Heavy Rainfall Event in Wuhan Revealed by Barotropic and Baroclinic Mode Evolution of Sub-synopticand Mesoscale Systems
With the filtering method, the sub-synoptic scale and mesoscale informations of the atmosphere flow field are extracted. Then the horizontal wind field of large-and meso-scale are decomposited into barotropic component (vertical mean) and baroclinic component(perturbation) respectively. An analysis of the evolution of barotropic and baroclinic modes of sub-synoptic scale and mesoscale system in a heavy rainfall event in Wuhan during 21—22 July of 1998 is made. The results show that the evolution of barotropic component of the flow field of sub-synoptic scale and mesoscale is closely related to the brewing, development and disappearance of the event. The baroclinic component at 200hPa is strong, the barotropic component at 850hPa is strong, the baroclinicity is dominant. With the development of heavy rainfall, the barotropy will weaken while baroclinicity will get more strong, but the barotropy of current field in sub-synoptic sacle will get strong and the baroclinicity get weaken.