2020 Volume 67 Issue 6 Pages 331-342
Synoptic- and meso-α-scale variations of Baiu frontal cloud-precipitation systems over Japan in July 1982 are studied using observation data to clarify the relationship between meso scale phenomena and synoptic fields.
The temperature variation at the 500hPa surface was large in middle latitude (to the north of the Baiu frontal zone). During the period of low temperature in mid-July, predominant upper troughs passed over Japan. Baiu frontal depressions, and cloud-precipitation systems also developed. Significant variations of cloud/precipitation systems with 〜 2 day period appeared in 5-20 July. In 23-24 July, after the cold period, record-breaking precipitation occurred in Kyushu.
The south-north gradient of the moist static energy, vertical stability in the frontal zone varied in association with passage of the major upper troughs. The Baiu frontal depressions, cloud systems in the frontal zone varied in association with these variations of the frontal zone.
Major troughs in the lower troposphere were accompanied with the major upper troughs. However, minor trough in the lower troposphere seen in 17 July was not associated with upper trough. Most of Baiu frontal depressions and cloud-precipitation systems developed under the influence of the troughs in the lower troposphere. However, the depression with intense precipitation in 23-24 July was not associated with significant trough. Features of the cloud-precipitation systems varied from case to case. In some cases, they formed “cloud system family in the Baiu frontal zone”.
The synoptic-scale features found during July 1982 are compared with those in previous reports. Although, synoptic-scale features in this period are commonly found in other periods, some differences of features are seen among the periods. This report also shows that features of cloud-precipitation systems varied significantly depending on synoptic fields.