Trend Analysis The Number of Dusty Days in The Past 55 Years in The West of Iran, Using Non-Parametric Statistics

In this study, data is used to identify trend of geo-spatial changes of dusty days from 16 Synoptic Stations in the West of Iran (19 Provinces). Selected weather stations have the most complete and longest periods of recorded data. First, to provide a preliminary view of the climatology of dust in the study area, yearly and monthly changes of average number of days with dust is analyzed by using charts and maps and determined that the west of Iran from the view of number of days with dust is not homogeneous region and these phenomena increases from north to south. Then, to review the trend of occurrence of these phenomenon two non-parametric statistical methods of Mann-Kendall and Sen, s Estimator was selected. The results showed that because of input data nature, the Mann-Kendall and Sen, s Estimator methods have very good performance for analyzing of dust phenomenon trend. The results of used statistical methods showed that all studied stations (except Khoy station) are a trend, but between them, only 8 cases have a significant trend (Three stations are decreased and in 5 stations are raising trend). Finally, trend type’s geographic distribution map of dusty days frequency in the study area were taken in the GIS environment and discussed about causes the formation of such trends.