Coherence of temporal variations (2-30 days) in the wind field of the midlatitude middle atmosphere of the Earth

Current work is dedicated to the investigation of the coherency between wave processes at heights of lower and middle atmospheres of the Earth in the field of background circulation. In this work the comparison between temporal variations of the wind velocity on heights of the mesosphere - lower thermospher (MLT) and on heights of the troposphere and the stratosphere is accomplished. For analysis we used data of wind measurements accomplished during 1986-2004 at meteor radar of Kazan University (56N, 49E). Also we used data of BADC UK MO1 containing wind velocity in nodes of the longitudinal - latitudinal grid (96×72). Data of BADC UK MO are exposed to the spatial filtering. This allowed time series of complex amplitude of spatial waves with wave numbers 1-8. Performed analysis of wind data by the coherency spectra between this time series and time series of the wind velocity for heights of MLT allowed the detection of wave trains with specific periods close to Rossby waves (2, 5, 10 days) and to long-period waves (15-30 days) with significant coherency between variation on different height levels. Height profiles of the coherency phase showed the propagation direction and vertical wave length of the corresponding wave trains. The work has been performed under the support of Ministry of Education of Russian Federation, grant A03-2.13-513

Interdependence of wave processes of zonal and meridional circulation of the middle atmosphere

The investigation of daily prevailing wind velocity variations with planetary wave time scales from 2 to 30 days are accomplished using radio meteor observations over Kazan (56N, 49E) in the height range 80-100 km and BADC UK MO data archive for heights 0-55 km (with coordinates of Kazan). Calculated coherency spectra between zonal and meridional prevailing wind velocity show the significant coherency for time scales 3-5 days and 10-30 days. Height range with significant coherency for certain frequency is larger than 7-10 km. Height profiles of the coherency phase indicate the time shift between variations of zonal and meridional winds with mentioned time scales

Wave interactions in midlatitude middle atmosphere of the Earth

Investigation of wave interactions in heights of the upper mesosphere - lower thermosphere is accomplished using time series of zonal and meridional winds. These time series are acquired in Kazan State University (56N, 49E) by radio meteor observations. Applied bispectral analysis shows expressed non-linier interactions of wave processes with tidal scales (12 and 24 hours) and planetary wave scales (so-called as normal Rossby modes with periods 5, 10, 16 days)

Rotational effects in the field of tidal wind of the mid-latitude MLT-Region

Investigation of non-linear effects in the approach of quadratic coupling of tidal motions and planetary waves with taking into consideration their polarization properties was carried out. The investigation was based on the wind observations performed by meteor radar station of Kazan State University (Russia, Kazan, 56N, 49E) in the MLT-region (80-100km) during 1998-1999 years. A complex approach is used to analyze non-linear interactions. It includes calculation of rotational autospectra of vectorial time series in the representation as complex u+i*v, where u and v is zonal and meridional winds correspondingly and 'i' is a complex unit. Autoregressive spectra show a stable clockwise rotation of the resulting vector of the tidal winds, quasi 2-day and quasi 4-day waves in spite of the presence of modulating effects by planetary waves at heights of the MLT-region. The spectral analysis of vectorial time series for tidal winds reveals side frequencies. These side frequencies appear as result of interactions of tides and quasi-2 day and quasi 4-day planetary waves and correspond to the interaction with consideration of their polarization properties. © 2003 COSPAR. Published by Elsevier Ltd. All rights reserved

Structure of rotational spectra of vectorial wave fields in the middle atmosphere

In this work the time spectra dynamics of zonal and meridional average daily values of wind velocity was investigated. An analysis is carried out using Atmospheric Assimilated Data acquired from British Atmosphere Data Center United Kingdom Met Office on the height range 0-55 km in the grid node correspondent to Kazan and experimental data of the wind velocity acquired by radio meteor measurements in radio meteor station of Kazan State University (56N, 49E) for height range 80-100 km. The seasonal structure of zonal circulation and planetary wave activity is established in the height range of the troposphere, the stratosphere, the mesosphere and the lower thermosphere using wavelet transformation and rotational spectra. An intensity of planetary waves has a stable maximum in the winter on heights above 20 km. The stable maximum of the intensity of planetary waves is observed in the height of the tropopause during the whole year. A regime of planetary waves with specific rotation of resulting wind velocity vector (clockwise and anticlockwise) appears on heights of the lower and middle atmosphere with the prevailing of a certain type of rotation depending on height, season and scale of planetary waves

Temporal and spatial rotational spectra of wind velocity variations with periods 2-40 days in lower and middle atmospheres of the Earth

Current work is dedicated to the investigation of temporal and spatial energy spectra of wave processes in the field of lower and middle atmospheres (0-100 km) of the Earth. For analysis we used data of wind measurements at heights 80-100 km performed at meteor radar in Kazan (56N, 49E). Also we used data of BADC UK MO containing wind velocity in nodes of the longitudinal - latitudinal grid (96×72) for the height range 0-55 km. Analysis of calculated temporal rotational energy is performed separately for time scales 2-7 days, 7-20 days and 20-40 days. At middle latitudes of Northen and Southen Hemispheres the change of the prevailing direction of the wind velocity rotation is detected. Established change of the prevailing rotation of the wind velocity vector at heights 0-100 km shows that these latitudes are in the region of active cyclonic and anticyclonic activity. Also we found that for middle and high latitudes of the Northen and Southen Hemispheres the planetary wave regime is specific as well as the regime of the geostrophic turbulence is specific for low latitudes and the equator. This result is acquired using the analysis of the spatial energy spectra for heights 0-55 km. The inclination of these energy spectra in the linier region with wave numbers 8-25 is [-6;-4] for middle and high latitudes (it corresponds to the planetary wave regime) and [-2;-1] for low latitudes and equator (it corresponds to the regime of the geostrophic turbulence)

Longitudinal variability of the zonal and meridional circulation and the intensity of planetary waves in the lower and middle atmosphere

Mesosphere/lower thermosphere wind data sets from three midlatitude sites and UKMO assimilated wind data in the height range 0-55 km at 55°N were used to show the altitudinal and longitudinal variability of mean winds and planetary waves at mid-latitudes during solstices. In spite of the existence of longitudinal differences of the prevailing winds and the annual and semiannual oscillations, certain common features of the zonal wind height profiles are visible in the height range 10-100 km. The maxima of the mean annual winds and of the intensities of the annual and semiannual oscillations occur near the stratopause. In the height range 80-100 km there is an increase in the annual mean winds and in the amplitudes of the annual and semiannual oscillations; also the semiannual oscillation is larger than the annual one. Minima of the annual/semiannual oscillation amplitudes at heights of 85-95/80-85 km are accompanied by corresponding phase changes of 180 degrees in relation to those values near the stratopause. The height structure of meridional wind parameters is more complicated, with dependences on longitude and height. Longitudinal variability in the intensity of planetary waves was also found. © 2003 COSPAR. Published by Elsevier Ltd. All rights reserved

Planetary wave activity and rotational effects in the mid-latitudes of the lower and middle atmosphere (0-100KM)

Investigation of the wind regime during solstices (1998-1999) allowed the presentation of the vertical structure of the intensity of planetary waves in the zonal and meridional wind. The seasonal dependence of the vertical structure of these planetary wave amplitudes is determined at middle atmosphere heights. Daily mesosphere/lower thermosphere (MLT) experimental data, measured at Collm (52N 15E, LF D1 radar), Kazan (56N 49E, meteor radar) and Saskatoon (52N 103W, MF radar) in the height range 80-100 km, and UKMO assimilated wind data from the British Atmospheric Data Center in the height range 0-55 km are used. In winter, maxima of the planetary wave intensity are observed near the tropopause and in the stratosphere. A decrease of the planetary wave intensity in the mesosphere coincides with the weakening of the stratospheric jet, and with the decay of the zonal flow in the mesosphere. Processes such as radiative suppression of planetary waves in the mesosphere and their additional reductions as a result of wave interactions and interactions with the zonal flow may explain these significant decreases of the intensity. Rotational spectra and estimates of rotational amplitudes in the height range of the middle atmosphere allow the investigation of the change of rotation direction of the horizontal wind vector dependent on height and period of the wave perturbations. © 2003 COSPAR. Published by Elsevier Ltd. All rights reserved

Wind regime of the mesosphere - Lower thermosphere of the Earth

Nowadays investigations of the wind regime of the mesosphere - lower thermosphere (80-100 km) using ground-based (including radiometeor method) and satellite measurements allow the setting and the decision of the task of the creation the global model of the circulation including background motions and temporal variability. The temporal variability is due to the wide spectrum of temporal and spatial scales of waves existing in the atmosphere. Radiosystem of Kazan University is one of 23 meteor radars operating currently in the World. Radiometeor wind measurements in Kazan University started in 1964. During the period of 1964-1965, the first annual cycle of observation is accomplished. Long cycles of observations accomplished during 1979-2002. Uninterrupted cycle of observations started in November 2002 allowed the detailed structure of the temporal variability in the region of the mesosphere - lower thermosphere. Modern methods of the analysis along with background motions allowed the detection of short-period (5-10 minutes) innergravity waves, tidal waves, planetary waves (2-30 days), seasonal variations (annual and semiannual oscillations). Dynamics of this height region of the atmosphere presents significant scientific and practical interests. Due to propagating from the lower atmosphere waves experience the dissipation and the filtration and affects to the altitudinal and seasonal structure of the circulation we should expect the affection of these waves to the disturbed structure of the ionosphere

Semi-empirical model of middle atmosphere wind from the ground to the lower thermosphere

During recent years, special attention has been paid to understanding the background circulation of the middle atmosphere. Particularly in the mesosphere/lower thermosphere (MLT) region, this has involved including data from a range of new radar measurements. It has also involved the comparison of existing empirical middle atmosphere wind models, such as CIRA-86 and HWM-93 to the new data. This has led to the construction of empirical models of MLT winds such as the Global Empirical Wind Model (GEWM). Further investigations are aimed at the construction of new empirical and semi-empirical wind models of the entire middle atmosphere including these new experimental results. The results of a new wind climatology (0-100 km) are presented here, based upon the GEWM, a reanalysis of stratospheric data, and a numerical model which is used to fill the gap between data from the stratospheric and MLT regions. © 2008 COSPAR