Principle Component Analysis of Extreme Indices of Zanjan City Precipitation

Climate is a multivariate system. Every change in every climate variable could result in different changes in climate. Recently، experts have paid extensive attention to frequency distribution sequence of climate elements. Accordingly، many different indices have been defined. Precipitation extremes can exhibit the phase space of climate system. A technique that can be used to analyze climate phase space is multivariate statistics. In order to analyze precipitation extremes simultaneity، 26 indices of daily precipitation of Zanjan city during 1961-2006 had been chosen. Principle Components Analysis has been used to find the most important components in extreme precipitation. Accordingly، 6 components could justify about 86. 4% of variation in precipitation extremes indices. Spectral analyses on principle components have shown a 3- year cycle in second components as well as a 4-year cycle in forth component and 2-3 years cycles in the fifth. The second component that shows frequency and spells 95 percentile of precipitation has a significant decreasing trend. Also، there is a dropped jump in first component as the first percentile.