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Variations of energetics of cyclones in the mid-latitude North America, 1948--2000
Variations in energetics of cyclones in the midlatitude North America are examined and changes of the cyclone energetics are found with the climate warming since the late 1970s. Generation, horizontal and vertical transports of energy are found to drastically increase after 1978 indicating that cyclones of both cold and warm seasons are more energetic in the warmer period since 1978 than those in the relative cool period of 1948-78. ^ Excess production of potential energy in the warm climate resulted in large generation of available potential energy in both warm and cold seasons. However, large amount of the resulting available potential energy is not converted into kinetic energy. This indicates changes in the efficiency of the atmospheric engine during cyclone activities, especially in winter. ^ The strengthening of cyclones in the warm season of the recent decades can be attributed to a stronger jet stream centered at a lower elevation in the troposphere, while the enhanced cold season cyclones in the warmer climate are found to be associated with the westerly jet centered at a higher elevation of the troposphere. From mid-troposphere to the jet in winter, increase in temperature and meridional wind caused significant development and strength of eddy motion leading to the observed upward displacement of the winter jet. Associated with this elevated jet stream is the enhanced baroclinicity in the upper troposphere in boreal winter. ^ The variations in the energetics of warm and cold season cyclones in the midlatitude North America found in the present study invite more research on the possible consequences of climate warming. Changes in the characteristics of various atmospheric phenomena in the warming climate are still unknown. Examples among the several unknowns are the transition mechanisms from tropical to extratropical cyclones. This transition occurs when a tropical cyclone moves into the midlatitudes and acquires midlatitude characteristics. Studies of the energetics of extratropical cyclones will explain not only the transition mechanisms but also the changes of these transition mechanisms when the climate gets warmer.^
Tawaye, Yacoubou, "Variations of energetics of cyclones in the mid-latitude North America, 1948--2000" (2007). ETD collection for University of Nebraska - Lincoln. AAI3255460.