Change Detection of Precipitation Trend of Northern Part of Iran using Mann- Kendall Non-Parametric Test

Climate scientists have concluded that the air temperature of earth’s surface warmed to 0.6 during the 20th century, and that warming induced by increasing concentrations of greenhouse gases accompanied by changes in the precipitation and hydrologic cycle. Monthly, seasonal and annual precipitation trends of meteorological stations have been analyzed and interpolated in the northern part of Iran for three periods (30, 40, 50 years). The Mann-Kendall trend test was applied to examine the monthly precipitation data. Significant positive and negative trends at the 90, 95, and 99 percent confidence levels were detected for numerous stations. The detected trends were spatially interpolated by applying the inverse distance weighted (IDW) interpolation method. The amount of RMSE for different variables obtained using IDW less than 0.2, indicating the effectiveness of this method in the interpolation of rainfall. The results showed that the trend of variation, both in terms of time and spatial is different in the study area, as has experienced downward trend in cold season and upward trend in warm season which indicates the importance of climate change in the study area. The spatial variation trends results for mean annual precipitation of 30 and 40 years period showed that the east of region have downward trend and the west of region have the upward trend. For the 40-years period, downward trend of station nearly are situated in eastern part of region, as downward trend at 90% confidence level are evident for Talar basin. The western part of region experienced upward trend at 99% confidence level especially in Chaloos-roud basin. The results of this study indicated that the region has experienced the severe climatic change which the better understanding of the climate variation and its impacts on water recourses, natural environment and other related sector are necessary.