Document Type : Research Paper

Authors

• Saeed Jahanbakhsh Asl ¹
• Ali . Mohammad Khorshiddoost ¹
• yaghoob Din Pazhooh ²
• Fatemeh Sarafroozeh ³

¹ Meteorological Department, University of Tabriz

² Department of Water Resources, Faculty of Agriculture, University of Tabriz

³ Graduate Doctorate in Physical Geography tendency climatology, University of Tabriz

Abstract

Trend analysis of 27 indices related with extreme temperature and precipitation during 1961-2011 were conducted in Tabriz using the non-parametric Mann-Kendall test and Sen’s Estimator Slope methods. Furthermore Generalized Extreme Value distribution fitted to observational extreme events. Values of quantiles of the variables were estimated for different return periods. Results indicated that during the past half century, trends of indices for summer days, tropical nights and warm nights were upward and statistically significant. Trends of indices related to ice days and cool days were downward and significant. Minimum values of daily minimum and maximum temperature in year indicate significant increasing trends. Indices of number of days with precipitation greater or equal to 10 and 15 mm, consecutive wet days, total precipitation in wet days and total precipitation when rainfall is greater than 95 and 99 percentiles have experienced significant decreasing  trends. After fitting GEV distribution to annual values of daily minimum and maximum temperature as well as daily maximum precipitation in Tabriz Growth curves and Q-Q plats were illustrated. Investigation of plots indicated that this distribution function has more capability in fitting of time series of extreme value even in tails of the distribution.    

Keywords

• Extreme Climate Events
• Nonparametric Mann-Kendal Test
• Generalized Extreme Value Distribution
• Return Period
• Tabriz