Temporal Changes Analysis of Dew Point Temperature in Iran

In this study, hourly data of dew point temperature from 162 stations of the country, which had more than 10 years of data, were extracted from the database of Iran's Meteorological Organization during the period from 1951 to 2010. The hourly dew point temperature data includes 8 times and daily mean. Different methods can be used to assess the time series behavior of climate data. In this study, in addition to the linear regression trend test, a frequency analysis method was used to evaluate the dew point temperature behavior over the past few decades. For estimating the trend, the smoothed average of the hourly data was used and for frequency analysis, the daily mean dew point temperature was used.In frequency analysis, the statistical period was divided into six decades according to the Julian calendar, and then, the frequency and percentage of frequency of the data were calculated. The distribution of the temperature of the dew point of the first decade was compared with subsequent decades.A review of the decade to decade of dew point temperature in Iran has shown that, in general, its temporal behavior is changing. The percentage of distribution of the dew point temperature has shifted to low temperatures. Analysis of the linear regression test on the smoothed series the hourly dew point temperature showed that 18, 21 and 00 hours had a weakening trend. While at 03, 06, 09, 12, 15 and the average daily, a steep slope has occurred. The average dew point temperature in the solar decades of 30-60 degrees was about 5 degrees Celsius, and in the 1980s the solar fluctuated around 3.8 degrees Celsius. This decrease was accompanied by a sudden drop in the late '60s, which could be a sign of the drying of the moisture content of Iranian atmosphere.