Idealized Experiments of Cyclone Development in the Tropical, Subtropical and Extratropical Environments

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Wataru Yanase (Atmosphere and Ocean Research Institute, the University of Tokyo)
Hiroshi Niino (Atmosphere and Ocean Research Institute, the University of Tokyo)

The development of synoptic-scale cyclones over the global oceans is active in the tropics and the extratropics, and inactive in the subtropics. To clarify the relationship between cyclone development and their environmental field, we performed idealized numerical experiments of cyclone development in which climatological atmospheric conditions are prescribed as zonally uniform environmental fields. The climatological field is examined for the tropics, the subtropics and the extratropics over the western North Pacific in the autumn season, which are characterized by tropical cyclones, few cyclones and extratropical cyclones, respectively. The Japan Meteorological Agency Non-Hydrostatic Model (JMA-NHM) is used with the model domain of 6000 km x 4000 km x ~24 km and the horizontal grid spacing of 10 km. The cloud microphysics scheme and cumulus parameterization scheme are used. The model reproduced the active cyclone development in the tropical and extratropical environments, and inactive cyclone development in the subtropical environment. This result indicates that the environmental field is an important factor for explaining the geographical distribution of cyclone development. The result is not changed qualitatively in additional experiments with different model domains and initial disturbances. The sensitivity experiments show that the inactive cyclone development in the subtropical environment is associated with the horizontal wind and temperature field rather than the humidity field.

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