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Journal of Geophysical Research: Oceans

The measurement of the synoptic scale wind over the ocean

Authors

  • Willard J. Pierson Jr.


Abstract

Mesoscale and microscale features of the turbulent winds over the ocean are related to the synoptic xscale winds in terms of published spectral forms for the microscale, a mesoscale valley, and published values of u*, Var u′, Var v′, and z/L, as defined in the text and as obtained for moderate to gale force winds. The frequencies involved correspond to periods longer than 1 hour and extend to the microscale, which starts at a period near 2 min, or so, and continues to the Kolmogorov inertial range. Nondimensional spectra that span both the mesoscale and the microscale are derived as a function of u*,f/(=nz/ū), and z/L, where z is 10 m, L is the Monin-Obukhov stability length, and ū is evaluated at 10 m. For the same ū, different values of z/L produce a range of values of u* which in turn result in variations of the eddy structure of the mesoscale and microscale spectra. Both conventional anemometer averages and remotely sensed winds contain a random component of the mesoscale wind in their values. These components are differences and not ‘errors’ when winds are compared, and quantitative values for these differences are given. Ways to improve the measurement of the synoptic scale wind by transient ships, data buoys, and scatterometers on future spacecraft are described. These ways are longer averaging times for ships and data buoys, depending on the synoptic conditions, and pooling spacecraft data to form superobservations. Design considerations for future remote sensing systems are given.

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