Abstract

Dust storms are common meteorological events in arid and semi-arid regions, particularly in Southwest Iran (SWI). Here we study the relation between drought events in Iraq and dust storms in SWI between 2003 and 2018. The HYSPLIT model showed that central and southern Iraq are the main dust sources for SWI. Mean annual aerosol optical depth (AOD) analysis demonstrated that 2008 and 2009 were the dustiest years since 2003 and there is an increased frequency of summertime extreme dust events in the years 2008 and 2009. The Standardized Precipitation Evapotranspiration Index revealed that drought in Iraq significantly affects dust storms in Iran. Similarly, dramatic desiccation of Iraq wetlands has contributed to increasing fall dust events in SWI. AOD in SWI is highly correlated (−0.76) with previous-month vapor pressure deficit (VPD) over Iraq, demonstrating the potential of VPD for dust event forecasting.

Highlights

  • Dust events occur in many parts of the world (Chen et al 2004, Hand et al 2012, Creamean et al 2013, Ishimoto et al 2016), but are more frequent over arid and semi-arid regions (Furman 2016, Khalidy et al 2019)

  • Mean annual aerosol optical depth (AOD) time series over Southwest Iran (SWI) In order to illustrate the fluctuation of dust events in the region, a monthly time series of eight different Moderate Resolution Imaging Spectroradiometer (MODIS) products, averaged over SWI, are plotted for 2003–2018

  • The results show that 2008 and 2009 were the most polluted years in SWI, which is consistent with the study of Sari Sarraf et al (2015), based on the yearly variation of annual means of dust events in Ahvaz weather station during the period of analysis

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Summary

Introduction

Dust events occur in many parts of the world (Chen et al 2004, Hand et al 2012, Creamean et al 2013, Ishimoto et al 2016), but are more frequent over arid and semi-arid regions (Furman 2016, Khalidy et al 2019). The United Nations Environment Program (UNEP) has reported several factors that may exacerbate these events, including the occurrence of droughts in SWI and neighboring countries such as Iraq, the reduction of surface and subsurface soil moisture, removal of vegetation cover, and the development of sedimentary and fine-grained areas (Environment in Iraq: UNEP Progress Report 2003). Human factors such as construction of large dams on rivers leading to the Mesopotamian basin (Iraq) may contribute to the dust events entering western Iran, some of them having crossed the Zagros Mountains in recent years to impact central Iran (Crosbie et al 2014). We will show where most of the SWI dust events come from, quantify relationships between major drought events in Iraq and dust events in SWI, and introduce a satellite-observed variable that can potentially be used for prediction of dust events

AOD data
HYSPLIT model
GDAS model The Global Data Assimilation
SPEI The Standardized Precipitation Evapotranspiration
AIRS Near surface air temperature (T) and relative humidity (RH) are obtained from the Atmospheric Infrared
Mean annual AOD time series over SWI
Trajectory analysis of dust storms in SWI
Extreme dust event frequency analysis over SWI
Monthly AOD over SWI
Drought analysis The observed relationship between drying wetlands in
Conclusions
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