Geoscience Reference
In-Depth Information
from ocean surface toward the land in the coastal region.
5
,
6
In the recent
years, frequent snowfalls have taken in the mountainous coastal area in
Korea. In the coastal sites, we classified three categories such as category
1 — the positions of high pressure system in the north China and low-
pressure system in the south sea of Korea, category 2 — the passage of
trough in the behind region of high pressure through the eastern coastal sea
and category 3 — the couple of a high pressure in north and a low pressure
in south with later another high pressure in west and a low pressure in east
inducing strong easterly wind from the East Sea.
7
,
8
In this study, the case of category 1 was mainly investigated in detail
using a three-dimensional (3D) nonhydrostatical numerical model called
MM5 model, Version 3.5 and driving mechanism on the formation of snow
fall was mainly focused.
2. Numerical Method and Data
A 3D nonhydrostatic grid point model of MM5, Version 3.5 with NECP data
in a terrain following coordinate system was adopted for 4 days numerical
simulation on meteorological phenomena from 09:00 LST, December 6 to
12:00 LST, December 9, 2002 by PC Pentium 4 with one-way triple nest-
ing at Kangnung National University. There were 22 layers in the vertical
spread from 10 m to 10 km with sequentially larger intervals between levels
with increasing altitude.
In the numerical process, a triple nesting were made with grid numbers
of 125
×
105 with horizontal 27 km interval and vertical grid number of 23
in the coarse domain and in the second domain, grid numbers of 82
×
82
with 9 km interval and in the third domain, grid numbers 61
61 with 3 km
interval. About 2.50
◦
interval terrain date was used for the largest domain
and then the 0.9 km interval data was used for fine mesh domain.
MRF method was adopted for boundary layer process in the plane-
tary boundary layer, and simple ice method for the prediction was also
considered. Horizontal and vertical wind and air temperature fields, 3 h
accumulated snowfall amount, mixing ratio inside snow, relative humidity,
and sensible heat flux were evaluated for understanding snowfall event.
×
3. Results
3.1.
Beginning stage of snowfall in the coast
At the beginning stage of snowfall event from 12:00 LST to 18:00 LST, on
December 7, a high-pressure system in the north (north-eastern China) and
