Investigation of frequency changes trend of days with dust storms in western half of Iran

In this research, daily and hourly data of dust storms (horizontal vision and meteorology codes) at 26 synoptic stations of western Iran for the period of 1990–2013has been used in order toidentifying and determining trend of dust-storm-frequencies. In this research, visibility less than 1000 was used as factor in order to determining dust storm (local and external) for all of dust storm meteorology codes. This data was investigated by parametric and non-parametric tests including Man-Kendal, Sen’s and regression test in yearly scale.Results indicated that a set of 26 data series, 9 data series in Man-Kendal method, 6 data series in Sen’s method, and 13 data series in regression method have significant positive trend in significant level at %1 and %5. The results of all three methods indicated that most of stations in western half Iran have increasing trend of dust storms. It increased markedly in southwest of Iran.