Journal of the Meteorological Society of Japan. Ser. II
Online ISSN : 2186-9057
Print ISSN : 0026-1165
ISSN-L : 0026-1165
Volume 25 , Issue 7-9
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  • R. Sawada
    1948 Volume 25 Issue 7-9 Pages 71-107
    Published: January 30, 1948
    Released: February 05, 2009
    JOURNALS FREE ACCESS
    After one year's experiences of daily aerological map analysis near Japan, we have come to the conclusion that there exist three types of cyclone, the natures and activeties of each type of which are explained as follows;-
    (1) Uoper-layer cyclone:
    It often happens that a moderate low pressure exists in the upper part of troposphere or at the base of stratosphere, having no effect on the surface pressure map. The low pressure takes place usually at the tropopause, some times having Tropopausentrichter with her.
    This is the upper-layer cyclone. She has a barotropic field and so has a vertical axis of center.
    One of examples shown here is the period from Feb. 18th 1943 through Feb. 22nd. Day to day 8 km pressure maps(Fig. 6 to 12) show low pressure moving from west Manchuria to Japan see, track of which is shown in Fig. 13. Surface maps corresponding to this period are Fig. 14 to 19, which show no surface low pressure until the evening of Feb. 22, when 8 km low pressure center came to Japan sea having a corresponding surface low oressure on the sea as shown in Fig. 19.
    As far as the each kilometre height pressure maps of every day are concerned, this low pressure existed only in the upper and middle part of troposphere, having no mark in the lower layer under some 2 km above the sea.
    The upper-layer cyclone takes her tracks along the isobars of 8 km mean pressure map of period covering five or few days (Fig. 32). She is not so active that seldom goes up to well developed surface cyclone.
    (2) Lower-layer cyclone:
    In the lower layer of troposphere, it is every day experience to find cyclones of this kind, characteristic nature of which is the accompanied baroclinic field causing the inclination of axis. According to Laolace's equation of statical equiliorium, center of low pressure goes over the colder area, thus the axis usually inclining to north-westwards in the northern hemisphere.
    Fig. 41 (_??_), (_??_), (_??_)are all typical examples of this kind, in which big points show locations of low pressure centres in the upper layers, height of which layer is shown in kilometres by numbers written aside each point.
    But, as far as the inclination of axis is concerned, there are various kinds of cyclone, one example of whicn is shown as Fig. 42 which has northsouth axis.
    The problem of axis inclination is of dynamical characters, essential elements being the velocity of the cyclone relative to the general current of the field.
    One of the dypamical study by the present author shows that:-
    The axis of cyclone inclines to leewards of, relative general current (velocity of general current relative to the moving cyclone). The paper will be made public very soon.
    (3) Middle-layer cyclone:
    In cold season, we have many continental cyclones travelling, from the west Manchuria to Japan sea, some of them showing very rapid developments during one or two days long.
    How to forecast the big development of this kind is one of the most important problems for us. Well experienced forecaster can do it one or two days before the rapid development by observing the air mass activities on the surface maps only.
    There is, however, a remarkable harbinger of the phenomenon in the middle layer of troposphere.
    That is a middle-layer cyclone, if to be called, which means that a remarkable low pressure developes at the middele neight of troposphere one or two days before the surface cyclone makes her rapid developments. This harbinger can be usually observed on the 5 km pressure maps etc. Corresponding to this middlecyclone there is a slight low pressure area in the upper troposphere, just over the middle-cyclone center.
    An example explained here is the cyclone observed in the period from April 10th 1943 through April 12, which appeared herself in north China on the day of April lOth (Fig. 43), then developed very raoidly (April 12th. Fig. 45).
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