The Relationship between Disturbance of the Polar Jet Stream and the Surface Low Pressure Intensity

Abstract

The investigations between 300 hPa level and surface charts show that there is obvious connection between the mid-latitude cyclone waves and the polar front jet stream. The work studied the relationship between polar jet stream and surface low pressure during April's months for years from 2014 to 2016 which were the polar jet passing with high frequencies over the area of study. The weather charts used which they were 300 hPa wind speed and surface pressure in addition to the surface weather phenomenon. The study presents the structure of polar jet that affects significantly in the intensity of the low pressure system at the surface. The structure did not repeat regularly during April's months for the years from 2014 to 2016 and the structure was two types which they are continuous and discontinuous. The percentage ratios for jet-structure were different from a year to another year. The discontinuous jet-structure percentages ratios were in the year 2014 about 36 %, 6 % in 2015, 92 % in 2016. The analysis of continuous and discontinuous jet-structures declared that the estimating of the surface low pressure center value needs the correcting of recognizing of the polar jet-structure. The analysis also showed the relationship between the surface low pressure system center value and the lowest polar jet geopotential height at 300 hPa level was in general decreasing geopotential height causing decreasing the low pressure center value on the surface but the structure of polar jet is important. The plotting between low pressure center value on y-axis and geopotential height value on x-axis by using SigmaPlot program offered that in April 2014 that the relationship between low pressure center and geopotential height was direct relationship with continuous jet-structure while it was indirect with discontinuous jet-structure. The mixing between continuous and discontinuous jet-structure data for the same year will distort that relationship.. In April 2015 with small ratio of discontinuous jet-type the relationship between geopotential height and surface low pressure center was direct relationship. In April 2016 with high ratio of discontinuous jet-structure the relationship between geopotential height and surface low pressure center was also direct. In April 2014 the ratio was near from middle that causing the relationship between low pressure center and geopotential height distorted. The study also revealed the low pressure center value would be less with the discontinuous jet-type if there were same geopotential height values of continuous and discontinuous jet-type.