Simple kinematic models for the environmental interaction of tropical cyclones in vertical wind shear

Riemer, Michael; Montgomery, Michael T.

doi:10.5194/acp-11-9395-2011

Cited by 87 publications

(72 citation statements)

References 38 publications

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“…Besides the obvious importance of the shear magnitude, such factors include the vertical profiles of environmental wind speed and direction (Zeng et al, 2010;Wang, 2012), and the environmental moisture and temperature profiles (cf. discussion in Riemer and Montgomery (2011)). Careful examination of the importance of these environmental profiles is beyond the scope of this study but constitutes an important topic for future research 5 .…”

Section: Purpose Of Additional Experimentsmentioning

confidence: 99%

“…On account of the swirling winds, the updrafts within the SBC rise along a helical path. A simple kinematic model (Riemer and Montgomery, 2011) suggests that, at low levels above the inflow layer, environmental low-θ e air approaches the storm closely underneath the helical updrafts in the downshear and downshear-left quadrants 2 . Evaporative cooling of precipitation falling out of the SBC, and into this unsaturated air, most likely drives the strong and persistent, vortex-scale downdrafts that cool and dry the TC's inflow layer.…”

Section: Riemer Et Al: Thermodynamic Impact Of Vertical Wind Sheamentioning

confidence: 99%

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Further examination of the thermodynamic modification of the inflow layer of tropical cyclones by vertical wind shear

2013

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Abstract. Recent work has developed a new framework for the impact of vertical wind shear on the intensity evolution of tropical cyclones. A focus of this framework is on the frustration of the tropical cyclone's power machine by shearinduced, persistent downdrafts that flush relatively cool and dry (lower equivalent potential temperature, θ e ) air into the storm's inflow layer. These previous results have been based on idealised numerical experiments for which we have deliberately chosen a simple set of physical parameterisations. Before efforts are undertaken to test the proposed framework with real atmospheric data, we assess here the robustness of our previous results in a more realistic and representative experimental setup by surveying and diagnosing five additional numerical experiments. The modifications of the experimental setup comprise the values of the exchange coefficients of surface heat and momentum fluxes, the inclusion of experiments with ice microphysics, and the consideration of weaker, but still mature tropical cyclones.In all experiments, the depression of the inflow layer θ e values is significant and all tropical cyclones exhibit the same general structural changes when interacting with the imposed vertical wind shear. Tropical cyclones in which strong downdrafts occur more frequently exhibit a more pronounced depression of inflow layer θ e outside of the eyewall in our experiments. The magnitude of the θ e depression underneath the eyewall early after shear is imposed in our experiments correlates well with the magnitude of the ensuing weakening of the respective tropical cyclone. Based on the evidence presented, it is concluded that the newly proposed framework is a robust description of intensity modification in our suite of experiments.

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Section: Purpose Of Additional Experimentsmentioning

confidence: 99%

Section: Riemer Et Al: Thermodynamic Impact Of Vertical Wind Sheamentioning

confidence: 99%

Further examination of the thermodynamic modification of the inflow layer of tropical cyclones by vertical wind shear

2013

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“…Since the particles originate from a region with low relative humidity, the streamlines underestimate the amount of dry air entering the pouch. The differences in translation speed tend to have less effect on the geometry of strong vortices (Riemer and Montgomery , 2011). Since the Lagrangian frame does not require a translation speed, it is not sensitive to variations in translation speed.…”

Section: Repelling Materials Linementioning

confidence: 99%

“…While the trajectories for Gaston traveled the longest distances outside the pouch center, the trajectories for Karl that recirculated in the pouch center had the longest paths, Figure 11 over the four day period of time before exhibiting a persistent region of central dense overcast on the day of development of an organized circulation center, 14 September (Montgomery et al 2011). Karl intensified to a strong tropical storm on 15 September, and into a hurricane on 16 September, becoming a category 3 storm on 17 September, shortly before landfall in Veracruz, Mexico.…”

Section: Trajectory Analysismentioning

confidence: 99%

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

Rutherford

Montgomery

2012

Atmos. Chem. Phys.

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Abstract. The problem of tropical cyclone formation requires among other things an improved understanding of recirculating flow regions on sub-synoptic scales in a time evolving flow with typically sparse real-time data. This recirculation problem has previously been approached assuming as a first approximation both a layer-wise two-dimensional and nearly steady flow in a co-moving frame with the parent tropical wave or disturbance. This paper provides an introduction of Lagrangian techniques for locating flow boundaries that encompass regions of recirculation in timedependent flows that relax the steady flow approximation.Lagrangian methods detect recirculating regions from time-dependent data and offer a more complete methodology than the approximate steady framework. The Lagrangian reference frame follows particle trajectories so that flow boundaries which constrain particle transport can be viewed in a frame-independent setting. Finite-time Lagrangian scalar field methods from dynamical systems theory offer a way to compute boundaries from grids of particles seeded in and near a disturbance.The methods are applied to both a developing and nondeveloping disturbance observed during the recent predepression investigation of cloud systems in the tropics (PREDICT) experiment. The data for this analysis is derived from global forecast model output that assimilated the dropsonde observations as they were being collected by research aircraft. Since Lagrangian methods require trajectory integrations, we address some practical issues of using Lagrangian methods in the tropical cyclogenesis problem. Lagrangian diagnostics are used to evaluate the previously hypothesized import of dry air into ex-Gaston, which did not re-develop into a tropical cyclone, and the exclusion of dry air from pre-Karl, which did become a tropical cyclone and later a major hurricane.

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Environmental control of tropical cyclones in CMIP5: A ventilation perspective

Tang

Camargo

2014

J Adv Model Earth Syst

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The ventilation index serves as a theoretically based metric to assess possible changes in the statistics of tropical cyclones to combined changes in vertical wind shear, midlevel entropy deficit, and potential intensity in climate models. Model output from eight Coupled Model Intercomparison Project 5 models is used to calculate the ventilation index. The ventilation index and its relationship to tropical cyclone activity between two 20 year periods are compared: the historical experiment from 1981 to 2000 and the RCP8.5 experiment from 2081 to 2100. The general tendency is for an increase in the seasonal ventilation index in the majority of the tropical cyclone basins, with exception of the North Indian basin. All the models project an increase in the midlevel entropy deficit in the tropics, although the effects of this increase on the ventilation index itself are tempered by a compensating increase in the potential intensity and a decrease in the vertical wind shear in most tropical cyclone basins. The nonlinear combination of the terms in the ventilation index results in large regional and intermodel variability. Basin changes in the ventilation index are well correlated with changes in the frequency of tropical cyclone formation and rapid intensification in the climate models. However, there is large uncertainty in the projections of the ventilation index and the corresponding effects on changes in the statistics of tropical cyclone activity.

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Simple kinematic models for the environmental interaction of tropical cyclones in vertical wind shear

Cited by 87 publications

References 38 publications

Further examination of the thermodynamic modification of the inflow layer of tropical cyclones by vertical wind shear

Further examination of the thermodynamic modification of the inflow layer of tropical cyclones by vertical wind shear

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

Environmental control of tropical cyclones in CMIP5: A ventilation perspective

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