Prior to the space age, meteorologists rarely paid particular attention to the height regions above the tropopause. What was known about the upper atmosphere above about 100 km came essentially from ionospheric and geomagnetic research. The region in between, presently known as the middle atmosphere, was almost terra incognita above the height reachable by balloons. It was space research that allowed for the first time direct access to middle and upper atmospheric heights. About 40 years ago, Sidney Chapman coined a new word 'aeronomy' to describe the study of these two height regions. When asked about the difference between aeronomy and meteorology, he allegedly replied: 'it is the same as between astronomy and astrology' . This mild irony indicates the preferred prejudice of many ionospheric physicists and geomagneticians in those days toward meteorology as a descriptive rather than an exact science, in spite of the presence of such giants as Carl Rossby and Hans Ertel.
A three dimensional, semi-spectral, numerical model is developed for forced, vertically propagating planetary waves and is used to simulate atmospheric diurnal and semi-diurnal thermal tides. The physical model is the same as the one developed by Lindzen (1971) for tides, except that the equation normally used for height is used as the vertical coordinate instead, and an initial value approach is used to obtain the steady state instead of the eigen-value approach used by Lindzen (1971). In the semi-spectral method all the variables are expanded in Fourier series in the E-W direction, and are specified on a mesh of equally spaced grid points in N-S direction. The vertical direction is divided into a number of layers with variable thicknesses. The free modes generated by inperfect initial conditions are dissipated by using a transient Rayleigh friction decaying in time. Reflections of the vertically propagating waves from the top boundary are avoided by absorbing them in a sponge layer, in which Rayleigh friction increase exponentially with height. The model is integrated by using a two step predicted-corrector (leapfrog-trapezoidal) time integration scheme, and is driven by the diurnal and semi-diurnal heating function given by Lindzen (1971). Comparision of the numerical results with the analytical solutions of Lindzen (1971) show that the model reproduced the tidal oscillations very well.
We report here the results from a modeling study with our Numerical Spectral Model (NSM) that extends from the ground into thermosphere. The NSM incorporates Hines Doppler Spread Parameterization for small-scale gravity waves (GWs) and describes the major dynamical features of the atmosphere, including the wave driven equatorial oscillations (QBO and SAO), and the seasonal variations of tides and planetary waves. Accounting solely for the solar migrating tidal excitation sources, the NSM generates through dynamical interactions also non-migrating tides in the mesosphere that have amplitudes comparable to those observed. The model produces the diurnal (and semidiurnal) oscillations of the zonal mean (m = 0), and eastward and westward propagating tides for zonal wave numbers m = 1 to 4. To identify the mechanism of excitation for these tides, a numerical experiment is performed. The NSM is run without the heat source for the zonal-mean circulation and temperature variation, and the amplitudes of the resulting nonmigrating tides are then negligibly small. This leads to the conclusion that the planetary waves, which normally are excited in the NSM by instabilities but are suppressed in this case, generate the nonmigrating tides through nonlinear interactions with the migrating tides.
CAWSES (Climate and Weather of the Sun-Earth System) is the most important scientific program of SCOSTEP (Scientific Committee on Solar-Terrestrial Physics). CAWSES has triggered a scientific priority program within the German Research Foundation for a period of 6 years. Approximately 30 scientific institutes and 120 scientists were involved in Germany with strong links to international partners. The priority program focuses on solar influence on climate, atmospheric coupling processes, and space climatology. This book summarizes the most important results from this program covering some important research topics from the Sun to climate. Solar related processes are studied including the evolution of solar radiation with relevance to climate. Results regarding the influence of the Sun on the terrestrial atmosphere from the troposphere to the thermosphere are presented including stratospheric ozone, mesospheric ice clouds, geomagnetic effects, and their relevance to climate. Several chapters highlight the importance of coupling mechanisms within the atmosphere, covering transport mechanisms of photochemically active species, dynamical processes such as gravity waves, tides, and planetary waves, and feedback mechanisms between the thermal and dynamical structure of the atmosphere. Special attention is paid to climate signals in the middle and upper atmosphere and their significance relative to natural variability.
This thesis reports the investigation of the dynamics and associated phenomena occurring in the ionospheric E- and F-region heights above Arecibo. The observational data was derived with an incoherent scatter radar (ISR) from Arecibo Observatory, Puerto Rico. The thesis focuses primarily on two aspects. One is to study the atmospheric tidal and planetary waves. This is the first time that dual-beam ISR has been used for E- and F-region tidal and planetary wave studies. The vertical structures of the observed tidal and planetary waves are analyzed rigorously. This study is the first to report the existence and possible excitation mechanism of a terdiurnal tide in the F-region at low latitude. The second aspect is to give a more complete explanation of the midnight collapse phenomenon. The F-region electric field, ambipolar diffusion, and tidal components in the meridional wind all play a role in causing the midnight collapse at Arecibo.
Data obtained from six radar stations covering a wide latitude range has been used to determine the global distribution of planetary waves and tides. In the process a number of data analyses techniques were considered for their characterisation.
The SABER radiometer on the TIMED spacecraft scans the earthlimb continuously in ten channels spanning the spectrum from 1.27 to 15 mum. The signature of the diurnal tide in the equatorial region is apparent throughout the mesosphere in TIMED/SABER data, especially in the CO2 15-mum radiance profiles. In addition, layer structures are apparent in a large fraction of the both the radiance profiles and the kinetic temperature profiles derived from them. We present results showing tidal and layer features in the variation with local time and latitude of 15-%mum radiance and temperature. Temperature inversion layers (TILs) are regions of extreme perturbations in the retrieved temperature profile where the temperature increases rapidly over 3-10 km range by tens of degrees K, sometimes approaching increases of 100 K, and are not represented in any existing atmospheric climatologies. Theories that have been proposed connect them with the amplitude and phase of atmospheric tides, as well as with the interactions and dissipation of atmospheric gravity waves and planetary waves. The radiance local maxima, or "knees," are more mysterious. Their occurrence is rather unpredictable and not well explained by models, although it is known that they are due to vibrational excitation of CO2 by atomic oxygen and they may have tidal connections. While they may be associated with strong TILs, the most important class occurring at tangent heights in the lower thermosphere between * 100 and 115 km appear not to be simply related to local inversion layers. SABER data offers the opportunity to do the first global survey of MET TILs, determine their spatial extent and persistence time, and develop a global climatology of their occurrence and properties.
This book is a multi-author treatise on the most outstanding research problems in the field of the aeronomy of the Earth’s atmosphere and ionosphere, encompassing the science covered by Division II of the International Association of Geomagnetism and Aeronomy (IAGA). It contains several review articles and detailed papers by leading scientists in the field. The book is organized in five parts: 1) Mesosphere-Lower Thermosphere Dynamics and Chemistry; 2) Vertical Coupling by Upward Propagating Waves; 3) Ionospheric Electrodynamics and Structuring; 4) Thermosphere- Ionosphere Coupling, Dynamics and Trends and 5) Ionosphere-Thermosphere Disturbances and Modeling. The book consolidates the progress achieved in the field in recent years and it serves as a useful reference for graduate students as well as experienced researchers.
The participation of such diverse scientific and technical disciplines as meteorology, astronomy, atmospheric electricity, ionospheric and magnetospheric physics, electromagnetic wave propagation, and radio techniques in the research of atmospherics means that results are published in scientific papers widely spread throughout the literature. This Handbook collects the latest knowledge on atmospherics and presents it in two volumes. Each chapter is written by an expert in his or her field. Topics include the physics of thunderclouds, thunder, global atmospheric electric currents, biological aspects of sferics, and various space techniques for detecting lightning within our own atmosphere as well as in the atmospheres of other planets. Up-to-date applications and methodology are detailed. Volumes I and II offer a comprehensive discussion that together will serve as an important resource for practitioners, professionals, and students alike.