A Study on Dust Storms Using Wind Rose, Storm Rose and Sand Rose (Case Study: Tehran Province)

Document Type: Research Paper

Authors

1 Faculty of Natural Resources, University of Tehran, Karaj, Iran

2 Senior expert of Desert Management

3 Ph.D student of Watershed Management

Abstract

Sand and dust storms are natural events that occur widely around the world, mostly in dry and bare lands. Over the
past decade a large part of Iran has been affected by this phenomenon, and Tehran has not been excluded from this
event. Therefore, having knowledge of spatiotemporal frequency variations can aid us in future management and
storm trajectory assessment. In this study the synoptic anemometric data of Tehran-Mehrabad stations over the past
47 years were used. Annual and monthly wind and storm roses were drawn to determine the predominant wind
direction. The primary results indicated that the prevailing wind direction is western, but in summer, it is southsoutheastern.
According to the threshold wind velocity (6.5 ms-1) about 12% of recorded data was categorized into
the storm condition.. Results also indicated that western, northwestern, and southwestern winds have the three highest
rates of sand drift potential (Dpt), respectively. The temporal variability of dust storms showed that between 1951 and
2005, the largest number of days characterized by dust and thunderstorms was observed in the spring and summer.
The average number of dusty days in spring and summer was four d/m, and the fastest winds ranged from 40 to 49
m/s-1. An assessment of dusty days over the past five decades revealed that the average number of dusty days has
significantly increased from 10 days to 80 days. It seems that cyclonic circulations in the Monsoon Trough together
with regional winds in central Iran are responsible for the transmission of dust particles over central Iran. Results and
data from this study can be helpful in determining and predicting the critical dust storm period and in forming
management strategies in order to minimize aftermath impacts.

Keywords