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- ItemStudy of the tidal variations in mesospheric temperature at low and mid latitudes from WINDII and potassium lidar observations(Göttingen : Copernicus GmbH, 2004) Shepherd, M.; Fricke-Begemann, C.Zonal mean daytime temperatures from the Wind Imaging Interferometer (WINDII) on the Upper Atmosphere Research Satellite (UARS) and nightly temperatures from a potassium (K) lidar are employed in the study of the tidal variations in mesospheric temperature at low and mid latitudes in the Northern Hemisphere. The analysis is applied to observations at 89 km height for winter solstice, December to February (DJF), at 55° N, and for May and November at 28° N. The WINDII results are based on observations from 1991 to 1997. The K-lidar observations for DJF at Kühlungsborn (54° N) were from 1996-1999, while those for May and November at Tenerife 28° N were from 1999. To avoid possible effects from year-to-year variability in the temperatures observed, as well as differences due to instrument calibration and observation periods, the mean temperature field is removed from the respective data sets, assuming that only tidal and planetary scale perturbations remain in the temperature residuals. The latter are then binned in 0.5 h periods and the individual data sets are fitted in a least-mean square sense to 12-h and 8-h harmonics, to infer semidiurnal and terdiurnal tidal parameters. Both the K-lidar and WINDII independently observed a strong semidiurnal tide in November, with amplitudes of 13 K and 7.4 K, respectively. Good agreement was also found in the tidal parameters derived from the two data sets for DJF and May. It was recognized that insufficient local time coverage of the two separate data sets could lead to an overestimation of the semidiurnal tidal amplitude. A combined ground-based/satellite data set with full diurnal local time coverage was created which was fitted to 24 h+ 12 h+8 h harmonics and a novel method applied to account for possible differences between the daytime and nighttime means. The results still yielded a strong semidiurnal tide in November at 28° N with an amplitude of 8.8 K which is twice the SD amplitude in May and DJF. The diurnal tidal parameters were practically the same at 28° N and 55° N, in November and DJF, respectively, with an amplitude of 6.5 K and peaking at ∼9h. The diurnal and semidiurnal amplitudes in May were about the same, 4 K, and 4.6 K, while the terdiurnal tide had the same amplitudes and phases in May and November at 28° N. Good agreement is found with other experimental data while models tend to underestimate the amplitudes.
- ItemFirst observations of noctilucent clouds by lidar at Svalbard, 78° N(München : European Geopyhsical Union, 2003) Höffner, J.; Fricke-Begemann, C.; Lübken, F.-J.In summer 2001 a potassium lidar was installed near Longyearbyen (78° N) on the north polar island of Spitsbergen which is part of the archipelago Svalbard. At the same place a series of meteorological rockets ("falling spheres", FS) were launched which gave temperatures from the lower thermosphere to the stratosphere. The potassium lidar is capable of detecting noctilucent clouds (NLCs) and of measuring temperatures in the lower thermosphere, both under daylight conditions. In this paper we give an overview on the NLC measurements (the first at this latitude) and compare the results with temperatures from meteorological rockets which have been published recently (Lübken and Mülleman, 2003) NLCs were observed from 12 June (the first day of operation) until 12 August when a period of bad weather started. When the lidar was switched on again on 26 August, no NLC was observed. The mean occurrence frequency in the period 12 June -- 12 August ("lidar NLC period") is 77%. The mean of all individual NLC peak altitudes is 83.6 km (variability: 1.1 km). The mean peak NLC altitude does not show a significant variation with season. The average top and bottom altitude of the NLC layer is 85.1 and 82.5 km, respectively, with a variability of ~1.2 km. The mean of the maximum volume backscatter coefficient bmax at our wavelength of 770 nm is 3.9 x 10-10/m/sr with a large variability of ±3.8 x 10-10/m/sr. Comparison of NLC characteristics with measurements at ALOMAR (69° N) shows that the peak altitude and the maximum volume backscatter coefficient are similar at both locations but NLCs occur more frequently at higher latitudes. Simultaneous temperature and NLC measurements are available for 3 flights and show that the NLC layer occurs in the lower part of the height range with super-saturation. The NLC peak occurs over a large range of degree of saturation (S) whereas most models predict the peak at S = 1. This demonstrates that steady-state considerations may not be applicable when relating individual NLC properties to background conditions. On the other hand, the mean variation of the NLC appearance with height and season is in agreement with the climatological variation of super-saturation derived from the FS temperature measurements.
- ItemTemperature lidar measurements from 1 to 105 km altitude using resonance, Rayleigh, and Rotational Raman scattering(München : European Geopyhsical Union, 2004) Alpers, M.; Eixmann, R.; Fricke-Begemann, C.; Gerding, M.; Höffner, J.For the first time, three different temperature lidar methods are combined to obtain time-resolved complete temperature profiles with high altitude resolution over an altitude range from the planetary boundary layer up to the lower thermosphere (about 1–105 km). The Leibniz-Institute of Atmospheric Physics (IAP) at Kühlungsborn, Germany (54° N, 12° E) operates two lidar instruments, using three different temperature measurement methods, optimized for three altitude ranges: (1) Probing the spectral Doppler broadening of the potassium D1 resonance lines with a tunable narrow-band laser allows atmospheric temperature profiles to be determined at metal layer altitudes (80–105 km). (2) Between about 20 and 90 km, temperatures were calculated from Rayleigh backscattering by air molecules, where the upper start values for the calculation algorithm were taken from the potassium lidar results. Correction methods have been applied to account for, e.g. Rayleigh extinction or Mie scattering of aerosols below about 32 km. (3) At altitudes below about 25 km, backscattering in the Rotational Raman lines is strong enough to obtain temperatures by measuring the temperature dependent spectral shape of the Rotational Raman spectrum. This method works well down to about 1 km. The instrumental configurations of the IAP lidars were optimized for a 3–6 km overlap of the temperature profiles at the method transition altitudes. We present two night-long measurements with clear wave structures propagating from the lower stratosphere up to the lower thermosphere.