Long-term mean vertical velocity measured by MST radar at Gadanki (13.5° N, 79.2° E)
Rao, P. V.
Vinay Kumar, P.
Ajay Kumar, M. C.
MST radars are capable of measuring vertical motion along
a vertically directed beam. We present 8 years (1995–2003) averaged profile
of vertical velocity in the troposphere and the lower stratosphere over
Gadanki (13.5° N, 79.2° E), a tropical station. A downward
mid-tropospheric <I><span style="border-top: 1px solid #000; color: #000;">w</span></I> is observed with a reversal of sign around 10 km
and a further reversal can also be seen at ~17 km. A significant
diurnal and semidiurnal variation in vertical wind is observed for all
heights with subsidence during the evening hours. Seasonal variability of
vertical wind is also found to be quite appreciable. Vertical velocities
have been derived using symmetric pairs of off-vertical beams and a
comparison has been made with direct vertical beam measurements. Vertical
components estimated from E-W and N-S radial velocities do not match and are
also found to have discrepancy with direct measurements. Plausible causes of
the discrepancy have been investigated with the help of some case studies.
Vertical shear in horizontal wind, gradients in horizontal velocities and
echo power imbalance may be some of the factors responsible for the observed