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How important is the isothermal expansion effect in elevating equivalent potential temperature in the hurricane inner core?



We examine aspects of the thermodynamic structure of mature Atlantic hurricane Earl (2010) based on airborne dropwindsondes released from the upper troposphere during the National Aeronautics and Space Administration (NASA), Genesis and Rapid Intensification Processes (GRIP) experiment. Vertical sounding profiles of the data raise questions concerning the relative roles of isothermal expansion and relative humidity increase in elevating the equivalent potential temperature of air parcels spiralling inwards to the eyewall convection region. The observational results obtained for two successive days of this category 4 hurricane show that the isothermal expansion effect leads to roughly one half of the increment in equivalent potential temperature for boundary-layer air parcels moving between the region outside the eyewall and the eyewall and eye region. Copyright © 2012 Royal Meteorological Society

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