THE EFFECT OF LATENT HEAT ON KINETIC ENERGY CONVERSIONS ASSOCIATED WITH SOUTH PACIFIC CYCLONES
Abstract
Three cyclones which formed in the South Pacific Convergence Zone (SPCZ) during January, 1979 are documented using ECMWF FGGE Level III-b analyses. The FGGE analyses made the study of these cyclones possible for the first time. One cyclone remains in the tropics; the other two propagate southeastward along the western edge of the SPCZ and take on frontal characteristics while still in the subtropics. Analyses of the structure of the SPCZ verify that the region is an active baroclinic zone during the period of study. Temperature anomalies and precipitating convection suggest that latent heat plays an important role in the existence of the SPCZ. Vertical velocities which were partitioned into adiabatic and diabatic components confirm that the forcing by moist processes dominates over that due to dry processes. The role that latent heat has in the life cycles of each cyclone is examined by calculating two terms in the eddy kinetic energy budget: (1) CE, a baroclinic-type conversion, and (2) CK, a barotropic-type conversion. These terms are calculated using the partitioned vertical velocities. Results show that CE is an order of magnitude larger than CK, indicating that baroclinic processes dominate over barotropic processes. In both terms, the contribution by latent heat accounts for nearly all the conversion.
Degree
Ph.D.
Subject Area
Atmosphere
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