Abstract:
Medium Frequency (MF) radar located at Kolhapur (16.8 N, 74.2 E) has been upgraded in August 2013. Since
then continuous measurements of zonal and meridional winds are obtained covering larger altitudes from the
Mesosphere and Lower Thermosphere (MLT) region. Diurnal, monthly and seasonal variation of these mean winds
is presented in this study using four years (2013–2017) of observations. The percentage occurrence of radar
echoes show maximum between 80 and 105 km. The mean meridional wind shows Annual Oscillation (AO)
between 80 and 90 km altitudes with pole-ward motion during December solstice and equatorial motion during
June solstice. Quasi-biennial oscillation (QBO) with weaker amplitudes are also observed between 90 and
104 km. Zonal winds show semi-annual oscillation (SAO) with westward winds during equinoxes and eastward
winds during solstices between 80 and 90 km. AO with eastward winds during December solstice and westward
wind in the June solstice is also observed in the mean zonal wind between 100 and 110 km. These results match
well with that reported from other latitudes within Indian region between 80 and 90 km. However, above 90 km
the results presented here provide true mean background winds for the first time over Indian low latitude region
as the present station is away from equatorial electro-jet and are not contaminated by ionospheric processes.
Further, the results presented earlier with an old version of this radar are found contaminated due to unknown
reasons and are corrected in the present work. This upgraded MF radar together with other MLT radars in the
Indian region forms unique network to investigate the vertical and lateral coupling.
