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Undoubtedly, Egypt is one of the most air polluted countries in the world. It suffers from high ambient concentrations of atmospheric pollutants including particulates (PM), carbon monoxide, nitrogen oxides, ozone and sulfur. The pollution phenomenon locally known as “Black cloud” over Cairo has been attributed to many reasons among which are biomass burning, local emission and long range transport during the fall season.
The anthropic factors affecting black cloud over Niledelta.
Nile delta and Great Cairo have witnessed different seasonal climate systems that are highly influenced by sand and dust storms coming from the western desert as well as local, increasing anthropogenic activities. As a result, it is characterized by a complicated meteorology that varies in the different times of the year. This study suggests that the pollution during the black cloud episode is the worst on human beings in addition to its effect on the local climate. During winter the climate is generally cold, humid and rainy; while during the summer season the weather is hot and dry.
On the other hand, Alexandria as a Mediterranean city has better climate conditions, yet being the largest industrial city, with ~55% of total Egyptian industry, suffers from pollution episodes, which are, however, still not as intense as the ones usually observed over Cairo. El-Metwally et al., (2008) and El-Askary et al., (2009) revealed that Cairo’s and Alexandria’s aerosol includes; “background pollution’’, ‘‘pollution-like’’, and ‘‘dust-like’’ components. Generally speaking, Egypt is influenced by the regional scale trade wind system that is enhanced during the warm period of the year resulting in winds over Egypt are from North supporting the sea-breezes along the Mediterranean coastline.
However, the author is worried by the continuous spate of pollution and other imminent environmental challenges posed by human and industrial activities in the Nile delta and Great Cairo. It should be noticed that aerosol from natural sources, such as sea salt and desert dust; contain larger particles than aerosols were emanating from human-produced combustion sources such as agricultural and deforestation burning or urban/industrial pollution. The mature MODIS algorithm includes aerosol optical thickness at several wavelengths, information on particle size, and aerosol-reflected flux at the top of the atmosphere, which is expected to be more accurate than the optical thickness retrievals.
The research conclusively revealed that The MODIS aerosol product is used to study aerosol climatology, sources and sinks of specific aerosol types (e.g., biomass burning aerosol or black cloud over Nile delta), interaction of aerosols with clouds, the hydrological cycle and atmospheric dynamics, and atmospheric corrections of remotely sensed surface reflectance over the land.
Hossam Ismael：Geography and GIS Department, Faculty of Arts, Assiut University, New Valley Branch, Egypt