In ground- and tower-based instrumentation for direct sensing, few, if any, new concepts have appeared, but steady improvements in technique and reliability have been reported [Dyer et al., 1967; Goddard, 1970; Hicks, 1969; Kaimal, l9687semi; Kaimal et al, 1968; Thurteil et al., 19707semi; Wesely et al., 1970], and comparisons have been made between different kinds of instruments [Businger et al., 19677; Miyake et al, 1970a], leading generally to increased knowledge and confidence in the characteristics of each. More rapid advances occurred in aircraft-based instrumentation. In particular the utilization of inertial navigation systems by Axford , by the Air Force Hicat program [Crooks et al., 1968] and by the National Center for Atmospheric Research-Desert Research Institute program [National Center for Atmospheric Research, 1970] is leading to the ability to measure the larger turbulence scales and mesoscales, where much of the important energy generation resides, in levels above the surface boundary layer, Sheih  has effectively utilized hot wire anemometry to measure the microscales of turbulence from an aircraft. Precision radar-tracked balloons of either the constant-level type [Angell et al., 1968], or with a roughened surface to improve stability [DeMandel and Scoggins, 1967[, have been used to reveal details of the mesoscale wind field.
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