scholarly journals Planetary-scale Coherent Structures of Tropical Moist Convection

1998 ◽  
Vol 51 (5) ◽  
pp. 865 ◽  
Author(s):  
Jun-Ichi Yano
Keyword(s):  
Coherent Structures ◽  
Tropical Atmosphere ◽  
Moist Convection ◽  
Initial Attempt ◽  
Planetary Scale ◽  
Characteristic Scales

Two competing pictures for planetary-scale moist convective coherency in the tropical atmosphere exist. The nonlinear turbulent picture emphasises the scaling nature of the system, whereas the traditional picture emphasises the characteristic scales associated with the variability. Some idealised simulations were performed as an initial attempt to reconcile these two competing pictures.

Theory of tropical moist convection

2020 ◽  
pp. 1-45
Author(s):  
David M. Romps
Keyword(s):  
Energy Balance ◽  
Relative Humidity ◽  
Temperature Structure ◽  
Tropical Atmosphere ◽  
Two Dimensional ◽  
Free Troposphere ◽  
Moist Convection ◽  
Real Atmosphere ◽  
Rain Cloud ◽  
Insight Into

These lecture notes cover the theory of tropical moist convection. Many simplifications are made along the way, like neglecting rotation and treating the atmosphere as a two-dimensional fluid or even reducing the atmosphere to two columns. We can gain an immense amount of insight into the real atmosphere by studying these toy models, including answers to the following questions: What is the dominant energy balance in the tropical free troposphere; what sets the temperature structure of the tropical free troposphere; what happens to the pulse of heating deposited into the atmosphere by a rain cloud; why does the tropical atmosphere have the relative-humidity pro le that it does; and what sets the amount of energy available to storms?

scholarly journals Lagrangian coherent structures in tropical cyclone intensification

2012 ◽  
Vol 12 (12) ◽  
pp. 5483-5507 ◽  
Author(s):  
B. Rutherford ◽  
G. Dangelmayr ◽  
M. T. Montgomery
Keyword(s):  
Boundary Layer ◽  
Tropical Cyclone ◽  
Flow Field ◽  
Coherent Structures ◽  
Finite Time ◽  
Potential Temperature ◽  
Three Dimensional ◽  
Lagrangian Coherent Structures ◽  
Moist Convection ◽  
Hyperbolic Structures

Abstract. Recent work has suggested that tropical cyclones intensify via a pathway of rotating deep moist convection in the presence of enhanced fluxes of moisture from the ocean. The rotating deep convective structures possessing enhanced cyclonic vorticity within their cores have been dubbed Vortical Hot Towers (VHTs). In general, the interaction between VHTs and the system-scale vortex, as well as the corresponding evolution of equivalent potential temperature (θe) that modulates the VHT activity, is a complex problem in moist helical turbulence. To better understand the structural aspects of the three-dimensional intensification process, a Lagrangian perspective is explored that focuses on the coherent structures seen in the flow field associated with VHTs and their vortical remnants, as well as the evolution and localized stirring of θe. Recently developed finite-time Lagrangian methods are limited in the three-dimensional turbulence and shear associated with the VHTs. In this paper, new Lagrangian techniques developed for three-dimensional velocity fields are summarized and we apply these techniques to study VHT and θe phenomenology in a high-resolution numerical tropical cyclone simulation. The usefulness of these methods is demonstrated by an analysis of particle trajectories. We find that VHTs create a locally turbulent mixing environment. However, associated with the VHTs are hyperbolic structures that span between adjacent VHTs or adjacent vortical remnants and represent coherent finite-time transport barriers in the flow field. Although the azimuthally-averaged inflow is responsible for the inward advection of boundary layer θe, attracting Lagrangian coherent structures are coincident with pools of high boundary layer θe. Extensions of boundary layer coherent structures grow above the boundary layer during episodes of convection and remain with the convective vortices. These hyperbolic structures form initially as boundaries between VHTs. As vorticity aggregates into a ring-like eyewall feature, the Lagrangian boundaries merge into a ring outside of the region of maximal vorticity.

Rapid Filamentation Zones in Intense Tropical Cyclones

2006 ◽  
Vol 63 (1) ◽  
pp. 325-340 ◽  
Author(s):  
Christopher M. Rozoff ◽  
Wayne H. Schubert ◽  
Brian D. McNoldy ◽  
James P. Kossin
Keyword(s):  
Tropical Cyclone ◽  
Tropical Cyclones ◽  
Coherent Structures ◽  
Deep Convection ◽  
Relative Vorticity ◽  
Moist Convection ◽  
Vortex Interaction ◽  
Tangential Wind ◽  
Stratiform Precipitation ◽  
Deep Moist Convection

Abstract Intense tropical cyclones often possess relatively little convection around their cores. In radar composites, this surrounding region is usually echo-free or contains light stratiform precipitation. While subsidence is typically quite pronounced in this region, it is not the only mechanism suppressing convection. Another possible mechanism leading to weak-echo moats is presented in this paper. The basic idea is that the strain-dominated flow surrounding an intense vortex core creates an unfavorable environment for sustained deep, moist convection. Strain-dominated regions of a tropical cyclone can be distinguished from rotation-dominated regions by the sign of S21 + S22 − ζ2, where S1 = ux − υy and S2 = υx + uy are the rates of strain and ζ = υx − uy is the relative vorticity. Within the radius of maximum tangential wind, the flow tends to be rotation-dominated (ζ2 > S21 + S22), so that coherent structures, such as mesovortices, can survive for long periods of time. Outside the radius of maximum tangential wind, the flow tends to be strain-dominated (S21 + S22 > ζ2), resulting in filaments of anomalous vorticity. In the regions of strain-dominated flow the filamentation time is defined as τfil = 2(S21 + S22 − ζ2)−1/2. In a tropical cyclone, an approximately 30-km-wide annular region can exist just outside the radius of maximum tangential wind, where τfil is less than 30 min and even as small as 5 min. This region is defined as the rapid filamentation zone. Since the time scale for deep moist convective overturning is approximately 30 min, deep convection can be significantly distorted and even suppressed in the rapid filamentation zone. A nondivergent barotropic model illustrates the effects of rapid filamentation zones in category 1–5 hurricanes and demonstrates the evolution of such zones during binary vortex interaction and mesovortex formation from a thin annular ring of enhanced vorticity.

From storms to planetary-scale disturbances in the atmospheres of Jupiter and Saturn

2020 ◽  
Author(s):  
Agustín Snchez-Lavega
Keyword(s):  
Bright Spot ◽  
Moist Convection ◽  
Jet Streams ◽  
Linear Interaction ◽  
Spatial And Temporal Scales ◽  
Wind Speeds ◽  
Planetary Scale ◽  
The North ◽  
Wide Range ◽  
Cloud Tops

<p>The deep atmospheres of the giant planets Jupiter and Saturn are covered by different layers of clouds and hazes where a rich variety of dynamical phenomena take place. At the cloud tops, the winds blow along latitude circles forming a system of jet streams that alternate in East-West direction with latitude. The upper clouds are organised in parallel bands (the low reflectivity belts and the white zones) whose structure follows the winds and correlate with the temperature field over a range of altitudes.</p><p>In this zonal system of jets and bands, meteorological formations grow and evolve over a wide range of spatial and temporal scales, among others, vortices, waves, storms and chaotic and turbulent features. The most spectacular of all of them are those in which the outbreak of a small bright spot that growths and expands rapidly up to a size in the range of 5,000 - 10,000 km, produces a strong interaction with the winds generating a planetary scale disturbance that propagates zonally according to prevailing winds. Jupiter events begin at localized latitudes in the South Equatorial Belt at 16º South, where wind speeds are close to zero, and in the North Temperate Belt at 23º North where the winds have the velocity record on the planet with a jet peak reaching about 180 m/s. The disturbance produces cyclically a change in the albedo of the band, from a zone to a belt, with periods in the range 5-10 years. On Saturn, the phenomenon is known as the Great White Spot (GWS) and has been observed at different latitudes, from the Equator to near the pole, but always in the northern hemisphere. The GWS has been recorded only six times in the history of observations of the planet with a periodicity close to 30 years (about one Saturn year). The proposed models to explain these phenomena involve the trigger of an initial storm produced by moist convection at the water clouds located below the visible clouds. The associated vigorous upward motions generate massive cumulus-like clouds and their non-linear interaction with the wind system forms the series of vortices and waves that make-up the disturbance that propagates away from the active source until fully encircling the planet.</p>

Shallow Meridional Circulations in the Tropical Atmosphere

2008 ◽  
Vol 21 (14) ◽  
pp. 3453-3470 ◽  
Author(s):  
Chidong Zhang ◽  
David S. Nolan ◽  
Christopher D. Thorncroft ◽  
Hanh Nguyen
Keyword(s):  
Large Scale ◽  
Meridional Circulation ◽  
Indian Subcontinent ◽  
Meridional Flow ◽  
Trade Wind ◽  
Seasonal Cycles ◽  
Tropical Atmosphere ◽  
Moist Convection ◽  
Meridional Overturning ◽  
Deep Moist Convection

Abstract A shallow meridional circulation (SMC) in the tropical atmosphere features a low-level (e.g., 700 hPa) flow that is in the opposite direction to the boundary layer monsoon or trade wind flow and is distinct from the meridional flow above. Representations of the SMC in three global reanalyses show both similarities and astonishing discrepancies. While the SMC over West Africa appears to be the strongest, it also exists over the eastern Atlantic and eastern Pacific Oceans, and over the Indian subcontinent, with different strength and structure. All SMCs undergo marked seasonal cycles. The SMCs are summarized into two types: one associated with the marine ITCZ and the other with the summer monsoon. The large-scale conditions for these two types of SMCs are similar: a strong meridional gradient in surface pressure linked to surface temperature distributions and an absence of deep moist convection. The processes responsible for these conditions are different for the two types of SMCs, as are their structures relative to moist convection, associated precipitation, and deep meridional overturning circulations. It is suggested that discrepancies among the representations of the SMC in the three global reanalyses stem from different treatment of physical parameterizations, especially for cumulus convection, in the models used for the data assimilation.

scholarly journals Is the Tropical Atmosphere in Convective Quasi-Equilibrium?

2015 ◽  
Vol 28 (11) ◽  
pp. 4357-4372 ◽  
Author(s):  
Jia-Lin Lin ◽  
Taotao Qian ◽  
Toshiaki Shinoda ◽  
Shuanglin Li
Keyword(s):  
Boundary Layer ◽  
Global Climate Models ◽  
Quasi Equilibrium ◽  
Tropical Atmosphere ◽  
Tropospheric Temperature ◽  
Moist Convection ◽  
Moist Static Energy ◽  
Shallow Convection ◽  
Upper Troposphere ◽  
Static Energy

Abstract The hypothesis of convective quasi-equilibrium (CQE) has dominated thinking about the interaction between deep moist convection and the environment for at least two decades. In this view, deep convection develops or decays almost instantly to remove any changes of convective instability, making the tropospheric temperature always tied to the boundary layer moist static energy. The present study examines the validity of the CQE hypothesis at different vertical levels using long-term sounding data from tropical convection centers. The results show that the tropical atmosphere is far from the CQE with much weaker warming in the middle and upper troposphere associated with the increase of boundary layer moist static energy. This is true for all the time scales resolved by the observational data, ranging from hourly to interannual and decadal variability. It is possibly caused by the ubiquitous existence of shallow convection and stratiform precipitation, both leading to sign reversal of heating from lower to upper troposphere. The simulations by 42 global climate models from phases 3 and 5 of the Coupled Model Intercomparsion Project (CMIP3 and CMIP5) are also analyzed and compared with the observations.

Simulations of convective storms in Jupiter with an updated version of a three-dimensional model of moist convection

2020 ◽  
Author(s):  
Peio Iñurrigarro ◽  
Ricardo Hueso ◽  
Agustin Sánchez-Lavega
Keyword(s):  
Large Scale ◽  
Vertical Structure ◽  
Three Dimensional ◽  
Giant Planets ◽  
Moist Convection ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Geophysical Research ◽  
Convective Storms ◽  
Planetary Scale

<p>Moist convective storms powered by the release of latent heat in rising air parcels are a key element of the meteorology of the Gas Giants [1] and are suspected to play also an important role in the atmospheric dynamics of the Ice Giants [2]. In Jupiter convective storms of different spatial scales occur with different frequencies, from short-lived localized storms [3] to longer-lived storms able to trigger planetary-scale disturbances that develop in cycles of several years [4].</p> <p>Several models with different approaches have been developed to study moist convection in Jupiter and other planets [5-8]. Three-dimensional cloud resolving models are computationally expensive but have the advantage of allowing the study of the motions generated in the storm and they can also take into account the effects of the three-dimensional Coriolis force in the evolution of the storm. We have used an updated version of a three-dimensional Anelastic Model of Moist Convection [9-11] to explore the development of convective storms in Jupiter. We have improved the dynamical core of the model increasing the stability of the model, which allows us to simulate the dynamics of the development of the storms for longer time ranges than previous simulations presented with this model.</p> <p>Here we will present results of new simulations of moist convective storms in Jupiter. We simulated the onset and initial development of the storms in a series of different scenarios of condensables abundances to study under which conditions it is possible to trigger convective storms. We tested different abundances of the condensables, relative humidities and fractions of condensates carried by the storm. We play particular attention to the capacity of the storm to generate convective downdrafts with the potential to desiccate the volatiles of the upper atmosphere [12, 13].</p> <p> </p> <p><strong>References:</strong></p> <p>[1] A. P. Ingersoll et al. Moist convection as an energy source for the large-scale motions in Jupiter’s atmosphere, Nature 403, 2000.</p> <p>[2] R. Hueso and A. Sánchez-Lavega. Atmospheric Dynamics and Vertical Structure of Uranus and Neptune's weather layers, Space Science Reviews, 215:52, 2019.</p> <p>[3] P. Iñurrigarro et al. Observations and numerical modelling of a convective disturbance in a large-scale cyclone in Jupiter’s South Temperate Belt, Icarus 336, 2020.</p> <p>[4] A. Sánchez-Lavega et al. Depth of a strong jovian jet from a planetary-scale disturbance driven by storms, Nature 451, 2008.</p> <p>[5] C. R. Stoker. Moist Convection: A Mechanism for Producing the Vertical Structure of the Jovian Equatorial Plumes, Icarus 67, 1985.</p> <p>[6] Y. Yair et al. Model interpretation of Jovian lightning activity and the Galileo Probe results, Journal of Geophysical Research 103, 1998.</p> <p>[7] K. Sugiyama et al. Numerical simulations of Jupiter’s moist convection layer: Structure and dynamics in statistically steady states, Icarus 229, 2014.</p> <p>[8] C. Li and X. Chen. Simulating Nonhydrostatic Atmospheres on Planets (SNAP): Formulation, Validation and Application to the Jovian Atmosphere, The Astrophysical Supplement Series 240, 2019.</p> <p>[9] R. Hueso and A. Sánchez-Lavega. A Three-Dimensional Model of Moist Convection for the Giant Planets: The Jupiter Case, Icarus 151, 2001.</p> <p>[10] R. Hueso and A. Sánchez-Lavega. A three-dimensional model of moist convection for the giant planets II: Saturn’s water and ammonia moist convective storms, Icarus 172, 2004.</p> <p>[11] R. Hueso and A. Sánchez-Lavega. Methane storms on Saturn’s moon Titan, Nature 442, 2006.</p> <p>[12] T. Guillot et al. Storms and the Depletion of Ammonia in Jupiter: I. Microphysics of “Mushballs”, Journal of Geophysical Research, in press, 2020.</p> <p>[13] T. Guillot et al. Storms and the Depletion of Ammonia in Jupiter: II. Explaining the Juno observations, Journal of Geophysical Research, in press, 2020.</p>

scholarly journals Lagrangian coherent structures in tropical cyclone intensification

2011 ◽  
Vol 11 (10) ◽  
pp. 28125-28168 ◽  
Author(s):  
B. Rutherford ◽  
G. Dangelmayr ◽  
M. T. Montgomery
Keyword(s):  
Boundary Layer ◽  
Coherent Structures ◽  
Potential Temperature ◽  
Three Dimensional ◽  
Complex Problem ◽  
Lagrangian Coherent Structures ◽  
Moist Convection ◽  
Hyperbolic Structures ◽  
Convective Structures ◽  
Deep Moist Convection

Abstract. Recent work has suggested that tropical cyclones intensify via a pathway of rotating deep moist convection in the presence of enhanced fluxes of moisture from the ocean. The rotating deep convective structures possessing enhanced cyclonic vorticity within their cores have been dubbed Vortical Hot Towers (VHTs). In general, the interaction between VHTs and the system-scale vortex, as well as the corresponding evolution of equivalent potential temperature θe that modulates the VHT activity, is a complex problem in moist helical turbulence. To better understand the structural aspects of the three-dimensional intensification process, a Lagrangian perspective is explored that focuses on the localized stirring around VHTs and their vortical remnants, as well as the evolution and stirring of θe. Recently developed finite-time Lagrangian methods are limited in the three-dimensional turbulence and shear associated with the VHTs. In this paper, new Lagrangian techniques developed for three-dimensional velocity fields are summarized and we apply these techniques to study VHT and θe phenomenology. Our primary findings are that VHTs are coherent Lagrangian vortices that create a turbulent mixing environment. Associated with the VHTs are hyperbolic structures that modulate the aggregation of VHTs and their vortical remnants. Although the azimuthally-averaged inflow is responsible for the inward advection of boundary layer θe, the Lagrangian coherent structures are found to modulate the convection emanating from the boundary layer by stirring θe along organized attracting boundaries. Extensions of boundary layer coherent structures grow above the boundary layer during episodes of convection are responsible for organizing the remnants of the convective vortices. These hyperbolic structures form initially as boundaries between VHTs, but persist above the boundary layer and outlive the VHTs to eventually form the primary eyewall as the vortex attains maturity.

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