Document Type : Research Paper

Authors

• Yagoub Dinpazhooh ¹
• Faege Niazi ²
• Hamed Mofid ³

¹ Water Engineering Department, Faculty of Agricultural, University of Tabriz

² Ph.D. Student, Water Engineering Department, Faculty of Agricultural, University of Tabriz.

³ Graduate in Water Department, Islamic Azad University, Tehran Branch

Abstract

The aim of this study is trend analysis of meteorological parameter including mean wind speed, min, max and mean air temperature, difference between the min and max temperature, pan evaporation, average relative humidity, sunshine hours, total precipitation, the number of days with precipitation more than 1, 5 and 10 mm, the number of days with dust, number of the days with snow and the number of days with visibility less than 2Km, degree days based on 18 and 21 ^oC at Tabriz station during 1970-2005 in three time scales, monthly, seasonal and annually using the non-parametric Mann-Kendall (MK) method. Trend analysis was conducted using two methods, which are conventional MK (for series having insignificant autocorrelation coefficients) and modified MK (for other series) in three significant levels, 1%, 5% and 10%. Trend slopes were calculated using Sen’s estimator. Results showed that in annual time scale, pan evaporation, min, max and mean temperature and degree days based on 18 and 21⁰C have significant increasing trends at 5% level but precipitation, number of the days with precipitation more than 1 and 5 mm and degree days based on 18⁰C have decreasing trend (at 5% level). Other parameters did not show significant trend in annual time scale. Trend slope of annual precipitation was -2.28 mm/year and trend slopes of all three elements, average, max and min temperature were 0.06 ⁰C/year. Observed trends in studying parameters indicate climate change in Tabriz.

Keywords

• Mann-Kendall
• Tabriz
• Meteorological parameter
• Sen’s estimator
• Trend