East Asia and Western Pacific METEOROLOGY AND CLIMATE

168
In order to understand the internal circulation of this long-lived cell, the
single Doppler analysis at 0701, 0802 and 0856 LST were shown in Fig. 11. Prom
these three successive echo configurations with overlaid radial wind, we noted that
the configurations of the cell were almost steady and the isodops showed sharp
turning. This signature indicated that a clear wind shear line just located at the
back edge of reflectivity core(> 30 dBZ). From the configuration of isodops we
observed the strong southwesterly LLJ heading toward the shear line. To the rear
side of the shear line the westerly flow met the southwesterly one and created strong
convergence.This southwesterly low level jet was responsible to supply the moisture
to this prefrontal precipitation system as described in Browning and Pardoe(1973).
A cross-section pendicular to the shear line was illustrated in Fig. 12 ( the position
of the crossection was marked in Fig. 11) 30 dBZ contours were tilted toward the
southeast direction. From Fig. 12, at the lowest level 0.5km we can identify that the
shearline position was at x=-16 km, a strong convergence zone near this shearline
was found .Consequently a strong updraft will erect right above this region. From
5km to 15km height to front side of updraft, a strong wind component blowing
toward the southeast (northwest wind 16ni/sec) was observed, while only about
9m/sec north-west wind at this levle was observed on the rear side. Obviously, an
outflow region was located above updraft center. At 5 km height a convergence
was found near 24 km to the northwest of the strong convection, this convergence
resulted in a rear flank downdraft.
6. CONCLUSION
Based on the digital radar data, a detailed discussion of the reflectivity characteristics
such as horizontal pattern, vertical structure and movement was illustrated.
In order to understand the kinematics of the convective systems in TAMEX
phase I, the internal motion fields were also calculated through the TREC technique.
The TAMEX case study indicate that within the MCS rainband, a few very
long-lived cells along the shear line develop and maintain its three dimensional
structure. During its long life cycle, the 3-D airflow may evolved into supercell-like
pattern with strong rotational characteristics. From the configuration of isodops
we observed the strong southwest LLJ heading toward the shearline. To the rear
side of the shear line the westerly flow met the southwesterly and created strong