P. Mukhtarov

Planetary waves in coupling the stratosphere and mesosphere during the major stratospheric warming in 2003/2004

[1] The vertical coupling of the stratosphere-mesosphere system through quasi-stationary and traveling planetary waves during the major sudden stratospheric warming (SSW) in the Arctic winter of 2003/2004 has been studied using three types of data. The UK Met Office (UKMO) assimilated data set was used to examine the features of the global-scale planetary disturbances present in the winter stratosphere of the Northern Hemisphere. Sounding the Atmosphere using Broadband Emission Radiometry (SABER) satellite measurements were used as well for extracting the stationary planetary waves in the zonal and meridional winds of the stratosphere and mesosphere. Radar measurements at eight stations, four of them situated at high latitudes (63–69N) and the other four at midlatitudes (52–55N) were used to determine planetary waves in the mesosphere-lower thermosphere (MLT). The basic results show that prior to the SSW, the stratospheremesosphere system was dominated by an upward and westward propagating � 16-day wave detected simultaneously in the UKMO and MLT zonal and meridional wind data. After the onset of the SSW, longer-period (� 22–24 days) oscillations were observed in the zonal and meridional MLT winds. These likely include the upward propagation of stationary planetary waves from below and in situ generation of disturbances by the dissipation and breaking of gravity waves filtered by stratospheric winds. Citation: Pancheva, D., et al. (2008), Planetary waves in coupling the stratosphere and mesosphere during the major stratospheric warming in 2003/2004, J. Geophys. Res., 113, D12105, doi:10.1029/2007JD009011.

Strong evidence for the tidal control on the longitudinal structure of the ionospheric F‐region

This paper presents for the first time the global latitude structure and seasonal variability of the ionospheric response to the forced from below DE3 and DE2 tides during the period of time January 2008–March 2009. The COSMIC hmF2 and SABER temperature data have been utilized in order to define the ionospheric DE3 and DE2 tidal response to the DE3 and DE2 temperature tides propagating from below. The COSMIC DE3 and DE2 hmF2 tidal oscillations are derived by the same method as the tides seen the SABER temperatures. It has been shown that the longitude wave-4 and wave-3 hmF2 structures observed respectively in September and May 2008 are forced mainly by DE3 (wave-4) and DE2 (wave-3) temperature tides coming from below. The longitude wave-3 hmF2 structure observed in January 2008 however is forced by the combined action of the DE2 temperature tide coming from below and the SPW3 probably generated in-situ.

Atmospheric Tides and Planetary Waves: Recent Progress Based on SABER/TIMED Temperature Measurements (2002–2007)

The present paper is focused on the global spatial (altitude and latitude) structure, seasonal and interannual variability of the atmospheric tides (migrating and nonmigrating) and planetary waves (stationary and zonally traveling) derived from the SABER/TIMED temperature measurements for full 6 years (January 2002–December 2007). The mean wave amplitudes and phases are presented for the latitude range 50°N–50°S and from the lower stratosphere to the lower thermosphere (20–120 km). The main advantage of the results presented in this paper is that the migrating and nonmigrating tides as well as all significant planetary waves found in the SABER/TIMED temperatures are extracted simultaneously from the raw data (downloaded from the SABER web site temperatures). Therefore, using the same analysis techniques and the same data set makes it possible to get a consistent picture of the wave activity in the stratosphere-mesosphere-lower thermosphere system. Concerning the atmospheric tides, in addition to the migrating diurnal and semidiurnal tides the following nonmigrating tides also received significant attention: diurnal eastward propagating with zonal wavenumbers 2 and 3 and westward propagating with zonal wavenumber 2 and semidiurnal westward propagating with zonal wavenumber 3 and eastward propagating with zonal wavenumbers 2 and 3. A special attention is paid to the climatology and interannual variability of the temperature SPW1 and its origin in the lower thermosphere, as well as for following zonally propagating planetary waves: the ~5-day Rossby wave; ~6-day Kelvin wave, the ~10-day W1 wave and ~16-day W1 wave. The presented detailed picture of the spatial (altitude, latitude) structure and temporal variability of the considered atmospheric tides and planetary waves can serve as a benchmark and guide for future numerical modeling studies aimed at better understanding the stratosphere-mesosphere-lower thermosphere coupling by tidal and planetary wave patterns.

A Single-Station Spectral Model of the Monthly Median foF2 and M(3000)F2

A new single-station model (SSM) for monthly median values of the ionospheric parameters foF2 and M(3000)F2 has been developed. Fourier analysis provides a tool for decomposing the time-varying ionospheric parameters. The 12–month smoothed sunspot number R12was used as an external solar characteristic because of its availability and predictability. However, for the first time, the solar activity is described not only by R12, but also by the linear coefficient KRrepresenting the tendency of the change of solar activity. A general non-linear approximation of the influence of the solar-cycle characteristics R12and KRand ionospheric parameters foF2 and M(3000)F2 was accepted. The new SSM is applied to several European stations and its statistical evaluation shows better results than the other two SSMs used in the paper. The approach described in the paper does not contradict the use of different synthetic ionospheric indices (as the T-index, MF2–index); the basic aim is to show only that using one additional new characteristic of the solar-cycle variations, such as KR, improves the monthly median model.

Global distribution and variability of quasi 2 day waves based on the NOGAPS-ALPHA reanalysis model

This study presents the analysis of 14 months (January 2009–February 2010) of continuous hourly NOGAPS-ALPHA reanalysis data used for examining the quasi-2-day wave (OTDW). The global structure and seasonal variability of the eastward- and westward-traveling QTDWs in all meteorological fields (geopotential height, zonal and meridional wind and temperature) have been studied. The use of hourly reanalysis data allows a comprehensive understanding of the global spatial-temporal QTDW distribution by simultaneous separations of all tides and planetary waves. The wave characteristics (amplitudes and phases) are presented in latitude range ±80° and altitudes from 15 to 95 km. Two different types of eastward-traveling waves are identified: (i) waves at middle and high latitudes with zonal wave numbers 2 and 3, which are observed in the local winters, and (ii) waves observed predominantly over the equator with zonal wave number 2, which do not have a well-defined seasonal variability but show some enhancement between June and August. While the first type waves are seen in all meteorological fields, the second ones are not seen in the meridional wind and belong to the ultra-fast Kelvin waves. Two different types of westward-traveling waves have been identified as well: (i) waves at middle and high latitudes with zonal wave numbers 2, 3 and 4, which are observed mainly in summer hemisphere, and (ii) waves observed predominantly over the equator with zonal wave numbers 1, 2 and 3, enhanced predominantly at both solstices but are seen in other seasons as well. While the first type waves are seen in all meteorological fields the second ones are observed in the meridional wind and are Rossby-gravity normal modes.

QBO modulation of traveling planetary waves during northern winter

[1] This study analyzes geopotential height data from the ERA-40 and ERA-Interim reanalyses for the period of 1958–2009 to provide some new insights on the stratospheric Quasi-Biennial Oscillation (QBO) modulation of traveling planetary waves during Northern Hemisphere (NH) winter. In the stratosphere, the zonal wave number 1–3 waves with periods of 22.5–30 days and 45–60 days are found to be significantly stronger at midlatitudes when the QBO at 50 hPa is in its westerly phase than when it is in its easterly phase. The modulation is stronger for eastward propagating and standing waves and weaker for westward propagating waves. A QBO modulation of 11–13 day planetary waves is also found but the effect is dominated by post-satellite data. In the troposphere, significant QBO modulation is only detected in westward propagating waves at zonal wave number 2 with periods of 22.5–30 days in early winter (Oct-Dec). Consistent results in the stratosphere are obtained using the temperature data from SABER/TIMED. The SABER data also show that the QBO effect on the eastward propagating 23-day waves extends into the mesosphere (70 km) for wave number 1 and only up to the stratopause (45 km) for wave numbers 2 and 3. We suggest that the 22.5–30 day planetary waves are secondary waves generated by a nonlinear coupling between zonal-mean intraseasonal oscillations (ISO) and the well-known 16-day planetary waves. The QBO modulation of those planetary waves is due to a QBO-ISO interaction. Further studies are needed to prove this hypothesis.

Nonmigrating tidal variability in the SABER/TIMED mesospheric ozone

This paper presents for the first time evidence showing nonmigrating tidal variations in the mesospheric ozone (O3) derived from the Sounding of the Atmosphere using Broadband Emission Radiometry/Thermosphere-Ionosphere-Mesosphere-Energetics and Dynamics (SABER/TIMED) for a full 11 year period, 2002–2012. The O3 tidal fields are extracted from the data by the same method as the temperature tides have been derived. The spatial distribution and seasonal variability of the three strongest nonmigrating O3 tidal variabilities, i.e., SW3, DW2, and DE3, are shown. They demonstrate repeatable presence each year. These O3 tidal variations have large amplitudes at the seasons and latitudes for which the respective temperature (T) tides amplify, i.e., near the equator and during the equinoxes. The phases of the T and O3 tidal signatures are out of phase above 95 km. This phase relationship no longer holds for tidal perturbations below about 90 km. The O3 SW3 and DW2 tidal variations have similar interannual variabilities that appear to follow El Nino–Southern Oscillation variability. The O3 DE3 tidal field, however, has a clear biyearly interannual variability as the biyearly maxima correlate with the westerly phase of the quasi-biennial oscillation in tropical stratospheric winds but only up to 2008.

Observed Response of the Ionospheric F2–Layer and Lower Thermosphere to Geomagnetic Storms during High Solar Activity

The response of the critical frequency of the ionosphere F2–layer, described by its main Fourier components (daily constant, “diurnal” and “semidiurnal waves”) and the lower thermosphere dynamics to the geomagnetic storms in July 1991 and February 1992 is studied. The daily constant displays a negative response, however, the magnitude of reaction depends on the season and latitude. The amplitudes of “diurnal” and “semidiurnal waves” increase during a geomagnetic storm, as this enhancement is very strong at high latitudes in winter. The prevailing neutral wind, especially the zonal wind, shows an inclination to decrease during the geomagnetic storm (the effect is more distinct in summer). The amplitudes of diurnal and semidiurnal tides also demonstrate a tendency toward reduction during high geomagnetic activity.

A diurnal asymmetry of the monthly median E-region critical freouency

Abstract Distinct differences in the morning/afternoon variation of foE appear from a detailed model based on data of our ionosonde station Sofia.