A Study of the Relationship between Low-level Jet and inversion Layer over an Agroforest Ecosystem in East China Plain

1.IntroductionWindprofilewiththerelevantlow--leveljet(LLJ)isoneofthemostimportantfactorsthatcharacterizethestructureoftheatmosphericboundarylayer.TheLLJswerereportedinEurope(SladkovicandKanter,1977;Krausetal.,1985),Africa(Anderson,1976;Hart,etal.,1978),NorthAmerica(Stull,1988;Arrittetal.,1997),Australia(MalcherandKraus,1983;Garratt,1985)andEastAsia(Wangetal.,1996;ChenandHsu,1997).DifferentinvestigatorsuseddifferentcriteriaforidentifyingtheLLJs.SomerequiredwindspeedgreaterthanaParti…

A Study of the Relationship between Low-level Jet and inversion Layer over an Agroforest Ecosystem in East China Plain

The relationship between the super-low-level hi (LLJ) and inversion layer over an agroforest ecosystem on the Huang-Huai-Hat plain in the eastern China is studied by means of a time-independent K-closure model. It is found that the intensified inversion near the surface of a luxuriantly growing agroforest ecosystem leads to the formation and development of the LLJ, the more intense the inversion, the stronger is the LLJ. The critical value of inversion intensity index for the LLJ formation is 0.75'C / 100 m, which relates to the necessary geostraphic wind velocity of 6.0 to 10 m/ s at the top level of the model. The numerical calculations show that the roughness length of the underlying surface has considerable effects on the LLJ structure.