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

Abstract

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 600km 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 100km off the west coast of Hokkaido and 70-80km 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.