Trend analysis of cold season hourly temperatures in Iran as an index for changing climate

The temperature is the most important climate parameter with a major role in detecting the effects of climate change. This study built on a statistical-analytical approach to analyze the hourly temperature variations in Iran. A database with 3,252,800 hourly air temperature records for 28 synoptic stations in the cold season was developed and refined for the 30-year period from 1985 to 2014. Using the linear inference method, the three-hourly synopses of air temperature were converted into hourly temperature. The Non-Parametric Mann-Kendall method was used to reveal the hourly temperature changes. The results showed that a limited number of stations experienced a significant increase in November, whilst a significant decrease was found in most stations in December. The most significant increase is found in the second half of the cold season in February and March. In March, all the stations had a positive and increasing pattern in terms of hourly temperature, and this increase was observed in the minimum hours of the night and morning. On average, more than 5 hours a day, an increasing trend was observed at 0.05 and 0.01 levels at most stations. There is an increasing trend in nearly the whole 24 hours in Meshkinshahr, Karaj, Golmakan, Tehran, Tabriz, Fasa, Yasuj, Khoy, M