Hossein Asakereh; Hasan Shadman
Abstract
Abstract
Hotdays are temperature extreme states and are considered to be one of the important climatic phenomena. Long term changes (trends) of thisphenomenon arethe consequences and evidences of thermal-climatic changes. Also, these days can affect the ecosystems and human life. Therefore, recognizing ...
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Abstract
Hotdays are temperature extreme states and are considered to be one of the important climatic phenomena. Long term changes (trends) of thisphenomenon arethe consequences and evidences of thermal-climatic changes. Also, these days can affect the ecosystems and human life. Therefore, recognizing the behavior of hot days can be the source of many topics. In this research, we tried to investigate the long-term trend of Iran's hot days using the network data of the country’s average maximum temperature from 1961 to 2007 and statistical methods. For this purpose, the hot day profile was studied based on the percentile of ninety for each pixel from the network and was estimated on each day of the year. Thus, a threshold of heat occurrence was obtained for each pixel every day. Then, the days whose temperatures equaled or exceeded this threshold, were considered hot days.The average number of hot days in the country is 39 days. The cold season months, as well as April, have the highest frequency of the average hot days.The frequency of hot days is increasing. The number of hot days has made a positive trend for about half of the country. Also, the average temperature of hot days has also been checked. The trend of the average temperature of hot daysin more than half of the countryhas been positive and in around one third of the country has been negative.The hot days’ temperature-related events of Iran have a 3 to 4 year cycle. Toanalyze the trend in data, linear regression was used with least squares error method and a spectral analysis method was used to investigate the existence of significant fluctuations in the data.
