Zohre Ebrahimi-Khusfi

In this study, change patterns in the standardized surface soil moisture (SSM), standardized land surface temperature (SLST) and standardized normalized difference vegetation index (SNDVI) across arid and semiarid regions of Iran were first investigated by Mann-Kendall test. Then the temporal response of dust occurrences to terrestrial factors variations in 1, 3, 6, 9, and 12-monthly time series at different lag times was identified using the cross-correlation (CC) method. The standardized dust concentration (SDC) in dusty days was considered as a criterion for measuring dust storms activity in the monitoring period (2010-2018). The results showed that arid regions of Iran have experienced a decreasing trend of dust events in recent years while semiarid regions have experienced an increasing trend of these events from 2010 onwards. The SSM changes trend in both regions was positive and significant in different time series (Z>+1.96). A similar trend was observed for SNDVI in long-term series across these areas. In the arid regions, the SLST variations showed the meaningful positive trends in various time series (Z>+4.5) while it showed only a significant positive trend in 1-monthly series (Z=+2.12) over semiarid regions. According to the strongest CC amounts, the temporal response of dust events to changes in vegetation, LST, and SM across arid regions occurred in time series of 6-monthly, 12-monthly, and 3-monthly with different time lags. For the semi-arid regions, 12-monthly time series with a 1-month and 5-month lag were identified as temporal responses of dust events to vegetation and LST variations, respectively.