Bulk Properties of Cumulus Convections in the Small Area over Kuroshio Region

Abstract

The bulk thermodynamical property of the cumulus convections within the small area (about 4×(100km)2) over the Kuroshio region is studied analytically by means of the atmospheric heat energy budget in February 1968.
The situations of cumulus convections in the area are classified from the PPI radar observa tions into three categories, i.e., the situation of “echo cluster”, “weak echo” and “no echo”.
The statistics of the mean vertical velocity (ω), individual changes of temperature and mixing ratio of water-vapor (δ1T/δt and δq/δt) and the horizontal convergence of water vapor (∇Vq) indicate the characteristic bulk thermodynamic property for each category of the echo situation.
The bulk property of “echo cluster” is characterized by the strong upward motion, large positive value of δT/δt and large negative value of δq/δt in the middle troposphere and large negative value of ∇Vq in the lower atmosphere. The bulk property for the situations of “weak echo” and “no echo” are characterized by the weak downward motion, small positive value of δT/δt, δq/δt and ∇Vq.
The structure of the disturbances of synoptic and medium-scale associated with the echo cluster are also studied by analysing the time series data of aerological observations.