On the Accuracy of Monthly Mean Wind Speeds over the Equatorial Pacific

Abstract

Yearlong in situ surface wind measurements at three sites along the Pacific equator (95°, 110°, 152°W) are used to estimate the required number of random observations per month for monthly mean wind speed components accurate to 1.0 and 0.5 m s?. The three-site average amplitude of wind speed fluctuations with time scales less than a month was 2.8 m s?, which was about 64% of the annual vector-mean speed. For the zonal (meridional) wind component, the average numbers of random observations at the three sites were about 10 (8) and 39 (30), respectively, for accuracies of 1.0 and 0.5 m s?. The number of random observations increased westward and was highly correlated (R = 0.97) with monthly mean standard deviations. Neglect of wind variations yields an approximate 50% underestimate of monthly mean wind stress computed from the square law and monthly mean wind components.