Maryam Arjmand; Alireza Rashki; Hossein Sargazi
Abstract
Extended Abstract Introduction Dust cycles are an integral part of the Earth system, which emits about 2000 tons of dust every year (Shao et al., 2011) and plays an important role in the global climate changes (Park & Jong, 2008). The frequency of dust events in the arid and semi-arid regions is ...
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Extended Abstract Introduction Dust cycles are an integral part of the Earth system, which emits about 2000 tons of dust every year (Shao et al., 2011) and plays an important role in the global climate changes (Park & Jong, 2008). The frequency of dust events in the arid and semi-arid regions is much higher, meanwhile, dried lakes have the largest ration in dust emission (Goudie and Middleton, 2006). Hamoun e Jazmurian is a dried lake located in an homonymous topographic-low basin in southeast Iran and a main source for high dust emissions under favorable weather conditions, but so far limited studies have been carried out in this area, especially on dust. Remote sensing provides useful information about spatiotemporal variability of dust storms over the arid environment of the world. So the present study examines the spatiotemporal variability of dust activity over the region by identifying the dust events from the satellite data. Materials & Methods In this work, spatial and temporal variability of dust aerosol were analyzed over the arid environment of Jazmurian region and surroundings located on southeast of Iran by means of monthly mean data, including Absorption Aerosol Index (AAI), values products of TOMS-Nimbus7 (N7) (1979-1984), TOMS-Earth Probe (EP)(1990-2005) and OMI (2005-2014) as well as Deep Blue AOD of MODIS-Terra (2000-2007) and MODIS-Aqua(2002-2014) and Aerosol Optical Depth (AOD555nm) of MISR (2000-2013). Results & Discussion The results indicated that several hot points of dust including Sistan/Hamoun, Rootak, a region in Pakistan near the border with Iran, Makran coast, Gwadar Bay ion the southeast corner of Iran and the Jazmurian region. Overall, the annual trend of both AAI and AOD values obtained from all sensors, are increasing during the periods expect MODIS retrievals which has negative partial amounts, the time periods of 2002-2004, 2008-2009 and 2011-2012 are the peak of dust storms over the Jazmurian region because of human activities and severe droughts. Seasonal variations of AAI and AOD values showed the major dust activities occur during spring and summer and it is minimum in autumn over Jazmurian region. high activity of dust storms are in four months of May, June, July and August and low in the four months of November, December, January and February Conclusion Hamoun e Jazmourian is one of the active dust emission regions in south east of Iran. The amount of dust and affected areas have increased in recent years. Severe droughts in recent years and numerous dam construction are one of the main factors of dust emission increase in this region.
Masoud Torabi Azad; Kamran Lari; Faramarz Rostaei
Abstract
In this research, the large-scale currents have been investigated using field data of the Caspian Sea temperature, salinity and density at the stations near west of the South Caspian, related to two field patrols. The geostrophic current is created due to the balance of the gradient pressure force and ...
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In this research, the large-scale currents have been investigated using field data of the Caspian Sea temperature, salinity and density at the stations near west of the South Caspian, related to two field patrols. The geostrophic current is created due to the balance of the gradient pressure force and theCoriolisEffect, and is the major factor in the creation of large-scale currents. After analyzing the data, the speed and direction of these types of currents were calculated using satellite imagery.These images were extracted from Aviso satellite with a spatial resolution 0.25 degrees.The calculations for the five vertical sections in the westpart of the South Caspian Sea werecarried out using Excel software and the depth profile of the geostrophic currents speed was obtained speed in each of these sections.In the Southwestern part of theCaspian, the average velocity of these currents for field data was calculated to be 5.85 and 15 cm /s is for the summer and winter respectively. The direction of these currents was also obtained to be 285 in the summer and 44 in the winter. With regard to the satellite images, counterclockwise currents up to 4.5 cm/s velocities and, eastward counterclockwise currents at the velocities of 8 cm/s are observed in the summer and in the winter respectively. The value of the currents velocity (the magnitude of the vectors) indicates that the average currentsvelocity is higher in the winter. One of the reason for this is due to the difference in density caused by the increase in rivers flow rate (especially the Volga), precipitation, wind, etc.
Mojtaba Fathi; Alireza Ma'manpush
Volume 18, Issue 72 , February 2010, , Pages 71-74
Abstract
Achieving stable agricultural production with proper profitability and, at the same time, preserving the environment from destructive effects of chemical fertilizers is not possible without taking the changes in farm’s soil and plant growth into account. The division of the farm into management ...
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Achieving stable agricultural production with proper profitability and, at the same time, preserving the environment from destructive effects of chemical fertilizers is not possible without taking the changes in farm’s soil and plant growth into account. The division of the farm into management sections is carried out in a variety of ways. Concentrated sampling of plants and soil, preparation of contour line maps of its features, and the use of aerial (installed on airplanes) and satellite sensors are among these methods. In developing countries, access to high resolution satellite data is not feasible due to economic and security reasons. However, satellite data with smaller scale is partially able to make the division of the management sections in the farm according to the state of plant growth possible. In this study, the possibility of dividing in-farm management sections based on the NDVI index calculated from the reflection intensity at Landsat 7 satellite wavelengths has been investigated. The NDVI map provides the possibility of dividing farm sections, calculation of the cropping area of each product, and the division of sections with different growth. The coefficient of variation of the NDVI growth index in the 10 hectare farm scale was about 11.5% and was significant. The observable growth rate of the field and the growth rate estimated according to the NDVI index field show agreement.
