عنوان مقاله [English]
In this research, we attempted to identify the cause for occurrence of the heat wave in April 2008 as one of the most significant and most comprehensive heat waves. Since deep recognition of such phenomena is not possible only by ground data, so, it is necessary to study synoptic conditions and effective atmospheric factors more than before. To study synoptic of how the heat wave occurs, the geopotential height, sea level pressure, air temperature, as well as the meridian and orbital component of the wind data at various levels with a resolution of 2.5 to 2.5 degrees, were obtained and the mean maps and anomalies of geopotential pressure and height at different levels, hot air flow and thickness map were plotted using GrADS software. The synoptic results showed that the existence of thermal low pressure in sea level and settlement of the subtropical high pressure was a major cause of this heat wave. The formation of a thermal low pressure center in the lower level of the atmosphere, on Sudan and the expansion from the south and southwest on Iran, causes the hot and dry weather of the desert areas, such as Saudi Arabia and Iraq move towards Iran. On the other hand the subtropical high pressure with hot core, when formed at the intermediate levels of the troposphere, causes a considerable increase in temperature due to air subsidence inside it.