الفهرس 
Aerosol parameter classificationOnly 14 pages are availabe for public view
 |  | from | 243 |  |  |
| | | from | 243 | | |
Abstract
This study is based on an analysis of available meteorological data from ground stations in addition to AERONET data.
Recent studies using year (2004–2005) satellite (including Moderate Resolution Imaging Spectroradiometer (MODIS) and ground Aerosol Robotic Network (AERONET) data show strong seasonal variability of aerosol optical depth (AOD) with maximum aerosol loading (1> τa> 0.3) during spring season. A number of major dust storms, originating from western arid and desert regions (west Desert), affect the whole during the season (March–May). Pronounced changes in the aerosol optical parameters, derived from AERONET, have been observed over Cairo University (30o 01\ N, 31o .12\ E) during dust storm events (2004–2005). These measurements were recorded by sunphotometer that measures direct sunlight over a narrow range of wavelengths, some sunphotometer use ”interference filters” to make a sharp cut off to ensure the measurement at selected of wavelength.
Monthly average values of aerosol optical depth (AOD) showed a pronounced temporal trend, with a maximum AOD during winter and the transition season (spring) at two sites urban areas.
Variation of Angstrom exponent (α) with the AOD was clear and the α- value depends on the spectral range used in its determination.
The number of occurrence distribution measurements are carried out at seven stations in Egypt some of these stations are urban/industrial areas, and other is an agricultural area covering the period from Jan 1968 to Dec 2005.
The dust model includes dust emission as a function of (vegetation cover- soil type and texture – soil wetness – friction velocity), dust deposition (wet and dry), horizontal and vertical advection and vertical diffusion through an improved formulation of PBL. One case with very remarkable sandstorms has been described and investigated through this study. The model output for 72 hours were validated and verified with satellite images and visibility as actual data. In addition, the aerodynamic parameters (friction velocity, wind speed and vertical motion for compression) are the main factors in the dust emission. The author concludes that:
1) The model had an excellent performance in predicting dust over Egypt during the forecast period when compared with the satellite images and actual visibility.
2) The dust storm events are extremely associated with the cold front.