We consider the amplitudes of coastally trapped Rossby waves in a high-latitude shear flow on a modified ß-plane, where also the effect of the sphericity of the earth (c5-effect) is taken into account. We present a particular analytical solution and also asymptotic and numerical solutions. We find that the asymptotic WKB solutions are accurate compared to the numerical results. We show that the o-effect is most important for shorter waves and leads to an enhanced selection of trapped Rossby wave modes. / Wir betrachten die Amplituden von küstennah gefangenen Rossby-Wellen in einer Scherströmung hoher Breiten. Die Rechnungen werden auf einer modifizierten ß-Ebene durchgeführt, die auch die Spherizität der Erde berücksichtigt (o-Effekt). Wir zeigen eine spezielle analytische Lösung und auch asymptotische und numerische Lösungen. Die asymptotischen WKB-Lösungen erweisen sich als genau, verglichen mit den numerischen Resultaten. Der o-Effekt wirkt sich a stärksten bei den sehr langen und den kurzen Wellen aus und führt zu einer stärkeren Selektion von Moden gefangener Rossby-Wellen.

Thesis (S.M.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2002. / Includes bibliographical references (leaf 119). / The linear and nonlinear Rossby wave solutions are examined in homogeneous square basins on the [beta]-plane both with and without a thin meridional barrier. In the presence of the meridional barrier the basin is almost partitioned into two; only two small gaps of equal width, d, to the north and south of the barrier allow communication between the eastern and western sub-basins. Solutions are forced by a steady periodic wind forcing applied over a meridional strip near the eastern side. Bottom friction is present to allow the solutions to reach equilibrium. The linear solution for the basin containing the barrier is determined analytically and the nonlinear solutions for both basins are found numerically. In the linear solution with the barrier present, particular attention was paid to the resonant solutions. We examined the effects of varying the symmetry of the forcing about the mid-latitude, the frequency of the periodic forcing and the strength of the bottom friction. For each solution we focus on how the no net circulation condition, which is central to any solution in a barrier basin, is satisfied. The nonlinear solutions were studied for both basin configurations. In each case the transition from the weakly nonlinear solution to the turbulent solution was examined, as the forcing frequency and forcing strength were varied. Only integer multiples of the forcing frequency are present in the weakly nonlinear solutions. The turbulent solutions were accompanied by the appearance of many other frequencies whose exact origins are unknown, but are probably the result of instabilities. A hysteresis was found for the turbulent solutions of both the barrier-free and barrier basins. In the weakly nonlinear solutions of the barrier basin it was predicted and confirmed that there is never a steady net flow from sub-basin to sub-basin. It was also shown that with a symmetric forcing all modes oscillating with an odd multiple of the forcing frequency are symmetric and all modes oscillating with even multiples of the forcing frequency are antisymmetric. / by Juli Atherton. / S.M.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Meteorology, 1981. / Microfiche copy available in Archives and Science. / Bibliography: leaves 210-215. / by William Roy Young. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Meteorology, 1979. / Microfiche copy available in Archives and Science. / Vita. / Bibliography: leaves 143-146. / by Charles Augustin Lin. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Meteorology, 1979. / Vita. / Bibliography: leaves 121-122. / by Hsien Wang Ou. / Ph.D.

<p>Several physical mechanisms concerning the impact of Rossby waves on ozone distribution and circulation in the stratosphere and troposphere are studied in the thesis.</p><p>Summertime total ozone variability over Middle Asia and Northern Scandinavia shows similar wave-like behaviour with typical periods of 10-20 days and amplitudes of 20-50 Dobson units. These variations are caused by eastward travelling Rossby waves in the lower stratosphere. The same mechanism plays the primary role in the formation of an intense low ozone episode over Scandinavia in August 2003. A strong anticyclone was formed in the troposphere over Europe as a part of a Rossby wave train. The anticyclone coincides with a displaced Artic pool of low-ozone air in the stratosphere aloft of the anticyclone. A combination of the two above-mentioned processes results in the total ozone minimum over Northern Europe for summer 2003.</p><p>Interannual variability of the atmospheric circulation and total ozone during winter is strongly controlled by the diabatic (Brewer-Dobson) circulation which is driven by upward propagating waves from the troposphere. In the Northern Hemisphere midlatitudes, wintertime total ozone shows antiphase behaviour with the Arctic Oscillation (AO) index on interannual and decadal time-scales. Weaker (stronger) wave activity leads to less (more) northward ozone transport and to a stronger (weaker) AO.</p><p>Rossby wave activity occurs as episodic wave events and this wave forcing is not uniform during winter. The November-December stratospheric eddy heat flux is strongly anticorrelated with the January-February eddy heat flux in the midlatitude stratosphere and troposphere. Weaker upward wave fluxes in early winter lead to stronger upward wave fluxes from the troposphere as well as to a stronger polar night jet during midwinter and vice versa. Hence upward wave activity fluxes in early winter define, to a considerable extent, the subsequent evolution of the midwinter circulation in the stratosphere and troposphere.</p>

Several physical mechanisms concerning the impact of Rossby waves on ozone distribution and circulation in the stratosphere and troposphere are studied in the thesis. Summertime total ozone variability over Middle Asia and Northern Scandinavia shows similar wave-like behaviour with typical periods of 10-20 days and amplitudes of 20-50 Dobson units. These variations are caused by eastward travelling Rossby waves in the lower stratosphere. The same mechanism plays the primary role in the formation of an intense low ozone episode over Scandinavia in August 2003. A strong anticyclone was formed in the troposphere over Europe as a part of a Rossby wave train. The anticyclone coincides with a displaced Artic pool of low-ozone air in the stratosphere aloft of the anticyclone. A combination of the two above-mentioned processes results in the total ozone minimum over Northern Europe for summer 2003. Interannual variability of the atmospheric circulation and total ozone during winter is strongly controlled by the diabatic (Brewer-Dobson) circulation which is driven by upward propagating waves from the troposphere. In the Northern Hemisphere midlatitudes, wintertime total ozone shows antiphase behaviour with the Arctic Oscillation (AO) index on interannual and decadal time-scales. Weaker (stronger) wave activity leads to less (more) northward ozone transport and to a stronger (weaker) AO. Rossby wave activity occurs as episodic wave events and this wave forcing is not uniform during winter. The November-December stratospheric eddy heat flux is strongly anticorrelated with the January-February eddy heat flux in the midlatitude stratosphere and troposphere. Weaker upward wave fluxes in early winter lead to stronger upward wave fluxes from the troposphere as well as to a stronger polar night jet during midwinter and vice versa. Hence upward wave activity fluxes in early winter define, to a considerable extent, the subsequent evolution of the midwinter circulation in the stratosphere and troposphere.

Decadal variations in climate are important, because the magnitude of sustained decadal change is often much larger than the often discussed background trends. Climate variability at interannual and longer periods is most often discussed in the context of climate modes defined by sea level pressure (SLP) and sea surface temperature (SST) patterns. However, SLP and SST are not capable descriptors of ocean dynamics. The approximately two decades of global sea surface height (SSH) measurements from satellite altimetry reveal substantial low-frequency redistributions of heat and salt in the ocean, which may or may not be related to defined climate modes. In addition, coastal sea level responds directly to synoptic variability in the atmosphere, providing long records of weather events in coastal areas. The unifying idea in the following analyses is the value and versatility of SSH from altimetry and sea level from tide gauges for investigations of decadal climate variability. Three applications of SSH and coastal sea level to the study of decadal change demonstrate the merits of using sea level for investigations of oceanic and atmospheric, episodic and continuous processes. The analyses concern a multidecadal change in storminess along the coast of the Southeast U.S., basin-scale coherent sea level variations in the western boundary of the North Atlantic, and the low-frequency response of the ocean to atmospheric forcing in the Northeast Pacific.

Wavelike spiral asymmetries are an intriguing aspect of Tropical Cyclone dynamics. Previous work hypothesized that some of them are Vortex Rossby Waves propagating on the radial gradient of mean–flow relative vorticity. In the Intermittently Forced Vortex Rossby Wave theory, intermittent convection near the eyewall wind maximum excites them so that they propagate wave energy outward and converge angular momentum inward. The waves’ energy is absorbed as the perturbation vorticity becomes filamented near the outer critical radii where their Doppler–shifted frequencies and radial group velocities approaches zero. This process may initiate outer wind maxima by weakening the mean–flow just inward from the critical radius. The waves are confined to a relatively narrow annular waveguide because of their slow tangential phase velocity and the narrow interval between the Rossby wave cut–off frequency, where the radial wavenumber is locally zero, and the zero frequency, where it is locally infinite.

The large-scale, mid-latitude circulation in the upper troposphere is dominated by Rossby waves. The jet stream flows along the wave structure and surface cyclones can be found ahead of the troughs of the waves, propagating eastward. This propagation is here estimated as the zonal phase speed which is quantified using spectral analysis, producing a unique, global daily value for each day of the winter season (DJF) between 1979 and 2019. From this data set phase speed events are defined as periods of more than four consecutive days of the top or bottom 5\% phase speed values, resulting in 15 low phase speed events and 22 high phase speed events. During events of low phase speed the 2m temperature is higher than the climatology at high latitudes and lower over Europe and Siberia. Zonal wind speed at 10m and 250hPa is also found to be lower than the climatology over both the Pacific and Atlantic storm track. Furthermore, low phase speed events are found to be occurring when blocking is present on either one or both storm tracks. During high phase speed events there is an overall increase in zonal wind speed both at 10m and 250hPa over both storm tracks as well as total magnitude of wind over western Europe. These findings suggest a link of high phase speed events to windstorms over Europe. A subjective classification indicates that at the onset of high phase speed events blocking is found mainly in two regions, one at high latitudes outside the Siberian coast and one at low latitudes outside the coast of Japan, suggesting enhanced temperature gradients at the entrance of the Pacific could cause these events. / Den storskaliga cirkulationen över mellanbredderna i den övre troposfären domineras av Rossbyvågor. Dessa är en vågstruktur som formas från Jordens rotation och vorticitet och associeras med det starka flödet från jetströmmen som återfinns längs vågstrukturen. På grund av vorticiteten uppstår cykloner framför vågornas tråg och hela systemet propagerar österut. Propageringen uppskattas här som fashastighet och kvantifieras med spektralanalys, en metod där interpolering från ett spektrum används snarare än teoretiska beräkningar. Detta producerar ett unikt och globalt dygnsmedel under vintersäsongen (December, Januari, Februari) mellan 1979 och 2019, där vintern väljs på grund av den stora variabiliteten i fashastighet som observeras då. Från denna data definieras fashastighetsevent som fyra eller fler dagar i sträck med de högsta eller lägsta 5 \%-värdena, vilket resulterar i 15 event med låg fasthastighet och 22 event med hög fashastighet. Under eventen med låg fashastighet är temperaturen vid 2m högre än klimatologin vid höga breddgrader och lägre över Europa och Sibirien. Den zonala vinden vid 10m och 250hPa är också lägre än klimatologin över både lågtrycksbanan över Stilla havet och Atlanten. Vidare så fann vi att låg fashastighet uppstår i samband med atmosfärisk blockering över en eller båda lågtrycksbanor. Under event med hög fashastighet observeras en ökning i zonal vindstyrka både vid 10m och 250hPa över båda lågtrycksbanorna samt en ökad styrka i den totala magnituden av vinden över västra Europa. Dessa fynd tyder på en länk mellan hög fashastighet och vindstormar i Europa. Vid starten av event med hög fashastighet återfinns atmosfärisk blockering främst i två regioner, en vid höga breddgrader utanför den Sibiriska kusten och en vid låga breddgrader utanför Japans kust, vilket tyder på att ökade temperaturgradienter vid början av lågtrycksbanan över Stilla havet kan orsaka dessa event.