Analysis of a Cyclone in Middle Latitudes Near Japan (I)

[摘要] Using the surface autographic records and aerological data, the author analyzed synoptically an abnormaly developed cyclone over the sea south of Kamt_??_hatka in the second decade of January 1950, with reference to the mechanism of development of cyclone, the movement of cold dome, the outburst of NW monsoon in winter, the vertical structure of cyclone and deep cold trough and the manner of appearance of front or squall line on autographic records. The main results obtained are as follows: (1) This cyclone is accompanied by a marked tropopause low independently of a deep cold trough at first, and so the existence of large downward motion can be assumed at upper layers above the cyclone center before the development of cyclone. The vertical structure of this cyclone is shown in Fig. 11 (it is the same as shown by Palmén except the uppermost layer) and we can show that the necessary conditions for development of cyclone are the large magnitude of mass divergence at middle layer and the downward motion of lower tropopause or layer aloft. But it seems that the latter condition played the main part for deepening of this cyclone.(2) A marked animate growth of cyclone due to the amalgamation of isalobaric lows, by a deep cold trough advancing after cyclone, and the cyclone itself was performed and then discontinuous rapid deepening was done.(3) Then the tropopause low accompanied by cyclone separated from the lower cyclone and at this time the deepening of cyclone ceased. Afterward the amalgamation of both lows was done again and then the cyclone reached its maximum development. Therefore we can know the importance of tropopause low for deepening of cyclone.(4) The NW monsoon comes to weaken when the depth of cold dome has decreased to almost 700 mb and the change of depth has become small.(5) The autographic records by passage of the cold front and prefrontal squall line are shown in Figs. 3, 4 and 5. The prefrontal squall line is accompanied by the pressure jump and that is the same as shown by Moris Tepper in 1950 except the temperature rise due to adiabatic compression of the layer under the inversion level by sudden pressure rise. After the passage of surface cold front, the marked stepwise change of weather elements as shown in the figures appeared. This will be due to the instantaneous downward motion in cold dome.

[学科分类] 大气科学