scholarly journals Constraints from Invariant Subtropical Vertical Velocities on the Scalings of Hadley Cell Strength and Downdraft Width with Rotation Rate

2021 ◽  
Vol 78 (5) ◽  
pp. 1445-1463
Author(s):  
Jonathan L. Mitchell ◽  
Spencer A. Hill
Keyword(s):  
Heat Flux ◽  
Vertical Velocity ◽  
Rotation Rate ◽  
Diabatic Heating ◽  
Static Stability ◽  
Hadley Cell ◽  
Rossby Number ◽  
Eddy Heat Flux ◽  
Planetary Rotation ◽  
Wide Range

AbstractWeak-temperature-gradient influences from the tropics and quasigeostrophic influences from the extratropics plausibly constrain the subtropical-mean static stability in terrestrial atmospheres. Because mean descent acting on this static stability is a leading-order term in the thermodynamic balance, a state-invariant static stability would impose constraints on the Hadley cells, which this paper explores in simulations of varying planetary rotation rate. If downdraft-averaged effective heating (the sum of diabatic heating and eddy heat flux convergence) too is invariant, so must be vertical velocity—an “omega governor.” In that case, the Hadley circulation overturning strength and downdraft width must scale identically—the cell can strengthen only by widening or weaken only by narrowing. Semiempirical scalings demonstrate that subtropical eddy heat flux convergence weakens with rotation rate (scales positively) while diabatic heating strengthens (scales negatively), compensating one another if they are of similar magnitude. Simulations in two idealized, dry GCMs with a wide range of planetary rotation rates exhibit nearly unchanging downdraft-averaged static stability, effective heating, and vertical velocity, as well as nearly identical scalings of the Hadley cell downdraft width and strength. In one, eddy stresses set this scaling directly (the Rossby number remains small); in the other, eddy stress and bulk Rossby number changes compensate to yield the same, ~Ω−1/3 scaling. The consistency of this power law for cell width and strength variations may indicate a common driver, and we speculate that Ekman pumping could be the mechanism responsible for this behavior. Diabatic heating in an idealized aquaplanet GCM is an order of magnitude larger than in dry GCMs and reanalyses, and while the subtropical static stability is insensitive to rotation rate, the effective heating and vertical velocity are not.

scholarly journals Solsticial Hadley Cell ascending edge theory from supercriticality

2021 ◽  
Author(s):  
Spencer A. Hill ◽  
Simona Bordoni ◽  
Jonathan L. Mitchell
Keyword(s):  
Large Scale ◽  
Analytical Approximation ◽  
Hadley Cell ◽  
Rossby Number ◽  
Absolute Vorticity ◽  
Rotation Rates ◽  
Planetary Rotation ◽  
Wide Range ◽  
Summer Hemisphere ◽  
Earth’S Climate

AbstractHow far the Hadley circulation’s ascending branch extends into the summer hemisphere is a fundamental but incompletely understood characteristic of Earth’s climate. Here, we present a predictive, analytical theory for this ascending edge latitude based on the extent of supercritical forcing. Supercriticality sets the minimum extent of a large-scale circulation based on the angular momentum and absolute vorticity distributions of the hypothetical state were the circulation absent. We explicitly simulate this latitude-by-latitude radiative-convective equilibrium (RCE) state. Its depth-averaged temperature profile is suitably captured by a simple analytical approximation that increases linearly with sinφ, where φ is latitude, from the winter to the summer pole. This, in turn, yields a one-third power-law scaling of the supercritical forcing extent with the thermal Rossby number. In moist and dry idealized GCM simulations under solsticial forcing performed with a wide range of planetary rotation rates, the ascending edge latitudes largely behave according to this scaling.

The Position of the Midlatitude Storm Track and Eddy-Driven Westerlies in Aquaplanet AGCMs

2010 ◽  
Vol 67 (12) ◽  
pp. 3984-4000 ◽  
Author(s):  
Jian Lu ◽  
Gang Chen ◽  
Dargan M. W. Frierson
Keyword(s):  
Global Warming ◽  
Coming Out ◽  
Storm Track ◽  
Lower Troposphere ◽  
Static Stability ◽  
Hadley Cell ◽  
Eddy Heat Flux ◽  
Circulation Regime ◽  
Wide Range ◽  
Single Jet

Abstract The sensitivity of the midlatitude storm track and eddy-driven wind to the sea surface temperature (SST) boundary forcing is studied over a wide range of perturbations using both simple and comprehensive general circulation models over aquaplanet lower boundary conditions. Under the single-jet circulation regime similar to the conditions of the present climate in the Northern Hemisphere winter or the Southern Hemisphere summer, the eddy-driven jet shifts monotonically poleward with both the global mean and the equator-to-pole gradient of the SST. The eddy-driven jet can have a reverse relationship to the gradient if it is well separated from the subtropical jet and Hadley cell boundary in a double-jet circulation regime. A simple scaling is put forward to interpret the simulated sensitivity of the storm-track/eddy-driven westerly wind position within the single-jet regime in both models. The rationale for the scaling is based on the notion that the wave activity flux can propagate horizontally away from the source region, resulting in a broader distribution of eddy potential vorticity (PV) flux in the upper troposphere than that of the flux in the opposite direction in the lower troposphere. As a consequence, the position of the maximum of the eddy-driven westerlies tends to be controlled by the profile of the relatively sharp-peaked low-level PV flux, which is dominated by the eddy heat flux component of the Eliassen–Palm (EP) flux. Thus, the position of the eddy-driven surface westerlies may be inferred from the vertical EP flux coming out of the lower troposphere. The vertical EP flux can be parameterized by a measure of baroclinicity, whose latitudinal variations show a linear relationship with the meridional displacement of the eddy-driven westerlies and the storm track. This relationship still holds well within the single-jet regime, even when only the variation of static stability is taken into consideration in estimating the baroclinicity (the temperature gradient component of which is fixed). To the extent that the static stability is deterministically constrained by and hence can be predicted from the given SST conditions through a moist scaling for the midlatitude stratification, one may, given SST perturbations, predict which way the storm track and eddy-driven wind should shift with respect to a chosen reference climate state. The resultant anomaly-wise scaling turns out to be valid for both the idealized and comprehensive models, regardless of the details in the model physics. By corollary, it can be argued that the poleward shift of storm track found in the global warming simulations by fully coupled climate models may be attributed, at least partially, to the increase in the subtropical and midlatitude static stability with global warming.

The role of diabatic heating in Ferrel cell dynamics

2021 ◽  
Author(s):  
Orli Lachmy ◽  
Yohai Kaspi
Keyword(s):  
Heat Flux ◽  
Heating Rate ◽  
Diabatic Heating ◽  
Heat Budget ◽  
Reanalysis Data ◽  
Cell Dynamics ◽  
Data Set ◽  
Eddy Heat Flux ◽  
Ferrel Cell ◽  
Meridional Winds

<p>The Ferrel cell consists of the zonal mean vertical and meridional winds in the midlatitudes. The continuity of the Ferrel circulation and the zonal mean momentum and heat budgets imply a collocation of the eddy-driven jet and poleward eddy heat flux maxima, under certain assumptions, including the negligibility of diabatic heating. The latter assumption is questioned, since midlatitude storms are associated with latent heating in the midtroposphere. In this study, the heat budget of the Ferrel cell in both hemispheres is examined, using the JRA55 reanalysis data set. The diabatic heating rate is significant close to the center of the Ferrel cell during winter and at the ascending branch during summer in both hemispheres. The interannual variability shows a positive correlation between the diabatic heating rate in the midlatitude midtroposphere and the latitudinal separation between the eddy heat flux and the eddy-driven jet maxima during winter in both hemispheres.</p>

Towards an Understanding of the Structure of Jupiter’s Atmosphere using the Ammonia Distribution and the Transformed Eulerian Mean Theory

2021 ◽  
Author(s):  
Sukyoung Lee ◽  
Yohai Kaspi
Keyword(s):  
Vertical Velocity ◽  
Static Stability ◽  
Hadley Cell ◽  
Lapse Rate ◽  
Scaling Analysis ◽  
Overturning Circulation ◽  
Temperature Lapse Rate ◽  
Ferrel Cell ◽  
The Tropics ◽  
Transformed Eulerian Mean

AbstractThe structure and stability of Jupiter’s atmosphere is analyzed using transformed Eulerian mean (TEM) theory. Utilizing the ammonia distribution derived from microwave radiometer measurements of the Juno orbiter, the latitudinal and vertical distribution of the vertical velocity in the interior of Jupiter’s atmosphere is inferred. The resulting overturning circulation is then interpreted in the TEM framework to offer speculation of the vertical and meridional temperature distribution. In the extratropics, the analyzed vertical velocity field shows Ferrel-cell-like patterns associated with each of the jets. A scaling analysis of the TEM overturning circulation equation suggests that in order for the Ferrel-cell-like patterns to be visible in the ammonia distribution, the static stability of Jupiter’s weather layer should be on the order of 1 × 10−2 s−1. In the tropics, the ammonia distribution suggests strong upward motion which is reminiscent of the rising branch of the Hadley cell where the static stability is weaker. Taken together, the analysis suggests that the temperature lapse rate in the extratropics is markedly greater than that in the tropics. Because the cloud top temperature is nearly uniform across all latitudes, the analysis suggests that in the interior of the weather layer, there could exist a temperature gradient between the tropical and extratropical regions.

scholarly journals The Effect of Eddy–Eddy Interactions on Jet Formation and Macroturbulent Scales

2016 ◽  
Vol 73 (5) ◽  
pp. 2049-2059 ◽  
Author(s):  
Rei Chemke ◽  
Yohai Kaspi
Keyword(s):  
High Resolution ◽  
Kinetic Energy ◽  
Rotation Rate ◽  
Mean Flow ◽  
Jet Formation ◽  
Zonal Scale ◽  
Zonal Jets ◽  
Planetary Rotation ◽  
Wide Range ◽  
Flow Interactions

Abstract The effect of eddy–eddy interactions on zonal and meridional macroturbulent scales is investigated over a wide range of eddy scales, using high-resolution idealized GCM simulations with and without eddy–eddy interactions. The wide range of eddy scales is achieved through systematic variation of the planetary rotation rate and thus multiple-jet planets. It is found that not only are eddy–eddy interactions not essential for the formation of jets, but the existence of eddy–eddy interactions decreases the number of eddy-driven jets in the atmosphere. The eddy–eddy interactions have little effect on the jet scale, which in both types of simulations coincides with the Rhines scale through all latitudes. The decrease in the number of jets in the presence of eddy–eddy interactions occurs because of the narrowing of the latitudinal region where zonal jets appear. This narrowing occurs because eddy–eddy interactions are mostly important at latitudes poleward of where the Rhines scale is equal to the Rossby deformation radius. Thus, once eddy–eddy interactions are removed, the conversion from baroclinic to barotropic eddy kinetic energy increases, and eddy–mean flow interactions intrude into these latitudes and maintain additional jets there. The eddy–eddy interactions are found to increase the energy-containing zonal scale so it coincides with the jets’ scale and thus make the flow more isotropic. While the conversion scale coincides with the most unstable scale, the Rossby deformation radius does not provide a good indication to these scales in both types of simulations.

scholarly journals Verification of an Approximate Thermodynamic Equation with Application to Study on Arctic Stratospheric Temperature Changes

2018 ◽  
Vol 76 (1) ◽  
pp. 3-9
Author(s):  
Renqiang Liu ◽  
Yanyan Fu
Keyword(s):  
Heat Flux ◽  
Diabatic Heating ◽  
Radiative Heating ◽  
The Arctic ◽  
Temperature Changes ◽  
Stratospheric Temperature ◽  
Eddy Heat Flux ◽  
Temperature Increment ◽  
Flux Approximation ◽  
Arctic Temperature

Abstract Temperature changes in the Arctic lower stratosphere on both short- and long-term time scales are critical for changing the magnitude of ozone losses in the Arctic vortex. In this paper, an approximate month-to-month temperature change equation is constructed and extended to a new form for decade-to-decade changes. Then we provide a verification of these equations and show an example of an application for partitioning between the dynamical and radiative contributions to the Arctic lower-stratospheric temperature decadal changes, as well as the trends, using the European Centre for Medium-Range Weather Forecasts (ECMWF) interim reanalysis (ERA-Interim) data during the period of 1980–99. At 100 hPa, the month-to-month Arctic temperature increment is a small term compared to the dynamical heating and diabatic heating, which are largely canceling terms with maximum magnitudes in November–April and October–March, respectively. However, it is not the case for their decadal changes and the decadal change of the Arctic current-month temperature compared to those of the regressed dynamical heating and radiative heating, where the current-month decadal changes and the corresponding trends are approached except in March and a rough agreement exists between these trends and those reported in other studies. The dynamical plus diabatic heating term and the temperature increment, as well as their decadal changes, are roughly balanced during the annual oscillation. However, some departures exist in both cases because of the large deviations or uncertainties of relevant terms and also probably due to the quasigeostrophic approximation and the eddy heat flux approximation of the dynamical heating, and a restricted condition of the eddy heat flux approximation is given at the end.

scholarly journals Limits on the Extent of the Solsticial Hadley Cell: The Role of Planetary Rotation

2019 ◽  
Vol 76 (7) ◽  
pp. 1989-2004 ◽  
Author(s):  
Martin S. Singh
Keyword(s):  
Rotation Rate ◽  
Seasonal Cycle ◽  
General Circulation ◽  
Circulation Model ◽  
Hadley Cell ◽  
Quasi Equilibrium ◽  
Rotation Rates ◽  
Planetary Rotation ◽  
Summer Hemisphere

Abstract The role of planetary rotation in limiting the extent of the cross-equatorial solsticial Hadley cell (SHC) is investigated using idealized simulations with an aquaplanet general circulation model run under perpetual-solstice conditions. Consistent with previous studies that include a seasonal cycle, the SHC extent increases with decreasing rotation rate, and it occupies the entire globe for sufficiently low planetary rotation rates. A simple theory for the summer-hemisphere extent of the SHC is constructed in which it is assumed that the SHC occupies regions for which a hypothetical radiative–convective equilibrium state is physically unattainable. The theory predicts that the SHC extends farther into the summer hemisphere as the rotation rate is decreased, qualitatively reproducing the behavior of the simulations, but it generally underestimates the simulated SHC extent. A diagnostic theory for the summer-hemisphere SHC extent is then developed based on the assumptions of slantwise convective neutrality and conservation of angular momentum within the Hadley cell. The theory relates the structure of the SHC in the summer hemisphere to the distribution of boundary layer entropy in the dynamically equilibrated simulations. The resultant diagnostic for the SHC extent generalizes the convective quasi-equilibrium-based constraint of Privé and Plumb, in which the position of rain belts is related to maxima in the low-level entropy distribution.

scholarly journals Zonal-Mean Atmospheric Dynamics of Slowly Rotating Terrestrial Planets

2019 ◽  
Vol 76 (5) ◽  
pp. 1397-1418
Author(s):  
G. J. Colyer ◽  
G. K. Vallis
Keyword(s):  
Numerical Simulations ◽  
Zonal Wind ◽  
Rotation Rate ◽  
Potential Temperature ◽  
Terrestrial Planet ◽  
Zonal Flow ◽  
Hadley Cell ◽  
Overturning Circulation ◽  
Eddy Motion ◽  
Planetary Rotation

Abstract The zonal-mean atmospheric flow of an idealized terrestrial planet is investigated using both numerical simulations and zonally symmetric theories, focusing largely on the limit of low planetary rotation rate. Two versions of a zonally symmetric theory are considered, the standard Held–Hou model, which features a discontinuous zonal wind at the edge of the Hadley cell, and a variant with continuous zonal wind but discontinuous temperature. The two models have different scalings for the boundary latitude and zonal wind. Numerical simulations are found to have smoother temperature profiles than either model, with no temperature or velocity discontinuities even in zonally symmetric simulations. Continuity is achieved in part by the presence of an overturning circulation poleward of the point of maximum zonal wind, which allows the zonal velocity profile to be smoother than the original theory without the temperature discontinuities of the variant theory. Zonally symmetric simulations generally fall between the two sets of theoretical scalings, and have a faster polar zonal flow than either set. Three-dimensional simulations, which allow for the eddy motion that is missing from both models, fall closer to the scalings of the variant model. At very low rotation rates the maximum zonal wind falls with falling planetary rotation rate, and is zero at zero rotation. The low-rotation limit of the overturning circulation, however, is strong enough to drive the temperature profile close to a state of nearly constant potential temperature.

Radiative and Dynamic Controls on Atmospheric Heat Transport over Different Planetary Rotation Rates

2021 ◽  
Vol 34 (9) ◽  
pp. 3543-3554
Author(s):  
Tyler Cox ◽  
Kyle C. Armour ◽  
Gerard H. Roe ◽  
Aaron Donohoe ◽  
Dargan M. W. Frierson
Keyword(s):  
Heat Transport ◽  
Rotation Rate ◽  
Hadley Cell ◽  
Slow Rotation ◽  
Rotation Rates ◽  
Planetary Rotation ◽  
Atmospheric Heat Transport ◽  
Mean Meridional Circulation ◽  
Radiative Temperature ◽  
Atmospheric Heat

AbstractAtmospheric heat transport is an important piece of our climate system, yet we lack a complete theory for its magnitude or changes. Atmospheric dynamics and radiation play different roles in controlling the total atmospheric heat transport (AHT) and its partitioning into components associated with eddies and mean meridional circulations. This work focuses on two specific controls: a radiative one, namely atmospheric radiative temperature tendencies, and a dynamic one, the planetary rotation rate. We use an idealized gray radiation model to employ a novel framework to lock the radiative temperature tendency and total AHT to climatological values, even while the rotation rate is varied. This setup allows for a systematic study of the effects of radiative tendency and rotation rate on AHT. We find that rotation rate controls the latitudinal extent of the Hadley cell and the heat transport efficiency of eddies. Both the rotation rate and radiative tendency influence the strength of the Hadley cell and the strength of equator–pole energy differences that are important for AHT by eddies. These two controls do not always operate independently and can reinforce or dampen each other. In addition, we examine how individual AHT components, which vary with latitude, sum to a total AHT that varies smoothly with latitude. At slow rotation rates the mean meridional circulation is most important in ensuring total AHT varies smoothly with latitude, while eddies are most important at rotation rates similar to, and faster than, those of Earth.

scholarly journals Influence of Northern Hemispheric Winter Warming on the Pacific Storm Track

2021 ◽  
Author(s):  
Hyung-Ju Park ◽  
Kwang-Yul Kim
Keyword(s):  
Heat Flux ◽  
Global Warming ◽  
Energy Conversion ◽  
Storm Track ◽  
The Arctic ◽  
Late Winter ◽  
Turbulent Heat ◽  
Early Winter ◽  
Eddy Heat Flux ◽  
Northern Hemispheric

AbstractEffect of global warming on the sub-seasonal variability of the Northern Hemispheric winter (NDJFM) Pacific storm-track (PST) activity has been investigated. Previous studies showed that the winter-averaged PST has shifted northward and intensified, which was explained in terms of energy exchange with the mean field. Effect of global warming exhibits spatio-temporal heterogeneity with predominance over the Arctic region and in the winter season. Therefore, seasonal averaging may hide important features on sub-seasonal scales. In this study, distinct sub-seasonal response in storm track activities to winter Northern Hemispheric warming is analyzed applying cyclostationary empirical orthogonal function analysis to ERA5 data. The key findings are as follows. Change in the PST is not uniform throughout the winter; the PST shifts northward in early winter (NDJ) and intensifies in late winter (FM). In early winter, the combined effect of weakened baroclinic process to the south of the climatological PST and weakened barotropic damping to the north is responsible for the northward shift. In late winter, both processes contribute to the amplification of the PST. Further, change in baroclinic energy conversion is quantitatively dominated by eddy heat flux, whereas axial tilting of eddies is primarily responsible for change in barotropic energy conversion. A close relationship between anomalous eddy heat flux and anomalous boundary heating, which is largely determined by surface turbulent heat flux, is also demonstrated.

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