Case study survey of surface air density and water vapor pressure over Iran

In this study, air density and water vapor pressure for 184 synoptic meteorological stations in the year2004, 2005 and 2015 were calculated based on the theoretical of computing these two parameters. The results indicate monthly, seasonal and annual averages of WVP and air density were maximum values over shores of the Caspian-Sea and the Persian-Gulf, while the values were minimum over the highlands of the Zagros and Alborz mountains. These results are compatible with theoretical fundamentals indicating the exponential reduction of density with height. Moreover, it was observed that the monthly, seasonal and annual averages of air density over shores of the Caspian-Sea were higher than the corresponding values over the Persian-Gulf coasts. These conditions occur due to changes in air pressure as a result of cold high pressure system extension in the cool season where its related dominating ridge affects most regions of Iran causing air pressure increase over the Southern-Caspian-Sea(SCS) proportional to the corresponding value over Iran’s-Southern-Coasts(ISC); hence the average density during winter season over the SCS where affected by high pressure systems is more than corresponding value over the ISC. During the warm seasons a result of heat low pressure system predomination over southern Iran, air pressure decrease over these regions, while the SCS area are subjected to relatively high pressure system. Therefore air density average over the ISC will be lower than the corresponding one over the SCS in the warm season.