Dr.Babu, C A; Hamza, V; Kunhikrishnan, P. K; Sabin, T P(January , 2007)
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Abstract:
The oscillations in the Atmospheric Boundary Layer (ABL) are important because the transport mechanism from
the surface to the upper atmosphere is governed by the ABL characteristics. The study was carried out using wind and
temperature data observed at surface, 925 hPa and 850 hPa levels over Cochin and the different frequencies embedded
in the boundary layer parameters are identified by employing wavelet technique. Surface boundary layer characteristics
over the monsoon region are closely linked to the upper layer monsoon features. In this perception it is important to
study the various oscillations in the surface boundary layer and the layer above. It is found that the wind and
temperature at different levels show oscillations in Quasi Biweekly Mode (QBM) and Intra Seasonal Oscillation (ISO)
bands as observed in a typical monsoon system. Amplitude of the oscillation varies with height. The amplitude of the
QBM periodicity is more in the surface levels but in the upper levels the amplitude of the ISO periodicity is more than
that of the QBM. From this, it is obvious that the controlling mechanism of QBM band is surface parameters such as
surface friction and that for ISO band is associated with the active-break cycles of monsoon system