عنوان مقاله [English]
نویسندگان [English]چکیده [English]
A lot of climatic researches paid attentions to widespread climatic events. However there is not exact and scientific definition for extent of “widespread” of climate events vast. It is important to find a definition to divide local and widespread climatic events. It has to be noticed that widespread climatic events have two characters; first it has to be nature of the climate in a given place and second it has to be justified in synoptic patterns. In current research in order to achieve the aim of definition for climatic widespread events a survey has been done on widespread hot days in Iran. Accordingly daily maximum temperature database of Iran during 1961 to 2008 has been used. The hot day has defined based on 90th percentile index for every single pixel in every day of database. So there are hot day threshold for every day in year and for every location. In next step the numbers of hot days for all percents covering of Iran area was calculated. For example the numbers of hot days that covered 10-20 percentiles of Iran has calculated. Then the time series of hot day’s numbers were tested for autocorrelation function. The significant autocorrelation in a given lag shows that the time series is not random. Accordingly the time series mentioned above for all possible percent covering has test, the result showed that the non random area for hot days climatic events occurred in 30% of country covering. In order to validate this result and the climatic regulation on this sort of events central mean of hot days has been analyzed. At last the synoptic patterns in hot days have been classified to test the validity of the result.