The Analysis of Dust Phenomenon in the Southern and Central Fars Province

One of the common and destructive phenomena in dry and arid regions of the world and Iran is dust storm which may have harmful effects on human life and environment. Iran is also exposed to this phenomenon because of its geographical location in arid and semiarid areas. Fars province, especially its southern and central regions, due to being located in low latitudes and its geographical position, takes less advantage of humidity routes, and its proximity to the major sources of dust within the deserts of Arabia and Iraq always exposes it to this phenomenon. Therefore, understanding how such dust is produced can be of benefit  in reducing its destructive effects in the region. This research examines the hourly data of wind direction and speed and the current weather condition of synoptic stations in southern and central Fars (Shiraz, Lar, Lamerd, Darab and Fasa). After extracting the codes related to dust phenomenon (codes 6-9 and 30-35) and a statistical analysis of the aerology data related to this phenomenon using an SPSS software, the annual and monthly Wind Roses and Dust Roses of the synoptic stations in southern and central Fars were drawn using WDconvert and WRplot software during the common statistical period of 1992-2008. The results of this investigation show that the dust occurs in the stations of southern and central Fars province on most days in spring and summer. Also, the highest monthly frequency of this phenomenon may be assigned to the central stations of this province (Shiraz and Fasa), In the southern stations (Lar, Lamerd and Darab), the highest monthly frequency is related to July. In addition, the average days with dust in Lar, Lamerd, Darab, Fasa and Shiraz stations  are 88.1, 39, 54, 30.3 and 56.1 a year respectively. Among the selective stations, Lar station has the highest annual average in terms of dusty days. The results of the research also suggest that the most days with dust occur in spring and summer.The highest frequency of this phenomenon in central and southern stations is May and July respectively. Studying the monthly and annual Wind Roses and Dust Roses of station, it is clear that the wind direction of dusts is equal to the direction of the dominant wind, and the maximum occurrence of this phenomenon is in  afternoon hours. Since the average annual wind speed of dusts in this region is almost 1m/s, dust phenomenon in Fars province doesn’t have a local source (code 07); rather, the major origin of 98% is outdoors (code 06).