DYANA Campaign Research Articles

Non-linear resonant wave–wave interaction (triad): Case studies based on rocket data and first application to satellite data

Gravity waves are well known to have significant influence on the circulation and thermal structure of the atmosphere by transporting energy and momentum. When reaching instability, gravity waves dissipate energy, causing the surrounding wind regime to be modified. Therefore, knowledge about the geographical location of sources of gravity waves (‘GWS’), their dynamical characteristics (e.g. wave spectral information) as well as their energy dissipation mechanisms and rates is essential. Besides pure wave breaking, other possibilities of energy transmission are possible. One prominent mechanism is the non-linear resonant wave–wave interaction (‘triad’). In this paper, an early case study performed by Widdel et al. [1994. Vertical velocities measured at Biscarrosse (44°N) and by EISCAT at Tromso (69.6°N) during DYANA campaign. Journal of Atmospheric and Terrestrial Physics 56, 1779–1796], to look for a possible triad within wind data obtained by the meteorological rocket based foil-chaff cloud technique during the DYANA campaign (DYnamics Adapted Network for the Atmosphere) in 1990, is reinvestigated. Their assumption of seeing a triad in the data is now proved. In addition the observed wave field is dynamically characterized. Energy dissipation rates and the acceleration of the zonal mean flux are estimated applying linear and non-linear theory, respectively. Furthermore, ozone data derived from the satellite-based ERS-2-GOME (Global Ozone Monitoring Experiment) instrument in January 2003 are assimilated into the 3D-chemical transport model ROSE (Research on Ozone in the Stratosphere and its Evolution) to yield synoptic and global coverage and to allow the tracing of dynamical processes. Regions of pronounced dynamical variability are identified and are supposed—at least occasionally—to generate gravity waves. Due to their relatively high vertical resolution, ozone measurements of the ENVISAT-GOMOS (Global Ozone Monitoring by Occultation of Stars) instrument are further used to look for possible indications of triad effects above these gravity wave sources (‘GWSs’).

Some results of S-transform analysis of the transient planetary-scale wind oscillations in the lower thermosphere

Technique appropriate to the analysis of lower thermospheric wind data recorded by global-scale networks of ground-based instruments are discussed. The S-transform technique is shown to be effective in the analysis of the main features of travelling planetary waves and this method is applied to the time series of horizontal-velocity data obtained during the DYANA campaign (January–March, 1990). The analysis reveals strongly transient behavior of the day-to-day lower thermosphere wind variations, as well as their specific longitudinal structure. In particular, it was found that the revealed quasi-15 day and quasi-5 day wind oscillations may be described as transient westwardpropagating waves with zonal wavenumber s = 1, while an oscillation with the a period near 7 days is tentatively identified as having a wavenumber s = 0.

Comparison of the CIRA 1990 planetary wave model to rocket temperature measurements

The new CIRA 1990 contains a wave model for the quasi-stationary planetary waves 1 and 2. Comparison to rocket measurements shows that the wave model underestimates the wave activity during disturbed winter periods. An amendment of the CIRA wave model was therefore developed on the basis of data obtained during the DYANA campaign. This Improved Wave Model (IWM) uses lower stratosphere radiosonde measurements as input data to predict upper stratosphere and mesosphere temperature disturbances. Maximum amplitude of wave No. 1 of the IWM is higher than the CIRA amplitude by a factor of 3.2. The IWM was applied to a strongly disturbed part of the MAP/WINE campaign, and very satisfactory results were obtained. The IWM accounts for more than 70% of the data variance both during the DYANA and the MAP/WINE periods.

Simultaneous observation of convective adjustment and turbulence generation in the mesosphere

We present simultaneous in situ measurements of turbulence and temperature in the midlatitude mesosphere obtained as part of the DYANA campaign on March 13, 1990 at Biscarrosse, France (44°N, 1°W). In this study, we have extended the temperature measurements of our rocket borne ionization gauge down to 70 km and directly compared them to the small scale density fluctuations. Between 74 and 81 km we observed a unique, sawtooth shape layer in the temperature profile with a slightly superadiabatic lapse rate. In the same region, strong turbulent density fluctuations were present. We interpret these observations as convective adjustment and associated turbulence.

Planetary wave activity in the lower ionosphere during the DYANA campaign

On the basis of MEM spectrum analyses, the main fluctuations formed in the lower ionosphere in the period range 3–35 days during the DYANA campaign are studied. The wave response of the lower ionosphere to changes in the thermal and dynamical regime is investigated separately for several altitudinal regions and because of the occurrence of a pronounced minor stratospheric warming during mid-February, also separately for the first (1 January–14 February) and the second (15 February–31 March) part of DYANA. According to different patterns of planetary wave activity in various ionospheric data, the lower ionosphere can be divided into altitudinal regions: the lowest D-region, the lower D-region, the upper D-region and the bottom part of the E-region. An attempt to identify the wave number of the best pronounced fluctuations, existing in most time series, with a mean period of about 12 days, indicates the zonal wave number K = 1. In general, the ionospheric data do not provide a well-consistent pattern of the planetary wave activity in the lower ionosphere during the DYANA campaign. Nevertheless, it seems to be sure that (1) the patterns of planetary wave activity in the first and the second half of DYANA are very different, and (2) changes in planetary wave activity over Europe appear to be arranged according to altitude, not latitude or longitude.

Long period/large scale oscillations of temperature during the DYANA campaign

During the DYANA campaign (January–March 1990) vertical temperature profiles were measured in the middle atmosphere above 11 rocket and four lidar stations in the northern hemisphere. Strong temperature variations were observed, especially at the medium to high latitude stations. Time series analysis was applied, and most oscillations were found to be quasi-periodic only, and restricted to certain altitude levels. Solely the longest periods (>4 weeks) and the shortest periods (around 5 days) were consisterrtly observed in the whole altitude regime, and were, therefore, further analysed. These temperature variations were found to be compatible with the assumption that the Quasi-Stationary Planetary Wave No. 1 (QSW 1) of the CIRA 1990 Model Atmosphere was modulated with the respective periods. Especially close similarity of the vertical phase structures was obtained. The amplitudes measured were, however, much larger than those of the model, and hence some amendment to the model may be appropriate. The importance of QSW 1 modulation appears to be considerable, as more than 50% of the temperature variance could be ascribed to it. The DYANA results were checked by an analysis of respective data from two other campaigns (Winter Anomaly campaign, 1976, and MAP/WINE campaign, 1984). Essentially the same results were obtained. Considering the strength of QSW 1 control, the midwinter middle atmosphere shows itself to be quite strongly and persisterrtly structured in both the vertical and horizontal directions. This applies to all parts of the stratosphere and mesosphere.

The DYANA campaign: a survey

The DYANA campaign ( DYnamics Adapted Network for the Atmosphere) was performed from January through to March 1990 in the northern hemisphere. A large number of ground-based, balloon and rocket borne experiments was performed to study various aspects of middle atmosphere dynamics (10–100 km). DYANA was a project of the Solar Terrestrial Energy Program (STEP). This paper briefly reviews the scientific objectives of the campaign, the campaign structure and the geophysical conditions present during the campaign. Detailed results of DYANA are presented in the subsequent 24 papers of this issue.

Vertical velocities measured at Biscarrosse (44°n) and by EISCAT at Tromsø (69.6°n) during the DYANA campaign

The vertical velocities of the atmosphere were measured at Biscarrosse (southwest France, 44°N) by the foil cloud method and at Tromsø (northern Norway, 69.6°N) using incoherent scatter (EISCAT) during the DYANA campaign from January 1990 to March 1990. A new type of foil which had a fairly low velocity of descent alleviated the investigation of small-scale vertical structures. The vertical velocities measured at Biscarrosse by the foil cloud method turned out to be rather moderate (±2–3 m/s) but were found to be superimposed by short-wavelength vertical waves (1–1.4 km) with about half that amplitude (1–1.5 m/s). This was considered to be a major result and a maximum entropy, a bispectral and a triad analysis of the vertical velocities measured in DYANA salvo 2 (on 20 February 1990) suggest a non-linear wave-wave interaction (‘parametric amplification’). A detailed analysis of this aspect which includes all flights is considered necessary. Vertical velocities measured by EISCAT at Tromsø turned out to be quite moderate and one sample (on 5–6 March 1990) is discussed. The large distance between Biscarrosse and Tromsø (3064 km) renders a direct comparison quite difficult

Rocket electron density profiles over Volgograd, Heiss Island and Esrange during the DYANA campaign

The results of the determination of electron density ( N e ) profiles at Volgograd, Heiss Island and Esrange ranges are discussed. Some of these profiles were obtained at solar zenith angles <90°, but at times near the sunset, and others at night-time. The profiles obtained during the DYANA campaign were compared with others obtained in the past, with solar and geomagnetic indices as well as with the temperature and atmospheric circulation in the stratosphere and mesosphere. The daytime electron densities below 85 km over Volgograd do not show any appreciable connection to the temperature. An anomalous period of low electron densities observed from February to the beginning of March rather seems to be connected with the meridional and vertical components of the atmospheric wind. We can speculate that the high night-time N e -values at middle latitude may be considered as a manifestation of a post-storm effect. The relationship of the N e -values at higher altitudes (>80 km) and radio wave absorption seems to be connected with the atmospheric circulation and geomagnetic activity. The N e -values in the polar cap region (Heiss Island) are below those at the same altitude in the auroral zone (Esrange), but higher than at middle latitudes (Volgograd). The N e -values over Heiss Island seem to be connected with the geomagnetic activity and the meridional component of atmospheric circulation; the thermal control of the D-region cannot be excluded.

Morphology of the D- and E-regions at high latitudes in the northern hemisphere during the DYANA campaign in 1990

The morphology of the D- and E-regions in the northern hemisphere at latitudes above 60°N during the DYANA campaign from 11 January to 16 March 1990 is described on the basis of riometer, rocket and EISCAT measurements. The campaign was carried out during the sunspot maximum year of solar cycle 22 and was aimed at studies of the middle atmosphere. During the winter anomaly days of the campaign period an increased ionospheric absorption measured by a riometer was seen on only one winter anomaly day, and only at the southernmost station of the riometer network at latitude 63°N. The ionospheric absorption did not increase during a stratospheric warming in early February. Both winter and autumn anomalies in the ionospheric absorption occurred during 1990. The substorm events observed during the campaign period are discussed and electron density profiles in the D- and E-regions are presented for different substorm phases.

The wind regime of the mesosphere and lower thermosphere during the DYANA campaign—I. Prevailing winds

During the DYANA campaign, winds and tides at mesospheric and lower thermospheric altitudes were measured by 14 ground based experiments (MF radars, meteor radars and LF-drift systems). The experiments were located between 107°W and 102°E, mostly in northern mid-latitudes with well covered areas in Central and Eastern Europe. Emphasis is placed here upon the vertical profiles and height-time contours of the prevailing zonal and meridional winds with different resolution (15 d, 4d). Generally, westerly winds are observed at heights below 95 km with a strong mesospheric variability and with longitudinal differences between the data of Central Europe, Eastern Europe, Asia and Canada. Planetary waves and a minor stratospheric warming in the first 10 days of February 1990 are the cause of this behaviour. In connection with the stratospheric warming, a wind reversal to summer east winds reaching from the upper stratosphere up to 95 km is observed. The close connection of the behaviour of the stratosphere with the observed longitudinal differences in the mesospheric response on the stratospheric warming and with the occurrence of wind oscillations (10–15 d) is discussed.

Gravity-wave activity and its relation with prevailing winds during DYANA

The DYANA campaign in early 1990 gave a unique opportunity to study the gravity wave (GW) activity in the middle atmosphere in relation to the general circulation. Several instruments, including Rayleigh lidars, ME and meteor radars, OH and O 2 spectrometers and radio-wave absorption receivers provided data at various locations in Europe and Canada to study the GW activity during the campaign. These sets of data indicate that the GW activity is in general enhanced during periods of strong westerly prevailing winds or high planetary-wave activity in the middle atmosphere. When two sets of data are compared, they show a rather fast decorrelation as a function of altitude difference or horizontal distance. This study confirms that the level of GW activity in the middle atmosphere is very sensitive to filtering by the mean wind, but does not exclude its sensitivity to the sources of GW.

Morphology and sources of turbulence in the mesosphere during DYANA

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 Andøya (69°N) and two in Biscarosse (44°N). Altitude profiles of turbulent parameters, such as turbulent energy dissipation rates ε. 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 Andøya show very low values ( < l mW/kg) in the lower mesosphere, increasing to ~ 10 W/kg in the upper mesosphere. The corresponding heating rates are approximately 0.05 and 1 K/day, respectively. The two flights performed in Biscarosse showed similar 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 ε 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 ε values from this technique are considered upper limits.

Lower thermospheric infra-red emissions from minor species during high-latitude twilight—A. Experimental results

During the DYANA campaign, thermospheric infra-red emissions of CO 2( v 2), CO 2( v 3), O 3( v 3) and NO ( ΔV = 1) were measured by a rocket-borne liquid helium-cooled spectrometer on 6 March 1990 above Kiruna, Sweden. The measured radiances are compared with the results obtained during other flights of the same instrument. According to the measured data the 15 μm band of CO 2 is in local thermodynamic equilibrium up to about (100 ± 5) km. Recently proposed high rate constants for the excitation of CO 2( v 2) in atomic oxygen collisions are verified by the measured data. The nitric oxide cooling rate in the lower thermosphere is found to be remarkably constant during different rocket soundings. A comparison between the measurements and a non-LTE model is given in part B of this paper; ( Ratkowski et al., 1994, J. atmos. terr. Phys. 56, 1899–1914).

The wind regime of the mesosphere and lower thermosphere during the DYANA campaign—II. Semi-diurnal tide

Co-ordinated ground-based radar measurements carried out during the 15 January–15 March 1990 DYANA campaign at 14 different geographical sites have provided a good opportunity to investigate the characteristics of semi-diurnal tidal variations in the mesosphere/lower thermosphere over a wide spectrum of space/time scales. It is pointed out that significant differences of monthly mean tidal parameters observed at the various sites may be explained by latitudinal and longitudinal effects. Well-defined 2–3-week oscillations of the tidal parameters are found to be typical of all observational sites. Their estimated space scales do not contradict the hypothesis about a possible coupling between these oscillations and the low wave-number processes in the stratosphere. Tidal parameter oscillations with 2–5-day periods may be explained to be effects of the nonstationary processes with longitudinal wave numbers S > 3.

Plasma instabilities in the lower E-region observed during the DYANA campaign

During the DYANA campaign a number of instrumented sounding rockets were launched from Andøya Rocket Range (ARR) in Norway (69°N) to study the dynamics of the mesosphere and lower thermosphere during winter conditions. The EISCAT UHF radar in Tromsø, located 130 km to the east of ARR, was used to map the electric field and the wind field in the same height region. During some of the launches, plasma irregularities with scales in the range from a few metres to tens of metres were observed. We focus our attention on an event which took place on 8/9 March 1990. Two instrumented payloads code-named DAT-73 and DAT-76 were flown 92 min apart during different levels of disturbance in the E-region. We have studied the plasma fluctuations observed during these flights in terms of the modified two-stream and gradient-drift instabilities using linear fluid theory. The observed height extent of the disturbed region is in excellent agreement with theoretical predictions based upon measurements of background plasma parameters. We also find that the instability is much stronger during the first part of the event as a consequence of larger drift velocities. This is evident by the large plasma fluctuations measured in situ as well as the electron temperature measured by EISCAT. An adequate description of the observations must include effects of electron density gradients and recombinational damping. During the flight of DAT-73, the plasma waves must propagate in a direction different from 90° with respect to the magnetic field, while the DAT-76 observations can be explained by plasma waves propagating normal to the magnetic field.

Lower ionosphere at middle latitudes: its morphology and response to meteorological and solar-terrestrial activity during the DYANA campaign 1990

A large number of radio wave absorption, ƒ min , and IPHA data measured in Europe and East Asia are investigated over the DYANA campaign period (1 January–31 March 1990) from the point of view of their response to meteorological and solar/geomagnetic forcing, of winter anomaly, and of a brief description of the state of the lower ionosphere on rocket salvo days. European mid-latitudinal measurements of electron density are briefly mentioned. The meteorological/solar control of the mid-latitudinal lower ionosphere during DYANA is considerably weaker than during MAP/WINE (winter 1983/84), but is evidently stronger than during MAP/SINE (summer 1987). The most distinct feature of the DYANA winter is a quite different response of the mid-latitudinal lower ionosphere to meteorological variability (namely to the 10 hPa North Pole temperature— indirect characteristics of a global state of the polar vortex) in the first and second halves of the DYANA period. The winter anomaly displays an expected magnitude and pattern during the DYANA winter. There is an expected weaker response of the lower ionosphere to the strong minor stratospheric warming of the first half of February. All three rocket salvos at Biscarosse (CEL) were carried out when the state of the lower ionosphere was within the range of normal (non-extremal) conditions. Various rocket salvos at Andoya took place on days of considerably different conditions in the lower ionosphere at higher mid-latitudes. Partial reflection measurements at Nizhny Novgorod show a clear tendency to a decrease of the electron density gradient between 70 and 80 km during March 1990.

Large-scale structures in hydroxyl rotational temperatures during DYANA

Comparison of nightly means of OH ∗ rotational temperatures measured at Yakutsk, Kiruna, Andoya, Biscarrosse, and El Arenosillo during the DYANA campaign reveals information about dynamics in the 86 km altitude region that includes relatively short-range temperature gradients at high latitudes associated with a stratospheric warming, and long-range oscillations with periods from about 2 to more than 30 days that can be attributed to travelling or quasi-stationary planetary waves. The DYANA campaign averages terrd to exceed zonal mean temperatures of the CIRA 86 model by up to 15 K.

Intercomparison of density and temperature profiles obtained by lidar, ionization gauges, falling spheres, datasondes and radiosondes during the DYANA campaign

During the course of the DYANA campaign in early 1990, various techniques to measure densities and temperatures from the ground up to the lower thermosphere were employed. Some of these measurements were performed near simultaneously (maximum allowed time difference: 1 h) and at the same location, and therefore offered the unique chance of intercomparison of different techniques. In this study, we will report on intercomparisons of data from ground-based instruments (Rayleigh- and sodium-lidar), balloon-borne methods (datasondes and radiosondes) and rocket-borne techniques (falling spheres and ionization gauges). The main result is that there is good agreement between the various measurements when considering the error bars. Only occasionally did we notice small but systematic differences (e.g. for the datasondes above 65 km). The most extensive intercomparison was possible between the Rayleigh lidar and the falling sphere technique, both employed in Biscarrosse (44°N,1°W). Concerning densities, excellent agreement was found below 63 km: the mean of the deviations is less than 1 % and the root mean square (RMS) is ~ 3%. Systematic differences of the order of 5% were noticed around 67 km and above 80 km. The former can be accounted for by an instrumental effect of the falling sphere (Ma = 1 transition; Ma = Mach number), whereas the latter is tentatively explained by the presence of Mie scatterers in the upper mesosphere. Concerning temperatures, the agreement is excellent between 35 and 65 km: the mean of the deviations is less than ± 3 K and the variability is ± 5 K. The two systematic density differences mentioned above also affect the temperatures: between 65 and 80 km, the Rayleigh lidar temperatures are systematically lower than the falling sphere values by ~ 5 K.

TOTAL: a rocket-borne instrument for high resolution measurements of neutral air turbulence during DYANA

An improved version of a rocket-borne instrument (‘TOTAL’), optimized for high resolution measurements of relative density variations, was successfully employed during the DYANA campaign in winter 1990. Both the inertial-convective subrange and the viscous-diffusive subrange of turbulence were observed in the power spectra derived from density fluctuations. An extended spectral model which comprises both subranges has been used to analyse the data. In this paper we present altitude profiles of turbulent parameters, such as turbulent energy dissipation rates ε and turbulent diffusion coefficients K, which were derived from a total of eight successfully launched instruments at high (Andoya, 69°N) and middle (Biscarosse, 44°N) latitudes. The limitations of the measurement technique as well as instrumental errors are discussed. The results mainly show small values of ε and K throughout the whole campaign period. The turbopause was found at an altitude of 95 ± 3 km.