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A description is given of experiments carried out during 1949 and early 1950 that were designed to produce some phenomenon exhibiting effects of the resultant horizontal Coriolis force on a symmetrical vortex that results from the latitude variation of the Coriolis force. A circular cap of dense liquid at the base of a small hemispherical shell filled with liquid was forced to rotate about a vertical axis independently of the rate of rotation of the remaining fluid and containing vessels. Within the ranges of 20 to 150 r.p.m. for the vessel and 0 to 120 relative r.p.m. for the cap vortex, the center of mass of the polar cap never showed appreciable displacements away from the polar axis exept for a range of sufficiently high relative rotations when the vortex was anticyclonic in sense. Numerical checks are given with a simplified calculation in spherical coordinates of the torque equilibrium for the vortex as a whole. DOI: 10.1111/j.2153-3490.1950.tb00325.x

In winter the polar stratospheric air within the earth's shadow forms the core of an intense ‘cold low’ which extends from about 10 km to at least 50 km and possibly to the base of the ionosphere. Compared with the tropospheric general circulation, this vortex seems to be remarkably stable, particularly in the Southern Hemisphere. Recent research work in Canada and the United States on the characteristics of the vortex is reviewed. The chief conclusions are that the vortex is more stable in the Southern than in the Northern Hemisphere, that ‘explosive warmings’ in the lower stratosphere of the Northern Hemisphere follow the breakdown of the vortex at high levels close to the pole, and that the breakdown extends from above downward over a period of several days. It is suggested that the high-level breakdown is correlated with solar activity.

Figures 4 and 6 of the paper [Palmer, 1959] illustrated the time variation of atmospheric pressure, temperature, and density at two stations in the core of the vortex prior to and during the warming of the arctic stratosphere in 1958. Since that time, the entire polar cap has been analyzed, using the complete IGY data at the 15-km level, to determine the daily distribution of these same variables. The map series from January 11 through January 30 is presently being prepared for publication.1 The influence of the land and sea distribution is manifest in the asymmetry of the stationary features on the maps.

Large changes in the temperature and ozone content of the stratosphere at Aspendale (38 S, 145 E), Hobart (43 S, 148 E) and Macquarie Island (54 S, 160 E) are associated with the passage of planetary waves in the Antarctic polar vortex. Application of the conservation equation to an elliptical model of the polar vortex, using both ozone and potential temperature as tracers, leads to order of magnitude estimates of the vertical and horizontal motions and transports involved. Estimated vertical motions are of the order of 1 cm s−1. At the 30-mb level there is significant horizontal advection of ozone into the vortex in the vicinity of the cold troughs and out of the vortex near the ridges, but horizontal advection of heat appears to be negligible.

The general circulation of the stratosphere is described briefly in the light of recent observations, with particular emphasis on the polar vortex of winter and its evolution. It is concluded that the observed breakdowns in the polar vortex are some sort of instability phenomenon. Baroclinic instability is investigated both through a four-level finite-difference model and a two-layer analytic model. Although the evidence is not entirely conclusive, the analytic model, consisting of a tropospheric layer without shear and a stratospheric layer with constant shear, appears to be stable regardless of shear or wavelength. The finite-difference model, however, does indicate instability of the higher modes provided that the stratospheric shear is very strong. The discrepancy may lie in the fact that long internal waves are not excluded from the finite-difference model as they are from the stratospheric layer of the analytic model. Inertial and barotropic instability are also briefly discussed. Although inertial instability is dismissed as an explanation for the observed developments, barotropic instability may not so be dismissed. It is suggested that future research be directed to the problem of barotropic instability.

This paper presents a description of experiments on the stability of a polar vortex and offers a theory for the experimental results. The experimental set-up is a rotating spherical shell, containing two immiscible liquids. The denser liquid covering the polar region is given a rotation with respect to the spherical shell, and observations are made to determine the tendency for the vortex to be displaced equatorward. The observations indicate that a cyclone centered near the pole is stable in the sense that its center of mass remains near the pole. An anticyclone tends to be unstable, however, so that its center of mass is displaced equatorward if its rotation is sufficiently strong. In connection with the experiments, the equations of motion of a simplified vortex were developed for a spherical earth. These are applied to obtain an instability criterion for a polar vortex. Other applications of these equations are described. One of these is a study of the motion of a vortex imbedded in a uniform...

The flow at 500 mb. is compared with that at 100 mb. With the exception of the polar vortex, the patterns at the two levels tend to show a distinct similarity, with the major exception that small-scale features at 500 mb. are not present at 100 mb. In middle latitudes, the wind speeds at the two levels are of the same order of magnitude, with a systematic excess of the 100-mb. speeds over the 500-mb. speeds at latitudes 30° and farther south. In the region of the polar vortex, heights at the two levels are still well correlated. Variations in height over long periods tend to be much larger at 100 mb. than at 500 mb. Similarly, the winds at 100 mb. are much stronger than those at 500 mb.

An analysis of the large-scale eddy processes which may be responsible for the northward and downward transport of trace substances in the stratosphere is performed for cases of a major and a “minor” breakdown of the polar night vortex. By using vertical velocities obtained from the thermodynamic equation, eddy covariances between the vertical velocity and the northward component of the wind were computed on a daily basis for middle and higher latitudes. The results indicate that this quantity reverses very rapidly from positive to large negative values just after the major breakdown of the polar vortex, thus providing an efficient mechanism for northward and downward trace substance transport at this time of the year. This result is also corroborated through large-scale trajectory calculations. A similar analysis is performed for a fall period in which the intensifying polar vortex circulation deforms into a regime dominated by large-scale cyclones and anticyclones (“minor” breakdown), but then reforms into an intense midwinter polar vortex. This situation also appears to be favorable for northward and downward transport, but the processes are considerably weaker than for the major breakdown case. This result may indicate why the largest buildup of trace substance concentrations in the high-latitude lower stratosphere occurs during late winter and early spring.

Seasonal variations in the 50-mb. circulation over the Antarctic during 1958 are discussed and the features observed in 1957 are compared with those found in 1958. Both years exhibited similar patterns in the fall and winter seasons but differed somewhat in spring and summer. In 1957, the polar vortex of winter began to weaken in early October and by November 21 a closed anticyclone at 50 mb. encompassed the continent. In 1958, the breakdown of the polar vortex was more gradual and by the end of November the 50-mb. circulation was characterized by an irregular pattern of closed cyclones and anticyclones rather than a dominant anticyclone.

The intensity of the polar vortex at 10 mb is used to calculate theoretical values of mean total ozone north of 40° latitude. A satisfactory fit is attained between the development in time of the theoretical ozone and that of the mean of the observed total ozone. The results lead to the conclusion, that a one-cell mean meridional motion relative to the polar night vortex is important for the transport of heat and ozone.

Stratospheric air is stably stratified, but vertical mixing is indicated by measurements of ozone and nuclear bomb debris. Tracer measurements suggest a mean net circulation by which air enters the stratosphere in the tropics, is transported polewards and leaves the stratosphere at higher latitudes. The air transport seems to be sufficient for full replacement of stratospheric air within two years. The tropical tropopause is regarded as the result of ascending cold air being mixed with warmer air from higher latitudes. The polar tropopause is regarded as the mixing layer between an upper current of stratospheric air going downwards and a lower region where convective currents occur. Springtime increase of ozone is thought to be due to subsidence associated with the breakdown of the stratospheric polar vortex, beginning at a high level.

Vertical velocities have been computed for the lower stratosphere for two independent winter periods, by employing a form of the adiabatic method. The regions studied were in both cases outside the polar vortex. The flow pattern was divided into stationary (long-wave) and transient (short-wave) components. The vertical velocity pattern associated with the stationary long wave is precisely that described by Kochanski [3]; i.e., the air rises in moving from warm troughs to cold ridges. The pattern associated with the short waves is more complicated. There is a maximum of warm, advection in the vicinity of short-wave ridges, and cold advection near troughs. Local temperature changes, however, very nearly compensate the advection, with the net result that in the mean the vertical velocities associated with short-wave patterns are small, but tend to be positive near ridges and negative near troughs. Superimposition of the short and long wave, however, can lead to any conceivable combination of signs o...

A new set of long-period means for sea level pressure and 700-mb. height, based on 12 recent years of reliable upper-level and surface observations in the Northern Hemisphere, is constructed. Comparison with the normals currently in use, which are based on data prior to 1950, reveals additional information and some significant differences, principally at high and low latitudes. The three cells of the polar vortex at 700 mb. are not as deep as shown in the normals, the cells over Baffin Island and the Siberian Arctic are farther north, and the Kamchatka cell is found primarily over the Bering Sea rather than over land. The Pacific High at 700 mb. is tricellular on an annual basis, with the additional Philippine cell becoming the dominant cell ill late winter. Other new features in the 700-mb. means include troughs near Spitzbergen, Alaska, the Philippine Sea, and the Bay of Bengal; and Highs in northeastern Siberia and the Caspian Sea area. Patterns of height differences between the new means and ...

The large scale atmospheric nuclear testing in 1961 and 1962 afforded the opportunity of observing changes in the distribution of radioactivity and its relationship to stratospheric circulation patterns. Air-craft observations in early 1963 from 15 to 21 km over the Northern Hemisphere and balloon observations to 30 km at 31N together with 50-mb constant pressure charts suggest that most of the debris injected into the polar stratosphere during November-December 1962 was confined to a relatively small volume north of 70N. This debris did not appreciably affect the zone south of 70N until February 1963 when the circumpolar vortex split into two cyclonic cells and moved southward, one cell over Europe, the other over Canada and the United States. This contaminant was then observed as far south as 25N. An anticyclone which moved over Alaska during February 1963 had different radioactivity characteristics than did the polar vortex. These well-defined large-scale eddies maintained their identity until...

Significant correlations have been found between year to year mean latitudes of the surface high pressure belt, L, over eastern Australia and atmospheric parameters such as total ozone, winds and temperatures at various levels in the troposphere and stratosphere, and rainfall. In those years when, in late winter and spring, the high pressure belt lies nearer to the Equator it appears that the Hadley circulation and poleward transport processes in the lower stratosphere and upper troposphere in middle latitudes are stronger. This is probably also associated with the earlier breakdown of the winter stratospheric polar vortex. Evidence is presented to support the view that L is determined to a good approximation by the criterion for baroclinic instability which was derived by Phillips and Smagorinsky and applied to climatology by Flohn and Henning. Thus variations in L are related to variations in the driving force of the Hadley circulation, which in turn may well be related to variations in sea surface temperature. This encourages the view that an empirical and theoretical basis for long-range seasonal forecasts of temperate zone climate may be in prospect. The results should lead to a greater understanding of the nature of global climatic change.

The development of a polar substorm consists of two distinctly different phases; i.e. the growth phase lasting 1 or 2 hr prior to the well-defined breakup, and the subsequent expansion phase. The essential signatures for the growth phase are a gradual development of the polar vortex type current without remarkable current enhancement in the auroral belt (DP 2 field), and the asymmetric growth of the low latitude field-depression in the eveningmidnight-early morning sector (DRT field). After a distinct DP 2 and DRT fields, drastic changes occur in the substorm development and the expansion phase starts. The expansion phase is characterized by a rapid expansion of the auroral electrojet disturbance (AEJ or DP-B field) in the high latitudes, and a rapid recovery of the field-depression near the midnight meridian and the subsequent asymmetric development of the disturbance field in the low latitudes. Considering the close associations of the interplanetary magnetic disturbance field with the magnetospheric field and particle disturbances which have been confirmed by various authors, it may be concluded that the growth phase is the precursory excitation of the magnetospheric background and the energy-storage or the energy-conversion stage in the magnetosphere due to the non-equilibrium magnetospheric convection, while the expansion phase is the energy-diversion stage in the magnetosphere. The disturbance field in the growth phase is a nucleus-like, fundamental element for the substorm breakup and it is essentially different from the expansion phase disturbance in quality and in quantity.

The radioactive fall-out during 1959 shows that the Russian October 1958 debris dominated the northern hemisphere and came down with a residence time corresponding to about 8 months. The rest of the world had a steady fall-out rate of about 0.06 mc/mi/sup 2//in. of rain throughout the year, whereas values for the northern hemisphere came down to this value in the months of September, October, and November when the Russian debris was apparently exhausted. Thus. it appears that there is a world-wide fall-out rate of about 0.06 mc/mi/sup 2//in. of rain which is nearly independent of the Russian polar debris and which is probably from the equatorial tests. Using the estimate of ihe amount of material injected into the stratosphere, this world-wide rate of fall-out corresponds to a residence time of about 5 years for equatorial injections. Goldie suggested that the meridional circulation at levels well within the stratosphere consists of an up-welling of air at the equator. followed by a polar fiow, a down-welling in the polar region, and an equatorward movement above the troposphere at approximately 24 km. In addition, a seasonal perturbation of this circulation occurs in the long winter night near the pole. It results inmore » an accumulation of material at high levels near the pole, until the sun returns in the spring, when a sudden break-up occurs and the material is rapidly carried toward the troposphere. This model explains quite well most of the present observations on radioactive fall- out. The polar debris would Naturally have a shorter residence time because it would be introduced in the last steps of the cycle, the equatorial would have a longer residence time, having been introduced at the beginning of the cycle, and the spring breakup of the polar vortex would account for the well-known spring maximum in the rate of radioactive fall-out. The residence times of material injected near the equator and the pole, respectively, permit a quantitative estimate of the intensity and depth of the circulation to be made. The meridiomal velocity deduced for the equatorially directed low stratospheric current is about l to 3 miles per hour, whereas that for the poleward high stratospheric current is about one-tenth as large. This requires, of course, that 90% of the stratospheric air be concentrated in the high brand. (auth)« less

Total ozone amounts are shown to vary with the motion systems of the stratospheric polar vortex. Two cold outbreaks, one over Europe in 1959 and the other over North America in 1960, produced similar pronounced minima in the total ozone records. The results support the hypothesis that major anomalies in the horizontal and seasonal distributions of total ozone are related to dynamical activity in the polar-night vortex and the stratospheric warm belt.

Circumpolar decadal 500-mb mean maps and data for middle and high latitudes are presented for January and July, 1950–59. These maps are based largely on recent Northern Hemispheric upper-air observations and are superior to previous normals. The 500-mb January map is the first long-period mean for that month to show a splitting of the jet stream over the North Pacific with a secondary branch passing to the north of Alaska. In July, the polar vortex is rather symmetrically centered over the North Pole at 500 mb. The tendency during the past decade for the Aleutian and Icelandic lows to form winter auxiliary cells to the cast of the parent cells is supported by the sea-level-pressure data for January. Relatively low sea-level mean pressures in the vicinity of the North Pole are confirmed for July. It is implied that July mean virtual temperatures over the Polar Basin previously have bun underestimated by approximately 3K.

The meridional transport of relative angular momentum by transient eddies is computed from the wind data so far available from the Meteorological Rocket Network for the 25–60 km region. The transport is northward in winter and apparently of sufficient magnitude to account for the formation of the winter polar vortex. It is suggested that the eddies arise in response to the differential heating within the region produced by radiational effects. Zonal available potential energy and its generation are calculated and compared with the kinetic energy. The transformation of eddy kinetic energy to zonal kinetic energy is of the same order of magnitude as the generation of zonal available potential energy. The importance of eddy structures as compared with mean meridional motions appears to be similar to the earlier findings for the troposphere and lower stratosphere. It is concluded that the region from 25–60 km may generate its own kinetic energy in situ in winter and be essentially energetically indep...

The midwinter temperature changes of the mesosphere and stratosphere are described by means of Satellite Infrared Spectrometer and Selective Chopper Radiometer data, rocketsondes, and rocket grenade data, which show that the so-called stratospheric midwinter warmings extend at least into the upper mesosphere. Temperature changes of opposite sign take place at the same time at different levels, probably as a result of vertical motion. The event begins around a very high stratopause, ∼60 km, which descends 20 km within several days while the warming intensifies. At the same time the upper mesosphere and lower stratosphere cool. When the polar vortex breaks down, the warming reaches the lower stratosphere, the warm stratopause region is destroyed through cooling of the layer between 30 and 60 km, and the upper mesosphere warms. The mean vertical temperature profiles suggest that the upper mesosphere is cold at high latitudes in early winter and again in late winter, and that the warm upper mesospher...

The dynamics of the stratosphere sudden warming phenomenon is discussed in terms of the interaction of vertically propagating planetary waves with zonal winds. If global-scale disturbances are generated in the troposphere, they propagate upward into the stratosphere, where the waves act to decelerate the polar night jet through the induction of a meridional circulation. Thus, the distortion and the break-down of the polar vortex occur. If the disturbance is intense and persists, the westerly jet may eventually disappear and an easterly wind may replace it. Then “critical layer interaction” takes place. Further intensification of the easterly wind and rapid warming of the polar air are expected to occur as well as weakening of the disturbance. The model is verified by numerical integrations of the adiabatic-geostrophic potential vorticity equation. Computed results possess features similar to those observed in sudden warming phenomena.

The selection of an appropriate reference figure for geophysical studies suggests a relationship between the Antarctic negative gravity anomaly and the great shrinkage of the Antarctic ice cap about 4–5 m.y. ago. The depression of the south polar regions relative to the north polar regions makes the southern hemisphere flatter than the northern hemisphere, and thus the third harmonic (pear shaped) contribution to the earth's figure is produced.

With total ozone sensors on earth-orbitung satellites the ozone distribution over the entire earth may be measured daily. The conclusions from some of the Nimbus III measurements are discussed in this paper. A comparison of time-longitude variations of stratospheric radiance values at 60°S with values of the total ozone indicated that low (high) radiance values correspond very closely with the low (high) total ozone amounts. The speed at which these ozone ‘waves’ progress eastward is greatest in the winter hemisphere. The speed of eastward progression decreases as one approaches the lower latitudes in the winter hemisphere. In the equatorial region the progression of the ozone ‘waves’ appears to be slowly westward. In the Northern Hemisphere the waves progress slowly eastward during summer. The intensity of the ozone ‘waves’ was also observed to change with latitude. These temporal and spatial fluctuations are related mainly to the motion of dynamic tropospheric systems. The extremely tight ozone gradients, which may be seen in the winter hemisphere data, have been shown to be associated with strong baroclinic zones in the lower stratosphere and upper troposphere, which are moving eastward. Assuming uniform zonal velocity we found Rossby wavelengths that varied from 2500 to 3700 km.

The paper contains a study of the day-to-day, seasonal and latitudinal distribution of ozone over the southern hemisphere in comparison with those observed in the northern hemisphere. It has been observed that there is more ozone over the middle latitudes of the southern hemisphere in summer, autumn and early winter, than in the northern hemisphere, whereas the spring maximum values are more or less the same in both hemispheres, suggesting lesser destruction of ozone from spring to autumn in the southern than in the northern hemisphere. The distribution of ozone with height computed from umkehr observations over Aspendale by method B has been compared with that over Tateno in Japan. The results are discussed in relation to the idea of a poleward flow of air from the lower stratosphere and the neighbourhood of the equatorial tropopause in the southern hemisphere. It is concluded that the mean meridional circulation in the lower stratosphere of the southern hemisphere is weaker than, or at any rate only as vigorous as that in the northern hemisphere in spring.

The stratospheric warming and circulation change of January and February 1963 are discussed by means of constant pressure charts, time sections and cross sections. Rawinsonde data are combined with wind data from the Meteorological Rocket Network. The warming initially appeared at 10 mb over southeastern Canada as the contour field began its evolution from a pattern dominated by a circumpolar vortex to a nearly symmetrical bipolar pattern. The subsequent events, such as the northwestward spread of the warm air and destruction of the wintertime polar cyclone, are found to be strikingly similar to those of the 1957 warming. The circulation changes could be traced upward beyond the 55-km level, with an indication that maximum intensities occurred near 45 km. Contour charts of the 10-, 2-, and 0.4-mb surfaces give evidence that the entire atmospheric layer from about 25 km to at least 55 km belongs to the same regime, but with significant interlevel variations in the slope and intensity of the systems.

On the basis of a number of synoptic and synoptical-climatological studies, the following picture of the arctic circulation in summer is presented. A secondary baroclinic zone, distinct from the polar front, develops along the northern shores of Siberia, Alaska and Canada. Cyclones which originate in this zone, and to a lesser extent in the polar frontal zones to the south, frequently invade the central Arctic. The stagnation of these lows near the pole leads to a high frequency of occurrence of low pressure centers and a weak area of low pressure in the mean. There is no evidence for the often assumed semi-permanent anticyclone near the pole. Anticyclones are most frequent in the belt between 70N and 75N, favored locations being central Greenland and the area about the Beaufort Sea. The disturbances of the polar region in summer are shown to be similar to typical middle-latitude storm systems. An example of a typical baroclinic wave development is discussed, a cross section through a high-latitu...

Based on the revised Catalogue of European Large-Scale Weather Patterns (1881–1950) the annual course and the secular variations of the frequency of blocking highs in Europe are treated. Regions of blocking action and those of frequent cold-air centers mutually exclude one another, both corresponding to the orographically influenced asymmetry of the polar vortex.DOI: 10.1111/j.2153-3490.1951.tb00795.x