Semidiurnal tidal winds at Collm (52°N, 15°E) and Saskatoon (52°N, 107°W) over the decade 1978–1988

Mean winds and tides have been measured by the LF and MF radar systems at Collm and Saskatoon respectively. Semidiurnal tide amplitudes and phases near 90 km evidence very similar monthly variations. A detailed comparison of mean wind and tidal profiles (85–110 km) in the Septembers of 4 years shows some differences however, which are consistent with regional (Europe-Canada) differences in the mean background winds.     

Mean winds at 60–90 km observed with the MU radar (35°N)

Mean winds at 60–90 km altitudes observed with the MU radar (35°N, 136°E) in 1985–1989 are presented in this paper. The zonal wind at 70 km became westward and eastward in summer and winter, respectively, with a maximum amplitude of 45 m s⁻¹ westward in early July and 80 m s⁻¹ eastward at the end of November. The meridional wind below 85 km was generally northward with the amplitudes less than 10 m s⁻¹. In September to November, the meridional wind at 75–80 km becomes as large as 20–30 m s⁻¹. Those zonal wind profiles below 90 km show good coincidence with the CIRA 1986 model, except for the latter half of winter, from January to March, when the observational result showed a much weaker eastward wind than the CIRA model. The height of the reversal of the summer wind from westward to eastward was determined as being 83–84 km, which is close to the CIRA 1986 model of 85 km. The difference between the previous meteor radar results at 35–40°N, which showed the reversal height below 80 km, could be due to interannual variations or the difference in wind measurement technique. In order to clarify that point, careful comparative observations would be necessary. These mean winds were compared with Adelaide MF radar observations, and showed good symmetry between the hemispheres, including the summer reversal height, except for the short period of eastward winds above Kyoto and the long period over Adelaide.     

Variations of mean winds and tides in the upper middle atmosphere over a solar cycle,Saskatoon, Canada, 52°N, 107°W

Saskatoon (52 N, 107 W) medium frequency (MF) radar data from 1979 to 1990 have been analyzed to investigate the solar activity effects on upper middle atmospheric winds and tidal amplitudes. The period of study covers two solar maxima and a solar minimum; the continuous data allow a systematic analysis of solar cycle dependence on mean winds and tides. The height region of 79–97 km sampled in the study shows an apparent but very weak dependence of mean winds and tidal amplitudes on solar activity variation. The observed features are fairly consistent with the early results reported by Sprenger and Schmindkr [(1969) J. atmos. terr. Phy. 31, 217). The mean zonal wind and the semidiurnal tidal amplitudes appear to exhibit positive and negative correlations with the solar activity, respectively; the statistical significances of these correlations are generally low. There is a biennial periodicity evident in the zonal wind oscillations but this docs not have a consistent phase relationship with the equatorial stratospheric wind oscillations (QBO). The meridional winds and the tidal amplitudes are characterized with different and quite irregular periods of oscillations (2–5 yr). The diurnal tidal variations over the solar cycle are small and irregular, although amplitudes are slightly larger during the solar minimum years.     

Winds and waves in the middle atmosphere at Saskatoon (52°N, 107°W), Collm (52°N, 15°E) and Badary (52°N, 105°E)

Winds data from three radar systems in the U.S.S.R. G.D.R. and Canada, which are well-spaced along the 52°N latitude circle, are used to illustrate longitudinal/regional variations in the dynamics of the upper middle atmosphere 80–97 km. Responses to the stratospheric warming of 1982/3 are noted at all three locations, but the zonal wind does not reverse at Badary, consistent with the flow there being eastward during all months of the year. Planetary wave period oscillations (2–30 days) are observed at all locations, and highly significant cross-spectral coherences exist between the three stations.     

Dynamics of the upper middle atmosphere (80–110 km) at Tromsø (70°N) and Saskatoon (52°N), June–December 1987, using the Tromsø and Saskatoon MF radars

A real-time-winds (RTW) system from Saskatoon operated with the Tromsø MF (partial reflection) radar system on a continuous basis in the period June–December 1987. This interval includes MAC/SINE and EPSILON. Profiles with 3-km resolution were obtained every 5 min—weak ionization and few geomagnetic disturbances limited the observations normally to 80–110 km. However, daily mean winds, diurnal and semidiurnal tidal characteristics (amplitudes, phases and wavelengths) and gravity wave characteristics (intensities, mean directions) are available throughout this interval. This is particularly valuable in defining the background state for some experiments, e.g. rockets, and for comparison with related parameters from the lidar and other radars (EISCAT, SOUSY-VHF). Comparisons with these dynamical parameters from Saskatoon (52 N) are made : the zonal circulation was weaker at Troms0, tidal amplitudes smaller, and summer 12-h tidal wavelengths shorter ( ~ 80 km vs ~ 100 km). The fall transition for this tide occurred in September at Troms0, earlier than observed elsewhere.     

Comparisons between time variations in D-region winds and electron densities at Saskatoon,Canada (52°N; 106°W)

A partial reflection radiowave system (2.2 MHz) has been used at Saskatoon, Canada (52°N, 106°W; L = 4.4) to obtain electron densities (~65–85 km) by the differential absorption experiment, and winds (52–118 km) by the spaced antenna drifts experiment. These data have been compared during the winter (December–March) of 1974/75, eleven selected days during January and February of 1976, and during 10 days in each of the four seasons of 1976. There is consistent evidence for a correspondence between increasing ionization and decreasing northward or increasing southward winds, during winter months. This is consistent with the hypothesis that nitric oxide (NO), created during magnetic storms by the associated auroral activity, contributes to electron density variability by way of circulation changes and atmospheric waves. It has not been possible to distinguish between a latitude gradient of NO or isolated accumulations of this minor constituent.     

Winds oscillations (∼ 6h–6days) in the upper middle atmosphere at Monpazier (France, 45°N, 1°E) and Saskatoon (Canada, 52°N, 107°W) in 1979–1980

The medium frequency radar (∼ 2.2 MHz) at Saskatoon has been run continuously since 1978 and the Meteor Radar at Monpazier ran continuously for ∼ 10 day intervals in most months of 1979/1980. The radars are separated by ∼ 8000 km. Because of the excellent quality of the data, spectral and harmonic analyses have been completed from ∼ 70 to 100km and oscillations with periods of ∼ 6h–6days studied.There are substantial similarities in the mean zonal winds, both with regard to magnitudes and times of seasonal reversals; also in annual and semi-annual oscillations. In general, the semi-diurnal tide has similar amplitudes, phases and vertical wavelengths : there are consistent summer (long λ) and winter (short λ) characteristics, with rapid transitions between them. Differences between the timing of these transitions and in some of the mid-season tides are discussed. The diurnal tide is less regular and of smaller amplitude at both locations, often being too small to reliably characterize at Monpazier. However, seasonal variations between summer and winter months may be discerned.In addition to the 24 and 12 h tidal oscillations, which traditionally are studied in most detail, there is clear evidence for additional osculations near 6,8, ∼ 10 and ∼ 16 h and longer periods of ∼ 2 and ∼ 5 days. The amplitudes of these are often comparable or larger than the ‘dominant’ 24 and 12 h tides. The monthly and seasonal variations of these additional oscillations are studied, as a function of height, at the two locations. There is evidence for large scale (global) and small scale (local) disturbances in the wind field.     

An assessment of winds data (60–110 km) obtained in real-time from a medium frequency radar using the radio wave drifts technique

In a recent paper (Meek, 1980) a fast and efficient method for analysing ionospheric drift records was described. The technique is well suited to real-time analysis.Examples of winds data (60–110 km) obtained from the medium frequency (2.2 MHz) radar at Saskatoon (52°N, 107°W) during 1980 are described here. The quantity and quality of data obtained during typical summer and winter months are discussed. Height time cross-sections of mean winds and tides are also shown.     

Heights of MF radar scatter (1986/87) and the wind field (55–95 km): Saskatoon,Canada

The Saskatoon MF radar (2.2 MHz) at 52°N, 107°W, has been used to measure the heights of occurrence of radar scatter during four seasons, and twelve months of 1986/87. Mean winds, and gravity waves are also available, by the spaced antenna method and from the same radar echoes. Certain heights, called elsewhere ‘preferred heights’, are identified near 60km, 70km, 75km in summer, and 80–86 km. Several layers have seasonal and diurnal variations. Associations with electron density gradients (rocket data), mean wind shear in summer, and gravity wave amplitude-minima in the equinoxes are effectively demonstrated. Case studies, involving 3 h data sets of radar scatter and wind elaborate the comparison: gravity waves of long period (τ > 6 h) are shown to modulate the scattering process.     

Tidal winds at mesopause altitudes over Arecibo (18°N, 67°W), 5–11 April 1989 (AIDA '89)

An imaging Doppler interferometer (IDI) radar was operated during the three AIDA '89 campaigns in Puerto Rico over the period March–May of 1989. The output of the IDI analysis characterizes radar scattering in terms of a number of discrete ‘scattering points,’ also referred to as ‘multiple scattering centers,’ IDI/MSC for short. For each of these points the three-dimensional location, radial velocity and amplitude and phase are determined, similar to the output of meteor radars. We have applied the conventional Groves [(1959) J. atmos. terr. Phys. 16, 344–356] meteor wind radar analysis to the scattering points to produce the mean apparent motions over the height range from 70 to 110 km which are presented here. The mean apparent motion of the scattering centers is the quantity that would correspond to the neutral atmosphere wind or bulk motion if the scattering points are physical entities (such as turbulent eddies) whose motions are determined solely by advection. This is the quantity which is treated as the ‘wind’ in the analysis which follows and which should be compared to the wind measurements as deduced from the other methods employed during this campaign. There is, however, a caveat which supports the contention of Hineset al. [(1993) J. atmos. terr. Phys. 55, 241–287] that extreme care must be used in interpreting the velocities measured by partial reflection radars as winds. The current application of the Groves method of analysis has revealed motions from which one would infer a typical equatorial easterly circulation, with mean meridional circulation becoming significant only above 96 km. A periodogram analysis of the complete data interval (5–11 April) has shown the diurnal tide to be the most significant feature of the wind field at these altitudes, with zonal amplitudes up to some 50 m/s and meridional amplitudes approximately half this value. The 12 and 6 h tides become as significant as the diurnal above 100 km. The two day (48 ± 5 h) wave is the next most significant feature, with zonal amplitude increasing with height up to 30 m/s at 110km. The semidiurnal tide is not at all well developed below 100 km. However, analysis on a day by day basis reveals a significant semidiurnal component which is not phase coherent over the total interval. Mean vertical velocities are of the order of tens of centimeters per second and are considered to be more realistic than the meters per second velocities usually inferred from analyses of meteor trail drifts.     

Meteor radar observation at Kyoto in two C.T.O.P. periods (July 20–August 7, 1978, and March 13–29, 1979)

Meteor radar data taken in 1978–1979 at Kyoto station (35°N, 136°E) are processed statistically by Groves' algorithm (1959). Analysis is done especially for data in two C.T.O.P. campaigns carried out in summer and in spring to study a seasonal variation of tides. The reliability of the algorithm is clarified by a simulation with a realistic model. Vertical wavelengths of the diurnal tide and the semidiurnal tide are estimated from height profiles. The diurnal tide becomes evanescent in summer, and the semidiurnal tide appears to be the S_2,2 mode in summer and the S_2,4 mode in spring. This suggestion regarding the semidiurnal tidal modes agrees with the latitudinal variation deduced from many other meteor radar data. Tidal wave energy in the meteor region is estimated. A sudden enhancement of energy is observed in both the diurnal and the semidiurnal tides. There is a clear correlation between an energy decrease of the diurnal tide and an energy increase of the semidiurnal tide.     

The Indo‐European mirror: Monotheism and polytheism (J.G. Herder,E. Renan,A. Pictet,F.M. Müller and R.F. Grau)

Some authors assigned the Indo‐Europeans a mirror‐like role which allowed them to understand their own position with respect to contemporary Christian values. After dealing briefly with the writings of J.G. Herder, I shall evoke a certain number of questions which oriented the research of E. Renan, F.M. Müller, A. Pictet and R.F. Grau. The works of the latter authors expounded fabulous genealogies, organizing them into explanatory systems that radically opposed Hebrew monotheists to Indo‐European polytheists. Thus, depending on whether they had used the Semites or the Indo‐Europeans as their starting‐point, they concluded that monotheism or polytheism, respectively, was the archaic source of human thought. The goal on their horizon was a ressuscitated West, forever in the forefront of progress, often simultaneously Christian and scientific. If this type of historiographic analysis is urgently needed at the present time, its purpose is not to provide a grid for distinguishing “truth”; from “falsehood,”; but rather to grasp a set of scholarly traditions within its own channels of transmission.     

Total ozone changes in the northern hemisphere mid-latitudinal belt (30–60°N) derived from Dobson spectrophotometer measurements, 1964–1988

A statistical analysis is presented of the daily values of total column ozone obtained during 1964–1988 from a network of 24 Dobson instrument stations located within the mid-latitudinal belt 30–60°N. The year-round-, as well as the summer- and the winter data have been analyzed to detect year-to-year changes in the annual pattern of the probability density function of total ozone (PDFTO) in the belt. Long-term variations in the PDFTO have been deduced from trend analyses of the following statistical characteristics of the annual pattern of the PDFTO: mean, standard deviation, median, 10 and 90 percentile, and the asymmetry coefficient. The trends have been calculated from a multiple regression model adjusted for serial correlations, the 11-yr solar cycle, and long-term stratospheric circulation fluctuation effects. We have found that the pattern of the PDFTO has been drifting uniformly (without changes in its shape) towards lower ozone values, with some seasonal peculiarities in the drift (the annual rate of total column ozone loss). The winter pattern of the PDFTO moves (with a drift of 2.3% per decade) towards lower ozone values faster than the year round pattern (drift equals 1.8% per decade) and the summer pattern of the PDFTO (drift equals 1.5% per decade).