Diagnostic Analysis Of Kunming Quasi-Stationary Front When It Shifts And Sustains

Kunming Quasi-Stationary Front(KQSF)is a frequent weather system on the Yun-Gui plateau in southwestern China,which has a great impact on the weather in Yunnan,Guizhou and southern Sichuan.Based on the methods of weather diagnosis,frontal function diagnosis,synthesis analysis,numerical simulation,etc.This paper chooses the most suitable temperature humidity parameters to studying KQSF,discusses the circulation features,characteristics and effects of frontogenesis function,and frontal structures,and reveals the causes of frontal movements and the role of yunnan-guizhou plateau in frontal movements.The main conclusions indicate that:(1)By comparing the potential temperature,equivalent potential temperature,generalized potential temperature and their corresponding frontogenesis functions,we found equivalent potential temperature is the best one to describe the location of KQSF,the frontal strength and the frontogenesis.(2)For the frontal structures,when the isotherm between lower atmosphere and ground presents "V" distribution,and the frontal secondary circulation is relatively deep,the front is easy to move westward;when the lower atmosphere presents deep inversion layer,and the frontal secondary circulation is very thin,the front is tend to move eastward;when the inversion layer only exists in lower atmosphere,and there is a cold center in surface layer,the front tends to sustain.For the vertical structure of the u wind,when the border of east and west wind is on the left side of front,front tends to move westward,on the contrary it tends to go eastward;when the border is basically coincident with front,it's likely to sustain.(3)For frontogenesis in frontal zone,when the front sustains,frontogenetical area is basically coincident with frontal zone,and the phenomenon of frontogenesis is strong.When the font goes westward,the strengthof frontogenesis is increased and the strong frontogenetical area develops upward,and the frontogenetical area is inclined to the left side of the frontal zone.When the front moves eastward,the frontogenetical area only appears in the lower atmosphere,and it is inclined to the right of the frontal zone.(4)For the four components of frontogenesis function,for the non-adiabatic heating term,when the front is obviously moving,the frontogenetical area is consistent with the frontal movement direction;When the front is maintained,this term is related to the "advance at night and retreat during day" of KQSF.For the vertical motion tilting term,there is a strong phenomenon of frontolysis in the windward slope near 105oE when the font goes westward,and is a weak phenomenon of frontogenesis when the font goes eastward or keeps still.For the horizontal divergence term,when the strong frontogenetical area is on the left side of front,front tends to go westward;when it is on the right side of front,and the phenomenon of frontogenesis is weak,front tends to go eastward;when the strong frontogenesis is basically coincident with frontal zone,front tends to sustain.For the horizontal deformation term,and tilting term is more important to frontogenesis.For the expansion deformation term,there is a stronger phenomenon of frontolysis in the east of 104 o E because of the interaction between cold air mass and windward slope.(5)By increasing or decreasing the topography,we find that: when the terrain height is reduced,the quasi-stationary front will be changed into a cold front and go westward rapidly,and the lower the terrain height,the faster the front will move.When the terrain height is increased,the blocking effect of the high altitude area on the cold air mass will increase,and the position of the front maintenance will be more and more east as the terrain height increases.