Circumpolar Jet Research Articles

Meridional Tripole Mode of Winter Precipitation over the Arctic and Continental North Africa–Eurasia

AbstractWintertime precipitation is vital to the growth of glaciers in the northern hemisphere. We find a tripole mode of precipitation (PTM), with each pole of the mode extending zonally over the eastern hemisphere roughly between 30°W and 120°E, and the positive/negative/positive structure for its positive phase extending meridionally from the Arctic to the continental North Africa–Eurasia. The large-scale dynamics associated with the PTM is explored. The positive phase of the PTM is associated with the negative while eastward-shifted phase of the North Atlantic Oscillation (NAO) and a zonal band of positive SST anomaly in the tropics, together with a narrowed Hadley cell and weakened Ferrel cell. While being north-eastward tilted and separated from their North Africa-Eurasia counterpart in the climatological mean, the upper-tropospheric westerly jets over the east Pacific and north Atlantic become extending zonally and shifting southward and hence form a circumpolar subtropical jet as a whole by connecting with the westerly jets over the North Africa-Eurasia. The enhanced zonal winds over the north Atlantic promote more synoptic-scale transient eddies which are waveguided by the jet streams. The polar vortex weakens and cold air dips southward from the North Pole. Further diagnosis of the E-vectors suggests that transient eddies have a positive feedback on the weakening of Ferrel cell. Opposite features are associated with the negative phase of the PTM. The reconstructed time series using multiple linear regression on the NAO index and the tropical SST averaged over 20°S– 20°N, can explain 62.4% of the variance of the original the original precipitation time series.

Stratospheric Impacts of Continuing CFC‐11 Emissions Simulated in a Chemistry‐Climate Model

AbstractTrichlorofluoromethane (CFC‐11, CFCl3) is a major anthropogenic ozone‐depleting substance and greenhouse gas, and its production and consumption are controlled under the Montreal Protocol. However, recent studies show that CFC‐11 emissions increased during 2014–2017 relative to 2008–2012. In this study, we use a chemistry‐climate model to investigate the stratospheric impacts of potential CFC‐11 emissions continuing into the future. As a sensitivity test, we use a high CFC‐11 scenario in which the inferred 2013–2016 average emissions of 72.5 Gg/yr is sustained to year 2100. This increases equivalent effective stratospheric chlorine by 15% in 2100, relative to the WMO (2018) baseline scenario in which future emissions decay with a bank release rate of 6.4%/year. Consistent with recent studies, the resulting ozone response has a linear dependence on the accumulated CFC‐11 emissions, yielding global and Antarctic spring total ozone sensitivity per 1,000 Gg of −0.37 and −3.9 DU, respectively, averaged over 2017–2100. The deepened ozone hole reduces UV heating, causing a colder Antarctic lower stratosphere in spring/early summer. Through thermal wind balance, this accelerates the circumpolar jet which in turn alters planetary and gravity wave propagation through the Southern Hemisphere stratosphere, and modifies the Brewer‐Dobson circulation. Age of air in the high scenario is slightly younger than the baseline in the lower stratosphere globally during 2090–2099, with a maximum change of −0.1 years. Coupled atmosphere‐ocean model simulations show that the resulting greenhouse gas impact of CFC‐11 is small and not statistically significant throughout the troposphere and stratosphere.

Antarctic Atmospheric River Climatology and Precipitation Impacts

AbstractThe Antarctic ice sheet (AIS) is sensitive to short‐term extreme meteorological events that can leave long‐term impacts on the continent's surface mass balance (SMB). We investigate the impacts of atmospheric rivers (ARs) on the AIS precipitation budget using an AR detection algorithm and a regional climate model (Modèle Atmosphérique Régional) from 1980 to 2018. While ARs and their associated extreme vapor transport are relatively rare events over Antarctic coastal regions (∼3 days per year), they have a significant impact on the precipitation climatology. ARs are responsible for at least 10% of total accumulated snowfall across East Antarctica (localized areas reaching 20%) and a majority of extreme precipitation events. Trends in AR annual frequency since 1980 are observed across parts of AIS, most notably an increasing trend in Dronning Maud Land; however, interannual variability in AR frequency is much larger. This AR behavior appears to drive a significant portion of annual snowfall trends across East Antarctica, while controlling the interannual variability of precipitation across most of the AIS. AR landfalls are most likely when the circumpolar jet is highly amplified during blocking conditions in the Southern Ocean. There is a fingerprint of the Southern Annular Mode (SAM) on AR variability in West Antarctica with SAM+ (SAM−) favoring increased AR frequency in the Antarctic Peninsula (Amundsen‐Ross Sea coastline). Given the relatively large influence ARs have on precipitation across the continent, it is advantageous for future studies of moisture transport to Antarctica to consider an AR framework especially when considering future SMB changes.

Sensitivity of the Southern Hemisphere circumpolar jet response to Antarctic ozone depletion: prescribed versus interactive chemistry

Abstract. Southern Hemisphere lower-stratospheric ozone depletion has been shown to lead to a poleward shift of the tropospheric jet stream during austral summer, influencing surface atmosphere and ocean conditions, such as surface temperatures and sea ice extent. The characteristics of stratospheric and tropospheric responses to ozone depletion, however, differ among climate models depending on the representation of ozone in the models. The most appropriate way to represent ozone in a model is to calculate it interactively. However, due to computational costs, in particular for long-term coupled ocean–atmosphere model integrations, the more common way is to prescribe ozone from observations or calculated model fields. Here, we investigate the difference between an interactive and a specified chemistry version of the same atmospheric model in a fully coupled setup using a nine-member chemistry–climate model ensemble. In the specified chemistry version of the model the ozone fields are prescribed using the output from the interactive chemistry model version. We use daily resolved ozone fields in the specified chemistry simulations to achieve a very good comparability between the ozone forcing with and without interactive chemistry. We find that although the shortwave heating rate trend in response to ozone depletion is the same in the different chemistry settings, the interactive chemistry ensemble shows a stronger trend in polar cap stratospheric temperatures (by about 0.7 K decade−1) and circumpolar stratospheric zonal mean zonal winds (by about 1.6 m s−1 decade−1 as compared to the specified chemistry ensemble. This difference between interactive and specified chemistry in the stratospheric response to ozone depletion also affects the tropospheric response. However, an impact on the poleward shift of the tropospheric jet stream is not detected. We attribute part of the differences found in the experiments to the missing representation of feedbacks between chemistry and dynamics in the specified chemistry ensemble, which affect the dynamical heating rates, and part of it to the lack of spatial asymmetries in the prescribed ozone fields. This effect is investigated using a sensitivity ensemble that was forced by a three-dimensional instead of a two-dimensional ozone field. This study emphasizes the value of interactive chemistry for the representation of the Southern Hemisphere stratospheric-jet response to ozone depletion and infers that for periods with strong ozone variability (trends) the details of the ozone forcing could also have an influence on the representation of southern-hemispheric climate variability.

Global climate modeling of Saturn's atmosphere. Part II: Multi-annual high-resolution dynamical simulations

The Cassini mission unveiled the intense and diverse activity in Saturn's atmosphere: banded jets, waves, vortices, equatorial oscillations. To set the path towards a better understanding of those phenomena, we performed high-resolution multi-annual numerical simulations of Saturn's atmospheric dynamics. We built a new Global Climate Model [GCM] for Saturn, named the Saturn DYNAMICO GCM, by combining a radiative-seasonal model tailored for Saturn to a hydrodynamical solver based on an icosahedral grid suitable for massively-parallel architectures. The impact of numerical dissipation, and the conservation of angular momentum, are examined in the model before a reference simulation employing the Saturn DYNAMICO GCM with a 1/2° latitude-longitude resolution is considered for analysis. Mid-latitude banded jets showing similarity with observations are reproduced by our model. Those jets are accelerated and maintained by eddy momentum transfers to the mean flow, with the magnitude of momentum fluxes compliant with the observed values. The eddy activity is not regularly distributed with time, but appears as bursts; both barotropic and baroclinic instabilities could play a role in the eddy activity. The steady-state latitude of occurrence of jets is controlled by poleward migration during the spin-up of our model. At the equator, a weakly-superrotating tropospheric jet and vertically-stacked alternating stratospheric jets are obtained in our GCM simulations. The model produces Yanai (Rossby-gravity), Rossby and Kelvin waves at the equator, as well as extratropical Rossby waves, and large-scale vortices in polar regions. Challenges remain to reproduce Saturn's powerful superrotating jet and hexagon-shaped circumpolar jet in the troposphere, and downward-propagating equatorial oscillation in the stratosphere.

On the dynamical nature of Saturn’s North Polar hexagon

An explanation of long-lived Saturn’s North Polar hexagonal circumpolar jet in terms of instability of the coupled system polar vortex - circumpolar jet is proposed in the framework of the rotating shallow water model, where scarcely known vertical structure of the Saturn’s atmosphere is averaged out. The absence of a hexagonal structure at Saturn’s South Pole is explained similarly. By using the latest state-of-the-art observed winds in Saturn’s polar regions a detailed linear stability analysis of the circumpolar jet is performed (i) excluding (“jet-only” configuration), and (2) including (“jet + vortex” configuration) the north polar vortex in the system. A domain of parameters: latitude of the circumpolar jet and curvature of its azimuthal velocity profile, where the most unstable mode of the system has azimuthal wavenumber 6, is identified. Fully nonlinear simulations are then performed, initialized either with the most unstable mode of small amplitude, or with the random combination of unstable modes. It is shown that developing barotropic instability of the “jet+vortex” system produces a long-living structure akin to the observed hexagon, which is not the case of the “jet-only” system, which was studied in this context in a number of papers in literature. The north polar vortex, thus, plays a decisive dynamical role. The influence of moist convection, which was recently suggested to be at the origin of Saturn’s North Polar vortex system in the literature, is investigated in the framework of the model and does not alter the conclusions.

A δ-plane simulation of anticyclones perturbing circumpolar flows to form a transient north polar hexagon

Saturn's North Polar Hexagon was discovered by Godfrey who pieced together map projections of images captured by the Voyager mission to unveil a hexagonal structure over the north pole of Saturn. This article attempts to answer whether or not a hexagonal structure can be formed through anticyclones impinging on the dominant eastward circumpolar flow and is in part based upon the proposed theory by Allison et al. that the Hexagon may be the result of at least one impinging anticyclone perturbing a circumpolar jet centrally located around the 76°N latitude. A high-latitude δ-plane approximation is used to simulate the interaction between an initially circular circumpolar jet and at least one perturbing anticyclone. Our simulations with one perturbing anticyclone failed to form a hexagonal structure; yet by including an additional anticyclone it was found that depending on the strength, location and radius of the perturbing anticyclones a hexagonal feature could develop. However, the longevity and drift rate of the actual Hexagon must be attributed to other factors not considered in this paper.

Eddy Fluxes and Jet-Scale Overturning Circulations in the Indo–Western Pacific Southern Ocean

AbstractThe relationship between Antarctic Circumpolar Current jets and eddy fluxes in the Indo–western Pacific Southern Ocean (90°–145°E) is investigated using an eddy-resolving model. In this region, transient eddy momentum flux convergence occurs at the latitude of the primary jet core, whereas eddy buoyancy flux is located over a broader region that encompasses the jet and the interjet minimum. In a small sector (120°–144°E) where jets are especially zonal, a spatial and temporal decomposition of the eddy fluxes further reveals that fast eddies act to accelerate the jet with the maximum eddy momentum flux convergence at the jet center, while slow eddies tend to decelerate the zonal current at the interjet minimum. Transformed Eulerian mean (TEM) diagnostics reveals that the eddy momentum contribution accelerates the jets at all model depths, whereas the buoyancy flux contribution decelerates the jets at depths below ~600 m. In ocean sectors where the jets are relatively well defined, there exist jet-scale overturning circulations with sinking motion on the equatorward flank and a rising motion on the poleward flank of the jets. These jet-scale TEM overturning circulations, which are also discernible in potential density coordinates, cannot be attributed to Ekman downwelling because the Ekman vertical velocities are much weaker and their meridional structure shares little resemblance to the rapidly varying jet-scale overturning pattern. Instead, the location and structure of these thermally indirect circulations suggest that they are driven by the eddy momentum flux convergence, much like the Ferrel cell in the atmosphere.

Linkage between the East Asian January temperature extremes and the preceding Arctic Oscillation

ABSTRACTThis study investigated the potential connection of the October–December Arctic Oscillation (AO‐OND) with the following January East Asian temperature extremes and the possible mechanisms. It was found that the extreme cold (warm) events are less (more) frequent in January over East Asia following a positive phase of AO‐OND, which might be attributed to the intrinsic persistence of AO‐OND in stratosphere and the memory of Eurasian snow cover. It is revealed that the barotropic structure of AO‐OND could extend to stratosphere. By the following January, wave activities propagate from stratosphere downwards to upper troposphere, then bent equatorwards to mid‐latitudes. Consequently, the January circumpolar jet (polar vortex) gets strengthened (colder) because the equatorward‐pointing (upwards) wave activities correspond to poleward meridional eddy momentum (eddy heat) flux. In such a way, the anomalous AO‐OND persists into the following January. On the other hand, positive phase of AO‐OND causes significant surface warming in most parts of Eurasia, leading to Eurasian snow melt. The October–December snow melt has intrinsic climatic memory and further weakens the January Siberian High through reducing surface albedo. Besides, the surface warming in North Europe because of reduced surface albedo caused by snow melt could stimulate a Rossby wave train propagating eastwards across Eurasia, which restrains the blocking events around Ural region. In such a context, the incidence of extreme warm (cold) events over East Asia is more (less) frequent.

Long-time asymptotic states of forced two-dimensional barotropic incompressible flows on a rotating sphere

This study re-examines a long-time asymptotic state of a two-dimensional barotropic incompressible flow with a small-scale, Markovian random forcing on a rotating sphere. Numerical simulations with different rotation rates of the sphere and different wavenumbers of the forcing are performed from zero initial condition. The integration time is extended to around 100–500 times that of the previous study by Nozawa and Yoden [Phys. Fluids 9, 2081 (1997)]. At an early stage of the time integration, a multiple zonal-band structure or a structure with westward circumpolar jets emerges. However, in the course of time development, a multiple zonal-band structure is found to appear in all cases. The multiple zonal-band structure then enters quasisteady state, showing little energy increase with nearly steady energy spectrum. This is followed by a sudden merger/disappearance of the jets, accompanying an energy increase, and at the final stage of the time integration, a zonal-band structure with only two or three jets is realized in all cases. The characteristic total wavenumber of this asymptotic state is far lower than the Rhines wavenumber of the zonal flow, which suggests that the inverse energy cascade is not totally stopped by the β effect.

Meteorological predictions for candidate 2007 Phoenix Mars Lander sites using the Mars Regional Atmospheric Modeling System (MRAMS)

The 2007 Phoenix Mars lander will land in the late afternoon at a high northern latitude in the late northern hemisphere spring season. Various types of Mars atmospheric model simulations (general circulation model, mesoscale, and large‐eddy simulation) were used to investigate the plausible range of meteorological conditions that the lander will likely experience during its landed mission and entry, descent, and landing phase. These studies were carried out in support of Phoenix mission atmospheric risk assessment tasks. The model results reveal a circumpolar jet with associated relatively weak transient baroclinic disturbances that appear not to severely impact the potential Phoenix landing sites, even under differing plausible atmospheric dust loading scenarios. At the local time of landing, modeling results indicate vigorous (dry) planetary boundary layer convection extending from the surface to perhaps 5 km.

Rossby Waves and Jets in Two-Dimensional Decaying Turbulence on a Rotating Sphere

Abstract Jet formation in decaying two-dimensional turbulence on a rotating sphere is reviewed from the viewpoint of Rossby waves. A series of calculations are performed to confirm the behavior of zonal mean flow generation on the parameter space of the rotation rate Ω and Froude number Fr. When the flow is nondivergent and Ω is large, intense easterly circumpolar jets tend to emerge in addition to the appearance of a banded structure of zonal mean flows with alternating flow directions. When the system allows surface elevation, circumpolar jets disappear and an equatorial easterly jet emerges with increasing Fr. The appearance of the intense easterly jets can be understood by the angular-momentum transport associated with the generation, propagation, and absorption of Rossby waves. When the flow is nondivergent, long Rossby waves tend to be absorbed near the poles. In contrast, when Fr is large, Rossby waves can hardly propagate poleward and tend to be absorbed near the equator.

Energy Accumulation in Easterly Circumpolar Jets Generated by Two-Dimensional Barotropic Decaying Turbulence on a Rapidly Rotating Sphere

Abstract A series of numerical experiments on two-dimensional decaying turbulence is performed for a barotropic fluid on a rotating sphere. Numerical calculations have confirmed two important asymptotic features: emergence of the banded structure of zonal flows and their extreme latitudinal inhomogeneities in which kinetic energy is accumulated into the easterly circumpolar jets. The banded structure of zonal flows is established relatively early on in the initial stage. Later, after extended periods of time integration, only the circumpolar jets are intensified gradually, while there is no further evolution in the banded structure in the low and midlatitudes. Wave activity flux analysis illustrates that the initial vortices in the low and midlatitudes propagate poleward as Rossby waves and converge to produce easterly circumpolar flows. In association with this convergence, accumulation of the mean zonal component of kinetic energy proceeds. The tendency for the accumulation becomes strong as the rotation rate is increased, and nearly all of the kinetic energy is concentrated to the circumpolar flows in cases of rapid rotation. A theoretical model is constructed under the assumption that a circumpolar jet emerges around the latitude where the local Rhines scale is equal to the distance from the Pole, and that initial vortices at the lower latitudes contribute to the generation of the jets. The model describes the mean zonal component of kinetic energy and the averaged speed and width of the circumpolar jets as functions of the rotation rate, which agree satisfactorily with the numerical results.

Circumpolar jets emerging in two-dimensional non-divergent decaying turbulence on a rapidly rotating sphere

A series of numerical experiments on two-dimensional decaying turbulence are performed for a non-divergent fluid on a rotating sphere, with attention focused on scaling properties of spontaneous circumpolar jets. The numerical calculations show that strong circumpolar westward (retrograde) jets emerge clearly in high latitudes at a large rotation rate Ω . A scaling theory is proposed for the jet width proportional to Ω - 1 / 4 , and the jet strength to Ω 1 / 4 , which agrees well with the numerical results. A noteworthy asymptotic feature is that kinetic energy is entirely concentrated on the circumpolar jets under large rotation rates.

Jupiter's atmospheric temperatures: From Voyager IRIS to Cassini CIRS

Retrievals performed on Cassini Composite Infrared Spectrometer data obtained during the distant Jupiter flyby in 2000/2001 have been used to generate global temperature maps of the planet in the troposphere and stratosphere, but to higher latitudes than were shown previously by Flasar et al. [Flasar, F.M., 39 colleagues, 2004a. Nature 427, 132–135; Flasar, F.M., 44 colleagues, 2004b. Space Sci. Rev. 115, 169–297]. Similar retrievals were performed on Voyager 1 IRIS data to provide the first detailed IRIS map of the stratosphere, and high latitudes in the troposphere. Thermal winds were calculated for each data set and show strong vertical shears in the zonal winds at low latitudes, and meridional temperature gradients indicate the presence of circumpolar jets, as well. The temperatures retrieved from the two spacecraft were also compared with yearly ground-based data obtained over the intervening two decades. Tropospheric temperatures reveal gradual changes at low latitudes, with little obvious seasonal or short-term variation [Orton et al., 1994. Science 265, 625–631]. Stratospheric temperatures show much more complicated behavior over short timescales, consistent with quasi-quadrennial oscillations at low latitudes, as suggested in prior analyses of shorter intervals of ground-based data [Orton et al., 1991. Science 252, 537–542; Friedson, A.J., 1999. Icarus 137, 34–55]. A scaling analysis indicates that meridional motions, mechanically forced by wave or eddy convergence, play an important role in modulating the temperatures and winds in the upper troposphere and stratosphere on seasonal and shorter timescales. At latitudes away from the equator, the mechanical forcing can be derived simply from a temporal record of temperature and its vertical derivative. Ground-based observations with improved vertical resolution and/or long-term monitoring from spacecraft are required for this purpose, though the Voyager and Cassini data given indications that the magnitude of the forcing is very small.

Possible effects of breaking gravity waves on the circulation of the middle atmosphere of Mars

A simplified (quasi‐geostrophic, beta‐plane) dynamical model of the zonal‐mean flow is used to investigate the possible effects of breaking internal gravity waves on the circulation in the middle atmospheric region (∼10–100 km altitude) of Mars. The gravity wave parameterization employed is basically the saturation parameterization of Lindzen (1981) which has been utilized in several terrestrial modeling studies. Numerical simulations are performed for a range of plausible values of the gravity wave parameters and for different representations of the mean flow thermal forcing, with a focus on the effects of topographically forced stationary gravity waves on the winter hemisphere circulation. The results of the model simulations show that breaking gravity waves (of intermediate horizontal scales, ∼100–1000 km wavelengths) could act to “close off” the winter westerly circumpolar jet in the ∼40–80 km altitude region and induce strong high‐latitude warming at these levels. The latter could explain recent thermal measurements indicating that Martian winter polar latitudes may be very warm, far above radiative equilibrium, in this middle atmospheric region [Deming et al., 1986]. For the most plausible range of parameter values breaking gravity waves do not induce much warming below ∼40 km, consistent with available data showing that winter high latitudes are normally very cold at lower levels. Several “dust storm” cases indicate that breaking gravity waves possibly could act to induce a very large polar warming at relatively low altitudes, such as was observed during the 1977 winter solstice dust storm. However, quite large gravity wave amplitudes and/or relatively long horizontal wavelengths are required for such strong low‐level effects; thermal forcing associated with dust heating might be a source for such anomalous gravity wave activity during a global dust storm. Summer simulations indicate that breaking gravity waves might alter the mean flow at somewhat higher levels than in the winter hemisphere, as a consequence of the presence of westerlies in the lower atmosphere. This could explain the presence of a warm summer pole in the recent 50–80 km thermal measurements of Deming et al. Several aspects of the results relating to the middle atmospheric circulation and the polar warming phenomenon are discussed. The possible importance of breaking gravity waves for constituent transports in the middle atmosphere of Mars is also briefly considered.

Ozone destruction by chlorine radicals within the Antarctic vortex: The spatial and temporal evolution of ClO‐O3 anticorrelation based on in situ ER‐2 data

In situ O3 and ClO data obtained from the ER‐2 aircraft are used to define the chemical evolution of the Antarctic vortex region from August 23 to September 22, 1987. Initial conditions are characterized at aircraft flight altitude (18 km) by highly amplified ClO mixing ratios (800 parts per trillion by volume (pptv)) within a well‐defined “chemically perturbed region” (CPR) poleward of the circumpolar jet, within which ozone exhibits limited erosion (∼15%) in middle to late August. Within this CPR, ozone decays consistently throughout the course of a 10‐flight series, such that by late September, 75% of the O3 has disappeared within the region of highly amplified ClO concentrations (which reached 500 times normal levels at ER‐2 cruise altitude). As this ozone depletion develops, O3 and ClO exhibit dramatic negative correlation on isentropic surfaces, obtained as the aircraft passed through the edge of the CPR. Taken in conjunction with an analysis of the mechanisms defining the rate of catalytic O3 destruction, it is concluded that ClO is an essential constituent in the catalytic destruction of ozone within the vortex. Therefore it is concluded that the observed disappearance of ozone within the Antarctic vortex would not have occurred in the absence of global chlorofluorocarbon release.

Planetary-scale wave structure in the Martian atmosphere

Wave-like perturbations are found in the Mariner 9 IRIS atmospheric temperature data during late Northern Hemisphere winter in a latitude band between 45°N and 65°N. The nature of the data base prevents a unique separation of spatial and temporal behavior, but Fourier analysis of the data constrains the waves to discrete combinations of planetary wavenumber and period. One major spectral component possesses a meridional amplitude cross section with a maximum near the 1-mbar level at 60°N and is strongly correlated with the circumpolar jet observed in thermal winds calculated from the mean meridional temperature cross section. This feature is consistent with the low-wavenumber baroclinic waves observed in Viking Lander data, and the vertical structure reflects the behavior anticipated for a vertically penetrating quasi-geostrophic disturbance. Other possible origins for the wave cannotbe ruled out, however. Among these is a stationary wave forced by wavenumber-2 topographic relief.

A Transect of the Southern Circumpolar Jet Stream

Abstract Aitken nuclei and ozone concentrations were measured, in concert with meteorological variables, while flying beneath the core of a jet stream at the 400 mb level. Stratospheric air which subsided to the flight level was richer in ozone, but similar in particle concentration when compared with adjacent tropospheric air. Concurrent carbon tetrachloride measurements by E. Robinson showed the tropospheric air to be richer in CCL4.

A PRELIMINARY REPORT ON OZONE OBSERVATIONS AT LITTLE AMERICA, ANTARCTICA1

Summaries of ozone measurements made at Little America, Antarctica during 1957 and 1958 are presented. Data include both total ozone observations made with a Dobson Ozone Spectrophotometer and surface ozone concentrations measured with the automatic ozone recorder developed by Regener. Wind and ozone roses were constructed to examine the variation of surface ozone with wind direction, and in addition the net meridional transport of surface ozone was computed for each month for a year. The computed northward transport of surface ozone during the winter months of June through September suggests a model for atmospheric circulation in the Antarctic. Assuming no ozone is created or destroyed by photo-chemical or other means during this dark period and that Little America is representative of its latitude, steady-state conditions require that the low-level outflow of ozone be compensated by inflow at other levels. Both the lower stratospheric circumpolar jet inhibiting meridional transport and the stability of the Antarctic stratosphere inhibiting downward vertical transport lead us to ascribe the principal ozone influx to the troposphere above the surface layer. Computations of the tropospheric ozone concentrations required to replace the low-level loss of ozone, using Rubin's values for the vertical distribution of the tropospheric mass transports, are in good agreement with the observations made by ozonesonde at Halley Bay. It thus appears that some of the ozone manufactured in the sunlit stratosphere of lower latitudes which enters the troposphere through the tropopause gap associated with the mid-latitude jet stream is transported into the Antarctic by winds of the vigorous winter storms which move around and into the continent, and finally sinks and then flows northward again as part of the 2- to 3-km. thick surface layer.