جستجوی مقالات مرتبط با کلیدواژه « temporal changes » در نشریات گروه « جغرافیا »

The purpose of this research is to investigate the temporal changes and spatial distribution of the total cloud cover of the sky in the Ormia Lake drainage basin. In order to achieve the goals of this research, observational data on total cloud cover of the sky at five selected meteorological stations and the product of total cloud cover of the sky (CFFCM) from MODIS sensors (Tera and Aqua) were used. The observed cloudiness values according to the ICAO standard were classified into five classes: cloudless sky, slightly cloudy, partly cloudy, semi-cloudy, and full cloudy, and the sky cloudiness changes were investigated. Pearson's correlation test was also used in order to investigate the relationship between the total cloud cover of the sky and the elements of precipitation, temperature, evaporation, and sunshine hours.The findings of the research showed that in the study area, the sky is mostly clear (28.7%) and slightly cloudy (23.9%), and only about 30% of the cases are semi-cloudy and full cloudy.In the examination of the frequency of occurrence of each of the cloudy classes, it was found that, in most cases, there was an increasing trend in the clear and slightly cloudy classes and a decreasing trend in the semi-cloudy and full cloudy classes.The study of the correlation coefficients between the total cloud cover of the sky and climatic parameters showed that there is a direct and significant relationship between the cloudiness of the sky and annual precipitation and an inverse relationship with temperature, evaporation, and sunshine hours, which is weaker in the case of annual temperature than the rest of the parameters, and also that the relationships established with observational data are more logical than those established with those established with satellite data. Investigating the spatial distribution of average seasonal cloudiness showed that cloudiness in winter and autumn is different from spring and especially summer. The highest amount of winter (summer) cloudiness is observed in the southern (northern) half of the Ormia Lake drainage basin, and this arrangement is consistent with the seasonal synoptic currents and the distribution of altitudes.

In this research, in order to reveal possible climate changes, the time series of annual average temperature of Urmia synoptic station during the statistical period of 1951-2017 was studied. Box-Jenkins prediction model (integrated auto-regressive and moving average model) was used to find the change model and predict the behavior of the time series. After fitting different models, R2, Akaike information criterion (AIC), regression standard error (SEE) and the Schwartz-Bayesin criterion (BIC) were measured to select the optimal model. The results showed that the time series model ARIMA (2,2) (1,0) has better results compared to other models and the trend of time series changes of this model has less error. After choosing the best model, the average annual temperature values for the next 13 years were predicted using it. The temperature prediction was done using this model with a good fit and the correlation between the actual and fitted values was around 82%. After ensuring the correctness of the forecast, the time series until 2030 was estimated. The forecast of the model indicates a mild temperature increase in the coming years with an upward linear trend. The study of the general circulation of the atmosphere of the region by drawing and analyzing the difference maps for the parameters of geopotential height of 500 hpa, relative rotation of 500 hpa, vertical velocity of the atmosphere (Omega) and air temperature on the surface of the earth indicates the strengthening of the stability of the atmosphere as well as the increase in temperature. The air of Urmia city is 0.4 degrees Celsius compared to the past, which confirms the results of the Box-Jenkins model.

The purpose of this study was to analyze the relationship between land use changes in different time periods using landscape metrics in the KoozehTopraghi Watershed located in Ardabil Province. For this purpose, three Landsat satellite images from 2000, 2010, and 2021 were received from the United States Geological Survey (USGS) database. After preparing the land use maps of the watershed by supervised classification and converting it to a raster format, the landscape metrics of Fragstats 8.2 software were calculated and quantified in two levels of landscape (22 metrics) and class (13 metrics). The kappa coefficient for the land use maps of the three years under study (2000, 2010, and 2021) was equal to 58.2, 75.0, and 59.2 %, respectively. The results showed that at the level of class, rainfed agriculture had the maximum value in the edge density metric, and irrigated agriculture had the maximum values in the average distance of the nearest Euclidean neighbor, the number of patches, and the total edges in all three years. Furthermore, at the landscape level, the fragmentation index decreased slightly in 2010 compared to 2000 and then increased in 2021. The largest patch index also showed a significant decrease in 2021, so it has reached from 43.34 in 2000 to 34.81 in 2021.

During the recent years in Iran and especially arid and semi-arid due to natural and human factors, has been seen the underground water level drop. The aim of this study was to examine the spatial and temporal changes of underground water level using geostatistical methods. First, were collectedthe static level of the data related to the 39 wells in the aquifer Bayza plain seasons of spring, summer, autumn and winter of blue year 2003-2004 to 2012-2013.After quality control and ensure the normal data,The results of the deterministic methods of statistical estimation for static surface and ground water based on cross-validation technique statistical criteria the second root mean square error case evaluated. The results of the deterministic methods and geostatistical for estimation of groundwater levels case evaluated based on cross-validation technique by statistical criteria root mean square (RMSe). The map water level changes showed that in all seasons, the underground water level in the North plain is higher and gradually towards reduced the Center and the South Plains. View to be largest decreases the level of stagnation in fall blue year 2012-2013 to amount of 14.3 m, and minimum water level drop in winter blue 2003-2004 to amount of 5 m.

The Khoshk river emanates from golestan and ghalat height and flow to the northwest and southeast direction. After traversing a short distance it cover's golestan and dukohak,goiom from the right and the ghasr ghomshe branch from the left. Then by direct cross from the middle of shiraz metro police, it will divide it into to half south and east and at the end, it will pour into maharlo lake.numorus researchs with different method and purposes has been done I. Side and outside of the country about the change of morphology and effective factors for them. The aim of this paper is investigating the changes of manipulation the zones in time-place range in the sanctum of the river.
The main researching method, in this paper is the traverseal and analytical method. Thus for determining the ranges in the limitation of the case we study about existing maps, scope revision and Google earth software have been used. And then the oldest satellite images of the zone (Lansat8 OLI imagery) have been provided for 1394 with the power of 30 meter state dividing coherent to Shiraz metropolis. By the use of geological maps and topography, air shots and satellite images of shiraz were studied and geomorphologic annotation of them were done about expanding the city in sanctum of the river as to recognize the changes of dry riverbed due to urban expanding in two time sections 1394 and 1346.
In this paper the riverbed divides in to 3 ranges as follow.
First range: the direction of chanarsookhte is from tange sorkh to Maliabad Bridge with 8 km long and average slope of 1.42%. Riverbed is formed by generally marine stages and Razak marine lime. The feature of this part of river is rash slope, severe erosion of near lands, brinding of strand. And the width of illuviation has been reported about 70 meters. The average of river's width on the air image in 1346 compared to 1394, has been reduced 19 meters. The space which the river has been changed to 56ha in 1394 which means 27.5 percent of river space has been reduced because of human operations in the sanctum of river, removing sand from the riverbed and the buildings.
Second range: from maliabad bridge to Fazilat Bridge is 15 km and the slope is 0.90%. In this direction, nahre azam sideway, ghoran gate, sadi, bajgah and etc pour in to Koshk River. Because of appropriate soil and enough mineral water, the gardens and agricultural lands has been expanded near the river. The property of this range is that the river's channel has been shored by the stile barrier. The narrow pass way of river channel, unsuitable bridges, floor fraction, lateral erosion of river, building sideways in both left and right shores of the river with the length of 7 km and urban buildings in the foot print of river. Thus most of the violation to the sanctum of river has been occurred in this range which has caused bad issues for Shiraz metropolis in the future.
The average width of river in 1394 compared to 1394 has been reduced 140 meters. And on the other side the space has been changed from 312 ha in 1346 to 92 ha in 1394 which means 70.5% of river's space has been reduced because of the change of controlling the lands due to human operation in the sanctum of river.
Third range:From the fazilat bridge to the exit of river from the city is 10 km in the length and 0.39 percent in average slope. The kind of bed's sediment is formed of torrential illuviation and kovaterner sediments. And the thickness of the illuviation has been reported 200 meter. The property of this part of low slope, is settling the sediments and reduction of river tension, low capacity at the time of big floodwaters.
Most of the river direction has been shored by the stile barrier and the mean width of river compared to second range is lower (42m) and it's mean depth compared to around deserts is 1.5m-2m. Nowadays the average river width compared to 1346 has been reduced about 49 meters. And the river's space in this range in 1346 is about 95ha but nowadays has been reached lower than 50ha. It means that 57% of river space has been decreased. Which by the effect of urban expanding and agricultural operations in this range has caused the constriction of the river pass way. As in every raining, it causes the uprising of river down the Sardkhane Bridge.
Investigating the changes of urban expanding effects and changing the lane controlling in the sanctum of Khoshk River, are the most important aims of this paper which has been evaluated. According to the results of urban expanding investigation in the first rang, there is Alluvial fan in the Foot of mountains foothill stone which is firmed by sediments, maren, shil and weak seeds articles. But in the second and third local sections, the city is placed in a desert zone which the kind if the sediments of illuviation articles are kovaterner. Urban expanding in the sanctum of river in the above time-local ranges causes the reduction of riverbed space compared to last year. In that the space of river bed has been reached from 77ha to 56 ha (27.5%) in the first range and from 312 to 92 ha (70.5%) in the second range and from 95 ha go 41 ha (57%) in third range. And also width displacement of the river was 176 meter in first range, 145 meter in the second range and 68 meter in the third range. In the past, the firm of city was nuclear and compressed and occupied lower space of river sanctum. The result is that the type of physical expanding of this city has been proceed thorough linear type.

In this research, daily and hourly data of dust storms (horizontal vision and meteorology codes) at 26 synoptic stations of western Iran for the period of 1990–2013has been used in order toidentifying and determining trend of dust-storm-frequencies. In this research, visibility less than 1000 was used as factor in order to determining dust storm (local and external) for all of dust storm meteorology codes. This data was investigated by parametric and non-parametric tests including Man-Kendal, Sen’s and regression test in yearly scale.Results indicated that a set of 26 data series, 9 data series in Man-Kendal method, 6 data series in Sen’s method, and 13 data series in regression method have significant positive trend in significant level at %1 and %5. The results of all three methods indicated that most of stations in western half Iran have increasing trend of dust storms. It increased markedly in southwest of Iran.

Various plannings in agriculture, hydrology, architecture and energy largely depend on the correct estimation of the amount of solar radiation. To estimate the solar radiation, most of the previous studies have used Angstrom model, having the values of sunshine hours as it's input, or regression equations through considering the climatic factors and elements affecting the radiation. In this study, optimized "Bird and Hulstrom" model is used to estimate incoming solar radiation in Kermanshah Province by using the daily data from synoptic weather stations of the province between the years 1990- 2009. For this purpose, all parameters involved in radiation, including length of day, humidity, air mass, air pressure, precipitable water, sky albedo, atmospheric absorption and absorption by ozone were used and the resulting spatial-temporal variations of radiation were analyzed. The results showed that there is little difference between the radiation values measured by pyranometer and values estimated by the model. This indicates the ability of the model to estimate radiation. The least amount of incoming solar radiation in the region occurs in January and December, which varies from 9 to 13 MJ/m2/day in different locations of the province. The amount of radiation absorbed by ozone is reduced in the summer due to the reduction of air mass, especially in the highlands; while the amount of direct radiation and thereby total radiation is increased in this season. The highest amount of incoming solar radiation in the region occurs in June, which varies from 32 to 42 MJ/m2/day in different locations. In autumn and winter, radiation differences in the region are reduced because of the role of diffuse radiation.