Variation in the Heat Energy Budget over the East China Sea Associated with the Passage of Wave Cyclones in February 1968

Abstract

The air-mass modification is very remarkable over the East China Sea in wintertime, where the warm sea current Kuroshio is very warm. The variation in the heat energy budget situation over this area is studied during 20-day period in February of 1968. From the analyses of ESSA cloud pictures and data of aerological and radar observations, it is shown that the wave disturbances with a period of about 4 days predominate over the analysed area. The synoptic situation in the lower troposphere as well as the situation of the heat energy budget varies remarkably when the wave cyclone passed over this area. The synoptic situations of this area are classified into two typical situations, i.e. the cold air outbreak occurring after the passage of cyclones and the northward invasion of the subtropical air-mass occurring when the disturbance is located on the AMTEX area.
The budget for the former synoptic situation (i.e the cold air outbreak) is characterized by the large amount of heat energy supply from the sea and the large positive value of individual change of temperature and mixing ratio in the lower troposphere under the stable layer. The influence of air-mass modification is confined within the lower layer since the penetrative convections, which redistribute the heat energy in the free atmosphere, are suppressed by the stable layer which developed in the subsiding polar air mass.
The budget for the latter synoptic situation is characterized by the strong convergence of water vapor flux in the lower troposphere, very large positive and negative values of the individual change of temperature and mixing ratio in the middle troposphere. More than 30% of the heat energy, which supplied from the sea surface, is transported upward across the 700-mb surface through the work of cumulus convection developing in the thick layer of moist neutral stratification.