Investigation of thermal inversions as a major contributer to the Black cloud episodes over Cairo

Aerosol index measurements from the total ozone monitoring spectroradiometer (TOMS) revealed the aerosol concentrations scattering properties to the UV radiations during the season well known to the locals and named as the black cloud season. Aerosol optical depth (AOD) obtained from moderate resolution imaging spectroradiometer (MODIS) showed the high aerosol concentrations during October of each year. Vertical temperature profiles obtained from the atmospheric infrared sounder (AIRS) level-3 daily global girded data product during the months of September and October over Cairo are analyzed. AIRS, is one of the most advanced space-based atmospheric sounding systems. These profiles reveal the occurrence of an inversion layer in the lower troposphere in the vicinity of less than 1 km above the ground surface over Cairo. Meanwhile, over the same time period, a regular negative temperature gradient is observed over Alexandria, located 250 km away from Cairo.