عنوان مقاله [English]
In recent years, dust storms have become one of the environmental problems, especially in desert and semi-desert countries. Dust storms are a great natural hazard to human health and cause great damage to human societies every year. In this research, the effect of the RMM index (Real-time Multivariate MJO index) of Madden-Julian Oscillation on the frequency of dust storms in the west of Iran )Sarpol-E-Zahab, Islamabad Gharb, Kermanshah and Kangavar stations located in Kermanshah province as a representative province) during February to July 1987-2022 and the frequency percentage of this index for positive and negative phases was investigated. Daily data related to horizontal visibility and current weather code for a statistical period of 35 years (1987-2022) were received from Iran Meteorological Organization (IRO). Horizontal visibility data less than 1 km and dust phenomenon codes 6, 7, 8, 9, 30, 31, 32, 33, and 35 were filtered from codes 0 to 99). Then, Madden-Julian Oscillation data were obtained from the Australian Government Climate and Air Research Center and filtered for the statistical period of February to July 1987-2022. Analyzing the relationship between Madden Julian Oscillation and dust in Kermanshah province showed that 63 and 57 percent of dust storms occurred in the negative phase of the RMM index, and 37 to 42 percent occurred in its positive phase. The negative phase of the RMM index has a higher percentage of dust storms than its negative phase. According to the results of the Mann-Whitney test, the displacement of the positive and negative phases of the RMM index has significantly led to dust storms in the Kermanshah and Kangavar stations. The results showed that the negative phase of the RMM index accounted for a higher percentage of dust storms in Kermanshah than the negative phase of this index. The results also showed that dust storms are more likely to occur in the active state of the RMM index than in its weak state. The percentage of dust occurrence in the inactive state of this index changes between 48% in Kangavar station and 34.6% in Islamabad West station. Analysis of the role of positive and negative phases and amplitude values showed that the negative phase and amplitude greater than or equal to 1 are the most influential in the occurrence of dust storms in the stations of Kermanshah province. Tracking the paths of dust entering Kermanshah province with the HYSPLIT model and analyzing the wind speed and direction maps at 700 hectopascal level indicate an increase in the speed of western winds and the movement of dust particles from Iraq, eastern parts of Syria, and Khuzestan province towards Kermanshah province.