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Zoning of Dust Hotspots and Investigation of their Formation Factors

Mohandes Samani, Sara | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 53626 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Tajrishy, Massoud
  7. Abstract:
  8. Identification of dust storm hotspots using high resolution 1 km MODIS Aerosol Optical Depth (AOD) data obtained by MAIAC algorithm for a region including Iran and its neighbors, is one of the objectives of the present study. By implementing three important statistics on AOD and averaging over the last decade time period (2009-2019), dust sources of Iran, Iraq, Syria, Saudi Arabia, Oman, Afghanistan, and Pakistan were specified. These statistics include frequency of occurrence AOD>0.3, mean and coefficient of variation of aerosol optical depth. The membership rank of source zones in the set of hotspot areas has been obtained by applying the fuzzy logic approach on the three mentioned layers. As a final result, three groups are introduced. The group with a membership rank between 0.18-0.5 as the most hazardous active dust source, has been found in areas such as the east coast of Saudi Arabia (in Ad-Dahna desert), the southern coast of Oman and the Arabian Sea, coasts of Oman Sea and the Persian Gulf especially on the southeastern border of Iran and Iraq, central Iraq, Lake Urmia, Salt Lake located in the Dasht-e-Kavir, Sistan Basin on the border of Iran and Afghanistan, the western coast of Saudi Arabia with the Red Sea and finally some parts of the eastern shores of the Caspian Sea identified in Turkmenistan. Among these, dust sources of the three countries of Iran, Iraq, and Syria were chosen for studies related to land-use and extraction of environmental parameters. The barren land-cover class had the largest extent in all the selected dust sources and especially in Iraq and Syria, it covered more than 60% of the area of the dust sources. Land-use changes in this decade show that the size of shrubs in each source group has increased by at least 20%. However, land-use in some groups did not show significant changes in any of the classes.The environmental parameters of this study include ground surface temperature and Normalized Difference Vegetation Index (NDVI) obtained from MODIS and LANDSAT 7 surface reflectance images respectively, precipitation obtained by PERSIANN Climate Data Record, air temperature, wind speed, soil surface moisture, and evapotranspiration flux is derived from GLDAS simulated data. Among these seven parameters, three key components were extracted by performing the Principal Component Analysis (PCA) in the GIS environment for each source group. The purpose of this analysis is to select important data distributions so as to reduce the interdependence between parameters. The assumption of linearity is one of the main foundations of the present study and after selecting a component that has a stronger spatial correlation with the frequency of occurrence and the average AOD, its correlation with seven initial parameters was investigated, and finally, the two variables of surface temperature and soil surface moisture was recognized as most important factors for all selected hotspots. Investigating the relationship between time series of important variables related to each source group and frequency of AOD>0.3 has demonstrated the overlapping role of parameters in their effect on dust emission statistics, gap existence between temporal changes in parameters such as soil surface moisture, and their effect on changes in AOD frequency and at the end, the complexity of the relationship between climatic parameters and dust activity statistics
  9. Keywords:
  10. Meteorological Parameters ; Soil Moisture ; Optical Depth ; Moderate Resolution Imaging Spectroradiometer (MODIS)Data ; Dust Outbreaks ; Dust Sources ; Dust Source Zoning

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