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The role of dense coconut palms in attenuating the wind speed at Kavaratti Island, which is located in the southeastern
Arabian Sea, is examined based on land-based and offshore wind measurements (U10) using anchored-buoy-mounted and
satellite-borne sensors (QuikSCAT scatterometer and TMI microwave imager) during an 8-year period (2000-2007). It is
found that round the year monthly-mean wind speed measurements from the Port Control Tower (PCT) located within
the coconut palm farm at the Kavaratti Island are weaker by 15-61% relative to those made from the nearby offshore
region. Whereas wind speed attenuation at the island is ~15-40% in the mid-June to mid-October south-west monsoon
period, it is ~41-61% during the rest of the year. Wind direction measurements from all the devices overlapped, except in
March-April during which the buoy measurements deviated from the other measurements by ~20°. U10 wind speed
measurements from PCT during the November 2009 tropical cyclone "Phyan" indicated approximately 50-80%
attenuation relative to those from the seaward boundary of the island's lagoon (and therefore least influenced by the
coconut palms). The observed wind speed attenuation can be understood through the theory of free turbulent flow jets
embodied in the boundary-layer fluid dynamics, according to which both the axial and transverse components of the
efflux of flows discharged through the inter-leaves porosity (orifice) undergo increasing attenuation in the downstream
direction with increasing distance from the orifice. Thus, the observed wind speed attenuation at Kavaratti Island is
attributable to the decline in wind energy transmission from the seaward boundary of the coconut palm farm with
distance into the farm. Just like mangrove forests function as bio-shields against forces from oceanic waves and stormsurges
through their large above-ground aerial root systems and standing crop, and thereby playing a distinctive role in
ameliorating the effects of catastrophies such as hurricanes, tidal bores, cyclones, and tsunamis, the present study
provides an indication that densely populated coconut palms and other tall tree vegetation would function as bio-shields
against the damaging effects of storms through attenuation of wind speed.
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