Sensitivity of tropical‐cyclone models to the surface drag coefficient
Abstract
Motivated by recent developments in tropical‐cyclone dynamics, this paper re‐examines a basic aspect of tropical‐cyclone behaviour, namely, the sensitivity of tropical‐cyclone models to the surface drag coefficient. Previous theoretical and numerical studies of the sensitivity in axisymmetric models have found that the intensity decreases markedly with increasing drag coefficient. Here we present a series of three‐dimensional convection‐permitting numerical experiments in which the intensification rate and intensity of the vortex increase with increasing surface drag coefficient until a certain threshold value is attained and then decrease. In particular, tropical depression‐strength vortices intensify to major hurricane intensity for values of CK/CD as small as 0.1, significantly smaller than the critical threshold value of about 0.75 for major hurricane development predicted by Emanuel using an axisymmetric balance model. Moreover, when the drag coefficient is set to zero, no system‐scale intensification occurs, despite persistent sea‐to‐air fluxes of moisture that maintain deep convective activity. This result is opposite to that found in a prior axisymmetric study by Craig and Gray.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Oct 01, 2010
- Source ID
- 10.1002/qj.702
Entities
People
- Michael T. Montgomery
- Roger K. Smith
- Sang V. Nguyen
Organizations
- National Science Foundation
- Office of Naval Research