Abstract. Turbulence parameters in the tropo-stratosphere are analyzed using high-resolution balloon temperature measurements collected during the MUTSI (MU radar, Temperature sheets and Interferometry) campaign which took place near the Middle and Upper atmosphere (MU) radar (Japan, 35 • N, 136 • E) in May 2000. Vertical profiles of the specific dissipation rate of turbulent kinetic energy, ε, and turbulent diffusivity, K, are estimated from the Thorpe lengthscale, L T . The last is obtained by using two methods. The first one consists of measuring directly L T by reordering the potential temperature profiles. The second method is based on estimates of the temperature structure constant, C 2 T . A relationship between L T and C 2 T can be found by assuming either adiabatic vertical displacements or a model based on turbulent energy balance consideration. Analysis shows that the adiabatic assumption gives indirect estimates of L T more consistent with direct measurements. We also found that vertical profiles of analyzed turbulence characteristics show substantial intermittency, leading to substantial scatter of the local, median and average values. General trends correspond to a decrease in ε and K from the boundary layer up to altitudes 20-25 km. Layers of increased turbulence are systematically observed in the tropo-stratosphere, which may be produced by instabilities of temperature and wind profiles. These maxima may substantially increase local values of turbulence diffusivity.

An experimental and theoretical investigation of the air trapping by a blunt, locally spherical body impacting onto the free surface of water is conducted. In the parameter regime previously studied theoretically by Hicks & Purvis (J. Fluid Mech., vol. 649, 2010, pp. 135–163), excellent agreement between experimental data and theoretical modelling is obtained. Earlier predictions of the radius of the trapped air pocket are confirmed. A boundary element method is used to consider air cushioning of an impact of an axisymmetric body into water. Efficient computational methods are obtained by analytically integrating the boundary integral equation over the azimuthal variable. The resulting numerically computed free-surface profiles predict an annular touchdown region in excellent agreement with the experiments.

A statistical procedure is developed to obtain the parameters of spectral harmonics of internal gravity waves (IGW) with horizontal wavelengths larger than ~ 60 km using measurements of wind velocity in the middle atmosphere from the middle and upper atmosphere (MU) radar. The method is applied to find sets of IGW parameters for the winter and summer seasons of 1987-1988 for 6-km-thick layers centered at 70, 75, and 80 km at Shigaraki, Japan (34.9øN, 139.4øE). The numbers of selected IGW harmonics having periods from 5 min up to 6 hours vary between 360 and 2000 depending on the season and altitude. Mean vertical wave numbers are 0.6-0.9 km -• in winter and 0.5-1 km -• in summer, and horizontal wave numbers are (3-4)x10 -2 km -• and (2-4)x10 -2 km -•, respectively. Predominant azimuths of wave vectors and momentum fluxes concentrate near 640 in winter and 900 in summer at all altitudes. In general, the difference between the azimuths of the wave vector and momentum flux is close to zero or 1800 . Turbulent and instrumental noise can contribute 20-30% of the observed intensity of the wind variations at altitudes of 70-85 km. The IGW momentum fluxes are 0.2-2.7 m•s -: in winter and 0.2-1.9 m:s -• in summer. The wave drag of the mean flow is 0.5-45 m2s -• in winter and 2-25 m2s -• in summer. In most cases the momentum flux and wave drag are directed oppositely to the mean wind. 1. 1976; Reid and Vincent, 1987; Gardner and Voe!z, 1987; Gavrilov and Kalov, 1987; Kashcheyev and Oleynikov, 1994], directions of IGW propagation [Frills and Vin-Unfortunately, most experiments are not able to measure all IGW parameters simultaneously. Also, IGW characteristics are usually obtained for a relatively broad range of frequencies or for cases when one IGW harmonic dominates over others, and visual inspection reveals clear wavelike structures or quasi-elliptical wind hodographs.In this paper we reevaluate the methods used to determine IGW characteristics and modify them to obtain parameters for each spectral harmonic of the complicated noisy wave spectrum present in the atmosphere. Formulae are obtained that allow the calculation of the parameters of IGW harmonics using measurements of wind velocity in the middle atmosphere with the MU radar in five directions of the antenna beam (one vertical and four inclined to the north, west, south, and east from zenith). The statistical method includes spectral analysis of the data for the five directions of the antenna beam, calculation of the axes and the tilt angle of the velocity hodograph ellipse, amplitudes and momentum flux, vertical and horizontal wave numbers, and azimuths of wave vector and momentum flux for each spectral harmonic. Spectra of wind variations in the middle and upper atmosphere are very complicated, and may include (in addition to IGWs) harmonics caused by turbulence, trapped waves, impacts of solar events, etc. Spectral analysis of short data series is notorious for giving "computational" peaks of spectral density that do not exist in nature (see, for example, Gavri...

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