A Synoptic Study of the Inversion during the AMTEX '74
1975 Volume 26 Issue 4 Pages 121-147
Details
1975 Volume 26 Issue 4 Pages 121-147
Analyses of the synoptic dat a during the AMTEX '74 revealed the spatial and time variations of the inversion layer over the AMTEX area. The quasi-stationary inversion formed between 700 mb and 850 mb and covered a considerable wide area from the Yellow Sea to the southwest Pacific.
The formation of inversion was mainly attributed to free convection above the warm sea surface and isentropic sloping down at middle level during the period of cold air outbreak. As a result vertical transport of heat energy from the sea was stopped at the inversion.
After the cold air outbreak, the southerly f low replaced the northerly flow. Even at this stage the inversion was recognizable between the southwest winds in the lower layer and the steady westerlies above 700 mb. The thermal stratification below the inversion, however, became more stable, and the height of the inversion base rose. When a synoptic disturbance was approaching to the area, moist and dry tongues were formed in the sub-inversion layer. The scales of the tongues were a few hundred kilometers. The formation of this sharp gradient of water vapour was related to the vertical circulation below the inversion rather than the horizontal advection of vapour. At this time a secondary low-level inversion was often formed.
A few time s the inversion partly disappeared through large-scale upward motion of air, and an ensemble of cumulus convection developed.
The cloud shield above the inversion was dependent on the moisture content of air coming from the China continent and the adjacent sea.
The numerical analysis of static stability between 850 mb and 700 mb showed that: (1) Differential advection of potential temperature and vertical net transport of stability were equally important to the change in the stability when adiabatic condition was applicable. (2) During the period of cold air outbreak, diabatic heating in the lower layer played an important role in compensating the surplus contributions of the two terms.
