Abstract
The atmospheric heat energy budget over the Kuroshio region has been analysed for the period of polar air outbreak (cold period for short) in AMTEX '75. The situations of this period are somewhat different from those in AMTEX '74 described in Ninomiya and Akiyama (1976).
Three undisturbed periods of polar air outbreak, i.e., Period I (25-27 February 1974), Period II (15-16 February 1975) and Period III (20-23 February 1975) are selected for comparison.
Period I is characterized by the weak subsidence of the polar air mass and large amount of precipitation (˜5mm/day) from the cloud layer capped by the inversion layer which distinctly separates the northerly subinversion layer from westerlies aloft. Periods II and III are characterized by the non-precipitating cloud layer capped by the inversion existing in the thick subsiding polar air mass.
The large apparent heat and moisture sources in the subinversion layer are commonly found for the three periods. Significant differences among these periods are found in 175˜'250mb (p*) layer including the inversion base. In Period I, both apparent heat and moisture sources show rapid decrease above the inversion. In Periods II and III, maximum of apparent moisture source and maximum of apparent heat sink are found around the inversion base, which are accounted for by the evaporation from the top of the non-precipitating cloud layer.
The results of comparison evidently demonstrate the difference between the energy balance in the precipitating and non-precipitating cloud layers and the controlling influence of large-scale subsiding motions upon the thermodynamic . process of the polar air-mass transformation.
