جستجوی مقالات مرتبط با کلیدواژه « توپوگرافی » در نشریات گروه « آبخیزداری، بیابان، محیط زیست، مرتع »

Airborne particles play an important role in the balance of atmospheric radiation and climate change. The relationship between aerosols and climate systems has received increasing attention as our understanding of these issues increases. A dust storm is a complex process that is influenced by the interactions of atmospheric systems and is basically caused by conditions such as high wind speed, bare soil and dry air.

Aerosol optical depth (AOD) is one of the most important parameters in the field of dust related research. Aerosol optical depth actually refers to the distribution of dust aerosols in the atmosphere. In this research, the dust condition was investigated using the AOD parameter of MODIS product. In order to investigate the relationship between environmental factors, NDVI was used. For each year, based on the total images taken, which is about 24 images per year, the average vegetation cover index was calculated in the Google Earth Engine system as a time series. In this study, among the climatic factors, annual rainfall data from synoptic stations were used to investigate the effect of rainfall on the amount of dust changes in the period from 2013 to 2022. Also, a 90-meter DEM was prepared from the SRTM sensor in order to prepare layers of slope percentage, slope direction and elevation classes.

In the research, firstly, to evaluate the dust situation, the aerosol optical depth product was obtained from the MODIS sensor. In order to highlight and monitor as much as possible, the dust phenomenon of the months of June to September, corresponding to the late spring and summer season of each year, when the majority of dust storms are concentrated in these months, was chosen. After downloading the images, the 9-year statistical period (2013-2022) was considered as the studied statistical period in Khuzestan province. The average optical depth of dust was obtained each year based on the images taken in the same year. The results show that most of the dust was spread in the years 2015, 2016, 2017 and 2018, so that a large part of the province faced the dust phenomenon in these years. The investigation of the dust situation in 2013 and 2014 showed that although most of Khuzestan province is facing a relatively low average AOD, the maximum AOD value is related to classes with values of 0.71 to 1.5 and more than 1.5 located in the southwest. is the province; The maximum value of AOD in these years was 2.82 and considering that AOD is between zero and 5 in the mentioned years, the southern regions have faced a high average dust phenomenon. The purpose of this study was to monitor dust and investigate its relationship with various factors of topography, vegetation and climate. The results of dust relationship with the mentioned factors showed that among all the factors, height and slope direction have the highest correlation (83 percent) and (72 percent) respectively with the phenomenon of dust in the opposite direction, so that an increase in the amount of height causes a decrease in dust and south-facing directions. And smooth areas will have an increase in the amount of this phenomenon. Therefore, by using remote sensing techniques, it is possible to identify dust centers as a valuable tool to combat the expression factor.

Desertification is one of the most obvious ecological and environmental problems in arid and semi-arid regions. n this study, to identify dust spots, changes in the average occurrence of dust storms were obtained using MODIS sensor data from 2013 to 2022, and then its relationship with climatic factors, sun cover with NDVI index, and topography were evaluated. A decrease in the amount of precipitation that can lead to a decrease in soil moisture, vegetation cover and an increase in drought; Also, the changes in land use in recent years are all among the factors that have led to an increase in the phenomenon of dust, especially in Khuzestan province. Examining the influencing factors such as topography, vegetation and climatic factors is of great importance in identifying and prioritizing the control of dust centers, in addition, the MODIS optical depth sensor product can be of great help as a valuable tool for monitoring and managing this event.

One of the environmental challenges in the world is desertification. Desertification is land degradation in arid, semi-arid and dry sub-humid caused by several factors such as climate change and human activities. Desertification is a significant phenomenon, particularly in arid and semi-arid regions. In many instances, it is seen as a serious threat to human societies. The desertification process in developing countries is very intense, and this issue can have a significant impact on the future of these countries. Iran is a country that is exposed to the phenomenon of desertification. Due to the geographical location, arid and semi-arid areas cover approximately two-thirds of Iran.  The desertification phenomenon is present in Yazd province. Due to its climate and hydrogeomorphology, this province, which is located in the central regions of Iran, has a high vulnerability potential against land use changes and desertification. Considering the importance of the topic, this research has identified the vulnerable areas of Yazd province against desertification using the DVI index.

In this research, library information, statistical data related to the population of Yazd province, climatic data of Yazd province, as well as the 30-meter SRTM DEM as the most important research data were used. The model used in this research was based on DVI vulnerability index. The DVI vulnerability index was the basis for the model used in this research. The time-spatial changes of vulnerability to desertification in the Banas River basin in India have been investigated using the DVI model. The DVI model uses 9 indicators, which are grouped into 4 groups: demographic indicators, weather indicators, topographic indicators, and soil indicators.

In this research, in order to identify the vulnerable areas of Yazd province to desertification from demographic indicators (population density, population growth and illiteracy percentage), weather indicators (precipitation rate, average temperature, and evaporation rate and dryness index), topographic indices (slope percentage) and soil science indices (soil type) have been used.The slope index indicates that the western parts of Yazd province are more vulnerable. According to the geological index, the northern and eastern parts of this province are highly vulnerable. The northern, central, and eastern regions of Yazd province are highly vulnerable in terms of precipitation, average temperature, evaporation, and dryness indicators. Yazd city has a high vulnerability potential in terms of population density index. In terms of population growth index, Ardakan city has a high vulnerability potential and also in terms of illiteracy index, Taft city has a high vulnerability potential. The location of Yazd province has resulted in a large portion of its area being covered in arid and hyper-arid areas. Due to their high vulnerability to erosion, destruction, and vulnerability, many parts of this province are prone to desertification. The DVI model was used to evaluate the vulnerability potential of Yazd province against desertification in this research. The DVI model results are divided into 4 vulnerability potential classes: low, medium, high, and very high. The results indicate that the class with a high vulnerability potential covers 42.9% of the area, which is primarily concentrated in the northern and central areas of Yazd province. The class with high vulnerability potential covers 41/4 of the area, which primarily encompasses the western regions of Yazd province. The classes with medium and low vulnerability potential are distributed in the central, southeastern, and southern parts of Yazd province, with 14.3 and 1.4 percent of the area, respectively. The vulnerability status of cities in Yazd province has been assessed in this research. Khatam and Bahabad cities have the lowest vulnerability percentage, while Yazd, Meibod, and Ardakan cities have the highest vulnerability potential, according to the results. Many parts of Yazd province, including its northern and central regions, have a high vulnerability potential, which requires special attention and the implementation of long-term programs to prevent vulnerability and increase desertification.

The phenomenon wherein precipitation increases as altitude ascends is referred to as the precipitation gradient, that significant importance in the field of hydrological forecasting in mountain basins and management of water resources. The present study aims to investigate the changes in the topography of the earth on the formation and movement pattern of precipitation, the average rainfall of the IMERG V06 satellite and the dem of the 0.1 degree elevation of the precipitation gradient for eight main directions or coding in the Python environment of the Alborz Mountains were extracted. Then, in order to determine the movement pattern of precipitation, longitudinal and latitude profiles were used. The study findings indicate that in the northeast region of Golestan province (positive gradient), there exists a positive gradient of precipitation, which amounts to 0. 44 mm.m elevation. Furthermore, it is worth noting that in the southeastern region of Semnan, there exists a negative gradient of 1. 91 mm.m reduction in precipitation of elevation gain. Additionally, it was found that the precipitation gradient was significantly influenced by both the north and south directions, accounting for 16. 8% and 25.4% of the effect, respectively, at a significance level of 0. 01. On the northern slopes, a negative correlation has been observed between the amount of precipitation and latitude, wherein higher latitudes are associated with lower precipitation levels. Conversely, a positive correlation has been noted between the amount of precipitation and latitude in other regions, where higher latitudes correspond to increased levels of precipitation. The intricate nature of precipitation in mountainous regions presents a challenge in establishing a comprehensive pattern due to the multifaceted influence of anthropogenic, climactic, and terrestrial variables, nevertheless, comprehending precipitation patterns in the context of decision-making can benefit water resource management.

Any plant according to its needs selects an optimal location of the environment as habitat. The aim of this study was to evaluate the relationship between plant species composition and edaphotopopographic factors in the steppe rangelands of Marvdasht in Fars province. Soil and vegetation sampling was carried out by random sampling and transect method, respectively. In this study, transects with a length of 30m were used. After sampling the soil samples were transported to the laboratory. In the laboratory content of OM, EC, pH, sand, silt and clay, Na, K and P were measured. The relationship between environmental factors and species composition was determined using DCA and CCA multivariate analyzes. The most important factors in the distribution of vegetation, were soil EC and Na. Altitude and slope were identified as effective topographic factors the composition of plant species.

In this research, habitat of Camphorosma monspeliaca was studied ecologically. This species has spread into an area of more than 3500 ha within Doto-Tangsayad in Chaharmahal and Bakhtiari Province. After identification of the stands of this species and selecting stands with and without this species; vegetation cover and environmental factors such as topography, physical and chemical properties of soil were studied Random-Systematic sampling method was considered with plots which that area was determined by minimal area method. Plant species was recorded along five transect per stand. In the present study quantities parameters of C. monspeliaca were analyzed using SPSS software. A matrix of plant stands and environmental factors was prepared and data were analyzed by the Principal Component Analysis (PCA) using PC- ORD software. Result indicated that Camphorosma monspeliaca species has scattered more along the second axis that plant stands were in southern aspect and had more density and cover percentage. From the results obtained on three topography position, slope aspect has significant difference on distribution of this species. In general, the most important effective environmental factors in vegetation distribution pattern were elevation, sodium, organic matter, sand, calcium carbonate and magnesium.