Interannual variations of dust activity in western Iran and their possible mechanisms

ABSTRACT

Through an analysis of station observations and reanalysis data, in this study, we investigate the variations of dust activity during 1979–2015 in western and southwestern Iran and their associated mechanisms. The dust day frequency (DDF) is used to identify dust activities. The results show larger interannual variabilities in the DDF in spring and summer, with standard deviations (σ) of 10% and 13%, respectively. Correlation analyses reveal that the interannual variability of DDF in western Iran is largely regulated by wind speed, precipitation and soil moisture in the region. The regional mean spring (March–May) DDF shows strong negative correlations with spring precipitation (correlation coefficient R = −0.5) and soil moisture (R = −0.6) over western to southwestern Iran, but strong positive correlations between the springtime DDF and surface winds can be found with the R reaching 0.4–0.6. Dust activity in the summer dry season (June–August) is mainly associated with surface winds over southwestern Iran, especially in regions near the Persian Gulf, where the R between the DDF and surface winds reaches 0.5. Meanwhile, the summer DDF also shows strong negative correlations (R < −0.4) with soil moisture of the top layer in the middle to southern part of the region. These results highlight the key roles of wind speed, precipitation and soil moisture in determining the interannual variation of dust activities in western and southwestern Iran.

KEYWORDS:

• Dust activity
• interannual variation
• wind speed
• precipitation
• western Iran

Acknowledgments

We would like to thank the Islamic Republic of Iran Meteorological Organization (IRIMO) for access to weather data. The European Centre for Medium‐Range Weather Forecasts (ECMWF) reanalysis project for wind field and soil moisture data, and the Global Precipitation Climatology Centre (GPCC) for precipitation data over Middle East are gratefully acknowledged.

Data availability statement

Meteorological data are available on the Islamic Republic of Iran Meteorological Organization (IRIMO) website: https://data.irimo.ir. Reanalysis wind speed data from ERA-Interim and soil moisture data from ERA-Interim/Land data are available at the following website: https://apps.ecmwf.int/datasets. Precipitation dataset from GPCC V7 are available at the following website: https://www.esrl.noaa.gov/psd/data/gridded/data.gpcc.html.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study is jointly supported by the Chinese Academy of Sciences (CAS) Strategic Priority Research Program (grant XDA19030403), the National Natural Science Foundation of China (grant 41575095, 41830966 and 41505131) and CAS “The Belt and Road Initiatives” program on international cooperation (grant 134111KYSB20160010). The authors acknowledge the support of the CAS-TWAS President Fellowship.