Day by day evolution of a vigorous two wave Saharan dust storm – Thermal and air quality impacts

Abstract

This paper conducts a day-by-day analysis of an intense Saharan dust storm that struck Athens (Greece) during April 2008 and consisted of two main dust waves (the first from 10/04/2008 to 14/04/2008 and the second from 19/04/2008 to 22/04/2008). Daily satellite data (1º × 1º resolution) of aerosol optical depth (AOD) were used, in order to follow the course of two dust plumes originated in North Africa through the eastern Mediterranean. Ground based measurements of particle concentrations (PM₁₀ and PM_2.5) and meteorological parameters (wind speed, air temperature, relative humidity and visibility) were also studied. The time intervals before and after each dust wave were taken under consideration, aiming to identify the atmospheric circulation that generated the dust storm and also the clearing mechanisms that removed the African dust from the Athenian atmosphere. Backward air mass trajectories isolated the source of the two dust plumes over Libya and Tunisia, where extreme daily AOD values were recorded. The transportation of dust in the Greek region, during both dust waves, was associated with south westerlies airflows attributed to the advent of low pressure systems from the Atlantic. The impact of both dust waves in Athens was interrupted by the prevalence of a strong north westerlies air stream, which carried the particles eastwards through Turkey, Cyprus and the Middle East. During this dust event, air quality in Athens was severely downgraded, but no thermal discomfort has occurred, according to the estimation of a Pollution Index (PI) and a Discomfort Index (DI), respectively. A drop in visibility was also reported.