Evaluation of Variations in Extreme Precipitation Indices in Iran

Statement of the Problem:Precipitation is one of the most important climate variables in the world, and its changes can have different environmental, economic, and social consequences.

The purpose of this study was to evaluate the changes in rainfall indices in Iran.

For this goal, the latest version of the daily data of the Global Precipitation Climatology Center (GPCC) for the period from 1982 to 2016 was selected in 1×1 degree spatial resolution of latitude and longitude. By programming in the MATLAB software package, a matrix was constructed on the Iranian framework at 12784 × 750, the rows of which represented the days from 1.1.1982 to 31.12.2016, and columns represented the pixels in the region. The indices used in this study were selected from the list of standard indices recommended by the Climate World Committee of the World Meteorological Organization and the Climate Change Variation and Research Program, which made it possible to compare all stations in different countries.

The calculation of the indices changes with the help of the slope of the regression line on each of the pixels shows that in many parts in Iran, the intensity of daily precipitation is increasing. Also, in many parts of Iran, especially in western parts, the index of wet succession is decreasing, that is, the persistence of rainy days in many areas of the country is declining.