East Asia and Western Pacific METEOROLOGY AND CLIMATE

308
snowflakes aggregation generates larger particles above
and in the 0 C isothermal layer. Before reaching the
bottom of the melting layer, either the collision-breakup
or the spontaneous breakup process causes a swift
disappearance of these large, wet particles, since the
breakup efficiency increases with particle size.
In the warm-rain region, the collision-coalescence
process is dominant in generating larger particles. Such a
phenomenon is distinguishable in the vertical profile of
median diameter (Fig. 7) after averaging every 200m data
to smooth out the effect of localized turbulence and
horizontal advection. Meanwhile, a few raindrop spectra
below 1.5km (Fig. 8) stress the existence of three peaks
as those proposed by List et al. (1987), etc. for an
equilibrium spectrum maintained through the binary
interactions of coalescence and breakup.
ACKNOWLEDGEMENT
All the analyses done in this paper are executed on
the Micro Vax-II computer located in the Dept. of
Atmospheric Sciences, National Taiwan University through
the support of National Science Council Grant
NSC77-0202-M002-22. The assistance of Miss S. C. Lee is
appreciated.
REFERENCE
Heymsfield, A. J. , and D. Baumgardner,1985:
workshop on processing 2D probe dat&.
Meteor. Soc., 66, 437-440.
Summary of a
Bull. Amer.
, and J. L. Parrish, 1978: A computational technique
for increasing the effective sampling volume of the
PMS two-dimensional particle size spectrometer. J.
Appl. Meteor.,17, 1566-1572,
Johnson, R. H., and G. C. Young, 1983: Heat and moisture
budgets of tropical mesoscale anvil clouds. J.
Atmos. Sci. p . 40, 2138-2147.
List, R., N. R. Donaldson and R. E. Stewart, 1987:
Temporal evolution of drop spectra to collisional
equilibrium in steady and pulsating rain* J. Atmos.,.
Sci., 44, 362-372.
Lo, K. K., and C. M. Liu, 1989: The Microphysics of a
Mei-Yu case: Theoretical study. International
Conference on East Asia and Western Pacific:
Meteorology and Climate. July 6-8, 1989. Hong Kong.