A Multiscale Study of Tropical Cyclone Formation, Structure Change, and Predictability in the Western North Pacific Region and TCS08 Experiment Support

LONG-TERM GOALS AND OBJECTIVES: The overarching objectives of this research project are to obtain an improved understanding of the formation, predictability and structure change of tropical cyclones in the Western Pacific region. During the second year of this project multiple cases have been analyzed in support of the Tropical Cyclone Structure 2008 (TCS08) field campaign. Because of space constraints, only a brief summary of these extensive results is presented here.Award Number: N001408WR2012

Continued Analysis on Multiscale Aspects of Tropical Cyclone Formation, Structure Change and Predictability in the Western North Pacific Region as Part of the TCS08 DRI

2012 ANNUAL REPORT FOR ONR SPONSORED RESEARCHLONG-TERM GOALS AND OBJECTIVES: The overarching objectives of this research project are to obtain an improved understanding of the formation, intensification, predictability and structure change of tropical cyclones in the Western Pacific region. These new insights will ultimately improve forecast guidance for U.S. Naval operations in this region.ONRN0001411WX2009

A Lagrangian analysis of a developing and non-developing disturbance observed during the PREDICT experiment

Atmos. Chem. Phys., 12 11355-11381The article of record as published may be located at http://dx.doi.org/10.5194/acp-12-11355-201

Point-vortex application to vortex stability, evolution, and statistical equilibrium

June 1995.Also issued as John Persing's thesis (M.S.) -- Colorado State University, 1995.Includes bibliographical references.The nonlinear evolution of an isolated, barotropic vortex in an infinite, frictionless domain is examined with a cloud of like-signed point-vortices. The stability of systems of point­ vortices is reviewed as well as the stability of continuous systems possessing a sign reversal in the radial vorticity gradient like that observed in the inner core of hurricanes. The new result is the application of point-vortices to examine the evolution of a hurricane­ like vortex system. Using a three-region approximation to the radial vorticity profile, the nondimensional problem can be reduced to two parameters. These are the inner radius of the vorticity maximum 8 and the tangential wind speed at this radius Vtan(8). The relaxation time scale is on the order of five circuit times, and the relaxed vorticity profile ranges from near solid-body rotation to highly monopolar profiles. The relaxation time-scale and the monopolicity of the relaxed vorticity profile show some correlation to the strength of the linear instability in the initial system, although a more thorough examination of the parameter space is proposed to obtain a complete understanding of the processes involved in the relaxation.Sponsored by the Office of Naval Research grant ONR-N00014-93-1-0456

Evaluation of a Heuristic Model for Tropical Cyclone Resilience

The article of record as published may be found at http://dx.doi.org/10.1175/JAS-D-14-0318.1This work examines the applicability of a previously postulated heuristic model for the temporal evolution of the small-amplitude tilt of a tropical cyclone–like vortex under vertical shear forcing for both a dry and cloudy atmosphere. The heuristic model hinges on the existence of a quasi-discrete vortex Rossby wave and its ability to represent the coherent precession and tilt decay of a stable vortex in the free-alignment problem. Linearized numerical solutions for a dry and cloudy vortex confirm the model predictions that an increase in the magnitude of the radial potential vorticity (PV) gradient within the vortex skirt surrounding the core yields a more rapid evolution of a sheared vortex toward the equilibrium, left-of-shear tilt configuration. However, in the moist-neutral limit, in which the effective static stability vanishes in rising and sinking regions, the heuristic model yields a poor approximation to the simulated vortex core evolution, but a leftof- shear tilt of the near-core vortex, radially beyond the heating region, remains the preferred long-time solution. Within the near-core skirt, the PV perturbation generated by vertical shearing exhibits continuousspectrum- type vortex Rossby waves, features that are not captured by the heuristic model. Nevertheless, the heuristic model continues to predict the rapid vertical alignment and equilibrium, left-of-shear tilt configuration of the simulated near-core vortex in the moist-neutral limit.The first author (P. D. R.) would like to acknowledge support from NSF ATM-0514199. Both authors would like to thank Dr. David Schecter for stimulating discussions that helped motivate this study and for his insightful comments on the manuscript, including the comment that motivated Eq. (15).We would also like to thank two anonymous reviewers for their substantive comments, which have helped clarify both thought and presentation. The second author (M. T. M.) would like to acknowledge support from NSF AGS- 0733380, AGS-1313948, NOAA’s Hurricane Research Division, and the U.S. Naval Postgraduate School

The generalized Ekman model for the tropical cyclone boundary layer revisited: Addendum

17 USC 105 interim-entered record; under review.The article of record as published may be found at http://dx.doi.org/10.1002/qj.4012Motivated by prior research examining the myth of inertial stability as a radial restoring force in the tropical cyclone boundary layer, we explore factors deter mining the vertical velocity at the top of the linear vortex boundary layer. Possible applications of these findings to mature tropical cyclone vortices are discussed briefly.NSFONRAGS-1313948 and IAA-1656075N0001417WX 00336,U.S. Naval Postgraduate Schoo

Circumpolar vortex studies using MSU temperature data

October 1996.Also issued as Paul D. Reasor's thesis (M.S.) -- Colorado State University, 1996.Includes bibliographical references.Irreversible mixing associated with breaking planetary waves at the edge of the circumpolar vortex exerts a westward force on the atmosphere. The tendency of this wave forcing is to decelerate the polar right jet and warm the polar regions of the stratosphere. While the tendency is opposed by an induced Eulerian-mean circulation, it is observed that substantial reductions in jet strength and departures from radiative equilibrium still occur. In the steady-state limit the departures from radiative balance at any level may be accounted for by the total wave forcing above that level. The wave forcing, and hence vortex strength, varies from year to year in a biennial fashion, suggesting a link with the equatorially-confined quasi-biennial oscillation (QBO) (Tung and Yang, 1994). These ideas will be explored in the context of a seasonal and interannual study of the austral circumpolar vortex using brightness temperature data from the Microwave Sounding Unit (MSU). Observations of the seasonal evolution of the vortex are presented along with direct and indirect evidence of wave forcing. A 50-mb vortex circulation index derived from the MSU is shown to qualitatively correlate with the phase of the QBO in some years. It is concluded, however, that the effects of wave forcing may be too weak in the lower stratosphere to consistently observe a QBO signal at high latitudes.Sponsored by the Cooperative Institute for Research in the Atmospheric (CIRA)

An axisymmetric view of concentric eyewall evolution in Hurricane Rita (2005)

J. Atmos. Sci., 69 2414-2432The article of record as published may be located at http://dx.doi.org/10.1175/JAS-D-11-0167.

Optical processing for distributed sensors in control of flexible spacecraft

A recent potential of distributed image processing is discussed. Applications in the control of flexible spacecraft are emphasized. Devices are currently being developed at NASA and in universities and industries that allow the real-time processing of holographic images. Within 5 years, it is expected that, in real-time, one may add or subtract holographic images at optical accuracy. Images are stored and processed in crystal mediums. The accuracy of their storage and processing is dictated by the grating level of laser holograms. It is far greater than that achievable using current analog-to-digital, pixel oriented, image digitizing and computing techniques. Processors using image processing algebra can conceptually be designed to mechanize Fourier transforms, least square lattice filters, and other complex control system operations. Thus, actuator command inputs derived from complex control laws involving distributed holographic images can be generated by such an image processor. Plans are revealed for the development of a Conjugate Optics Processor for control of a flexible object

Lagrangian Coherent Structures in tropical cyclone intensification

Atmos. Chem. Phys., 12 5483-5507The article of record as published may be located at http://dx.doi.org/10.5194/acpd-11-1-201