Large Scale Winter Time Disturbances in Meteor Winds over Central and Eastern Europe

Daily zonal wind data of the four pre-MAP-winters 1978/79 to 1981/82 obtained over Central Europe and Eastern Europe by the radar meteor method were studied. Available temperature and satellite radiance data of the middle and upper stratosphere were used for comparison, as well as wind data from Canada. The existence or nonexistence of coupling between the observed large scale zonal wind disturbances in the upper mesopause region (90 to 100 km) and corresponding events in the stratosphere are discussed

On the dependence of the lower thermospheric wind regime on the solar cycle

The lower thermosphere occupies the intermediate position between the overlying thermospheric layers, for which direct correlation of its parameters with solar variety variations is well established, and the underlying ones, where this correlation is mainly of an indirect character. Therefore, for understanding the mechanism of solar terrestrial correlation it is important to investigate the dependence of different atmospheric parameters in the lower troposphere, and of wind regime parameters in particular, on the solar activity. Several series of observations were used which include the results of meteor radar wind velocity measurements carried out in Obninsk complemented by the data obtained using the same technique at Jodrell Bank from 1953 to 1958 and in Kharkov from 1960 to 1963. The interannual variations of values averaged over these periods for prevailing wind velocities and semidiurnal harmonic amplitudes and also results for some months are presented. These results are discussed

Wind regime peculiarities in the lower thermosphere in the winter of 1983/84

Temporal variations of prevailing winds at 90 to 100 km obtained from measurements carried out in winter 1983 to 1984 at three sites in the USSR and two sites in East Germany are reported. These variations are compared with those of the thermal stratospheric regime. Measurements were carried out using the drifts D2 method (meteor wind radar) and the D1 method (ionospheric drifts). Temporal variations of zonal and meridional prevailing wind components for all the sites are given. Also presented are zonal wind data obtained using the partial reflection wind radar. Wind velocity values were obtained by averaging data recorded at between 105 and 91 km altitude. Wind velocity data averaged in such a way can be related to about the same height interval to which the data obtained by the meteor radar and ionospheric methods at other sites, i.e., the mean height of the meteor zone (about 95 km). The results presented show that there are significant fluctuations about the seasonal course of both zonal and meridional prevailing winds

Arc Magmas from Slab to Eruption: The Case of Kliuchevskoy Volcano

Arc magmas are generated by a number of mantle and crustal processes. Our multidisciplinary, long-term research is aimed at deciphering these processes for a single arc volcano, Kliuchevskoy volcano in Kamchatka. Some key results of the study follow: 1) Modeling of trace element and H2O contents in melt inclusions suggests that the primary magmas originate via hydrous flux-melting of the mantle wedge at temperatures close to the dry peridotite solidus. The role of decompression melting is minor or absent at Kliuchevskoy and other arc volcanoes built on relatively thick crust. 2) Geochemistry of high-Mg olivine suggests that primary Kliuchevskoy magmas have substantial contribution from olivine-free pyroxenite (up to 30 %), which could be formed by reaction of slab melts (or supercritical fluids) with mantle wedge peridotite. 3) Parental Kliuchevskoy melts start to crystallize as deep as the Moho boundary, and the erupted magmas reflect multistage and complex processes of crystallization, magma mixing and crustal assimilation. None of the Kliuchevskoy rocks analyzed thus far represent true primary melt compositions. 4) The Kliuchevskoy Holocene eruptive history is not steady-state in terms of eruption rate and geochemistry. There are two millenial cycles with major and trace element and OSr- Nd-Pb and U-series isotope compositions of the magmas changing gradually from more to less affected by crustal (?) assimilation. The onset of the cycles correlates with periods of enhanced volcanic activity in Kamchatka, suggesting that the extent of magma-crust interaction is inversely related to magma production rate and thus magma flux from the mantle

First results of meteor radar lower thermosphere wind measurements at Dixon, Arctic (73.5゜N, 80゜E)

Results of simultaneous wind measurements by the identical meteor radars at Dixon (73.5°N, 80°E) and Obninsk (55°N, 37°E) are presented for the time interval from November 12, 1999 to July 31, 2000. A number of features were observed which require comprehensive investigation on the basis of long-term wind measurements in the high-latitude lower thermosphere. The observed semidiurnal tide phases at Dixon are close to those published for Troms0, providing some evidence for predominance of the migrating semidiurnal tide for semidiurnal oscillations at this latitude. Highly coherent oscillations in tidal amplitudes and prevailing winds were also revealed, as well as time intervals with non-significant semidiurnal tide during which oscillations with periods different from but close to 12 h were observed

The summertime 12-h wind oscillation with zonal wavenumber <i>s</i> = 1 in the lower thermosphere over the South Pole

International audienceMeteor radar measurements of winds near 95 km in four azimuth directions from the geographic South Pole are analyzed to reveal characteristics of the 12-h oscillation with zonal wavenumber one (s=1). The wind measurements are confined to the periods from 19 January 1995 through 26 January 1996 and from 21 November 1996 through 27 January 1997. The 12-h s=1 oscillation is found to be a predominantly summertime phenomenon, and is replaced in winter by a spectrum of oscillations with periods between 6 and 11.5 h. Both summers are characterized by minimum amplitudes (5?10 ms?1) during early January and maxima (15?20 ms?1) in November and late January. For 10-day means of the 12-h oscillation, smooth evolutions of phase of order 4?6 h occur during the course of the summer. In addition, there is considerable day-to-day variability (±5?10 ms?1 in amplitude) with distinct periods (i.e., ~5 days and ~8 days) which suggests modulation by planetary-scale disturbances. A comparison of climatological data from Scott Base, Molodezhnaya, and Mawson stations suggests that the 12-h oscillation near 78°S is s=1, but that at 68°S there is probably a mixture between s=1 and other zonal wavenumber oscillations (most probably s=2). The mechanism responsible for the existence of the 12-h s=1 oscillation has not yet been identified. Possible origins discussed herein include in situ excitation, nonlinear interaction between the migrating semidiurnal tide and a stationary s=1 feature, and thermal excitation in the troposphere