Detecting and routing of dust event using remote sensing and numerical modeling inIsfahan Province

The phenomenon of dust in Iran is a serious risk that caused major problems for the environment and human health. Research have shown that the frequency and severity of these storms have increased in recent years. In addition, numerical weather models alone are not capable of storm detection, which requires the use of dust detection methods based on data remote sensing.The purpose of this research was to analyze the statistical data and identify the days with dust, the source of dust entering the Isfahan area, and identify the route of its movement.

Dust data were collected from the selected station in the study area with a suitable sta-tistical period from the meteorological organization on a daily basis for 8 hours, in the form of special codes for the period of 2010 to 2013, which were processed and analyzed using statistical methods. In order to zoning the dust abundance in the province, the IDW method was used to interpolate and transform point-to-area data. The dispersion zonation map for the 2010-2013 period was mapped using the GIS software.In order to visualize the dust phenomenon, after the geometric correction of the images, the radian values of the images were converted to brightness temperature using the Planck function. Corrections and processing of images were done in ENVI software. Due to the large influence of dust particles on the reflection and brightness temperature of the 31 and 32 bands of the material, the difference between the two bands’ brightness was used to represent the dust mass. Also, to prevent the detection of cloud areas, the threshold of 290 K was applied to the 12-micron range. HYSPLIT La-grangian model was used to trace the dust particles’ path.

Results and disscussion:

The results of this study indicated that a total of 1467 days of dust phenomena were reported for selected stations from 2010 to 2013, in which the Naein station was the largest with 634 days and the Kashan station had the least frequency of dust with 50 days. The results also indicated the greatest frequency percentage occurred in May, June and April and the lowest frequency percentages in December and January. The frequency of monthly dust data showed that 44.57% of the total dust incidence occurred in April, May and June and 32.4% in December and January. Accordingly, it can be concluded that monthly dust changes occur frequently in the region consistent with the regional climate during all months of the year. The zoning results showed that during the study period, the southeast of the province, especially Naien station, had the highest incidence of dust. The application of brightness temperature and temperature threshold in order to separate the dust from the terrain, especially in areas with backlight, was helpful in the detection of dust. The results of the tracking showed that the main route for the transfer of dust to the studied area was southwest-northeast.

In general, according to satellite images on the first and the peak day of dust, the main sources of dust in the region were northern Arabian deserts. Based on the results obtained from image processing and the output of the model, the northern part of Saudi Arabia and the southwest-northeast route were the origin and main route of dust entering Isfahan.