عنوان مقاله [English]
نویسندگان [English]چکیده [English]
All around the world disasters and hazards occurs that always endanger human life and property. Among these disasters, storm is one of the most dangerous that allocate about 30 percent share of 90 percent natural disasters related to climatic factors and yearly enter irreparable damage in life and property. In some area of Iran occur incidence of storms by speed more than 100 kilometers in one hour occurred times.
Kermanshah province has located in the western end of Iran's country, is one of the areas that effected by these storms.
To study statistically and predicting incident probability of stormy and strong winds of Kermanshah province is used way of analyzing and partial series used anemometer data in 5 stations synoptic in Islamabad, Ravansar, Kermanshah, Sarpolzehab and Kangavar throughout statistical period 20 years (1990-2009). In this method by proposing this argument that occur strong winds or storms in few years which their speed is more than maximum speed and must consider for preventing damages and safety. After regulating matrix table of data, by using SPSS software data are arranged. To select days along with stormy and strong wind, winds with equal speed and more than 17m/s (strong wind base in scale of Biofort ) and accepted by weather meteorology organization(WMO) is accounted as days by stormy and strong wind. Correctness and homogeneous of data is accepted by using of followings test. At first winds by speed higher than base speed is selected and without attention to the year occurrence are ranked and accounted incident probability by Vibol relation. Then in studying strong storms by certain return period and by using certain statistical years (2009-1990) base speed is selected that occurs annual at average between 3 to 5 stronger winds. At the other stage all strong winds and storms that is more than base amount is extracted. By considering all strong winds by speed more than base speed, average occurrence at year is accounted and finally storm speed by certain return period and average speed of predicted storms is obtained.
3â Discussion and Conclusion
Considering that obtained findings, occurrence of strong winds and storm with speed (17m/s) and more at Islamabad, Ravansar, Kermanshah, Sarpolzahab and Kangavar station is phenomenon relative common and is natural properties of region. Throughout statistical period (1990-2009), Islamabad station 72 days, Kermanshah station 76 days, Kangaver station 90 days, Ravansar station 94 days Sarpolzahab station 98 days. With wind (17 mls and higher) has been observed. According to studying and movneter data, maximum recorded wind speed among studied 5 stations, has been 34 m/s and belonged to Sarpolzahab station. By comparison of station, probability of occurrence at dangerous storms at Sarpol Zahab station has been more than other station and less at Islamabad station. predicting probability of occurrence of storms by speed more than base that performed by analyzing and decomposition method of partial series in return periods, has been showed that by probability near to 100 percent in return period of 1 year stormy and stormy and strong winds by speed 18/84 m/s at Islamabad station, 19 m/s at Kermanshah station, 20/53 m/s at Ravansar station, 20/68 m/s at Kangaver station and 23/56 m/s at Sarpolzahab have been occurred. Also predicted that in one return period 100 years, by probability 1 percent storm by speed 41/09 m/s at Sarpolzahab station, 30/39 m/s at Kangaver station, 29/54 m/s at Islamabad station has been occurred. Among recorded data throughout statistical period, Sarpolzahab by 98 days, along with stormy and strong wind and Islamabad station by 72 days, have been the least days by stormy and strong wind. Maximum observed storm speed 34 m/s belonged to Sarpolzahab station minimum observed storm speed 19/57 s belonged to Islamabad station.
Drawing annul wind rose by WRPLOT software is showed that direction of stormy and strong wind of region has been different at studied station. The results predict probability of incidence of stormy and stormy winds for studied stations in return period. Probability of occurrence predict maximum speed in one return period 100 years at Sarpolzahab station to 41/09 m/s. In addition probability of occurrence of strong winds by speed more than 18 m/s in return period one year at mentioned stations is near to 100%. Thus, in environmental planning and safety of structures must consider occurrence of this natural danger that decrease these damages.