RESEARCH IN FOUR-DIMENSIONAL DIAGNOSIS OF CYCLONIC STORM CLOUD SYSTEMS.

Abstract : The report consists of two parts: (1) by E. F. Danielsen on the flow and trajectories in a developing wave cyclone as derived from hand analyses on equivalent potential virtual temperature surfaces; (2) by R. Bleck on numerical methods for computing moist isentropic trajectories. Danielsen shows that anticyclonic flow and trajectories predominate in the developing cyclone, with the colder air in advance of the cyclone descending and turning anticyclonically into the storm, while the warmer moist air ascends and predominantly turns anticyclonically away from the storm. The colder dry air turning into the cyclone produces cloudless layers under the moist ascending flow. Precipitation generated in the latter flow evaporates in the colder dry air and cloud layers merge. As the colder, now moist, air approaches the cyclone it ascends and is turned cyclonically around to the rear of the cyclone where it then descends again. The analyses are made by hand because it is impossible to generate the analogue of the Montgomery stream function on moist isentropic surfaces. Bleck discusses two numerical methods for constructing isentropic trajectories which include the release of latent heat. He also shows the resultant trajectories, omega fields, latent heat patterns, individual moisture changes, potential vorticity changes and divergence fields for a developing wave cyclone. (Author)