A Trend Analysis of Total Rainfall, Maximum Temperature and Precipitation in Iran

Climate change has recently received much attention at local, national and international level. To this end, an attempt was made to investigate the trend of total precipitation, maximum precipitation and temperature in Iran at annual scale. The data was obtained from 36 hydrometric stations from 1969 to 2009. In this study, the slope of the linear trend in the data was investigated using TSA, TFPW, PW and VCA methods. The effect of coefficient of autocorrelation of data was eliminated, and discharge time series were prewhittened, then the changing trend of total precipitation, maximum precipitation and temperature of original and prewhittened time series were analyzed using MK test. Ultimately, the ability of TFPW, PW and VCA methods in delimiting autocorrelation coefficient were investigated. The results showed that TFPW method is the best one for delimiting autocorrelation coefficient. The results of the investigation were presented based on MK_TFPW at the annual scale. Moreover, the results were indicative of a significant negative trend for the total precipitation in most parts of the country, a significant positive trend for the temperature in northwest of Iran and almost no trend in most parts of the country (no negative or Positive trend) for maximum precipitation.