Investigation of inversion characteristics in atmospheric boundary layer: a case study of Tehran, Iran

Abstract

Atmospheric stability originated from temperature inversion is a main challenge in the metropolitan areas especially during the cold seasons. This study aims to investigate temperature inversion characteristics of atmospheric boundary layer in Tehran within 2010–2014. Some parameters such as height, layer thickness, air pressure and temperature difference between base and top of inversion layer were studied in order to detect radiation and subsidence inversions. The results showed that among total 1138 days with inversion events about 1015 and 123 days were classified as radiation and subsidence inversions, respectively. According to an empirical equation, daily inversion intensity was categorized from weak to severe. The most inversions occurred in summer while, the least happened in spring. However, the most severe intensity values were recorded in autumn with 58 days, while the weakest values were recorded in spring with 170 days. Height of the base level of the inversion layer in all autumn seasons is in lowest distance from Earth surface. Hence, environmental impact of the inversion events in autumn is more intense in Tehran.