A possible connection of planetary waves (PW) and ionospheric planetary wave type oscillations (PWTO) at midlatitudes is studied by analyzing MetOffice stratospheric reanalysis data and maps of the Total Electron Content. Although the seasonal variability looks similar, the vertical coupling between stratosphere and ionosphere is known to only happen indirectly through processes such as the modulation of gravity waves (GW) by PW. To investigate possible coupling processes, information about GW are retrieved from SABER temperature profiles (30-130 km) by calculating the potential energy (Ep) and generating daily maps of Ep. For the period of time from 2003-07-19 to 2005-07-20 proxies of stationary and travelling PW were calculated to obtain a general picture of PW activity, modulation of GW by PW and activity of PWTO in the ionosphere. The results reveals that mostly PW itself cannot reach lower thermospheric heights, but their signatures propagate upward up to 120 km and above, where they can trigger PWTO. / Ein möglicher Zusammenhang zwischen dem Auftreten planetarer Wellen (PW) und typischer Oszillationen planetarer Wellen (PWTO) der Ionosphäre in mittleren Breiten wird auf der Basis von Analysen stratosphärischer Reanalysen und Karten des Gesamtelektronengehalts untersucht. Obwohl das saisonale Verhalten ähnlich erscheint, kann die Kopplung nur auf indirektem Wege erfolgen, wie z.B. durch die Modulation von Schwerewellen (GW) durch PW. Die für die Analysen notwendigen Informationen über GW können aus Temperaturprofilen (30-130 km), abgeleitet von Satellitenbeobachtungen (z.B. SABER), durch die Bestimmung der potentiellen Energie von GW, gewonnen werden. Zusammengefasst in täglichen Daten (2003-07-19 to 2005-07-20) stellen Proxies stationärer und wandernder PW ein vereinfachtes Bild des Prozesses der Modulation durch PW dar. Die Ergebnisse zeigen, dass sich PW selbst nicht bis in die unteren Thermosphäre ausbreiten können. Jedoch die Signatur, getragen durch GW, könnte auf diesem Wege als PWTO abgebildet werden.

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.

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.

The aim of the study is to compare planetary wave characteristics derived from NCEP/NCAR reanalysis data with Collm wind observations and validate solar activity influence. Vacillations of the SPW 1 amplitude and 5-,10-, 16-day atmospheric modes calculated from NCEP/NCAR reanalysis data and wind variations processed from Collm LF mesopause wind measurements since the 1980s are compared. Similarity of decadal variations of the SPW amplitude vacillations and meridional wind from Collm data is visible for the period 1980-1995. Comparison of the 5-,10-, 16-day atmospheric modes with 2-7, 7-12, 12-30 day period Collm wind variation data do not show clear correspondence for period 1980 - 2005. Correlations between vacillation amplitudes with sunspots numbers and the stratospheric QBO of different phases are presented also. / Die Charakteristik planetarer Wellen, analysiert auf der Basis von NCEP/NCAR-Reanalysen, wird mit Windmessungen von der Außenstelle Collm verglichen, und auf den Einfluss solarer Variationen und der stratosphärischen QBO untersucht. Wir verwenden Schwankungen der stationären planetaren Welle 1, sowie Analysen der 5-, 10- und 16-Tage Welle. Die Variabilität der stationären Welle 1 und diejenige der Windvariationen am Collm stimmt auf der dekadischen Zeitskala überein, jedoch spiegelt sich die Variabilität der Normalmoden (5-, 10-, 16-Tage-Welle) nicht in der entsprechenden Variabilität der Collmer Messdaten wider.

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.

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.