The Impact On Weather Systems Of Upper-level Jet Stream And Its Dynamics Of Change

Using regular observation data, weather satellites data, doppler radar data, NCEP/NCAR reanalysis data and the mesoscale model WRF, are used to make diagnostic analyses, numerical simulations and tests of strong convective weather systems occurred on the sea, and mid-term rainfall process, to analyse the effect of upper-level jet stream on the extreme weather systems, and the dynamics of upper-level jet stream’s change.On the strong squall line process, which occurred in Qingdao’s near sea area, in the early morning of August 10th,2013, the results show that the upper-level jet stream existed in the east side of the upper-level trough at 200hPa. The cold temperature advection over land strengthened the trough, prompting the near sea area where disastrous accident occurred, located in the right side of upper-level jet stream’s entrance region, had a strong suction effect, developed the squall line process. Analyse vertical structure of the squall line, find there was a strong divergence in upper-level, a strong convergence in low-level, descending dry current from the middle and upper of troposphere, are the main cause of the formation of strong wind on the sea-level.Through the diagnosis and comparisons of meteorological element fields, find the causes of Yangtze River basin’s more precipitation than previous years’ average during Meiyu period of June 2011, and research the impact of upper-level jet streams on several main heavy rainfall processes preliminary. Compare three heavy rainfall processes, find the reason of the maximum precipitation is, during June 13th to June 15th, Yangtze River basin located in the right side of upper-level jet stream’s entrance region, and upper-level jet stream has an intensive strength.On the heavyrainfall during June 13th to June 15th,2013, the results show that upper-level jet stream had a more significant effect at 200hPa, when its suction appeared in the right side of upper-level jet stream’s entrance region. The vorticity advection had a significantly increased with height, promoting a strong upward movement at 500hPa, also had a strong divergence in upper-level, a strong convergence in low-level. There was also low-level jet streams and its huge amount of moisture transportion at 850hPa in the lower troposphere, prompting the developed of vortex system, also existed a convectively unstable stratification, benefiting the heavy rain process.Using control and sensitive tests of WRF numerical simulation for the research of upper-level jet stream’s dynamics of change. The results show that, it has not a significant effect on the upper-level jet stream and the geopotential height and stream field at each layer, when reducing the sea surface temperature gradient. There is a significant effect on the upper-level jet stream when closing the process of releasing latent heat, the geopotential height and stream field exist apparent changes at each layer. Analyse the vertical temperature anomaly field, find a significant effect in tropopause atmosphere’s temperature by latent heat releasing. The latent heat releasing promote the increase of the geopotential height ot upper-level of troposphere benefiting the divergence effect, promoting an upward movement of huge amount of moisture, a positive feedback process has established. The feedback of upper-level jet stream-upward movement-latent heat relasing-upper-level jet stream,is the main cause of the flood in June 2011.