Recognition and Spatial-Temporal Analysis of Heat Waves in Iran

The aim of this study is to recognize the heat waves and their spatial-temporal reanalysis on Iran. In order to perform this study, the daily maximum and minimum data of  the interpolated Asfazari Data Base during 1/1/1962 up to 31/12/2004 were used . The data spatial separation is 15*15 kilometers.
For heat waves recognition,  the six indices based on 90, 95 and 99 percentiles have been used which  show  the intensity, duration and frequency of heat waves’ occurrence. The recognition   of indices’ trend during  the study period was examined  by nonparametric test of Mann Kendal and then slope and the trend rate was estimated  by linear regression. The results showed that the occurrence frequency of heat waves has an increasing  trend in Iran. Also, duration and intensity of heat waves has been increased.  From spatial distribution view, the type and rate of trend over different regions is not equal.
The duration, frequency and intensity of heat waves over flat and low height plains are increasing. Among these regions the highest slope and changing rate were observed in Lout desert ( northeastern of Kerman), flat regions at  northeast of Bandar Abbas, Kavir desert  and khozestan. On the height and high elevations of Zagros and  Alborz  chains and dispread heights over Iran’s extent,  the rate of heat wave has a decreasing trend.
The intensity of heat waves frequency reduction and intensity and duration of heat waves over these regions is more than their  increasing trend on the low lands and plains.  On the western heights of Shahrekord,  the reduction trend rate of indices will reach to its maximum rate. There is no different between types of the indices trend  and their spatial dispersion based on 95 and 99^th but the  trend rate of indices based on 95^th  percentile is greater.