John Persing | Naval Postgraduate School (original) (raw)
Papers by John Persing
We present the results of idealized numerical experiments to examine the difference between tropi... more We present the results of idealized numerical experiments to examine the difference between tropical cyclone evolution in three-dimensional (3-D) and axisymmetric (AX) model configurations. We focus on the prototype problem for intensification, which considers the evolution of an initially unsaturated AX vortex in gradient-wind balance on an f plane. Consistent with findings of previous work, the mature intensity in the 3-D model is reduced relative to that in the AX model. In contrast with previous interpretations invoking barotropic instability and related horizontal mixing processes as a mechanism detrimental to the spin-up process, the results indicate that 3-D eddy processes associated with vortical plume structures can assist the intensification process by contributing to a radial contraction of the maximum tangential velocity and to a vertical extension of tangential winds through the depth of the troposphere. These plumes contribute significantly also to the azimuthally averaged heating rate and the corresponding azimuthal-mean overturning circulation.
The comparisons show that the resolved 3-D eddy momentum fluxes above the boundary layer exhibit counter-gradient characteristics during a key spin-up period, and more generally are not solely diffusive. The effects of these eddies are thus not properly represented by the subgrid-scale parameterizations in the AX configuration. The resolved eddy fluxes act to support the contraction and intensification of the maximum tangential winds. The comparisons indicate fundamental differences between convective organization in the 3- D and AX configurations for meteorologically relevant forecast timescales. While the radial and vertical gradients of the system-scale angular rotation provide a hostile environment for deep convection in the 3-D model, with a corresponding tendency to strain the convective elements in the tangential direction, deep convection in the AX model does not suf- fer this tendency. Also, since during the 3-D intensification process the convection has not yet organized into annular rings, the azimuthally averaged heating rate and radial gra- dient thereof is considerably less than that in the AX model. This lack of organization results broadly in a slower intensifi- cation rate in the 3-D model and leads ultimately to a weaker mature vortex after 12 days of model integration. While az- imuthal mean heating rates in the 3-D model are weaker than those in the AX model, local heating rates in the 3-D model exceed those in the AX model and at times the vortex in the 3-D model intensifies more rapidly than AX. Analyses of the 3-D model output do not support a recent hypothesis concerning the key role of small-scale vertical mixing processes in the upper-tropospheric outflow in controlling the intensification process.
In the 3-D model, surface drag plays a particularly important role in the intensification process for the prototype intensification problem on meteorologically relevant timescales by helping foster the organization of convection in azimuth. There is a radical difference in the behaviour of the 3-D and AX simulations when the surface drag is reduced or increased from realistic values. Borrowing from ideas developed in a recent paper, we give a partial explanation for this difference in behaviour.
Our results provide new qualitative and quantitative insight into the differences between the asymmetric and symmetric dynamics of tropical cyclones and would appear to have important consequences for the formulation of a fluid dynamical theory of tropical cyclone intensification and mature intensity. In particular, the results point to some fundamental limitations of strict axisymmetric theory and modelling for representing the azimuthally averaged behaviour of tropical cyclones in three dimensions.
The purpose of this article is twofold. The first is to point out and correct several misconcepti... more The purpose of this article is twofold. The first is to point out and correct several misconceptions about the putative WISHE mechanism of tropical cyclone intensification that currently are being taught to atmospheric science students, to tropical weather forecasters, and to laypeople who seek to understand how tropical cyclones intensify. The mechanism relates to the simplest problem of an initial cyclonic vortex in a quiescent environment. This first part is important because the credibility of tropical cyclone science depends inter alia on being able to articulate a clear and consistent picture of the hypothesized intensification process and its dependencies on key flow parameters. The credibility depends also on being able to test the hypothesized mechanisms using observations, numerical models, or theoretical analyses. The second purpose of the paper is to carry out new numerical experiments using a state-of-the-art numerical model to test a recent hypothesis invoking the WISHE feedback mechanism during the rapid intensification phase of a tropical cyclone. The results obtained herein, in conjunction with prior work, do not support this recent hypothesis and refute the view that the WISHE intensification mechanism is the essential mechanism of tropical cyclone intensification in the idealized problem that historically has been used to underpin the paradigm. This second objective is important because it presents a simple way of testing the hypothesized intensification mechanism and shows that the mechanism is neither essential nor the dominant mode of intensification for the prototype intensification problem. In view of the operational, societal, and scientific interest in the physics of tropical cyclone intensification, we believe this paper will be of broad interest to the atmospheric science community and the findings should be useful in both the class- room setting and frontier research.
Journal of The Atmospheric Sciences, 2003
High spatial and temporal resolution simulations using the Rotunno and Emanuel axisymmetric, clou... more High spatial and temporal resolution simulations using the Rotunno and Emanuel axisymmetric, cloud-resolving, hurricane model are found to greatly exceed Emanuel's energetically based upper bound for maximum potential intensity (E-MPI).Using a control simulation similar to that of Rotunno and Emanuel with a sea surface temperature (SST) of 26.13°C, the E-MPI is exceeded after 15 simulation days, after the warming of
Journal of Advances in Modeling Earth Systems, 2015
ABSTRACT The purpose of this article is twofold. The first is to point out and correct several mi... more ABSTRACT The purpose of this article is twofold. The first is to point out and correct several misconceptions about the putative WISHE mechanism of tropical cyclone intensification that currently are being taught to atmospheric science students, to tropical weather forecasters, and to laypeople who seek to understand how tropical cyclones intensify in the simplest problem of an initial cyclonic vortex in a quiescent environment. This first part is important because the credibility of tropical cyclone science depends inter alia on being able to articulate a clear and consistent picture of the hypothesized intensification process and its dependencies on key flow parameters; the credibility depends also on being able to test the hypothesized mechanisms using observations, numerical models or theoretical analyses. The second objective of this paper is to carry out new numerical experiments using a state-of-the-art numerical model to test a recent hypothesis invoking the WISHE feedback mechanism during the rapid intensification phase of a tropical cyclone. The results obtained herein, in conjunction with prior work, do not support this recent hypothesis and refute the view that the WISHE intensification mechanism is the essential mechanism of tropical cyclone intensification in the idealized problem that historically has been used to underpin the paradigm. This second objective is important because it presents a simple way of testing the hypothesized intensification mechanism and shows that the mechanism is neither essential nor the dominant mode of intensification for the prototype intensification problem.In view of the operational, societal, and scientific interest in the physics of tropical cyclone intensification, we believe this paper will be of broad interest to the atmospheric science community and the findings should be useful in both the classroom setting and frontier research. This article is protected by copyright. All rights reserved.
Quarterly Journal of the Royal Meteorological Society, 2009
Page 1. QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY QJR Meteorol. Soc. 135: 1697–1714 (... more Page 1. QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY QJR Meteorol. Soc. 135: 1697–1714 (2009) Published online 9 October 2009 in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/qj.459 Do tropical cyclones intensify by WISHE? ...
Quarterly Journal of the Royal Meteorological Society, 2014
ABSTRACT We examine the physical constraints that must be satisfied to allow for a steady-state t... more ABSTRACT We examine the physical constraints that must be satisfied to allow for a steady-state tropical cyclone in an isolated environment, paying particular attention to the need to replenish absolute angular momentum exactly at the rate that it is consumed and to the vanishing of the spin-up function above the frictional boundary layer. We conclude that it is unlikely that these conditions will be met simultaneously and question whether globally steady-state tropical cyclone solutions have merit. The implications for previous studies are discussed.
Monthly Weather Review, 2002
Hurricane Opal (1995) crossed the Gulf of Mexico rapidly intensifying to a 130-kt storm, then for... more Hurricane Opal (1995) crossed the Gulf of Mexico rapidly intensifying to a 130-kt storm, then fortunately weakening before landfall on the Florida panhandle. This intensification was underforecast by the National Hurricane Center. Forecast fields from the 1997 version of the Geophysical Fluid Dynamics Laboratory Hurricane Prediction System (GFDL model) for Hurricane Opal are used to diagnose the rapid intensification of the tropical cyclone. While falling short of the realized peak intensity, the simulation did capture the phase of intensification. This study presents the first step toward diagnosing the mechanisms for intensification within a moderate resolution (ϳ15 km) hydrostatic model and testing the extant hypotheses in the literature.
Journal of the Atmospheric Sciences, 2003
High spatial and temporal resolution simulations using the Rotunno and Emanuel axisymmetric, clou... more High spatial and temporal resolution simulations using the Rotunno and Emanuel axisymmetric, cloud-resolving, hurricane model are found to greatly exceed Emanuel's energetically based upper bound for maximum potential intensity (E-MPI).Using a control simulation similar to that of Rotunno and Emanuel with a sea surface temperature (SST) of 26.13°C, the E-MPI is exceeded after 15 simulation days, after the warming of
We present the results of idealized numerical experiments to examine the difference between tropi... more We present the results of idealized numerical experiments to examine the difference between tropical cyclone evolution in three-dimensional (3-D) and axisymmetric (AX) model configurations. We focus on the prototype problem for intensification, which considers the evolution of an initially unsaturated AX vortex in gradient-wind balance on an f plane. Consistent with findings of previous work, the mature intensity in the 3-D model is reduced relative to that in the AX model. In contrast with previous interpretations invoking barotropic instability and related horizontal mixing processes as a mechanism detrimental to the spin-up process, the results indicate that 3-D eddy processes associated with vortical plume structures can assist the intensification process by contributing to a radial contraction of the maximum tangential velocity and to a vertical extension of tangential winds through the depth of the troposphere. These plumes contribute significantly also to the azimuthally averaged heating rate and the corresponding azimuthal-mean overturning circulation.
The comparisons show that the resolved 3-D eddy momentum fluxes above the boundary layer exhibit counter-gradient characteristics during a key spin-up period, and more generally are not solely diffusive. The effects of these eddies are thus not properly represented by the subgrid-scale parameterizations in the AX configuration. The resolved eddy fluxes act to support the contraction and intensification of the maximum tangential winds. The comparisons indicate fundamental differences between convective organization in the 3- D and AX configurations for meteorologically relevant forecast timescales. While the radial and vertical gradients of the system-scale angular rotation provide a hostile environment for deep convection in the 3-D model, with a corresponding tendency to strain the convective elements in the tangential direction, deep convection in the AX model does not suf- fer this tendency. Also, since during the 3-D intensification process the convection has not yet organized into annular rings, the azimuthally averaged heating rate and radial gra- dient thereof is considerably less than that in the AX model. This lack of organization results broadly in a slower intensifi- cation rate in the 3-D model and leads ultimately to a weaker mature vortex after 12 days of model integration. While az- imuthal mean heating rates in the 3-D model are weaker than those in the AX model, local heating rates in the 3-D model exceed those in the AX model and at times the vortex in the 3-D model intensifies more rapidly than AX. Analyses of the 3-D model output do not support a recent hypothesis concerning the key role of small-scale vertical mixing processes in the upper-tropospheric outflow in controlling the intensification process.
In the 3-D model, surface drag plays a particularly important role in the intensification process for the prototype intensification problem on meteorologically relevant timescales by helping foster the organization of convection in azimuth. There is a radical difference in the behaviour of the 3-D and AX simulations when the surface drag is reduced or increased from realistic values. Borrowing from ideas developed in a recent paper, we give a partial explanation for this difference in behaviour.
Our results provide new qualitative and quantitative insight into the differences between the asymmetric and symmetric dynamics of tropical cyclones and would appear to have important consequences for the formulation of a fluid dynamical theory of tropical cyclone intensification and mature intensity. In particular, the results point to some fundamental limitations of strict axisymmetric theory and modelling for representing the azimuthally averaged behaviour of tropical cyclones in three dimensions.
The purpose of this article is twofold. The first is to point out and correct several misconcepti... more The purpose of this article is twofold. The first is to point out and correct several misconceptions about the putative WISHE mechanism of tropical cyclone intensification that currently are being taught to atmospheric science students, to tropical weather forecasters, and to laypeople who seek to understand how tropical cyclones intensify. The mechanism relates to the simplest problem of an initial cyclonic vortex in a quiescent environment. This first part is important because the credibility of tropical cyclone science depends inter alia on being able to articulate a clear and consistent picture of the hypothesized intensification process and its dependencies on key flow parameters. The credibility depends also on being able to test the hypothesized mechanisms using observations, numerical models, or theoretical analyses. The second purpose of the paper is to carry out new numerical experiments using a state-of-the-art numerical model to test a recent hypothesis invoking the WISHE feedback mechanism during the rapid intensification phase of a tropical cyclone. The results obtained herein, in conjunction with prior work, do not support this recent hypothesis and refute the view that the WISHE intensification mechanism is the essential mechanism of tropical cyclone intensification in the idealized problem that historically has been used to underpin the paradigm. This second objective is important because it presents a simple way of testing the hypothesized intensification mechanism and shows that the mechanism is neither essential nor the dominant mode of intensification for the prototype intensification problem. In view of the operational, societal, and scientific interest in the physics of tropical cyclone intensification, we believe this paper will be of broad interest to the atmospheric science community and the findings should be useful in both the class- room setting and frontier research.
Journal of The Atmospheric Sciences, 2003
High spatial and temporal resolution simulations using the Rotunno and Emanuel axisymmetric, clou... more High spatial and temporal resolution simulations using the Rotunno and Emanuel axisymmetric, cloud-resolving, hurricane model are found to greatly exceed Emanuel's energetically based upper bound for maximum potential intensity (E-MPI).Using a control simulation similar to that of Rotunno and Emanuel with a sea surface temperature (SST) of 26.13°C, the E-MPI is exceeded after 15 simulation days, after the warming of
Journal of Advances in Modeling Earth Systems, 2015
ABSTRACT The purpose of this article is twofold. The first is to point out and correct several mi... more ABSTRACT The purpose of this article is twofold. The first is to point out and correct several misconceptions about the putative WISHE mechanism of tropical cyclone intensification that currently are being taught to atmospheric science students, to tropical weather forecasters, and to laypeople who seek to understand how tropical cyclones intensify in the simplest problem of an initial cyclonic vortex in a quiescent environment. This first part is important because the credibility of tropical cyclone science depends inter alia on being able to articulate a clear and consistent picture of the hypothesized intensification process and its dependencies on key flow parameters; the credibility depends also on being able to test the hypothesized mechanisms using observations, numerical models or theoretical analyses. The second objective of this paper is to carry out new numerical experiments using a state-of-the-art numerical model to test a recent hypothesis invoking the WISHE feedback mechanism during the rapid intensification phase of a tropical cyclone. The results obtained herein, in conjunction with prior work, do not support this recent hypothesis and refute the view that the WISHE intensification mechanism is the essential mechanism of tropical cyclone intensification in the idealized problem that historically has been used to underpin the paradigm. This second objective is important because it presents a simple way of testing the hypothesized intensification mechanism and shows that the mechanism is neither essential nor the dominant mode of intensification for the prototype intensification problem.In view of the operational, societal, and scientific interest in the physics of tropical cyclone intensification, we believe this paper will be of broad interest to the atmospheric science community and the findings should be useful in both the classroom setting and frontier research. This article is protected by copyright. All rights reserved.
Quarterly Journal of the Royal Meteorological Society, 2009
Page 1. QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY QJR Meteorol. Soc. 135: 1697–1714 (... more Page 1. QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY QJR Meteorol. Soc. 135: 1697–1714 (2009) Published online 9 October 2009 in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/qj.459 Do tropical cyclones intensify by WISHE? ...
Quarterly Journal of the Royal Meteorological Society, 2014
ABSTRACT We examine the physical constraints that must be satisfied to allow for a steady-state t... more ABSTRACT We examine the physical constraints that must be satisfied to allow for a steady-state tropical cyclone in an isolated environment, paying particular attention to the need to replenish absolute angular momentum exactly at the rate that it is consumed and to the vanishing of the spin-up function above the frictional boundary layer. We conclude that it is unlikely that these conditions will be met simultaneously and question whether globally steady-state tropical cyclone solutions have merit. The implications for previous studies are discussed.
Monthly Weather Review, 2002
Hurricane Opal (1995) crossed the Gulf of Mexico rapidly intensifying to a 130-kt storm, then for... more Hurricane Opal (1995) crossed the Gulf of Mexico rapidly intensifying to a 130-kt storm, then fortunately weakening before landfall on the Florida panhandle. This intensification was underforecast by the National Hurricane Center. Forecast fields from the 1997 version of the Geophysical Fluid Dynamics Laboratory Hurricane Prediction System (GFDL model) for Hurricane Opal are used to diagnose the rapid intensification of the tropical cyclone. While falling short of the realized peak intensity, the simulation did capture the phase of intensification. This study presents the first step toward diagnosing the mechanisms for intensification within a moderate resolution (ϳ15 km) hydrostatic model and testing the extant hypotheses in the literature.
Journal of the Atmospheric Sciences, 2003
High spatial and temporal resolution simulations using the Rotunno and Emanuel axisymmetric, clou... more High spatial and temporal resolution simulations using the Rotunno and Emanuel axisymmetric, cloud-resolving, hurricane model are found to greatly exceed Emanuel's energetically based upper bound for maximum potential intensity (E-MPI).Using a control simulation similar to that of Rotunno and Emanuel with a sea surface temperature (SST) of 26.13°C, the E-MPI is exceeded after 15 simulation days, after the warming of