جستجوی مقالات مرتبط با کلیدواژه "spatio-temporal pattern" در نشریات گروه "جغرافیا"

Introduction :

Rapid population growth and limited production resources, especially in the agricultural sector, have made the issue of food security one of the challenges in the world. One of the main goals of sustainable development is to end hunger, achieve food security and develop sustainable agriculture. But predictions indicate that this goal will be difficult to achieve. Thus, world hunger is increasing and the lives of many people are directly and indirectly dependent on agriculture.

Purpose of the research: 

one of the basic approaches to agricultural development and food needs is to increase the yield and productivity of agricultural products for this reason, the present study was conducted with the aim of analysis patterns and spatial and temporal changes in cereal yield (wheat and barley) in Iran during a 35-year period from 1983 to 2018.

This study is an applied research and methodologically descriptive-analytical. Data and information were collected in a library method. Gi statistic or hot spot analysis used to discover the spatial pattern of cereal production (wheat and barley) and to identify its focal points. Arc GIS software was used to analyze the data.

Geographical area of research: 

The study area in this study includes the entire political and geographical area of Iran except open waters. In the present study, three levels of national (Iran), provincial (31 provinces) and counties (429 counties) have been analyzed for spatial and temporal changes in cereal yield.

Findings and Discussion During the study period, Isfahan province had the highest decrease in wheat yield and Khorasan Razavi province had the highest increase in wheat yield. In barley, some provinces such as Mazandaran, Fars, Kerman and Bushehr had the highest decrease in yield and Khorasan Razavi province had the highest increase in barley yield.

The results of research at the national and provincial levels show an increase in cereal yield during the study period. Also, spatial analysis at the county level shows the formation of a cluster pattern with a concentrate on high cereal yields in some plain areas of Iran

The analysis of dust hazard studies in southwest region of Iran in 22 years (1996-2017)
Dust storms are natural hazards that mostly occur in arid and semi-arid regions and there are many harmful consequences. According to the topographic-climatic conditions in Iran and the significant increase in the number and severity of dust storms occurrence in recent decades, especially in the West and Southwest regions where the dust storms are the most important environmental crisis. Studying this phenomenon is necessary for better management its harmful effects.
Since most of the research are implemented as different case studies, and there is no comprehensive study that review a wide range of existing researches with overall results in the southwestern parts of Iran, in this study a comprehensive overview of available literature reviews are addressed including dust spatio-temporal variations, modeling, detection, and health issues. This research is based on a library research and search of valid national and international scientific articles about the dust crisis and no data-processing. We attempted to analyze temporal and spatial variations in the south and southwest of the country using the available studies and the challenges of this phenomenon in the past and present to provide a new perspective to apply a comprehensive land management and managing environmental hazards in Iran with all the problems. A review of the history of dust storm studies from information sources showed that most researchers (61.40%) used a synoptic method to study dust storms, and the most important indicators that were considered by the researchers in physical properties were frequency and density, 34.21% and 34.21% of the studies respectively. Dust detection methods show that the use of thermal or reflective bands cannot detect dust phenomena with high precision, therefore, a model which applies both bands simultaneously should be developed. In other words, applying a combination of reflective and thermal spectra of Military Origin Destination Information System (MODIS) could offer better results in detection of dust storms in the study area. Studies indicate that most of the storms originate outside of Iran. Moreover, exposure to airborne contaminants, especially when the dust storms occur in the Middle East, can lead to an increase in the related diseaseoutbreak in the study area. For instance, there was a 70% increase in referring to medical centers for lung related problems when a dust phenomenon occurred. The Results showed that in cold seasons where low height and western waves is formed on the European and Mediterranean Sea, due to the heaviness, cold air in these days, can penetrate low latitudes and their trough is located over the Middle East area. Under warming condition, the front of rough is formed as ridge, then engendered turbulence and wind. In the warm seasons, thermal low pressure is rapt to ward in the high latitude, and severe dryness of the area is also due to the fact that the dusty phenomenon is intensified in the area. Dust storm occurrence in the summer due to bareness of the land, transparency of the atmosphere, dryness of the air and the vast plains, which can reduce the formation of local instability in the case of a sharp rise in air temperature. The dispersal of deserts and sand sea is mainly in the northwest of Khuzestan province, especially in Fakkeh and Moussan which are located in the western borders of Iran with Iraq, which cover most of the Azadegan plain and west of the Karkheh and Mollasani and Maroon Rivers, and ultimately end in the Omidiyeh and Aghajari regions. Results show that the border between Syria and northwest Iraq, west and southwest of Iraq to east and northeast of Saudi Arabia are the main sources of dust in the studied region . Synoptic conditions considering simultaneously with the occurrence of dust storms showed the significant role of cyclonic systems in the occurrence and transfer of this phenomenon. With the phenomenon occurrence during the warm period, the significant strengthening in low pressure of Iraq along with the trough formation in Zagros causes the formation and transfer of dust towards Southwest Iran. Simulation studies of dust particles movement paths have shown that most of the paths are from the northern and central parts of Iraq and Syria and the source of dust storms are deserts and dry regions of the northern and central parts of Iraq and Syria. In addition, the study of the transmission paths of particles in dust storms indicates the presence of a lower level jet, which causes horizontal displacement of dust particles in a shallow layer and prevents its vertical propagation in the higher layers of the atmosphere. In general, although the dust phenomenon is transnational and uncontrollable, it can introduce limitations in terms of circulation patterns and statistical properties at different time intervals to the different planners via its time and scope which will necessitate appropriate programs for combating and adaptation.