Abstract

Understanding how jet streams influence climate prediction and how other events take placeis one of the main objectives of any analysis of general atmosphere circulation. In the present study, the data are used from the zonal and meridional wind components at levels 200, 300, 400 and 500 Hap, ranging from north latitude of 20° up to 80°, and longitude of 10 ° up to 120 °.The time interval is from March 1951 to March 2011.A matrix is created atthe size of 1325 × 21914 the rows are days and the columns are pixels).The daily mean wind speed is considered for each level. These data are extracted by using GrADS software. Then, using Arc Map software, standard ellipses are drawn for each level. The descriptive analysis results indicate an annual scale of events. The annualcenter of the subtropical areas is 200 hpa over North Africa, Red Sea and northern Arabia. This center transferred at the levels below onto the East. Also, the mean annual frequency is because of the maximum occurrence of the core in the area. This phenomenon is an important factor in the transfer of dust to the Southwest and the West. The standard ellipse drawn at all levels showed that Iran is in the second half of the ellipse, and it has moved in the west and slightly north in the below level. The maximum of the core frequency during the mentioned period occurred in Khuzestan, Bushehr, Fars, Kerman, Hormozgan and Sistanva Baluchistan. The core of the jet stream in the right input and output of the left is associated with a high divergence.If there isa simultaneous ground-level convergence and a lack of moisture, dust storms occur. کلیدواژگان [English] Jet stream, Iran, Standard ellipse, Zonal component of the wind, Meridional component of the wind, Desert areas