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Showing 4 results for Modis
Koohzad Raispour,
year 8, Issue 1 (5-2018)
year 8, Issue 1 (5-2018)
Abstract
Extended abstract
1- Introduction
Dust storms are a kind of severe natural disaster indust source regions, which have a negative impact on human health, industrial products and activities. Iran is a dry and low water country, the coincidence of this situation and its position in the global rebound belt has brought about very bad conditions. Repeaters in recent years have been affected by the severity and frequency of major events in Iran and, in terms of environmental issues, studying and managing the reduction of its effects is a priority.
In recent years, these events have been the main hazards in areas of South-west Iran. Several complex dust storms have recently occurred in the southwestern part of Iran. Detecting the spatial distribution of dust storms in the deposition regions is an essential step for managing this natural and human-induced crisis. Land measurement and remote sensing techniques are currently two of the most important methods for monitoring dust storms. Traditional reference land measurement methods have little spatial and temporal resolutions, so they can not properly monitor and anticipate dust storms. Due to rapid changes in the nature and location of dust storms, there are limitations in monitoring and relating measurements. Meteorological numerical models can not detect dust storms alone. Today, remote sensing technology is known for providing multiple global and regional images with time, spatial and spectral scales as a useful tool for monitoring , measuring and harvesting dust properties. Also, remote sensing can monitor the range and scope of dust storms, their degree of intensity and their route of movement. In this research, by using MODIS images and applying methods of applying the dust algorithm, dust was monitored. This study aimed to investigate the performance of the Normalized Differences Dust Index (NDDI) applied to MODIS data (01/11/2017) for detection of dust storms in the Southwest of Iran.
2- Methodology
Monitoring disasters properly is a necessary requirement. In this study, the dust event that took place in November 2017, based on Terra / MODIS remote-sensing indices, has been monitored by ECMWF database and synoptic analyzes from the NCEP / NCAR database. Therefore, according to the characteristics of reflection and absorption of the aforementioned dust event, the resulting dust range and its intensity are extracted accurately using the NDDI index and their degree of intensity is estimated. The NDDI equation is as follows:
Here b3 and b7 reflect the band of three and the band of seven of the MODIS bands.
3- Results
Based on the results, the dust pollution eventually increased the air pollution in some areas of Khuzestan, Ilam, Kermanshah and Kurdistan provineces, and greatly reduced the horizontal visibility. The results also showed that the dust storm began from the day in which it started from deserts in the northeast of Saudi Arabia, and after spreading to the vast deserts of southern Syria, northern Arabia and west of Iraq, moving eastward to southwest Iran has moved. The maximum spatial distribution of dust is in Khuzestan province. After the Khuzestan province, western parts of Ilam, Kermanshah, Kurdistan and Zanjan provinces are located in the next rows.
4- Discussion & Conclusions
The results of the satellite monitoring show a great deal of agreement with monitoring the meteorological conditions at the time of the occurrence of dust. The results also showed that the atmospheric conditions affecting the Atmosphere borderland in creating turbulence and transferring dust from deserts in northern Arabia, east and south of Syria, west and south of Iraq to southwest Iran have an important and undeniable nature. So, in the dusty event studied, unstable airborne conditions, such as the presence of very deep wrecks, a strong wheel with a significant positive tau in the wake axis, along with instability and climbing the air, made the region an unrestrained and turbulent situation over adjacent Arabian desert areas Provided with the West of Iran and provided very favorable conditions for harvesting, transportation and transportation to the western and southeastern parts of Iran.
Zahra Yarmoradi, Behrooz Nasiri, Gholam Hasan Mohammadi, Mostafa Karampoor,
year 9, Issue 1 (5-2019)
year 9, Issue 1 (5-2019)
Abstract
Extended abstract
1- Introduction
A dust storm is one of the biggest serious environmental problems in the arid and semi-arid regions of the world, causing irreparable damages to farms, facilities, roads, traffic and transportation every year and respitory problems by contaminating the air. Due to the geographic location of Iran which is in the arid and semi-arid belt of the world, the country is frequently exposed to local and synoptic dust systems. Considering the increasing occurrence of dust in the coming years, drought and climate changes and the emergence of desert zones, the study of this phenomenon is considered important and should be studied by using scientific researches to identify the factors affecting the occurrence of this phenomenon and dust source areas. The main purpose of this research is to identify the sources and also track the dust route entering the east of Iran using the HYSPLIT model, satellite images and synoptic analysis.
2- Methodology
In this study, At first, warm season dust storms were studied by using weather data, phenomenal code and horizontal visibility. Then, the storm from August 12 to 14, 2018, was recorded using weather data for East stations and horizontal visibility. For more accuracy, MODIS images of the storm wave on this day were identified and the surface dust concentration was confirmed using the AOD Index. Then, using the European Center for Average Meteorological Data (ECMWF) with a spatial resolution of 0.25 * 0.25, sea level pressure (SLP), temperature, direction and wind speed, and geopotential height At 850, 500 and 250 levels, jet streams were investigated and The synoptic factor of the dust storm was determined. In the next step, using the HYSPLIT model, the path of motion of particles and their source were determined at three levels of 500, 1000 and 1500 meters for 24 hours before the storm. The meteorological data of the model was obtained from a 0.5 degreess GDAS.
3- Results
The intensity and extent of the dust storm from August 12 to 14, 2018 showed that its horizontal visibility had been decreased to less than 200 meters across stations in eastern half areas of Iran. On this day, the dry bed of Hamoun, Pozak, Saberi and Hirmand, Afghanistan's plains have been contributed to nourish the storm. The results of synoptic studies showed that when there is a high pressure independent cell in the north-east of Afghanistan and north-east of Iran as well as a low-pressure cell in the southwestern part of Afghanistan, a severe gradient is made between these regions that causes the wind speed at ground level to be more than 14 meters per second. The severe pressure and temperature differences in the region, the lack of humidity and the high radiation angle have drove the dust of deserts outside the northern and eastern borders toward the region, and this area has been under the Azores subtropical high pressure, which its blockage at high levels leads the persistence of dust for three days in eastern Iran. The results of the model also showed that more than 90% of the dust entry routes to the east enters the eastern part of Iran from the deserts of Turkmenistan, Khazakhistan and Afghanistan.
4- Discussion & Conclusions
Due to 120-day winds, low humidity, poor vegetation and dry regional substrates, the eastern part of Iran is prone to the frequent occurrence of dusty phenomena. Based on satellite images and AOD index, the storm has formed in the desert region of Turkmenistan and has been expanding to eastern Iran. According to the synoptic study of the warm period of the dust storm in the east, the upper levels of the Iranian plateau are under the control of the Azores high pressure and on the ground surface, the thermal low is also increasing in the eastern half. When two strong low-pressure nuclei with a 990 hp center in southeastern Afghanistan and southeastern Pakistan were deployed so that its tabs penetrated into the studied region and progressed to the Mediterranean, it created the appropriate conditions for climbing a huge amount of dust into the air that in the case of dryness of the area and north-northwestern and northeastern flow of the upper levels, this phenomenon intensified and moved to the eastern part of Iran. At high atmospheric levels, due to air stability and blocking events, as well as air stagnation, the dust is more durable temporally and the process of bringing it down to the ground surface will last longer days. The results of the HYSPLITE modeling output also showed that the source of dust of the eastern half of Iran in the storm studied enter the studied area from the deserts of Turkmenistan and northwest of Afghanistan and Khazakhistan with the north, northwest and northeastern directions up to 90 percent. In all cases, the results of the model are compared with and confirmed by satellite and synoptic studies.
1- Introduction
A dust storm is one of the biggest serious environmental problems in the arid and semi-arid regions of the world, causing irreparable damages to farms, facilities, roads, traffic and transportation every year and respitory problems by contaminating the air. Due to the geographic location of Iran which is in the arid and semi-arid belt of the world, the country is frequently exposed to local and synoptic dust systems. Considering the increasing occurrence of dust in the coming years, drought and climate changes and the emergence of desert zones, the study of this phenomenon is considered important and should be studied by using scientific researches to identify the factors affecting the occurrence of this phenomenon and dust source areas. The main purpose of this research is to identify the sources and also track the dust route entering the east of Iran using the HYSPLIT model, satellite images and synoptic analysis.
2- Methodology
In this study, At first, warm season dust storms were studied by using weather data, phenomenal code and horizontal visibility. Then, the storm from August 12 to 14, 2018, was recorded using weather data for East stations and horizontal visibility. For more accuracy, MODIS images of the storm wave on this day were identified and the surface dust concentration was confirmed using the AOD Index. Then, using the European Center for Average Meteorological Data (ECMWF) with a spatial resolution of 0.25 * 0.25, sea level pressure (SLP), temperature, direction and wind speed, and geopotential height At 850, 500 and 250 levels, jet streams were investigated and The synoptic factor of the dust storm was determined. In the next step, using the HYSPLIT model, the path of motion of particles and their source were determined at three levels of 500, 1000 and 1500 meters for 24 hours before the storm. The meteorological data of the model was obtained from a 0.5 degreess GDAS.
3- Results
The intensity and extent of the dust storm from August 12 to 14, 2018 showed that its horizontal visibility had been decreased to less than 200 meters across stations in eastern half areas of Iran. On this day, the dry bed of Hamoun, Pozak, Saberi and Hirmand, Afghanistan's plains have been contributed to nourish the storm. The results of synoptic studies showed that when there is a high pressure independent cell in the north-east of Afghanistan and north-east of Iran as well as a low-pressure cell in the southwestern part of Afghanistan, a severe gradient is made between these regions that causes the wind speed at ground level to be more than 14 meters per second. The severe pressure and temperature differences in the region, the lack of humidity and the high radiation angle have drove the dust of deserts outside the northern and eastern borders toward the region, and this area has been under the Azores subtropical high pressure, which its blockage at high levels leads the persistence of dust for three days in eastern Iran. The results of the model also showed that more than 90% of the dust entry routes to the east enters the eastern part of Iran from the deserts of Turkmenistan, Khazakhistan and Afghanistan.
4- Discussion & Conclusions
Due to 120-day winds, low humidity, poor vegetation and dry regional substrates, the eastern part of Iran is prone to the frequent occurrence of dusty phenomena. Based on satellite images and AOD index, the storm has formed in the desert region of Turkmenistan and has been expanding to eastern Iran. According to the synoptic study of the warm period of the dust storm in the east, the upper levels of the Iranian plateau are under the control of the Azores high pressure and on the ground surface, the thermal low is also increasing in the eastern half. When two strong low-pressure nuclei with a 990 hp center in southeastern Afghanistan and southeastern Pakistan were deployed so that its tabs penetrated into the studied region and progressed to the Mediterranean, it created the appropriate conditions for climbing a huge amount of dust into the air that in the case of dryness of the area and north-northwestern and northeastern flow of the upper levels, this phenomenon intensified and moved to the eastern part of Iran. At high atmospheric levels, due to air stability and blocking events, as well as air stagnation, the dust is more durable temporally and the process of bringing it down to the ground surface will last longer days. The results of the HYSPLITE modeling output also showed that the source of dust of the eastern half of Iran in the storm studied enter the studied area from the deserts of Turkmenistan and northwest of Afghanistan and Khazakhistan with the north, northwest and northeastern directions up to 90 percent. In all cases, the results of the model are compared with and confirmed by satellite and synoptic studies.
Moien Jahantigh, Mansour Jahantigh, Fazel Iranmanesh,
year 13, Issue 3 (10-2023)
year 13, Issue 3 (10-2023)
Abstract
1- Introduction
Wind erosion is affected by climate change and several droughts have caused environmental degradation in arid regions. This process causes sand and dust storm (SDS) phenomenon which is one of the most important challenges in fragile areas. This phenomenon is harmful for human health and causes socio-economic problems. Over the past two decades, SDS have been increasing in Iran, particularly in the south-east of the country. Therefore, in order to manage this environmental phenomenon in arid areas, it is an urgent need to identify the dust storm sources. The changes of factors such as vegetation, soil moisture, slope, land temperature, and geological units have effective roles in the occurrence of dust storms. So, investigating the changes in these factors is an effective solution to identify dust storm sources. In this regard, using remote sensing data is one of the effective methods for the detection and mapping of dust storms resource, which combined with field methods, provides a coherent approach to manage and control this phenomenon. This study aimed to identify dust sources and storms in the southeast of Iran with emphasis on the Sistan dust storm by using field work and remote sensing data.
2- Methodology
The study area is located in the south east of Iran and contains some of the border areas of Iran and Afghanistan (including some parts of the south Khorasan and Sistan and Baluchestan province in Iran as well as Farah and Nimroz province in Afghanistan with coordinates of 60˚ 16′ - 61˚ 36′ east longitude and 29˚ 8′ - 32˚ 32′ north latitude). In north of the study area, the mountainous and low-altitude areas are intertwined but the southern area is mostly flat and lacks topography and natural features. The most important characteristics of this area is 120-day winds, which sometimes reach speeds of more than 120 kilometers per hour and is accompanied by high intensity of sand and dust storms. In this study, to identify dust storm sources, the combination of remote sensing, field study and wind analysis methods are used. To achieve this purpose, at first effective factors in the occurrence of dust storms such as vegetation, soil moisture, slope, land temperature, and geological units were prepared. In this regard, by using Modis satellite images, map of vegetation, soil moisture and land temperature were prepared by applying Soil Adjusted Vegetation Index (SAVI), integrating temperature vegetation dryness index (TVDI) and Land surface temperature (LST), respectively. Also slope map (using Aster satellite) and geological units were prepared. In the next stage, the fuzzy logic method was employed to combine layers and prepare the map of dust storms source, which is assessed by an error matrix and available dust source map. Detection of sand dust storms were performed by using BTD dust detection indicator. For winds analysis, we used WRplot view 8 Software. In the field study, several dust storms sources were determined and their characteristics were recorded.
3- Results
The results showed that the ranges of SAVI index are + 0.6 to -1 and the highest amount of this index coordinate with highest soil moisture (TVDI) and the lowest land surface temperature (LST) area. This area is mostly related to rangeland, combination of wetland-rangeland, hand-planted forests and agricultural lands. The amount of SAVI index and soil moisture reaches its minimum value in the salt marsh lands, abandoned agricultural lands, desert areas and degraded rangeland. By merging the layers and preparing the map of dust storm sources, it was found that the critical dust storms resources coordinate with high land surface temperature and low vegetation and soil moisture areas. In addition, the highest dust source area is in the slopes of 0 to 4 % with geological units such as playa deposits, eolian deposits, alluvium sediment and wet playa deposit. According to the results, the incoming dust storms into the study area come from the east and southeast of south Khorasan province in Iran and the southwest of Farah province in Afghanistan.
4- Discussion & Conclusions
In this study by using effective factors including vegetation, soil moisture, land surface temperature, slope and geological units, the sources of dust production were identified. According to the results, poor vegetation and low soil moisture in flat areas with sensitive formations are the key factors to create dust storm resources in the study area. Also, the most important active hot-spot areas for dust storm is concentrated in the southwest of Afghanistan and north of sistan region (dry lake bed of Hamoon). Therefore, it can be concluded that using satellite images and the studied factors, the dust sources can be properly identified. Furthermore, by using Time series images of modis and the updated dust source maps, a coherent approach can be provided in order to manage and control this phenomenon.
Zohre Ebrahimi-Khusfi, Ablfazl Ranjbar,
year 14, Issue 3 (10-2024)
year 14, Issue 3 (10-2024)
Abstract
1- Introduction
Dust aerosols have adverse effects on public health, air quality, and the environment; therefore, continuous monitoring of their spatio-temporal changes in different regions, especially arid and semi-arid regions, is very important. Considering the vast spatial extent of Kerman province, the inappropriate distribution of air pollutant measurement stations, a number of synoptic stations, as well as the large area of the province and the different climatic and biological diversity; the use of remote sensing techniques and especially the use of Aerosol optical depth (AOD) index of the MODIS sensor can be one of the appropriate tools to analyze and investigate the trend of temporal changes and the pattern of spatial distribution of dust particles in different regions of this province. This study has been carried out with the main purpose of analyzing the changes in dust aerosols based on the average monthly, seasonal and annual values of aerosol optical depth in different regions of Kerman province during the period from 2000 to 2022, so that while knowing the state of these changes, the high-risk areas of dust production in recent decades should also be identified.
2-Methodology
In the present study, the MODIS sensor aerosol optical depth index product (MCD19A2) was used to analyze the trend of changes in dust aerosols in different regions of Kerman province. In order to validate this product, the average daily horizontal visibility recorded on the days of dust events was used. The data related to the MCD19A2 satellite product was downloaded through programming in the Google Earth Engine environment for different cities of Kerman province in the period from 2000 to 2022. After filtering the dusty days (AOD>0.5), the average values of the mentioned index on monthly, seasonal and annual time scales were calculated separately for each region. The Mann-Kendall test was then used to analyze the temporal changes of the optical depth of dust aerosols in different regions of Kerman province.
3- Results
Based on the spatial distribution pattern of the air quality, it was found that the air quality of the eastern half in March and April was lower than other areas of the province, while in the central areas, the air pollution was less and the air quality was more favorable. The results of the Mann-Kendall test showed that in June and December, the trend of changes in the dust aerosols optical depth in more than two thirds of Kerman province had a non-significant decrease (Z>-1.96). This is why in November and May, half of the province and in other months more than two-thirds of the province have experienced incremental changes over the last 23 years. The pattern of long-term average spatial changes of the optical depth of aerosols on a seasonal scale showed that Kerman province was more affected by aerosols in the spring and summer seasons. Maximum dust pollution has occurred from Raver to Rigan, Jiroft to Manojan, Sirjan and Anar cities. The mentioned areas in the cold seasons of the year have also experienced the worst conditions in terms of the presence of aerosols, but their concentration has been significantly lower compared to the warm seasons of the year. The results of the Mann-Kendall test showed that 75% of the cities of Kerman province have faced an increasing-insignificant trend of spring dust events, which has led to an increase in the concentration of aerosols. In summer, these changes were increased in more than 95% of the province's regions, and the most changes were observed in Anar, Baft, Fahraj, Kohnouj, Kohbanan, Orzuiyeh and Rafsanjan. Although in the fall season, about 25% of the regions of the province had a decreasing trend and about 4% had no particular trend, but in more than 70% of the regions of Kerman province, the trend of changes in dust aerosols was an increase, and among the regions with a positive trend, the cities Baft and Jiraft had the worst conditions (Z>1.96). The remarkable result is the rising trend of dust and dust aerosols in all regions of Kerman province during winter, particularly in the cities of Anar, Anbarabad, Baft, Faryab, Ghaleganj, Manojan and Rabor. Although Anbarabad, Baft, Orzuiyeh, Shahrbabak and Sirjan exhibit a stronger annual increase compared to other areas, the rise in AOD changes is evident throughout the province. This 23-year trend indicates that Kerman has not experienced favorable conditions, highlighting the increasing frequency of dust events in this desert region.
4- Discussion & Conclusions
Based on the findings of the analysis of the temporal changes of dust aerosols; the western cities of the province have become more sensitive to the phenomenon of wind erosion compared to the past. This can be a serious threat to the residents of these areas. On the other hand, the increasing trend in the southern and eastern regions highlights the intensification of dust events, contributing to the decline in air quality in the province over recent decades. Considering the intensification of the phenomenon of wind erosion and dust storms in many areas of Kerman province, it is necessary to control this phenomenon in order to increase the health security of the residents of the affected areas. Although the awareness of the spatial and temporal changes of dust aerosols has led to an increase in our understanding of the phenomenon of wind and dust erosion in the province, but in order to prevent, control and reduce the risks caused by the occurrence of this destructive environmental phenomenon, it is necessary to identify the main driving factors of these changes that are suggested to be investigated separately for each city in future researches.
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