چکیده:
Indian Ocean is known as a source of moisture for southeast of Iran due to summer precipitation. In this study, in order to investigate the role of SST of Indian Ocean, and the convergence and divergence fields in the precipitation of southeast of Iran, precipitation data of five synoptic stations were used during 2000-2010, including Iranshahr, Khash, ChahBahar, Zabul, and Saravan. To investigate synoptic circumstances of precipitation, different atmospheric levels of data was obtained from National Oceanic and Atmospheric of United States (NOAA) website with the horizontal resolution of 5.2 degree. Afterward, maps of wind, heights, and moisture flux were prepared. The results show that these three important factors (including Indian Ocean surface temperature (SST), convergence and divergence fields, and monsoon returned east jet stream) have one important role in the summer rainfall event for the study region. In addition, summer precipitation is influenced by the wet and shallow summer monsoon, sea surface temperatures, and convergence and divergence in continental regions. East jet stream have also been effective in these regions. Summer rainfall patterns have played roles in this region, including the convergence of the wind in southeast of Iran and the divergence of wind in the southeast of Arabian Peninsula in first pattern. The above circumstances as well as high temperatures of sea surface are considered in second pattern, and high sea surface temperature and the monsoon East jet stream in third pattern.
خلاصه ماشینی:
The results show that these three important factors (including Indian Ocean surface temperature (SST), convergence and divergence fields, and monsoon returned east jet stream) have one important role in the summer rainfall event for the study region.
The results of precipitation forecast in the Indian Ocean using sea surface temperature (Bollasina & Nigam, 2009), as well as the role of the above processes in weather forecasting systems (Jasti et al.
Observing Indian Ocean surface temperature during the period of 2008-1950 using empirical orthogonal functions and correlation analysis revealed that the occurrence of El Niño and Southern Oscillation (ENSO) and global warming on the Arctic Ocean, a uni-polar model on the ocean is evident that it caused the lack of climate diversity on the ocean (Dietmar, 2011; Rao & Rongcai, 2015).
The Western Pacific precipitation associated with SST, ENSO and moisture flux convergence showed a high correlation between moisture of the ocean surface temperature with precipitation in these areas that these precipitations had been evident more in western parts of the tropical Pacific Ocean (Byeong & Kyung, 2015).
During the winter, the effect of Mediterranean Sea surface temperature fluctuations on rainfall in the western of Iran revealed that when Med SST is colder than usual, the winter precipitation increases in the study area.
Therefore the aim of this study is to determine the three important parameters (Indian Ocean SST, the wind convergence, and divergence fields at Geopotential level) of rainfall in the southeast of Iran.
1. imatic characteristics sea surface Figure 3 shows the distribution of Indian Ocean surface temperature, wind currents and convergence and divergence fields in the vicinity of Earth surface.