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During the DYANA campaign in early 1990 turbulent parameters were measured at various places by means of in situ and ground supported techniques. Rocket borne instruments detected small-scale fluctuations of neutral (TOTAL instrument) and ion (PIP instrument) number densities in the mesosphere and lower thermosphere. A total of six flights was successfully performed in Andoya (69°N) and two in Biscarosse (44°N). Altitude profiles of turbulent parameters, such as turbulent energy dissipation rates e. and turbulent diffusion coefficients K were derived from the fluctuations. Thanks to improvements in the instrumental capabilities, the reliability of the absolute values is unprecedented. The mean turbulent energy dissipation rates measured both by TOTAL and PIP in Andoya show very low values ( Nearly simultaneously with the sounding rocket flights, temperatures and winds were measured by meteorological rockets and by lidars. This allows study of the relationship between the occurrence of turbulence and the atmospheric stability, parameterized by the Richardson number. In 14 out of 18 cases strong turbulent layers were accompanied by low Richardson numbers. Both wind shear and convectively generated instabilities were observed. Given a particular altitude in the mesosphere, the TOTAL and PIP instrument detected turbulence in approximately 40–60% of all flights. In addition to the in situ measurements, energy dissipation rates were measured around 75 km by the chaff dispersion technique at Heiss Island (81°N) and at Volgograd (48°N). Much higher e values were observed (typically 100 mW/kg) using this procedure than those values obtained by in situ measurements. However, due to non-turbulent dispersion processes, such as small-scale gravity waves and wind shears, the absolute e values from this technique are considered upper limits.

Results obtained with rocket-borne nose tip probes which measured the full current/voltage characteristics by linearly sweeping the probe's driving potential between positive and negative against the rocket's body as a reference suggest that such probes work in the middle atmosphere as mobility probes. It was found that the electron current depends upon positive ion composition in the sheath of the probe and rather strongly upon ambient air temperature.

Two series of measurements of horizontal wind velocity, one performed in winter 1990 at 44°N latitude, and the other in summer 1988 at 69°N latitude, were subjected to a spectral analysis. The two series covered a height interval of 11–15 km centred at about the same height (92.5km in winter, 91.5km in summer). In both cases the slopes of the spectra were close to −3. A dominant wavelength (if it existed) must have been larger than the height interval covered.

Five foil chaff and two falling sphere rockets flown during the MAC/SINE Campaign on 15 July 1987 at Andenes, Northern Norway (69°17′N). From these rocket measurements, turbulent energy dissipation rates, vertical wind shears and Richardson numbers as functions of height were derived in the range from 82 to 92km. Turbulent energy dissipation rates generally range from 1.4 × 10−5 to 2.0 × 10−2W/kg and are consistent with other experiments performed at the same latitude. Strong wind shears of the order of 50–90 m/s/km are observed at various heights. Good correspondence between turbulence intensity peaks, regions of strong wind shear and low Richardson number is found. Vertical wavenumber spectra of the five scalar winds measured by the foil chaff rockets indicate that there is an excellent agreement with the saturation hypothesis, suggesting that the turbulence intensity peaks measured in this salvo are linked directly to the saturation of gravity wave motions via dynamical instabilities.

In the altitude range 70–100 km, high-resolution wind profiles have been measured during the summers of 1987 and 1988 at Andenes (69°N). We report on the wind corners observed in these profiles and compare their properties with those of wind corners seen in the winter of 1983–1984 and autumn 1987. Five of the main results are as follows. (1) The occurrence rates for wind corners in general are similar in summer and in winter. The database for autumn (only 7 flights) was too small to draw any firm conclusions. A strong wind corner was seen, roughly, on every third experiment, both in summer and in winter. (2) The results obtained on the temporal occurrence of wind corners suggest that wind corners seem to have no preference to appear at certain hours of the day. (3) Wind corners tend to appear at preferred heights which are higher in summer than in winter. The spacing between these preferred heights is about 5 km in summer and about 3-3.5 km in winter. (4) In strong wind corners the sense of rotation of the wind direction is positive in summer and negative in winter (with positive being defined as a rotation of the wind direction from northward towards eastward with increasing altitude). (5) At altitudes below 90km wind corners tend to occur at or close to atmospheric layers having Ri ≈ 0.25.

Two field campaigns were conducted, primarily in northern Norway, in the summer and late autumn of 1987; these yielded a total of 41 in situ temperature profiles and 67 in situ wind profiles. Simultaneously, ground-based measurements were conducted of OH temperatures and sodium lidar temperatures for 85 and 104 hours, respectively. The summer campaign's mean temperature profile exhibited major deviations from the CIRA (1986) reference atmosphere; the differences between this model and the observations are less pronounced in the autumn. Both the summer and autumn mean wind profiles were in general agreement with the CIRA model.

The aerodynamic behaviour of foil chaff (rectangular plates) used for in-situ measurements of atmospheric motions in the middle atmosphere (up to 100 km altitude) can be described by Stokes' Law in which the corrections are applied to the coefficient of viscosity. The results obtained with this approximation are in good agreement with observations and allow us to explain in detail certain peculiarities occasionally seen in the tracking of chaff clouds by radar.

We present simultaneous spectra of horizontal and vertical wind fluctuations obtained from foil chaff measurements carried out during the MAP/WINE Campaign in the winter of 1983/84 above Andoya. The wind data with a height resolution of 25 m measured at heights of 72–88 km were used to calculate the vertical wavenumber spectra. Vertical wavenumber spectra computed from horizontal velocities have slopes close to −2.5 and −2.6 in the range of 2.1–100m wavelengths for the zonal and meridional winds. These observed slopes agree well with the slope of −2.4 for the vertical wavenumber predicted by the universal gravity wave spectrum model, suggesting that gravity waves are the dominant motion in the horizontal flow. The vertical wavenumber spectra for the vertical velocity appear to follow power laws with exponents in the − 1.8 to −3.7 range. These do not agree with the values discussed in the literature, and show that the spectral power levels are an order of magnitude lower than for the horizontal velocity spectra.

The correlation at latitude 37°N between zenith brightness of 557.7 nm atomic oxygen airglow and short wave radio wave absorption was investigated. A correlation seems to exist only when the amount of absorption is relatively low and does not exceed a certain critical value. Electron density profiles measured when the radio wave absorption was slightly below the critical value, slightly above it, and winter-anomalous show that the main contribution to absorption is shifted to lower heights when absorption increases and becomes winter-anomalous. Results of DC probe measurements suggest that the atmospheric temperature increases when this change occurs.

Five vertical profiles of scalar horizontal winds have been measured at high resolution (25m) in the range from 80–95 km during the last salvo of the MAC/SINE campaign in the summer 1987 at Andenes, Northern Norway (69.3°N). Our purpose in this study is to examine the consistency of the motion spectrum with the saturated spectrum of gravity waves proposed by Smith S. A. , Fritts D. C. and Van Zandt T.E. , (1987, J. atmos. Sci . 44 , 1404). An analysis of vertical wavenumber spectra of the five horizontal wind profiles is presented and it is found that (a) the average slope of the five vertical wavenumber spectra is −3.0 ± 0.2 for wavelengths in the range from 6.4 km to 100 m. The slope is considerably steeper than the vertical wavenumber spectra of the horizontal velocity discussed in the literature, (b) the average vertical wavenumber spectrum shows that there is excellent agreement between the observed spectrum and the saturated spectrum in both slope and amplitude, suggesting that saturation processes do indeed act to control spectral amplitudes at large wavenumbers, and (c) a dominant vertical wavelength of 6.4 km is found in the mesosphere. Taken together, our observations provide further support for the saturated spectrum theory.

The results of in situ measurements of electron concentration in the D-region of the ionosphere obtained with different probe techniques during the Western European Winter Anomaly Campaign 1975/76 are described. Electron density profiles were measured on fifteen days when the amount of absorption was low, medium or winter-anomalous at time of launch. In agreement with earlier results and with those gathered by other authors, the electron density was found to be increased between about 75 and 95km when winter-anomaly was present. One probe technique allowed measurements of ionization also at heights well below the D-region where the number density of free electrons is very small compared with that of negative ions. On four flights of this probe, electrons could be distinguished from ions in the probe records at heights between 58 and 62 km, in one case even from 38 km upwards. This means that λ, the ratio between the number density of negative ions and that of free electrons had changed in favour of electrons in this height region when these launches took place. Further, significant increases of ion density by a factor of 14–20 at a height of 40 km and a different scale height of ionization between 40 and 70 km was observed on three flights. Two events of this kind were observed when λ was small at heights below 70 km. This increase of ionization at 40 km was neither related to air temperatures measured with a different instrumentation flown on small meteorological rockets shortly after the launch of the guard ring probes, nor to cosmic ray intensity measured on the ground.

Quasi-periodic oscillations with periods ranging from days to several weeks can clearly be traced in tropospheric parameters and parameters of relevance to the mesosphere and to the D -region of the ionosphere like short wave radio wave absorption data, but a permanent upward propagation of these planetary-scale waves does not seem to exist. The transition of the summer atmosphere into a winter atmosphere however, as is seen at the bottom of the troposphere as an increase of the sum of the annual and half annual Fourier components of air pressure (which begins in September and lasts until midwinter) is accompanied by a parallel change of the ionospheric D -region, namely: the increase of short wave radio wave absorption, well known as the winter-anomaly.

Turbulent energy dissipation rates and eddy diffusion coefficients in the 66–90 km altitude range using the foil cloud technique are presented. Turbulent energy dissipation rates vary between 3.2E-5 and 8.6E-2 W kg −1 , and between 0.1 and 170 m 2 s −1 for eddy diffusion coefficients. These derived quantities are in good agreement with the values discussed in the literature. The average value of the calculated spectral index for the vertical velocity is −1.689 ±0.569, which is very close to −5 3 . Richardson number profiles obtained show that the presence of turbulence is associated with a range of dynamic instability.

Results obtained on vertical velocities of air in the mesosphere are presented which were measured by small foil clouds tracked by radar at Andenes (69°) during January and February 1984. The results (typically ± 4–6 m s −1 , up to 10 m s −1 , and oscillatory in nature) are in good agreement with those obtained by ground-based remote sensing methods. Supplementary observation techniques of the radar return signal show that the interactions between background wind and waves quite often cause small-scale flow separation effects which escape detection when conventional radar tracking is the sole source of information.

Electron density profiles mainly gathered between 70 and 100 km from 19 rocket flights during the Western Europe Winter Anomaly Campaign 1975/76 are presented. After suitable normalization these profiles can be arranged vs A3 absorption enhancement and provide an electron density history for the time period of the campaign.

The MAP/WINE campaign has yielded information on small scale structure and turbulence in the winter mesosphere and lower thermosphere by a number of very different remote and in situ techniques. We have assimilated the data from the various sources and thus attempted to present a coherent picture of the small scale dynamics of the atmosphere between 60 and 100 km. We review physical mechanisms which could be responsible for the observed effects, such as ion density fluctuations, radar echoes and wind corners. Evidence has been found for the existence of dynamic structures extending over distances of the order of 100 km; these may be turbulent or non-turbulent. The results indicate that gravity wave saturation is a plausible mechanism for the creation of turbulence and that laminar flows, sharply defined in height and widespread horizontally, may exist.

During the period December 1975–mid-February 1976 of the Western European Winter Anomaly Campaign, the local dynamical and thermal structure of the stratosphere and mesosphere was determined by some 31 rocket launches at El Arenosillo, Spain, while the mesospheric thermal structure in the winter (northern) hemisphere was derived from Nimbus 6 satellite observations. An analysis of these data is presented here. As determined by the A3 technique and the parameter Ld[= L0(n +1)], ionospheric absorption is significantly correlated with many features of the dynamical and thermal structure of the atmosphere. The strongest correlations are, on this occasion, with local winds, at a level between 85 and 92 km altitude, the sense being that high absorption corresponds to northward and eastward wind tendencies, while low absorption corresponds to southward and westward wind tendencies. Additionally, there is a significant correlation with local temperature above 60 km, high absorption corresponding to high mesospheric temperatures. These local variations are corroborated by data obtained from the PMR 3000 channel of the Nimbus 6 satellite (centred about 80km). A trivariate analysis of absorption (Ld), temperature (40° latitude) and meridional temperature gradient along the 0° longitude meridian, which corresponds to the pressure gradient driving a ‘geostrophic’ zonal wind, shows extremely high significance. High ionospheric absorption in Spain is associated with disruption of the normally strong winter vortex around a warm winter mesospheric pole. As the polar temperature decreases, temperatures at low- and mid-latitudes increase and, responding to a decrease of meridional temperature gradient, the mid-latitude zonal and meridonal wind regime changes. Disturbances of the winter mesospheric polar vortex are triggered by the upward propagation of earlier perturbations within the troposphere and/or stratosphere. Delays of 2–4 days are indicated between the onset of stratospheric circulation disturbances, perturbation of the mesospheric polar vortex, and the consequent dynamical and thermal effects in the mid-latitude mesosphere which are associated with anomalously high ionospheric absorption.

The results of conductivity, ion mobility and ion conductivity measurements performed below 70 km with a parachuted Gerdien aspiration analyser during winter and in the summer season are described. The mobility of the most abundant species of positive ions was found to be the same for summer and winter conditions. Observed increases of conductivity are therefore caused by increased carrier density. Increases of negative conductivity in heights above 40 km found in the winter seasons were probably caused by an increase of the number density of free electrons. A straight-forward relation between the number density of charged carriers and the air temperature was not found. Suggestions are made for the cause of the observed seasonal variation in ion density and in λ, the ratio of negative ions to electrons.

Wind measurements which were carried out during the MAP/WINE Campaign in northern Scandinavia between 2 December 1983 and 24 February 1984 are used to derive background winds and monthly as well as winter mean values from the ground up to 90 km altitude. These mean winds compare favourably to the wind field proposed for the revised CIRA 86, which is deduced from satellite measurements. The vertical structure of the zonal monthly means is similar in both data sets during January and February. The winter mean zonal winds are observed to be slightly stronger in the stratosphere and lower mesosphere during the MAP/WINE winter than the satellite winds proposed for CIRA 86. The long term mean meridional winds are in good agreement up to 60 km. They indicate a dominant influence of quasistationary planetary waves up to 90 km and an ageostrophic poleward flow between 60 km and 85 km over northern Scandinavia, which maximizes at 76 km at about 8 m s −1 . The observed short term variability of the wind is discussed with respect to a possible impact of saturating gravity waves on the momentum budget of the middle atmosphere.

The seasonal variation of radio wave absorption of three mid-latitudes is calculated using an atmospheric model and compared to measurements of two winters and one summer. From the correlations of the absorption patterns of three A3 paths, velocities of these patterns are derived and the relevance of such velocities to enhanced absorption is examined.

A significant correlation has been found between interplanetary magnetic field polarity changes and the short wave radio wave absorption of the D -region. The results support the explanation that the galactic cosmic rays are one of the most important transfer agents of sun-weather relationships.

Fieldstrength records on 2.8 Mc/s between Sardinia and Italy have shown that the winter anomaly of ionospheric absorption still exists at 40° northern latitude but is less pronounced and of shorter duration than at 52°N.