synoptic stations were collected during 1960-2010. Quality control was applied on these data by applying Pettit, SNHT, Buishand and Von Neumann’s tests. Later data Simulated and compared with reanalysis data such as ERA-Interim, ERA-20C, NCEP and CMIP5 models (RCP8.5 for the period 1960-2100). Trends were calculated by the Mean Kendall test and the Sen’s estimator (95 % confidence level). Based on the results obtained from all models, a significant positive trend was observed in spring, summer and autumn, and only in winter according to ERA-Interim. Based on CMIP5 results for the period 2050-2100 values between 2 and 4 ° C/100 achieved, which is lower than the results of other models for the period 1979-2010. Considering the CMIP5 models and their overall average in the study area, an increase in annual temperature (7 ° C /100) for the second half of the 21st century was confirmed.
Ms Zienab Hosinpoor, Dr. Aliakbar Shamsipour, Dr. Mostafa Karimi, Dr. Faramarz Khoshakhlagh,
Volume 23, Issue 68 (4-2023)
Abstract
Heat waves are important phenomena in Iran, And its upsurge in recent years seems to have a high upside trend.This climate has a negative impact on agriculture, forest fire and forestry, water resources, energy use and human health.The purpose of the research is to explain the frequency, time distribution, continuity of thermal waves, and the identification of its occurrence in the southern foothills of central Alborz.Therefore, using the statistical methods and maximum daily temperature data of Tehran (Mehrabad), Qazvin and Semnan stations for the statistical period of 30 years (1966-2016), the mentioned characteristics were extracted.In the first step, the nonparametric method of Kendal was used to understand the variability and awareness of the monthly trend of maximum temperatures in the study period.In order to determine the severity, duration and frequency of heat wave events, the percentiles (95.98) and normalized temperature deviation (NTD) were used.The results of the study showed that the frequency of short-wave heat waves was higher.Most frequencies are related to 2-day waves, respectively, and Tehran (Mehrabad), Semnan and Qazvin stations are more frequent.The highest frequency of annual events was detected at stations in Tehran (11 waves in 2010), in Semnan (9 waves in 2015) and Qazvin (7 waves in 2015), respectively.The highest frequency of monthly heat wave events was recorded in June and September.The highest continuation (15 days) was obtained in March 2008 with the percentile method at Mehrabad station.In the normalized deviation method, the temperature was calculated as a warm wave (12 days) in 2008.The highest annual frequency of heat loss occurred in all three stations in 2015.The evolution of the process indicated an increase in the incidence of thermal waves in the cold period of the year But in other chapters, no meaningful changes were made.As it says, the decline in cold winter temperatures is on the southern slopes of Alborz.The results of the two methods showed that in the normalized deviation of the temperature, the number of thermal waves more than the percentile method was recorded, but in the percentile method, the thermal wave was more prominent in the cold period of the year.
Mina Mirian, Mostafa Karampoor, Mohamd Moradi, Houshang Ghemi, Behrouz Nasiri,
Volume 23, Issue 68 (4-2023)
Abstract
The purpose of this study is to determine the long-term variations in rainfall data as well as to identify wet and dry periods of 35 synoptic stations in Iran. In order to know the variation of rainfall in studied stations, average maps, coefficient of variation and skewness were drawn. Then, using the Mann-Kendall test, the significance of the trend on each station was tested at 95% confidence level. Finally, wet and dry periods were identified by using 20% high and low extreme rainfall during the 50-year study period. The results show that the general model of the country's regime is that the rainfall levels from the north to the south-east and from the west to the east of the country are reduced. The lowest values of the coefficient of variation and skewness are related to the northern regions especially the Caspian seaside and the highest amounts are in the southern regions, especially in the south and south-east. In general, the results of the Mann-Kendall test show that rainfall data in the seasonal scale, with the exception of several synoptic stations, do not show a significant trend. Most wet periods occur in the spring and the lowest in summer and the highest dry periods occur in the autumn and the lowest in spring. The number of droughts in the cold periods is significant. Also, the frequency of occurrence of dry periods is more than wet periods.
