Statistical and Synoptic Analysis of Temperature Advection Role in Iran Spring Rainfalls (1961-2013)

The study of the temperature mechanism and temperature advection along with the thickness layer and its effect on the rainfall level of an area is one of the most important subjects in the field of atmospheric science. The present study was carried out with the aim of studying the temperature advection and recognition of thickness layer in relation to spring rainfall in Iran. For this purpose, a daily rainfall database with a spatial resolution of 15 × 15 km2 was used in the period 1961–2013. After extraction of precipitation days, the corresponding pressure data was extracted using the programming capabilities in the Grades environment, and with the help of cluster analysis, representative days and spring weather patterns were identified in the Matlab environment. To determine the day of precipitation, three criteria of daily rainfall of 1 mm or more, minimum two-day continuity, and minimum 50% coverage were considered. Sea level pressure maps of 700 and 500 hPa were extracted along with temperature advection and thickness of the atmosphere. The results showed that five effective patterns were identified on Iran's spring general rainfall mechanism. The strongest amount of temperature advection from the Siberian high pressure occurred in the eastern and north-eastern parts of the country and reduced to the west and south of its intensity. Generally, from the east to the west and from the north to the south, there was a milder temperature advection during spring rainfalls in Iran. In addition, the most severe temperature advection occurred at sea level due to high-pressure thermal systems. At higher altitudes and higher levels, the temperature advection had a milder state than the sea level, and reduced the severity of the temperature advection due to the dynamic situation of the atmosphere, especially the blocking systemand Mediterranean deep trough.