On the Decrease in the Occurrence of Synoptic-scale Transient Disturbances in the Middle Latitudes of the Northern Hemisphere for the Period 1969-1979

[摘要] The occurrence of transient eddies having a time scale shorter than 10 days has been presented for the 850mb and 500mb height fields over a period of eleven years (1969 through 1979) for the Northern Hemisphere middle latitudes. The population of both cyclones and anticyclones contained in disturbances with a duration of longer than 3 days decreased about 1.5% per year. The intensity of the disturbances also decreased during these years.The transport of sensible heat by transient eddies decreased while the total eddy transport of sensible heat remained unchanged. The relation between eddy heat flux and radiative forcing is discussed.

[学科分类] 大气科学