Climatology
abdolreza hosseini; sayed mohammad hosseini; Rahman Zandi; hasan hajimohammadi
Abstract
IntroductionSnow, as one of the important climatic-hydrological parameters, has a significant role in providing the world's water resources for industrial, agricultural and drinking purposes. At the same time, the dangerous consequences of heavy snowfall, avalanches, destruction of rural housing, disruption ...
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IntroductionSnow, as one of the important climatic-hydrological parameters, has a significant role in providing the world's water resources for industrial, agricultural and drinking purposes. At the same time, the dangerous consequences of heavy snowfall, avalanches, destruction of rural housing, disruption of road transport and communication and numerous other consequences that it has on the natural and human environment are significant for environmental scientists (Shakiba et al, 2015: 88). However, heavy snowfall, especially in the lowlands and lowlands of the middle latitudes, is unexpected and somewhat surprising. So that its continuation for a few days in these areas will have negative effects on practically all living standards of the residents of these areas (Hosseini, 2014: 101). In recent years, the use of satellite data in natural, hydrological and water resource management has grown significantly, and in this regard, MODIS sensor images due to acceptable spatial resolution and fast temporal retrieval power with a variety of bands. Spectral has put it in a good position. Also, due to the very high albedo of snow, it is possible to measure the level of snow cover using satellite data. MethodologyIn the present study, the environmental approach to circulation was used to investigate the relationship between circulation patterns and heavy snowfall. Thus; first, the days of heavy snowfall in the studied stations were identified and then the synoptic patterns and atmosphere of the representative days were analyzed. In this regard, after receiving snow altitude data from the Meteorological Organization, heavy and widespread rainfall events were identified in three western provinces of the country, including Hamadan, Kurdistan and Kermanshah in the form of 16 synoptic stations, during the years 2000 to 2019. In order to study and analyze the synoptic patterns of days with heavy snowfall, by referring to the website of the National Center for Environmental Forecasting / Atmospheric Sciences (NCEP / NCAR), daily data on Sea Level Pressure (SLP), High Geopotential (HGT), zonal wind (UWND) and meridianal wind (VWND), air temperature (Air) and instability index (Omega) were extracted at the intersection of 2.5 * 2.5 and the relevant maps were drawn using GRADS software. Also, the area covered by snow was obtained from MODIS satellite images. MODIS data are of level1b type, which was calculated based on the parameters in the header, radiance and reflectivity. Reflective and thermal parameters for bands 4 and 6 were also used to apply the NDSI (Normalized Difference Snow Index). Results and DiscussionAfter 20 years of study, 8 days were identified that heavy and heavy snow had fallen in the area. On February 4, 2011, in the middle of the atmosphere, a deep trough formed in the western Mediterranean and North Africa, with a strong positive vorticity. This situation has affected the study area.The location of this trough in the Mediterranean provides the moisture needed for snowfall from the Mediterranean Sea. ConclusionsThe results showed in the ground formed a powerful cyclone on Iraq and turbulent weather caused chaos for the region. This condition causes the air to cause accelerated the rise of the package and water vapor in the atmosphere with his quick ascent to the seed quickly convert hexagonal snow. Creates a pressure gradient that causes more than 12 HPa in the region was to create a strong front will be formed in the region. In the high latitudes of cold air and warm air in front of it is the lower latitude. Has caused more than 60 to 70 percent of the study area are covered by snow. A deep trough of cold air loss in middle levels at depths greater than 25 degrees latitude has been. With extreme vorticity and air along rapid ascent has been closed. NDSI index showed the results of actions by deploying the most weather systems has gone down snow-covered forests of western Iran.
Geomorphology
najmeh shafiei; LAILA GOLIMKOTARI; Aboalghasem Amir Ahmadi; Rahman Zandi
Abstract
Introduction
Today, the phenomenon of land subsidence is one of the most important geomorphological hazards on a global scale, which causes great damage to urban and rural structures, development facilities. Most of the reports from around the world related to the phenomenon of land subsidence have ...
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Introduction
Today, the phenomenon of land subsidence is one of the most important geomorphological hazards on a global scale, which causes great damage to urban and rural structures, development facilities. Most of the reports from around the world related to the phenomenon of land subsidence have been related to arid and low rainfall areas. According to the US Geological Survey, a subsidence phenomenon involves a collapse or subsidence that can have a small displacement vector. Land subsidence is a geological phenomenon that causes the earth's surface to descend slowly and horizontally.
In recent decades, most joints and fissures in agricultural areas have been reported due to over-abstraction of groundwater. Recently, urban areas have also been affected by this phenomenon. These seams and cracks cause a lot of annual damage to ground-level installations such as roads and bridges, buildings, power transmission lines, oil and gas transmission pipes, water pipes and sewage systems, wells wall pipes of exploitation wells. In addition, they provide a path for surface pollutants to move to groundwater sources and contaminate groundwater by infiltrating aquifers.
Among the innovations of this study, for the first time, radar interferometry technique was used to investigate the risk of subsidence of Nurabad plain aquifer subsidence. , Identification of vulnerable areas in the aquifer area.
Methodology
The method used in this research is applied analysis. Groundwater data including piezometer and exploitation wells were used to investigate groundwater level changes and Sentinel 1 images were used to calculate radar interferometry. Geographic weighted regression model (GWR) was used to investigate the relationship between subsidence and groundwater loss parameters.
By examining the changes in groundwater level of piezometer wells in the aquifer during a period of 17 years (1380-1397) showed that an average of 15 meters of groundwater drop has occurred in the plain. This decrease in agricultural and residential areas is a priority compared to other uses. By preparing the output of radar images during 4 statistical years, the results show that in 2015 the maximum amount of leakage was 7 cm and in 2016 it increased to 8 cm. In 2017 it is equal to 9 cm and in 2018 it is equal to 10 cm. In the end, by calculating the average of these four years, the amount of subsidence at the aquifer level increases significantly, with the regions in the central and eastern parts of the aquifer having the highest subsidence at the aquifer level. Which has been developed in residential and agricultural areas of the region so that the effects and evidence of these meetings are visible in residential houses and agricultural lands according to Table (2) in the analysis section to examine the status of subsidence rates in the study area using Radar images were taken during the mentioned years and show that in 2015 it is equal to 8 square kilometers, which is compared to 2014, in 2016 it is equal to 34 square kilometers, and in 2017 and 2018 it is equal to 40 and 86 square kilometers. According to the maps, we see in these 4 consecutive years that every year b The amount of subsidence at the plain level has increased and thus subsidence at the plain level has become a kind of hazard.
Results and discussion
High values of R2 have occurred in the central parts of the model aquifer, which shows a good estimate of the model in estimating the dependent variable and the predictive explanatory variable. Also, relatively lower values are located in the southern parts of the aquifer by examining the subsidence status in the plain. By creating a relationship with the groundwater drop layer, it showed that the observed values with the predicted values indicate a strong relationship. The layer shows the coefficient of determination R2, which is the highest coefficient of R2 in the central part, which is about -0.79 Is 0.53 Figure (7). The distribution of the remaining space of the GWR model errors shows that the model outputs are closer to the actual values. Second, the resulting map shows the low error values in the range.
Occlusion
The average subsidence rate is about 4 cm per year and the average 4-year average is 16 cm. The average area of the aquifer where the subsidence has taken place during 4 years is about 36 square kilometers, which includes about 5% of its area. The high concentration of wells and the greatest drop in groundwater and the concentration of existing cities and villages. In these areas, due to the water needs of the residential community, including the city of Nurabad and surrounding areas, as well as the water needs of the industrial sector, including factories and agricultural activities, access to water resources is more and groundwater extraction is very high. There has been a high decline that these factors with the intervention of the arid climate of this region has caused the high talent of these areas in the discussion of subsidence and has been identified as one of the critical areas of the city in the subsidence map. The results of radar interferometry show that uncontrolled extraction from the surface of underground reserves has caused the subsidence of the central part of the aquifer and also the presence of several aqueducts at the aquifer has caused damage to residential centers. One of the areas with the highest risk of subsidence in the plain, in the eastern, central and southern parts, the rate of groundwater loss in the aquifer within 14 statistical years is about 22 meters in the same well and the results of GWR method show local R2 in the central parts of the aquifer which is about 79% maximum and shows a high correlation between subsidence and groundwater loss Residual rate in the central part which is equal to 0.007 / 0007 which is a high coefficient of significance.
