Sort Options:

• Sort By Last Name
• Sort By Title

Other:

• Print All

Sort by time-scale:

• Short
• Intermediate
• Long
• SHOW ALL

The Importance of Vortex Rossby Wave Breaking and Radiation for Angular Momentum Transport in Hurricanes

The Importance of Vortex Rossby Wave Breaking and Radiation for Angular Momentum Transport in Hurricanes

G. Brunet1, Y. Martinez2, P. Yau2, M. Desgagn�1 and Xingbao Wang2
Affiliations:

1.Meteorological Research Division, Environment Canada, Canada
2.Department of Atmospheric and Oceanic Science, McGill University, Canada

In Chen et al. 2003 (J. Atmos. Sci.) it was demonstrated that in an idealized simulation of an intensifying hurricane that vortex Rossby waves (VRWs) explain a significant amount of the wave activity. The diagnostics based on Eliassen-Palm (EP) flux, and its divergence, show that the VRWs are concentrated in the inner-core region where the radial gradient of the basic state potential vorticity is large. In general, these waves propagate outward in the lower troposphere and inward in the upper troposphere. The VRWs lead to significant wave-mean-flow interaction, as indicated by the divergence of the EP flux, with tangential wind acceleration of order 1-2 m/s per hour in the vicinity of the eyewall region. The VRWs show also characteristics typical of flow with critical layer and sheared disturbances. In case of monotonic angular wind distribution, the VRW critical level position depends on the VRW characteristics: intense (weak)hurricanes have their VRW critical layer close (far away) to their inner-core due to their fast (slow) phase speed. Hence these mesovortices are responsible for the dynamical processes controlling the redistribution of angular momentum from the inner core to the far field. It then seems that strong hurricanes are relatively more efficient in retaining their angular momentum than weak hurricanes that tend to radiate away their angular momentum.

These wave processes have been studied using wave activity diagnostics, like in Chen et al. (2003, JAS), in a series of high resolution tropical simulations of hurricanes Earl (September 1998) and Isabel (September 2003), using the Environment Canada MC2 non-hydrostatic LAM and the high resolution PSU-NCAR nonhydrostatic mesoscale model MM5 respectively, which resolves the convective scale and the critical layer. These simulations and others with lower resolution will be used to comment the role of these vortex Rossby waves in the angular momentum transport in hurricanes. We will point out also the expected implication of these results in the context of systematic errors in numerical weather prediction and climate models at different space-time resolutions for intensifying and mature hurricanes of different strengths.

References:

Chen, Y., G. Brunet and P. Yau 2003 Spiral bands in a simulated hurricane PART II: Wave activity
diagnostics J. Atmos. Sci. , 60, 1239-1256.