[A-AS10] General Meteorology

[AAS10-P06] Characteristics of local wind systems and temperature during nighttime in recent summer over the Kanto Plain

*Yoshihito Seto¹ (1.Department of Geography, Graduate School of Urban Environmental Sciences, Tokyo Metropolitan University)

Keywords:Local wind system, Land and sea breeze, Temperature distribution, Kanto Plain

Recent changes in local wind systems and temperature distribution during calm and clear nights in summer over the Kanto Plain were studied using 40-year dense surface observation data. In the early morning, northwesterly to westerly land and mountain breezes were observed over most of the Saitama, Tokyo, and Kanagawa Prefectures. However, over the last 20 years, land breezes typically did not reach the coast of Tokyo Bay, and a change in wind direction toward the southwest was observed in the Tokyo metropolitan area and eastern Kanagawa Prefecture. The factors behind these changes include an increase in the frequency of nights during which there was no transition to land breezes, and a tendency for land breeze development to be delayed, even on nights when land breezes reached the coast of Tokyo Bay. When land breezes did not reach the coast of Tokyo Bay, temperatures tended to be high due to the prevailing southerly winds during the night, and the early morning temperatures were notably high on the northern coast, where there was no transition to land breezes. These findings suggest a relationship between the recent changes in nocturnal wind systems and the trend toward frequent high-temperature nights on the Kanto Plain.