  We analyse the chromospheric Doppler velocity oscillations in a sunspot using
the high resolution spectral observations obtained from the Fast Imaging Solar
Spectrograph(FISS) of the New Solar Telescope at the Big Bear Solar
Observatory. The Doppler velocity maps are constructed from the bisectors of
the spectral observations. The time series analysis of Doppler velocity maps
show enhanced power in the sunspot umbra at higher frequencies and in the
penumbra at lower frequencies. We find that the peak power frequency decreases
gradually from the umbra to outward.
