Assessment of wave modeling results with buoy and altimeter deep water waves for a summer monsoon
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A second-generation offshore spectral wave model has been applied to simulate wind waves over the north Indian Ocean during May-August 2000 using 6 hourly NCEP re-analysis wind data. The significant wave height (SWH), wave period and mean wave direction derived from the model have been compared with moored buoy and TOPEX altimeter data. As the accuracy of simulated wave parameters depends on the accuracy of winds, the NCEP re-analysis winds have been compared with buoy winds and an assessment is made to this effect. The data of deepwater buoys off Goa, Kochi, and Chennai have been utilised for comparison. It is difficult to get sufficient collinear altimeter points with modelled output, and therefore, all the altimeter SWH values are organised in 0.75 degrees x 0.75 degrees size boxes and compared the average value in each grid with those of model output and buoy SWHs. Comparison of model and buoy wave parameters during the summer monsoon shows that model results agree closely with the buoy measurements (Example, for Kochi SWHs, bias = 0.888 and correlation coefficient (gamma) = 0.923). Higher winds, of the order of 15-18 m/s, off Goa and Kochi and 10-12 m/s off Chennai, and wave heights, of the order of 3.5-4.5 m observed during 5-7 June 2000 are due to a low-pressure system present at that time, and the model is quick in reflecting this rapid change, and it is a clear evidence of the model capability. Wave heights, in general, are higher in the Arabian Sea than the Bay of Bengal during June to August, but nearly the same in May.
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