From 19 November to 19 December 2010 the fourth and final ECOMA rocket campaign was conducted at Andøya Rocket Range (69° N, 16° E) in northern Norway. We present and discuss measurement results obtained during the last rocket launch labelled ECOMA09 when simultaneous and true common volume in situ measurements of temperature and turbulence supported by ground-based lidar observations reveal two Mesospheric Inversion Layers (MIL) at heights between 71 and 73 km and between 86 and 89 km. Strong turbulence was measured in the region of the upper inversion layer, with the turbulent energy dissipation rates maximising at 2 W kg⁻¹. This upper MIL was observed by the ALOMAR Weber Na lidar over the period of several hours. The spatial extension of this MIL as observed by the MLS instrument onboard AURA satellite was found to be more than two thousand kilometres. Our analysis suggests that both observed MILs could possibly have been produced by neutral air turbulence

Abstract. In summer 2013 the WADIS-1 sounding rocket campaign was conducted at the Andøya Space Center (ACS) in northern Norway (69 • N, 16 • E). Among other things, it addressed the question of the variability in mesosphere/lower thermosphere (MLT) turbulence, both in time and space. A unique feature of the WADIS project was multi-point turbulence sounding applying different measurement techniques including rocket-borne ionization gauges, VHF MAARSY radar, and VHF EISCAT radar near Tromsø. This allowed for horizontal variability to be observed in the turbulence field in the MLT at scales from a few to 100 km. We found that the turbulence dissipation rate, ε varied in space in a wavelike manner both horizontally and in the vertical direction. This wavelike modulation reveals the same vertical wavelengths as those seen in gravity waves. We also found that the vertical mean value of radar observations of ε agrees reasonably with rocket-borne measurements. In this way defined ε radar value reveals clear tidal modulation and results in variation by up to 2 orders of magnitude with periods of 24 h. The ε radar value also shows 12 h and shorter (1 to a few hours) modulations resulting in one decade of variation in ε radar magnitude. The 24 h modulation appeared to be in phase with tidal change of horizontal wind observed by SAURA-MF radar. Such wavelike and, in particular, tidal modulation of the turbulence dissipation field in the MLT region inferred from our analysis is a new finding of this work.

Abstract. The ECOMA sounding rocket campaign in 2010 was performed to investigate the charge state and number density of meteoric smoke particles during the Geminids meteor shower in December 2010. The ALOMAR Na lidar contributed to the campaign with measurements of sodium number density, temperature and line-of-sight wind between 80 and 110 km altitude over Andøya in northern Norway. This paper investigates a possible connection between the Geminids meteor shower and the mesospheric sodium layer. We compare with data from a meteor radar and from a rocketborne in situ particle instrument on three days. Our main result is that the sodium column density is smaller during the Geminids meteor shower than the winter average at the same latitude. Moreover, during two of the three years considered, the sodium column density decreased steadily during these three weeks of the year. Both the observed decrease of Na column density by 30 % and of meteoric smoke particle column density correlate well with a corresponding decrease of sporadic meteor echoes. We found no correlation between Geminids meteor flux rates and sodium column density, nor between sporadic meteors and Na column density (R = 0.25). In general, we found the Na column density to be at very low values for winter, between 1.8 and 2.6 × 10 13 m −2 . We detected two meteor trails containing sodium, on 13 December 2010 at 87.1 km and on 19 December 2010 at 84 km. From these meteor trails, we estimate a global meteoric Na flux of 121 kg d −1 and a global total meteoric influx of 20.2 t d −1 .

We present a new method for the derivation of gravity wave vertical wavelengths from OH airglow observations of different vibrational transitions. It utilizes small phase shifts regularly observed between the OH(3-1) and OH(4-2) intensities in the spectra of the GRIPS (GRoundbased Infrared P-branch Spectrometer) instruments, which record the OH airglow emissions in the wavelength range from 1.5µm to 1.6µm simultaneously. These phase shifts are interpreted as being due to gravity waves passing through the OH airglow layer and affecting individual vibrational transitions at slightly different times due to small differences in their emission heights. The results are compared with co-located observations of the OH(6-2) and O 2 b(0-1) transitions by means of spectrometer observations (TANGOO instrument, Tilting-filter spectrometer for Atmospheric Nocturnal Ground-based Oxygen & hydrOxyl emission measurements) performed from 2013 until 2016 at Oberpfaffenhofen (48.08° N, 11.27° E), Germany, and with Na-Lidar measurements acquired between 2010 and 2014 at the Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR, 69.28° N, 16.01° E), Norway. The latter comparison shows best agreement if the mean height difference of the OH(3-1) and OH(4-2) emission is assumed to be 540 m (1σ=160 m), confirming the result of von Savigny et al. (2012), who derived a height difference of approximately 500 m between each vibrational level. For approximately 40 % of all wave events observed with GRIPS, a quantitative estimate of the phase relationship between the OH(3-1) and OH(4-2) intensities can be retrieved from the spectra allowing derivation of vertical wavelengths. The retrieval performs best for wave periods below two hours (80 % success rate) and worse for periods above ten hours (successful in less than 10 % of the cases). The average wavelength determined from 102 events amounts to 22.9 km (1σ: 9.0 km).

Abstract. An algorithm has been developed for the retrieval of sodium atom (Na) number density on a latitude and altitude grid from SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) limb measurements of the Na resonance fluorescence. The results are obtained between 50 and 150 km altitude and the resulting global seasonal variations of Na are analyzed. The retrieval approach is adapted from that used for the retrieval of magnesium atom (Mg) and magnesium ion (Mg + ) number density profiles recently reported by Langowski et al. (2014). Monthly mean values of Na are presented as a function of altitude and latitude. This data set was retrieved from the 4 years of spectroscopic limb data of the SCIAMACHY mesosphere and lower thermosphere (MLT) measurement mode (mid-2008 to early 2012).The Na layer has a nearly constant peak altitude of 90-93 km for all latitudes and seasons, and has a full width at half maximum of 5-15 km. Small but significant seasonal variations in Na are identified for latitudes less than 40 • , where the maximum Na number densities are 3000-4000 atoms cm −3 . At middle to high latitudes a clear seasonal variation with a winter maximum of up to 6000 atoms cm −3 is observed. The high latitudes, which are only measured in the summer hemisphere, have lower number densities, with peak densities being approximately 1000 Na atoms cm −3 . The full width at half maximum of the peak varies strongly at high latitudes and is 5 km near the polar summer mesopause, while it exceeds 10 km at lower latitudes. In summer the Na atom concentration at high latitudes and at altitudes below 88 km is significantly smaller than that at middle latitudes. The results are compared with other observations and models and there is overall a good agreement with these.

I investigate the nightly mean emission height and width of the OH * (3-1) layer by comparing nightly mean temperatures measured by the ground-based spectrometer GRIPS 9 and the Na lidar at ALOMAR. The data set contains 42 coincident measurements between November 2010 and February 2014, when GRIPS 9 was in operation at the ALO-MAR observatory (69.3 • N, 16.0 • E) in northern Norway. To closely resemble the mean temperature measured by GRIPS 9, I weight each nightly mean temperature profile measured by the lidar using Gaussian distributions with 40 different centre altitudes and 40 different full widths at half maximum. In principle, one can thus determine the altitude and width of an airglow layer by finding the minimum temperature difference between the two instruments. On most nights, several combinations of centre altitude and width yield a temperature difference of ±2 K. The generally assumed altitude of 87 km and width of 8 km is never an unambiguous, good solution for any of the measurements. Even for a fixed width of ∼8.4 km, one can sometimes find several centre altitudes that yield equally good temperature agreement. Weighted temperatures measured by lidar are not suitable to determine unambiguously the emission height and width of an airglow layer. However, when actual altitude and width data are lacking, a comparison with lidars can provide an estimate of how representative a measured rotational temperature is of an assumed altitude and width. I found the rotational temperature to represent the temperature at the commonly assumed altitude of 87.4 km and width of 8.4 km to within ±16 K, on average. This is not a measurement uncertainty.

a b s t r a c tWe present a comparison of the temperature and sodium layer properties observed by the ALOMAR Na lidar (69.3°N, 16.0°E) and simulated by the Whole Atmosphere Community Climate Model with specified dynamics and implemented sodium chemistry (WACCM-Na). To constrain the meteorological fields below 60 km, we use MERRA and GEOS-5. For the years 2008 to 2012, we analyse daily averages of temperature between 80.5 km and 101.5 km altitude, and of the Na layer's peak height, peak density, and centroid height. Both model runs are able to reproduce the pronounced seasonal cycle of Na number density and temperature at high latitudes very well. Especially between 86.5 km and 95.5 km, the measured and simulated temperatures agree very well. The lidar measurements confirm the model predictions that the January 2012 stratospheric warming led to large variation in temperature and Na density. The correlation coefficient between Na number density and temperature is positive for almost all altitudes in the lidar data, but not in the simulations. On average, the centroid height and peak height measured by lidar is about 2 km-3 km higher than simulated by WACCM-Na.

Abstract. An algorithm has been developed for the retrieval of sodium atom (Na) number density on a latitude and altitude grid from SCIAMACHY limb measurements of the Na resonance fluorescence. The results are obtained between 50 and 150 km altitude and the resulting global seasonal variations of Na are analysed. The retrieval approach is adapted from that used for the retrieval of magnesium atom (Mg) and magnesium ion (Mg+) number density profiles recently reported by Langowski et al. (2014). Monthly mean values of Na are presented as a function of altitude and latitude. This data set was retrieved from the 4 years of spectroscopic limb data of the SCIAMACHY mesosphere and lower thermosphere (MLT) measurement mode. The Na layer has a nearly constant altitude of 90–93 km for all latitudes and seasons, and has a full width at half maximum of 5–15 km. Small but substantial seasonal variations in Na are identified for latitudes less than 40°, where the maximum Na number densities are 3000–4000 atoms cm−3. At mid to high latitudes a clear seasonal variation with a winter maximum of up to 6000 atoms cm−3 is observed. The high latitudes, which are only measured in the Summer Hemisphere, have lower number densities with peak densities being approximately 1000 Na atoms cm−3. The full width at half maximum of the peak varies strongly at high latitudes and is 5 km near the polar summer mesopause, while it exceeds 10 km at lower latitudes. In summer the Na atom concentration at high latitudes and at altitudes below 88 km is significantly smaller than that at mid latitudes. The results are compared with other observations and models and there is overall a good agreement with these.