Bivariate Analysis of Return Period of Dust Storm Based on Copula Theory in Yazd Province

Dust storm is a stochastical event that depends on several parameters, therefore, multivariate analysis of this event is really important. In this study, importance and shortage of multivariate analysis of natural disasters such as dust storm is investigated. For this purpose, Copula theory is used for bivariate analysis of dust storm. Copulas function are useful tools for multivariate frequency analysis of natural disasters. One of the main advantages of Copula theory is that there is no limit to select the type of marginal distribution. In order to perform bivariate analysis of dust storm, severe dust storm was selected based on definition of WMO from 1982 to 2014 in Yazd province. 34 dust storm events were extracted and maximum wind speed and geopotential heights were determined corresponding to stormy days. Finally, the bivariate return period was calculated based on maximum wind speed and geopotential height using the t-student Copula as the best function. Also, univariate return period of dust storm was calculated based on maximum wind speed and geopotential height, separately for comparison with bivariate return period. The results showed bivariate analysis of return period of dust storm is more accurate than univariate return period.