The marine atmospheric boundary layer (MABL) plays a vital role in the transport of momentum and
heat from the surface of the ocean into the atmosphere. A detailed study on the MABL characteristics was
carried out using high-resolution surface-wind data as measured by the QuikSCAT (Quick scatterometer)
satellite. Spatial variations in the surface wind, frictional velocity, roughness parameter and drag coe±cient
for the di®erent seasons were studied. The surface wind was strong during the southwest monsoon season
due to the modulation induced by the Low Level Jetstream. The drag coe±cient was larger during this
season, due to the strong winds and was lower during the winter months. The spatial variations in the
frictional velocity over the seas was small during the post-monsoon season (»0.2 m s¡1). The maximum
spatial variation in the frictional velocity was found over the south Arabian Sea (0.3 to 0.5 m s¡1) during
the southwest monsoon period, followed by the pre-monsoon over the Bay of Bengal (0.1 to 0.25 m s¡1).
The mean wind-stress curl during the winter was positive over the equatorial region, with a maximum value
of 1.5£10¡7 N m¡3, but on either side of the equatorial belt, a negative wind-stress curl dominated. The
area average of the frictional velocity and drag coe±cient over the Arabian Sea and Bay of Bengal were also
studied. The values of frictional velocity shows a variability that is similar to the intraseasonal oscillation
(ISO) and this was con¯rmed via wavelet analysis. In the case of the drag coe±cient, the prominent
oscillations were ISO and quasi-biweekly mode (QBM). The interrelationship between the drag coe±cient
and the frictional velocity with wind speed in both the Arabian Sea and the Bay of Bengal was also studied.
Description:
ADVANCES IN ATMOSPHERIC SCIENCES, VOL. 24, NO. 4, 2007, 631{643