Main topics

 

The main scientific reasons to extend the study of neutral winds up to an altitude of about 120 km are:

1. Study of semi- and terdiurnal tidal waves over an extended altitude range. These waves have their maxima at altitudes above ~100 km, where they have the strongest influence on the background mean winds. Detailed tasks concerning the wind observations are directed to:

+ identify periods with ionospheric conditions which allow the derivation of neutral winds in the lower thermosphere from the EISCAT radars in order to get a good data coverage,

+ compare and combine MF/MR winds and neutral winds in the lower thermosphere,

+ investigate atmospheric tidal waves in both data sets in comparison with circulation models,

+ investigate tidal variations in water vapor and ozone in the upper stratosphere as measured by microwave radiometry as possible sources of tidal waves and to compare them to the tidal waves in the mesosphere and lower thermosphere,

+ compare the results for different averaging intervals with the results of the TIDI experiment onboard the TIMED satellite,

+ examine characteristics of planetary wave structures in the derived data set and in comparison with ISR- and mesospheric radar winds over Northern America.

 

2. Investigation of vertical propagation of waves and their impact on the dynamical and thermal structure in the lower thermosphere. Of particular interest are coupling processes such as sudden stratospheric warming events during winter which significantly affect all atmospheric layers, To improve our understanding of the mesosphere-lower thermosphere response to SSW, detailed tasks are directed to:

+ measure neutral wind (zonal and meridional components) and electron and ion temperatures in the lower thermosphere before and during sudden stratospheric warming,

+ investigate variations in temperature and winds in relation to average variations observed by the EISCAT radars during the winter, compare these results to similar measurements from other incoherent Scatter radars (Millstone Hill, Sondrestrom, Poker Flat, ...)

+ compare variations in temperatures and winds to the mesospheric response as given by MF and meteor radars (Singer et al., 2004)

+ investigate variations in water vapor and ozone in the upper stratosphere and lower mesosphere as measured by microwave radiometry during SSW and to compare them to the variations in the mesosphere and lower thermosphere,

+ extend studies of stratospheric warming effects to the lower thermosphere and investigate possible coupling with the ionosphere,

+ investigate possible time lags between  wind and temperature changes in the mesosphere and lower thermosphere with changes in the troposphere and lower stratosphere,

+ examine the mechanisms responsible for variations in lower thermospheric dynamics and temperatures and investigate to what degree they can be related to SSW.

 

In addition to tidal variations, at altitudes above 100 km there is a stronger response of solar events on winds and temperatures in the mesosphere and lower thermosphere. A particular task is to evaluate quantitatively how the atmosphere in the MLT region is influenced by the ion drag and particle precipitations.