Spatial analysis of the frequency of jet stream influencing western Iran extreme precipitation

In all weather maps, without exception belt or wind tape at high speed are seen to have drawn very long distances. As defined by the World Meteorological Organization, whenever the tape speed is faster than 30 meters per second, the jet stream is created (Alijani and Kavyani, 1379: 291). However, according to the definition in the dictionary of weather and climate extreme horizontal winds with speeds of over 50 knots, or about 26 meters per second, above the planetary winds blow, refers jet stream (Hitch, 1961). In fact, the jet stream, the core of which are fast moving and in the context of long and short waves, as they are areas of convergence and divergence (Alijani, 1381: 82). The core of the jet stream speed is also reduced from the core center around which this reduction to the poles to the equator volubility or positive, or negative anti cyclone.
Experimental basic research with an inductive approach. Geographical zones studied western regions of Iran. The data base that environmental to circulation approach involves two variables. The daily precipitation data of 69 synoptic stations and climate West of Iran (Hamedan, Kurdistan, Kermanshah, Lorestan and Ilam) in the interval from 2010 to 1961 as the database environment event was received from the National Weather Service. The second group of variables including wind component-oriented data and meridional wind component in order to draw jet streams at levels 250, 300, 400 and 500 hp were taken from the website of Noaa , data extraction was performed using the software Grds. According to the event database environment, enjoying updated daily rainfall 18624 West Iran interpolation method was Kriging. or this purpose, an interpolation of rainfall per day, the study area the size of 2.5 × 2.5 km in 1367 became cells, resulting in the formation of an array of daily precipitation database with dimensions of 1367 × 18624 West was Iran. Selected. Perform calculations on the data, was conducted using MATLAB software. The resulting calculation is presented in the form of maps. Maps arches were used for mapping software The number of rainy days inclusive extreme studied stations cover 30% of the 119 days that were analyzed. One of the most common parameters in spatial analysis in relation to the distribution points around the center Average used, the standard deviation ellipse. Since the situation may be occurring phenomena, has deviated directional arrow and oval standard deviation of the probability distribution may well show (Asgari, 1390: 89), as well as in-order to display the deviation of the distribution points, the standard oval used. Standard oval on the frequency jet stream was applied in each pixel.
Frequency jet stream at 250 hPa level spatial analysis showed that the most frequent jet stream is from the Southern Red Sea to the south of the Mediterranean, in other words more than 70% of the formation, establishment and cross Jetstream’s West's influence on rainfall in this area is, which is the main route from the Red Sea, which leads to water injection system precipitation from the Red Sea to the West Iran.% of the formation and establishment of the jet stream. Frequency jet stream at 400 hPa level spatial analysis showed that during the study period was the most common jet streams northeastern extension of the Red Sea to the west over Irans. The actual zones in this area in more than 50% of the formation and establishment of the jet stream. By reducing the height of the territory of jet streams and their influence has waned. Spatial analysis showed that the frequency jet stream at 500 hPa level jet stream during the study period was the most common variety of the northeastern Red Sea to the west of Iran in the covers. The actual zones in this area in more than 50% of the formation and establishment of the jet stream. The results of the standard oval jet stream in the range of activities on Iran's western regions, respectively. Given that, the event shows the dispersion ellipse fitting, oval shows the pattern of the jet stream of high activity in the West of Iran.
The results show that the jet stream at 250 hPa level, show a high frequency. Maps of average speed jet stream jet stream and on the other hand, in accordance with the highest frequency of occurrence coinciding with the maximum speed jet streams in the study area, and reflects the core jet stream wrapping the second quarter (by increasing positive vortices and upper level divergence and low levels of the atmosphere is mobile convergence) on the West Iran.