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  • Author or Editor: J. R. Pollard x
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J. F. Read and R. T. Pollard

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P. G. Challenor, J. F. Read, R. T. Pollard, and R. T. Tokmakian

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This paper describes a new method for combining altimetry data with hydrography in order to produce absolute surface geostrophic currents from altimetry. This method is then applied to data from the Drake Passage allowing surface currents to be monitored every 35 days during the second half of 1992. The resulting currents show several regions of strong currents with water flowing to the east and other places where the currents are either zero or flowing to the west After comparison with a model it is suggested that this structure is a result of the bathymetry.

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C. B. Emmanuel, B. R. Bean, L. G. McAllister, and J. R. Pollard

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Acoustic probing of the lower atmosphere (<150 m) reveals structures that appear similar to those of instability waves produced by wind shear at the stable interface of a temperature inversion. The acoustic sounder was located in the vicinity of a meteorological tower 152 m in height. Profiles of wind velocity and temperature were taken during the acoustic sounder operation. Regions of enhanced thermal stability and wind shear produce strong echoes which the acoustic sounder maps on a height vs time facsimile record. In this paper we limit our discussion of those echo returns that have the characteristic appearance of Helmholtz waves. Richardson numbers calculated from the tower measurements over the layer thickness as determined from the acoustic sounder returns appear to he of the order of ½, while sub-strata embedded within the layer thickness exist where the Richardson number drops near the theoretically predicted critical value of ¼. In addition, measurements of the wavelengths associated with the “breaking” phenomenon conform to the theoretically predicted range of values.

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