Document Type : Research Paper
Authors
1 Water Eng. Dept., University of Tabriz
2 Dept. of Climatology, University of Tabriz
3 ِDept. of Climatology, University of Tabriz
Abstract
In this study the values of potential reference crop evapotranspiration were calculated using the FAO-56 Penman Monteith method in six stations located in southern shores of Caspian Sea. Trends in annual ET0 values of the stations were analyzed using the Mann-Kendall test. Then to determine the relative importance of climatic variables on ET0 in a certain station factor analysis conducted. To do this, correlation matrix (R) of seven variables also called similarity matrix was constructed. The significance of correlation coefficients were tested. Results of trends in ET0 showed that in all the stations (except Noshahr) trends of annual ET0 were upward and significant. The slopes of trend lines were positive in all the stations. Factor analysis showed that the first two factors accounted the total variance in the range of 56.5 per cent in the Rasht to 79.6 per cent in the Sari. The largest loading of the first factor is attributed to sunshine hours in the station Rasht, however, it was maximum air temperature in all other sites. In the case of the second factor, the largest loading belonged to wind speed (in Rasht, Gorgan, Sari and Noshahr) and precipitation (in Ramsar and Astara). The findings of this study can be helpful in optimum management of regional water resources.
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