On the Structure of the “Baiu Front” and the Associated Intermediate-scale Disturbances in the Lower Atmosphere

[摘要] During the 4-day period of project observation, July 8-July 12, 1968, the “Baiu front” activity was prevailing almost steadily over the Far East.Therefore the averaged fields of various meteorological elements in the vicinity of “Baiu front” are examined. The most remarkable structure is found not in the thermal stratification but in the wind field with a low-level jet which is considerably ageostrophic. The existence of low-level jet stream seems to be deeply related with the precipitation and, therefore probably, with the connective activity.Along the concentrated zone of strongly baroclinic field, lower tropospheric disturbances of wave lengths less than 1, 000km were generated and moved east-northeastwards successively, bringing a large amount of precipitation periodically at an interval of about 20 hours. The associated thermal field indicated the existence of indirect circulation, but, nevertheless, disturbances did develop.The energy conversion processes among three different scales of motion, i. e., general synoptic scale, intermediate scale (frontal disturbances) and small scale (convection) are studied. It is suggested that the kinetic energy of intermediate-scale disturbances is transformed from the kinetic energy of convective-scale motion.

[学科分类] 大气科学