Dust events in southwestern Iran: Estimation of PM10 concentration based on horizontal visibility during dust events

Abstract

AbstractDue to the lack of air quality data in many regions across the globe, determination of PM10 concentration based on horizontal visibility is of considerable importance. This study aims to obtain the best empirical equation to estimate PM10 concentration in southwestern Iran during dust events based on horizontal visibility. By analysing long‐term (2000–2019) meteorological data, a statistically significant correlation is found between horizontal visibility and PM10 concentration in southwestern Iran. A distinct seasonal pattern in the frequency of dust events is observed, with the highest and lowest frequency in June and December, respectively. The diurnal variation is also identified in the frequency of dust events in southwestern Iran, with a higher frequency in the afternoon during which thermal instability is maximum, but a relatively lower frequency at night when the atmosphere is generally thermally stable. A relatively high year‐to‐year variability in the frequency of dust events is observed in southwestern Iran, suggesting a large contribution of natural internal climate variability. However, the frequency of dust events has not changed significantly during the period 2000–2019. Analysis of three dust events in southwestern Iran in winter and the long‐term wind rose in Ahvaz indicates that dust events in southwestern Iran are mainly associated with strong northwesterly winds and transport of dust from Iraq. Strong southerly winds and activation of local sources or transport of dust from Saudi Arabia also occasionally contribute. PM10 concentrations in southwestern Iran during dust events are estimated based on horizontal visibility using eight different equations, three of which are introduced in this study. Results show that exponential equations provide a more accurate estimation of PM10 concentration in southwestern Iran during dust events when horizontal visibility is less than 500 m, while power equations perform better when horizontal visibility is greater than 500 m.