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Acoustic-gravity waves at ionospheric heights generated by meteorological activity in the troposphere
Šindelářová, Tereza ; Sládek, Ivan (advisor) ; Laštovička, Jan (referee) ; Blanc, Elisabeth (referee)
Acoustic-gravity waves at ionospheric heights generated by meteorological activity in the troposphere Tereza Šindelářová The study deals with observations of ionospheric effects of convective storms in the troposphere, particularly with observations of acoustic-gravity waves in the period range 1-30 min. Convective storms are a source of a broad wave spectrum. The waves propagate partly into the upper atmosphere where they contribute to changes of the structure, dynamics, and composition of the atmosphere. The results of observations in the Czech Republic were compared with the results obtained in the 1960s and 1970s in the central part of the USA. Convective storm develop in both regions under different conditions and thus may act different as far as their influence on the upper atmosphere is considered. Acoustic gravity waves generated by severe tropospheric weather do not carry any label which would help to identify them. One of the ways to distinguish acoustic-gravity waves of tropospheric origin is to recognize waves generated by other sources. Here, a method was proposed that could help to find waves generated by fluctuations the geomagnetic field which is one of the most common sources of ionospheric waves. Ionospheric infrasound generated by convective storms was rarely observed in the Czech...
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Long-term changes of selected stratospheric fields related to circulation and enhancing greenhouse effect
Kozubek, Michal ; Halenka, Tomáš (referee) ; Laštovička, Jan (advisor)
In the present work we study behavior and trends of stratospheric wind in period of 1957-2002. We used reanalyzed daily data from project ERA-40. Results are shown in graphic form for 3 atmospheric levels. In each level we describe trends of wind velocities and directions separate into 2 seasons. We also compare trends of stratospheric wind with other characteristic indicators of atmospheric circulation. One of them is total columnar ozone and the second is mesopause midlatitude winds. Results of analyze halving adjustment of trends in wind directions and velocities for level 100, 50 and 10 hPa, too.
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Impacts of human activity on the upper atmosphere
Laštovička, Jan
Trends in the mesospheric temperature, electron concentration in the lower ionosphere, electron concentration and height of its maximum in the E region, electron concentration in the F1-region maximum, thermospheric neutral density and F-region ion temperature qualitatively agree with consequences of the enhanced greenhouse effect and form a consistent pattern of global change in the upper atmosphere. Three groups of parameters were identified as not-fitting this global pattern, the F2 region ionosphere, mesospheric water vapour, and the mesosphere/lower thermosphere dynamics. The paper reports progress in development of the global pattern of trends with emphasis to these three open problems. There are several other factors contributing to long-term trends, namely the stratospheric ozone depletion, mesospheric water vapour concentration changes, long-term changes of geomagnetic activity and of the Earth’s magnetic field.
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Height profil of geomagnetic storm effects in the ionosphere and atmosphere
Laštovička, Jan
The construction of the height profile of the geomagnetic storm effects in the ionosphere and atmosphere is described. In the F2 region the ionospheric effect is strong and is a response to thermospheric storm. In the lower ionosphere, the strong effect is a direct consequence of a substantial increase of flux of precipitating high energy particles. In the lower atmosphere the origin of strom effects is different.
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