IMPACT OF WIND DIRECTION AND SPEED ON DUSTY DAYS

The direction and speed of winds play an important role in the occurrence of pollutions and dust stormas well as location placement for the establishment of industries and the expansion of cities. Yazd is a dry area of Iran, and constantly exposed to the dust particles in the air; and this in terms of human life and health issues are of special importance. In this paper a day when due to the amount of dust particles visual acuity reduces to 5,000 m is considered the dusty day. In this study dusty days and direction and wind speed of 4 synoptic stations were studied in spring 2010. Pearson correlation has been used in the study of relationship between wind direction and speed and the occurrence of dust. The results show a direct correlation between wind direction and speed, the wind direction nearer to 360°, (North) wind speed increases. There is an inverse correlation between the speed and the visibility in dusty days, where in 17 cases this relationship has been significant up to confidence level. Of course, in 5 cases the calculated correlation is negative. So according to the obtained results. there is an inverse relation between speed and visibility in stormy days, so that with increased wind speed visibility is reduced. Although the test does not show a significant correlation between wind speed and Visibility, due to a direct correlation between wind speed and wind direction from one side and the reverse relationship between two components of speed and visibility it can be said that whatever wind direction gets close to the North, in high speed winds visibility reduces.