资源环境科技发展态势分析平台

The purpose of this study is to identify the vertical integrated moisture flux convergence (VIMFC) on the atmosphere of Iran. To achieve this goal, the monthly European Center for Medium range Weather Forecasting gridded data was used during the time period from 1979/1 to 2013/12. Initially, the troposphere was divided into three layers, L1 (850-1000 hPa), L2 (700-775 hPa), and L3 (500-600 hPa) based on the specific moisture amount in the atmosphere. The average long-term rate of VIMFC was plotted for each layers of the troposphere during different months of the year and relationship between VIMFC and precipitation rates was investigated on Iran. On the basis of the time series of the anomalies of the country's precipitation, the VIMFC'S rates was divided into two periods of 1979-1998 and 1999-2013. To understand the VIMFC shifts in the different layers of the troposphere and its relationship with precipitation, probability distribution function (PDF) for VIMFC and precipitation was calculated. The findings showed that in the warm months, the VIMFC was far more than the cold months of the year and the VIMFC rate in the L1 is also higher than the other layers of the troposphere. Iran's atmospheric moisture sources at the L1 are southern seas such as Red Sea, Arabic Sean, and Persian Gulf that is being driven toward Iran by Saudi Arabia Dynamic High Pressure System and Sudan's Low Pressure System. In the L2, the Saudi Arabia Dynamic High Pressure is the most important atmospheric system that sends the moisture of the southern seas to Iran. The PDF shifts of Iran's precipitation shows a very strong coordination with the VIMFC rate in different months of the year. The findings indicated that in the winter months (JFM), along with decreasing VIMFC rates, the country's precipitation rate also decreased in the second period of 1999-2013.