Trend Analysis of Annual Dry Periods Using SPI and AMDSL and ANDSPs Indices

Authors

1 student of kashan university

2 Associate Professor

3 Urmia university

Abstract

< p >Abstract
Study of the trend and change of precipitation is very important in the proper management of water resources. In this research, in order to analyze the changes in precipitation and annual dry spell period, the trends of SPI and two Annual Maximum Dry Spell length and Annual Number of Dry Spell Periods indices are studied. For this purpose, daily precipitation data in five synoptic station of northwest of Iran (Urmia, Tabriz, Ardebile, Khoy and Maragheh) which has a 30-year data (2010-1981), are used. After examining the homogeneity and normality of the data, significant autocorrelation in each series were tested According to Mann-Kendall test, all three indices have a decreasing trend in most stations. Decreasing trend in two AMDSL and ANDSPs indices reflects the improving climatic condition and decreasing trend of SPI index indicates reduction of precipitation. So we can conclude that despite of the reduction in precipitation in the region, rainfall distribution has improved over the years. Decreasing trend of two SPI, and ANDSP indices is significant in Maragheh and Mann-Kendall (p < 0.05). Test criteria (Zm) for SPI, and ANDSP indices are -3.622 and -2.408 respectively. In order to identify the start points of trends of series, sequential Mann-Kendall techniques have been used. The results indicate the occurrence of significant mutations in Maragheh station.

Keywords


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