Numerical Simulation of Land-Breeze-Induced Snowbands Along the Western Shore of Lake Michigan

The aim of the present paper is to investigate the formation mechanism of a convergent cloud band which appears east of the Korea Peninsula over the western Japan Sea under northwesterly winter monsoon.Numerical experiments with different surface conditions reveal that the land-sea contrast of thermal property between the Peninsula and the Japan Sea plays the leading role in the formation of the convergent cloud band. Less transformation over the cold land causes a mesoscale high pressure in the lower troposphere with its center at the southeast end of the Peninsula and a convergence zone forms over sea at the eastern margin of it. The convergence zone makes cumulus convections active and organized into a band. In addition, blocking effect of the mountains north of Korea acts to intensify the convergence zone.

Section: Discussionmentioning

confidence: 99%

On the Formation of a Convergent Cloud Band over the Japan Sea in Winter; Numerical Experiments

Nagata¹,

Ikawa²,

Yoshizumi³

et al. 1986

“…Passarelli and Braham (1981) observed shoreline-parallel snowbands and showed that a shallow winter land breeze (only a few hundred meters deep) has an important role in organizing the low-level convergence and in the formation of the snowbands. Ballentine (1982) indicated by numerical simulations that a snowband coincides with a narrow band of upward motion which results from the convergence between a land breeze and an easterly wind over Lake Michigan, and has also shown that latent heat release plays an important role in intensifying the land breeze circulation. Using a mesoscale numerical model, Hjelmfelt and Braham (1983) found that latent heat release plays an important role in strengthening convection, and that the basic mesoscale circulation pattern, including a land breeze, is caused by the lake-land surface temperature difference.…”

Section: Introductionmentioning

confidence: 74%

Doppler Radar Observation of Convergence Band Cloud Formed on the West Coast of Hokkaido Island. II: Cold Frontal Type

Tsuboki

Fujiyoshi

Wakahama

1989

A convergence band cloud moved southwestward through the Ishikari Plain on 20 January, 1986. In this study, we mainly used a single Doppler radar to examine the kinematic and radar echo structures of a convergence band cloud of the cold frontal type. The band cloud, approximately 40km in width, shifted southwestward and accompanied an advancing land-breeze front. The front was geometrically and dynamically similar to that of a gravity current found in laboratory experiments. Kelvin-Helmholtz instability waves with wavelength of 1-2km were observed along the interface of the land breeze and the northwesterly monsoon wind. Two small (*6km) vertical circulations similar to those seen in the warm frontal type were embedded in the mesoscale (*15km) vertical circulation. A low-level convergence and a resultant updraft which were stronger than that of the warm frontal type were located ahead of the front. A distinct subsidence, which is not found in the warm frontal type, followed the front. The updraft caused strong convective echoes ahead of the front, while, owing to the subsidence, the echoes behind the front rapidly weakened. The height of maximum updraft coincided with that of the potential instability layer. The updraft and the potential instability may be responsible for the formation of the convergence band cloud. Based on our observations, we constructed a conceptual model of the formation of the convergence band cloud.

“…Indeed, Ballentine (1982) and Hjelmfelt and Braham (1983) performed a numerical simulation of the convergence cloud over Lake Michigan using a hydrostatic limited area model and indicated that latent heat release played an important role in intensifying the land breeze circulation and the convergence cloud over the lake. The horizontal grid intervals of their models were about 10 km, and the method of cumulus cloud parameterization for the model whose grid intervals are about 10 km has not been established yet.…”

Section: Introductionmentioning

confidence: 97%

Numerical Experiments on Convergence Cloud Bands over the Northern Part of the Japan Sea

Sasaki¹,

Satomura²

1991

Two convergence cloud bands over the northern part of the Japan Sea are simulated with a 2-dimensional non-hydrostatic cloud model and the results are compared with special observations performed by the Japan Meteorological Agency. The model covers 600 km in the horizontal direction and includes Primorskii, USSR, the northern part of the Japan Sea, and Hokkaido, Japan.We successfully simulated convergence cloud bands nearly 100 km off the west coast of Hokkaido and 70*80 km off the east coast of Primorskii.The results show that the cold air from the Asian Continent stops at the west convergence cloud band and the land breeze from the Hokkaido also stops at the east convergence cloud band.Experiments with different lower boundary conditions and physical processes are made to examine the effects of initial wind, surface temperature, latent heat release and orography upon the convergence cloud bands. The results show that the pressure gradient induced by the gradient of the sea surface temperature causes the westerly wind between the two convergence cloud bands. Latent heat release is necessary for convection to develop fully as observed. We also find that both the sea-land temperature difference at the coast of Hokkaido and the initial wind in a lower layer are important factors in determining the position of the east convergence cloud band.