The Genesic Mechanism Of Kunming Quasi-Stationary Front

Based on the significant difference of temperature between Kunming and Guiyang in the process of Kunming quasi-stationary front, the ERA-Interim reanalysis data and conventional observation data are used to build a data series of Kunming quasi-stationary front, and the data series are verified by synthetic analysis and correlation analysis. After that, the climatological features of Kunming quasi-stationary front during 2010-2014 are summarized and the average location of Kunming quasi-stationary front is also available. Then day-by-day diagnoses are done to the Kunming quasi-stationary front with the frontogenesis formula. The genesic mechanism of Kunming quasi-stationary front is identified by comparing contributions of each item of the frontgenesis function. Results are as follow:(1) A continuing Kunming quasi-stationary series is obtained by the criterion of which standardized temperature difference between Kunming and Guiyang is larger than 0.8 and lasts at least two days.Comparison with observation data during two periods of November 2004 to April 2005 and the whole year of 2010 shown that the criterion mentioned before is feasible and reliable although it looks very simple.(2) 343 days are picked out as Kunming quasi-stationary front activiting days from the study period of 2010-2014, divided into 67 processes. The time frequency is 68.6 days, divided into 13.4 processes per year. Each processed last for 5 days. Largest number of process occurred in 2010, which is 17 times, and the fewest number is in 2013, which is just 11 times.(3) Experiments of locating front with the method developed by Hewson are carried out using data from January to February 2008. Results shows that this method can be used to discriminate the location of frontal zones of Kunming quasi-stationary front. The suitable locating variable and threshold of masking variable for Kunming quasi-stationary front are determined through comparisons between a lot of experiments of different pressure levels and different front locating variable and different mask variable threshold.(4) Composite analysis to 343 activiting days shows that there are obvious temperature gradient and convergence of wind along the frontal zone at the lower pressure levels blow 800hPa, whereas no such features can be seen at the higher pressure levels. There is no gradient in specific humidity field at all pressure levels from 850 hPa to 500hPa. Based on the composition of temperature and wind field, the location of frontal line at 850hPa is visible, which has a turning point in the vicinity of 27. The frontal line between 27-29 extends from 105 to 102.5 in the southeast-northwest direction. The south phase of the frontal line extends to 23 southwardly.(5) The kinematic frontogenesis formula is used to calculate the frontogenesis function of the Kunming quasi-stationary front day-by day. The result shows that there are indeed high value zones of frontogenesis function nearby the mean position of the Kunming quasi-stationary front. The position and shape of the center of high frontogenesis function value zone are consistent with location of the frontal line. This consistency shows that frontogenesis function can describe the generation and maintenance of Kunming quasi-stationary front.On the other hand, it can also reflects the method about process selection of Kunming quasi-stationary front in the second chapter is feasible. By comparing the average intensity of frontogenesis, the vital items for frontogenesis are Identified. Horizontal divergence and horizontal shear iterms play major roles in the frontogenesis of Kunming quasi-stationary front, while the effects of vertical motion associated tilting can be ignored. But the change of diabatic heating is ahead of frontogenesis.(6) The genesis mechanism of Kunming quasi-stationary front is phrased as that the releasing of latent heat near the Kunming quasi-stationary front heat the air column, then a thermally indirect circulation formed and triggered the genesis of front by increasing the temperature gradient. Then frontogenesis theory of horizontal movement can explain the development of Kunming quasi-stationary front well.