Use of Synthetic Data to Test Flight Patterns for a Boundary Layer Field Experiment

Abstract

A virtual research aircraft was flown through a synthetic atmospheric boundary layer to help design a real
\nflight plan that would allow robust turbulence statistics to be obtained in a heterogeneous, evolving, convective
\nboundary layer. The synthetic boundary layer data consisted of a field of coherent, large-diameter, thermal
\nupdraft/downdraft structures, superimposed in random smaller-scale turbulence having a Gaussian distribution.
\nThese large and small eddy perturbations, with scales set from published empirical relationships, were superimposed
\non the expected mean profiles of wind and potential temperature. The goal was to determine whether
\nsufficiently robust line-averaged statistics could be gathered to study a new similarity theory for the radix layer,
\nthe bottom fifth of the convective boundary layer, where mean profiles are not uniform with height.
\nAfter testing a variety of flight patterns with the synthetic data, a vertical zigzag pattern of slant ascent/descent
\nlegs was selected as the best compromise, given typical aircraft flight and safety constraints. This flight pattern
\nwas then successfully flown with the University of Wyoming King Air aircraft in the real atmosphere during
\nBoundary Layer Experiment 1996 (BLX96) over Oklahoma and Kansas. Postexperiment comparison revealed
\nthat the synthetic data exhibited less scatter than the actual data, perhaps caused by a heterogeneous surface
\nand a nonstationary boundary layer. Based on this comparison, some practical recommendations are given for
\nfuture use of synthetic boundary layer data. Copyright 1999 American Meteorological Society (AMS). Permission
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