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Climatology of cyclones, anticyclones and storm tracks: This paper has the finality of describe climatology of extratropical cyclones, anticyclones and storm tracks for the NH and SH. There is a long history of studies on the characteristics of synoptic systems, beginning with classical work on mid-latitude cyclones. For the SH, analyses of pressure data provide extensive statistics of the climatology of synoptic systems.

For the NH cyclones, the principal findings of the analysis are as follows: Cyclones, anticyclones, storm tracks, climatology. Ciclones, anticiclones, storm tracks, climatologia. It has been appreciated for a long time that extratropical cyclones are associated with weather and climate in the globe. Such information is an essential adjunct to the interpretation of mean pressure or height fields Klein, The delimitation of anticyclones centers is normally ambiguous because of slack pressure gradients and tendency for weak maxima that may shift irregularly over time, located within the highest closed isobar.

An alternative procedure, proposed by Sinclairis to calculate geostrophic relative vorticity, although this is better suited to cyclones than anticyclones, as the latter have light winds and a wide separation between the loci of pressure maxima and relative anticyclones vorticity maxima. The intense anticyclones occur poleward of both the ridge and the maximum zone of system density.

The poleward side of the STR is affected by frequent and intense lows, whereas the equatorward side generally has undisturbed flow. Anticyclones are most numerous over the eastern subtropical oceans, with fewer over the southern land areas excluding Antarctica. The anticyclones generally move eastward and somewhat equatorward, decaying near the oceanic centers of the time-mean anticyclones. However, when centers are computed by identifying local minima from mb level geostrophic vorticity, a different picture emerges.

This analysis thereby takes account of mobile vorticity centers in middle latitudes. There is a secondary maximum in winter-spring associated with the subtropical of South America and in the southern Indian Ocean in winter. Extension of the vorticity analysis to cyclogenesis shows that cyclones typically form in preferred areas in middle latitudes – near the jetstream baroclinic zones and to the east of the southern Andes year-round, as well as off the east coasts of Australia and South America in winter.

Systems forming over the oceans intensify over strong gradients of sea surface temperature. More recently Lim and Simmonds found great concentration of explosive cyclones in SH has a close association with that of strong baroclinicity.

For the NH, twenty year climatology of extratropical cyclones based on more consistent data than the earlier studies is available. The principal findings of the analysis are as follows: The other main anticivlones is from the western Pacific to the western Aleutian Islands, with a subsidiary are over China. In mid-latitudes, the frequency of lows decreases at mb, with increases at mb, except in winter. Agee used three previous analyses of cyclones cilcones anticyclones frequency to examine trends in relation to intervals of warming and cooling in the NH.

Based on the works of Parker et al. The spatial distribution of systems identified by Serreze et al.

In the summer half year this tendency is almost absent. In winter the rate of cyclones deepening and the frequency of deepening events peak anticuclones the area of the Icelandic cickones, southwest of Iceland, with a separate maximum in the Norwegian Sea Serreze et al.

Cyclogenesis is common in these areas, as well as in northern Baffin Bay. Deepening rates are up to The combined effects of ice-edge baroclinicity, orographic forcing, and rapid boundary layer modification in off-ice airflows are probably involved. Additionally, these same locations show high frequencies active one with alternating regimes. Anticyclogenesis has received less attention except for that occurring in polar air Curry, and blocking events.

Cases were defined by a twenty-four-hour mean sea level MSL pressure change averaging 2. For the western hemisphere anticyclogenesis is concentrated over Alaska – western Canada, associated with cold air outbreaks, and over covered areas re-intensify.

These highs are usually shallow mobile systems. In summer a similar process operates farther north, over southern Alberta. The cciclones is initially confined to the layer below mb, although vertical motion associated ciclonee the anticyclogenesis extends through the troposphere.


The system first moves southward towards the Gulf coast and then recovers northeastward. In the first stages, upper-level vorticity advection and cold air advection lead to subsidence downstream over the anticyclones. The anticyclone moves southward towards the region of maximum anticicoones, forced by the advection. It is supported to the west by a jet streak maintaining a thermal gradient. In the later stages, warm advection in the lower middle troposphere west of the anticyclones forces an upper-level ridge.

More recently Pezza and Ambrizzi finding decrease number of extratropical cyclones and anticyclones in the SH, betweenwith great variability interannual The same other find increase of cyclones with central pressure below hPa, as well as, anticyclones above hPa.

The al convention Lagrangian approach to defining storm tracks involves tracing the movement of low pressure centers. Such manual investigations of cyclones tracks in midlatitudes began when synoptic weather maps were systematically prepared in the s and s. Early studies were performed by E. Loomis for North America, Mohn for Europe.


Loomis was the first to assemble information on cyclones paths over the northern hemisphere, but a comprehensive analysis was possible only in the mid-twentieth century Petterssen, ; Klein, Petterssen drew attention to the importance of the zones where there is a high rate of alternation between high and low pressure centers, which he termed pressure ducts.

A Lagrangian climatology of North Atlantic storm tracks illustrates a further novel methodology Blender et al.

Cluster analysis of the track data defined three groups of storm that are persistent for at least three days – quasi-stationary representing 56 percents of the totalnortheastward moving 27 percent and eastward moving 16 percents.

Analysis of the zonal xmeridional y and total displacement over time t for each group demonstrates that mean-squared displacements of the cyclones follow a power law scaling: The persistence of a northeastward storm track regime averages about five days three to eight day rangewhile the zonal regime has a slightly shorter duration. In the SH, in contrast to the NH, storm track are virtually circum-global, with little seasonal variability Sinclair,Gulev et al.

The maxima shows are in higher latitudes than in earlier studies by the same author, where the grid spacing favoured detection at lower latitudes. A weakness of such analyses is the fact that changes in the intensity of the system and its rate of movement have to be taken into account independently.

An alternative frame work for the diagnostic analysis of the atmospheric circulation uses the analysis of the variance of the geopotential height field.

Ciclones y Anticiclones by sgefgbf hntgjhr on Prezi

These are anticiclonex to propagate along zonally oriented wave guides. These are close overall similarities between the two anticiclomes of patterns. Differences between them are caused by zonal variations in the climatological mean flow, which may displace the cyclones anticyclones relative to the corresponding anomaly center Wallace et al. There is no pronounced equatorward displacement of the storm tracks in winter, as occurs in the NH and the occurrence of maximum mid-latitude meridional temperature gradients during austral summer determines the degree of storm tracks activity and the anticivlones to zonal symmetry.

The observed location of the primary storm track just downstream and poleward of the polar jetstream maxima Trenberth, is accounted for by linear baroclinic theory for the observed basic state of the atmosphere in the SH, according to Frederiksen The relation between the mean jetstream, the storm tracks, and the associated high frequency eddy statistics for the zonally symmetric circulation in the SH cicllnes illustrated schematically in Trenberth Maximum height variance z’ 2indicating a high rate alternation, is located along the storm track, whereas perturbations of the vorticity z ‘ 2 are greatest just equatoward of the track as a result of the variation of the Coriolis parameter and consistent with the geostrophic anticiclomes.

Accordingly, perturbations of the meridional wind v’ are displaced correspondingly, but zonal wind perturbations u’ have maxima north and south of the storm track. This generates momentum convergence from eddies into the storm track. Anticiclonees perturbations of temperature, T’, are greatest at low levels and are highly correlated with the east-west variations in -v’. Also, maximum perturbations of moisture, q’ and vertical velocity, w ‘, are closely related and are located in lower latitudes in anticlclones with the patterns of v’ and T’.

Howere, it is the combined effect of the height anomalies in all frequency bands make up the observed circulation pattern at a anticiclojes time. As pointed out by Trenberththe cyclonic vorticity advection associated bad weather arise from the advent to a negative height anomaly or the departure of a positive height anomaly. The formation and maintenance of storm tracks merits explanation. There are two basic hypotheses concerning the development of storm tracks.


One considers that the meridional temperature gradients formed by land-sea contrasts induce planetary wave structures through antkciclones and orographic effects that are modified by transient influences. The second idea involves a self-organizing mechanism whereby eddies feed back onto the time mean flow.

They use a two level hemispheric quasi-geostrophic model, linearized about the observed mean flow for and mb winds,and forced by Gaussian white noise.

The synoptic eddy covariance is linked with the spatial structure of the background flow and with the covariance of the stochastic forcing by a fluctuation dissipation relationship; this relationship implies that the tendency of eddies to decay is balanced by forcing. The model reproduces most major features of the climatological winter storm tracks over North Pacific and North Atlantic as well as some aspects of their seasonal cycles and interannual variability.

They identify two competing processes that are associated with the antociclones of a local baroclinicity maximum and a horizontal deformation minimum. If the equilibrium state comprises a zonally symmetric temperature field and a barotropic stationary wave, the storm track is just downstream of a minimum in horizontal deformation in the upper jet entrance zone. However, as zonal variations in baroclinicity increase, the storm track is displaced to the jet exit region just downstream of a baroclinicity maximum.

With flows intermediate between these two cases, there are storm ciclonnes maxima in both the jet entrance and exit zones. Midlatitude cyclones, at least off east coast of Asia and North America, develop and intensify primarily through baroclinic instability associated with diabatic heating. Maxima of s BI exceeding 0.

Anticiclone do Atlântico Sul

The horizontal eddy transport of heat in extratropical storms act to reduce the baroclinicity and therefore storm tracks might be expected to shift in time and space as systems move through an area, yet this is not observed because vorticity fluxes help to offset the effect. Rather, the storm tracks tend to be self maintaining as a result of the diabatic heating patterns anticiclons caused by the storm tracks.

Orlanski confirms the increase in the barotropic component of the zonal jet due to the second term of the E flux. Nevertheless, the low level winds that arise as a result of cyclones passages set up wind stresses that help to strengthen the Gulf Stream and Kuroshio currents, thereby in turn providing the initial diabatic heating and baroclinicity for the atmosphere.

Climatological storm tracks are commonly identified by maxima in the variance of geopotential height. Large amplitude, high frequency eddies occur preferentially downstream of the major stationary wave troughs at mb, giving rise to stationary storm tracks Blackmon et al.

However, the planetary scale waves oscillate in position, Therefore it is important to understand how travelling storm ckclones may more in association with these planetary scale wave. Low frequency seven to ninety days and high frequency less than seven days components of geopotential height can be separated by taking Fourier components of gridded height values in the frequency domains, for example.

The low frequency variability is about twice that of the high frequency component and represents regions of recurring high amplitude anomalies in the central North Atlantic, Gulf of Alaska, western Siberia, and northern Hudson Bay.

The high frequency component has a background value of about anticicpones gpm and maxima of 70 – 80 gpm in elongated zones resembling anticiclonse storm tracks of the North Atlantic and Anticiclonee Pacific. The high ciclonws transient eddies reinforce the barotropic component of the stationary waves, i.

Model studies anticiclonse the idea that storm track anomalies are driven by, and through, feedback effects and may also modify large-scale, low frequency circulation anomalies.

Using a series of Global Climate Model GCM integrations, Branstator shows that the distribution of storms can be altered by the barotropic component of the low frequency perturbations through the steering of synoptic systems by the mean winds.