Further Studies of a Prefrontal Convective Rainband During TAMEX IOP 13 Part II:Kinematic Structure and History

Abstract

Doppler radar data collected at 7-min intervals by the TOGA radar during TAMEX IOP 13 were used to investigate the time-dependent kinematic structure of the Mei-Yu front and the associated rainband as it made landfall on the western shore of Taiwan. Using RHI cross sections, chosen to be nearly perpendicular to the approaching Mei-Yu front, the vertical velocities and divergences were calculated. Using these data, the time-dependent kinematic structure of the Mei-Yu front and prefrontal convective rainband were analyzed. A careful analysis shows that high speed mid-level dry flow pushes the high reflectivity cores at the Mei-Yu front southeastward into the warm sector. In addition, evaporative cooling associated with a strond dry-air intrusion at mid to upper levels combines with precipitation loading to create convective downdrafts in a wide-spread area ahead of the Mei-Yu front. The low-level cold outflow form the downdraft interacts with the moisture-rich southwest monsoon flow creating a gust front. A smaller portion of the downdraft is also directed back to the Mei-Yu front sustaining the front. These structures provide further evidence supporting the conceptual model put forth in Lin et al. (1992).

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