Mehdi Jafari; Gholamreza Zehtabian; Tayebeh Mesbahzadeh
Volume 25, Issue 4 , February 2019, , Pages 863-876
Abstract
In this study, the dust phenomenon was studied at the station of Isfahan temporally and spatially. For this purpose, the data, the time and date of the observation, the direction and wind speed, and the current weather condition were prepared. After extraction of dust codes (06 ...
Read More
In this study, the dust phenomenon was studied at the station of Isfahan temporally and spatially. For this purpose, the data, the time and date of the observation, the direction and wind speed, and the current weather condition were prepared. After extraction of dust codes (06 and 07) and statistical analysis of the data related to this phenomenon, the annual and seasonal wind rose and storm rose of the station were mapped using WRplot & WDconvert software during the statistical period of 2013-2002. The results showed that there were 525 days of dust in the region, which was the most frequent in 2012 with 62 days. Also, in May and spring, the highest frequency of dust occurred. The study of wind rose and storm rose annually confirms the formation of wind tunnel on the western-eastern route. The annual dust rose, divided into two meteorological codes 06 and 07, indicates that winds with dust from the Midwest are involved in the transport of suspended particles and formation of local dusts. Seasonal storm rose show the impact of different atmospheric systems throughout the year on the formation of dust phenomena in the region better and more accurately. With the onset of the cold season, the winds with dust are increasing from the northern half to Isfahan and reach the maximum in the winter, but with the start of the hot season, and especially the summer season, it is more intense than east to Isfahan, and from the west almost reaches zero.
Mehdi Jafary; Gholamreza Zehtabian; Amir Houshang Ehsani
Volume 20, Issue 4 , March 2014, , Pages 644-652
Mehdi Jafari; Gholam Reza Zehtabian; Amir Houshang Ehsani
Volume 20, Issue 1 , June 2013, , Pages 72-87
Abstract
Today, remote sensing data can provide the latest information for the study of land cover and land uses These images are of utmost importance due to the providing updated information, variety of forms and the possibility of processing for making land use maps. Determining the location of each land use ...
Read More
Today, remote sensing data can provide the latest information for the study of land cover and land uses These images are of utmost importance due to the providing updated information, variety of forms and the possibility of processing for making land use maps. Determining the location of each land use together with land cover helps managers in making decisions. Also, the current status of the land cover can be studied by using land use maps at different levels. In order to evaluate the ability of multitemporal satellite data of TM and ETM + in land use classification and the effect of the thermal band on increasing the accuracy of the land use maps, Landsat TM digital data relating to the September 27, 1990 and Landsat ETM + digital data of 10 July 2002 from Kashan were analyzed. Initial studies were performed on images in terms of the presence of geometric errors. In order to prepare the images for digital processing, improved operation and image enhancement were applied on the images. Ground truth map was prepared in the same stage. Then, the supervised classification of satellite images with algorithms and different approaches including a variety of bands were tested and the accuracy of each of the methods and approaches were investigated. The results showed that the highest Kappa accuracy in both Landsat TM and ETM + with all the bands were 86.34 and 83.21, respectively. While the elimination of the thermal band decreases the accuracy to 82.46 and 79.93 % The results of this study showed that using thermal bonding caused an increase of 4 percent in Kappa accuracy, and the highest accuracy was occurred in the classes of clay plains, flood plains, mountains and puffy salt lands. Therefore, despite the lower spectral resolution, the use of thermal bonding is recommended in such studies.