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This thesis provides highlights of the atmospheric research conducted during the program of studies 2003-07. The theme is variability of the winds at mesospheric heights (60-100 km) due to Planetary Waves (PW, 2-30 days) over middle and high latitudes. Considerable energy and momentum are transported by atmospheric waves, and their global characteristics are required to understand many phenomena and explain coupling processes within the atmosphere. The vertical propagation of PW from the upper troposphere to the mesosphere is investigated by applying the Morlet wavelet and wave number analysis to the MetO (United Kingdom Meteorological Office) stratospheric assimilated fields, TOMS total (column) ozone, and Medium Frequency (MFR) and Meteor Wind (MWR) radar measurements. The results show that large-scale eastward propagating PW dominate at tropopause and low stratospheric heights, while westward PW become comparable or even stronger in the upper stratosphere and above during months other than summer. There are also strong seasonal dependences of the PW activity in each of the stratospheric and mesospheric regions, which are attributed, at least partially, to the influence of the background wind on PW propagation. Longitudinal variations in PW activity are explained by longitudinal variations in these winds.<p>During summer (westward zonal winds) PW activity is reduced in the stratosphere and only relatively fast westward propagating PW, such as quasi 2-day wave (Q2DW), are able to reach mesospheric heights from below. The results obtained using 14 years of MFR data at Saskatoon provide a unique climatology (70-100 km) of this wave: in addition to summer activity the Q2DW is also present at low mesospheric heights in winter, especially when the eastward winds are weak; there are significant interannual variations in Q2DW activity in both seasons. Strong latitudinal and longitudinal differences in Q2DW occurrence and amplitude are shown from the comparisons of wind data at several stations.<p>During winter, when zonal winds are eastward, the PW coupling between stratosphere and mesosphere is stronger than during other seasons. Detailed data analysis has been performed for the Arctic winter of 2004/05, for which the stratospheric state is described using conventional zonal mean parameters as well as the newer Q-diagnostic. Spectral analyses for this winter show relatively weak PW activity at stratospheric and mesospheric heights and strong latitudinal and longitudinal differences of mean winds and PW characteristics consistent with the form and location of the polar vortex. <p>In addition to the vertical coupling it has also been shown that weaker horizontal inter-hemispheric coupling occurs during equinoctial months, when eastward winds dominate globally. It is demonstrated that with favorable conditions, planetary waves with 10, 16 and 25 day periods penetrate to the opposite hemisphere.

This thesis provides highlights of the atmospheric research conducted during the program of studies 2003-07. The theme is variability of the winds at mesospheric heights (60-100 km) due to Planetary Waves (PW, 2-30 days) over middle and high latitudes. Considerable energy and momentum are transported by atmospheric waves, and their global characteristics are required to understand many phenomena and explain coupling processes within the atmosphere. The vertical propagation of PW from the upper troposphere to the mesosphere is investigated by applying the Morlet wavelet and wave number analysis to the MetO (United Kingdom Meteorological Office) stratospheric assimilated fields, TOMS total (column) ozone, and Medium Frequency (MFR) and Meteor Wind (MWR) radar measurements. The results show that large-scale eastward propagating PW dominate at tropopause and low stratospheric heights, while westward PW become comparable or even stronger in the upper stratosphere and above during months other than summer. There are also strong seasonal dependences of the PW activity in each of the stratospheric and mesospheric regions, which are attributed, at least partially, to the influence of the background wind on PW propagation. Longitudinal variations in PW activity are explained by longitudinal variations in these winds.<p>During summer (westward zonal winds) PW activity is reduced in the stratosphere and only relatively fast westward propagating PW, such as quasi 2-day wave (Q2DW), are able to reach mesospheric heights from below. The results obtained using 14 years of MFR data at Saskatoon provide a unique climatology (70-100 km) of this wave: in addition to summer activity the Q2DW is also present at low mesospheric heights in winter, especially when the eastward winds are weak; there are significant interannual variations in Q2DW activity in both seasons. Strong latitudinal and longitudinal differences in Q2DW occurrence and amplitude are shown from the comparisons of wind data at several stations.<p>During winter, when zonal winds are eastward, the PW coupling between stratosphere and mesosphere is stronger than during other seasons. Detailed data analysis has been performed for the Arctic winter of 2004/05, for which the stratospheric state is described using conventional zonal mean parameters as well as the newer Q-diagnostic. Spectral analyses for this winter show relatively weak PW activity at stratospheric and mesospheric heights and strong latitudinal and longitudinal differences of mean winds and PW characteristics consistent with the form and location of the polar vortex. <p>In addition to the vertical coupling it has also been shown that weaker horizontal inter-hemispheric coupling occurs during equinoctial months, when eastward winds dominate globally. It is demonstrated that with favorable conditions, planetary waves with 10, 16 and 25 day periods penetrate to the opposite hemisphere.

Temperature measurements from the HIRDLS instrument on NASA's Aura satellite are analysed for the purposes of detecting and studying internal gravity waves in the terrestrial stratosphere. A detailed description of the methodology used to obtain these data is given, including details of the instrument correction processes used to compensate for errors introduced by a blockage in the instrument optics. A short precis of the relevant theoretical considerations related to atmospheric gravity waves is then outlined. The thesis then discusses the use of the Stockwell (time-frequency) Transform for the detection of gravity waves in HIRDLS data, together with a detailed analysis of the limitations of this method, and the results obtained from this analysis are analysed by comparison to other instruments and climatology. It is concluded that the Stockwell Transform is an appropriate method for the analysis of the HIRDLS dataset, and that the results obtained are robust. We apply these results to analyse stratospheric gravity wave activity during the 2005/06 Arctic sudden stratospheric warming. By comparing the magnitude and form of the gravity wave results to local wind data obtained from ECMWF operational analyses, we conclude that a heavily deformed stratopause observed during this period by other instruments was most probably due to wind-based filtering of the gravity wave spectrum during this period.

This thesis presents observations of the 2-day planetary wave in the stratosphere, mesosphere and lower thermosphere. These observations were made using two ground-based meteor radars at polar latitudes and the satellite-borne microwave limb sounder (MLS) on the NASA Aura satellite. There have been relatively few observations of the 2-day wave at polar latitudes made using ground-based radars. This is particularly so in the Antarctic. Measurements of summertime and wintertime polar 2-day waves in the mesosphere and lower thermosphere (MLT) region were made using identical meteor radars at the conjugate geographical latitudes of Rothera (68!S, 68!W) in the Antarctic and Esrange (68!N, 21!E) in Arctic Sweden. This allows accurate quantification of the differences in the nature and seasonal variability of the 2day wave between the two polar regions. A clear seasonal variability is evident with the maximum amplitudes occurring during the summer months in both hemispheres. However, significant differences are found in the behaviour of the summertime wave between the two polar regions. In particular, wave activity is shorter lived but of larger amplitude in the Antarctic. These differences are suggested to be partly due to the different background winds of the two polar regions and possible differences in the component zonal wavenumbers in the northern and southern hemispheres. These radar studies have excellent spatial, height and time resolution but cannot resolve the component zonal wavenumbers of the 2-day wave. Therefore, Earth Observing System (EOS) Aura Microwave Limb Sounder (MLS) measurements of atmospheric temperature were used to investigate the climatology and interhemispheric differences of the different zonal wavenumbers (westward propagating zonal wavenumbers 2, 3 and 4) that compose the 2-day wave “complex”. This study demonstrates that the wave is dominated by different wavenumbers in the northern and southern hemisphere and that some of the interhemispheric differences observed in ground-based studies can be explained by the seasonal variability of these different zonal wavenumbers. These satellite studies led to participation in a multi-technique international collaboration to study the short-term variability of the summertime 2-day wave. Observations made in the northern hemisphere at mid-latitudes revealed that there are typically three peaks of enhanced 2-day wave amplitude during the summer, probably originating from a combination of baroclinic instability and critical wind speed.

Aus täglichen Analysen des sommerlichen zonalen Grundwindes im Mesopausenbereich, der am Observatorium Collm der Universität Leipzig gemessen wurde, werden niederfrequente Variationen im Zeitbereich planetarer Wellen (10 - 20 Tage) bestimmt. Obwohl die direkte Ausbreitung derartiger Wellen durch die stratosphärischen und mesosphärischen Ostwinde verhindert wird, werden in manchen Jahren trotzdem Oszillationen gemessen, die mit planetaren Wellen im Zusammenhang stehen können. Dies unterstützt die Theorie, daß sich planetare Wellen von der Winterhalbkugel entlang der Zonen schwachen Windes bis in die Mesopausenregion mittlerer und polarer Breiten ausbreiten. Betrachtet man die interanuelle Variabilität dieser Wellen, fällt eine Abhängigkeit von der äquatorialen quasi 2-jährigen Schwingung (QBO) auf, wobei während der Ostphase der QBO die Wellenaktivität gering ist, während sie in der Westphase der QBO stärker sein kann. Der Einfluß der QBO auf die sommerliche Wellenaktivität wird vom 11-jährigen Sonnenfleckenzyklus moduliert, wobei während des solaren Maximums stärkere Aktivität zu verzeichnen ist. / From daily estimates of the summer mesopause region zonal prevailing wind measured at the Collm Observatory of the University of Leipzig long-term variations in the period range of planetary waves (10-20 days) are detected. Although the direct propagation of these waves from lower layers into the mesosphere is not possible because of the wave filtering in the summer stratospheric and mesospheric easterlies, in some years oscillations are found that can be connected with planetary waves, supporting the theory of the propagation of these waves from the equatorial region to the midlatitude and polar upper mesosphere along the zero wind line. The interannual variability of these waves shows a dependence on the equatorial quasi-biennial oscillation (QBO), so that in general during the east phase of the QBO the planetary wave activity is small, while during the QBO west phase it can be larger. The influence of the QBO on the planetary wave activity is modulated by the I I-year solar cycle, so that the strongest signal is found during solar maximum.

This thesis presents observations of the dynamical features of the stratosphere, mesosphere and lower thermosphere. These are made from various observational techniques and model comparisons. A focus of the work is the two-day wave at high latitudes in the MLT region. This has revealed significant wave amplitudes in both summer and winter. However, these waves are shown to have very different origins. Using satellite data, the summertime wave is found to be the classic quasi-two-day wave which maximises at mid-latitudes in the MLT region. The wintertime wave is found to be a mesospheric manifestation of an eastward-propagating wave originating in the stratosphere and likely generated by barotropic and baroclinic instabilities in the polar night jet. The horizontal winds from Meteor and MF radars have been used to measure and produce climatologies of the Lunar M2 tide at Esrange in the Arctic (68°N), Rothera and Davis in the Antarctic (68°S), Castle Eaton at mid-latitude (52°N) and Ascension Island at Equatorial latitudes (8°S). These observations present the longest period of lunar semi-diurnal tidal observations in the MLT region to date, with a 16-year dataset from the UK meteor radar. Comparisons with the Vial and Forbes (1994) lunar tidal model are also made which reveal generally good agreement. Non-migrating lunar tides have been investigated. This uses lunar tidal results from equatorial stations, including the Ascension Island (8°S) meteor radar. Also lunar tidal results from the Rothera meteor wind radar (68°S, 68°W) and the Davis MF radar (68°S, 78°E) are considered. Both of these stations are on the edge of the Antarctic continent. It is demonstrated that there are often consistent tidal phase offsets between similar latitude stations. This suggests that non-migrating modes are likely to be present in the lunar semi-diurnal tidal structure and have significant amplitudes.

The ionosphere-thermosphere can be considered to a certain degree as a system, which is externally-driven by the extreme-ultraviolet solar radiation. The main components in the regular variation are connected to the solar cycle, solar rotation and the diurnal cycle. However, anomalies and periodicities of several days, which cannot be related to changes in the solar activity at all times, were detected in ionospheric parameters. It is assumed that the total variation in the ionosphere is partly forced by waves coming from below. This thesis provides a clearer picture of the seasonal changes of wave phenomena observed in the ionosphere and its possible relation to lower atmospheric structures. Since such global disturbances in the middle atmosphere are termed as planetary waves (PW), such features in the ionosphere are declared as planetary wave type oscillations (PWTO), although a direct connection is excluded.Northern hemispheric maps of the Total Electron Content (TEC) derived from GPS-signals that are currently used for monitoring the ionospheric F-region in relation to space weather provide a basis for investigating PWTO applying space-time analysis methods to separate stationary and traveling wave components from the data. Compared to analyses of PW obtained by regular stratospheric reanalyses the seasonal behavior and possible coexisting wave activities during the considered period of time (2002-2008) are presented. Such a climatological consideration has revealed that recurring events in the course of the solar cycle are rare, but it seems that the westward propagating quasi 16-day wave with zonal wavenumber 1, analysed from stratospheric MetO reanalyses, and the ionosphere are indirectly coupled. Generally, the correspondence of other components are restricted around the solar maximum 2002-2005. There are some suggestions, how the middle and upper atmosphere are connected by PW. Sounding of the middle atmosphere by remote sensing techniques from satellites (e.g. SABER on TIMED) deliver a suitable basis to investigate the coupling by the modulation of gravity waves (GW). By calculating the potential energy for a certain wave spectrum, characterized by vertical wavelength shorter than 6 km, and determining proxies of traveling waves permits to investigate a possible mechanism. The results reveal that GW partly penetrate the lower thermosphere carrying a modulation by PW. In some cases, especially during the first three winter, near solar maximum, stratospheric PW show a good correlation to indirect signals in the lower thermosphere and to PWTO in the ionospheric F-region near 300 km.

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-11-08T11:09:05Z No. of bitstreams: 1 ROBSON BATISTA DE SOUSA - DISSERTAÇÃO (PPGFísica) 2012.pdf: 22073508 bytes, checksum: 07991b4cdb0e710b093893fcc69708ec (MD5) / Made available in DSpace on 2018-11-08T11:09:05Z (GMT). No. of bitstreams: 1 ROBSON BATISTA DE SOUSA - DISSERTAÇÃO (PPGFísica) 2012.pdf: 22073508 bytes, checksum: 07991b4cdb0e710b093893fcc69708ec (MD5) Previous issue date: 2012-05-16 / Medidas de ventos e de temperatura obtidas por radar meteórico (SKiYMET) em São João do Cariri-PB (7, 4◦S) e em Cachoeira Paulista-SP (22, 7◦S) foram utilizadas para investigar a oscilação de 6, 5 dias na região mesosférica. Os resultados das análises dos dados de vento e de temperatura revelaram a presença da onda de 6, 5 dias em ambas as localidades, em que as atividades máximas ocorreram durante os meses de primavera austral. Os valores das amplitudes e dos comprimentos de onda vertical, determinados a partir das medidas de ventos, para São João do Cariri, foram superiores aos de Cachoeira Paulista. Em ambas as localidades foram verificadas uma modulação da onda de 6, 5 dias pela Oscilação Semi-Anual (SAO) na temperatura mesosférica. De um modo geral, tanto em São João do Cariri, quanto em Cachoeira Paulista, as atividades máximas da onda de 6, 5 dias foram registradas durante a fase para oeste da Oscilação Quase-Bienal (QBO). Entretanto, o conjunto de dados utilizados neste trabalho não são suficientes para estabelecer uma relação conclusiva dos efeitos da QBO na atividade da onda de 6, 5 dias. Em geral, os parâmetros físicos da onda de 6, 5 dias obtidos neste trabalho são compatíveis com os reportados em outras localidades. / Measurements of wind and temperature obtained from SKiYMET meteor radars at São João do Cariri-PB (7.4◦S) and Cachoeira Paulista (22.7◦S) were used to investigate the 6.5-day oscillations in the mesospheric region. The wind and temperature data analysis results revealed the presence of the 6.5-day waves at both sites, in which the maximum activities have occurred during the austral spring months. The amplitudes and vertical wavelength values, estimated from the wind vertical structure phase delay, for São João do Cariri were longer than for Cachoeira Paulista. For the first time, has been observed for both sites that the 6.5-day wave activities display a semi-annual modulation (SAO) in the meteor temperature. In general, the maximum activities of the 6.5-day waves took place during westward QBO wind phase. However, the data series used in this study are not enough to establish a reliable QBO modulation of the 6.5-day wave. In general, the 6.5-day wave parameters obtained in this work are consistent with those reported for other sites.

Submitted by Jean Medeiros (jeanletras@uepb.edu.br) on 2017-08-11T13:18:16Z No. of bitstreams: 1 PDF - Jaruseyk Batista Silva Fidelis.pdf: 30809896 bytes, checksum: b1811b7e03cf7247fe3d69350743897c (MD5) / Made available in DSpace on 2017-08-11T13:18:16Z (GMT). No. of bitstreams: 1 PDF - Jaruseyk Batista Silva Fidelis.pdf: 30809896 bytes, checksum: b1811b7e03cf7247fe3d69350743897c (MD5) Previous issue date: 2017-06-26 / In this study, VLF (Very Low Frequency) signal amplitude data obtained through the o o receiving station located at Punta Lobos (12,5 S 76,8 W), belonging to the SAVNET net- work (South America VLF Network), were used to characterize planetary wave signatures in the Ionosphere D region during the summer seasons of the years 2008 and 2009. The VLF signal data were submitted to filters seeking to eliminate different oscillations of planetary waves, then through spectral analysis in wavelet used to identify the presence of periodic planetary oscillations. The results of the analyzes of VLF signal amplitude data at Punta Lobos revealed the presence of planetary scale oscillations on several occasions during the period considered. Among the identified oscillations, the periodicity of 2, 6, 8, and 16 days were interpreted as a result of planetary wave actions, so that they exhibited higher intensity after the summer solstices. In general, the characteristics of the VLF signal obtained through the wavelet analysis showed consistency with those obtained in other locations. / Nesta pesquisa, dados de amplitude do sinal de VLF (Very Low Frequency) obtidas através o o da estação receptora localizada em Punta Lobos (12,5 S 76,8 W), pertencente a rede SAVNET (South America VLF Network), foram utilizados para caracterizar assinaturas de ondas planetárias na região D da Ionosfera durante as estações de verão dos anos de 2008 e 2009. Os dados do sinal de VLF foram submetidos a filtros buscando eliminar oscilações diferentes de ondas planetárias, em seguida através de análise espectral em wavelet buscou- se identificar a presença de oscilações periódicas de escala planetária. Os resultados das análises dos dados de amplitude do sinal de VLF em Punta Lobos revelaram a presença de oscilações de escala planetária em várias ocasiões durante o período considerado. Dentre as oscilações identificadas, as periodicidades de 2, 6,5, 8 e 16 dias foram interpretadas como resultado de ações de ondas planetárias, de forma que exibiram maior intensidade após os solstícios de verão. Em geral, as características do sinal de VLF obtidos através das análises em wavelet mostraram consistência com aqueles obtidos em outras localidades.