پديد آورندگان :
سليمي، سعدون نويسنده كارشناسيارشد آب و هواشناسي سينوپتيك، دانشگاه خوارزمي , , سليقه، محمد نويسنده ,
كليدواژه :
انتقال رطوبت , اقليم ايران , چشمههاي اتمسفري , رودباد , شاخص مداري باد
چكيده لاتين :
Extended Abstract
Introduction:
Water vapor spreads in molecular, unstable and erratic phase and transfers by convection and advection process. This transfer happens from the earth and oceansʹ surfaces to the atmosphere by the hot air. This type of this transfer is considered as the main pattern. In the studies of the atmosphere, one of the prominent factors to be considered is the complexity of water vapor and its cycle.Water structure is different above the surface of the earth and the oceans. The study on water structure was first done in 1960, in which a great deal of information gathered by the meteoric satellites, and according to this fact the researches about this phenomenon were set off. One of the water structures is the atmospheric river, which is considered as a separate factor recently. The definition of the atmospheric river as the Tropospheric River was first introduced by Riginald Newell in 1992. Regarding to the fact that Middle East, especially Iran, is facing a sever trend of drought, it is necessary to provide programs and plans to prevent this phenomenon. Moreover, the vast and small water sources and the moisture entries have to be identified.
Materials and methods:
In this research the specific humidity maps were reanalyzed in three years’ time (2011, 12, 13), which were provided by NOAA administration. About 1000 maps from different surfaces were drawn in this period, and after the days with the occurrence of Atmospheric River were identified, jet stream maps were produced. For the jet stream maps two types of winds were used: UWND and VWND which are derived from the NOAA administration. The maps were designed by the GRADS program by the use of 300 hPa of the defined day. Afterwards, the relation between the atmospheric river and jet stream of 300 level of the defined day was studied. These relations with zonal wind were calculated in SPSS program by using the Pearson correlation coefficient.
Results and discussion:
The average occurrence of ARS phenomenon in Iran is 13 that enter the country from different directions. In 2012, the highest amount of atmospheric river was reported. Approximately, 27 percent of the rivers were from the West, and thesoutheast, southwest and south were 8, 46 and 19 percent effective. West ARs happen mostly in February, which 80 percent happens in the winter. Also the other 20 percent happens in the late autumn in December. The ARs are considered as 400hPa height, which 90 percent of them happen at this height level. East south ARsʹ occurrence rate is the least with the low percentage of 8. Based on the seasons, these Atmospheric Rivers happen more in August and July. Their movement level is 600 hPa, which is in a lower level comparing the western ARs. West south ARs are considered as the main entries, due to the fact that 46 percent of the ARs are from this direction. These rivers are in lower levels, 600 and 700 hPa. About 60 percent of these rivers happen in the autumn, as the winter has the second rate. The other direction of the rivers is the southern part, which is considered the most unregulated AR and can happen during all the seasons except the winter. This direction is on the third stage according to the occurrence, and includes only 19 percent of the rivers. It enters Iran at the level of 700hPa, and is rarely reported by other levels.
Conclusion:
The occurrence of Massive flood sin the southern regions on the one hand, and reduce the average of total rainfall in the country on the other hand, representing to being influencing Iran from the destructive and climate events and phenomena. For predicting flooding and accordance the types of economic activities related to water, it is necessary to be recognized their sources and the transport of moisture factors and type in different levels of the atmosphere. In this study, it has been studied Transport of water vapor through distinct phenomena on called synoptic atmospheric rivers (ARS). In the beginning of the research re-processed data of specific humidity, were taken for a period of three years (2011-2013)from the NOAA. Then, the maps were prepared by Software GRADS. The results show that about 12atmosphericrivers were observed during the study period on average annually and have been classified so-called western, southwestern, southern and southeastern Atmospheric Rivers. Studies show that River Winds have created the phenomena. Moisture in the river is about 6 times of Surroundings on the average. Atmospheric rivers feed atmospheric spring head along the way. Southern and southwestern Atmospheric Rivers have the most the amount of moisture. Rainfall maps also showed the rainfall of Southern Atmospheric Rivers have the amount and even lead to the Flood and Water logging passages in the southern cities. Pearson correlation coefficients showed that their relationship between atmospheric rivers with orbital indexes, respectively, are the southern, southwestern and western ARS which their Correlation values are 28, 53, 85 percentage.
