Roll Clouds Associated with an East Asian Cold Front

On 11 January 1998, a cold front formed in southeast China as a result of a cold-air outbreak in northeast Asia. During this synoptic development, a series of roll clouds (along the SW–NE direction) was observed in East Asia; some of the clouds stretched for over a thousand kilometers. This roll cloud formation moved southeastward across Taiwan, the Ryukyu Islands, and Japan, and eventually into the open ocean. In order to explore the possible cause of these roll clouds the following preliminary analyses were made in this study: These observations imply that the series of roll clouds formed in association with solitary wave disturbances generated on the density current (i.e., the outflow from the cold-air break) but behind its leading edge.