Radar reflectivity and wind fields analysis by using two X-band Doppler radars at Okinawa, Japan from 11 to 12 June 2007

摘要

During 11 June (CASE I) and 12 June (CASE II) 2007, several meso-β-scale convective systems (MβCSs) were generated along the Meiyu-Baiu front. In this study, the formation, evolution and dissipation of convective precipitation, kinematics structures, and features of the MβCSs developed over ocean were investigate using dual Doppler analysis. The analysis of synoptic conditions and atmospheric sounding suggested that in both cases the atmospheric environment was characterized by well-developed convective systems with warm and humid air-inflow and unstable conditions in addition to strong vertical wind shear at lower levels. In CASE I, an embedded-cell storm developed, approached the area, and moved slowly (≤2.5m s~(-1)) northeastward. As the system advanced, strong dominant updraft could be observed at the core. After the system passage, the wind became weak at the centre of the cell, whereas the downdraft area extended up to 4 km in height on the front side. This downdraft flowed back into the convective cell and, maintained the convective activity. The evolution of the updraft and downdraft was in good agreement with the general life cycle of convective systems. In CASE II, line-shaped convective systems (LSCSs) passed from the southwest to east-northeast at 10m s~(-1). The dual Doppler analysis revealed that the wind at the rear of the band contributed to the cells merge and developed into a strong convective cell. In addition, the outflow from the new cell flowed into the rear of a merged convective cell and enhanced the vertical development of the cell.