Statistical distribution of wind directions observed by QuikSCAT/SeaWinds

In order to validate wind vectors derived from QuikSCAT (QSCAT)/SeaWinds, statistical distributions of wind directions are investigated by comparison with those from numerical weather prediction (NWP) wind analyses. Frequency distribution of wind directions relative to spacecraft flight direction is calculated from the QSCAT data for a period of three months to assess the self-consistency of the wind directions. It is found that the QSCAT wind vectors exhibit systematic directional preference relative to antenna beams, which is very similar to that found in the NSCAT winds. Sharp spikes are discernible in the directional distributions and azimuth location of the spikes varies with cross-track cell location reflecting azimuth angle combinations of scatterometer beams. It is expected that the artificial directivities are considered to be caused by imperfections in the NSCAT-2 geophysical model function