The aim of this paper is to investigate annual and seasonal precipitation trends of some selective meteorological stations of central region in Iran using non-parametric methods. Two non-parametric methods including Mann-Kendall and Sen's estimator slope methods were used here to analyze the seasonal and annual trends of precipitation data. Some 48 meteorological stations in central region of Iran which in the period of (1971-2000) had full records were selected and two mentioned tests were applied and results were compared. The results showed that the application of these two methods is almost similar, although the Sen's estimator slope method showed better performance where the number of zero in the time series of data was considerable. There is a significant negative trend in both tests in some of the time series, but no significant positive trend for both tests was confirmed. Since the number of series with significant trend in comparison to series without any trend was small, therefore a general trend can not be attributed to the region.
Keywords: Trend analysis, Precipitation, Non-parametric Methods, Mann-Kendall, Sen's Estimator Slope.