On the Theory of Cyclones

On the Motion of a Typhoon (I)

“…The equations of motion are given by (1) where x and y are cartesian coordinates, positive towards the east and towards the north respectively, p and a are the pressure and the specific volume of the air respectively. f and B are the Coriolis factor and its meridional gradient respectively.…”

On cyclogenesis in the lee of the Canadian Rocky Mountains

“…The maxima are maintained in all seasons. Petterssen [15,17] examined the effect of a mountain barrier on the flow pattern on an isentropic surface, and showed that oQ Ot -v3"(QV' +Q 8wn -an (1) It is seen that the local change of the absolute vorticity Q in a unit volume on an isentropic surface is determined not only by the import of vorticity into a unit volume in this surface, but also by the intensity of the vorticity source, 1, the most pronounced maximum in North America lies in the lee of the Alberta Rockies while other maxima are associated with the Colorado Rockies, and the Sierra Nevada where thermal lows frequently occur as well.…”

“…V. Bjerknes [2] and collaborators in 1911 demonstrated the occurrence of stretching and convergence on the lee slope and described the production and characteristics of eddy motion in the following manner: A motion going on without eddies is kinematically possible, but dynamically unstable, and had therefore no chance of persisting even if it be produced for a moment ... and on the leeward side of a mountain the eddies being the most frequent ... Eddies having a vertical axis may be formed in the same way. Considering lee cyclogenesis in the light of new aerological data, J. Bjerknes and Holmboe [1] concluded that the divergence fields could be superimposed on baroclinic waves in a westerly current over mountains. The eddies can exist on every scale, down to the smallest, which must be considered as local disturbances.…”

Summer Upper-Level Vortex over the North Pacific

“…4 suggests that the vortex is reasonably depicted by the NCEP-NCAR reanalysis data. 2) Ascending motions associated with midlatitude cyclones (e.g., Bjerknes and Holmboe 1944;Chen et al 1996), equatorial waves (e.g., Reed and Reeker 1971), and monsoon depressions (e.g., Saha and Saha 1988) always exist within these disturbances to form a direct secondary circulation. induced by the vertical motions depressions, except for the fact that cyclonic vortices of these two types of synoptic disturbances exist in the lower half of the troposphere.…”