Geoscience Reference
In-Depth Information
AN INVESTIGATION OF WINTER RAINFALL
AND SNOWFALL IN THE MOUNTAIN
AND COAST
HYO CHOI
Department of Atmospheric Environmental Sciences
Kangnung National University, Kangnung 210-702, Korea
du8392@hanmail.net
The case study of snowfall in the mountainous coastal region of Korea had been
undertaken from 09:00 UTC December 6, 2002 through 12:00 UTC December 9,
2002, using 3D-numerical model, MM5 V3.5 with NCEP data inserted as initial
input data for the model. During the snowfall period, north-easterly wind and
easterly wind in a high-pressure system in north and a low pressure in south
of Korean peninsula prevailed in the eastern mountainous coastal region and
sensible heat flux induced a great amount of evaporation from the sea surface.
This wind could drive the moisture transported from the East Sea-coastal
area toward the top of mountain in the west and uplifted moisture should be
cooled down and saturated, under westerly cool air masses, resulting in the
formation of ice and rain particles inside low cloud. Snowfall band coincided
with minimum sensible heat flux band or zero value area, where maximum
cooling of air parcels occurred. This snowfall band also directly coincided with
the area of relative humidity of 100%. As air temperature at the level of cloud
base was below 0
◦
C, water droplet of cloud formed ice crystal phase like snow.
As stratocumulus type low clouds moved down toward the ground surface of
coastal area, the falling droplets remained snow phase without melting of snow
due to the short distance to the ground. Vertical distribution of total cloud
mixing ratio, air temperature and relative humidity gave detail information
on the height of cloud formation, the determination of snowfall or rainfall of
droplets and snowfall area. Under north-westerly wind parallel to the coast,
moisture advection became very weak, resulting a small amount snow or no
snow in the coast.
1. Introduction
The driving mechanisms on snowfall or winter rainfall are basically similar,
but the prediction of snowfall is quite different from one of rainfall. It is
generally due to the reason how much cooling is necessary to make for
the formation of snowfall. The development of snowball is greatly affected
by cooling of water droplets, due to orography in the mountain
1
-
4
and by
enough supplying of moisture through the transfer of moisture evaporated
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