P1.6
Role of diabatic potential vorticity during hurricane genesis
Leela Ramaswamy, Florida State University, Tallahassee, FL; and T. N. Krishnamurti
This study explores potential vorticity budgets from the complete Ertel’s potential vorticity equation during hurricane genesis. The data sets for these experiments are derived from a high-resolution hurricane forecast that provided reasonable simulation on hurricane genesis. The budgets sort out the relative contribution from the horizontal advection of PV (i.e., related to the conservation of PV in isentropic coordinates), vertical advection of PV (a diabatic contribution), differential heating along the vertical, differential heating along the horizontal, and the frictional contributions. This is aimed to sort out the role of conservation versus non-conservation of PV during the formative stage of a hurricane. The main findings of this study are that conservation of PV was not adequate to explain the large increase in PV during genesis of the storm. The vertical differential of heating made by far the most significant contributions to the changes of PV during the length of the forecast. The vertical advection of PV and the horizontal differential of heating each made smaller contributions to changes in PV, but neither was a significant contributor as compared to the other terms. Our analysis includes parcel trajectories along which the PV components (adiabatic and diabatic) of the complete equation are calculated at intervals of every three hours. These were also cast on isentropic surfaces to assess the role of the nonlinear advection of PV and of the diabatic contributions. In the inner rain area of the hurricane a jump in the value of diabatic PV was noted (related to the vertical differential of heating) that was roughly several times larger than that of the nonlinear advection of PV (the latter relates to the conservation of PV while the former is a measure of the non-conservation).
Poster Session 1, General Poster Session (Hall 4AB)
Monday, 12 January 2004, 2:30 PM-4:00 PM, Hall 4AB
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